The 100 most-cited articles in ACS Applied Materials & Interfaces, 2021

The use of metal-organic frameworks (MOFs) in biomedical applications has greatly expanded over the past decade due to the precision tunability, high surface areas, and high loading capacities of MOFs. Specifically, MOFs are being explored for a wide variety of drug delivery applications. Initially, MOFs were used for delivery of small-molecule pharmaceuticals; however, more recent work has focused on macromolecular cargos, such as proteins and nucleic acids. Here, we review the historical application of MOFs for drug delivery, with a specific focus on the available options for designing MOFs for specific drug delivery applications. These options include choices of MOF structure, synthetic method, and drug loading. Further considerations include tuning, modifications, biocompatibility, cellular targeting, and uptake. Altogether, this Review aims to guide MOF design for novel biomedical applications.

Radiative cooling is a passive cooling technology that offers great promises to reduce space cooling cost, combat the urban island effect, and alleviate the global warming. To achieve passive daytime radiative cooling, current state-of-the-art solutions often utilize complicated multilayer structures or a reflective metal layer, limiting their applications in many fields. Attempts have been made to achieve passive daytime radiative cooling with single-layer paints, but they often require a thick coating or show partial daytime cooling. In this work, we experimentally demonstrate remarkable full-daytime subambient cooling performance with both BaSO4 nanoparticle films and BaSO4 nanocomposite paints. BaSO4 has a high electron band gap for low solar absorptance and phonon resonance at 9 μm for high sky window emissivity. With an appropriate particle size and a broad particle size distribution, the BaSO4 nanoparticle film reaches an ultrahigh solar reflectance of 97.6% and a high sky window emissivity of 0.96. During field tests, the BaSO4 film stays more than 4.5 °C below ambient…

Understanding of the triboelectric charge accumulation from the view of microcapacitor formation plays a critical role in boosting the output performance of the triboelectric nanogenerator (TENG). Here, an electrospun nanofiber-based TENG (EN-TENG) using a poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE)/MXene nanocomposite material with superior dielectric constant and high surface charge density is reported. The influence of dielectric properties on the output performance of the EN-TENG is investigated theoretically and experimentally. The fabricated EN-TENG exhibited a maximum power density of 4.02 W/m 2 at a matching external load resistance of 4 MΩ. The PVDF-TrFE/MXene nanocomposite improved the output performance of the EN-TENG fourfold. The EN-TENG successfully powered an electronic stopwatch and thermo-hygrometer by harvesting energy from human finger tapping. Moreover, it was utilized in smart home applications as a self-powered switch for controlling electrical home appliances, including fire alarms, fans, and smart doors. This work presents an effective and…

Air filtration materials (AFMs) have gradually become a research hotspot on account of the increasing attention paid to the global air quality problem. However, most AFMs cannot balance the contradiction between high filtration efficiency and low pressure drop. Electrospinning nanofibers have a large surface area to volume ratio, an adjustable porous structure, and a simple preparation process that make them an appropriate candidate for filtration materials. Therefore, electrospun nanofibers have attracted increased attention in air filtration applications. In this paper, first, the preparation methods of high-performance electrospun air filtration membranes (EAFMs) and the typical surface structures and filtration principles of electrospun fibers for air filtration are reviewed. Second, the research progress of EAFMs with multistructures, including nanoprotrusion, wrinkled, porous, branched, hollow, core-shell, ribbon, beaded, nets structure, and the application of these nanofibers in air filtration are summarized. Finally, challenges with the fabrication of EAFMs, limitations of…

Hydrogel-based wearable devices have attracted tremendous interest due to their potential applications in electronic skins, soft robotics, and sensors. However, it is still a challenge for hydrogel-based wearable devices to be integrated with high conductivity, a self-healing ability, remoldability, self-adhesiveness, good mechanical strength and high stretchability, good biocompatibility, and stimulus-responsiveness. Herein, multifunctional conductive composite hydrogels were fabricated by a simple one-pot method based on poly(vinyl alcohol) (PVA), sodium alginate (SA), and tannic acid (TA) using borax as a cross-linker. The composite hydrogel network was built by borate ester bonds and hydrogen bonds. The obtained hydrogel exhibited pH- and sugar-responsiveness, high stretchability (780% strain), and fast self-healing performance with healing efficiency (HE) as high as 93.56% without any external stimulus. Additionally, the hydrogel displayed considerable conductive behavior and stable changes of resistance with high sensitivity (gauge factor (GF) = 15.98 at a strain of 780%). The…

Conductive hydrogels have drawn significant attention in the field of stretchable/wearable sensors due to their intrinsic stretchability, tunable conductivity, biocompatibility, multistimuli sensitivity, and self-healing ability. Recent advancements in hydrogel- and organohydrogel-based sensors, including a novel sensing mechanism, outstanding performance, and broad application scenarios, suggest the great potential of hydrogels for stretchable electronics. However, a systematic summary of hydrogel- and organohydrogel-based sensors in terms of their working principles, unique properties, and promising applications is still lacking. In this spotlight, we present recent advances in hydrogel- and organohydrogel-based stretchable sensors with four main sections: improved stability of hydrogels, fabrication and characterization of organohydrogel, working principles, and performance of different types of sensors. We particularly highlight our recent work on ultrastretchable and high-performance strain, temperature, humidity, and gas sensors based on polyacrylamide/carrageenan double…

Notwithstanding its relatively recent discovery, graphene has gone through many evolution steps and inspired a multitude of applications in many fields, from electronics to life science. The recent advancements in graphene production and patterning, and the inclusion of two-dimensional (2D) graphenic materials in three-dimensional (3D) superstructures, further extended the number of potential applications. In this Review, we focus on laser-induced graphene (LIG), an intriguing 3D porous graphenic material produced by direct laser scribing of carbonaceous precursors, and on its applications in chemical sensors and biosensors. LIG can be shaped in different 3D forms with a high surface-to-volume ratio, which is a valuable characteristic for sensors that typically rely on phenomena occurring at surfaces and interfaces. Herein, an overview of LIG, including synthesis from various precursors, structure, and characteristic properties, is first provided. The discussion focuses especially on transport and surface properties, and on how these can be controlled by tuning the laser processing.…

Stimuli-responsive hydrogels possess unique advantages in drug delivery due to their variable performance and status based on the external environment. In the present study, a dual-responsive (pH and reactive oxygen species (ROS)) hydrogel was prepared to realize drug release properties under inflammatory stimulation. By grafting 3-carboxy-phenylboronic acid to the gelatin molecular backbone and cross-linking with poly(vinyl alcohol), we successfully synthesized the inflammation-responsive drug-loaded hydrogels after encapsulation with vancomycin-conjugated silver nanoclusters (VAN-AgNCs) and pH-sensitive micelles loaded with nimesulide (NIM). This novel design not only retained the dynamic functions of hydrogels, such as injectability, self-healing, and remodeling, but also realized sequential and on-demand drug delivery at diabetic-infected wound sites. In this work, we found that the hydrogel exhibited excellent biocompatibility and hemostasis properties owing to the enhanced cell-adhesive property of the gelatin component. The significant antibacterial and anti-inflammatory…

Flexible and wearable hydrogel strain sensors have attracted tremendous attention for applications in human motion and physiological signal monitoring. However, it is still a great challenge to develop a hydrogel strain sensor with certain mechanical properties and tensile deformation capabilities, which can be in conformal contact with the target organ and also have self-healing properties, self-adhesive capability, biocompatibility, antibacterial properties, high strain sensitivity, and stable electrical performance. In this paper, an ionic conductive hydrogel (named PBST) is rationally designed by proportionally mixing polyvinyl alcohol (PVA), borax, silk fibroin (SF), and tannic acid (TA). SF can not only be a reinforcement to introduce an energy dissipation mechanism into the dynamically cross-linked hydrogel network to stabilize the non-Newtonian behavior of PVA and borax but it can also act as a cross-linking agent to combine with TA to reduce the dissociation of TA on the hydrogel network, improving the mechanical properties and viscoelasticity of the hydrogel. The…

Subcellular organelles are the cornerstones of cells, and destroying them will cause cell dysfunction and even death. Therefore, realizing precise organelle targeting of photosensitizers (PSs) can help reduce PS dosage, minimize side effects, avoid drug resistance, and enhance therapeutic efficacy in photodynamic therapy (PDT). Organelle-targeted PSs provide a new paradigm for the construction of the next generation of PSs and may provide implementable strategies for future precision medicine. In this Review, the recent targeting strategies of different organelles and the corresponding design principles of molecular and nanostructured PSs are summarized and discussed. The current challenges and opportunities in organelle-targeted PDT are also presented.

A porous and microstructure piezoresistive material composed of polydimethylsiloxane (PDMS) and multiwalled carbon nanotubes (MWCNTs) was designed and prepared for a flexible and highly sensitive pressure sensor over a wide detection range. The microstructure was patterned on the surface of the partially cured PDMS/MWCNTs/NaCl mixture by imprinting a nonwoven fabric. After curing and dissolving the NaCl powders, the porous and surface microstructure PDMS/MWCNT film was obtained. Two PDMS/MWCNT films were stacked together and sandwiched between two copper foil electrodes, in which the two microstructure surfaces were in contact with the electrodes. Due to the synergistic effects of the combination of the porous structure and surface microstructure, the flexible sensor had highly sensitive response over a wide pressure range from 1 Pa to 100 kPa. Under the small pressure, the high sensitivity was achieved by the change in contact areas between the electrodes and the surface microstructures; at high pressure up to 100 kPa, the sensor retained its high sensitivity because of the porous…

Though the widely available, low-cost, and disposable papers have been explored in flexible paper-based pressure sensors, it is still difficult for them to simultaneously achieve ultrahigh sensitivity, low limit and broad range of detection, and high-pressure resolution. Herein, we demonstrate a novel flexible paper-based pressure sensing platform that features the MXene-coated tissue paper (MTP) sandwiched between a polyimide encapsulation layer and a printing paper with interdigital electrodes. After replacing the polyimide with weighing paper in the MTP pressure sensor, the silver interdigital electrodes can be recycled through incineration. The resulting pressure sensor with polyimide or paper encapsulation exhibits a high sensitivity of 509.5 or 344.0 kPa –1, a low limit (∼1 Pa) and a broad range (100 kPa) of detection, and outstanding stability over 10 000 loading/unloading cycles. With ultrahigh sensitivity over a wide pressure range, the flexible pressure sensor can monitor various physiological signals and human movements. Configuring the pressure sensors into an array…

High-performance flexible strain sensors are urgently needed with the rapid development of wearable intelligent electronics. Here, a bifiller of carbon nanotubes (CNTs) and graphene (GR) for filling flexible porous polydimethylsiloxane (CNT-GR/PDMS) nanocomposites is designed and prepared for strain-sensing applications. The typical microporous structure was successfully constructed using the Soxhlet extraction technique, and the connected CNTs and GR constructed a perfect three-dimensional conductive network in the porous skeleton. As a result, the stretchability and sensitivity of the CNT-GR/PDMS-based strain sensors were well regulated based on the porous structure and the typical synergistic conductive network. Based on the destruction effect of the brittle synergistic conductive network located in the outer and inner layers of the cell skeleton and the contact effect between adjacent cells in different strain ranges, the prepared CNTs-GR/PDMS-based strain sensor exhibited superior gauge factors of 182.5, 45.6, 70.2, and 186.5 in the 0-3, 3-57, 57-90, and 90-120% strain regions,…

As a flexible wearable device, hydrogel-based sensors have attracted widespread attention in soft electronics. However, the application of traditional hydrogels at extreme temperatures or for a long-term stability still remain a challenge because of the existence of water. Herein, we reported an antifreezing and antidrying organohydrogel with high transparency (over 85% transmittance), high stretchability (up to 1200%), and robust adhesiveness to various substrates, which consist of polyacrylic acid, gelatin, AlCl 3+, and tannic acid in a water/glycerin binary solvent as the dispersion medium. As the binary solvent easily forms strong hydrogen bonds with water molecules, organohydrogels exhibited excellent tolerance for drying and freezing. The organohydrogels maintained conductivity, adhesion, and stable sensitivity after a long-term storage or at subzero temperature (−14 °C). Moreover, the organohydrogel-based wearable sensors with a gauge factor of 2.5 (strain, 0–100%) could detect both large-scale movements and subtle motions. Therefore, the multifunctional…

High Resolution Image Download MS PowerPoint Slide Metal halide perovskites have attracted tremendous attention due to their excellent electronic properties. Recent advancements in device performance and stability of perovskite solar cells (PSCs) have been achieved with the application of self-assembled monolayers (SAMs), serving as stand-alone hole transport layers in the p-i-n architecture. Specifically, phosphonic acid SAMs, directly functionalizing indium–tin oxide (ITO), are presently adopted for highly efficient devices. Despite their successes, so far, little is known about the surface coverage of SAMs on ITO used in PSCs application, which can affect the device performance, as non-covered areas can result in shunting or low open-circuit voltage. In this study, we investigate the surface coverage of SAMs on ITO and observe that the SAM of MeO-2PACz ([2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid) inhomogeneously covers the ITO substrate. Instead, when adopting an intermediate layer of NiO between ITO and the SAM, the homogeneity, and hence the surface coverage of…

Repair of large bone defects represents a major challenge for orthopedic surgeons. The newly formed microvessels inside grafts play a crucial role in successful bone tissue engineering. Previously, an active role for mesenchymal stem cell (MSC)-derived exosomes in blood vessel development and progression was suggested in the repair of multiple tissues. However, the reports on the application of MSC-derived exosomes in the repair of large bone defects are sparse. In this study, we encapsulated umbilical MSC-derived exosomes ( uMSC EXOs) in hyaluronic acid hydrogel (HA-Gel) and combined them with customized nanohydroxyapatite/poly-ε-caprolactone (nHP) scaffolds to repair cranial defects in rats. Imaging and histological evaluation indicated that the uMSC EXOs/Gel/nHP composites markedly enhanced bone regeneration in vivo, and the uMSC EXOs might play a key role in this process. Moreover, the in vitro results demonstrated that uMSC EXOs promoted the proliferation, migration, and angiogenic differentiation of endothelial progenitor cells (EPCs) but did not significantly affect the…

Recently, trivalent chromium ion doped phosphors have exhibited significant application potential in broadband near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs). However, developing an NIR phosphor with both broad emission bandwidth and excellent luminescence thermal stability is still a great challenge. Here, we demonstrate an NIR phosphor, ScF 3:Cr 3+, which can fulfill both conditions simultaneously. The prepared phosphors show broadband emission in the range of 700 to 1100 nm, with a full width at half-maximum (FWHM) of 140 nm peaking at 853 nm. These phosphors also demonstrate an excellent luminescence thermal stability (the emission intensity of ScF 3:Cr 3+ keeps 85.5% at 150 °C compared with the value at room temperature). An NIR pc-LED based on blue LED chips was fabricated and tested. The results show that the NIR pc-LED can yield strong broadband NIR emission. This work not only provides a promising phosphor for the application of NIR pc-LEDs but also has important guiding significance for effect of synthesis conditions on the luminescence properties…

Herein, the synergistic effects of hollow nanoarchitecture and high specific surface area of hollow activated carbons (HACs) are reported with the superior supercapacitor (SC) and capacitive deionization (CDI) performance. The center of zeolite imidazolate framework-8 (ZIF-8) is selectively etched to create a hollow cavity as a macropore, and the resulting hollow ZIF-8 (HZIF-8) is carbonized to obtain hollow carbon (HC). The distribution of nanopores is, subsequently, optimized by KOH activation to create more nanopores and significantly increase specific surface area. Indeed, as-prepared hollow activated carbons (HACs) show significant improvement not only in the maximum specific capacitance and desalination capacity but also capacitance retention and mean desalination rates in SC and CDI, respectively. As a result, it is confirmed that well-designed nanoarchitecture and porosity are required to allow efficient diffusion and maximum electrosorption of electrolyte ions.

Ice formation on the surface of outdoor equipment brings significant inconvenience to human life and production. Superhydrophobic materials with the micro-nanostructure are considered to be effective anti-icing materials. However, repeated icing and deicing processes will destroy the structure and lose anti-icing properties. Herein, low-cost, durable, high-efficiency photothermal superhydrophobic materials were prepared by electrochemical deposition and silanization treatment methods. Combined with the black-body property of carbon materials and the micro-nano hierarchical structure, the as-prepared material has excellent photothermal and superhydrophobic properties. The surface temperature can rise to 90 °C, and the freezing droplets can melt in 100 s under 100 mW/cm 2 of sunlight illumination. The superhydrophobic property endows the material with excellent anti-icing performance, and the icing delay time is as long as 3600 s. The melted water droplet can quickly roll off due to the low adhesion of the superhydrophobic surface, which avoids the refreezing of the melted droplet and…

Flexible sensors have attracted great research interest due to their applications in artificial intelligence, wearable electronics, and personal health management. However, due to the inherent brittleness of common hydrogels, preparing a hydrogel-based sensor integrated with excellent flexibility, self-recovery, and antifatigue properties still remains a challenge to date. In this study, a type of physically and chemically dual-cross-linked conductive hydrogels based on 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofiber (TOCN)-carrying carbon nanotubes (CNTs) and polyacrylamide (PAAM) matrix via a facial one-pot free-radical polymerization is developed for multifunctional wearable sensing application. Inside the hierarchical gel network, TOCNs not only serve as the nanoreinforcement with a toughening effect but also efficiently assist the homogeneous distribution of CNTs in the hydrogel matrix. The optimized TOCN-CNT/PAAM hydrogel integrates high compressive (∼2.55 MPa at 60% strain) and tensile (∼0.15 MPa) strength, excellent intrinsic self-recovery property…

The need for a high efficiency deep blue organic emitter with narrow emission line width has never been so great. This is driven by the need to simplify the complex OLED stack for displays to enable larger substrate sizes to be used and greatly increase production yields. Here, the merits of using the hyperfluorescence scheme based around new multiresonance boron nitrogen molecules typified by DABNA type emitters are discussed and key requirements for suitable sensitizer hosts described, especially the photophysical requirements for optimal performance.

Bimetallic metal–organic frameworks (MOFs) containing two different inorganic metal nodes exhibited enhanced properties in CO 2 adsorption and catalytic conversion compared with the corresponding monometallic MOFs. In this work, the novel bimetallic Zn/Mg-MOF-74 with different ratios of Zn/Mg was synthesized successfully by a facile one-pot method. Powder X-ray diffraction, Fourier transform infrared, X-ray photoelectron spectroscopy, scanning electron microscopy/transmission electron microscopy, N 2 /CO 2 adsorption/desorption, and CO 2 /NH 3 -temperature-programmed desorption techniques thoroughly characterized the structure, morphology, and physicochemical properties of Zn/Mg-MOF-74. Besides the excellent CO 2 adsorption capacity (128.3 cm 3 /g at 273 K and 1 bar), Zn 0.75 Mg 0.25 -MOF-74 also showed efficient catalytic activity for the cycloaddition reaction of CO 2 and epoxides to cyclic carbonates with outstanding yield and selectivity all over 99% under solvent-free and mild conditions (60 °C, 0.8 MPa), outperforming the mechanical combination of Zn-MOF-74 and Mg-MOF-74 with…

Hydrogen is a fuel with a potentially zero-carbon footprint viewed as a viable alternative to fossil fuels. It can be produced in a large scale via electrochemical water splitting using electricity derived from renewable sources, but this would require highly active, inexpensive, and stable hydrogen evolution reaction (HER) catalysts to replace the Pt benchmark. Transition-metal phosphides (TMPs) are potential Pt replacements owing to their generally high activity as well as versatility as HER catalysts for different pH media. This review summarizes the recent progress in the development of TMP HER electrocatalysts, focusing on the strategies that have been recently explored to tune the activity in acidic, neutral, and basic media. These strategies are the doping of TMPs with metal and nonmetal elements, fabrication of multimetallic phosphide phases, and construction of multicomponent heterostructures comprising TMPs and another component such as a different TMP or a metal oxide/hydroxide. The synthetic methods utilized to design the catalysts are also presented. Finally, the…

Herein, a new type of injectable carboxymethyl chitosan (CMCh) hydrogel wound dressing with self-healing properties is constructed. First, CMCh samples are homogeneously synthesized in alkali/urea aqueous solutions. Subsequently, trivalent metal ions of Fe 3+ and Al 3+ are introduced to form coordination bonds with CMCh, leading to an ultrafast gelation process. A series of hydrogels can be obtained by altering the concentration of CMCh and the relative content of metal ions. Owing to the dynamic and reversible characteristics of the coordination bonds, the hydrogel exhibits self-healing, self-adaption, and thermoresponsive ability. Moreover, due to the interaction between the amino groups on CMCh and SO 4 2–, the hydrogel undergoes phase separation and can be painlessly detached from the skin with little residue. Taking advantage of all these characteristics, the hydrogel is used as a wound dressing and can significantly accelerate skin tissue regeneration and wound closure. This hydrogel has great potential in the application of tissue engineering.

Zn-ion energy storage devices employing hydrogel electrolytes are considered as promising candidates for flexible and wearable electronics applications. This is because of their safe nature, low cost, and good mechanical characteristics. However, conventional hydrogel electrolytes face limitation at subzero temperatures. Herein, we report an antifreezing, safe, and nontoxic gel electrolyte based on the poly(vinyl alcohol) (PVA)/Zn/ethylene glycol system. The optimal gel electrolyte membrane exhibits a high ionic conductivity (15.03 mS cm –1 at room temperature) and promising antifreezing performance (9.05 mS cm –1 at −20 °C and 3.53 mS cm –1 at −40 °C). Moreover, the antifreezing gel electrolyte can suppress the growth of Zn dendrites to display a uniform Zn plating/stripping behavior. Also, a flexible antifreezing Zn-ion hybrid supercapacitor fabricated with the optimum antifreezing gel electrolyte membrane exhibits excellent electrochemical properties. The supercapacitor possesses a high specific capacity of 247.7 F g –1 at room temperature under a high working voltage of 2 V. It…

Hydrogel-based flexible strain sensors have shown great potential in body movement tracking, early disease diagnosis, noninvasive treatment, electronic skins, and soft robotics. The good self-healing, biocompatible, sensitive and stretchable properties are the focus of hydrogel-based flexible strain sensors. Dual network (DN) hydrogels are hopeful to fabricate self-healing hydrogels with the above properties. Here, multifunctional DN hydrogels are prepared via a combination of host–guest interaction of β-cyclodextrin and ferrocene with dynamic borate ester bonds of poly(vinyl alcohol) and borax. Carbon nanotubes are used to endow the DN hydrogels with good conductivity. The obtained DN composite hydrogels possess good biocompatibility, stretchability (436%), fracture strength (41.0 KPa), self-healing property (healing efficiency of 95%), and high tensile strain sensitivity (gauge factor of 5.9). The DN composite hydrogels are used as flexible strain sensors to detect different human motions. After cutting, the healed hydrogels also can monitor human motions and have good stability.…

UiO-66 is regarded as an epitome of metal-organic frameworks (MOFs) because of its stability. Defect engineering has been used as a toolbox to alter the performance of MOFs. UiO-66 is among the most widely explored MOFs because of its capability to bear a high number of defects without undergoing structural collapse. Several representative works in the field of MOF-based defect engineering are available based on UiO-66. In this review, more emphasis is given toward the construction of catalytic sites by engineering defects in UiO-66 as a representative including all the detailed synthesis procedures for inducing defects, and the characterization techniques used to analyze these defects in UiO-66 are discussed. Furthermore, a comprehensive review for the defects themselves and the support using defects in catalysis is provided to accentuate the importance of defect engineering.

A solar steam generation method has been widely investigated as a sustainable method to achieve seawater desalination and sewage treatment. However, oil pollutants are usually emitted in real seawater or wastewaters, which can cause serious fouling problems to disturb the solar evaporation performance. In this work, a mussel-inspired, low-cost, polydopamine-filled cellulose aerogel (PDA-CA) has been rationally designed and fabricated with both superhydrophilicity and underwater superoleophobicity. The resulting PDA-CA device could also achieve a high solar evaporation rate of 1.36 kg m –1 h –1 with an 86% solar energy utilize efficiency under 1 sun illumination. In addition, the PDA-CA not only exhibited promising antifouling capacity for long-term water evaporation but also engaged in the effective adsorption of organic dye contaminants. These promising features of PDA-CA may offer new opportunities for developing multifunctional photothermal devices for solar-driven water remediation.

The three-dimensional (3D) architecture of electrode materials with excellent stability and electrochemical activity is extremely desirable for high-performance supercapacitors. In this study, we develop a facile method for fabricating 3D self-supporting Ti 3 C 2 with MoS 2 and Cu 2 O nanocrystal composites for supercapacitor applications. MoS 2 was incorporated in Ti 3 C 2 using a hydrothermal method, and Cu 2 O was embedded in two-dimensional nanosheets by in situ chemical reduction. The resulting composite electrode showed a synergistic effect between the components. Ti 3 C 2 served as a conductive additive to connect MoS 2 nanosheets and facilitate charge transfer. MoS 2 acted as an active spacer to increase the interlayer space of Ti 3 C 2 and protect Ti 3 C 2 from oxidation. Cu 2 O effectively prevented the collapse of the lamellar structure of Ti 3 C 2 –MoS 2 . Consequently, the optimized composite exhibited an excellent specific capacitance of 1459 F g –1 at a current density of 1 A g –1 . Further, by assembling an all-solid-state flexible supercapacitor with activated…

Although reactive oxygen species (ROS) are essential for cellular processes, excessive ROS could be a major cause of various inflammatory diseases because of the oxidation of proteins, DNA, and membrane lipids. It has recently been suggested that the amount of ROS could thus be regulated to treat such physiological disorders. A ROS-scavenging hydrogel is a promising candidate for therapeutic applications because of its high biocompatibility, 3D matrix, and ability to be modified. Approaches to conferring antioxidant properties to normal hydrogels include embedding ROS-scavenging catalytic nanoparticles, modifying hydrogel polymer chains with ROS-adsorbing organic moieties, and incorporating ROS-labile linkers in polymer backbones. Such therapeutic hydrogels can be used for wound healing, cardiovascular diseases, bone repair, ocular diseases, and neurodegenerative disorders. ROS-scavenging hydrogels could eliminate oxidative stress, accelerate the regeneration process, and show synergetic effects with other drugs or therapeutic molecules. In this review, the mechanisms by which ROS…

The synergistic effect of surface oxygen vacancy with induced lattice strains on visible light-driven photocatalytic H 2 evolution over black TiO 2 was investigated. Experimental measurements and theoretical calculations on the lattice parameters of black TiO 2 show that surface oxygen vacancies induce internal lattice strain during two-step aluminothermic reduction, which regulates the band structure and optimizes the photoinduced charge behavior of black TiO 2 . The hydrogen evolution rate of black TiO 2 with strain modification shows a 12-fold increase to 1.882 mmol/g· h (equal to 4.705 μmol/cm 2 ·h) under visible light illumination. The metastable state caused by the surface oxygen vacancies leads to the formation of a high-energy surface, which enhances visible light absorption and improves the photoinduced charge separation efficiency. Furthermore, the internal lattice strain provides the driving force and channel for the directional movement of photoinduced electrons from the bulk to the high-energy surface for photocatalytic H 2 evolution. This strategy provides a new method…

Lignin converted to carbon quantum dots (CQDs) attracts tremendous attention for large-scale production of carbon nanomaterials and value-added disposal of biomass wastes (such as the black liquor from pulping industry and the residue from hydrolysis of biomass). The green synthesis of lignin-derived CQDs is reported via a facile two-step method with the adjustment of acid additives containing N or S. The resulting series of CQDs exhibit bright fluorescence in gradient colors from blue to yellowish green, among which the N, S co-doped CQDs with the addition of 2,4-diaminobenzene sulfonic acid show an optimal fluorescence quantum yield (QY) of 30.5%. The red-shift photoluminescence emission behaviors of these CQDs can be attributed to the increased graphitization degree and reduced optical energy band gaps (2.47 → 2.17 eV) with regard to the incorporation of various heteroatoms. The improved fluorescence QYs are consistent with the variation trend of the increased N/C content in the CQDs. The yellowish green-emissive CQDs with bright fluorescence, strong water solubility, and…

Developing hard carbon with a high initial Coulombic efficiency (ICE) and very good cycling stability is of great importance for practical sodium-ion batteries (SIBs). Defects and oxygen-containing groups grown along either the carbon edges or the layers, however, are inevitable in hard carbon and can cause a tremendous density of irreversible Na + sites, decreasing the efficiency and therefore causing failure of the battery. Thus, eliminating these unexpected defect structures is significant for enhancing the battery performance. Herein, we develop a strategy of applying a soft-carbon coating onto free-standing hard-carbon electrodes, which greatly hinders the formation of defects and oxygen-containing groups on hard carbon. The electrochemical results show that the soft-carbon-coated, free-standing hard-carbon electrodes can achieve an ultrahigh ICE of 94.1% and long cycling performance (99% capacity retention after 100 cycles at a current density of 20 mA g –1 ), demonstrating their great potential in practical sodium storage systems. The sodium storage mechanism was also…

The COVID-19 pandemic has clearly shown the importance of developments in fabrication of advanced protective equipment. This study investigates the potential of using multifunctional electrospun poly(methyl methacrylate) (PMMA) nanofibers decorated with ZnO nanorods and Ag nanoparticles (PMMA/ZnO-Ag NFs) in protective mats. Herein, the PMMA/ZnO-Ag NFs with an average diameter of 450 nm were simply prepared on a nonwoven fabric by directly electrospinning from solutions containing PMMA, ZnO nanorods, and Ag nanoparticles. The novel material showed high performance with four functionalities (i) antibacterial agent for killing of Gram-negative and Gram-positive bacteria, (ii) antiviral agent for inhibition of corona and influenza viruses, (iii) photocatalyst for degradation of organic pollutants, enabling a self-cleaning protective mat, and (iv) reusable surface-enhanced Raman scattering substrate for quantitative analysis of trace pollutants on the nanofiber. This multi-functional material has high potential for use in protective clothing applications by providing passive and active…

The ability to synthesize laser-induced graphene (LIG) on cellulosic materials such as paper opens the door to a wide range of potential applications, from consumer electronics to biomonitoring. In this work, strain and bending sensors fabricated by irradiation of regular filter paper with a CO 2 laser are presented. A systematic study of the influence of the different process parameters on the conversion of cellulose fibers into LIG is undertaken, by analyzing the resulting morphology, structure, conductivity, and surface chemistry. The obtained material is characterized by porous electrically conductive weblike structures with sheet resistances reaching as low as 32 Ω sq –1 . The functionality of both strain (gauge factor of ≈42) and bending sensors is demonstrated for different sensing configurations, emphasizing the versatility and potential of this material for low-cost, sustainable, and environmentally friendly mechanical sensing.

Two-dimensional vanadium carbide (V 2 C) and titanium carbide (Ti 3 C 2 ) MXenes were first synthesized by exfoliating V 2 AlC or Ti 3 AlC 2 and then introduced jointly into magnesium hydride (MgH 2 ) to tailor the hydrogen desorption/absorption performances of MgH 2 . The as-prepared MgH 2 –V 2 C–Ti 3 C 2 composites show much better hydrogen storage performances than pure MgH 2 . MgH 2 with addition of 10 wt % of 2V 2 C/Ti 3 C 2 initiates hydrogen desorption at around 180 °C; 5.1 wt % of hydrogen was desorbed within 60 min at 225 °C, while 5.8 wt % was desorbed within 2 min at 300 °C. Under 6 MPa H 2, the dehydrided MgH 2 –2V 2 C/Ti 3 C 2 can start to recover hydrogen at room temperature, and 5.1 wt % of H 2 is obtained within 20 s at a constant temperature of 40 °C. The reversible capacity (6.3 wt %) does not decline for up to 10 cycles, which shows excellent cycling stability. The addition of 2V 2 C/Ti 3 C 2 can remarkably lower the activation energy for the hydrogen desorption reaction of MgH 2 by 37% and slightly reduce the hydrogen desorption reaction enthalpy by 2 kJ mol –1 H…

MXene sheets, as new 2D nanomaterials, have been used in many advanced applications due to their superior thin-layered architecture, as well as their capability to be employed as novel nanocontainers for advanced applications. In this research, intercalated Ti 3 C 2 MXene sheets were synthesized through an etching method, and then they were modified with 3-aminopropyltriethoxysilane (APTES). Cerium cations (Ce 3+ ) as an eco-friendly corrosion inhibitor were encapsulated within Ti 3 C 2 MXene sheets to fabricate novel self-healing epoxy nanocomposite coatings. The corrosion protection performance (CPP) of Ce 3+ -doped Ti 3 C 2 MXene nanosheets (Ti 3 C 2 MXene-Ce 3+ ) in a 3.5 wt % sodium chloride (NaCl) solution was studied on bare mild steel substrates using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. The self-healing CPP of epoxy coatings loaded with 1 wt % undoped and doped Ti 3 C 2 MXene was evaluated using EIS, salt spray, and field emission scanning electron microscopy (FE-SEM) techniques. The introduction of Ti 3 C 2 MXene-Ce 3+…

This Spotlight on Applications highlights the significant impact of microwave-assisted methods for synthesis and modification of carbon materials with enhanced properties for electrodes in energy storage applications (supercapacitors and batteries). For the past few years, microwave irradiation has been increasingly used for the synthesis of carbon materials with different morphologies using various precursors. Microwave processing exhibits numerous advantages, such as short processing times, high yield, expanded reaction conditions, high reproducibility, and high purity of products. On this frontier research area, we have discussed microwave-assisted synthesis, defect creation, simultaneous reduction and exfoliation, and heteroatom doping in carbon materials. By careful manipulation of microwave irradiation parameters, the method becomes a powerful and efficient tool to generate different morphologies in carbon-based materials. Other important outcomes are the flexible control over the degree of reduction and exfoliation of graphene derivatives, the generation of defects in…

Aqueous zinc-ion batteries (ZIBs) are considered as a promising energy storage system due to their low cost and high safety merits. However, they suffer from the challenge of uncontrollable dendrite growth due to a non-uniform zinc deposition, which increases internal resistance and causes battery failure. Herein, Ag coating fabricated by a facile surface chemistry route on zinc metal was developed to guide uniform zinc deposition. Ag-coated Zn shows improved electrolyte wettability, a small zinc deposition overpotential, and fast kinetics for zinc deposition/dissolution. Direct optical visualization and scanning electron microscopy images show uniform zinc deposition due to the introduction of Ag coating. As a result, the Ag-coated Zn anode can sustain up to 1450 h of repeated plating/stripping with a low overpotential in symmetric cells at a current density of 0.2 mA cm –2, while an improved performance is realized for full cells paired with a V 2 O 5 -based cathode. This work provides a facile and effective approach to improve the electrochemical performance of ZIBs.

Stretchable electronics that can elongate elastically as well as flex are crucial to a wide range of emerging technologies, such as wearable medical devices, electronic skin, and soft robotics. Critical to stretchable electronics is their ability to withstand large mechanical strain without failure while retaining their electrical conduction properties, a feat significantly beyond traditional metals and silicon-based semiconductors. Herein, we present a review of the recent advances in stretchable conductive polymer nanocomposites with exceptional stretchability and electrical properties, which have the potential to transform a wide range of applications, including wearable sensors for biophysical signals, stretchable conductors and electrodes, and deformable energy-harvesting and -storage devices. Critical to achieving these stretching properties are the judicious selection and hybridization of nanomaterials, novel microstructure designs, and facile fabrication processes, which are the focus of this Review. To highlight the potentials of conductive nanocomposites, a summary of some…

Understanding the oxidation reaction of aqueous Ti 3 C 2 T x MXene suspensions is very important for fostering fundamental academic studies as well as widespread industrial applications. Herein, we investigated the mechanism and kinetics of the oxidation reaction of aqueous Ti 3 C 2 T x suspensions at various pH and temperature conditions. Through comprehensive analysis, the mechanism of the chemical oxidative degradation of aqueous Ti 3 C 2 T x colloids was established. Chemical oxidation produces solid products such as TiO 2 and amorphous carbon as well as various gaseous species including CH 4, CO, CO 2, and HF. Additionally, our comprehensive kinetic study proposes that aqueous Ti 3 C 2 T x dispersions are degraded via an acid-catalyzed oxidation reaction, where, under acidic conditions, the protonation of the hydroxyl terminal groups on the Ti 3 C 2 T x flakes induces electron localization on titanium atoms and accelerates their oxidation reaction. In contrast, under basic conditions, the electrostatically alkali-metalized hydroxyl intermediates forming a bulky solvent cage…

In the past decade, there has been an increasing number of computational screening works to facilitate finding optimal materials for a variety of different applications. Unfortunately, most of these screening studies are limited to their initial set of materials and result in a brute-force type of screening approach. In this work, we present a systematic strategy that can find metal–organic frameworks (MOFs) with the desired properties from an extremely diverse and large set of over 100 trillion possible MOFs using machine learning and evolutionary algorithm. It is demonstrated that our algorithm can discover 964 MOFs with methane working capacity over 200 cm 3 cm –3 and 96 MOFs with methane working capacity over the current world record of 208 cm 3 cm –3 . We believe that this methodology can take advantage of the modular nature of MOFs and can readily be extended to other important applications as well.

Hollow nanostructures have attracted significant research interest in drug delivery systems due to their high capacities for drug loading and unique physicochemical properties, showing great potential in specific biomedical applications. Herein, hollow porphyrinic metal–organic framework (H-PMOF) nanoparticles with a mesoporous spherical shell have been fabricated via a facile self-sacrificial ZIF-8 nanoparticle template strategy. The H-PMOF nanoplatform not only demonstrates a greatly enhanced photodynamic therapy efficacy compared with nonhollow porphyrinic MOF nanoparticles but also can be used as a superior drug carrier to co-load doxorubicin (DOX) and indocyanine green (ICG) with an ultrahigh drug-loading capacity of 635%. Furthermore, cancer cell membrane camouflage of the (DOX and ICG)@H-PMOF composite nanoparticles affords a biomimetic nanoplatform, that is, (DOX and ICG)@H-PMOF@mem (DIHPm for short), with an outstanding homologous tumor-targeting and immune-escaping ability. Interestingly, DIHPm shows both pH-controlled and near-infrared laser-triggered DOX release. Both in…

Prussian blue analogs (PBAs) featuring large interstitial voids and rigid structures are broadly recognized as promising cathode materials for sodium-ion batteries. Nevertheless, the conventionally prepared PBAs inevitably suffer from inferior crystallinity and lattice defects, leading to low specific capacity, poor rate capability, and unsatisfied long-term stability. As the Na + migration within PBAs is directly dependent on the periodic lattice arrangement, it is of essential significance to improve the crystallinity of PBAs and hence ensure long-range lattice periodicity. Herein, a chemical inhibition strategy is developed to prepare a highly crystallized Prussian blue (Na 2 Fe 4 [Fe(CN) 6 ] 3 ), which displays an outstanding rate performance (78 mAh g –1 at 100 C) and long life-span properties (62% capacity retention after 2000 cycles) in sodium storage. Experimental results and kinetic analyses demonstrate the efficient electron transfer and smooth ion diffusion within the bulk phase of highly crystallized Prussian blue. Moreover, in situ X-ray diffraction and in situ Raman…

Multifunctional intelligent fireproof cotton fabrics are urgently demanded in the era of the Internet of Things. Herein, a novel high fire safety cotton fabric (denoted as MXene/CCS@CF) with temperature sensing, fire-warning, piezoresistivity, and Joule heating performance was developed by coating MXene nanosheet and carboxymethyl chitosan (CCS) via an eco-friendly layer-by-layer assembly method. Benefiting from the thermoelectric characteristic and high conductivity of MXene nanosheet, MXene/CCS@CF exhibited accurate wide-range temperature sensing performance. When being burned, it could repeatedly trigger the fire-warning system in less than 10 s. More importantly, MXene/CCS@CF showed outstanding flame retardancy because of the synergistic carbonization between MXene and CCS. The limiting oxygen index of MXene/CCS@CF was as high as 45.5%, and the char length was only 33 mm after the vertical burning test. Meanwhile, its peak heat release rate reduced more than 66%. Besides, the obtained fabric could detect a variety of human motions. Moreover, the controllable Joule heating…

With the modern development of power electrification, polymer nanocomposite dielectrics (or nanodielectrics) have attracted significant research attention. The idea is to combine the high dielectric constant of inorganic nanofillers and the high breakdown strength/low loss of a polymer matrix for higher energy density polymer film capacitors. Although impressively high energy density has been achieved at the laboratory scale, there is still a large gap from the eventual goal of polymer nanodielectric capacitors. In this review, we focus on essential material issues for two types of polymer nanodielectrics, polymer/conductive nanoparticle and polymer/ceramic nanoparticle composites. Various material design parameters, including dielectric constant, dielectric loss, breakdown strength, high temperature rating, and discharged energy density will be discussed from both fundamental science and high-voltage capacitor application points of view. The objective is to identify advantages and disadvantages of the polymer nanodielectric approach against other approaches utilizing neat…

Flexible pressure sensors have aroused tremendous attention, owing to their broad applications in healthcare, robotics, and prosthetics. So far, it remains a critical challenge to develop low-cost and controllable microstructures for flexible pressure sensors. Herein, a high-sensitivity and low-cost flexible piezoresistive sensor was developed by combining a controllable graphene-nanowalls (GNWs) wrinkle and a polydimethylsiloxane (PDMS) elastomer. For the GNWs–PDMS bilayer, the vertically grown GNWs film can effectively improve the interface strength and form delamination-free conformal wrinkles. More importantly, a controllable microstructure can be easily tuned through the thermal wrinkling method. The wrinkled graphene-nanowalls (WG) piezoresistive sensor has a high sensitivity ( S = 59.0 kPa –1 for the 0–2 kPa region and S = 4.8 kPa –1 for the 2–20 kPa region), a fast response speed (<6.9 ms), and a low limit of detection (LOD) of 2 mg (∼0.2 Pa). The finite element method was used to analyze the working mechanism of the sensor, which revealed that the periods of the wrinkles…

MXene, a new state-of-the-art two-dimensional (2D) nanomaterial, has attracted considerable interest from both industry and academia because of its excellent electrical, mechanical, and chemical properties. However, MXene-based device engineering has rarely been reported. In this study, we explored Ti 3 C 2 MXene for digital and analog computing applications by engineering the top electrode. For this purpose, Ti 3 C 2 MXene was synthesized by a simple chemical process, and its structural, compositional, and morphological properties were studied using various analytical tools. Finally, we explored its potential application in bipolar resistive switching (RS) and synaptic learning devices. In particular, the effect of the top electrode (Ag, Pt, and Al) on the RS properties of the Ti 3 C 2 MXene-based memory devices was thoroughly investigated. Compared with the Ag and Pt top electrode-based devices, the Al/Ti 3 C 2 /Pt device exhibited better RS and operated more reliably, as determined by the evaluation of the charge-magnetic property and memory endurance and retention. Thus, we…

Constructing a step-scheme (S-scheme) heterojunction represents a promising route to overcome the drawbacks of single-component and traditional heterostructured photocatalysts by simultaneously broadening the optical response range and optimizing the redox ability of the photocatalytic system, the efficiency of which greatly lies in the separation behaviors of photogenerated charge carriers with strong redox capabilities. Herein, we demonstrate interfacial facet engineering as an effective strategy to manipulate the charge transfer and separation for substantially improving the photocatalytic activities of S-scheme heterojunctions. The facet engineering is performed with the growth of ZnIn 2 S 4 on (010) and (001) facet-dominated BiOBr nanosheets to fabricate ZIS/BOB-(010) and ZIS/BOB-(001) S-scheme heterojunctions, respectively. It is disclosed that a larger Fermi level difference between BiOBr-(001) and ZnIn 2 S 4 enables the formation of a stronger built-in electric field with more serious band bending in the space charge region around the interface. As a result, the directional…

Passive daytime radiative cooling (PDRC) involves cooling down an object by simultaneously reflecting sunlight and thermally radiating heat to the cold outer space through the Earth’s atmospheric window. However, for practical applications, current PDRC materials are facing unprecedented challenges such as complicated and expensive fabrication approaches and performance degradation arising from surface contamination. Herein, we develop scalable cellulose-fiber-based composites with excellent self-cleaning and self-cooling capabilities, through air-spraying ethanolic poly(tetrafluoroethylene) (PTFE) microparticle suspensions embedded partially within the microsized pores of the cellulose fiber to form a dual-layered structure with PTFE particles atop the paper. The formed superhydrophobic PTFE coating not only protects the cellulose-fiber-based paper from water wetting and dust contamination for real-life applications but also reinforces its solar reflectivity by sunlight backscattering. It results in a subambient cooling performance of 5 °C under a solar irradiance of 834 W/m 2 and…

A stretchable conductor is one of the key components in soft electronics that allows the seamless integration of electronic devices and sensors on elastic substrates. Its unique advantages of mechanical flexibility and stretchability have enabled a variety of wearable bioelectronic devices that can conformably adapt to curved skin surfaces for long-term health monitoring applications. Here, we report a poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)-based stretchable polymer blend that can be patterned using an inkjet printing process while exhibiting low sheet resistance and accommodating large mechanical deformations. We have systematically studied the effect of various types of polar solvent additives that can help induce phase separation of PEDOT and PSS grains and change the conformation of a PEDOT chain, thereby improving the electrical property of the film by facilitating charge hopping along the percolating PEDOT network. The optimal ink formulation is achieved by adding 5 wt % ethylene glycol into a pristine PEDOT:PSS aqueous solution, which results in a…

Environmentally friendly lead-free dielectric ceramics have attracted wide attention because of their outstanding power density, rapid charge/dischargerate, and superior stability. Nevertheless, as a hot material in dielectric ceramic capacitors, the energy storage performance of Na 0.5 Bi 0.5 TiO 3 -based ceramics has been not satisfactory because of their higher remnant polarization value and low dielectric breakdown strength, which is a problem that must be urgently overcome. In this work, the (1 – x ) (0.6Na 0.5 Bi 0.5 TiO 3 – 0.4Sr 0.7 Bi 0.2 TiO 3 ) – x Ba(Mg 1/3 Ta 2/3 )O 3 (BNST- x BMT) systems were designed based on a dual optimization strategy of domain and bandgap to solve the above problems. As a result, a record-breaking ultrahigh energy density and excellent efficiency ( W rec = 8.58 J/cm 3, η = 93.5%) were obtained simultaneously under 565 kV/cm for the BNST-0.08BMT ceramic. The introduction of Sr 0.7 Bi 0.2 TiO 3 induces the formation of nanodomains in BNT-based ceramics, leading to slim P - E curves, and the further modification of Mg/Ta reduces the grain sizes and…

Early diagnosis of SARS-CoV-2 infection is critical for facilitating proper containment procedures, and a rapid, sensitive antigen assay is a critical step in curbing the pandemic. In this work, we report the use of a high-purity semiconducting (sc) single-walled carbon nanotube (SWCNT)-based field-effect transistor (FET) decorated with specific binding chemistry to assess the presence of SARS-CoV-2 antigens in clinical nasopharyngeal samples. Our SWCNT FET sensors, with functionalization of the anti-SARS-CoV-2 spike protein antibody (SAb) and anti-nucleocapsid protein antibody, detected the S antigen (SAg) and N antigen (NAg), reaching a limit of detection of 0.55 fg/mL for SAg and 0.016 fg/mL for NAg in calibration samples. SAb-functionalized FET sensors also exhibited good sensing performance in discriminating positive and negative clinical samples, indicating a proof of principle for use as a rapid COVID-19 antigen diagnostic tool with high analytical sensitivity and specificity at low cost.

As the leading anode material for sodium-ion batteries (SIBs), hard carbon (HC) still faces the puzzle of low initial Coulombic efficiency (ICE) in achieving commercialization. From the perspective of precursors, the low ICE has been attributed to the large specific surface area and porosity produced by the rapid decomposition of polymers during the carbonization. Therefore, increasing the cross-linking degree of precursors will be an effective shortcut to improve the ICE. Herein, a facile pre-oxidation tactic was successfully employed to tailor the cross-linking degree of phenolic resin precursors to precisely control the specific surface area of the obtained HC. As the pre-oxidation time is increased, the optimal HC with the lowest specific surface area shows an ICE elevated by 22.2% (from 62.5 to 84.7%) compared to the original pre-oxidation HC and delivers a high reversible capacity of 334.3 mAh g –1 at 20 mA g –1 . Besides, the pre-oxidation also introduces abundant carbonyl groups, which increase the disorder degree of HC and supply abundant adsorption sites of Na +, thus…

Conductive hydrogels can be used in wearable electronics integrated with skin, but the bulk structure of existing hydrogel-based temperature sensors limits the wearing comfort, response/recovery speeds, and sensitivity. Here, stretchable and transparent temperature sensors based on a novel thin-film sandwich structure (TFSS) are designed, which display unprecedented thermal sensitivity (24.54%/°C), fast response time (0.19 s) and recovery time (0.08 s), a broad detection range (from -28 to 95.3 °C), high resolution (0.8 °C), and high stability. The thin hydrogel layer (12.15 μm) is encapsulated by two thin elastomer layers, which prevent the water evaporation and enhance the heat transfer, leading to the boosted stability and accelerated response/recovery speeds. The nondrying and antifreezing capabilities are further promoted by the hydratable lithium bromide (LiBr) incorporated in the hydrogel, enabling it to avoid dehydration in an extremely arid environment and freeze below subzero temperatures (freezing point below -120 °C). A comparative study reveals that the thermal…

Three-dimensional (3D) printing technologies have unparalleled advantages in constructing piezoelectric devices with three-dimensional structures, which are conducive to improving the efficiency of energy harvesting. Among them, fused deposition modeling (FDM) is the most widely used thanks to its low cost and wide range of molding materials. However, as the best piezoelectric polymer, a high electroactive β-phase poly(vinylidene fluoride) (PVDF) piezoelectric device cannot be directly obtained by FDM printing because the β-crystal is unstable at the molten state. Herein, we develop for the first time ionic liquid (IL)-assisted FDM for direct printing of β-PVDF piezoelectric devices. An IL can induce and maintain β crystals during melt extrusion and FDM printing, ensuring that the β-crystal in the printed PVDF device is as high as 98.3%, which is the highest in 3D-printed PVDF as far as we know. Furthermore, the shearing force provided by the FDM facilitates the directional arrangement of the dipoles, resulting in the printed PVDF device having self-polarization characteristics…

Four-dimensional (4D) printed magnetoactive soft material (MASM) with a three-dimensional (3D) patterned magnetization profile possesses programmable shape transformation and controllable locomotion ability, showing promising applications in actuators and soft robotics. However, typical 4D printing strategies for MASM always introduced a printing magnetic field to orient the magneto-sensitive particles in polymers. Such strategies not only increase the cooperative control complexity of a 3D printer but may also induce local agglomeration of magneto-sensitive particles, which disturbs the magnetization of the already-printed structure. Herein, we proposed a novel 4D printing strategy that coupled the traditional 3D injection printing with the origami-based magnetization technique for easy fabrication of MASM objects with a 3D patterned magnetization profile. The 3D injection printing that can rapidly create complex 3D structures and the origami-based magnetization technique that can generate the spatial magnetization profile are combined for fabrication of 3D MASM objects to yield…

High Resolution Image Download MS PowerPoint Slide The photophysics of multiple resonance thermally activated delayed fluorescence molecule ν-DABNA is described. We show coupling of a 285 cm –1 stretching/scissoring vibrational mode of peripheral phenyl rings to the S 1 state, which dictates the ultimate emission full-width at half maximum. However, a separate high amplitude mode, 945 cm –1 of the N -biphenyl units, mediates the reverse intersystem crossing (rISC) mechanism. Concentration-dependent studies in solution and solid state reveal a second emission band that increases nonlinearly with concentration, independent of the environment assigned to excimer emission. Even at concentrations well below those used in devices, the excimer contribution affects performance. Using different solvents and solid hosts, rISC rates between 3–6 × 10 5 s –1 are calculated, which show negligible dependence on environmental polarity or host packing. At 20 K over the first 10 ns, we observe a broad Gaussian excimer emission band with energy on-set above the S 1 exciton band. An optical…

BiFeO 3 -BaTiO 3 is a promising high-temperature piezoelectric ceramic that possesses both good electromechanical properties and a Curie temperature ( T C ). Here, the piezoelectric charge constants ( d 33 ) and strain coefficients ( d * 33 ) of (1 – x )BiFeO 3 - x BaTiO 3 (BF- x BT; 0.20 ≤ x ≤ 0.50) lead-free piezoelectrics were investigated at room temperature. The results showed a maximum d 33 of 225 pC/N in the BF-0.30BT ceramic and a maximum d * 33 of 405 pm/V in the BF-0.35BT ceramic, with T C s of 503 and 415 °C, respectively. To better understand the performance enhancement mechanisms, a phase diagram was established using the results of XRD, piezoresponse force microscopy, TEM, and electrical property measurements. The superb d 33 of the BF-0.30BT ceramic arose because of its location in the optimum point in the morphotropic phase boundary, low oxygen vacancy ( V O ·· ) concentration, and domain heterogeneity. The superior d * 33 of the BF-0.35BT ceramic was attributed to a weak relaxor behavior between coexisting macrodomains and polar nanoregions. The presented strategy…

Bioinspired hydrogels have promising prospects in applications such as wearable devices, human health monitoring equipment, and soft robots due to their multifunctional sensing properties resembling natural skin. However, the preparation of intelligent hydrogels that provide feedback on multiple electronic signals simultaneously, such as human skin receptors, when stimulated by external contact pressure remains a substantial challenge. In this study, we designed a bioinspired hydrogel with multiple conductive capabilities by incorporating carbon nanotubes into a chelate of calcium ions with polyacrylic acid and sodium alginate. The bioinspired hydrogel consolidates self-healing ability, stretchability, 3D printability, and multiple conductivities. It can be fabricated as an integrated strain sensor with simultaneous piezoresistive and piezocapacitive performances, exhibiting sensitive (gauge factor of 6.29 in resistance mode and 1.25 kPa –1 in capacitance mode) responses to subtle pressure changes in the human body, such as finger flexion, knee flexion, and respiration. Furthermore,…

The transition metal-based layered double hydroxides (LDHs) have been extensively studied as promising functional nanomaterials owing to their excellent electrochemical activity and tunable chemical composition. In this work, using acetate anions (Ac – ) as intercalating elements, the NiCo-LDH nanosheets arraying on Ni foam with different amounts of Ac – anion intercalation or volume of hydrothermal solution were prepared by a simple hydrothermal method. The optimized amount of Ac – anions expanded the interlayer space of LDH nanosheets from 0.8 to 0.94 nm. An ultrahigh specific capacity of 1200 C g –1 at 1 A g –1 (690 C g –1 without Ac – anions), an outstanding rate capability of 72.5% at 30 A g –1, and a cycle stability of 79.90% after 4500 cycles were mainly attributed to the higher interlayer spacing of Ac – anion intercalation. The enlarged interlayer spacing was beneficial for stabilizing the α-phase of LDHs and accelerating the electron transport and electrolyte penetration in the electrochemical reaction. This work sheds light on the mechanisms of the interlayer spacing…

The activity of electrocatalysts can be improved by modifying their electronic structures and surface morphologies. In electrochemical reactions with gas evolution, the performance of an electrocatalyst is also affected by how easily gas bubbles depart from an electrocatalyst surface. However, it is difficult to quantitatively estimate the improvement in the performance that can be achieved by promoting the departure of gas bubbles from the electrocatalyst surface. This study investigated the effect of surface hydrophilicity on the hydrogen evolution reaction (HER). The water contact angles of the nickel phosphorous (NiP) films were controlled from 40.3 to 77.2° with imperceptible differences in their intrinsic electronic structures and surface areas. Electrochemical analyses and in situ visualization of the gas evolution on the NiP films indicated that an increase in the hydrophilicity of the electrocatalysts reduced the size of gas bubbles formed on the NiP films and shortened the duration of the bubbles’ stay on the NiP surface. A faster gas departure enabled continuous…

Searching for highly efficient and eco-friendly photocatalysts for water splitting is essential for renewable conversion and storage of inexhaustible solar energy but remains a great challenge. Herein, based on the new emerging two-dimensional (2D) material of MoSi 2 N 4, we report novel Janus MoSiGeN 4 and WSiGeN 4 structures with excellent stabilities and great potentials in photocatalytic applications through first-principles calculations. Comprehensive studies show that MoSi 2 N 4, MoSiGeN 4, and WSiGeN 4 exhibit semiconductor characteristics with an indirect gap, appropriate band gaps, and strong optical absorbance in the visible spectrum. Excitingly, by constructing Janus structures, an intrinsic electric field is realized that enhances the spatial separation and anisotropic migration of photoexcited electrons and holes. Further, this strategy can also alter the band alignment to provide an adequate photoexcited carrier driving force for water redox reactions. Moreover, the surface N vacancy can effectively lower the energy demand of both hydrogen evolution reaction (HER) and…

Although hydrophilic and electrically conductive transition-metal carbon/nitride (MXenes) nanosheets hold great promise for electrically conductive and electromagnetic interference (EMI) shielding applications, the weak interaction among MXene nanosheets makes them difficult to form compressible three-dimensional architectures with high conductivity. Herein, inspired by the plant “ Parthenocissus tricuspidata ”, an efficient approach is demonstrated to fabricate conductive and lightweight Ti 3 C 2 T x MXene/acidified carbon nanotube anisotropic aerogels (MCAs) with superelasticity and high thermal insulation. The MXene nanosheets construct the anisotropic and porous skeleton, while the acidified carbon nanotubes reinforce the pore walls of MXene nanosheets, making the MCAs superelastic and compressible. The superelastic MCA with only 5 wt % of the acidified carbon nanotubes is structurally stable during cyclic compressions at both high and ultralow temperatures. Its high conductivity (447.2 S m –1 ) and ultralow density (9.1 mg cm –3 ) endow its paraffin composite with a high EMI…

In the face of increasingly severe electromagnetic (EM) wave pollution, the research of EM wave absorbing materials is an effective solution. To reduce the density of traditional absorbing materials, in this work, FeCo/CoFe 2 O 4 /carbon nanofiber composites were successfully prepared by electrospinning for the EM wave attenuation application. Benefiting from the loss ability of interface polarization, dipole polarization, and magnetic loss, the composites obtained a bandwidth of 5.0 GHz at a 1.95 mm thickness and an absorption peak of −52.3 dB. More importantly, the radar cross section (RCS) reduction of composite coatings calculated by ANSYS Electronics Desktop 2018 (HFSS) can reach 34.5 dBm 2, and the RCS value is almost less than −10 dBm 2 when the incident angle is greater than 20°, demonstrating great scattering ability of the material coating to EM waves. This work, combined with the exploration of the mechanism and the simulation analysis of the absorbing coating, will be of significance for the development of absorbing materials.

A memristor is a two-terminal device with nonvolatile resistive switching (RS) behaviors. Recently, memristors have been highly desirable for both fundamental research and technological applications because of their great potential in the development of high-density memory technology and neuromorphic computing. Benefiting from the unique two-dimensional (2D) layered structure and outstanding properties, 2D materials have proven to be good candidates for use in gate-tunable, highly reliable, heterojunction-compatible, and low-power memristive devices. More intriguing, stable and reliable nonvolatile RS behaviors can be achieved in multi- and even monolayer 2D materials, which seems unlikely to be achieved in traditional oxides with thicknesses less than a few nanometers because of the leakage currents. Moreover, such two-terminal devices show a series of synaptic functionalities, suggesting applications in simulating a biological synapse in the neural network. In this review article, we summarize the recent progress in memristors based on inorganic and organic 2D materials, from the…

Ultrahigh-resolution displays for augmented reality (AR) and virtual reality (VR) applications require a novel architecture and process. Atomic-layer deposition (ALD) enables the facile fabrication of indium–gallium zinc oxide (IGZO) thin-film transistors (TFTs) on a substrate with a nonplanar surface due to its excellent step coverage and accurate thickness control. Here, we report all-ALD-derived TFTs using IGZO and HfO 2 as the channel layer and gate insulator, respectively. A bilayer IGZO channel structure consisting of a 10 nm base layer (In 0.52 Ga 0.29 Zn 0.19 O) with good stability and a 3 nm boost layer (In 0.82 Ga 0.08 Zn 0.10 O) with extremely high mobility was designed based on a cation combinatorial study of the ALD-derived IGZO system. Reducing the thickness of the HfO 2 dielectric film by the ALD process offers high areal capacitance in field-effect transistors, which allows low-voltage drivability and enhanced carrier transport. The intrinsic inferior stability of the HfO 2 gate insulator was effectively mitigated by the insertion of an ALD-derived 4 nm Al 2 O 3…

Hydrogels that are mechanically tough and capable of strong underwater adhesion can lead to a paradigm shift in the design of adhesives for a variety of biomedical applications. We hereby innovatively develop a facile but efficient strategy to prepare hydrogel adhesives with strong and instant underwater adhesion, on-demand detachment, high toughness, notch-insensitivity, self-healability, low swelling index, and tailorable surface topography. Specifically, a polymerization lyophilization conjugation fabrication method was proposed to introduce tannic acid (TA) into the covalent network consisting of polyethylene glycol diacrylate (PEGDA) of substantially high molecular weight. The presence of TA facilitated wet adhesion to various substrates by forming collectively strong noncovalent bonds and offering hydrophobicity to allow water repellence and also provided a reversible cross-link within the binary network to improve the mechanical performance of the gels. The long-chain PEGDA enhanced the efficacy and stability of TA conjugation and contributed to gel mechanics and adhesion by…

The electrochemical reduction of CO 2 (ECO 2 R) is a promising method for reducing CO 2 emissions and producing carbon-neutral fuels if long-term durability of electrodes can be achieved by identifying and addressing electrode degradation mechanisms. This work investigates the degradation of gas diffusion electrodes (GDEs) in a flowing, alkaline CO 2 electrolyzer via the formation of carbonate deposits on the GDE surface. These carbonate deposits were found to impede electrode performance after only 6 h of operation at current densities ranging from −50 to −200 mA cm –2 . The rate of carbonate deposit formation on the GDE surface was determined to increase with increasing electrolyte molarity and became more prevalent in K + -containing as opposed to Cs + -containing electrolytes. Electrolyte composition and concentration also had significant effects on the morphology, distribution, and surface coverage of the carbonate deposits. For example, carbonates formed in K + -containing electrolytes formed concentrated deposit regions of varying morphology on the GDE surface, while those…

One two-dimensional Fe-based metal–organic framework (FeSC1) and one one-dimensional coordination polymer (FeSC2) have been solvothermally prepared through the reaction among FeSO 4 ·7H 2 O, the tripodal ligand 4,4′,4″- s -triazine-2,4,6-triyl-tribenzoate (H 3 TATB), and flexible secondary building blocks p/m-bis((1H-imidazole-1-yl)methyl)benzene (bib). Given that their abundant interlayer spaces and different coordination modes, two compounds have been employed as battery-type electrodes to understand how void space and different coordination modes affect their performances in three-electrode electrochemical systems. Both materials exhibit outstanding but different electrochemical performances (including distinct capacities and charge-transfer abilities) under three-electrode configurations, where the charge storage for each electrode material is mainly dominated by the diffusion-controlled section ( i ∝ v 0.5 ) through power-law equations. Additionally, the partial phase transformations to more stable FeOOH are also detected in the long-term cycling loops. After coupling with the…

Doping engineering emerges as a contemporary technique to investigate the catalytic performance of MoS 2 . Cation and anion co-doping appears as an advanced route toward electrocatalytic hydrogen evolution reaction (HER). V and N as dopants in MoS 2 (VNMS) build up a strain inside the crystal structure and narrow down the optical band gaps manifesting the shifting of the absorbance band toward lower energy and improved catalytic performance. FE-SEM, HR-TEM, and XRD analysis confirmed that V and N doping decreases agglomeration possibility, particle size, developed strain, and crystal defects during crystal growth. Frequency shift and peak broadening in Raman spectra confirmed the doping induced strain generation in MoS 2 leading to the modification of acidic and alkaline HER (51 and 110 mV @ 10 mAcm –2, respectively) performance. The improved donor density in VNMS was confirmed by the Mott–Schottky analysis. Enhanced electrical conductivity and optimized electronic structures facilities H* adsorption/desorption in the catalytically active (001) plane of cation and anion co-doped MoS…

Hydrogel patches with high toughness, stretchability, and adhesive properties are critical to healthcare applications including wound dressings and wearable devices. Gelatin methacryloyl (GelMA) provides a highly biocompatible and accessible hydrogel platform. However, low tissue adhesion and poor mechanical properties of cross-linked GelMA patches ( i.e ., brittleness and low stretchability) have been major obstacles to their application for sealing and repair of wounds. Here, we show that adding dopamine (DA) moieties in larger quantities than those of conjugated counterparts to the GelMA prepolymer solution followed by alkaline DA oxidation could result in robust mechanical and adhesive properties in GelMA-based hydrogels. In this way, cross-linked patches with ∼140% stretchability and ∼19 000 J/m 3 toughness, which correspond to ∼5.7 and ∼3.3× improvement, respectively, compared to that of GelMA controls, were obtained. The DA oxidization in the prepolymer solution was found to play an important role in activating adhesive properties of cross-linked GelMA patches (∼4.0 and ∼6.9×…

High-air humidity, especially condensation into droplets under the influence of temperature, can pose a serious threat to air purification filters. This report introduces the use of methyltrimethoxysilane (MTMS) for the silanization hydrophobic modification of cellulose nanofibers (CNFs) and obtains an air filter with super-hydrophobicity (CA = 152.4°) and high-efficiency filtration of particulate matter (PM) through the freeze-drying technology. The antihumidity performance of CNFs filters that undergo hydrophobic modification in high-humidity air is improved. Especially in the case of high-humidity air forming condensed water droplets, the increase in the rate of filtration resistance of the hydrophobically modified CNFs filter is much lower than that of the unmodified filter. In addition, the water-vapor-transmission rate of the hydrophobically modified filter is improved. More importantly, adding MTMS can regulate the porous structure of CNFs filters and improve the filtration performance. The specific surface area and the porosity of the filter are 26.54 m 2 /g and 99.21%,…

Lightweight electromagnetic (EM) wave absorbers made of ceramics have sparked tremendous interest for applications in EM wave interference protection at high temperatures. However, EM wave absorption by pure ceramics still faces huge challenges due to the lack of efficient EM wave attenuation modes. Inspired by the energy dissipation mechanism during fracture of lobster shells with a soft and stiff multilayered structure, we fabricate a high-performance EM wave absorption ceramic aerogel composed of an alternating multilayered wave transparent Si 3 N 4 (N) layer and wave absorption SiC (C) layer by a simple restack method. The obtained N/C aerogel shows ultralow density (∼8 mg/cm 3 ), broad effective absorption bandwidth (8.4 GHz), strong reflection loss (−45 dB) at room temperature, and excellent EM wave absorption performance at high temperatures up to 1000 °C. The attenuation of EM wave mainly results from a “reflection–absorption–zigzag reflection” process caused by the alternating multilayered structure. The superior absorption performance, especially at high temperatures,…

As an innovative additive manufacturing process, 4D printing can be utilized to generate predesigned, self-assembly structures which can actuate time-dependent, and dynamic shape-changes. Compared to other manufacturing techniques used for tissue engineering purposes, 4D printing has the advantage of being able to fabricate reprogrammable dynamic tissue constructs that can promote uniform cellular growth and distribution. For this study, a digital light processing (DLP)-based printing technique was developed to fabricate 4D near-infrared (NIR) light-sensitive cardiac constructs with highly aligned microstructure and adjustable curvature. As the curvature of the heart is varied across its surface, the 4D cardiac constructs can change their shape on-demand to mimic and recreate the curved topology of myocardial tissue for seamless integration. To mimic the aligned structure of the human myocardium and to achieve the 4D shape change, a NIR light-sensitive 4D ink material, consisting of a shape memory polymer and graphene, was created to fabricate microgroove arrays with different…

The ZnIn 2 S 4 /BiVO 4 heterostructures were elegantly designed through assembling ZnIn 2 S 4 nanosheets onto the surface of BiVO 4 decahedrons. This composite photocatalyst exhibits efficient photocatalytic conversion of CO 2 into CO with a detectable amount of CH 4 in the presence of water vapor. An electron spin-resonance spectroscopy (ESR) technique and density function theory (DFT) calculation affirm the direct Z-scheme structure in ZnIn 2 S 4 /BiVO 4 . The larger surface photovoltage (SPV) change and the longer liquid photoluminescence (PL) lifetime of the heterostructure, compared to the individual ZnIn 2 S 4 and BiVO 4 components, demonstrate that the Z-scheme structure can effectively promote the recombination of the photogenerated holes in the valence band (VB) of the ZnIn 2 S 4 nanosheet with the electrons in the conduction band (CB) of the decahedral BiVO 4 and lead to the abundant electrons surviving in the CB of ZnIn 2 S 4 and holes in the VB of BiVO 4, thus enhancing photocatalytic CO 2 reduction performance. This study may make a potential contribution to the…

Equipping wearable electronics with special functions will endow them with more additional values and more comprehensive practical performance. Here, we report an ultraviolet (UV)-protective, self-cleaning, antibacterial, and self-powered all-nanofiber-based triboelectric nanogenerator (TENG) for mechanical energy harvesting and self-powered sensing, which is fabricated with Ag nanowires (NWs)/TPU nanofibers and the TiO 2 @PAN networks through a facile electrospinning method. Due to the added TiO 2 nanoparticles (NPs), the TENG presents excellent UV-protective performance, including the ultraviolet protection factor (UPF) of ∼204, the transmittance of UVA ( T UVA ) of ∼0.0574%, and the transmittance of UVB ( T UVB ) ∼0.107%. Furthermore, under solar lighting for 25 min, most surface contamination can be degraded, and the decreased power output would be recovered. Owing to the coupled effects of TiO 2 NPs and Ag NWs, the TENG shows excellent antibacterial activity against Staphylococcus aureus . Due to the micro-to-nano hierarchical porous structure, the all-nanofiber-based TENG can…

Considering the flexibility, adjustable pore structure, and abundant active sites of metal-organic frameworks (MOFs), rational design and fine control of the MOF-based hetero-nanocrystals is a highly important and challenging subject. In this work, self-assembly of a 3D hollow BiOBr@Bi-MOF microsphere was fabricated through precisely controlled dissociation kinetics of the self-sacrificial template (BiOBr) for the first time, where the residual quantity of BiOBr and the formation of Bi-MOF were carefully regulated by changing the reaction time and the capability of coordination. Meanwhile, the hollow microstructure was formed in BiOBr@Bi-MOF through the Oswald ripening mechanism to separate photogenerated electron-hole pairs and increase the adsorption capacity of Bi-MOF for dyes, which significantly enhanced the photocatalytic degradation efficiency of RhB from 56.4% for BiOBr to 99.4% for the optimal BiOBr@Bi-MOF microsphere. This research broadens the selectivity of semiconductor/MOF hetero-nanocrystals with reasonable design and flexible synthesis.

The electrochemical reduction of oxygen to water and the evolution of oxygen from water are two important electrode reactions extensively studied for the development of electrochemical energy conversion and storage technologies based on oxygen electrocatalysis. The development of an inexpensive, highly active, and durable nonprecious-metal-based oxygen electrocatalyst is indispensable for emerging energy technologies, including anion exchange membrane fuel cells, metal-air batteries (MABs), water electrolyzers, etc. The activity of an oxygen electrocatalyst largely decides the overall energy storage performance of these devices. Although the catalytic activities of Pt and Ru/Ir-based catalysts toward an oxygen reduction reaction (ORR) and an oxygen evolution reaction (OER) are known, the high cost and lack of durability limit their extensive use for practical applications. This review article highlights the oxygen electrocatalytic activity of the emerging non-Pt and non-Ru/Ir oxygen electrocatalysts including transition-metal-based random alloys, intermetallics, metal-coordinated…

Flexible pressure sensors have attracted increasing attention because they can mimic human skin to sense external pressure; however, for mimicking human skin, the sensing of a pressure point is far from sufficient. To realize fully biomimetic skins, it is crucial for flexible sensors to have high resolution and high sensitivity. We conducted simulations and experiments to determine the relationship between the sensor sensitivity and physical parameters, such as the effective relative permittivity and air ratio of the dielectric layer. According to the results, a micropillar–poly(vinylidene fluoride) (PVDF) dielectric layer was designed to achieve high sensitivity (0.43 kPa –1 ) in the low-pressure regime (<1 kPa). An 8 × 8 pixel sensor matrix was prepared based on a micropillar–PVDF (MP) film and electrode array (MPEA) to detect the pressure distribution with high resolution (13 dpi). Each pixel could reflect the point of applied pressure through an obvious change in the relative capacitance; moreover, objects with various geometries could be mapped by the pixels of the flexible…

Broadband near-infrared (NIR) emitting materials are in great demand as next-generation smart NIR light sources. In this work, a Cr 3+ -substituted phosphor capable of efficiently converting visible to NIR light is developed through the solid solution, Ga 2– x In x O 3:Cr 3+ (0 ≤ x ≤ 0.5). The compounds were prepared using high-temperature solid-state synthesis, and the crystal and electronic structure, morphology, site preference, and photoluminescence properties are studied. The photoluminescence results demonstrate a high quantum yield (88%) and impressive absorption efficiency (50%) when x = 0.4. The NIR emission is tunable across a wide range (713–820 nm) depending on the value of x . Moreover, fabricating a prototype of a phosphor-converted NIR light-emitting diode (LED) device using 450 nm LED and the [(Ga 1.57 Cr 0.03 )In 0.4 ]O 3 phosphor showed an output power that reached 40.4 mW with a photoelectric conversion efficiency of 25% driven by a current of 60 mA, while the resulting device was able to identify damaged produce that was undetectable using visible light. These…

Daytime radiative cooling materials reflect solar light and dissipate heat directly to outer space without any energy consumption, and thus, have attracted much attention due to the potential applications in many fields. Recently, elaborately designed photonic crystal and metamaterials have been reported for daytime subambient radiative cooling. However, such materials and structures have the drawbacks of complex shapes, inflexibility, high cost, and limitation in scaling up. It is also extremely difficult to apply such materials to buildings, vehicles, and other objects having complex surfaces. Here, a scalable and flexible hybrid film for daytime subambient radiative cooling was fabricated by a facile electrospinning method. The hybrid film consists of poly(vinylidene fluoride)/alumina (PVDF/Al 2 O 3 ) fibers with diameters of 0.5–2.5 μm. Owing to the efficient scattering by fibers and Al 2 O 3 nanoparticles, the hybrid film exhibits an extremely high average solar reflectance of 0.97. A high average atmospheric window emittance of 0.95 is simultaneously achieved due to the…

Developing photopolymerizable polymeric materials offers many opportunities to process materials in a remote and controllable manner. However, most photopolymerizable technologies require the external introduction of photoabsorbing units, whereas designing intrinsically photopolymerizable polymers is still highly challenging. Here, we report that a natural small-molecule disulfide, thioctic acid, can be directly transformed into a poly(disulfides) network under the irradiation of visible light without any external additives. The resulting polymer network exhibits optical transparency, mechanical stretchability and toughness, ambient self-healing ability, and especially strong adhesive ability to different surfaces. The dynamic covalent backbones of the poly(disulfides) endow the depolymerization ability to recycle the material in a closed-loop manner. We foresee that this facile and robust photopolymerization system is of great promise toward low-cost and high-performance photocuring coatings and adhesives.

Multifunctionalization is an important development direction of electromagnetic interference (EMI)-shielding materials. However, it is still a huge challenge to effectively integrate multiple functions into materials. Herein, we reported a facile method to fabricate multifunctional EMI-shielding materials, which were assembled with multidimensional components consisting of a 3D melamine–formaldehyde (MF) foam skeleton, 0D ferroferric oxide (Fe 3 O 4 ) nanoparticles, and 1D silver nanowires (AgNWs) via coprecipitation and dip-coating processes. Due to the coaction of conductive AgNWs and magnetic Fe 3 O 4 nanoparticles, the resultant hybrid foam showed excellent absorption-dominant EMI-shielding performances with a high specific EMI-shielding effectiveness value of 12,704 dB cm 2 g –1 . Moreover, thanks to the multilayer porous micro-/nanostructure and the nonflammability of functional coatings, the hybrid foam shows excellent flame retardancy and heat insulation, making it attractive for the functions of infrared stealth and heat insulation. The corresponding mechanism is discussed…

Layered H 2 TiO 3 has been studied as an ionic sieve material for the selective concentration of lithium from solutions. The accepted mechanism of lithium adsorption on H 2 TiO 3 ion sieves is that it occurs via Li + –H + ion exchange with no chemical bond breakage. However, in this work, we demonstrate that lithium adsorption on H 2 TiO 3 occurs via O–H bond breakage and the formation of O–Li bonds, contrary to previously proposed mechanisms. Thermogravimetric analysis results show that the weight loss due to dehydroxylation decreases from 2.96 wt % to 0.8 wt % after lithium adsorption, indicating that surface hydroxyl groups break during lithium adsorption. Raman and Fourier transform infrared spectroscopy studies indicate that H 2 TiO 3 contains isolated OH groups and hydrogen-bonded OH groups. Among these two hydroxyl groups, isolated OH groups present in the HTi 2 layers are more actively involved in lithium adsorption than hydrogen-bonded OH groups. As a result, the actual adsorption capacity is limited by the number of isolated OH groups, whereas hydrogen-bonded OH groups…

Interaction of the conjugated structure in melanin contributed to photothermal conversion. Inspired by this, here, we first demonstrated that lignin nanoparticles (L-NPs) can carry out photothermal conversion, which was attributed to π–π stacking of lignin molecules. Lignin can be readily converted into L-NPs, using the self-assembly method at room temperature. L-NPs showed a stable photothermal effect (22%). The L-NPs were successfully used to power a thermoelectric generator and drive a solar steam generation device under standard 1 sun irradiation (100 mW/cm 2 ). Because thermoelectric generators and solar steam generation technologies have huge potential for energy generation and water purification, the as-prepared L-NPs are expected to provide an important contribution to sustainable energy and clean water production.

Metal organic frameworks (MOFs) have been widely researched and applied in many fields. However, the poor electrical conductivity of many traditional MOFs greatly limits their application in electrochemistry, especially in energy storage. Benefited from the full charge delocalization in the atomical plane, conductive MOFs (c-MOFs) exhibit good electrochemical performance. Besides, unlike graphene, c-MOFs are provided with 1D cylindrical channels, which can facilitate the ion transport and enable high ion conductivity. Transition-metal oxides (TMOs) are promising materials with good electrochemical energy storage performance due to their excellent oxidation–reduction activity. When composited with TMOs, the c-MOFs can significantly improve the capacitance and rate performance. In this work, for the first time, we designed serial MnO 2 @Ni-HHTP (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) nanoarrays with different lengths and explored how the lengths influence the electrochemical energy storage performance. By taking advantage of the high redox activity of MnO 2 and the excellent…

A flexible poly(vinylidene difluoride) (PVDF) composite film embedding LiNbO 3 ceramics decorated with silver nanoparticles (Ag NPs) has been synthesized using the solvent casting method. The polar β-phase, Ag NPs, and LiNbO 3 phases were confirmed in the composite film using various characterization methods. The composite film showed promising degradation of cationic and anionic dyes using piezocatalysis under ultrasonication. Moreover, this composite film also effectively degraded two model pharmaceutical pollutants named tetracycline and ciprofloxacin using piezocatalysis under ultrasonication. In addition to this, this composite film piezocatalytically removed more than 99.999% of Escherichia coli and 96.65% of Staphylococcus aureus bacteria within 180 min of sonication. The piezocatalytic performance of the PVDF composite film embedding Ag-loaded LiNbO 3 in all three applications was superior to that obtained in the case of the PVDF film embedding LiNbO 3 and the bare PVDF film. This demonstrates the pronounced effect of Ag NPs in the increase of piezocatalytic activity in the…

Efficient removal of uranium (U) from aqueous solutions is crucial for ecological safety. Functionalized magnetic nanoparticles provide a promising strategy for radionuclide recovery and separation. However, designing and synthesizing magnetic adsorbents with high sorption capacity and selectivity, accompanied by excellent stability and reusability, remain a challenge. In this work, novel amidoxime-functionalized flower-like magnetic Fe 3 O 4 @TiO 2 core–shell microspheres are designed and synthesized to efficiently remove U(VI) from aqueous solutions and actual seawater. The magnetic Fe 3 O 4 core facilitates easy separation by an external magnetic field, and flower-like TiO 2 nanosheets provide abundant specific surface areas and functionalization sites. The grafted amidoxime (AO) groups could function as a claw for catching uranium. The maximum adsorption capacity on U(VI) of the designed nanospheres reaches 313.6 mg·g –1 at pH 6.0, and the adsorption efficiency is maintained at 97% after 10 cycles. In addition, the excellent selectivity of the magnetic recyclable AO-functioning…

Alzheimer’s disease (AD) is a neurodegenerative disease associated with amyloid-β (Aβ) deposition, leading to neurotoxicity (oxidative stress and neuroinflammation) and gut microbiota imbalance. Resveratrol (Res) has neuroprotective properties, but its bioavailability in vivo is very low. Herein, we developed a small Res-selenium-peptide nanocomposite to enable the application of Res for eliminating Aβ aggregate-induced neurotoxicity and mitigating gut microbiota disorder in aluminum chloride (AlCl 3 ) and d -galactose( d -gal)-induced AD model mice. Res functional selenium nanoparticles (Res@SeNPs) (8 ± 0.34 nm) were prepared first, after which the surface of Res@SeNPs was decorated with a blood–brain barrier transport peptide (TGN peptide) to generate Res-selenium-peptide nanocomposites (TGN-Res@SeNPs) (14 ± 0.12 nm). Oral administration of TGN-Res@SeNPs improves cognitive disorder through (1) interacting with Aβ and decreasing Aβ aggregation, effectively inhibiting Aβ deposition in the hippocampus; (2) decreasing Aβ-induced reactive oxygen species (ROS) and increasing activity of…

Zinc–iodine (Zn/I 2 ) batteries are recognized as a kind of leading candidate for large-scale energy storage systems, owing to the high-capacity dissolution–deposition reactions on both electrodes. Nevertheless, the lifespan of Zn/I 2 batteries is severely limited by the uncontrolled shuttling of triiodide ions (I 3 – ) and unfavorable side reactions on Zn anodes. Herein, an alginate-based polyanionic hydrogel electrolyte is designed and synthesized by ion exchange and Zn 2+ -induced cross-linking. The immobile, negatively charged polyanionic chains on the hydrogel skeleton effectively block I 3 – from shuttling, while simultaneously transporting cations that are indispensable for battery chemistry. Moreover, this hydrogel can also enhance the cycling durability of Zn anodes by alleviating Zn’s dendritic growth and corrosion reactions, due to the homogenized Zn 2+ flux and reduced interfacial contact between free water and metallic Zn. Consequently, this alginate-based hydrogel electrolyte enables stable Zn plating/stripping for over 600 h at 2 mA cm –2 and 2 mAh cm –2…

Water electrolysis powered by renewable electricity produces green hydrogen and oxygen gas, which can be used for energy, fertilizer, and industrial applications and thus displace fossil fuels. Pure-water anion-exchange-membrane (AEM) electrolyzers in principle offer the advantages of commercialized proton-exchange-membrane systems (high current density, low cross over, output gas compression, etc.) while enabling the use of less-expensive steel components and nonprecious metal catalysts. AEM electrolyzer research and development, however, has been limited by the lack of broadly accessible materials that provide consistent cell performance, making it difficult to compare results across studies. Further, even when the same materials are used, different pretreatments and electrochemical analysis techniques can produce different results. Here, we report an AEM electrolyzer comprising commercially available catalysts, membrane, ionomer, and gas-diffusion layers operating near 1.9 V at 1 A cm –2 in pure water. After the initial break in, the performance degraded by 0.67 mV h –1 at 0.5 A…

Abstract The recent development of phase transfer ligand exchange methods for PbS quantum dots (QD) has enhanced the performance of quantum dots solar cells and greatly simplified the complexity of film deposition. However, the dispersions of PbS QDs (inks) used for film fabrication often suffer from colloidal instability, which hinders large-scale solar cell production. In addition, the wasteful spin-coating method is still the main technique for the deposition of QD layer in solar cells. Here, we report a strategy for scalable solar cell fabrication from highly stable PbS QD inks. By dispersing PbS QDs capped with CH3NH3PbI3 in 2,6-difluoropyridine (DFP), we obtained inks that are colloidally stable for more than 3 months. Furthermore, we demonstrated that DFP yields stable dispersions even of large diameter PbS QDs, which are of great practical relevance owing to the extended coverage of the near-infrared region. The optimization of blade-coating deposition of DFP-based inks enabled the fabrication of PbS QD solar cells with power conversion efficiencies of up to 8.7%. It is…

Photothermal desalination is a promising approach for seawater purification by harvesting solar energy. Titanium carbide (Ti 3 C 2 T x MXene) membranes have been regarded as potential materials for photothermal desalination by virtue of their excellent light-to-heat conversion. However, achieving a well-balanced synergy between high evaporation rate and good salt resistance remains a significant challenge due to their limited solar absorption and inferior stability. Herein, we report a self-assembled flexible porphyrin-Ti 3 C 2 T x MXene Janus membrane (Janus PMX membrane) for dual-functional enabled photothermal desalination. The self-assembly of porphyrin on MXene not only effectively creates a favorable hydrophobic surface but also simultaneously enables efficient solar utilization. The significant interactions and charge redistribution between MXene and porphyrin lead to a stable hydrophobic/hydrophilic Janus structure with synergistically enhanced photothermal conversion. As a result, the Janus PMX membrane demonstrates highly efficient water pumping, heat localization, vapor…

Flexible electronics greatly facilitate human life due to their convenience and comfortable utilization. Liquid metals are an ideal candidate for flexible devices; however, the high surface tension and poor surface wettability restrict their application on diverse substrates. Herein, a printable and recyclable ink composed of poly(vinyl alcohol) and a liquid metal (PVA-LM) was developed to resolve these problems. The materials were designed considering the compatibility between PVA and the liquid metal, and the composite theory was applied to determine the component proportion. The developed composites improved the surface wettability of the liquid metal on diverse substrates, and three-dimensional (3D) printing technology was chosen to maximize the use of this material. Moreover, the PVA-LM ink showed excellent conductivity of about 1.3 × 10 5 S/m after being turned on, which favored the designing of alarm systems and object locators. The flexible sensors produced with this ink have broad application, high sensitivity, and superstable signal generation even after 200 cycles. When…

The weak mechanical properties of hydrogels due to the inefficient dissipation of energy in the intrinsic structures limit their practical applications. Here, a double-network (DN) hydrogel has been developed by integrating an ionically cross-linked agar network, a covalently cross-linked acrylic acid (AAC) network, and the dynamic and reversible ionically cross-linked coordination between the AAC chains and Fe 3+ ions. The proposed model reveals the mechanisms of the improved mechanical performances in the DN agar/AAC–Fe 3+ hydrogel. The hydrogen-bond cross-linked double helices of agar and ionic-coordination interactions of AAC–Fe 3+ can be temporarily sacrificed during large deformation to readily dissipate the energy, whereas the reversible AAC–Fe 3+ interactions can be regenerated after stress relief, which greatly increases the material toughness. The developed DN hydrogel demonstrates a remarkable stretchability with a break strain up to 3174.3%, high strain sensitivity with the gauge factor being 0.83 under a strain of 1000%, and good 3D printability, making the material a…

Conductive stretchable hydrogels and ionogels consisting of ionic liquids can have interesting application as wearable strain and pressure sensors and bioelectrodes due to their soft nature and high conductivity. However, hydrogels have a severe stability problem because of water evaporation, whereas ionogels are not biocompatible or even toxic. Here, we demonstrate self-adhesive, stretchable, nonvolatile, and biocompatible eutectogels that can always form conformal contact to skin even during body movement along with their application as wearable strain and pressure sensors and biopotential electrodes for precise health monitoring. The eutectogels consist of a deep eutectic solvent that has high conductivity, waterborne polyurethane that is an elastomer, and tannic acid that is an adhesive. They can have an elongation at a break of 178%, ionic conductivity of 0.22 mS/cm, and adhesion force of 12.5 N/m to skin. They can be used as conformal strain sensors to accurately monitor joint movement and breath. They can be even used as pressure sensors with a piezoresistive sensitivity of…

Black phosphorus (BP), an emerging remarkable photocatalytic semiconductor, is arousing strong interests in this field of solar-driven CO 2 reduction, but its stability and activity are still facing huge challenges. Here, an ambient-stable and effective 2D/2D heterostructure of BP/bismuth tungstate (Bi 2 WO 6 ) with oxygen vacancy is innovatively designed for syngas production via photocatalytic CO 2 reduction. This work, not only resolves the stability problem of BP nanosheets by anchoring ultrasmall platinum (Pt) nanoparticles (∼2 nm) but also greatly improves the charge transfer efficiency by constructing S-scheme 2D/2D heterostructure with coupled oxygen defects. As a result, the generation rates of carbon monoxide (CO) and hydrogen (H 2 ) remarkably reach 20.5 and 16.8 μmol g –1 h –1, respectively, which are much higher than that of reported BP-based materials, and the accomplished CO/H 2 ratios (1:1–2:1) are exactly the most desirable syngas for industrial applications. Thus, this work constructs an efficient and ambient-stable BP-based photocatalyst for syngas production by…

Metal–organic frameworks (MOFs) are crystalline materials comprising metal centers and organic linkers that feature structural rigidity and functional flexibility. These attractive materials offer large surface areas, high porosity, and good chemical stability; they have shown promise in chemistry (H 2 separation and catalysis), magnetism, and optics. They have also shown potential for drug delivery following the demonstration in 2006 that chromium-based MOFs can be loaded with ibuprofen. Since then, iron-based MOFs (Fe-MOFs) have been shown to offer high drug loading and excellent biocompatibility. The present review focuses on the synthesis and surface modifications of Fe-MOFs as well as their applications in drug delivery and biomedicine.

The slow Zn 2+ intercalation/deintercalation kinetics in cathodes severely limits the electrochemical performance of aqueous zinc-ion batteries (ZIBs). Herein, we demonstrate a new kind of coordinately unsaturated manganese-based metal–organic framework (MOF) as an advanced cathode for ZIBs. Coordination unsaturation of Mn is performed with oxygen atoms of two adjacent −COO – . Its proper unsaturated coordination degree guarantees the high-efficiency Zn 2+ transport and electron exchange, thereby ensuring high intrinsic activity and fast electrochemical reaction kinetics during repeated charging/discharging processes. Consequently, this MOF-based electrode possesses a high capacity of 138 mAh g –1 at 100 mA g –1 and a long life span (93.5% capacity retention after 1000 cycles at 3000 mA g –1 ) due to the above advantages. Such distinct Zn 2+ ion storage performance surpasses those of most of the recently reported MOF cathodes. This concept of adjusting the coordination degree to tune the energy storage capability provides new avenues for exploring high-performance MOF cathodes in…