The 50 most-cited articles in Langmuir, 2019

Nanogels and microgels are soft, deformable, and penetrable objects with an internal gel-like structure that is swollen by the dispersing solvent. Their softness and the potential to respond to external stimuli like temperature, pressure, pH, ionic strength, and different analytes make them interesting as soft model systems in fundamental research as well as for a broad range of applications, in particular in the field of biological applications. Recent tremendous developments in their synthesis open access to systems with complex architectures and compositions allowing for tailoring microgels with specific properties. At the same time state-of-the-art theoretical and simulation approaches offer deeper understanding of the behavior and structure of nano- and microgels under external influences and confinement at interfaces or at high volume fractions. Developments in the experimental analysis of nano- and microgels have become particularly important for structural investigations covering a broad range of length scales relevant to the internal structure, the overall size and shape,…

The 100th anniversary of Langmuir's theory of adsorption is a significant landmark for the physical chemistry and chemical engineering communities. Despite its simplicity, the Langmuir adsorption model captures the key physics of molecular interactions at interfaces and laid the foundation for further progress in understanding interfacial phenomena, developing new adsorbent materials, and designing engineering processes. The Langmuir model has had an exceptional impact on diverse fields within the chemical sciences (ranging from chemical biology to materials science), an impact that became clearer with the development of modified adsorption theories and continues to be relevant today.

Electrochemical gas evolution reactions are of vital importance in numerous electrochemical processes including water splitting, chloralkaline process, and fuel cells. During gas evolution reactions, gas bubbles are vigorously and constantly forming and influencing these processes. In the past few decades, extensive studies have been performed to understand the evolution of gas bubbles, elucidate the mechanisms of how gas bubbles impact gas evolution reactions, and exploit new bubble-based strategies to improve the efficiency of gas evolution reactions. In this feature article, we summarize the classical theories as well as recent advancements in this field and provide an outlook on future research topics.

Flexible and highly sensitive humidity sensors are crucial for humidity detection. In this study, a flexible cellulose nanofiber/carbon nanotube (NFC/CNT) humidity sensor with high sensitivity performance was developed via fast vacuum filtration. CNTs were well dispersed in water by using 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-oxidized NFC as a dispersant. More importantly, NFC also acted as a humidity sensitive material, achieving superior performance of NFC/CNT humidity sensors. The obtained NFC/CNT humidity sensor with 5 wt % CNT loading exhibits outstanding sensitive performance, and its response value reaches a maximum of 69.9% (Δ I / I 0 ) at 95% relative humidity (RH). It also displays good bending resistance and long-term stability. In addition, the NFC/CNT humidity sensor was employed to monitor human breath. Therefore, we believe that the flexible, highly sensitive, and simply designed NFC/CNT humidity sensor is a promising candidate for various applications in the field of humidity measurement.

In the last couple of decades, ultrasound-driven microbubbles have proven excellent candidates for local drug delivery applications. Besides being useful drug carriers, microbubbles have demonstrated the ability to enhance cell and tissue permeability and, as a consequence, drug uptake herein. Notwithstanding the large amount of evidence for their therapeutic efficacy, open issues remain. Because of the vast number of ultrasound- and microbubble-related parameters that can be altered and the variability in different models, the translation from basic research to (pre)clinical studies has been hindered. This review aims at connecting the knowledge gained from fundamental microbubble studies to the therapeutic efficacy seen in in vitro and in vivo studies, with an emphasis on a better understanding of the response of a microbubble upon exposure to ultrasound and its interaction with cells and tissues. More specifically, we address the acoustic settings and microbubble-related parameters (i.e., bubble size and physicochemistry of the bubble shell) that play a key role in…

Functional surfaces with superhydrophobic and superoleophobic properties are of great interest in many applications. However, such surfaces are generally difficult to obtain. Although a few superamphiphobic surfaces have been developed recently, a challenge still remains in preparing such a surface with good durability which is a critical issue in practical application. In this study, we demonstrate a facile method for preparing durable superhydrophobic and highly oleophobic surfaces using two kinds of nanoparticles. Epoxy resin is used as the adhesive material to improve the wear resistance of the surfaces. ZnO nanoparticles and SiO 2 nanoparticles are used to create high surface roughness. The prepared surfaces exhibit excellent superhydrophobicity and high oleophobicity once the nanoparticles are treated with 1 H,1 H,2 H,2 H -perfluorodecyltriethoxydsilane (FAS-17). Water and ethylene glycol contact angles of the coatings can reach up to 172? 2? and 157? 2?, respectively. After undergoing strong adhesive tape peeling and mechanical abrasion, the coatings still maintain good…

MXene is a new type of two-dimensional (2D) material that finds wide applications; however, its adhesion and tribological properties have not yet been fully revealed. Here, the chemical structure of MXene was revealed by X-ray diffraction, and the adhesion and friction behaviors of MXene were studied with atomic force microscopy (AFM) Nanoman technology. It was found in AFM tests that MXene exhibited enhanced adhesion and friction at higher pressure but exhibited reduced adhesion and friction at elevated temperature, while the sliding speed and delay time of the AFM probe have negligible effects on the friction. X-ray photoelectron spectroscopy was used to reveal the change in the chemical structure of MXene at different temperatures. We found increased oxidation, and replacement of C by O atoms occurred on MXene at higher temperatures, which has a profound impact on the adhesion and friction between MXene and the probe tip. This discovery lays the foundation for understanding the adhesion mechanism and the dynamic adhesion behavior in friction of MXene, rendering MXene a much…

Peptide amphiphiles (PAs) are extremely attractive as molecular building blocks, especially in the bottom-up fabrication of supramolecular soft materials, and have potential in many important applications across various fields of science and technology. In recent years, we have designed and synthesized a large group of peptide amphiphiles. This library of PAs has the ability to self-assemble into a variety of aggregates such as fibers, nanosphere, vesicles, nanosheet, nanocups, nanorings, hydrogels, and so on. The mechanism behind the formation of such a wide range of structures is intriguing. Each system has its individual method of aggregation and results in assemblies with important applications in areas including chemistry, biology, and materials science. The aim of this feature article is to bring together our recent achievements with designer PAs with respect to their self-assembly processes and applications. Emphasis is placed on rational design, mechanistic aspects of the self-assembly processes, and the applications of these PAs. We hope that this article will provide a…

Nanoemulsion systems comprising n -heptane (oleic component), stabilized by the {gemini surfactant (14-6-14 GS) + polymer [partially hydrolyzed poly-acrylamide (PHPA)] + silica (SiO 2 ) nanoparticle} shell and dispersed in aqueous phase, were synthesized by ultrasonication (high-energy method). Influence of ultrasonication time on nanoemulsion kinetics was investigated to predict the saturation droplet diameter. Morphological analysis by transmission electron cryomicroscopy imaging showed that oleic phase appears as uniformly dispersed spherical droplets in 14-6-14 GS-stabilized nanoemulsion, which on PHPA addition changes into a network structure consisting of larger oil droplets. 14-6-14 + PHPA + SiO 2 nanoemulsion systems show more effective packing arrangement with irregular-shaped (nonspherical) droplets. Dynamic light scattering studies identified droplet size distribution profiles in the range 4.2–25.4 nm for the surfactant-stabilized nanoemulsion, 125.9–358.8 nm for the surfactant–polymer nanoemulsion, and 88.4–222.3 nm for the surfactant–polymer–nanoparticle-based…

Nanobubbles have electrically charged interfaces; hence, the diffused double layer theory can be applied to explain the behavior of nanobubbles in different electrolytic solutions. In this research, oxygen nanobubbles were generated in NaCl solutions of different concentrations, and bubble size and ζ potentials were measured just after the generation and after 1 week. The measured data and diffused double layer theory were used to compute the surface charge density, the potential due to the surface charge, and the interaction energy between bubbles. With the increased NaCl concentration, bubble size, surface charge density, and the number of negative charges increased, while the magnitude of ζ potential/surface potential, double layer thickness, internal pressure, and the electrostatic repulsion force decreased. The same trend was observed after 1 week. The net total energy calculation for the 0.001 M NaCl solution showed that the bubble repulsion for an intermediate separation distance had a 6.99 × 10 –20 J energy barrier, which prevented bubble coalescence. Hence, the 0.001 M NaCl…

Pattern formation is a frequent phenomenon in physics, chemistry, biology, and materials science. Bottom-up pattern formation usually occurs in the interaction of the transport phenomena of chemical species with their chemical reaction. The oldest pattern formation is the Liesegang phenomenon (or periodic precipitation), which was discovered and described in 1896 by Raphael Edward Liesegang, who was a German chemist and photographer who was born 150 years ago. The purpose of this feature article is to provide a comprehensive overview of this type of pattern formation. Liesegang banding occurs because of the coupling of the diffusion process of the reagents with their chemical reactions in solid hydrogels. We will discuss several phenomena observed and discovered in the past century, including reverse patterns, precipitation patterns with dissolution (due to complex formation), helicoidal patterns, and precipitation waves. Additionally, we will review all existing models of the Liesegang phenomenon including pre- and postnucleation scenarios. Finally, we will highlight several…

One of the major challenges associated with fuel cells is exploring highly efficient and low-cost electrocatalysts for the oxygen reduction reaction (ORR). Herein, the feasibility of using Ti 3 C 2 MXene nanoparticles (NPs) to enhance the electrocatalytic activity of g-C 3 N 4 for ORR was investigated. By varying the content of Ti 3 C 2 NPs, a series of g-C 3 N 4 /Ti 3 C 2 heterostructures were obtained, displaying enhanced electrocatalytic activity, including a positive shift in both onset and peak potentials toward ORR, compared to the original g-C 3 N 4 in basic solution. We attribute the improvement to the favorable electrical conductivity of well-dispersed Ti 3 C 2 MXene nanoparticles and also enhanced O 2 adsorption due to the electronic coupling effect between g-C 3 N 4 and Ti 3 C 2 in the heterostructures. This work demonstrates the potential of earth-abundant MXene family materials to construct low-cost and high-performance electrocatalysts.

This Feature Article focuses on recent advances in the bioconjugation of surface-bound zwitterionic polymers for biospecific antifouling surfaces. Various approaches for the functionalization of antifouling zwitterionic polymers are systematically investigated, such as chain-end and side-chain functionalization. Side-chain functionalization methods can be further classified as those that are achieved through homopolymerization of custom-synthesized zwitterionic monomers equipped with reactive groups, or those that are achieved via synthesis of random or block copolymers combining different monomers with antifouling functionality and others with reactive groups. Several of the pros and cons of these approaches are outlined and discussed. Finally, some perspective and future directions of research are presented toward long-term stable, generically repelling surfaces that strongly and specifically adhere to a single component in a complex mixture.

The pursuit of antibacterial properties on the surfaces of food container, medical equipment, and pharmaceutical tanks has been a compelling challenge for decades. Inspired by the biomimetic superhydrophobic surfaces that have self-cleaning, antifog, antisnow, and reduced bacterial adhesion properties, we use a simple and effective technology of a picosecond laser texturing for the fabrication of a superhydrophobic antibacterial surface on AISI 420 martensitic stainless steel plates. The laser-textured surface with micropapillae patterns with superimposed nanostructures exhibits outstanding in-air superhydrophobic and superaerophilicity underwater, which under the oscillation state resists an adhesion of 99% Escherichia coli and 93% Staphylococcus aureus and has hardly any bacterial adhesion under a stationary state. The comparative experiments verify that the robust air layer and hierarchical micro–nanostructures have come together to comprise the antibacterial mechanism. The laser-textured superhydrophobic surface also exhibits superior anticorrosion and antidestructive abilities…

The superhydrophobic leaves of a lotus plant and other natural surfaces with self-cleaning function have been studied intensively for the development of artificial biomimetic surfaces. The surface roughness generated by hierarchical structures is a crucial property required for superhydrophobicity and self-cleaning. Here, we demonstrate a novel self-cleaning mechanism of textured surfaces attributed to a spontaneous coalescence-induced wetting transition. We focus on the wetting transition as it represents a new mechanism, which can explain why droplets on rough surfaces are able to change from the highly adhesive Wenzel state to the low adhesion Cassie-Baxter state and achieve self-cleaning. In particular, we perform many-body dissipative particle dynamics simulations of liquid droplets (with a diameter of 89 μm) sitting on mechanically textured substrates. We quantitatively investigate the wetting behavior of an isolated droplet as well as coalescence of droplets for both Cassie-Baxter and Wenzel states. Our simulation results reveal that droplets in the Cassie-Baxter state have…

In this work, zeolite-based sorbents were developed from gasified rice husk. CO 2 capture capacity of the sorbents was examined at various temperatures and pressures employing a fixed-bed flow reactor and simulated flue gas. Various physicochemical properties such as thermal stability, pore size distribution, morphology, chemical composition, etc. of the in-house-developed materials were characterized in detail and were also compared with two commercially available zeolites. Tetra-ethylenepentamine was impregnated in the in-house-developed zeolite supports to investigate its suitability to improve the CO 2 adsorption capacity. The effects of reactor pressure, temperature, Si/Al ratio, and amine loading on CO 2 uptake capacity were examined. A declining trend in CO 2 adsorption capacity was observed with the increase in adsorption temperature and amine loading. At 30 °C, zeolite-Y (designated as Z-Y-3, silica to alumina ratio of 2.25) sample exhibited maximum adsorption capacity, and the obtained values were around 114 and 190 mg CO 2 /g sorbent under atmospheric and 5 bar pressure,…

The adsorption of dye molecules is an important process for the photodegradation removal of dye pollutants. In this work, a semiconductor photocatalyst of Cr-doped ZnO nanorods (Cr–ZnO NRs) was synthesized, and its adsorption–photocatalysis synergy (APS) effect was investigated for anionic methyl orange (MO – ) and cationic methylene blue (MB + ). The detailed thermodynamic information (including adsorption maximum capacity q max, adsorption equilibrium constant K ads and adsorption efficiency AE %) and dynamic information (including adsorption rate constant k a, degradation rate constant k d and degradation efficiency DE %) were obtained to evaluate the different reaction performances for MO – and MB + . With q max(MB + ) = 40.59 mg g –1 > q max(MO – ) = 15.95 mg g –1, k a(MB + ) = 20.61 min –1 > k a(MO – ) = 4.62 min –1, and AE (MB + ) = 40% > AE (MO – ) = 9%, Cr–ZnO NRs showed much superior adsorption performance for MB + than MO – . With k d (MB + ) = 0.0430 min –1 > k d (MO – ) = 0.0014 min –1 and DE (MB + ) = 98% > AE (MO – ) = 20%, Cr–ZnO NRs also showed much superior…

We report a thorough, multitechnique investigation of the structure and transport properties of a UV-cross-linked polymer electrolyte based on poly(ethylene oxide), tetra(ethylene glycol)dimethyl ether (G4), and lithium bis(trifluoromethane)sulfonimide. The properties of the cross-linked polymer electrolyte are compared to those of a non-cross-linked sample of same composition. The effect of UV-induced cross-linking on the physico/chemical characteristics is evaluated by X-ray diffraction, differential scanning calorimetry, shear rheology, 1 H and 7 Li magic angle spinning nuclear magnetic resonance (NMR) spectroscopy, 19 F and 7 Li pulsed field gradient stimulated echo NMR analyses, electrochemical impedance spectroscopy, and Fourier transform Raman spectroscopy. Comprehensive analysis confirms that UV-induced cross-linking is an effective technique to suppress the crystallinity of the polymer matrix and reduce ion aggregation, yielding improved Li + transport number (>0.5) and ionic conductivity (>0.1 mS cm?1 ) at ambient temperature, by tailoring the structural/morphological…

The emulsifying and dispersing mechanisms of oil-in-water emulsions stabilized by 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO)-oxidized cellulose nanofibers (CNFs) have been investigated. The emulsifying mechanism was studied by changing the oil/water interfacial tension from 8.5 to 53.3 mN/m using various types of oils. The results showed that the higher the oil/water interfacial tension, the greater is the amount of CNFs adsorbed at the oil/water interface, making the CNF-adsorbed oil-in-water emulsions thermodynamically more stable. Moreover, the amount of CNFs adsorbed on the surfaces of the oil droplets increased with increasing interfacial area. The dispersion stability of the oil droplets was dominated by the CNF concentration in the water phase. Above the critical concentration (0.15% w/w), the CNFs formed network structures in the water phase, and the emulsion was effectively stabilized against creaming. Emulsion formation and the CNF network structures in the emulsion were visualized by cryo-scanning electron microscopy.

Gallium and its alloys react with oxygen to form a native oxide that encapsulates the liquid metal with a solid "skin". The viscoelasticity of this skin is leveraged in applications such as soft electronics, 3D printing, and components for microfluidic devices. In these applications, rheological characterization of the oxide skin is paramount for understanding and controlling liquid metals. Here, we provide a direct comparison of the viscoelastic properties for gallium-based liquid metals and illustrate the effect of different subphases and addition of a dopant on the elastic nature of the oxide skin. The du Noüy ring method is used to investigate the interfacial rheology of oxide skins formed by gallium-based liquid metal alloys. The results show that the oxide layer on gallium, eutectic gallium-indium, and Galinstan are viscoelastic with a yield stress. Furthermore, the storage modulus of the oxide layer is affected by exposure to water or when small amounts of aluminum dopant are added to the liquid metals. The former scenario decreases the interfacial storage modulus of the…

Polymer materials have been widely used in industrial, agricultural, engineering, medical, electronic, and biological fields because of their excellent and diverse properties (e.g., mechanical, optical, electrical, and adhesive properties). The adhesion of polymer materials can affect the stability, alter the surface chemistry, change the surface structure, and influence the performance of the materials. It is of both fundamental and practical importance to understand the adhesion behaviors and interaction mechanisms of polymer surfaces and thin films for the development of new functional polymers and their applications. In this article, the fundamentals of surface energy, adhesion energy, and classical contact mechanics models are presented first, and the commonly used nanomechanical techniques for quantifying the intermolecular and surface interactions of polymers, including the surface forces apparatus (SFA) and atomic force microscope (AFM), are introduced. The advances in the adhesion of surfaces and thin films of various polymers (e.g., elastomers, glassy polymers) are…

A fundamental limitation of liquids on many surfaces is their contact line pinning. This limitation can be overcome by infusing a nonvolatile and immiscible liquid or lubricant into the texture or roughness created in or applied onto the solid substrate so that the liquid of interest no longer directly contacts the underlying surface. Such slippery liquid-infused porous surfaces (SLIPS), also known as lubricant-impregnated surfaces, completely remove contact line pinning and contact angle hysteresis. However, although a sessile droplet may rest on such a surface, its contact angle can be only an apparent contact angle because its contact is now with a second liquid and not a solid. Close to the solid, the droplet has a wetting ridge with a force balance of the liquid-liquid and liquid-vapor interfacial tensions described by Neumann's triangle rather than Young's law. Here, we show how, provided the lubricant coating is thin and the wetting ridge is small, a surface free energy approach can be used to obtain an apparent contact angle equation analogous to Young's law using…

We investigate the existence and stability of bulk nanobubbles in various aqueous organic solvent mixtures. Bulk nanobubble suspensions generated via acoustic cavitation are characterized in terms of their bubble size distribution, bubble number density, and zeta potential. We show that bulk nanobubbles exist in pure water but do not exist in pure organic solvents, and they disappear at some organic solvent-water ratio. We monitor the nanobubble suspensions over a period of a few months and propose interpretations for the differences behind their long-term stability in pure water versus their long-term stability in aqueous organic solvent solutions. Bulk nanobubbles in pure water are stabilized by their substantial surface charge arising from the adsorption of hydroxyl ions produced by self-ionization of water. Pure organic solvents do not autoionize, and therefore, nanobubbles cannot exist in concentrated aqueous organic solvent solutions. Because of preferential adsorption of organic solvent molecules at the nanobubble interfaces, the surface charge of the nanobubbles decreases…

Abstract Fluorescent carbon dots (CDs) are of interest as a promising alternative to quantum dots, partly because they do not include heavy metals. However, most CDs exhibit blue or green emission, while red-emitting CDs are required for a variety of applications. In the present work, CDs were synthesized by refluxing three phenylenediamine (PD) isomers with amino groups at different positions (o-PD, m-PD, and p-PD) in diphenyl ether at 250 °C for 4 h. Upon dispersing the resulting CDs in eight solvents with different polarities, emission colors ranging from green to red were observed. Among these CDs, p-PD-derived CDs exhibited both the longest emission wavelength range, from 538 to 635 nm, and the highest absolute red photoluminescence quantum yield (PLQY) of 15%. Herein the results are discussed based on a comparison of the polymerization processes of o-PD, m-PD, and p-PD. This work demonstrated that the optimum reaction time was 2 h, which yields a p-PD-derived CD dispersion in methanol with red emission and an absolute PLQY as high as 18%. Additionally, the use of 1-decanol and…

The existence of bulk nanobubbles is still controversial in spite of their significance in a large range of applications. Here, we developed a new method of compression-decompression to produce controllably bulk nanobubbles. Then, we further investigated the generation of bulk nanobubbles in pure water, acid, alkaline, and salt solutions using nanoparticle tracking analysis. The results indicated that the concentration of bulk nanobubbles depends on the decompression time and would reach a maximum value when the decompression time is about 30 min for the pure water system. More importantly, we gave a relatively direct evidence of the existence of bulk nanobubbles by measuring the X-ray fluorescence intensity of Kr in acid, alkaline, and salt solutions. It is shown that the decrease tendency in intensity of Kr in alkaline solution is similar to that in the concentration of bulk nanobubbles with the deposited time, indicating that the bulk nanobubbles produced indeed have gas inside. Furthermore, the concentration and stability of bulk nanobubbles in an alkaline solution are greatest…

Surface free energy remains a fundamental material property to characterize the interfacial interactions between liquid and solid. Here, we developed a precise approach to determine surface energy by using contact angles of binary mixtures of water–dimethyl sulfoxide (DMSO), water–formamide, water–ethylene glycol, and water–glycerol and analyzed using the Owens–Wendt method. A mixing equation was developed to estimate liquid-dispersive surface tension (γ L,mix d ) and polar surface tension (γ L,mix p ) parameters for binary mixtures. To test the approach, two hydrophobic surfaces, flat polydimethylsiloxane (PDMS), and silane-derivatized glass were prepared and the contact angle of mixtures on the surfaces were obtained. Surface energy of PDMS determined by three binary mixtures agrees with that from pure solvents, but the uncertainty decreases to less than 13%; remarkably, the uncertainty drops to around 5% once we combined measured contact angles from all the mixtures, namely, water–DMSO, water–formamide, and water–ethylene glycol. Surface energies of silane-derivatized glass…

Development of advanced fluorescent materials for constructing a secure and unclonable encryption is urgently required; however, their application in anti-counterfeiting applications is a great challenge. In this work, we proposed and synthesized a new type of upconversion [email protected] [email protected] 2 nanohybrids by integrating two fluorescent materials of lanthanide-doped NaYF 4 upconversion nanoparticles (UCNPs) and carbon dots (CDs) into mesoporous silica (mSiO 2 ) to produce a novel sandwichlike core–shell structure and a dual-mode fluorescence from UCNPs and CDs. By tailoring the UCNP core of different upconversion luminescence, all three kinds of dual-mode luminescent [email protected] @mSiO 2 nanohybrids exhibited typical RGB upconversion luminescence under a 980 nm laser and blue downconversion luminescence under a 365 nm UV light. Due to strong the hydrophilic nature of the nanohybrids, they can be further fabricated into environmentally benign luminescent inks for creating highly secured, fluorescent-based, three-dimensional anti-counterfeiting barcodes via inkjet…

Attaching thiolated DNA to gold nanoparticles (AuNPs) is a highly important and useful reaction for many applications. Various methods such as adding salts, acids, polymers, and surfactants have been developed to facilitate the reaction. Recently, it was reported that a very high DNA density can be achieved simply by freezing AuNPs with the DNA without any other reagents. DNA oligonucleotides are also known to stretch and align upon freezing. In this work, a set of experiments were performed with a fluorophore and thiol dual-labeled DNA, and the DNA loading density and colloidal stability of AuNPs were measured. The initial salt concentration was unimportant, and even 0.1 mM Na + allowed around 100 DNA attached to each 13 nm AuNPs. On the other hand, a high DNA concentration of 3 μM was needed to achieve the high DNA density and good colloidal stability of AuNPs. When the thiolated DNA was forced in stable secondary structures, the attachment was low, and preadsorbed DNA also inhibited the DNA attachment by the freezing method. Overall, nonstructured thiolated DNA strands need to…

oil (BJO) and doxorubicin hydrochloride (DOX) and display a pH-induced inverted hexagonal (pH = 7.4) to cubic (pH = 6.8) to emulsified microemulsion (pH = 5.3) phase transition with a therapeutic application in cancer inhibition. BJO is a traditional herbal medicine that strongly inhibits the proliferation and metastasis of various cancers. Doxorubicin is an antitumor drug, which prevents DNA replication and hampers protein synthesis through intercalation between the base pairs of the DNA helices. Its dose-dependent cardiotoxicity imposes the need for safe delivery carriers. Here, pH-induced changes in the structural and interfacial properties of designed multicomponent drug delivery (monoolein-oleic acid-BJO-DOX) systems are determined by synchrotron small-angle X-ray scattering and the Langmuir film balance technique. The nanocarrier assemblies display good physical stability in the studied pH range and adequate particle sizes and ζ-potentials. Their interaction with model lipid membrane interfaces is enhanced under acidic pH conditions, which mimic the microenvironment around…

Abstract Enhanced recovery of shale gas with CO2 injection has attracted extensive attention as it combines the advantages of improved efficiency of shale gas recovery and reduced greenhouse gas emissions via CO2 geological sequestration. On the other hand, the microscopic mechanism of enhanced shale gas recovery with CO2 injection and the influence of the subsurface water confined in the shale nanopores remain ambiguous. Here, we use grand canonical Monte Carlo (GCMC) simulations to investigate the effect of moisture on the shale gas recovery and CO2 sequestration by calculating the adsorption of CH4 and CO2 in dry and moist kerogen slit pores. Simulation results indicate that water accumulates in the form of clusters in the middle of the kerogen slit pore. Formation of water clusters in kerogen slit pores reduces pore filling by methane molecules, resulting in a decrease in the methane sorption capacity. For the sorption of CH4/CO2 binary mixtures in kerogen slit pores, the CH4 sorption capacity decreases as the moisture content increases, whereas the effect of moisture on CO2…

In this research, the anisotropic superhydrophobic surface is prepared on a stainless steel surface by laser etching, and the drag reduction property of the anisotropic surface is studied by a self-designed solid-liquid interface friction test device. Periodic arrangement structures of quadrate scales with oblique grooves are obtained on a stainless steel surface by a laser. After modification by fluoride, the surface shows superhydrophobicity and anisotropic adhesive property. Here, the inclined direction of grooves and the inverse direction are defined as RO and OR, respectively. By changing the inclination of the grooves, a surface is obtained with a contact angle of 160° and a rolling angle difference of 6° along the RO and inverse RO direction. It is verified by numerical simulation and experiment that the subjected force of water droplets on the surface is different along the RO and inverse RO direction. Furthermore, the as-prepared surface has different drag reduction effects along the two directions. With the increase of velocity, the drag reduction effect of the…

Low-molecular-weight gels are formed by the self-assembly of small molecules into fibrous networks that can immobilize a significant amount of solvent. Here, we focus on our work with a specific class of gelator, the functionalized dipeptide. We discuss the current state of the art in the area, focusing on how these materials can be controlled. We also highlight interesting and unusual observations and unanswered questions in the field.

Amyloid–carbon hybrid membranes have exceptional performance in removing heavy metal ions from water because of the presence of multiple binding sites on the amyloid fibrils, but the binding process is still not fully understood. To understand the mechanisms of amyloid–metal ion binding, we perform adsorption isotherms on a model system given by β-lactoglobulin amyloid fibrils and four representative heavy metal ions: chromium (Cr), nickel (Ni), silver (Ag), and platinum (Pt). Furthermore, to get a comprehensive thermodynamic picture of the binding process between amino acid residues and heavy metals, we here use isothermal titration calorimetry on native β-lactoglobulin monomers and amyloid fibrils exposed to the two model metal ions, that is, silver and chromium. A conclusive thermodynamic insight on the binding process emerges by direct measurements of enthalpy and entropy changes, association binding constant, and average number of binding sites of the protein monomer and amyloid fibril. As a result of the strong amyloid binding affinity between amino acids and metal ions, when…

Liposomes are well-established systems for drug delivery and biosensing applications. The design of a liposomal carrier requires careful choice of lipid composition and formulation method. These determine many vesicle properties including lamellarity, which can have a strong effect on both encapsulation efficiency and the efflux rate of encapsulated active compounds. Despite this, a comprehensive study on how the lipid composition and formulation method affect vesicle lamellarity is still lacking. Here, we combine small-angle neutron scattering and cryogenic transmission electron microscopy to study the effect of three different well-established formulation methods followed by extrusion through 100 nm polycarbonate membranes on the resulting vesicle membrane structure. Specifically, we examine vesicles formulated from the commonly used phospholipids 1-palmitoyl-2-oleoyl- sn-glycero-3-phosphocholine (POPC), 1,2-dipalmitoyl- sn-glycero-3-phosphocholine (DPPC) and 1,2-dioleoyl- sn-glycero-3-phosphocholine (DOPC) via film hydration followed by (i) agitation on a shaker or (ii)…

In this study, spent bleaching earth (SBE) and pyrolyzed SBE (SBE@C) were tested for their capacity to remove tetracycline hydrochloride (TCH) from aqueous solution. The maximum adsorption capacity obtained by the Langmuir model is 0.114 mmol/g for SBE@C and 0.087 mmol/g for SBE. The deleterious effects of coexisting cations were ranked in a decline: Al 3+ > Mg 2+ > Na + . The results of various characterization methods show that the adsorption mechanisms mainly included π–π interactions, hydrogen bonding, electrostatic interactions, and changes in physical and chemical properties. After 3 repeated cycles of pyrolysis, the adsorption capacity of SBE@C remained at 85.4%, with SBE@C potentially recycled 21 times before complete loss of adsorption capacity. Furthermore, the problem of secondary pollution caused by SBE and residual oil is resolved by the use of SBE@C. All results indicate that SBE@C is a likely candidate for the treatment of TCH wastewater in the coming practical applications.

The exfoliation of layered montmorillonite (MMT) into mono- or few-layer sheets is of significance for both fundamental studies and potential applications. In this report, exfoliated MMT nanosheets with different aspect ratios have been prepared via a new freezing/thawing-ultrasonic exfoliation method. Freezing/thawing processing can exfoliate MMT tactoids with low efficiency while virtually retaining the original lateral size. The ultrasonic method has better exfoliation efficiency but tends to damage the nanosheets. By combining them and reasonably controlling the cycle index of freezing/thawing and ultrasonic power, the MMT nanosheets with different aspect ratios have been prepared efficiently. Such a unique exfoliation method has broad applicability for layered materials to produce monolayer nanosheets on a large scale.

Cocatalysts play a significant role in accelerating the catalytic reactions of semiconductor photocatalyst. In particular, a semiconductor assembled with dual cocatalysts, i.e., reduction and oxidation cocatalysts, can obviously enhance the photocatalytic performance because of the synergistic effect of fast consumption of photogenerated electrons and holes simultaneously. However, in most cases, noble metal cocatalysts are employed, which tremendously increases the cost of the photocatalysts and restricts their large-scale applications. Herein, on the platform of one-dimensional (1D) CdS nanowires, we have utilized the earth-abundant dual cocatalysts, MoS 2 and cobalt phosphate (Co–Pi), to construct the CdS@MoS 2 @Co–Pi (CMC) core–shell hybrid photocatalysts. In this dual-cocatalyst system, Co–Pi is in a position to expedite the migration of holes from CdS, while MoS 2 acts as an electron transporter as well as active sites to accelerate the surface water reduction reaction. Taking the advantages of the dual-cocatalyst system, the prepared CMC hybrid shows an obvious enhancement of…

Carbon dots (CDs) are a novel class of nanoparticles with excellent properties. The development of CDs involves versatile synthesis, characterization, and various applications. However, the importance of surface chemistry of CDs, especially in applications, is often underestimated. In fact, the study of the surface chemistry of CDs is of great significance in the explanation of the unique properties of CDs as well as the pursuit of potential applications. In this feature article, we do not only introduce the development of CDs in our group but also highlight their applications where surface chemistry plays a critical role.

The volume phase transition of microgels is one of the most paradigmatic examples of stimuli-responsiveness, enabling a collapse from a highly swollen microgel state into a densely coiled state by an external stimulus. Although well characterized in bulk, it remains unclear how the phase transition is affected by the presence of a confining interface. Here, we demonstrate that the temperature-induced volume phase transition of poly( N -isopropylacrylamide) microgels, conventionally considered an intrinsic molecular property of the polymer, is in fact largely suppressed when the microgel is adsorbed to an air/liquid interface. We further observe a hysteresis in the core morphology and interfacial pressure between heating and cooling cycles. Our results, supported by molecular dynamics simulations, reveal that the dangling polymer chains of microgel particles, spread at the interface under the influence of surface tension, do not undergo any volume phase transition. The balance in free energy responsible for the volume phase transition is fundamentally altered by interfacial…

The corrosion of ferritic steel, a widely used structural material in the power and nuclear industries exposed to humid coastal environments, is a major concern. Here, we present a template-free one-step electrodeposition method for the fabrication of a robust superhydrophobic (SHP) coating on ferritic steel with excellent mechanical stability, enhanced corrosion resistance, and self-cleaning ability. By varying the electrodeposition time and potential, the micronanoscale hierarchical surface structures were optimized. The coated SHP surfaces were characterized by water contact angle measurement, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The coated surfaces showed a characteristic cauliflower morphology of cerium myristate with micronanoscale features. The maximum water contact angle achieved was 162.8 ± 2.4°. Shear abrasion testing showed good mechanical durability for the prepared coatings. The as-prepared SHP coating showed a five order reduction in corrosion current density (4.14 × 10 –11 A/cm 2 ) and corrosion rate (4.63 × 10 –7…

Ion-containing perfluorinated polymers possess unique viscoelastic properties, excellent proton conductivity, and nanophase-segregated structure all arising from the clustering of hydrophilic sulfonic acid groups within a matrix of hydrophobic fluorocarbons. When these ionomers are confined to nanothin films, a broad swathe of structural organization imparting a rich variety of surface, interfacial, and bulk characteristics can be expected. However, our understanding of perfluorinated ionomer thin film behavior is still in a rudimentary stage, and much of the research focus to date has been on its hydration-related structure and properties pertinent to electrochemical applications. Thus, many hidden gems-their interesting surface and interfacial properties-have been overlooked. In this Invited Feature Article, which is a summary of the key contributions by the author's group, including several collaborative publications on ionomer thin films, we unravel many of these facets. In addition, the article attempts to integrate knowledge acquired from a variety of investigations of…

In this work, we report a facile one-spot synthesis process and the influence of compositional variation on the electrochemical performance of Ni-Mn-oxides (Ni:Mn = 1:1, 1:2, 1:3, and 1:4) for high-performance advanced energy storage applications. The crystalline structure and the morphology of these synthesized nanocomposites have been demonstrated using X-ray diffraction, field emission scanning electron microscopy, and transmission electron Microscopy. Among these materials, Ni-Mn-oxide with Ni:Mn = 1:3 possesses a large Brunauer?Emmett?Teller specific surface area (127 m 2 g?1 ) with pore size 8.2 nm and exhibits the highest specific capacitance of 1215.5 F g?1 at a scan rate 2 mV s?1 with an excellent long-term cycling stability (?87.2% capacitance retention at 10 A g?1 over 5000 cycles). This work also gives a comparison and explains the influence of different compositional ratios on the electrochemical properties of Ni-Mn-oxides. To demonstrate the possibility of commercial application, an asymmetric supercapacitor device has been constructed by using Ni-Mn-oxide (Ni:Mn =…

Thin films (0-30 nm) of very concentrated aqueous monovalent salt solutions (2-10 M of LiCl, NaCl, and CsCl) were examined to determine how ionic strength affects the screening length of the electrostatic potential. Measurements were consistent with a screening length in the range of 3-12 nm. The screening length increased monotonically as a function of salt concentration, and the rate of increase was a function of the monovalent salt type. The results were incompatible with the Debye length of Poisson-Boltzmann theory but consistent with previous measurements of surface forces. The screening length was determined from the surface excess of fluorescein, a dianion under basic conditions, which was present in trace amounts in the thin film and detected via its fluorescence emission. That is, we directly observed that the ion concentration in very concentrated solutions is perturbed far from an interface.

A self-assembly of clay nanotubes in functional arrays for the production of organized organic/inorganic heterostructures is described. These 50-nm-diameter natural alumosilicate nanotubes are biocompatible. Halloysite allows for 10–20 wt % chemical/drug loading into the inner lumen, and it gives an extended release for days and months (anticorrosion, self-healing, flame-retardant, antifouling, and antibacterial composites). The structured surfaces of the oriented nanotube micropatterns enhance interactions with biological cells, improving their capture and inducing differentiation in stem cells. An encapsulation of the cells with halloysite enables control of their growth and proliferation. This approach was also developed for spill petroleum bioremediation as a synergistic process with Pickering oil emulsification. We produced 2–5-nm-diameter particles (Au, Ag, Pt, Co, Ru, Cu–Ni, Fe 3 O 4, ZrO 2, and CdS) selectively inside or outside the aluminosilicate clay nanotubes. The catalytic hydrogenation of benzene and phenol, hydrogen production, impacts of the metal core–shell…

Microfluidics is one of the most fascinating fields that researchers have been trying to apply in a large number of scientific disciplines over the past two decades. Among them, the discipline of food and pharmaceutical formulation encountered several obstacles when combining microfluidics with aqueous media. Indeed, the physical properties of liquids at micrometric volumes being particular, the droplet generation within microfluidic devices is a big challenge to be met. This focus review is intended to be an initiation for those who would like to generate microdroplets in microfluidic systems involving aqueous continuous phases. It provides a state-of-the-art look at such systems while focusing on the microfluidic devices used, their applications to form a wide variety of emulsions and particles, and the key role held by the interface between the device channels and the emulsion. This review also leads to reflections on new materials that can be used in microfluidic systems with aqueous continuous phases.

The use of soft microgel particles for stabilizing emulsions has captured increasing attention across a wide range of disciplines in the past decades. Being soft, the nanoparticles, which are spherical in solution, undergo a structure change when adsorbed at the oil-water interface. This morphology change leads to the special dynamic properties of interface layers and packing structures, which then alter the interfacial tension and rheological properties of the interface. In addition, emulsions stabilized by these particles, known as Pickering emulsions, can be triggered by changing a variety of environmental conditions, which is especially desirable in industrial applications such as oil transportation processes and biphasic catalysis, where the emulsions can be stabilized and destabilized on demand. Although many studies of the behavior of soft microgel nanoparticles at interfaces have been reported, there are still many challenges in gaining a full understanding of the structure, dynamics, and effective interactions between microgels at the interface. In this Feature Article, we…

Compartmentalization by complex coacervation is important across a range of different fields including subcellular and prebiotic organization, biomedicine, food science, and personal care products. Often, lipid self-assemblies such as vesicles are also present intracellularly or in commercial formulations. A systematic understanding of how phospholipid vesicles interact with different complex coacervates could provide insight and improve control over these systems. In this manuscript, anionic phospholipid vesicles were added to a series of different complex coacervate samples in which coacervates were formed by mixing one of five polycations with one of three (poly)anions that varied in chemical structure and length. Vesicles were found to assemble at the coacervate/continuous phase interface and/or form aggregates. We report how factors such as the charge density of polyelectrolytes and the charge ratio of cationic-to-anionic moieties impact the vesicle distribution in coacervate samples. Our findings emphasize the importance of interactions between vesicles and polycations in the…

In this paper, we present a highly efficient, cost-effective, and widely applicable functionalized SiO 2 /TiO 2 -polymer based coating to fabricate a translucent, fluorine-free, chemically stable, photocatalytic active, self-healable superhydrophobic coating, which consisted of two mixed functionalized particles (MFP) and polydimethylsiloxane (PDMS) in a proper ratio. Both SiO 2 and TiO 2 powders were functionalized with PDMS brushes to achieve superhydrophobicity. To maximally optimize its properties, including superhydrophobicity, transparency, and photocatalytic activity, the ratios between MFP with PDMS were carefully studied and optimized. Glass slides coated with this mixed coating (MC) showed translucence with a transparency of 75%. It also presented superior photocatalytic activity and strong UV resistance that could repeatedly degrade organic oil pollutants as many as 50 times, while still maintaining superhydrophobicity even upon exposure to UV light with a high intensity of 80 mW/cm 2 for as long as 36 h. When low-surface-tension oils such as dodecane wetted the MC…

The dielectric constant for water is reduced under confinement. Although this phenomenon is well known, the underlying physical mechanism for the reduction is still in debate. In this work, we investigate the effect of the orientation of hydrogen bonds on the dielectric properties of confined water using molecular dynamics simulations. We find a reduced rotational diffusion coefficient for water molecules close to the solid surface. The reduced rotational diffusion arises due to the hindered rotation away from the plane parallel to the channel walls. The suppressed rotation in turn affects the orientational polarization of water, leading to a low value for the dielectric constant at the interface. We attribute the constrained out-of-plane rotation to originate from a higher density of planar hydrogen bonds formed by the interfacial water molecules.

The ability to make stable water-in-oil and oil-in-water millimeter-size Pickering emulsions is demonstrated using Janus particles-particles with distinct surface chemistries. The use of a highly cross-linked hydrophobic polymer network and the excellent water-wetting nature of a hydrogel as the hydrophobic and hydrophilic sides, respectively, permit distinct wettability on the Janus particle. Glass capillary microfluidics allows the synthesis of Janus particles with controlled sizes between 128 and 440 μm and control over the hydrophilic-to-hydrophobic domain volume ratio of the particle from 0.36 to 12.77 for a given size. It is shown that the Janus particle size controls the size of the emulsion drops, thus providing the ability to tune the structure and stability of the resulting emulsions. Stability investigations using centrifugation reveal that particles with the smallest size and a balanced hydrophilic-to-hydrophobic volume ratio (Janus ratio) form emulsions with the greatest stability against coalescence. Particles eventually jam at the interface to form nonspherical…