The 50 most-cited articles in Langmuir, 2018

Abstract Bulk nanobubbles are a novel type of nanoscale bubble system. Because of their extraordinary behavior, however, their existence is not widely accepted. In this paper, we shed light on the hypothesis that bulk nanobubbles do exist, they are filled with gas, and they survive for long periods of time, challenging present theories. An acoustic cavitation technique has been used to produce bulk nanobubbles in pure water in relatively large numbers approaching 109 bubble·mL–1 with a typical diameter of 100–120 nm. We provide multiple evidence that the nanoentities observed in suspension are nanobubbles given that they disappear after freezing and thawing of the suspensions, their nucleation rate depends strongly on the amount of air dissolved in water, and they gradually disappear over time. The bulk nanobubble suspensions were stable over periods of many months during which time the mean diameter remained unchanged, suggesting the absence of significant bubble coalescence, bubble breakage, or Ostwald ripening effects. Measurements suggest that these nanobubbles are negatively…

The role of nanoparticles in cancer medicine is vast with debate still surrounding the distinction between therapeutic efficacy of actively targeted nanoparticles versus passively targeted systems for drug delivery. While it is commonly accepted that methodologies that result in homing a high concentration of drug loaded nanoparticles to the tumor is beneficial, the role of intracellular trafficking of these nanoparticles in dictating the overall therapeutic outcome remains unresolved. Herein we demonstrate that the therapeutic outcome of drug loaded nanoparticles is governed beyond simply enabling nanoparticle internalization in cells. Using two model polymeric nanoparticles, one decorated with the GE11 peptide for active targeting of the epidermal growth factor receptor (EGFR) and the other without, we demonstrate that EGFR mediated intracellular internalization results in an enhanced therapeutic effect compared to the nontargeted formulation. Our findings demonstrate that the intracellular destination of nanoparticles beyond its ability to internalize is an important parameter…

Superlubricity based on hydration lubrication provides a near-frictionless lubrication state for the extreme reduction of friction in aqueous conditions. Nevertheless, how to obtain the hydration superlubricity under macroscale conditions with higher load-carrying capacity still remains a challenge and the mechanisms governing macroscale superlubricity with hydrated ions are still not well comprehended. Here, we demonstrate that macroscale superlubricity based on hydrated alkali metal ions (Li +, Na +, K + ) can be realized under high contact pressure between the Si 3 N 4 ball and sapphire disk. The ultralow friction coefficients of 0.005 are obtained under average contact pressure up to 0.25 GPa by a universal micro-tribometer after a running-in period with acid solutions. The results reveal that running-in stage with acid solutions can not only make the worn region smoother but also generate a silica layer that is easy to shear, which provides excellent boundary lubrication. The hydration superlubricity occurs because hydration shells surrounding the alkali metal ions could…

The exciting functionalities of natural superhydrophilic and superhydrophobic surfaces served as inspiration for a variety of biomimetic designs. In particular, the combination of both extreme wetting states to micropatterns opens up interesting applications, as the example of the fog-collecting Namib Desert beetle shows. In this paper, the beetle’s elytra were mimicked by a novel three-step fabrication method to increase the fog-collection efficiency of glasses. In the first step, a double-hierarchical surface structure was generated on Pyrex wafers using femtosecond laser structuring, which amplified the intrinsic wetting property of the surface and made it superhydrophilic (water contact angle < 10°). In the second step, a Teflon-like polymer (CF 2 ) n was deposited by a plasma process that turned the laser-structured surface superhydrophobic (water contact angle > 150°). In the last step, the Teflon-like coating was selectively removed by fs-laser ablation to uncover superhydrophilic spots below the superhydrophobic surface, following the example of the Namib Desert beetle’s…

For the acquisition of blood-compatible materials, various hydrophilic polymers for surface modification have been examined. Among them, polymers with a representative phospholipid polar group, the phosphorylcholine (PC) group, are a successful example. These polymers were designed from inspiration of the cell membrane surface and provide protein adsorption resistance even following contact with plasma. This important property is based on the unique hydration state of water molecules surrounding hydrated polymer; in other words, water molecules weakly interact with the polymers and maintain their favorable cluster structure through hydrogen bonding. These polymers are not only hydrophilic, but also electrically neutral, important characteristics which make hydrogen bonding with water molecules less likely to occur and avoid hydrophobic interactions. Phosphorylcholine groups and other zwitterionic structures are significant as hydrophilic functional groups meeting these important requirements. In this review, blood compatibility of a polymer having a PC group is introduced in…

The surface chemistry and adsorption behavior of submicrometer cellulosic and lignin particles have drawn wide-ranging interest in the scientific community. Here, we introduce their assembly at fluid/fluid interfaces in Pickering systems and discuss their role in reducing the oil/water interfacial tension, limiting flocculation and coalescence, and endowing given functional properties. We discuss the stabilization of multiphase systems by cellulosic and lignin colloids and the opportunities for their adoption. They can be used alone, as dual components, or in combination with amphiphilic molecules for the design of multiphase systems relevant to household products, paints, coatings, pharmaceutical, foodstuff, and cosmetic formulations. This invited feature article summarizes some of our work and that of colleagues to introduce the readers to this fascinating and topical area.

Polydopamine-based chemistry has been employed for various surface modifications attributed to the advantages of universality, versatility, and simplicity. Co-deposition of polydopamine (PDA) with polyethyleneimine (PEI) has then been proposed to realize one-step fabrication of functional coatings with improved morphology uniformity, surface hydrophilicity, and chemical stability. Herein, we report the co-deposition kinetics related to the solution composition with different dopamine/PEI ratios, PEI molecular weights, dopamine/PEI concentrations, and the substrate surface with varying chemistry and wettability. The addition of PEI to dopamine solution suppresses the precipitation of PDA aggregates, resulting in an expanded time window of steady co-deposition compared with that of PDA deposition. Low-molecular-weight PEI at low concentration accelerates the co-deposition process, while high-molecular-weight PEI and high concentration of either PEI or dopamine/PEI are detrimental to the co-deposition efficiency. Meanwhile, the surface morphology and chemical composition of the…

Laser ablation in liquid was used to prepare homogeneous copper–zinc alloy catalysts that exhibited excellent selectivity for C 2 H 4 in CO 2 electroreduction, with faradaic efficiency values as high as 33.3% at a potential of −1.1 V (vs reversible hydrogen electrode). The high proximity of Cu and Zn atoms on the surface of the catalyst was found to facilitate both stabilization of the CO* intermediate and its transfer from Zn atoms to their Cu neighbors, where further dimerization and protonation occur to give rise to a large amount of ethylene product. The new homogeneous nanocatalyst, along with the mechanism proposed for its performance, may be very helpful for in-depth understanding of processes related to carbon dioxide electroreduction and conversion.

A series of four cellulose nanocrystal (CNC) suspensions were prepared from bleached softwood kraft pulp using different conditions of sulfuric acid hydrolysis. The CNCs were identical in size (95 nm in length × 5 nm in width) but had different surface charges corresponding to the harshness of the hydrolysis conditions. Consequently, it was possible to isolate the effects of surface charge on the self-assembly and viscosity of the CNC suspensions across surface charges ranging from 0.27%S to 0.89%S. The four suspensions (never-dried, free of added electrolyte) all underwent liquid crystalline phase separation, but the concentration onset for the emergence of the chiral nematic phase shifted to higher values with increasing surface charge. Similarly, suspension viscosity was also influenced by surface charge, with suspensions of lower surface charge CNCs more viscous and tending to gel at lower concentrations. The properties of the suspensions were interpreted in terms of the increase in effective diameter of the nanocrystals due to the surface electrostatic repulsion of the negative…

We reported an example of metal–organic framework (MOF)-based porous liquid by dispersing ZIF-8 ({Zn(mim) 2 }, mim = 2-methylimidazole) nanocrystallites in ionic liquid (IL) of [Bpy][NTf 2 ] ( N -butyl pyridinium bis(trifluoromethyl sulfonyl)imide). Two essential challenges, stable colloid formation and porosity retention, have been overcome to prepare MOF-based porous liquid. Preventing ZIF-8 nanocrystals from aggregation before dispersing is vital to form a stable ZIF-8 colloid in IL via enhancing the interaction between ZIF-8 and IL. The resultant ZIF-8–[Bpy][NTf 2 ] colloid is able to be stable over months without precipitating. [Bpy][NTf 2 ] with larger ion sizes cannot occupy pores in ZIF-8, leaving the ZIF-8 cage empty for enabling access by guest molecules. The porosity of this porous liquid system was verified by positron (e + ) annihilation lifetime spectroscopy and I 2 adsorption in ZIF-8 in the colloid. MOF-based porous liquids could provide a new material platform for liquid-bed-based gas separations.

Nanostructured copper sulfide synthesized with the assistance of surfactant with nanoscale particle size and high Brunauer–Emmett–Teller surface area was for the first time applied for the capture of elemental mercury (Hg 0 ) from coal combustion flue gas. The optimal operation temperature of nano-CuS for Hg 0 adsorption is 75 °C, which indicates that injection of the sorbent between the wet flue gas desulfurization and the wet electrostatic precipitator systems is feasible. This assures that the sorbent is free of the adverse influence of nitrogen oxides. Oxygen (O 2 ) and sulfur dioxide exerted a slight influence on Hg 0 adsorption over the nano-CuS. Water vapor was shown to moderately suppress Hg 0 capture efficiency via competitive adsorption. The simulated adsorption capacities of nano-CuS for Hg 0 under pure nitrogen (N 2 ), N 2 + 4% O 2, and simulated flue gas reached 122.40, 112.06, and 89.43 mgHg 0 /g nano-CuS, respectively. Compared to those of traditional commercial activated carbons and metal sulfides, the simulated adsorption capacities of Hg 0 over the nano-CuS are at…

Many surfaces possessing robust super liquid repellency are hierarchically structured on the nano- and micrometer scales. Several examples are found in nature, such as the self-cleaning leaves of lotus plants and anisotropic, water-guiding rice leaves. Each surface design has unique properties optimized for specific wetting conditions. In this invited feature article, we review both natural and artificial hierarchical surface structures and their function in repelling liquids. We discuss different types of structures needed in various wetting situations and draw some general conclusions as a guideline for designing robust superhydrophobic and superoleophobic surfaces.

Two-dimensional (2D) nanomaterials have attracted considerable attention in biomedical and environmental applications due to their antimicrobial activity. In the interest of investigating the primary antimicrobial mode-of-action of 2D nanomaterials, we studied the antimicrobial properties of MnO 2 and MoS 2, toward Gram-positive and Gram-negative bacteria. Bacillus subtilis and Escherichia coli bacteria were treated individually with 100 μg/mL of randomly oriented and vertically aligned nanomaterials for ∼3 h in the dark. The vertically aligned 2D MnO 2 and MoS 2 were grown on 2D sheets of graphene oxide, reduced graphene oxide, and Ti 3 C 2 MXene. Measurements to determine the viability of bacteria in the presence of the 2D nanomaterials performed by using two complementary techniques, flow cytometry, and fluorescence imaging showed that, while MnO 2 and MoS 2 nanosheets show different antibacterial activities, in both cases, Gram-positive bacteria show a higher loss in membrane integrity. Scanning electron microscopy images suggest that the 2D nanomaterials, which have a…

Micromotors are an emerging class of micromachines that could find potential applications in biomedicine, environmental remediation, and microscale self-assembly. Understanding their propulsion mechanisms holds the key to their future development. This is especially true for a popular category of micromotors that are driven by asymmetric surface photochemical reactions. Many of these micromotors release ionic species and are propelled via a mechanism termed "ionic self-diffusiophoresis". However, exactly how it operates remains vague. To address this fundamental yet important issue, we have developed a dielectric-AgCl Janus micromotor that clearly moves away from the AgCl side when exposed to UV or strong visible light. Taking advantage of numerical simulations and acoustic levitation techniques, we have provided tentative explanations for its speed decay over time as well as its directionality. In addition, photoactive AgCl micromotors demonstrate interesting gravitactic behaviors that hint at three-dimensional transport or sensing applications. The current work presents a…

Ice formation and accretion on surfaces is a serious economic issue in energy supply and transportation. Recent strategies for developing icephobic surfaces are intimately associated with superwettability. Commonly, the superwettability of icephobic materials depends on their surface roughness and chemical composition. This article critically categorizes the possible strategies to mitigate icing problems from daily life. The wettability and classical nucleation theories are used to characterize the icephobic surfaces. Thermodynamically, the advantages/disadvantages of superhydrophobic surfaces are discussed to explain icephobic behavior. The importance of elasticity, slippery liquid-infused porous surfaces (SLIPSs), amphiphilicity, antifreezing protein, organogels, and stimuli-responsive materials has been highlighted to induce icephobic performance. In addition, the design principles and mechanism to fabricate icephobic surfaces with superwettability are explored and summarized.

Sulfated cellulose nanocrystals (CNC) with high surface charge density are inadequate for stabilizing oil-water emulsions, which limits their applications as interfacial stabilizers. We performed end-group modification by introducing hydrophobic chains (polystyrene) to CNC. Results showed that the modified CNC are more effective in emulsifying toluene and hexadecane than pristine CNC. Various parameters were investigated, such as concentration of particles, electrolytes, and polarity of solvents on the characteristics of the emulsions. This study provides strategies for the modification of cellulose nanocrystals to yield amphiphilic nanoparticles that enhance the stability of emulsions. Such systems, bearing biocompatible and environmentally friendly characteristics, are attractive for use in a wide range of industries spanning food, biomedicine, pharmaceuticals, cosmetics, and petrochemicals.

Abstract In recent years, there has been a resurgence of interest in Pickering emulsions because of the recognition of the unique high steric stabilization provided by particles at interfaces. This interest is particularly keen for water-in-oil (W/O) emulsions because of the limited range of suitable Pickering stabilizers available. We demonstrate for the first time that W/O emulsions can be stabilized by using crystals from naturally occurring polyphenols (curcumin and quercetin particles). These particles were assessed based on their size, microstructure, contact angle, interfacial tension, and ζ-potential measurements in an attempt to predict the way that they act as Pickering stabilizers. Static light-scattering results and microstructural analysis at various length scales [optical microscopy, confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM)] confirmed that the quercetin particles has a nearly perfect crystalline rod shape with a high aspect ratio; that is, the ratio of length to diameter (L/D) was ca. 2.5:1–7:1. On the other hand, the curcumin…

Although metallic biomaterials find numerous biomedical applications, their inherent low bioactivity and poor osteointegration had been a great challenge for decades. Surface modification via silanization can serve as an attractive method for improving the aforementioned properties of such substrates. However, its effect on protein adsorption/conformation and subsequent cell adhesion and spreading has rarely been investigated. This work reports the in-depth study of the effect of Ti6Al4V surface functionalization on protein adsorption and cell behavior. We prepared self-assembled monolayers (SAMs) of five different surfaces (amine, octyl, mixed [1:1 ratio of amine:octyl], hybrid, and COOH). Synthesized surfaces were characterized by Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy, contact angle goniometry, profilometry, and field emission scanning electron microscopy (FESEM). Quantification of adsorbed mass of bovine serum albumin (BSA) and fibronectin (FN) was determined on different surfaces along with secondary structure analysis. The adsorbed…

In this work, we studied the swelling behavior and adsorption behavior of zwitterionic copolymer hydrogels, which were prepared via the free radical copolymerization of sulfobetaine methacrylate (SBMA) and other monomers including sodium p-styrenesulfonate (NaSS), acrylic acid, N-isopropylacrylamide, and 2-(dimethylamino) ethyl methacrylate. The PSBMA hydrogel showed increased swelling ratio with the increase of ionic strength at the same temperature, and the swelling process reflected endothermicity. Interestingly, the PSBMA-NaSS hydrogels collapsed when the ionic strength increased because the ions can weaken the repulsive interaction of the anionic groups of PNaSS. In addition, the PSBMA-NaSS showed high adsorption of methylene blue (760 mg/g). The zwitterionic hydrogels have potential to be used as an adsorbent in the field of wastewater treatment.

The widespread occurrence of zwitterionic compounds in nature has incited their frequent use in designing biomimetic materials. Therefore, zwitterionic polymers are a thriving field. A particular interest for this particular polymer class has currently focused on their use in establishing neutral, low-fouling surfaces. After highlighting strategies to prepare model zwitterionic surfaces as well as those that are more suitable for practical purposes relying strongly on radical polymerization methods, we present recent efforts to diversify the structure of the hitherto quite limited variety of zwitterionic monomers and of the derived polymers. We identify key structural variables, consider their influence on essential properties such as overall hydrophilicity and long-term stability, and discuss promising targets for the synthesis of new variants.

A droplet impacting on a superhydrophobic surface exhibits complete bouncing. The impacting process usually consists of spreading and retracting stages, during which the droplet contacts the underlying substrate. Recent research has been devoted to reducing the contact time using textured surfaces with different morphologies or flexibilities. Here, we design submillimeter superhydrophobic ridges and show that impacting droplets bounce off the surface immediately after capillary emptying in a petal-like shape at a certain Weber number range. The absence of a horizontal retraction process in two directions leads to ∼70% reduction in contact time. We demonstrate that the petal bouncing is attributed to the synergistic cooperation of the hierarchical structures and anisotropic property, which endows effective energy storage and release. When touching the bottom of the grooves, obvious flying wings appear along the ridges with a velocity component in the vertical direction, which help the energy releasing process in achieving fast droplet detachment. At higher Weber numbers, the…

A methodology for determining the micropore, mesopore, and external surface areas of hierarchical microporous/mesoporous materials from N 2 adsorption isotherms at 77 K is described. For FAU-Y zeolites, the microporous surface area calculated using the Rouquerol criterion and the Brunauer–Emmett–Teller (BET) equation is in accord with the geometrical surface determined by the chord length distribution method. Therefore, BET surface area ( S BET ) is the well representative of micropore surface areas of microporous materials and of total surface area of microporous/mesoporous materials. Mechanical mixtures of mesoporous MCM-41 and microporous FAU-Y powders of known surface areas were used to calculate the respective surface areas by weighted linear combination and the results were compared to the values obtained by the t -plot method. The first slope of the t -plot determined the mesopore and external surface areas ( S mes+ext ). The linear fit of the first slope is in general in the range 0.01 < p / p 0 < 0.17 and contains the volumes and relative pressures at which all micropores…

Nonspecific adsorption of biomolecules to solid surfaces, a process called biofouling, is a major concern in many biomedical applications. Great effort has been made in the development of antifouling polymer coatings that are capable of repelling the nonspecific adsorption of proteins, cells, and micro-organisms. In this respect, we herein contribute to understanding the factors that determine which polymer brush results in the best antifouling coating. To this end, we compared five different monomers: two sulfobetaines, a carboxybetaine, a phosphocholine, and a hydroxyl acrylamide. The antifouling coatings were analyzed using our previously described bead-based method with flow cytometry as the read-out system. This method allows for the quick and automated analysis of thousands of beads per second, enabling fast analysis and good statistics. We report the first direct comparison made between a sulfobetaine with opposite charges separated by two and three methylene groups and a carboxybetaine bearing two separating methylene groups. It was concluded that both the distance between…

Many surfaces reversibly change their structure and interfacial energy upon being in contact with a liquid. Such surfaces adapt to a specific liquid. We propose the first order kinetic model to describe dynamic contact angles of such adaptive surfaces. The model is general and does not refer to a particular adaptation process. The aim of the proposed model is to provide a quantitative description of adaptive wetting and to link changes in contact angles to microscopic adaptation processes. By introducing exponentially relaxing interfacial energies and applying Young's equation locally, we predict a change of advancing and receding contact angles depending on the velocity of the contact line. Even for perfectly homogeneous and smooth surfaces, a dynamic contact angle hysteresis is obtained. As possible adaptations, we discuss changes and reconstruction of polymer surfaces or monolayers, diffusion and swelling, adsorption of surfactants, replacement of contaminants, reorientation of liquid molecules, or formation of an electric double layer.

Lightweight and compatible metal–organic framework (MOF)-derived carbon-based composites are widely used in electromagnetic (EM) absorption. Their combination with laminated TiO 2 -C (derived from Ti 3 C 2 T x ) is expected to further strengthen the EM attenuation ability. Herein, novel laminated Co/TiO 2 -C hybrids were derived from Ti 3 C 2 T x /Co-MOF using heat treatment. Compared with pristine MOF-derived carbon-based composites, the EM absorption ability of Co/TiO 2 -C was improved by multiple reflections between multilayered microstructures and the improved polarization loss (due to the heterogeneous interfaces, residual defects, and dipole polarization) and the strengthened conductivity loss caused by the carbon layers. Specifically, for the Co/TiO 2 -C hybrids at thicknesses of 3.0 and 2.0 mm, the optimal reflection loss (RL) was −41.1 dB at 9.0 GHz and −31.0 dB at 13.9 GHz, with effective bandwidths (RL ≤ −10 dB) of 3.04 and 4.04 GHz, respectively. This study will underline the preparation of carbon-based absorbing materials starting from MXene/MOF hybrids.

Synthetic hectorite clay Laponite RD/XLG is composed of disk-shaped nanoparticles that acquire dissimilar charges when suspended in an aqueous medium. Owing to their property to spontaneously self-assemble, Laponite is used as a rheology modifier in a variety of commercial water-based products. In particular, an aqueous dispersion of Laponite undergoes a liquid-to-solid transition at about 1 vol % concentration. The evolution of the physical properties as the dispersion transforms to the solid state is reminiscent of physical aging in molecular as well as colloidal glasses. The corresponding soft glassy dynamics of an aqueous Laponite dispersion, including the rheological behavior, has been extensively studied in the literature. In this feature article, we take an overview of recent advances in understanding soft glassy dynamics and various efforts taken to understand the peculiar rheological behavior. Furthermore, the continuously developing microstructure that is responsible for the eventual formation of a soft solid state that supports its own weight against gravity has also been…

A pH- and ultrasound dual-responsive drug release pattern was successfully achieved using mesoporous silica nanoparticles (MSNs) coated with polydopamine (PDA). In this paper, the PDA shell on the MSN surface was obtained through oxidative self-polymerization under the alkaline condition. The morphology and structure of this composite nanoparticle were fully characterized by a series of analyses, such as infrared (IR), transmission electron microscopy, and thermogravimetric analysis. Doxorubicin hydrochloride (DOX)-loaded composite nanoparticles were used to study the performances of responsive drug storage/release behavior, and this kind of hybrid material displayed an apparent pH response in DOX releasing under the acidic condition. Beyond that, upon high-intensity focused ultrasound exposure, loaded DOX in composite nanoparticles was successfully triggered to release from pores because of the ultrasonic cavitation effect, and the DOX-releasing pattern could be optimized into a unique pulsatile fashion by switching the on/off status. From the…

Advances in stem cell technology and regenerative medicine have underscored the need for effective banking of living cells. Cryopreservation, using very low temperatures to achieve suspended animation, is widely used to store or bank cells for later use. This process requires the use of cryoprotective agents (CPAs) to protect cells against damage caused by the cooling and warming process. However, current popular CPAs like DMSO can be toxic to cells and must be thoroughly removed from cells before they can be used for research or clinical applications. Trehalose, a nontoxic sugar found in organisms capable of withstanding extreme cold or desiccation, has been explored as an alternative CPA. The disaccharide must be present on both sides of the cellular membrane to provide cryo-protection. However, trehalose is not synthesized by mammalian cells nor has the capability to diffuse through their plasma membranes. Therefore, it is crucial to achieve intracellular delivery of trehalose for utilizing the full potential of the sugar for cell banking. In this review, various methods that…

Methodology to combine nanotechnology and these organization processes has been proposed as a novel concept of nanoarchitectonics, which can fabricate functional materials with nanolevel units. As an instant nanoarchitectonics approach, confining systems within a two-dimensional plane to drastically reduce translational motion freedom can be regarded as one of the rational approaches. Supramolecular chemistry and nanofabrication and their related functions at the air-water interface with the concept of nanoarchitectonics would lead to the creation of a novel methodology of Langmuir nanoarchitectonics. In this feature article, we briefly summarize research efforts related to Langmuir nanoarchitectonics including the basics for anomalies in molecular interactions such as highly enhanced molecular recognition capabilities. It is also extended to frontiers including the fabrication of supramolecular receptors and two-dimensional patterns with subnanometer-scale structural regulation, manual control of molecular machines and receptors by hand-motion-like macroscopic actions, and the…

Bile salts (BSs) are naturally occurring rigid surfactants with a steroidal skeleton and specific self-assembly and interface behaviors. Using bile salts as precursors, derivatives can be synthesized to obtain molecules with specific functionalities and amphiphilic structure. Modifications on single molecules are normally performed by substituting the least-hindered hydroxyl group on carbon C-3 of the steroidal A ring or at the end of the lateral chain. This leads to monosteroidal rigid building blocks that are often able to self-organize into 1D structures such as tubules, twisted ribbons, and fibrils with helical supramolecular packing. Tubular aggregates are of particular interest, and they are characterized by cross-section inner diameters spanning a wide range of values (3-500 nm). They can form through appealing pH- or temperature-responsive aggregation and in mixtures of bile salt derivatives to provide mixed tubules with tunable charge and size. Other derivatives can be prepared by covalently linking two or more bile salt molecules to provide complex systems such as…

Patients with diabetic wounds have deficient local and systemic cellular immunity. Herein, a new silver nanoparticle-containing hydrogel with antifouling properties was developed for enhancing the immune response in diabetic wound healing. The antifouling property was obtained by adjusting the composition of cationic chitosan and anionic dextran to approach zero charge. Furthermore, this hybrid hydrogel showed long-lasting and broad-spectrum antibacterial activity. Rapid wound contraction was observed after the treatment with the hydrogel, which suggested its superior healing activity to promote fibroblast migration, granulation tissue formation, and angiogenesis. The upregulation of CD68+ and CD3+ expression levels demonstrated that the hydrogel could trigger immune responses in the treatment of wound healing. These results show that this antifouling hybrid hydrogel as a wound dressing provided a promising strategy for the treatment of diabetic ulcers.

In this study, composite photocatalysts were produced from NiTiO 3 and N 2 -rich precursors (dicyandiamide, melamine, urea, and thiourea) under N 2 flow conditions. The goal of the study was to investigate the interaction between NiTiO 3 and the synthesized g-C 3 N 4 . The properties of the g-C 3 N 4 /NiTiO 3 (CNT) composites were different depending on the starting materials. Dicyandiamide and thiourea created strong connections with NiTiO 3 and resulted in the generation of Ti–N and Ti–O–S bonds. Urea and melamine, however, had difficulty forming g-C 3 N 4 structures or interconnections with NiTiO 3 . The Ti–N and Ti–O–S bridges in the composite photocatalysts led to increased photocatalytic activity as well as inhibition of the recombination rate. Additionally, the band diagrams of g-C 3 N 4 prepared from dicyandiamide and thiourea exhibited positions suitable for the Z-scheme charge-transfer model with NiTiO 3, implying that the composite photocatalysts were applicable for photocatalytic degradation of organic contaminants under the visible-light irradiation. Higher reaction…

Columnar phases formed by the stacking of disclike molecules with an intimate π-π overlap forms a 1D pathway for the anisotropic charge migration along the columns. Columnar phases have great potential in organic electronic devices to be utilized as active semiconducting layers in comparison to organic single crystals or amorphous polymers in terms of processability, ease of handling, and high charge carrier mobility. Intelligent molecular engineering of perylene and its derivatives provided access to tune the physical properties and self-assembly behavior. The columnar phase formed by perylene derivatives has great potential in the fabrication of organic electronic devices. There are several positions on the perylene molecule, which can be functionalized to tune its self-assembly, as well as optoelectronic properties. Thus, many liquid-crystalline molecules stabilizing the columnar phase, which are based on perylene tetraesters, perylene diester imides, and perylene bisimides, have been synthesized over the years. Their longitudinal and laterally extended derivatives,…

Polydopamine (PDA)-based surface modification has been used in a variety of fields. However, a vague impression on the stability of PDA still exists due to a lack of systematic studies. To ascertain the issue and make better use of this surface modification method, a technique of surface plasmon resonance imaging (SPRi) was exploited to study the stability of PDA coated on gold surface. The results showed that PDA-coating stability was largely dependent on the pH of aqueous solutions, giving detachment ratios up to 66% and 80% at pH 1.0 and pH 14.0, respectively. However, increasing the ionic strength of aqueous solutions could reduce the detachment of PDA in strong acid and strong alkali conditions. Besides, organic solvents also made a difference on the PDA-coating stability. Among the tested 10 kinds of organic solvents, including n-hexane, toluene, ethyl ether, tetrahydrofuran, ethyl acetate, isopropanol, acetone, acetonitrile, dimethylformamide (DMF), and dimethyl sulfoxide (DMSO), DMSO caused the most serious detachment of PDA, up to 56%, followed by DMF with a detachment…

The emulsification properties of carboxymethyl chitosan (CMChi) and hydrophobically modified carboxymethyl chitosan (h-CMChi) were studied as a function of pH and dodecane/water ratio. The pH was varied between 6-10, and the oil/water ratio between 0.1-2.0. In CMChi solution, the emulsion stability increased as the pH was lowered from 10 to 7, and the phase inversion was shifted from oil/water ratio 1.0 to 1.8, respectively. The system behaved differently in pH 6 due to the aggregation of CMChi and the formation of nanoparticles (∼200-300 nm). No phase inversion was observed and the maximum amount of emulsified oil was reached at oil/water ratio 1.2. The h-CMChi showed similar behavior as a function of pH but, due to hydrophobic modification, the phase inversion was shifted to higher values in pH 7-10. In pH 6, the behavior was similar, but the maximum amount of emulsified oil was higher compared to CMChi. The amount of adsorbed particles correlated with the emulsified amount of oil. Reversible emulsification of dodecane was demonstrated by pH adjustment using CMChi and h-CMChi…

In this study, the influence of the chitosan immobilization method on the properties of final hybrid materials was performed. Chitosan was immobilized on the surface of mesoporous (ChS2) and fumed silica (ChS3) by physical adsorption and the sol–gel method (ChS1). It was found that physical immobilization of chitosan allows to obtain hybrid composites (ChS) with a homogeneous distribution of polymer on the surface, relatively wide pores, and specific surface area of about 170 m 2 /g, pH PZC = 5.7 for ChS3 and 356 m 2 /g and pH PZC = 6.0 for ChS2. The microporous chitosan–silica material with a specific surface area of 600 m 2 /g and a more negatively charged surface (pH PZC = 4.2) was obtained by the sol–gel reaction. The mechanisms of azo dye adsorption were studied, and the correlation with the composite structure was distinguished. The generalized Langmuir equation and its special cases, that is, Langmuir–Freundlich and Langmuir equations, were applied for the analysis of adsorption isotherm data. The adsorption study showed that physically adsorbed chitosan (ChS1 and ChS2) on a…

The structure, phase behavior, and properties of cellular membranes are derived from their composition, which includes phospholipids, sphingolipids, sterols, and proteins with various levels of glycosylation. Because of the intricate nature of cellular membranes, a plethora of in vitro studies have been carried out with model membrane systems that capture particular properties such as fluidity, permeability, and protein binding but vastly simplify the membrane composition in order to focus in detail on a specialized property or function. Supported lipid bilayers (SLB) are widely used as archetypes for cellular membranes, and this instructional review primarily focuses on the preparation and characterization of SLB systems formed by Langmuir deposition methods. Typical characterization methods, which take advantage of the planar orientation of SLBs, are illustrated, and references that go into more depth are included. This invited instructional review is written so that nonexperts can quickly gain in-depth knowledge regarding the preparation and characterization of SLBs. In addition,…

The foreign body response (FBR) to implantable materials can negatively impact performance of medical devices such as the cochlear implant. Engineering surfaces that resist the FBR could lead to enhanced functionality including potentially improving outcomes for cochlear implant recipients through reduction in fibrosis. In this work, we coat poly(dimethylsiloxane) (PDMS) surfaces with two zwitterionic polymers, poly(sulfobetaine methacrylate) (pSBMA) and poly(carboxybetaine methacrylate) (pCBMA), using a simultaneous photografting/photo-cross-linking process to produce a robust grafted zwitterionic hydrogel. reduce nonspecific protein adsorption, the first step of the FBR. The coating process uses benzophenone, a photografting agent and type II photoinitiator, to covalently link the cross-linked zwitterionic thin film to the PDMS surface. As the concentration of benzophenone on the surface increases, the adhesive strength of the zwitterionic thin films to PDMS surfaces increases as determined by shear adhesion. Additionally, with increased concentration of the adsorbed benzophenone,…

The structural memory effect of layered double hydroxides (LDHs) is one of the important reasons for their extensive use in environmental remediation. In this study, humic acid (HA) was extracted from black soil and sediments and characterized to determine their structures. The regeneration mechanisms of calcinated LDHs (CLDHs) including different divalent metals (Mg-CLDH and Zn-CLDH) in deionized water and different HA solutions were carefully elucidated, and the reasons for the behavior differences in the two materials were explained. The presence of the HAs significantly increased the dissolution rate of Mg 2+ ions from Mg-CLDHs and subsequent regeneration of Mg-LDH. Because of the diverse functional groups in the HAs, these groups were complexed with metallic ions such as Mg 2+ on the surface of Mg-CLDH in the beginning. During the process, the HAs adsorbed the regenerated LDHs on the surfaces. Therefore, the crystallinity, morphology, and specific surface area of the regenerated Mg-LDH significantly changed, especially in the presence of high concentrations of HA. In the case…

The adsorption of protein layers at oil-water interfaces is critical to the formation and stability of various emulsions in, for example, technical applications as well as in biological lipid storage. Effects of ionic strength, pH, temperature, and pretreatments of the proteins are well-known. However, the oil phase has been regarded as exchangeable and its role in protein adsorption has been widely ignored. Herein, the influence of systematically selected oil interfaces of high purity on the formation and properties of β-lactoglobulin (β-lg) adsorption layers was evaluated. Droplet profile tensiometry and interfacial rheometry were employed to determine the adsorption kinetics and dilatational and interfacial shear moduli. We show that depending on the molecular size, flexibility, hydrophobicity, polarity, and polarizability of the oils, globular proteins adsorb distinctively. Stronger interactions of polar oils with the hydrophilic exterior of the native β-lg lead to decelerated protein unfolding. This results in lower surface pressures and slower formation of viscoelastic…

Numerous studies have focused on the remarkable adhesive properties of polydopamine, which can bind to substrates with a wide range of surface energies, even under aqueous conditions. This behavior suggests that polydopamine may be an attractive option as a surface treatment in structural bonding applications, where good bond durability is required. Here, we assessed polydopamine as a surface treatment for bonding aluminum plates with an epoxy resin. A model epoxy adhesive consisting of diglycidyl ether of bisphenol A (DGEBA) and Jeffamine D230 polyetheramine was employed, and lap shear measurements (ASTM D1002 10) were made (i) under dry conditions to examine initial bond strength and (ii) after exposure to hot/wet (63 °C in water for 14 days) conditions to assess bond durability. Surprisingly, our results showed that polydopamine alone as a surface treatment provided no benefit beyond that obtained by exposing the substrates to an alkaline solution of tris buffer used for the deposition of polydopamine. This implies that polydopamine has a potential Achilles' heel, namely, the…

Zn 2+ -passivated carbon dots (named Z-CDs) were synthesized from zinc gluconate for the first time through a one-step pyrolysis treatment. The mechanism of Zn 2+ -enhanced fluorescence was carefully investigated, and a new strategy to passivate the surfaces of CDs by Zn 2+ was proposed. Inspired by the complexation reaction between Zn 2+ and ethylenediaminetetraacetic acid (EDTA), a reversible “off–on” fluorescent nanosensor for the detection of EDTA and Zn 2+ was constructed based on the depassivation and repassivation of Z-CDs, with a limit of detection as low as 3.2 × 10 –7 M and 5.1 × 10 –7 M, respectively. The proposed Z-CD-based nanosensor had been further utilized for EDTA and Zn 2+ monitoring in tap water with excellent recovery. To the best of our knowledge, this was the first report of a fluorescence-based sensor of EDTA and a turn-on sensor of Zn 2+ based on CDs with reversible detection capability. Also, benefiting from the low toxicity of zinc, Z-CDs were applied for multicolor bioimaging and in vitro detection in cells.

The spreading and rebound patterns of low-viscous droplets upon impacting spherical solid surfaces are investigated numerically. The studied cases consider a droplet impinging onto hydrophobic and superhydrophobic surfaces with various parameters varied throughout the study, and their effects on the postimpingement behavior are discussed. These parameters include impact Weber number (through varying the surface tension and impingement velocity), the size ratio of the droplet to the solid surface, and the surface contact angle. According to the findings, the maximum spreading diameter increases with the impact velocity, with an increase of the sphere diameter, with a lower surface wettability, and with a lower surface tension. Typical outcomes of the impact include (1) complete rebound, (2) splash, and (3) a final deposition stage after a series of spreading and recoiling phases. Finally, a novel, practical model is proposed, which can reasonably predict the maximum deformation of low Reynolds number impact of droplets onto hydrophobic or superhydrophobic spherical solid surfaces.

Antimicrobial peptide magainin 2 forms pores in lipid bilayers, a property that is considered the main cause of its bactericidal activity. Recent data suggest that tension or stretching of the inner monolayer plays an important role in magainin 2-induced pore formation in lipid bilayers. Here, to elucidate the mechanism of magainin 2-induced pore formation, we investigated the effect on pore formation of asymmetric lipid distribution in two monolayers. First, we developed a method to prepare giant unilamellar vesicles (GUVs) composed of dioleoylphosphatidylglycerol (DOPG), dioleoylphosphatidylcholine (DOPC), and lyso-PC (LPC) in the inner monolayer and of DOPG/DOPC in the outer monolayer. We consider that in these GUVs, the lipid packing in the inner monolayer was larger than that in the outer monolayer. Next, we investigated the interaction of magainin 2 with these GUVs with an asymmetric distribution of LPC using the single GUV method, and found that the rate constant of magainin 2-induced pore formation, k p, decreased with increasing LPC concentration in the inner monolayer. We…

Oxygen vacancies have been demonstrated to enhance the interfacial charge separation in TiO 2 -based photocatalysts. In this report, we explored a facile route to synthesize hierarchical nanotubular anatase/rutile/TiO 2 (B) nanostructures with high surface area and defective electronic structure. The formation of oxygen vacancies in the heterophase junction was analyzed by UV–vis absorption spectra, electron spin resonance, and X-ray photoelectron spectroscopy. The enhanced interfacial charge separation and transportation ensured the excellent photoactivity of oxygen-deficient junctions for the photocatalytic production of hydrogen. As a result, the defective anatase/rutile/TiO 2 (B) junction showed a high hydrogen evolution rate of 2.79 mmol/h, which was 19 times higher than blank TiO 2 nanotubes. The results demonstrate that defect modulation is a powerful tool to enhance the catalytic performances of TiO 2 -based photocatalysts.

Two-dimensional heterostructures, such as Fe 2 O 3 /MXene nanoparticles, can be attractive anode materials for lithium-ion batteries (LIBs) due to the synergy between high lithium-storage capacity of Fe 2 O 3 and stable cyclability and high conductivity provided by MXene. Here, we improved the storage performance of Ti 3 C 2 T x (MXene)/Fe 2 O 3 nanocomposite by confining Fe 2 O 3 nanoparticles into Ti 3 C 2 T x nanosheets with different mixing ratios using a facile and scalable dry ball-milling process. Composites of Ti 3 C 2 T x -25 wt % Fe 2 O 3 and Ti 3 C 2 T x -50 wt % Fe 2 O 3 synthesized by ball-milling resulted in uniform distribution of Fe 2 O 3 nanoparticles on Ti 3 C 2 T x nanosheets with minimum oxidation of MXene as compared to composites prepared by hydrothermal or wet sonication. Moreover, the composites demonstrated minimum restacking of the nanosheets and higher specific surface area. Among all studied composites, the Ti 3 C 2 T x -50 wt % Fe 2 O 3 showed the highest reversible specific capacity of ∼270 mAh g –1 at 1C (∼203 mAh g –1 based on the composite) and rate…

Application of biocatalytic membrane is promising in food, pharmaceutical, and water treatment industries, whereas enzyme immobilization is the key step of biocatalytic membrane preparation. Thus, how to minimize the negative effect of immobilization on enzyme performance is required to answer. In this work, we proposed a platform for biocatalytic membrane preparation and immobilization mechanism investigation based on polydopamine (PDA) coating, which was demonstrated by immobilizing five commonly used enzymes (laccase, glucose oxidase, lipase, pepsin, and dextranase) on three commercially available membranes via three immobilization mechanisms (electrostatic attraction, covalent bonding, and hydrophobic adsorption), respectively. By examining the enzyme loading, activity, and kinetics under different immobilization mechanisms, we found that except for dextranase, enzyme immobilization via electrostatic attraction retained the most activity, whereas covalent bonding and hydrophobic adsorption were detrimental to enzyme conformation. Enzyme immobilization via covalent bonding…

A pH-cycle method based on preparing an alkaline solution of zein followed by neutralization with an acid can be used to prepare zein nanoparticles. In the present work, partial alkaline hydrolysis of propylene glycol alginate (PGA) to a lower pH was studied to prepare binary zein-PGA nanocomplexes and ternary complexes with additional sodium caseinate (NaCas). 0.5% or more PGA was sufficient to reduce the pH to 7.5 or lower, eliminating the need for titration, and resulted in simultaneous nanocomplex formation. The addition of NaCas into alkaline zein-PGA solution resulted in smaller complexes with all biopolymers, whereas adsorption on binary zein-PGA complexes was observed when NaCas was added into the neutral zein-PGA dispersions. The formation of nanocomplexes involved with hydrophobic and electrostatic attractions and hydrogen bonds and was further affected by the amount of NaCas. The ternary nanocomplexes with equal masses of zein and NaCas had an excellent capacity to prepare gel-like Pickering emulsions with as much as 80% v/v oil with characteristics suitable for texture…

A series of microencapsulated phase-change materials (MEPCMs) based on paraffin core and calcium carbonate (CaCO 3 ) shell were synthesized, and the effect of emulsifier type and pH value on morphology, structure, and properties of paraffin@CaCO 3 MEPCMs were investigated. The results showed that CaCO 3 shell was formed in vaterite and calcite crystalline phase when emulsifier was sodium dodecyl benzene sulfonate and styrene-maleic anhydride (SMA), respectively. When sodium dodecyl sulfate was used as an emulsifier, both vaterite and calcite CaCO 3 were formed. The forming mechanism of emulsifier type on CaCO 3 crystalline phase was studied. Furthermore, phase-change enthalpy and leakage rate of MEPCMs were related with the type of emulsifier and the pH value of the emulsion. With optimum condition of SMA as emulsifier and pH value of 7, paraffin@CaCO 3 MEPCMs had an encapsulation ratio at 56.6% and leakage rate at 2.88%, illustrating its considerable heat storage capability and leakage-prevention property. The 50 heating–cooling cycles test indicated that the MEPCMs owned excellent…

Zwitterionic materials are the latest generation of materials for nonfouling interfaces and membranes. They outperform poly(ethylene glycol) derivatives because they form tighter bonds with water molecules and can trap more water molecules. This feature article summarizes our laboratory's fundamental developments related to the functionalization of interfaces and membranes using zwitterionic materials. Our molecular designs of zwitterionic polymers and copolymers, sulfobetaine-based, carboxybetaine-based, or phosphobetaine-based, are first reviewed. Then, the strategies used to functionalize surfaces/membranes by coating, grafting onto, grafting from, or in situ modification are examined and discussed, and the third part of this article shifts the focus to key applications of zwitterionic materials. Finally, some potential future directions for molecular designs, functionalization processes, and applications are presented.