Langmuir最新文献

The shape and stability of a droplet in contact with a solid surface is affected by the chemical composition and topography of the solid, and crucially, by the droplet's size. During a variation in size, most often observed during evaporation, droplets on smooth patterned surfaces can undergo sudden shape and position changes. Such changes, called snaps, are prompted by the surface pattern and arise from fold and pitchfork bifurcations which respectively cause symmetric and asymmetric motions. Yet, which type of snap is likely to be observed is an open fundamental question that has relevance in the rational design of surfaces for managing droplets. Here we show that the likelihood of observing symmetric or asymmetric snaps depends on the distance between fold and pitchfork bifurcation points and on how this distance varies for droplets that grow or shrink in size on surfaces patterned with a smooth topography. Our results can help develop strategies to control droplets by exploiting smooth surface patterns but also have broader relevance in situations where different types of bifurcations compete in determining the stability of a system, for instance in snap-through instabilities observed in elastic media.

Urea oxidation reaction (UOR) is an attractive alternative anodic reaction to oxygen evolution reaction (OER) for its low thermodynamic potential (0.37 V vs RHE). A major challenge that prohibits its practical application is the six-electron transfer process during UOR, demanding enhancements in the catalytic activity. Herein, a Fe-doped Ni₃S₂ catalyst with a uniform flower-like structure is synthesized in situ on nickel foam via a simple one-step hydrothermal method. The electrochemical properties of Fe-Ni₃S₂ are significantly improved since a current density of 10 mA cm^-2 only requires a 1.33 V potential and remains stable for 60 h. The structural characterization demonstrates a strong interaction between Fe and Ni₃S₂. After Fe doping, the active site increases, which promotes the formation of NiOOH on the catalyst surface, thus speeding up the UOR process. These changes are beneficial to charge transfer and optimize the adsorption energy of the intermediates. In situ EIS further confirms that Fe promotes electron transfer during the UOR process, reduces the interface resistance between the catalyst and the electrolyte, and lowers the driving voltage.

Biofouling can cause severe infections, device malfunctions, and failures in diagnostics and therapeutics. Proteins such as bovine serum albumin (BSA) have recently been used as coatings to resist biofouling because they combine surface anchoring and antifouling properties. However, their antifouling effectiveness will significantly deteriorate in complex biofluids with high salinity, limiting their practical applications. In this work, we developed a zwitterion-conjugated protein with enhanced antifouling capability by grafting zwitterionic 2-methacryloyloxyethyl phosphorylcholine (MPC) onto BSA protein via a click reaction. This conjugated protein can easily anchor on various substrates, both inorganic and organic, and exhibits efficient and broad-spectrum fouling resistance to metabolites, proteins, and complex biofluids. Even in the complex fetal bovine serum with higher salinity, the BSA@MPC coating can also maintain 99% fouling resistance robustly, over 6-fold superior to native BSA-coated surfaces in antifouling capability. Direct surface forces measurement reveals that such outstanding antifouling properties of conjugated protein BSA@MPC could be attributed to the stable hydration layer on its surface and the steric repulsion from the antipolyelectrolyte behavior of zwitterionic MPC polymer in the high-salinity environment. Our findings advance the development of protein-based functional materials and provide valuable insights for designing novel antifouling surfaces for marine, food, and bioengineering applications.

Here, we report the in situ generation of Bi nanoparticles (BiNPs) into a nanoporous matrix by impregnation of bismuth chloride and subsequent reduction with sodium borohydride. The nanoporous matrix was created by acid activation of natural montmorillonite clay under controlled conditions with the aim that it may serve as a host for BiNPs. The characterization of stabilized BiNPs was done by using Fourier-transform infrared (FTIR), powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), and field emission scanning electron microscopy-energy dispersive X-ray (FESEM-EDX) techniques. The TEM study reveals that the BiNPs with an average particle size of 7.16 nm are well-distributed on the surface of the acid-activated montmorillonite clay. The synthesized BiNPs exhibited excellent catalytic activity for the degradation of 4-nitrophenol (4-NP) in aqueous medium with remarkable results. The degradation of 4-NP to 4-aminophenol (4-AP) at 25 °C, in the presence of sodium borohydride, brought about almost 100% conversion in 6 min with a rate constant of 0.20098 s^-1 that follows the pseudo-first-order kinetics.

Transition metal complexes have been widely used as catalysts or chromophores in artificial photosynthesis. Traditionally, they are employed in homogeneous settings. Despite their functional versatility and structural tunability, broad industrial applications of these catalysts are impeded by the limitations of homogeneous catalysis such as poor catalyst recyclability, solvent constraints (mostly organic solvents), and catalyst durability. Over the past few decades, researchers have developed various methods for molecular catalyst heterogenization to overcome these limitations. In this review, we summarize recent developments in heterogenization strategies, with a focus on describing methods employed in the heterogenization process and their effects on catalytic performances. Alongside the in-depth discussion of heterogenization strategies, this review aims to provide a concise overview of the key metrics associated with heterogenized systems. We hope this review will aid researchers who are new to this research field in gaining a better understanding.

Constructing alternating donor-acceptor (D-A) units within g-C₃N₄ represents an effective strategy for enhancing photocatalytic performance through improved charge carrier separation while concurrently addressing energy shortages and facilitating wastewater remediation. Here, a series of D-A-type conjugated photocatalysts (CNBTC-X) are prepared using g-C₃N₄ as an acceptor unit and different masses of 5-bromo-2-thiophenecarboxaldehyde (BTC) as a donor unit by a one-step thermal polymerization. CNBTC-50 presents higher photocatalytic properties for CO₂ reduction coupled with tetracycline (TC) removal than those of g-C₃N₄, CNBTC-10, CNBTC-30, and CNBTC-70. The introduction of the unique electron-donor-acceptor structure effectively drives the separation and transfer of photoinduced carriers while reducing the internal carrier transfer hindrance. Photocatalytic experiments reveal that the CNBTC-50 photocatalyst achieves up to 94.6% TC removal under visible light irradiation conditions. Compared with that of the pristine g-C₃N₄, the photocatalytic degradation reaction rate constant of CNBTC-50 is significantly increased by about 3.87 times. The study examines the influence of various reaction parameters on degradation activity, including catalyst concentration, pH, and TC concentration. Additionally, LC-MS is utilized to perform a comprehensive analysis of the intermediates and pathways involved in TC degradation. Furthermore, CNBTC-50 demonstrates remarkable photocatalytic CO₂ reduction activity, achieving rates of 20.83 μmol g^-1 h^-1 (CO) and 9.36 μmol g^-1 h^-1 (CH₄), which are 10.68 and 5.98 times more efficient than those of g-C₃N₄, respectively. This work aims to offer valuable guidance for the rational design of nonmetal D-A-structured catalysts and effectively integrates reaction systems to couple CO₂ reduction with antibiotic removal.

Film thickness is a well-known experimental parameter for controlling lattice strain in oxide films. However, due to environmental and resource conservation considerations, films need to be as thin as possible, increasing the need to find alternative factors for strain management. Herein, we present the importance of thermal energy as a factor for the formation of lattice strain in the oxide films, specifically focusing on the effects of laser fluence during pulsed laser deposition (PLD) on the in-plane lattice strain of vanadium dioxide (VO₂) thin films grown on titanium dioxide (TiO₂) (001). VO₂ thin films were deposited using a KrF excimer laser (λ = 248 nm) at laser fluences ranging from 0.88 to 1.70 J/cm². The film thickness ranged from 10-15 nm, below the critical thickness. Films grown at higher laser fluences exhibited smooth surfaces and completely strained in-plane lattices. In contrast, films grown at lower laser fluences displayed numerous small islands and relaxed in-plane lattice strain. The metal-insulator transition (MIT) temperature was lower for films grown at higher laser fluencies compared to those grown at lower laser fluences. It was also revealed that Ti-V interdiffusion occurs, forming a solid solution (V_1-xTi_xO₂) near the interface. These observations suggest that the thermal energy of the particles, influenced by laser fluence, is a critical factor in the formation of lattice strain in metal oxide films and also that laser fluence in PLD is an effective experimental parameter for strain management in oxide films. Our findings enhance the understanding of lattice strain formation in metal oxides and offer insights for establishing effective methods for controlling lattice strain in metal oxide films.

Infections and thrombosis remain unsolved problems for implanted cardiovascular devices, such as left ventricular assist devices. Hence, the development of surfaces with improved blood compatibility and antimicrobial properties is imperative to reduce complications after artificial heart implantation. In this work, we report a novel approach to fabricate multifunctional surfaces for left ventricular transplanted ventricular assist devices (LVADs) by immobilizing nitric oxide (NO) generation catalysts and heparin and reducing silver nanoparticles in situ. The general view, structure, and chemical compositions of the pure/modified surfaces were characterized using digital imaging, scanning electron microscope (SEM), atomic force microscope (AFM), water contact angle (WCA), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma (ICP). All of the results demonstrated that the AgNPs and heparin were successfully immobilized on the surface. The Cu ions and NO release experimental results showed that the immobilized copper ions could catalyze the production of NO from S-nitrosothiols within the biological system. Meanwhile, due to the synergistic anticoagulant effect of NO and surface-immobilized heparin, the fabricated modified surfaces exhibited antiplatelet adhesion activities and good hemocompatibility. Finally, the antimicrobial activity of the samples was evaluated by Escherichia coli and Staphylococcus aureus, and cytocompatibility was measured using human umbilical vein endothelial cells (HUVECs). The results demonstrated that silver nanoparticles (AgNPs) immobilized by surface reduction reaction did not cause any significant inhibition of cell proliferation while providing stable and effective antimicrobial properties. We envision that this simple surface modification strategy with bifunctional activities of antimicrobial and anticoagulant will find widespread use in clinically used indwelling left ventricular assist devices.

Electrochemical water splitting required efficient electrocatalysts to produce clean hydrogen fuel. Here, we adopted greenway coprecipitation (GC) method to synthesize conducting polymer (CP) nanotunnel network affixed with luminal-abluminal CoNi hydroxides (GC-CoNiCP), namely, GC-Co₁Ni₂CP, GC-Co_1.5Ni_1.5CP, and GC-Co₂Ni₁CP. The active catalyst, GC-Co₂Ni₁CP/GC, has low oxygen evolution reaction (OER) overpotential (307 mV) and a smaller Tafel slope (47 mV dec^-1) than IrO₂ (125 mV dec^-1). The electrochemical active surface area (EASA) normalized linear sweep voltammetry (LSV) curve exhibited outstanding intrinsic activity of GC-Co₂Ni₁CP, which required 285 mV to attain 10 mA cm^-2. At 1.54 V, the estimated turnover frequency (TOF) of GC-Co₂Ni₁CP/GC (0.017337 s^-1) was found to be 3-fold higher than that of IrO₂ (0.0014 s^-1). Furthermore, the GC-Co₂Ni₁CP/NF consumed a very low overpotential (281 mV) with a small Tafel slope of 121 mV dec^-1. The ultrastability of GC-Co₂Ni₁CP for industrial application was confirmed by durability at 10 and 100 mA cm^-2 for the OER (GC/NF-8 h, 2.0%/100 h, 2.2%) and overall water splitting (100 h, 3.8%), which implies that GC-Co₂Ni₁CP had adequate kinetics to address the elevated rates of water oxidation. The effect of pH and addition of tetramethylammonium cation (TMA⁺) reveal that GC-Co₂Ni₁CP follows the lattice oxygen mechanism (LOM). The solar-powered water electrolysis at 1.55 V supports the efficacy of GC-Co₂Ni₁CP in the solar-to-hydrogen conversion. The environmental impact studies and solar-driven water electrolysis proved that GC-CoNiCP has excellent greenness and efficiency, respectively.