Langmuir最新文献

Compared to lipids, block copolymer vesicles are potentially robust nanocontainers for enzymes owing to their enhanced chemical stability, particularly in challenging environments. Herein we report that cis-diol-functional diblock copolymer vesicles can be chemically adsorbed onto a hydrophilic aldehyde-functional polymer brush via acetal bond formation under mild conditions (pH 5.5, 20 °C). Quartz crystal microbalance studies indicated an adsorbed amount, Γ, of 158 mg m^-2 for vesicle adsorption onto such brushes, whereas negligible adsorption (Γ = 0.1 mg m^-2) was observed for a control experiment conducted using a cis-diol-functionalized brush. Scanning electron microscopy and ellipsometry studies indicated a mean surface coverage of around 30% at the brush surface, which suggests reasonably efficient chemical adsorption. Importantly, such vesicles can be conveniently loaded with a model enzyme (horseradish peroxidase, HRP) using an aqueous polymerization-induced self-assembly formulation. Moreover, the immobilized vesicles remained permeable toward small molecules while retaining their enzyme payload. The enzymatic activity of such HRP-loaded vesicles was demonstrated using a well-established colorimetric assay. In principle, this efficient vesicle-on-brush strategy can be applied to a wide range of enzymes and functional proteins for the design of next-generation immobilized nanoreactors for enzyme-mediated catalysis.

A novel polymeric ionic liquid (PDBA-IL-NH₂) using imidazolium ionic liquids with short alkyl chains as monomers and two control ionic liquids (PDBA-IL-OH and PIL-NH₂) were synthesized. Their inhibition properties and mechanisms were explored via surface analysis, weight loss tests, electrochemical studies, and adsorption isotherm analysis. The corrosion inhibition efficiency (CIE) of PDBA-IL-NH₂ gradually increased with increasing concentration, and the largest efficiency was 94.67% at 100 ppm. At the same concentration (50 ppm), the corrosion inhibition abilities of inhibitors were in the order of PDBA-IL-NH₂ > PDBA-IL-OH > PIL-NH₂ > IL-NH₂. Based on the experimental investigation, the synergistic effect of electrostatic interaction, protonation, and electron donor-acceptor interaction facilitated the intensive entanglement and coverage of PDBA-IL-NH₂ with the reticulated form on the metal, and the generated densest films protected the metal from the corrosive media. Ultimately, the theoretical results of molecular dynamics simulations and quantum chemical study were in high agreement with the experimental data, which confirmed the proposed inhibition mechanisms on the microscopic scale. This study contributed valuable perspectives to the design of efficient and ecofriendly corrosion inhibitors.

The emulsifying mechanism of supramolecular stereoisomeric sugar fatty acyl molecular gelators was evaluated. In-house-synthesized mannitol dioctanoate (M8) and sorbitol dioctanoate (S8) were tested. The stereoisomeric difference between the sugar groups significantly affected the gelation and emulsifying properties of the gelators. M8 and S8 formed oleogels at 2 and 3.5% (w/v) and emulsified water up to 30 and 60% (v/v), respectively. Microscopy showed that the gelator fibers are at the W/O interfaces, demonstrating a solid particle or network mode of stabilization. The long fibers of M8 were unable to completely encompass the water droplets, resulting in poor emulsification. Small, hair-like fibers of S8 showed better emulsification. When sunflower wax (SFW, 1% w/v) was added as a coemulsifier, synergetic action between the wax and S8 improved the stability of emulsions. Such synergy was not seen between SFW and M8, henceforth emulsion stability was not improved. This study proved that a subtle stereoisomeric difference at the molecular level can greatly alter the supramolecular and emulsifying properties of sugar-fatty acyl compounds.

Lifshitz theory is widely used to calculate interfacial interaction energies and underpins established approaches to the interpretation of measurement data from experimental methods including the surface forces apparatus and the atomic force microscope. However, a significant limitation of Lifshitz theory is that it uses the bulk dielectric properties of the medium to predict the work of adhesion. Here, we demonstrate that a different approach, in which the interactions between molecules at surfaces and in the medium are described by a set of surface site interaction points (SSIPs), yields interaction free energies that are correlated better with experimentally determined values. The work of adhesion W(Lifshitz) between hydrocarbon surfaces was calculated in 260 liquids using Lifshitz theory and compared with interaction free energies ΔΔG calculated using the SSIP model. The predictions of these models diverge in significant ways. In particular, ΔΔG values for hydrocarbon surfaces are typically small and vary little, but in contrast, W(Lifshitz) values span 4 orders of magnitude. Moreover, the SSIP model yields significantly different ΔΔG values in some liquids for which Lifshitz theory predicts similar values of W(Lifshitz). These divergent predictions were tested using atomic force microscopy. Experimentally determined works of adhesion were closer to the values predicted using the SSIP model than Lifshitz theory. In mixtures of methanol and benzyl alcohol, even greater differences were found in the interaction energies calculated using the two models: the value of ΔΔG calculated using the SSIP model declines smoothly as the benzyl alcohol concentration increases, and values are well correlated with experimental data; however, W(Lifshitz) decreases to a minimum and then increases, reaching a larger value for benzyl alcohol than for methanol. We conclude that the SSIP model provides more reliable estimates of the work of adhesion than Lifshitz theory.

DNA-templated nanofabrication presents an innovative approach to creating self-assembled nanoscale metal-semiconductor-based Schottky contacts, which can advance nanoelectronics. Herein, we report the successful fabrication of metal-semiconductor Schottky contacts using a DNA origami scaffold. The scaffold, consisting of DNA strands organized into a specific linear architecture, facilitates the competitive arrangement of Au and CdS nanorods, forming heterojunctions, and addresses previous limitations in low electrical conductance making DNA-templated electronics with semiconductor nanomaterials. Electroless gold plating extends the Au nanorods and makes the necessary electrical contacts. Tungsten electrical connection lines are further created by electron beam-induced deposition. Electrical characterization reveals nonlinear Schottky barrier behavior, with electrical conductance ranging from 0.5 × 10^-4 to 1.7 × 10^-4 S. The conductance of these DNA-templated junctions is several million times higher than with our prior Schottky contacts. Our research establishes an innovative self-assembly approach with applicable metal and semiconductor materials for making highly conductive nanoscale Schottky contacts, paving the way for the future development of DNA-based nanoscale electronics.

Ordered mesoporous silica is widely used in catalysis, adsorption, and biomedicine, among which SBA-15 (Santa Barbara Amorphous-15) is one of the most widely studied. However, the synthesis of SBA-15 often requires strong acid (hydrochloric acid or sulfuric acid), which will not only corrode industrial equipment but also pollute the environment with the wastewater containing strong acid and halogen (sulfur). Here, we demonstrate a green synthetic strategy for SBA-15 under weakly acidic conditions through an anionic assembly route. With the assistance of poly(acrylic acid) (PAA) and 3-aminopropyltrimethoxysilane (APMS), the pH value of the synthesis system can be increased to 4-5, which is a mild near-neutral condition. In addition, halogen-free synthesis using organic acids is also achieved. The powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and N₂ sorption characterizations show that the obtained SBA-15 has good texture properties, with a specific surface area of 430-500 m²/g and ordered 6-8 nm mesopores, which is similar to SBA-15 synthesized in traditional strong acid. This strategy provides a facile and environmentally friendly route for the large-scale production of ordered mesoporous materials.

With the wide application of lithium-ion batteries (LIBs) in different fields, safety accidents occur frequently. Therefore, it is necessary to monitor the thermal runaway gas for an early warning. In this article, the adsorption properties of the characteristic gases of LIBs thermal runaway gases are studied by density functional theory (DFT). The adsorption structure of TM (Co/Rh/Ir)-decorated HfS₂ (TM@HfS₂) is established, and its adsorption properties for C₂H₄, CH₄, and CO are studied. The adsorption energy, charge transfer, band, DOS, charge difference density, work function, and recovery time are discussed in detail. The results show that Ir@HfS₂ has the strongest adsorption performance for C₂H₄ and CO, so C₂H₄ and CO can be stably adsorbed on the surface of the Ir@HfS₂ monolayer. The adsorption energy of CH₄ on Co@HfS₂ is stronger than those of Rh@HfS₂ and Ir@HfS₂, but the adsorption energy is still very small. By applying biaxial strain to Co@HfS₂, we found that the adsorption energy increases with the increase in negative strain. This study provides a theoretical basis for the regulation of the adsorption properties of HfS₂ by different transition metals.

We have quantified and compared the hydration capacity (i.e., capability to incorporate water molecules) of the two surface-bound hydrophilic polymer chains, dextran (dex) and poly(ethylene glycol) (PEG), in the form of poly(l-lysine)-graft-dextran (PLL-g-dex) and poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG), respectively. The copolymers were attached to a negatively charged silica-titania surface through the electrostatic interaction between the PLL backbone and the surface in neutral aqueous media. While the molecular weights of PLL and PEG were fixed, that of dex and the grafting density of PEG or dex on the PLL were varied. The hydration capacity of the polymer chains was quantified through the combined experimental approach of optical waveguide lightmode spectroscopy (OWLS) and quartz crystal microbalance with dissipation monitoring (QCM-D) to yield a value for areal solvation (Ψ), i.e., mass of associated solvent molecules within the polymer chains per unit substrate area. For the two series of copolymers with comparable stretched chain lengths of hydrophilic polymers, namely, PLL(20)-g-PEG(5) and PLL(20)-g-dex(10), the Ψ values gradually increased as the initial grafting density on the PLL backbone increased or as g decreased. However, the rate of increase in Ψ was higher for PEG than dextran chains, which was attributed to higher stiffness of the dextran chains. More importantly, the number of water molecules per hydrophilic group was clearly higher for PEG chains. Given that the -CH₂CH₂O- units that make up the PEG chains form a cage-like structure with 2-3 water molecules, these "strongly bound" water molecules can account for the slightly more favorable behavior of PEG compared to dextran in both aqueous lubrication and antifouling behavior of the copolymers.