Silica Surface Research Articles

Biotemplated Janus Magnetic Microrobots Based on Diatomite for Highly Efficient Detection of Salmonella.

Foodborne illnesses caused by Salmonella bacteria pose a significant threat to public health. It is still challenging to detect them effectively. Herein, biotemplated Janus disk-shaped magnetic microrobots (BJDMs) based on diatomite are developed for the highly efficient detection of Salmonella in milk. The BJDMs were loaded with aptamer, which can be magnetically actuated in the swarm to capture Salmonella in a linear range of 5.8 × 102 to 5.8 × 105 CFU/mL in 30 min, with a detection limit as low as 58 CFU/mL. In addition, the silica surface of BJDMs exhibited a large specific surface area to adsorb DNA from captured Salmonella, and the specificity was also confirmed via tests of a mixture of diverse foodborne bacteria. These diatomite-based microrobots hold the advantages of mass production and low cost and could also be extended toward the detection of other types of bacterial toxins via loading different probes. Therefore, this work offers a reliable strategy to construct robust platforms for rapid biological detection in practical applications of food safety.

Tetra-Amido Macrocyclic Ligand (TAML) at Silicon(IV): A Structurally Constrained, Water-Soluble Silicon Lewis Superacid.

Tetracoordinate silicon species are typically tetrahedral, weak Lewis acids, and often sensitive to moisture. In this study, we present a tetra-amido macrocyclic ligand (TAML)-substituted Si(IV), isolated as its bis(pyridine) adduct. Due to structural constraint toward anti van't-Hof/Le Bel geometry, this compound exhibits Lewis superacidity and effectively catalyzes the hydroboration of pyridine. Kinetic and computational analyses of the catalytic cycle reveal that TAML-Si(IV) acts as a hydride transfer agent, and the hydrido silicate key intermediate is isolated. Notably, the Lewis acid is highly soluble (5 g/L) and long-term stable in water. Unlike previously described silicon-H2O adducts, the bound water becomes substantially acidified, reaching the Bro̷nsted superacidity range. A comparison of water affinity versus pKa lowering confirms our previous theory of the strength and the effect of Lewis acids. Overall, the compound's unlimited water compatibility and its mechanistically understood catalytic efficiency mark significant progress in applying structural constraint strategies for p-block element-based catalysis, while the acidification touches critical aspects of zeolite and silica surface chemistry.

A stationary phase of tetraethylene glycol-modified silica for separation of phenolic acids

AbstractSilica, as a stationary phase, has low separation efficiency accompanied by overlapping, broadened, and tailed peaks, so it needs to be modified to improve its efficiency. This study aims to develop a silica-based stationary phase modified by tetraethylene glycol (TEG) to separate phenolic compounds. Silica was modified by a chemical bond between silanol groups on the silica surface and TEG through a 3-glycidyloxypropylmethoxysilane reaction. The modified silica was packed into a capillary column and used to separate simple phenolic compounds consisting of phenol, pyrocatechol, and pyrogallol. A sample of 0.2 µL was injected into the capillary liquid chromatography and the mobile phase employed was acetonitrile 98% with a flow rate of 3 μL min−1. Elution was also done isocratically in this process and detection was carried out at a wavelength of 254 nm. The mixture of simple phenolic compounds was successfully separated in less than 7 min. The asymmetry factor and resolution were 1.43–2.12 and 1.72–5.43 respectively. The number of the theoretical plates ranged from 213 to 7,857. Columns containing Si-TEG stationary phase also separate phenolic compounds, which consist of gallic acid, syringic acid, ferulic acid, and caffeic acid. A sample of 0.2 µL was injected into the capillary liquid chromatography and successfully separated the mixture in less than 12 min. The samples were eluted isocratically using a mixture of methanol and 50 mM phosphate buffer pH 2.5 (8:92) with a flow rate of 3 μL min−1. The phenolic acids compounds were detected at a wavelength of 280 nm. The chromatogram showed four separate peaks. The asymmetry factor and resolution were 1.53–1.63 and 1.14–1.74, respectively, but the number of the theoretical plates was low, ranging from 190 to 796.

Adsorption of Staphylococcus aureus biofilm associated compounds on silica probed with molecular dynamics simulations.

Staphylococcus aureus (S. aureus) is a potentially pathogenic bacterium that commonly colonizes surfaces through the formation of biofilms. Silica glass is a common material in the built environment, especially in laboratory and medical spaces. The chemical and physical mechanisms by which S. aureus initially adheres to surfaces are unclear. In this study, the adsorption of several S. aureus biofilm associated compounds on silica is probed using molecular dynamics simulations. Model compounds containing a phosphorylated backbone, N-acetylglucosamine (GlcNAc), or D-alanine (D-Ala) were simulated across a range of pH. GlcNAc adsorption is unfavorable and insensitive to pH. D-Ala adsorption is unfavorable across the range of tested pH. Phosphorylated backbone adsorption is unfavorable at low pH but favorable at high pH. Adsorbate titration and solution salt concentration were probed to establish effects of molecular charge and charge screening. Hydrogen bonding between compounds and the silica surface is a key factor for stronger adsorption. The findings of this study are important for the rational design of improved silica surfaces through chemical functionalization or through the application of optimal chemical disinfectants that discourage the initial stages of biofilm growth.

From surface activation to microfluidic heat pipes: An innovative in-situ wafer level heterogenous bonding method

There has been considerable interest in low-temperature in-situ integration techniques for the fabrication of hetero-structured substrates and micro/nanosystems. This study presents a novel bonding approach that uses a water vapor-assisted surface activation strategy with neutral oxygen species (NOS). This method enables of highly efficient in-situ bonding process that utilizes the controllable and flexible environment to meet specific integration needs without exposure to the unstable ambient air. The NOS and water vapor increases hydroxyl groups, leading to smoother and more hydrophilic surfaces. The combined effects of NOS and the water vapor result in a larger bonded area ratio and significantly higher bonding energy compared to those activated by NOS alone. Meanwhile, the silicon oxide and quartz glass surfaces avoid being heavily electrically charged. This process thus achieved flawless silicon/quartz glass wafer bonding at 150 °C with a high bonding energy (∼4 J/m2) and Si/Si bonding pairs without any subsequent annealing voids. Then, the bonding pairs have been verified to have high reliability in extreme environments from −65 °C to 200 °C with no thermal-shocked cracks. The high-quality heterointerfaces could also withstand subsequent mechanical grinding and polishing for silicon-on-quartz glass (SOQ) fabrication. Moreover, a SOQ structured microfluidic heat pipe device was successfully fabricated based on the low-temperature in-situ heterogenous bonding. The robust heterointerfaces ensured non-leakage working during the heat dissipation. This facile and cost-effective bonding method is suitable for damage-free heterogeneous integration of active devices, micro/nanofluidic chips, and M/NEMS packaging. It has of great potential in fields such as biochemical analysis, quantum computing, and thermal sensing.

Chemically Powered Nanomotors with Magnetically Responsive Function for Targeted Delivery of Exosomes.

Janus structure plays a crucial role in achieving chemically driven nanomotors with exceptional motion performance. However, Janus-structured chemically driven nanomotors with magnetic responsiveness are commonly fabricated by sputtering metal films. In the study, a self-assembly technique is employed to asymmetrically modify the surfaces of magnetic silica (SiO2@Fe3O4) nanoparticles with platinum nanoparticles, resulting in the formation of this kind nanomotors. Compared to platinumfilm, platinum nanoparticles exhibit a larger surface area and a higher catalytic activity. Hence, the nanomotors demonstrate improved diffusion capabilities at a significantly lower concentration (0.05%) of hydrogen peroxide (H2O2). Meanwhile, exosomes have gained attention as a potential tool for the efficient delivery of biological therapeutic drugs due to their biocompatibility. However, the clinical applications of exosomes are limited by their restricted tropism. The previously obtained nanomotors are utilized to deliver exosomes, greatly enhancing its targetability. The drug doxorubicin (DOX) is subsequently encapsulated within exosomes, acting as a representative drug model. Under the conditions of H2O2 concentration at the tumor site, the exosomes exhibited a significantly enhanced rate of entry into the breast cancercells. The utilization of the nanomotors for exosomes presents a novel approach in the development of hybrid chemically and magnetically responsive nanomotors.

Synthesis and Property Evaluations of a Bio‐Based Anticorrosive Urethane Composites Containing Bisphenol a as Extender

AbstractThis article reports the synthesis of an eco‐friendly polyurethane composite system, which was successfully prepared in a one‐pot synthetic pathway by combining castor seed oil (CSO), bisphenol A (BPA), isophorone diisocyanate (IPDI), and functional hybrid nanoparticles (prepared by modifying the peripheral surface of silica with 3‐aminopropyltrimethoxysilane (APTMS). The urethane composites were cast as thin films on tin foils and mild steel and cured under atmospheric moisture. Attenuated total reflectance Fourier transform infrared (ATR‐FTIR) spectroscopy was used to characterise the cured composite films, scanning electron microscopy (SEM), energy dispersive X‐ray (EDX), X‐ray diffraction (XRD), thermogravimetric analysis (TGA), corrosion resistance, antimicrobial analysis, salt spray test, and water contact angle measurements. Our evaluations showed improved thermal and hydrophobic properties of the composite coatings. Also, the electrochemical and antimicrobial analyses clearly show resistance to corrosion and test organisms as the percentage composition of APTMS‐SiO2 increases in the urethane system.

Dimercaprol-modified mesoporous silica nanoparticles for efficient removal of toxic mercury ions from aqueous solution.

A surface-modified mesoporous silica nanoparticle containing dimercaprol monomers was created utilizing the sol-gel condensation process, using tetraethyl orthosilicate (TEOS) as the silica source and poloxamer as the structure directing agent. To accomplish this synthesis, 3-glycidoxypropyl triethoxysilane (GPTS, 20mol%) was incorporated into the silica walls during the sol-gel condensation process, along with TEOS. Furthermore, dimercaprol (DM) monomers were incorporated onto silica surfaces by a ring-opening reaction between GPTS epoxy groups, and dimercaprol hydroxyl groups. The prepared dimercaprol-modified silica adsorbent (MSN-DT NPs) material has been studied using a variety of instruments, including XRD, FT-IR, N2 adsorption-desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric (TG) analysis, and zeta potential analysis. The MSN-DT NPs material selectively adsorbs mercury ions, with a high adsorption amount of 125mg/g and a removal capability of roughly ~ 90% from the original metal ion mixture comprising other competing metals such as Pb2+, Ni2+, Fe2+, and Zn2+. The MSN-DT NPs adsorbent shows recyclable qualities for up to five cycles when treated with an acidic aqueous solution (0.1M HCl). As a result, the MSN-DT NPs adsorbent may be regenerated and reused up to five times without losing its adsorption effectiveness. The experimental findings showed that the MSN-DT NPs adsorbent may be employed to selectively remove hazardous Hg2+ ions from an aqueous solution.

Characterization of mechanical behavior and cementing mechanism of high-strength composites using biomimetic chemically induced calcium carbonate precipitation method

Biomimetic mineralized mortar (BMM) represents a novel green cementitious material, increasingly recognized for its environmental sustainability. In this study, four typical amino acids including acidic amino acids (aspartic acid, glutamic acid), neutral amino acid (threonine), and basic amino acid (arginine), are employed as crystal modifiers to develop the high-strength BMM (HBMM) based on the biomimetic chemically induced calcium carbonate precipitation (BCICP) method. The mechanical properties and failure morphology of HBMM were evaluated through unconfined compressive strength (UCS) test. The microstructure characteristics of HBMM were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and contact angle test. The results show that amino acid-modified calcium carbonate precipitation can effectively cement loose sand particles and significantly improve the strength of the HBMM. The failure modes of HBMM observed include local failure, vertical splitting failure, shear failure, and splitting-shear mixed failure. Notably, aspartic acid and glutamic acid can induce the formation of vaterite-phase calcium carbonate crystals, while threonine and arginine facilitate the formation of aragonite-phase calcium carbonate crystals. The hydrogen bonding between modified calcium carbonate crystals and silanol groups on the silica surface ensures a tight adhesion of the precipitate to sand surfaces, filling gaps and cementing particles. This study elucidates that using amino acids as modifiers in the BCICP method can significantly enhance the strength of HBMM and influence its microstructure, offering valuable insights for its potential practical applications.

Synthesis of Fe3O4@SiO2–branched polyethylenimine nanospheres for removal of Cr(VI) and anionic dyes

There is a need to design and prepare new sorbents for the effective elimination of toxic metal ions and textile dyes from the environment. In the presented study, the preparation of magnetic functionalized silica composite nanospheres for the removal of inorganic and organic pollutants from aqueous solutions is reported. Firstly, the surface of silica coated magnetic nanospheres was functionalized with epoxy groups via a reaction of 3-glycidoxypropyltriethoxysilane. Then, the branched polyethylenimine (BPEI) was attached to generate positive functional charged groups on the on the Fe3O4@SiO2. The performance of the Fe3O4@SiO2-BPEI nanospheres for the removal of Cr(VI) and Congo Red (CR) and Trypan Blue (TB) dyes was studied under various experimental conditions. The optimum pHs values for adsorption of Cr(VI) ions, CR and TB dyes on the Fe3O4@SiO2-BPEI nanospheres were found to be at pH 2.0, and at pH 4.0, respectively. The maximum adsorption capacities of the Fe3O4-@SiO2-BPEI nanospheres for Cr(VI), CR, and TB were obtained as 356.7, 395.3, and 561.8 mg/g within 90 min equilibrium time, an initial concentration of 500 mg/L, and at 25 ºC, respectively. The adsorption of the tested pollutants were well described by the Langmuir isotherm model and second-order kinetic model. After ten reuse cycles, the adsorption capacity of Fe3O4-@SiO2-BPEI nanospheres was not significantly changed for the tested pollutants. The adsorption mechanism of Cr(VI), CR, and TB by the Fe3O4-@SiO2-BPEI nanospheres was evaluated to be related to ion exchange and ion exchange and/or hydrogen bonding interactions, respectively. The results also suggested that the presented adsorbent may serve as a multi-functional adsorbent for the remediation of industrial effluents. In addition, compared to the unmodified Fe3O4@SiO2, the Fe3O4@SiO2-BPEI nanospheres have antibacterial activities against Escherichia coli (American Type Culture Collection (ATCC) 12435), Pseudomonas aeruginosa (ATCC 10145), Listeria monocytogenes (ATCC 7644), and Staphylococcus aureus (ATCC 43300). Based on the obtained results from this work, the branched polyethylene functionalized magnetic silica nanospheres with antibacterial properties can be used as a potential adsorbent for the removal of metal ions and anionic dyes from wastewater.

CO2 Uptake and Stability Enhancement in Vinyltrimethoxysilane-Treated SBA-15 Solid Amine-Based Sorbents.

Silica-supported amine absorbents, including materials produced by tethering aminosilanes or infusion of poly(ethyleneimine), represent a promising class of materials for CO2 capture applications, including direct air and point source capture. Various silica surface treatments and functionalization strategies are explored to enhance stability and CO2 uptake in amine-based solid sorbent systems. Here, the synthesis and characterization of novel vinyltrimethoxysilane-treated Santa Barbara Amorphous-15 (SBA-15) supports and the corresponding enhancement in CO2 uptake compared to various SBA-15-based control supports are presented. The relationship between CO2 diffusion and amine efficiency in these systems is explored using a previously reported kinetic model. The synthesized materials are characterized with CO2 and H2O isotherms, diffuse reflectance infrared Fourier transform spectroscopy, 1H T1-T2 relaxation correlation NMR, and rapid thermal cycling experiments. The novel support materials are shown to enable high amine efficiencies, approaching a fourfold improvement over standard SBA-15-supported amines, while simultaneously exhibiting excellent stability when cycled rapidly under humid conditions. As the poly(ethyleneimine) loadings are held constant across the various samples, enhancements in CO2 uptake are attributed to differences in the way the poly(ethyleneimine) interacts with the support surface.

Preparation of two amphiphilic dendritic small molecule gelators based on poly (aryl ether) modified silica-based chromatographic stationary phases and molecular shape recognition for shape-restricted isomers

Geometric isomers tend to have similar polarities and differ only in molecular shape. Vigorously developing new stationary phases to meet the requirements for the separation of isomers that have similar physicochemical properties is still an urgent topic in separation science. Poly (arylene ether)-based dendrimers are known for their multifunctional branched peripheral structures and high self-assembly properties. In this paper, two amphiphilic dendritic organic small molecule gelling agents based on poly (aryl ether), PAE-ANT and PAE-PA, were prepared and conjugated to the silica surface. SiO2@PAE-ANT and SiO2@PAE-PA were used as HPLC stationary phases for the separation of non-polar shape-restricted isomers. Both stationary phases have very high molecular shape selectivity for isomers such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), tocopherols and carotenoids. Separation of cis-trans geometric isomers such as diethylstilbestrol and polar compounds such as monosubstituted benzenes and anilines can also be achieved. These two columns offer more flexible selectivity and higher separation performance than commercial C18 and phenyl columns. There is a difference in molecular shape selectivity between the two stationary phases for the same analyte test probes. SiO2@PAE-ANT showed slightly better linear selectivity for non-polar shape-restricted isomers compared to SiO2@PAE-PA with Janus-type PAE-PA bonding phase. This separation behavior may be attributed to the ordered spatial structure formed by the gel factor on the surface of the stationary phase and the combined effect of multiple weak interaction centers (hydrophobic, hydrophilic, hydrogen bonding and π-π interactions). It was also possible to separate nucleoside and nucleobase strongly polar compounds well in the HILIC mode, suggesting that hydrophilic groups in PAE-ANT and PAE-PA are involved in the interactions, reflecting their amphiphilic nature.The results show that the ordered gelation of dendritic organic small molecule gelators on the SiO2 surface, along with multiple carbonyl-π, π-π and other interactions, play a crucial role in the separating shape-restricted isomers. The integrated and ordered functional groups serve as the primary driving force behind the exceptionally high molecular shape selectivity of SiO2@PAE-ANT and SiO2@PAE-PA phases. Alterations in the structure of dendritic organic small molecule gelators can impact both molecular orientation and recognition ability, while changes in the type of functional groups influences the separation mechanism of shape-restricted isomers.

A detailed thermohydraulic performance assessment of surface-modified silver nanofluids in turbulent convective heat transfer

This study investigates the thermohydraulic performance of surface-modified silver nanofluids in turbulent convective heat transfer applications. The primary objective is to evaluate the impact of citrate, lipoic acid, and silica surface modifications on heat transfer coefficients, pressure drops, and friction factors under turbulent flow conditions. Silver nanoparticles (50 nm) with the specified surface modifications were synthesized and dispersed in deionized water, ensuring stable nanofluid preparations. Experimental evaluations were conducted in a smooth brass tube with a uniform heat flux, covering Reynolds numbers from 3400 to 21,800, mass flow rates of 32 to 78 g s−1, and inlet temperatures of 26 °C, 31 °C, and 36 °C. Key findings indicate that the silica-shelled nanofluid (Ag/S) exhibited a significant 35% increase in the heat transfer coefficient compared to DI water, while citrate-coated (Ag/C) and lipoic acid-coated (Ag/L) nanofluids showed slight decreases of 0.2% and 2%, respectively. The mean Nusselt number for Ag/S also increased by 9%, demonstrating enhanced heat transfer capabilities. Surface-modified nanofluids experienced higher pressure drops and friction factors than the base fluid. Ag/C showed a 7.7% increase in pressure drop, Ag/L a 12.3% increase, and Ag/S a 12.5% increase, correlating with an 11.9% rise in viscosity. While surface-modified silver nanofluids, particularly silica-shelled, can significantly improve heat transfer performance, the associated increases in pressure drops and friction factors must be carefully balanced for specific applications. Future research should explore long-term stability, varying nanoparticle concentrations, and more complex geometries to optimize nanofluid formulations for targeted heat transfer applications.

Esterified styrene-maleic acid copolymer modified silica as mixed-mode polymer-brush stationary phases for chromatographic separation

Styrene-maleic acid (SMA) copolymer has received much attention for its excellent solubilization characteristics. In this work, SMA copolymer brush-based chromatographic stationary phases were exploited and developed for the first time. First, SMA copolymer brush was in situ grown on the surface of spherical silica via living/controlled reversible addition-fragmentation chain transfer (RAFT) polymerization method. Subsequently, as a proof-of-concept demonstration, the copolymer was esterified by diethylene glycol mono-2-ethylhexyl ether (DGME) and 2-(2-ethylhexyloxy) ethanol (EHOE), respectively. The obtained Sil-SMA-DGME and Sil-SMA-EHOE copolymer-brush chromatographic stationary phases were characterized by transmission electron microscopy, Fourier transform infrared spectrometer, X-ray photoelectron spectroscopy, and thermogravimetric analysis, respectively. The chromatographic retention mechanism indicated that both the two packed columns exhibited hydrophilic/reverse mixed-mode retention modes. The maximum column efficiency was up to 71,000 N/m. The chromatographic separation performance evaluation indicated that the novel kind of stationary phases had excellent separation capabilities for hydrophilic, hydrophobic compounds and phospholipid standards. In addition, by combination with mass spectrometry identification, the Sil-SMA-DGME column was further exploited for separation and identification of phospholipids in human lung cancer cells. Totally, 9 classes including 186 phospholipid species were successfully identified. The results demonstrated the promising application prospects of the novel kind of SMA copolymer-brush chromatographic stationary phases.

Understanding protein adsorption on silica mesoporous materials through thermodynamic simulations

This work presents a molecular thermodynamic theory to study protein interactions within a charge-regulating silica-like nanopore structure. The theory accounts for electrostatic interactions, steric repulsions, finite-size entropic effects, and protonation equilibrium of silanol groups on silica and protein residue side-chains. Coarse-grained representations of proteins based on their 3D crystallographic structures are employed. We evaluate the influence of pH, salt concentration, and pore size on the adsorption of selected proteins (cytochrome c, lysozyme, and myoglobin) in both single- and binary-protein solutions. The surface charge density on the nanopore walls is less negative than on the adjacent planar surface, primarily influenced by pH and salt concentration. Adsorption within the nanopore from single protein solutions exhibits a non-monotonic behavior with pH, increasing with decreasing salt concentration and diminishing pore size. Analysis of the effective interactions between proteins and silica surfaces indicates that adsorption is enhanced when the protein size matches that of the nanopore. Evaluation of various adsorption pathways indicates minimized free energy when the protein enters the nanopore through its edge and contacts its cylindrical walls. In binary solutions, the presence of another protein significantly alters the affinity of a protein for the silica surfaces, potentially preventing its adsorption, and affects its organization on these surfaces upon adsorption.

NiO/vermiculite composites prepared for photocatalytic degradation of methanol-water solution and hydrogen generation

A novel eco-friendly NiO/Vm clay based photocatalysts were synthesized from two vermiculites (Vm1 and Vm2) and nickel(II) nitrate hexahydrate (Ni(NO3)2·6H2O salt precursor by the chemical precipitation without and with the sodium hydroxide (NaOH) or ammonium hydroxide (NH4OH, 28% NH3 in H2O) as precipitation agents (Synthesis A) in comparison with the solid-state thermal decomposition (Synthesis B) at 600 °C. Structural properties of all specimens were characterized by X-ray fluorescence, scanning electron microscopy, X-ray diffraction, infrared (IR) and Raman spectroscopy. The photocatalytic performance of NiO/Vm composites was evaluated under UV radiation (λ = 254 nm) for decomposition of methanol-water to hydrogen over 4-h and the stable yield of hydrogen over the 24-h periods. The NaOH and NH4OH affected the NiO crystallite size and therefore the photocatalytic activity during 4 h. Different 2:1 layer charge of Vm1 (0.82 e−) and Vm2 (0.40 e−) and the specific surface area of Vm1 (about 43 m2/g) and Vm2 (about 34 m2/g) supported H2 yield of 628.2 μmol/gcat. and 596.8 μmol/gcat., close to 657.0 μmol/gcat. produced in the presence of commercial photocatalyst TiO2 Evonik P25. Crystalline NiO precipitated and anchored in NiO/Vm composites contained smaller crystallites than those in free NiO. Vermiculite silica surface supports coverage of NiO by hydrogen bonding to Si-OH groups influencing the geometry of the NiO crystal structure (disorder NiO(X)). The heterojunction with Si-O-Ni bonding, at which electrons transfer from Vm to NiO cause enriching electron density in NiO and favoring its photocatalytic activity. Photocatalytic hydrogen generation from methanol–water mixture at the presence of all specimens indicated the main product H2 and minimum by-products CH4 and CO. The stable hydrogen production for 24 h was confirmed only in the presence NiO/Vm1–24 while maintaining the NiO(X) in small crystallites. The thermal solid-state procedure provided the gradual dehydration of vermiculites and Ni(NO3)2·6H2O to the same amount and crystallinity of NiO in NiO/Vm1 and NiO/Vm2 composites. The results of this work confirm that vermiculites mixed layer structures with different negative layer charge play a dominant role as semiconductors for anchored NiO. The photocatalytic activity of NiO/vermiculite composites can be harnessed to treat wastewater containing organic contaminants.

Adsorption isotherm and kinetics of diffusion of water accumulated between polypropylene thin film and Si substrate: Neutron reflectivity investigation

Isotactic polypropylene (PP) thin films deposited on Si substrates were subjected to neutron reflectivity (NR) measurements under various humidity conditions to evaluate the isothermal adsorption of water accumulated between the PP layer and Si substrate, with focus on the temperature-dependence of the adsorption isotherm. The adsorption of accumulated water followed a single type II isotherm according to the Brunauer-Emmett-Teller (BET) classification, regardless of temperature. This can be attributed to the weak interactions between the PP layer and Si substrate, and between the PP layer and water molecules. Hydrophobic PP does not significantly interact with water molecules and the hydrophilic Si surface. Therefore, the interfacial water molecules are simply adsorbed on the native oxide layer on Si via simple interaction between the water molecules and the silicon oxide surface without being affected by the PP layer. Consequently, the adsorption isotherm of the accumulated water follows the single type II adsorption isotherm regardless of temperature, similar to the adsorption isotherm of water simply adsorbed on exposed silica surfaces. These weak interactions of the PP layer with the Si surface and water molecules also lead to fast diffusion kinetics for the accumulated water along the interface.

Enhanced performance of quasi-solid-state silicon-air batteries through light-assisted anodic reactions

Silicon-air batteries (SABs) offer a promising energy storage solution due to their high theoretical energy density, cost-effectiveness, and environmental friendliness. However, practical applications are hindered by limitations in maximum discharge current density and discharge voltage, stemming from intrinsic electrochemical properties of the silicon (Si) anode and surface oxidation kinetics. This study addressed the low maximum discharge current density of SABs by leveraging the Si semiconductor properties and employing a light-assisted strategy. Introducing light to the silicon anode generates photogenerated electron-hole pairs. Furthermore, introducing light to the Si anode allowed for the generation of photogenerated electron-hole pairs. The resulting holes reacted with OH- ions to form hydroxyl radical (OH), which efficiently oxidized the Si surface, thereby facilitating electrochemical reactions. This enhancement increased the anodic reaction kinetics, thereby enhancing the maximum discharge current density of SABs. Furthermore, through this strategy, light-assisted SABs exhibited significant performance improvements: under 1 sun illumination, maximum discharge current density increased by 50.0 %, discharge voltage by 10.0 %, and power density by 45.0 %. Under 3 suns illuminations, these metrics improved further, with maximum discharge current density increasing by 87.5 %, discharge voltage by 20 %, and power density by 200 %. Additionally, quasi-solid-state SABs (QSSSABs) according to this strategy exhibited versatility across various application scenarios, thereby significantly expanding the practical potential of SABs technology.

Surface quality and microstructure evolution in fused silica under SF6/Ar reactive ion beam etching

The SF6/Ar reactive ion beam etching (RIBE) was proposed to explore the evolution of surface quality, subsurface defects, surface molecular structure, and chemical composition of fused silica. Also, the mechanism of reactive ion beam etching of fused silica surfaces was discussed. The results show that RIBE can maintain the original surface roughness by choosing suitable process parameters. this etching process can suppress the replication and expansion of subsurface defects and the deposition of reactants without bringing obvious contamination. The concentration of structural defects reaches a minimum at an etching depth of about 2 μm. However, further etching may lead to an increase in the chemical structure defects on the surface. The evolution of the intrinsic ring structure demonstrates that most intrinsic defects tend to reorganize into short (Si-O) ring structures. The etching mechanisms of Ar ions were discussed by simulating the stopping power and energy deposition. Phonon dissipation through atomic displacements and atomic vibrations is an important way of energy loss. Phonon vibrations and atomic dislocations induced by nuclear collisions are not only important factors causing the enhancement of electron-phonon coupling but also important causes of surface structural defects. The researches provide a theoretical basis for in-depth understanding of fused silica surface defect repair.

Migration of natural organic matter and Pseudomonas fluorescens-associated polystyrene on natural substrates in aquatic environments

This study investigated the migration behavior of microplastics (MPs) covered with natural organic matter (NOM) and biofilm on three substrates (silica, Pseudomonas fluorescent and Pseudomonas aeruginosa biofilms) in various ionic strengths, focusing on the alterations in surface properties based on surface energy theory that affected their deposition and release processes. Peptone and Pseudomonas fluorescens were employed to generate NOM-attached and biofilm-coated polystyrene (PS) (NOM-PS and Bio-PS). NOM-PS and Bio-PS both exhibited different surface properties, as increased roughness and particle sizes, more hydrophilic surfaces and altered zeta potentials which increased with ionic strength. Although the deposition of NOM-PS on biofilms were enhanced by higher ionic strengths and the addition of Ca2+, while Bio-PS deposited less on biofilms and more on the silica surface. Both types exhibited diffusion-driven adsorption on the silica surface, with Bio-PS also engaging in synergistic and competitive interactions on biofilm surfaces. Release tests revealed that NOM-PS and Bio-PS were prone to release from silica than from biofilms. The Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory furtherly demonstrated that mid-range electrostatic (EL) repulsion had significantly impacts on NOM-PS deposition, and structural properties of extracellular polymeric substances (EPS) and substrate could affect Bio-PS migration.