Silica Surface Research Articles

Influence of the Functional Groups of Modifying Chelates on the Adsorption of Aromatic Hydrocarbons by the Silica Surface

Influence of the Functional Groups of Modifying Chelates on the Adsorption of Aromatic Hydrocarbons by the Silica Surface

Unraveling the adsorption dynamics of asphaltene molecules on silica surfaces

Understanding the adsorption behavior of heavy oil components on reservoir solids is crucial for improving oil recovery, yet the molecular mechanism remains unclear. This study used molecular dynamics simulations to explore the adsorption kinetics and thermodynamics of asphaltene molecules on silica surfaces. The adsorption process was divided into three stages: free, adsorption, and equilibrium. In the adsorption stage, asphaltenes must pass through two dense hydration layers and adhere to the silica surface in a flat configuration. Carboxyl groups increase asphaltene hydrophilicity, raising interaction energy with water molecules and hindering adsorption. In addition, two distinct hydration layers of water molecules on the silica surface. The first hydration layer, with a peak density of 2000 kg m−3, was located around 0.6 nm from the surface, driven by hydrogen bonding between Si-OH groups and water molecules. The second layer, found at 1.44–1.80 nm, had a lower density of 1200 kg m−3, formed through hydrogen bonding between water molecules. This study aims to enhance the understanding of the physicochemical mechanisms governing oil droplet adsorption on silica surfaces, potentially informing the design of improved oil recovery strategies.

Preparation of New Hybrid Materials SiO2@Melamine-Cyanurate as Precursors of Graphite-Like Carbon Nitride

This work describes the use of silica particles obtained by sol-gel method as a templat for deposition of supramolecular complexes of melamine cyanurate. To obtain SiO2@melamine-cyanurate (SiO2@MCA) material, the method of covalent modification of silica surface by melamine molecules (SiO2-mel) was applied and the method of its further functionalization by hydrogen-bonded organic framework of melamine-cyanurate (HOF, MCA) was proposed. One of the promising directions of using SiO2@melamine-cyanurate is obtaining SiO2@g-C3N4 material on its basis. Control of the amount of applied melamine-cyanurate allows to potentially obtain g-C3N4 layers of different thicknesses on the silica surface.

Study on the wetting characteristics of liquid-Al/ SiO2 interface with Si content in liquid-Al

Aiming to address the issue of aluminum slag adhering to the interior walls of vacuum lifting ladles in the aluminum electrolysis industry, Molecular dynamics simulations are employed to investigate the wetting behavior and adhesion characteristics of aluminum droplets on silica surfaces. Our findings indicate that with an increase in silicon content within the droplets, wetting diminishes and complete wetting of the silica substrate by aluminum droplets is not achieved. The presence of silicon reduces both the melting point temperature and surface tension of aluminum droplets, leading to a significant increase in contact angle and a corresponding decrease in wettability. Moreover, an elevated silicon content within molten aluminum droplets substantially decreases their interaction energy with the substrate surface. The virtual wall method is applied to examine average separation force and work of separation for detaching aluminum droplets from the substrate, revealing that adhesion characteristics are predominantly governed by mutual adhesive forces. This paper presents an atomic-level analysis elucidating how silicon as an alloying element influences adhesion between liquid aluminum and solid surfaces.

Silica‐Mediated Incorporation of Lipase Into The Bulk of a Deep Eutectic Solvent: An Efficient Biocatalytic Phase for Esters Synthesis

Aiming at sustainable solutions suitable for industrial‐scale catalysis catalytic phase containing lipase and Deep Eutectic Solvent (DES) was designed. To achieve this, both physical and chemical immobilizations of lipases were performed on the surface of silica and carbon materials. The catalytic activity of developed biosystem was tested in biotransformation of α‐angelica lactone into butyl levulinate at 60°C. The best results were achieved for Candida antarctica lipase B adsorbed on fumed silica suspended in choline chloride: glycerol (1:2) with the addition of 20 wt% of water. Under these conditions 99.9% conversion of α‐angelica lactone and 100% selectivity to butyl levulinate were obtained after 45 min. The biocatalytic system maintained its activity for up to five consecutive reaction cycles with full conversion of lactone to ester. The heterogenization of the enzyme allowed the biocatalyst to be integrated into the bulk of the DES, which includes essential water. This combination resulted in the formation of a stable and easy‐to‐operate catalytic phase where reagents formed a second organic phase. The integration of cost‐effective biocatalyst with process efficiency provides a greener alternative with significant potential for industrial use.

Studying the optical properties of assembled silver and gold nanoparticles for the purpose of creating SERS sensors

The optical properties of silver and gold sols with different sizes of nanoparticles and the method of their chemical deposition on the surface of silicon, silicon oxide, glass and aluminum foil were studied in order to obtain SERS substrates – promising platforms for the development of aptamer sensors and immunochemical analysis of various pathogens. It has been established that for operation on lasers with exciting radiation wavelengths of 532, 638 and 785 nm, it is possible to create universal SERS substrates based on colloidal solutions obtained by the liquid-phase chemical method with an average silver particle size of 40 nm and by the Leopold-Lendl method with an average size of 20 nm.

Adsorption dynamics of heavy oil droplets on silica: Effect of asphaltene anionic carboxylic

Understanding the adsorption behavior of asphaltene molecules on the surfaces of oil reservoir solids is essential for optimizing oil recovery processes. This study employed molecular dynamics simulations to investigate the adsorption behavior of oil droplets composed of charged and neutral asphaltenes on silica surfaces. The results revealed that oil droplet containing anionic asphaltene molecules were more likely to adsorb onto silica surfaces and exhibited greater resistance to detachment compared to oil droplet containing neutral asphaltene molecules. Specifically, anionic asphaltene molecules tended to accumulate at the oil-water-silica interface, whereas neutral asphaltene molecules primarily adsorbed near the oil-water interface. These findings provide valuable insights into the differing adsorption dynamics of charged and neutral asphaltene molecules on silica surfaces.

Structure, Properties, and Applications of Silica Nanoparticles: Recent Theoretical Modeling Advances, Challenges, and Future Directions.

Silica nanoparticles (SNPs), one of the most widely researched materials in modern science, are now commonly exploited in surface coatings, biomedicine, catalysis, and engineering of novel self-assembling materials. Theoretical approaches are invaluable to enhancing fundamental understanding of SNP properties and behavior. Tremendous research attention is dedicated to modeling silica structure, the silica-water interface, and functionalization of silica surfaces for tailored applications. In this review, the range of theoretical methodologies are discussed that have been employed to model bare silica and functionalized silica. The evolution of silica modeling approaches is detailed, including classical, quantum mechanical, and hybrid methods and highlight in particular the last decade of theoretical simulation advances. It is started with discussing investigations of bare silica systems, focusing on the fundamental interactions at the silica-water interface, following with a comprehensively review of the modeling studies that examine the interaction of silica with functional ligands, peptides, ions, surfactants, polymers, and carbonaceous species. The review is concluded with the perspective on existing challenges in the field and promising future directions that will further enhance the utility and importance of the theoretical approaches in guiding the rational design of SNPs for applications in engineering and biomedicine.

A molecular dynamics simulation study of EthylChlorophyllide A molecules confined in a SiO2 nanoslit.

This paper investigates the dynamic behavior of EthylChlorophyllide A (EChlideA) molecules in a methanol solution confined within a 4nm silica nanoslit, using molecular dynamics simulations over a duration of 1ms. Three systems, containing 1, 2, and 4 solutes, were studied at 298K. The results demonstrate that EChlideA molecules predominantly adsorb onto the silica surfaces, driven by specific interactions between chlorin ring's methyl group and the hydroxyl groups of the silica. This adsorption leads to stable binding, particularly in less crowded environments, as indicated by the potential of mean force analysis. Higher molecular concentrations, such as those with four EChlideA molecules, introduce variation in binding strength due to molecular aggregation and complex interactions. The orientation analysis reveals that the chlorin ring tends to align parallel to the surface, requiring rotational adjustments during surface diffusion. In addition, solvent coordination around the Mg ion remains consistent under bulk conditions, although with some variation in higher concentrations. This study also highlights a decrease in linear diffusion and an increase in rotational relaxation times for EChlideA molecules within the confined nanoslit, reflecting the influence of molecular concentration and arrangement on their dynamics. These findings provide valuable insights into the role of surface interactions, molecular orientation, and solvent coordination in confined environments, offering implications for the design of nanoscale systems.

Silica surface modification using cellulose as a renewable organosilane derived from coconut coir fiber for carbon capture

The properties of silica surface modification for carbon capture were studied, utilizing cellulose-amine as a modification agent derived from dissolved coconut coir fiber. To form bonds with NH2 functional groups through amination processes, cellulosic biomass waste is utilized, which is analogous to replacing alkoxy ligands. The dual-function mixture reagents dimethyl sulfoxide (DMSO) and ammonium hydroxide (NH4OH) were employed in the same system as the amine sources and solvents. Waterglass is used as a source of silica, and the modified particles are formed using a one-step consecutive sol-gel spray drying process used in a direct condensation route. Changes in the concentration of sodium lauryl sulfate (SLS) were examined to determine how they affected the essential parameters of the particles. The template is removed during particle formation without further physical or chemical processing. The particle morphology changed from donut-shaped to spherical after SLS application, as evidenced by the increase in SLS concentration. This also shows that the increase in the particle surface area is directly influenced by the increase in the formation of new pore structures with increasing SLS concentration. Through this mechanism, it is possible to extend the pore size distribution to the meso-macropore regime and initiate the formation of new mesopores. This has a direct impact on the capacity to absorb CO2 gas by increasing the cellulose-amine mass fraction that can be grafted to as high as 32.35 %wt. At an operating pressure of 6 bar, a maximum CO2 gas adsorption capacity of 5.32 mmol/g silica was attained by adding SLS 3 CMC to the silica particles. This value is 2.3 times higher than that obtained when using an aminosilane-based modification agent.

B-064 Bovine Serum Albumin Coats Silicon Dioxide More Uniformly Near its Isoelectric Point Based on Atomic Force Microscopy Analysis

Abstract Background Bovine serum albumin (BSA) serves as a blocking agent in in-vitro diagnostic (IVD) applications, with fatty acid stabilized (FAS) and fatty acid free (FAF) BSA as common options. The presence of fatty acids and pH influence the conformation of BSA. While previous studies have explored the individual effects of fatty acids or pH on BSA blocking, limited data exists on their combined impact. This study employs atomic force microscopy (AFM) to investigate how pH and fatty acids jointly affect BSA adsorption onto silica, a surface relevant within diagnostics. Methods AFM, a sensitive microscopic technique, provides topographic images of surfaces with superior resolution compared to optical microscopy. We conducted experiments to assess the adsorption of 1% FAS and FAF BSA on a silica surface at pH 5.2 and pH 7. Evaluation of the coatings involved scratching to assess overall thickness, and roughness, indicating thickness variability. Results Results revealed that both fatty acids and pH play significant roles in shaping the BSA coating characteristics on silica surfaces. In three out of four experimental conditions, the average thickness of the BSA coating ranged between 3-4 nm, except for FAS BSA at pH 7, which exhibited a thicker average coating measuring 5.6 nm. The pH impacted the roughness of the BSA coating. Coatings prepared at pH 5.2 displayed smoother surfaces compared to those at pH 7. Utilizing the root mean square average height variability analysis, there is 95% confidence that the FAF and FAS BSA surfaces at pH 5.2 had a height range between 2.4-4.3 nm and 2.0-4.9 nm, respectively, indicating complete coverage of the silica surface without much height variation. In contrast, the FAF and FAS BSA coatings at pH 7 exhibited a wider range of heights, with 95% confidence intervals spanning from -1.5-8.6 nm and 0.0-11.2 nm, respectively. This variability suggests potential issues including incomplete BSA coverage at the lower range, and steric hindrance at the higher end, highlighting the importance of pH in optimizing BSA coatings for various applications. Conclusions Silica is commonly used in IVD assays, with BSA frequently employed to coat and passivate the surface. Our AFM experiments highlight the impact of pH and fatty acid presence on coating thickness and uniformity. Notably, FAS BSA at pH 7 exhibited the thickest coating; however, its increased roughness may pose challenges in IVD applications due to steric hindrance blocking antibody-antigen interactions. Alternatively, FAF BSA at pH 7 displayed an adequate thickness but also considerable roughness, suggesting potential insufficiencies in surface coverage and passivation. FAS and FAF BSA coatings at pH 5.2 showed relatively consistent thickness, indicating a more uniform surface which may be ideal for IVD coating applications. These AFM experiments were conducted on pure silica surfaces, which may differ from surfaces engineered for IVD. Additionally, both FAF and FAS BSA grades are proven to be effective in IVD applications. Further research employing AFM and other biophysical techniques is warranted to deepen our understanding of pH and fatty acid effects on BSA-surface interactions, aiming to enhance blocking strategies in IVD.

B-090 Efficient Hydrophilic Surface Coating with Low Concentrations of Bovine Gamma Globulins

Abstract Background Bovine Gamma Globulin (BGG) is a high purity immunoglobulin fraction of bovine serum. BGG is used as a blocker to prevent non-specific binding in immunoassays and, due to the mixture of immunoglobulins, its blocking capabilities differ from traditional blockers like Bovine Serum Albumin (BSA). Our objective was to evaluate the adsorption characteristics of BGG to In vitro diagnostic relevant hydrophilic surfaces compared to BSA. A bead-based immunoassay was utilized to quantify the mass of protein coating a bead surface and atomic force microscopy (AFM) to analyze physical properties of the protein-surface layer. Methods The mass of BGG bound to hydrophilic beads (Dynabeads M-270 Carboxylic Acid) was determined across varying concentrations ranging from 0.1% to 1.0% in pH 7.0 phosphate buffer. Coated beads were heated in 1x SDS loading dye to dissociate bound protein, then ran on a nonreducing SDS-PAGE gel. The total protein was measured using densitometry against a standard curve, using ImageJ, and analyzed with GraphPad Prism. This methodology was also used for BSA. AFM was used to image a topographical view of BGG binding to a silica surface. Samples were prepared at concentrations from 0.1% to 1.0% in phosphate buffer at pH 7.0. Followed by a series of washes to remove non-bound molecules, the surface was allowed to dry, then scratched with an AFM cantilever. The surface was then analyzed for roughness and thickness of BGG adsorption for each concentration. Results BGG and BSA have notable differences in their coating properties at a concentration of 1.0%. In the bead assay, the protein-surface binding is enhanced ∼4.8-fold for BGG compared to BSA. Interestingly, even at 0.1% BGG bound ∼0.8-fold more than BSA at 1.0%. Despite a 6-fold increase in mass bound to the bead surface with 1.0% BGG compared to 0.1%, AFM revealed a 1.3-fold and 1.8-fold decrease in height and roughness at the lower concentration, while maintaining effective coating. These results suggest that higher BGG concentrations result in thicker, rougher surface coating. This could lead to steric hindrance and obstruction of binding sites, affecting assay performance. Therefore, a lower concentration of BGG may lead to better surface coating and prevent reduced sensitivity and accuracy within immunoassays. Conclusions The bead binding assay demonstrates that BGG displays surface adsorption with comparable or improved results with lower concentrations compared to BSA. At 0.1%, BGG exhibits effective binding to a hydrophilic surface equivalent to that achieved by BSA at 1.0%. Additionally, AFM data suggest that even at 0.1%, BGG effectively coats the silica surface and potentially reduces steric hinderance compared to BGG at 1%. While BSA remains a reliable choice for many applications, our findings suggest that BGG can be an effective blocker for immunoassay applications. The choice of a suitable blocker varies depending on factors such as assay high background, sensitivity, and specificity. By tailoring the choice of blocker to the specific requirements of the assay, researchers can optimize assay performance by improving the accuracy and the reliability of the assay.

Wetting Preference of Silica Surfaces in the Context of Underground Hydrogen Storage: A Molecular Dynamics Perspective.

The growing interest in large-scale underground hydrogen (H2) storage (UHS) emphasizes the need for a comprehensive understanding of the fundamental characteristics of subsurface environments. The wetting preference of subsurface rock is a crucial parameter influencing the H2 flow behavior during storage and withdrawal processes. In this study, we utilized molecular dynamics simulation to evaluate the wetting preference of the silica surface in subsurface hydrogen systems, with the aim of addressing disparities observed in experimental results. We conducted an initial comprehensive assessment of potential models, comparing the wettability of five common silica surfaces with different surface morphologies and hydroxyl densities in CO2-H2/water/silica systems against experimental data. After introducing the INTERFACE force field as the most accurate potential model for the silica surface, we evaluated the wetting behavior of the α-quartz (101) surface with a hydroxyl density of 5.9 number/nm2 under the impact of actual geological storage conditions (333-413 K and 10-30 MPa), the coexistence of cushion gases (i.e., CO2, CH4, and N2) at various mole fractions, and pH levels ranging from 2 to 11 characterized through considering the negative charges of 0 to -0.12 C/m2 via deprotonation of silanol on the silica surface. Our results indicate that neither pressure nor temperature has a significant impact on the wetness of the silica in the case of pure H2 (single component UHS operations). However, when CO2 coexists with H2, especially at higher mole fractions, an increase in pressure and a decrease in temperature lead to higher contact angles. Moreover, when the mole fraction of cushion gas ranges from 0 to 1, the contact angle increases 20, 9.5, and 4.5° for CO2, CH4, and N2, respectively, on the neutral silica substrate. Interestingly, at higher pH conditions where the silica surface carries a negative charge, the contact angle considerably reduces where surface charges of -0.03 and -0.06 C/m2 result in an average reduction of 20 and 80% in the contact angle, respectively. More importantly, at a pH of ∼11 (-0.12 C/m2), a 0° contact angle is observed for the silica surface under all temperatures, pressures, types of cushion gases, and varying mole fractions.

Photochemical Oxidation of Polyethylene Terephthalate Microplastics Adsorbed on Sand and Silica Surfaces.

The environmental contamination by plastics, microplastics, and related compounds is a major concern. While the detection and release of micro- and nanoparticles from these materials have been widely studied, the formation and release of molecules resulting from their degradation in the environment have been overlooked. This work presents a study of the products released from poly(ethylene terephthalate) (PET) irradiated as pure particles and adsorbed on silica and sand surfaces under different irradiation conditions. The role of oxygen was also evaluated. The products were identified by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-high resolution mass spectrometry (LC-HRMS). The main released molecules can be accounted for by considering the cleavage of α- and β-bonds next to the ester moiety of the polymer chain. Volatile products such as benzene as well as monomer units of the polymer and related products were identified. In the presence of oxygen, acetic acid and products resulting from hydroxylation at the benzenic ring or at the ethyl moiety were detected. Adsorption on silica and sand has little effect on the photoproduct distributions. The irradiation at 360 nm leads to distributions similar to the ones observed at 257 nm, but the reaction rate is lower. The identified product ethylene terephthalate is a marker of PET plastics and particles and can therefore be used to evaluate the environmental contamination by this polymer material.

Wide-pore fully porous mixed-mode octyl/pyridyl-bonded silica material with pH-dependent surface charge reversal for high-performance hydrophobic charge-induction chromatography of proteins

In an attempt to overcome silanophilic interactions like observed on popular reversed-phase butyl‑bonded silica stationary phases in protein HPLC, a mixed-mode stationary phase based on wide pore silica (3 µm, 300 Å) was prepared by co-immobilization of octyl and 2-pyridylethyl ligands. The surface modification was performed by a new approach using synthesized functional silatranes of the above ligands and prewetted silica. It allowed to generate a dense polymeric siloxane layer on the silica surface. Butyl-bonded silica and octyl/3-aminopropyl-bonded mixed-mode silica phases were prepared for comparison. The modified silicas were subsequently characterized by elemental analysis regarding ligand densities, by solid-state 29Si and 13C cross polarization/magic angle spinning nuclear magnetic resonance spectroscopy for confirming the surface-bonded structure, and by pH-dependent ζ-potential measurements via electrophoretic light scattering providing net surface charge information at distinct pH values. While the classical butyl‑bonded stationary phase revealed negative ζ-potential over the entire pH range investigated (pH 3.5–9.5) due to residual silanols and the mixed-mode octyl/3-aminopropyl-bonded silica positive ζ-potential over the entire pH range, pH-dependent charge reversal was observed at approximately pH 5.5 for the octyl/pyridyl-bonded stationary phase. Then, a test set of proteins differing in hydrophobicities and isoelectric points was employed to evaluate the retention characteristics of all three synthesized stationary phases over the pH range of 3 to 7.5 by acetonitrile-gradient elution reversed-phase HPLC. Under acidic conditions (pH 3) the mixed-mode phases octyl/pyridyl-silica and octyl/aminopropyl-silica showed reduced retention and improved peak shapes due to repulsive interactions preventing silanophilic interactions, while protein separations by their hydrophobicities were achieved (repulsive charge-assisted protein RPLC). Finally, the prepared novel mixed-mode octyl/pyridyl-bonded stationary phase was evaluated in hydrophobic charge induction chromatography mode for protein separation of the same test set. Instead of an organic modifier gradient, elution was enforced by a pH gradient from almost neutral to acidic pH at constant organic modifier content of 10 %. This chromatographic mode showed orthogonal retention characteristics and reversed elution order compared to above organic gradient RP-HPLC. In addition, significantly less organic solvent was used under these conditions, classifying it as a green protein LC technology.

Enhanced photocatalytic degradation of antiviral drugs lopinavir and ritonavir by Ni doped ZnO/SiO2 nanocomposites

A series of silica-based Ni doped ZnO nanocomposites were successfully synthesized by the co-precipitation of zinc and nickel acetate salts in the presence of urea on the surface of amorphous silica using thermo-oxidative degradation at 600 °C with a concentration of 3, 6 and 9 mmol ZnO per 1 g SiO2. The effects of the dopants and SiO2 matrix on the structure, morphology and optical properties of the composites were investigated using N2 adsorption-desorption, Raman, XRD, UV-Vis, PL, FT-IR, SEM, and TEM analyses. XRD indicated the formation of a hexagonal ZnO wurtzite structure, while Ni2+ ions substituted Zn2+ sites in the host lattice. The size of nanoparticles was in the range of 10–100 nm and showed a broad fluorescence emission at 442–433 nm. The specific surface area was 110–171 m2 g−1. The materials showed high efficiency in removing the antiviral SARS-CoV-2 drugs lopinavir (LOPI) and ritonavir (RITO) from water. The comparative photocatalytic activity showed 100 % removal of LOPI by 3-, 6- and 9-Ni-ZnO/SiO2 photocatalysts after 60, 30 and 45 min of ultraviolet light irradiation, respectively, and 60 min for RITO for all catalyst samples. The effects of inorganic ions, dissolved organics and reusability on photocatalytic degradation were also described in terms of practical applications.

Temperature-induced desorption and decomposition of the organic molecule on the fused silica surface: Cleaning mechanism of laser heating

Understanding the structure–property relationships of the organic molecule-fused silica interface at the molecular level provides insights into the nature of their adhesion and desorption. In this study, molecular dynamic simulation and the ReaxFF force field are employed to investigate the adhesion properties of benzene, toluene, dodecane and dibutyl phthalate (DBP) on fused silica at different temperatures. The result shows that adhesion energy between benzene or toluene molecules and fused silica decreases gradually with the increased system temperature. The temperature affects Coulomb and van der Waals forces significantly. Environmental humidity affects the evaporation rate of alkane contaminants from fused silica. Besides, ambient humidity also affects the number of alkane molecules adsorbed to the fused silica surface and the chain configuration of adsorbed alkane molecules. Although the coverage of alkane molecules on fused silica is different, the relationship between temperature and the amount of adsorbed alkane molecules is not affected by the surface coverage of alkane molecules on the fused silica surface. These findings provide theoretical support for removing transparent organic contaminants from glass-like material surfaces using laser heating, laying the theoretical foundation for developing laser cleaning technologies.

Morphological evolution mechanism of microstructures involved in shaping micro-pillar arrays into microlens arrays on fused silica surfaces by CO2 laser polishing

The periodic micro-pillars on the hard-brittle fused silica surface can be shaped into the smooth and defect-free microlens arrays (MLA) by CO2 laser polishing, which can be applied in imaging and beam-shaping. However, the morphology evolution mechanism of the micro-pillars is not clear during polishing, which seriously affects the rapid preparation of high-quality MLAs. Herein, a multi-physics coupling model is established to investigate the interaction between CO2 lasers and micro-pillars on the fused silica surface, and is verified from the perspectives of temporal and spatial temperature. The steady surface temperature evolution law with laser power and spot radius is explored, based on which, the parameter ‘Window’ for polishing is determined to make the material melt and flow without ablation removal. The morphology evolution of micro-pillars is investigated as well as laser-material interaction. It is found that under laser irradiation, the micro-pillar height first increases and then decreases, and its top curvature radius increases. The surface tension makes the dominant contributions to the melting and flow of the micro-pillar materials, while the Marangoni effect and the gravity have little effect. Furthermore, to fabricate the target MLAs with the specific dimensions, the influence of micro-pillar aspect ratio (φ) on microlens surface morphology is investigated. It is found that there are two critical φ for the target MLAs. For the required MLA with the target period of 200 μm and the target height of 40 μm, when the φ is larger than 5.1, the micro-pillar array fails to be shaped into the target MLA by CO2 laser polishing. As the φ decreases, the junction of micro-pillar and the substrate sags downwards significantly, and the deviation between the shaped- and the ideal spherical contours increases. To successfully prepared the target MLA and guarantee the geometry accuracy, the minimum φ is selected to be 0.71. This work has important theoretical significance for obtaining the smooth and defect-free target fused silica MLAs with the specific dimensions by CO2 laser non-evaporative polishing.

Hybrid Carbon Black/Silica Reinforcing System for High-Performance Green Tread Rubber.

Silica, as a high-quality reinforcing filler, can satisfy the requirements of high-performance green tread rubber with high wet-skid resistance, low rolling resistance, and low heat generation. However, the silica surface contains abundant silicon hydroxyl groups, resulting in a severe aggregation of silica particles in non-polar rubber matrix. Herein, we explored a carbon black (CB)/silica hybrid reinforcing strategy to prepare epoxidized natural rubber (ENR)-based vulcanizates. Benefiting from the reaction and interaction between the epoxy groups on ENR chains and the silicon hydroxyl groups on silica surfaces, the dispersion uniformity of silica in the ENR matrix was significantly enhanced. Meanwhile, the silica can facilitate the dispersity and reinforcing effect of CB particles in the ENR matrix. By optimizing the CB/silica blending ratios, we realized high-performance ENR vulcanizates with simultaneously improved mechanical strength, wear resistance, resilience, anti-aging, and damping properties, as well as reduced heat generation and rolling resistance. For example, compared with ENR vulcanizates with only CB fillers, those with CB/silica hybrid fillers showed ~10% increase in tensile strength, ~20% increase in elongation at break, and ~20% increase in tensile retention rate. These results indicated that the ENR compounds reinforced with CB/silica hybrid fillers are a promising candidate for high-performance green tread rubber materials.

Rapid and selective separation of heavy metal ions from aquatic medium using a bidentate functionalized hybrid material

Low-cost mesoporous silica material, functionalized with a bidentate pyrazolyl pyridine metal acceptor and presenting a high specific surface area of 417 m²/g, was synthesized (mSi-L3) using a two-step procedure and characterized in detail to confirm the successful covalent binding onto silica surface. Notably, mSi-L3 exhibited strong selectivity for PbII among CdII and CuII ions, and displayed rapid metal ion removal, typically less than 10 min, from water samples.The influence of various environmental parameters on the adsorption process, such as pH, contact time and temperature, was systematically investigated. Optimal adsorption of metal ions was achieved at pH 6, as lower pH values reduced the availability of active sites due to competitive hydronium ion presence. Kinetic studies indicated that the adsorption process adhered to the pseudo-second-order model, suggesting a chemisorption mechanism. Temperature significantly influenced the adsorption capacity, with increased temperatures enhancing metal ion removal and confirming the endothermic nature of the process. The isotherm study suggests that the Langmuir model accurately describes the adsorption process, confirming that CuII, CdII and PbII ions are adsorbed as a monolayer on the homogeneous surface of m-SiL3 material, implying that the material has uniform adsorption sites where each metal ion occupies a distinct site without interaction with neighbouring ions. These findings underscore the importance of optimizing environmental conditions to maximize the efficiency of mSi-L3 for heavy metal removal. Also, mSi-L3 demonstrated excellent stability, with only a slight (∼1−3 %) decrease in functional groups on its surface after multiple regeneration cycles. Extensive analytical studies conducted with real water samples provided further evidence of the stability and effectiveness of mSi-L3 for the separation of metal trace elements of lead, copper and cadmium.