Hybrid Silica Research Articles

Microfluidic Precision Manufacture of High Performance Liquid Chromatographic Microspheres

AbstractA key bottleneck in developing chromatographic material is the chemically entangled control of morphology, pore structure, and material chemistry, which holds back precision material manufacture in order to pursue advanced separation performance. In this work, a precision manufacture strategy based on droplet microfluidics was developed, for production of highly efficient chromatographic microspheres with independent control over particle morphology, pore structure and material chemistry. The droplet‐synthesized microspheres display extremely narrow particle size distribution (CV<3 %), enabling a 100 % production yield due to complete elimination of sieving steps. More importantly, the size of the droplet‐synthesized microspheres is freely adjustable without the need for re‐optimizing chemical recipes or reaction conditions. The resulting materials exhibit excellent separation efficiencies, achieving a reduced plate height of hmin=1.67. This precision manufacture strategy also allows for flexible pore design and continuous pore size adjustment across three orders of magnitudes, providing a novel vehicle for resolution fine‐tuning targeting protein separation. Besides traditional silica, organic–inorganic hybrid silica, zirconia, and titania microspheres can also be precisely synthesized on the same platform, supporting various separation applications and operating conditions. Powered by precision manufacture, super‐throughput production, and versatile chemistry, the high‐performance droplet‐synthesized separation material will pave the way towards green and precision chromatographic industry.

Microfluidic Precision Manufacture of High Performance Liquid Chromatographic Microspheres.

A key bottleneck in developing chromatographic material is the chemically entangled control of morphology, pore structure, and material chemistry, which holds back precision material manufacture in order to pursue advanced separation performance. In this work, a precision manufacture strategy based on droplet microfluidics was developed, for production of highly efficient chromatographic microspheres with independent control over particle morphology, pore structure and material chemistry. The droplet-synthesized microspheres display extremely narrow particle size distribution (CV<3 %), enabling a 100 % production yield due to complete elimination of sieving steps. More importantly, the size of the droplet-synthesized microspheres is freely adjustable without the need for re-optimizing chemical recipes or reaction conditions. The resulting materials exhibit excellent separation efficiencies, achieving a reduced plate height of hmin=1.67. This precision manufacture strategy also allows for flexible pore design and continuous pore size adjustment across three orders of magnitudes, providing a novel vehicle for resolution fine-tuning targeting protein separation. Besides traditional silica, organic-inorganic hybrid silica, zirconia, and titania microspheres can also be precisely synthesized on the same platform, supporting various separation applications and operating conditions. Powered by precision manufacture, super-throughput production, and versatile chemistry, the high-performance droplet-synthesized separation material will pave the way towards green and precision chromatographic industry.

Mesoporous silica-confined ultrafine ruthenium nanoparticles supported by graphene: Robust catalysts for biphasic oxidation at the oil-water interface

Graphene-supported ultrafine ruthenium nanoparticles covered by mesoporous silica (mSiO2) were synthesized as interfacially active catalysts for biphasic oxidation at the oil-water interface. These mesoporous SiO2 layers serve to confine metal nanoparticles of specific sizes, preventing their sintering even under harsh conditions, which is attributed to the confinement effects within porous materials. Furthermore, Pickering emulsion systems formulated with these amphiphilic catalysts exhibit significantly higher catalytic efficiency compared to conventional organic-aqueous biphasic systems with Ru/rGO and commercial Ru/C catalysts. The catalytic performance is directly influenced by surface wettability, and the catalytic efficiency reveals a parabolic distribution with respect to the content of mSiO2, indicative of the optimal activity over Ru/rGO@mSiO2-100 with a conversion of up to > 92 % and a selectivity to benzaldehyde of up to > 99 % under base-free conditions after 2 h. Moreover, rGO–silica hybrids demonstrate the excellent reusability for over five cycles which benefits from the protective effect of mSiO2.

Diffusion Behavior of Organic Solvents in Graphene Oxide/Nano Silica Hybrid Natural Rubber Latex Nanocomposite: Experimental and Theoretical Approach

AbstractThis study explores the impact of a graphene oxide (GO)/nano silica (NS) hybrid (GO/NS) filler on the diffusion characteristics of natural rubber (NR) composites when exposed to toluene, xylene, and hexane solvents. The lowest solvent uptake is observed for NR GO/NS 3 (3 phr), which is attributed to forming a robust filler network within the composite. The calculation of crosslink density using the Flory‐Rehner equation reveals significantly higher values for NR GO/NS 3, indicating good crosslinking density in the presence of the hybrid filler. Furthermore, molecular mass between crosslinks (Mc) is calculated, demonstrating a favorable fit with the Affine model. The investigation extends to theoretical modeling, where the Korsemeyer–Peppas and Peppas–Sahlin models are employed to predict solvent uptake behavior. Strikingly, the experimental values exhibit a strong alignment with the Peppas–Sahlin model. This comprehensive analysis provides valuable insights into the diffusion behavior of graphene oxide/nano silica (GO/NS) hybrid‐reinforced natural rubber latex in organic solvents, highlighting potential applications in areas such as solvent‐resistant coatings, barrier materials for chemical storage, and enhanced performance in protective gloves and seals used in harsh chemical environments.

Plant-mediated synthesis, characterization, and evaluation of a copper oxide/silicon dioxide nanocomposite by an antimicrobial study

Abstract This study presents an innovative, environmentally friendly method for biosynthesizing copper oxide–silica (Cu2O/SiO2) nanocomposites (CSNCs) utilizing an aqueous leaf extract of Callistemon viminalis (C. viminalis). The goal of this work is to fabricate CSNCs using a less hazardous and sustainable synthesis approach. Copper acetate and sodium metasilicate were used as precursors, whereas the C. viminalis green leaf extract was used as the reducing and stabilizing agent. Analysis of the plant extract using Fourier transform infrared spectroscopy indicated the presence of polyphenolic compounds, primarily phenolic acids, which functioned as both reducing and stabilizing agents in the synthesis of CSNCs. A combination of energy dispersive X-ray spectroscopy and scanning electron microscopy was used to study the formation of spherical copper–silica hybrid nanostructures. Powder X-ray diffraction analysis revealed the successful integration of silica with copper(i) oxide (Cu2O) through the presence of distinct Cu2O peaks and a broad amorphous SiO2 peak at 2θ = 22.77°. The thermal stability of the nanocomposites (NCs) was assessed using thermogravimetric analysis and differential thermal analysis under a nitrogen atmosphere. The biogenic NCs also successfully inhibited pathogenic strains of Staphylococcus aureus (S. aureus) and Candida albicans (C. albicans); however, S. aureus was found to be more susceptible to the biocidal activity of the NCs than P. aeruginosa. These findings suggest that this simple, cost-effective, and eco-friendly method for producing biologically active hybrid nanomaterials holds significant promise for future applications in both biological and materials sciences.

Enhanced Thermal Conductivity and Stability of Hydrated Salt Phase Change Microcapsules With GO/SiO2 Hybrid Shell for Battery Thermal Management

AbstractHerein, the synthesis of a novel microencapsulated phase change material via a sol–gel method is presented, featuring disodium hydrogen phosphate dodecahydrate as the core and a SiO2/graphene oxide composite as the shell. The morphology and core–shell microstructure of the synthesized microcapsules are characterized using scanning electron microscopy. The phase change performance and thermal stability are evaluated by differential scanning calorimetry and a high/low temperature test chamber, respectively. Energy dispersive X‐ray spectroscopy and Fourier transform infrared spectroscopy are employed to determine the chemical composition of the microcapsules. The findings reveal that the MEPCM exhibited a high melting enthalpy of 174.3 J g−1. The degree of supercooling is reduced by 2.1 °C, and after 600 thermal cycles, the phase change enthalpy of the microcapsules showed a minor decrease of ≈6.0%. Notably, the thermal conductivity of the microcapsules is significantly enhanced, increasing by up to 51.8%. When integrated into the thermal management systems of lithium‐ion batteries, the MEPCM effectively maintained the battery temperature below 46 °C under a 3 C charging rate. In summary, these results suggest that the hydrated salt microcapsule with its hybrid silica and graphene oxide shell is a promising material for the thermal management of lithium‐ion batteries.

Development and Application of an Advanced Percolation Model for Pore Network Characterization by Physical Adsorption.

Physical adsorption is one of the most widely used techniques to characterize porous materials because it is reliable and able to assess micro- and mesopores within one approach. Challenges and open questions persist in characterizing disordered and hierarchically structured porous materials. This study introduces a pore network model aimed at enhancing the textural characterization of nanoporous materials. The model, based on percolation theory on a finite-sized Bethe lattice, includes all mechanisms known to contribute to adsorption hysteresis in mesoporous pore networks. The model accounts for delayed and initiated condensation during adsorption as well as equilibrium evaporation, pore blocking, and cavitation during desorption. Coupled with dedicated nonlocal-density functional theory kernels, the proposed method provides a unified framework for modeling the entire experimental adsorption-desorption isotherm, including desorption hysteresis scans. The applicability of the method is demonstrated on a selected set of nanoporous silica materials exhibiting distinct types of hysteresis loops (types H1, H2a, H1/H2a, and H5), including ordered mesoporous silica networks (KIT-6 and SBA-15/MCM-41 hybrid silica with plugged pores) and disordered mesoporous silica networks (hierarchical meso-macroporous monolith and porous Vycor glass). For all materials, a good correlation is found between calculated and experimental primary isotherms as well as desorption scans. The model allows us to determine key pore network characteristics such as pore connectivity and pore size distributions as well as a parameter correlated with the impact of pore network disorder on the adsorption behavior. The versatility and enriched textural insights provided by the proposed novel network model allow for a comprehensive characterization previously inaccessible and hence will contribute to further advancement in the textural characterization of novel nanoporous materials. It has the potential to provide important guidance for the design and selection of porous materials for optimizing various applications, including separation processes such as chromatography, heterogeneous catalysis and gas and energy storage.

Tuneable mesoporous silica material for hydrogen storage application via nano-confined clathrate hydrate construction

Safe storage and utilisation of hydrogen is an ongoing area of research, showing potential to enable hydrogen becoming an effective fuel, substituting current carbon-based sources. Hydrogen storage is associated with a high energy cost due to its low density and boiling point, which drives a high price. Clathrates (gas hydrates) are water-based (ice-like) structures incorporating small non-polar compounds such as H2 in cages formed by hydrogen bonded water molecules. Since only water is required to construct the cages, clathrates have been identified as a potential solution for safe storage of hydrogen. In bulk, pure hydrogen clathrate (H2O-H2) only forms in harsh conditions, but confined in nanospaces the properties of water are altered and hydrogen storage at mild pressure and temperature could become possible. Here, specifically a hydrophobic mesoporous silica is proposed as a host material, providing a suitable nano-confinement for ice-like clathrate hydrate. The hybrid silica material shows an important decrease of the pressure required for clathrate formation (approx. 20%) compared to the pure H2O-H2 system. In-situ inelastic neutron scattering (INS) and neutron diffraction (ND) provided unique insights into the interaction of hydrogen with the complex surface of the hybrid material and demonstrated the stability of nano-confined hydrogen clathrate hydrate.

Pt supported on modified-coal gasification slag for efficient dehydrogenation of methylcyclohexane in a fixed bed reactor

Coal gasification slag (CGS) was used for modification and loaded platinum (Pt) to liquid organic hydrogen carrier (LOHC) for the first time. The carbon hybrid silica (C/SiO2) was prepared by removing metal oxides and carbon residue of CGS through acid treatment and calcination. The C/SiO2 loaded Pt (Pt-C/SiO2) exhibited only a 1.3% decrease in dehydrogenation conversion rate after 30 h of continuous catalytic dehydrogenation of methylcyclohexane (MCH), and even after 100 h, the decrease was only 4.9%. When Pt was directly loaded on CGS (Pt-CGS), it showed higher catalytic activity (dehydrogenation conversion rate was 20.4%), but lower catalytic stability (dehydrogenation conversion rate decreased by 56% after 7 h). Additionally, commercial Pt-SiO2 catalysts exhibited poor dehydrogenation conversion rate, significantly lower than that of Pt-C/SiO2. Density functional theory calculations confirmed the influence of carbon hybrid SiO2 on the adsorption energy, electron transfer and density of states for the catalytic dehydrogenation of MCH. The highly active and stable Pt-C/SiO2 catalyst can be effectively utilized for LOCH while achieving high-value utilization of CGS solid waste.

Organic-Inorganic Hybrid Silica Film with a TGBA* Structure.

Twisted grain boundary (TGB) phases exhibit highly frustrated and complex liquid crystal structures, and have attracted enormous interest because of their unique internal structure, textures and properties. However, among the few real concerns related to these interesting structures, applying them to prepare polymer-stabilized colored liquid crystal films has been challenging. Herein, the organic-inorganic hybrid silica (OIHS) films with a TGBA* structure were prepared using two organosilanes and one chiral additive under an acidic condition. The structural color of the films can be adjusted by varying the polycondensation temperature and the concentration of the chiral additive. A structurally colored pattern was prepared by the inject printing, which was suitably applied for decoration and anti-counterfeiting.

Ultrahigh-Performance Supercritical Fluid Chromatography-Mass Spectrometry in the Clinical Lipidomic Analysis.

Ultrahigh-performance supercritical fluid chromatography-mass spectrometry (UHPSFC/MS) method is optimized for the high-throughput quantitation of lipids in human serum and plasma with an emphasis on robustness and accurate quantitation. Bridged ethylene hybrid (BEH) silica column (100×3mm; 1.7μm) is used for the separation of 17 nonpolar and polar lipid classes in 4.4min using the positive ion electrospray ionization mode. The lipid class separation approach in UHPSFC/MS results in the coelution of all lipid species within one lipid class in one chromatographic peak, including two exogenous internal standards (IS) per lipid class, which provides the optimal conditions for robust quantitation. The method was validated according to European Medicines Agency and Food and Drug Administration recommendations. UHPSFC/MS combined with LipidQuant software allows a semiautomated process to determine lipid concentrations with a total run time of only 8min including column equilibration, which enables the analysis of 160 samples per day.

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.

Graphene Oxide-Silica Green Hybrid Nanocomposites: Fabrication via Latex Mixing and Mechanical Properties Evaluation

ABSTRACT This study investigates the incorporation of sustainable self-assembled graphene oxide-nano silica (GO/NS) hybrid nanoparticles into the natural rubber latex matrix via latex mixing. The primary objective is to assess the synergistic impact of these nanofillers on the mechanical properties of natural rubber latex using both static and dynamic mechanical analysis. Results reveal significant enhancements in mechanical properties, with NRL GO/NS 2 exhibiting a remarkable 188% increase in tensile strength and NRL GO/NS 3 showing a substantial 107% increase. Furthermore, NRL GO/NS 3 demonstrates a 30% reduction in rolling resistance and a remarkable 200% improvement in wet grip, while NRL GO/NS 2 exhibits an 88% increase in wet grip and a 43% decrease in rolling resistance, suggesting potential fuel efficiency benefits. These advancements hold promise for various applications such as automotive tire manufacturing, biomedical devices, and the production of elastomeric goods.

Green synthesis of sacrificial UV-sensitive core and biobased shell for obtaining optically hollow nanoparticles

Hollow nanoparticles have been extensively studied in recent years. Obtaining such structures with biobased materials, following greener synthetic routes, is still challenging, especially if accurate particle dimensions are required. This work reports the use of an innovative hybrid silica core (Si@azo) containing UV-sensitive molecule, wrapped in biobased multilayer shell composed of polysaccharides. It is a promising strategy for obtaining optically hollow nanoparticles. Indeed, Si@azo cores have the ability to be partially degraded when irradiated with UV light. Combined with a well-controlled and monodisperse diameter, they provide a good basis for layer-by-layer assembly, leading to a multilayer shell with controlled composition and thickness. Finally, UV irradiation of such a core–shell structure is harmless to the polysaccharide shell, but does impact the hybrid silica core, as revealed by turbidity measurements, among other. Each step, i.e. core synthesis, shell addition, and core–shell irradiation, has been carefully characterized at the macro (Fourier-transform infrared spectroscopy – FTIR, Dynamic Light Scattering – DLS, Zeta-potential measurement, Surface Plasmon Resonance – SPR, turbidity) and microscale (Transmission and Scanning Electron Microscopies). Emphasis is put on how turbidity measurements can be related to the core refractive index (ncore), giving information on the state of core degradation and whether the core–shell particle is optically hollow.

Sustained Antibiotic Release from Biodegradable Gelatin–Silica Hybrid for Orthopedic Infections

AbstractAntibiotic‐loaded polymethylmethacrylate (PMMA) beads are commonly employed to treat prosthetic joint infections (PJI) and chronic osteomyelitis due to their excellent mechanical strength. However, PMMA's non‐degradability results in a burst release of antibiotics and potential renal toxicity, necessitating additional surgeries for bead removal. There is a critical need for infection control materials that can deliver antibiotics effectively, maintain adequate mechanical strength, and degrade uniformly. This study introduces a gelatin–silica hybrid antibiotic carrier, characterized by covalent bonds between the gelatin and silica networks. The incorporation of the silica network enhances the compressive strength to 32.53 ± 2.4 MPa and ensures uniform degradation over 6 months, aligning with clinical timelines. Furthermore, the gelatin–silica hybrid can support up to 10 wt% antibiotic loading without compromising its properties, making it a promising candidate for next‐generation infection control materials.

Enhancing cement-based composites via regulated hydration and concurrent construction of robust organic-inorganic network

Cement-based materials with excellent mechanical properties are in high demand in the civil engineering. This work utilized an innovative in-situ copolymerization approach for synergistic modification of cement-based materials. Vinyl hybrid silica microspheres (VSM) were synthesized through the sol-gel method. Subsequently, With the assistance of initiators and cross-linking agents, the VSM and acrylamide (AM) in-situ copolymerization and were uniformly dispersed in the cement matrix, leading to the successful development of a modified cement-based material. The copolymerization of VSM and AM resulted in the creation of a comprehensive three-dimensional hybrid network structure, interconnected by covalent bonds between the constituent components. Experimental results unequivocally demonstrate that the mechanical properties of the composite have undergone remarkable enhancement. Notably, the flexural strength experienced a substantial increase due to the in-situ polymerization of AM. Furthermore, the compressive strength was significantly improved, achieving a 21.4 % increase compared to samples modified with 2 wt% AM alone. The enhancement can be attributed to the synergistic effect of the in-situ copolymerization structure and the VSM attached to it. The microspheres not only aided in the development of a robust cement matrix and a higher compactness, but also bolstered the compressive modulus of the flexible polymer chains. Collectively, these factors contributed to an increase in the overall resistance to deformation, comprehensively enhancing the mechanical performance of the material. This study addresses the challenges posed by the loss of compressive strength during in-situ polymerization modification, introduces an innovative methodology aimed at significantly enhancing the mechanical properties of cement-based materials.

Development of L‐Aspartic Acid Decorated Core/Shell Silica Particles for Adsorption of Hyaluronic Acid

AbstractIn this study, core/shell‐structured mesoporous hybrid silica gel particles were synthesized for the selective adsorption of hyaluronic acid. A non‐ionic amphiphilic polymer core consisting of poly(methyl methacrylate) and poly(ethylene glycol) blocks were coated with SiO2 using the Stöber method in the presence of non‐ionic and cationic surfactants to obtain mesoporous core‐shell silica particles. The surface of silica particles was functionalized through modification of L‐aspartic acid to improve their affinity against the targeted analyte, hyaluronic acid. Physico‐chemical methods including Fourier transform infrared spectroscopy, thermal gravimetric analysis, zeta‐size measurements, and transmission‐ and scanning‐electron microscopies were utilized to evaluate the properties of core‐silica particles. The surface functionalized core/shell particles have an average size of 254.7 (±33.1) nm as confirmed by TEM analysis. The hyaluronic acid adsorption performance of the modified core‐shell silica particles was optimized through varying pH, concentration, temperature, and contact time parameters. Thermodynamic parameters were estimated by applying adsorption isotherm and kinetics models to assess the favorability of the adsorption process. The models revealed that the hyaluronic acid adsorption processes follow monolayer adsorption (Langmuir model) and chemisorption (pseudo‐second‐order kinetics) processes.

Development of a hydrogen permselective silica membrane and its application to the thermochemical water splitting method

Abstract The thermochemical water splitting IS process is one of the hydrogen production method to use a heat directly. The temperature of the thermal decomposition of water (4000 K) can be reduced under 700 K by introducing I2 and SO2 as recycling catalysts. One of the problems in the IS process is that the conversion of the HI decomposition reaction is low at about 20%. If a membrane reactor with the H2 permselective membrane is applied to the HI decomposition reaction, the hydrogen can be extracted to improve the HI conversion. We focus on a counter diffusion CVD method for the preparation method of the membranes. Two reactants (e.g. silica precursor and oxidant) are provided at the opposite side of the porous substrates and hybrid silica is deposited inside the pore of the substrate. The pore sizes are controlled by introducing organic functional groups to silica precursor. In this study, the silica hybrid membrane with high H2 permeation performance and high H2/HI selectivity were developed by introducing organic functional groups. Effects of the organic functional groups were summarized by using a pore model. The HI gas and other inorganic gases permeation performance were tested through silica hybrid membranes.

Feasibility of Sprayable Engineered Cementitious Composites Using Natural Sand and Low Fiber Content: Effect of Hybrid Fiber System, Silica Fume, and Air-Entraining and Shrinkage-Reducing Admixtures

Deterioration of corrugated steel culverts (CSCs) is a significant problem for the Virginia Department of Transportation and other U.S. transportation agencies. Spray-on lining using shotcrete engineered cementitious composites (ECCs) is a promising structural repair strategy for deteriorated CSCs. This study evaluates the feasibility of practical sprayable ECCs using natural silica sand and low fiber content, while forgoing the use of commonly utilized calcium sulfoaluminate cement to allow for delivery of the materials via ready-mixed concrete trucks. Aspects of the compositional space evaluated include the effect of a hybrid polyvinyl alcohol/polyethylene fiber system, silica fume (SF), shrinkage reducing admixture (SRA), and air-entraining admixture (AEA) on the properties of the composites. Experimental results suggested that the development of the proposed materials is feasible, because flow characteristics associated with shotcrete ECCs and ECC-like tensile ductility were achieved in the fresh and hardened state, respectively. Notwithstanding, further mixture optimization may be required for satisfactory field performance, which should be assessed through field testing. Generally, the use of the hybrid fiber system tended to improve the strength and ductility of the composites, especially when coupled with the use of SF. Furthermore, SF was effective at mitigating the strength loss associated with the incorporation of AEA and SRA, and meaningfully improved surface resistivity. SF also tended to reduce the mixture’s flow, whereas the contrary occurred with the use of SRA and AEA. SRA contributed to the reduction in drying shrinkage at early ages. However, the effect of SRA in reducing shrinkage was negligible at later ages.

Remediation of Neonicotinoid Polluted Environment by Silica Hybrid Nanosorbents

Remediation of Neonicotinoid Polluted Environment by Silica Hybrid Nanosorbents