Unmodified Silica Research Articles

Tri-functionally modified spherical silica for high-performance epoxy resin sealant

The integration of inorganic nanoparticles as reinforcement imparts epoxy resin with outstanding comprehensive performance, facilitating the utilization across diverse applications spanning coatings, adhesives, and composites. However, the persistent challenge lies in achieving optimal interfacial compatibility between the fillers and the resin matrix. This study focuses on the synthesis of tri-functionally modified spherical silica particles with an average size of 700 nm by empolying three distinct types of silane coupling agents in a synergistic manner to achieve desired functionalization. These agents endow the resulting particles with reactive groups, including epoxy and amine functionalities, which enhance interfacial compatibility and adhesion between the silica particle fillers and the epoxy resin matrix. Additionally, the incorporation of non-reactive phenyl groups serves to reduce the viscosity of resin composites. These modified silica particles are integrated into the sealant formulations, which exhibits commendable reliability and processability. It exhibits a 95 % reduction in moisture permeability, an increase in glass transition temperature by approximately 30 °C, and a decrease in coefficient of thermal expansion by 5∗10−6/k, compared to the sealant prepared with unmodified silica. The outcomes of this research present promising avenues for the advancement of cutting-edge display technologies.

Unraveling the Complexities of Silica Nanoparticle Adsorption onto Polymer Latexes in Pickering Emulsion Polymerization.

Incorporating unmodified silica nanoparticles onto polymer latexes to fabricate aqueous polymer dispersions without relying on electrostatic attraction during the Pickering emulsion polymerization process still faces challenges. For negatively charged silica nanoparticles to successfully adsorb onto polymer latexes, particularly in an anionic initiator emulsion polymerization system, they have remained elusive without the use of auxiliary monomers and cationic initiators. This study investigates various experimental parameters, such as emulsion polymerization temperature, monomer solubility, salt concentration, and cation type, to elucidate the factors influencing the adsorption of unmodified silica nanoparticles in Pickering emulsion polymerization. While poly(methyl methacrylate) (PMMA)/SiO2 hybrid latexes can be obtained under pH conditions of 5-6 and at temperatures of 65 °C or below, the loading rate of silica nanoparticles decreases as the reaction temperature increases, resulting in bare PMMA latexes without silica nanoparticle adsorption at temperatures exceeding 70 °C. Introducing styrene (St) into the monomer mixture with methyl methacrylate in a ratio of up to 10 wt % leads to a gradual decrease in silica nanoparticle loading rate, from 27.3 to 8.2 wt %, attributed to the low solubility of St in water. Furthermore, the presence of sodium ions (Na+) is found to be crucial for silica nanoparticle adsorption onto PMMA latexes, as the sodium ions have a stabilizing effect on both the silica nanoparticles and the silica nanoparticle-armored latexes. These findings highlight the complex nature of Pickering emulsion polymerization in the presence of unmodified silica nanoparticles, demonstrating that the loading rate of silica nanoparticles onto polymer latexes is influenced by various factors. These insights pave the way for developing aqueous polymer dispersions with high silica nanoparticle loading rates onto polymer latexes, which is a desirable trait in the coating industry.

The retention features of nitrogen-containing heterocyclic compounds in reversed-phase and hydrophilic HPLC-MS modes

Aromatic five- and six-membered nitrogen-containing heterocyclic compounds are biologically active substances and are widely used in biochemistry and medicine. In addition, such compounds are known as ecotoxicants formed during oxidation processes in industrial wastewater. High-performance liquid chromatography-mass spectrometry is widely used to determine nitrogen-containing heterocycles in various complex mixtures. Octadecyl silica gel is the main sorbent for chromatographic separation. However, octadecyl silica gel does not always enable satisfactory separation in the presence of highly polar isomeric molecules, and more selective chromatographic approaches are required. One of these is hydrophilic chromatography, which facilitates the separation of polar compounds. The aim of the study was to comparatively characterize the retention of a number of five- and six-membered nitrogen-containing heterocyclic compounds during reversed-phase and hydrophilic liquid chromatography with mass spectrometric detection. In addition, spectrophotometric detection at a wavelength of 210 nm was carried out. In the study, we used sorbents based on octadecyl silica gel and unmodified silica gel. High-resolution mass spectrometry was used in the electrospray ionization mode. We studied 19 nitrogen-containing heterocyclic compounds. We used aqueous acetonitrile mobile phases with added aqueous solutions of formic acid and diethylamine as acid-base modifiers. An ammonium formate solution was used as a modifier during hydrophilic chromatography. Reversed-phase chromatography showed that the introduction of 0.1% aqueous formic acid solution increased the ionization and the mass spectrometer signal intensity, but did not always result in a satisfactory separation of isomers upon elution from the octadecyl silica gel surface. The introduction of 0.01% diethylamine solution provided no significant improvement in the separation compared to the mobile phase without modifiers. The use of unmodified silica gel in hydrophilic chromatography mode allowed us to separate isomeric five-membered heterocycles, which was demonstrated by narrow symmetric peaks, but did not result in selective separation of isomeric diazines. Thus, we studied the retention of 19 nitrogen-containing heterocyclic compounds using reversed-phase and hydrophilic liquid chromatography with electrospray ionisation. It was determined that hydrophilic chromatography on unmodified silica gel could be used for satisfactory separation of isomeric five-membered heterocyclic compounds of different classes. For six-membered heterocycles, satisfactory separation was achieved by elution from the surface of octadecyl silica gel using aqueous acetonitrile mobile phase without modifiers.

Synthesis and study of organo-modified silica based hydrogels: Rheological properties and drug release kinetics.

The method of synthesis of unmodified and organo-modified silica hydrogels and their composites with orotic acid as a model drug was developed. The hydrogels had a pH of 6.5-7.8. The particulate nature and highly porous structures of the hydrogel materials were revealed using scanning electron and optical microscopy methods. The content of aqueous phase in the hydrogels was 99% or more. In order to evaluate the possibility of their application as a basis for development of novel soft drug formulations and cosmetic compositions, rheological properties of the hydrogels and in vitro release kinetics of the drug were studied. The effects of synthesis conditions (increasing concentration of catalyst of silica sol formation, drug loading) and the silica matrix modification with various organic groups on the indicated properties were investigated. It was found that all synthesized hydrogels exhibited pseudoplasticity, thixotropy and controlled release of the drug, which are important for their potential application. However, in general, the indicated effects led to worsening the properties of the hydrogel materials in comparison with the unmodified silica hydrogels.

Effect of Pore Confinement of Ionic Liquids on Solute Diffusion within Mesoporous Silica Microparticles.

The transport properties of the ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) confined within silica microparticles with well-ordered, accessible mesopores (5.4 or 9 nm diameter) were investigated. [BMIM][PF6] confinement was confirmed by using differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy. The transport properties of the confined IL were studied using the neutral and cationic fluorescent probes 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM) and rhodamine 6G, respectively, through fluorescence recovery after photobleaching (FRAP) in confocal microscopy. The diffusivity of DCM in 9 nm pores is 0.026 ± 0.0091 μm2/s, which is 2 orders of magnitude less than in the bulk ionic liquid. The pore size did not affect the diffusivity of DCM in unmodified silica nanopores. The diffusivity of the cationic probe is reduced by 63% relative to that of the neutral probe. Diffusivity is increased with water content, where equilibrium hydration of the system leads to a 37% increase in DCM diffusivity. The most dramatic impact on diffusivity was caused by tethering an IL-like methylimidazolium chloride group to the pores, which increased the pore hydrophobicity and resulted in 3-fold higher diffusivity of DCM compared to bare silica pores. Subsequent exchange of the chloride anion from the tethering group with PF6- decreased the diffusivity to half that of bare silica. The diffusion of probe molecules is affected most strongly by the pore wall effects on probe interactions rather than by the pore size itself, which suggests that understanding pore wall diffusion is critical to the design of nanoconfined ILs for separations, catalysis, and energy storage.

Hydrophobic PI/SiO2 composites with excellent dielectric property and thermal stability via simple modification

Polyimide (PI) has been extensively used in 5G microelectronics however the relatively high dielectric constant (∼3.5) and moisture adsorption have greatly limit its practical applications in high-frequency region. Here hydrophobic PI/SiO2 composite films with low dielectric constant and excellent thermal stability were synthesized by dispersing methyl modified hollow silica nanospheres (MHS) into polyamic acid solution prior to imidization treatment. Comparing with unmodified hollow silica nanospheres (HS), the MHS obtained through methyl modification can disperse uniformly in the PI matrix. Thus, the relaxation and orientation polarization of the PI chains as well as their electron migration are suppressed, resulting in a significant decrease in dielectric constant. The PI/MHS-10% film exhibits a stable low dielectric constant (1.9–2.3) in the high-frequency range (8.2 GHz–12.4 GHz), meanwhile maintains a high breakdown voltage (192 kV/mm), mechanical properties (64 MPa) and an excellent thermal stability (Td5% = 546.5 °C; Tmax = 589.0 °C). Moreover. PI/MHS demonstrates much lower linear expansion coefficient of 25.0 ppm/K that better matches the substrate. The surface contact angle of PI/MHS increases from 73° to 110° and the water absorption rate decreases from 3.1% to 1.6%, effectively avoiding the moisture adsorption. This work provides a simple method to prepare high-performance composite films for 5G practical applications.

Effect of silica type, content, and silanization on the curing, mechanical and energy dissipation properties of poly (epichlorohydrin-co-ethylene oxide-co-allyl glycidyl ether) elastomers

This work aimed to determine the effect of unmodified raw silicas and modified silicas with silane coupling agents on the curing, mechanical, and energy dissipation properties of poly (epichlorohydrin-co-ethylene oxide-co-allyl glycidyl ether) based elastomers. The modified silicas utilized include Coupsil 6109, Coupsil 8113, and Coupsil VP6411, while the unmodified silicas are Ultrasil VN2 and VN3. Adding modified silicas increased the optimum curing time and decreased the cure rate index up to a silica content of 20 phr. However, the cure rate index increased with the addition of 40 phr silica. Mechanical testing of the compounds highlighted the impact of silica addition on the reinforcement of the rubber matrix. The incorporation of silica resulted in enhanced mechanical properties, including increased tensile strength, elongation at break, and elastic modulus. The compression behavior of the vulcanized compounds is also analyzed. The results show that the modified silicas with silane coupling agents exhibit lower relative hysteresis loss than the unmodified silicas, highlighting their potential for reducing energy dissipation and improving mechanical efficiency. Additionally, the storage modulus (G') values of the unmodified silicas (VN2 and VN3) are higher than those of the silanized silicas. However, in compounds prepared with 20 phr silica, the differences in storage modulus (G') between the modified and unmodified silicas are minor. Overall, the findings highlight the influence of modified silicas with silane coupling agents and unmodified silicas on the properties of PECH elastomer, providing insights into optimizing silica content for desired material characteristics.

Dendrimer Coated Silica as a Sorbent for Dispersive Solid-Phase Extraction of Select Non-Steroidal Anti-Inflammatory Drugs from Water.

Non-steroidal anti-inflammatory drugs (NSAIDs) have been recognized as a potentially serious threat to the natural environment. NSAIDs are popular painkillers, and the main pathway for them to reach natural water is via discharge from wastewater and sewage treatment plants. In order to monitor contamination caused by these drugs, as well as their impact on the environment, a new material based on Silica Gel 60, functionalized with a dendrimeric copolymer of methylamine and 1,4-butanediol diglycidyl ether (named MA-BDDE), was prepared. Initial physicochemical characterization of the MA-BDDE material was carried out using ATR FT-IR spectroscopy as well as solid-state carbon-13 NMR spectroscopy. Its effectiveness at NSAID extraction was evaluated by the application of five select drugs in dispersive solid-phase extraction (dSPE): aspirin, ketoprofen, naproxen, diclofenac and ibuprofen. This was followed by their simultaneous determination using the HPLC-UV/Vis system demonstrating good sensitivity, with limits of detection values within the 63-265 ng mL-1 range. A comparison of the sorption capacity of each pharmaceutical with unmodified base silica showed an at least tenfold increase in capacity after modification. Initial MA-BDDE application in a quick, low-waste extraction procedure of those select NSAIDs from spiked surface water samples yielded promising results for its use as a sorbent, as recovery values of analytes adsorbed from various samples were found to exceed 72%.

Nanostructure and thermal characteristics of silica/human serum albumin systems based on a modified nanosilica entero-vulnerosorbent.

Entero-vulnerosorbents based on geometrically modified (GM) (mechanical treatment at different times, tMT = 1, 4, and 7 h) fumed nanosilica A300 (NS) and protein molecules (human serum albumin/GM-nanosilica systems) were characterized with a focus on their surface, morphology, topography, and thermal properties. Microscopic, spectroscopic, and analytical techniques, including atomic force microscopy (AFM), optical profilometry (OP), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and elemental analysis (CHN), were used. The differentiation in the surface morphology, micro-nanoroughness, surface chemistry, thermal properties of the silica support, and protein/nanosilica systems were found. AFM, OP, and HRTEM microscopic methods showed that the albumin/silica composite surface is less rough, wavy, and asymmetrical; it is also smoother, flat, and homogeneous because of the formation of a continuous layer of a protein film on the support surface. CHN, XPS, and S/TEM-EDX analysis showed that HSA adsorbed on the unmodified and GM-treated silica carrier led to variations in the physical and chemical features of materials (elemental composition, element concentration, chemical states, chemical bonds between enzyme molecules, and silica surface). Thermal studies were carried out using a thermogravimetric technique linked with a quadrupole mass spectrometer (TG/DTG/DSC-QMS). The degradation of the HSA/nanosilica system is a two-stage process that takes place within the temperature range 160-450-900 °C.

A facile route to the synthesis of carbon replicas cast from narrow-mesoporous matrices

Carbon replicas find a variety of applications in chemical sciences and even in medicine. However, tedious synthesis hinders their application to the laboratory scale hitherto. Here, we develop a facile procedure for the synthesis of CMK-1 and CMK-2 materials cast from narrow-mesoporous hard templates, i.e. MCM-48 and SBA-1, respectively. The proposed recipe is reproducible, operates under mild conditions using basic laboratory equipment and a renewable carbon source (furfuryl alcohol). It relies on the solvent-polarity-controlled deposition of a polar carbon precursor on unmodified silica in a non-polar medium. Such a self-regulating process provides even coverage of the matrix with polymer leading to the formation of carbon mesostructures of exquisite replication fidelity and structural homogeneity while maintaining the primary morphology. The in-depth study of physisorption data employing the dual gas model (simultaneous N2 and CO2 fitting) disclosed the mixed, micro-mesoporous nature of the materials. This tool was found to provide a fair, comprehensive textural characterization, especially useful for materials with pore sizes on the boundary between micro- and mesopores. Therefore, this research paves the way for the manufacturing and application of CMK-1 and CMK-2 carbon replicas on a larger scale. Additionally, it provides certain hints for the robust textural characterization of such materials.

Functionalization of mesoporous silica with oligoisoprene brushes: Application as charge for elastomers reinforcement

The interfacial interaction between mesoporous silica nanoparticles (MSN) and natural rubber was successfully improved by surface modification of hydrophilic silica using oligoisoprene brushes. This approach involved grafting 3-aminopropyltriethoxy silane (APTES) onto the silica surface, achieving a grafting efficiency of 13.22 % and generating amine groups. The long polyisoprene chains of natural rubber were selectively cleaved using an optimized oxidative reaction, resulting in the formation of short oligomers with carbonyl chain ends known as Carbonyl Telechelic Natural Rubber (CTNR), having a molecular weight of 4100 g/mol. The CTNR oligomers were subsequently linked to APTES-modified silica via a Schiff's base reaction, imparting hydrophobicity to the silica surface and enhancing its compatibility and dispersion within the natural rubber matrix. Two conditions, MSN@CTNR1 and MSN@CTNR2, were investigated, exhibiting grafting efficiencies of 10.66 % and 4.70 %, respectively. The functionalized silica particles from MSN@CTNR1 were examined and incorporated at varying proportions into rubber latex, leading to the formation of thin films. Surprisingly, films containing 1 part per hundred rubber (phr) functionalized silica had better mechanical and thermal properties than films containing unmodified silica. This study underscores the potential of MSN, whose surfaces are modified by grafting oligoisoprene brushes, to enhance the crosslinking points and serve as innovative additives in the formulation of composite rubber films. Furthermore, these findings highlight the prospects of utilizing modified silica nanoparticles as coating additive materials, enabling the enhancement of properties and performance in rubber-based composites, thereby paving the way for the development of advanced coating applications in diverse industries.

Effect of Drying Control Agent on Physicochemical and Thermal Properties of Silica Aerogel Derived via Ambient Pressure Drying Process

This paper presents the effect of drying control agents on the physicochemical and thermal properties of hydrophobic silica aerogels derived via the ambient pressure drying (APD) method by a surface silylation using a TMCS/n-hexane mixture. The structural and physicochemical properties of synthesized DMF-modified and unmodified hydrophobic silica aerogels were characterized using Brunauer–Emmett–Teller (BET) analysis, thermo-gravimetric analysis, FT-IR, and Raman spectroscopic techniques. Based on the obtained results, the differences in structure between samples before and after a surface silylation and the effect of drying control agents were documented. The structural measurements confirmed the efficient silylation process (TMCS/n-hexane), as well as the presence of DMF residues of hydrogen bonded with unreacted Si-OH silanol groups within the silica backbone after surface modification. Based on TG analysis, it was found that DMF addition improves thermal resistance (up to 320 °C) and hydrophobic character of prepared aerogel. Modification of the silica aerogel synthesis process by DMF also resulted in a significant increase in BET—the specific surface area, for the unmodified aerogel was ~828 m2/g, and for the DMF-modified aerogel more than 1200 m2/g—much higher than the value of silica aerogels available on the market.

CO2 Hydrogenation to Methanol on CuO-ZnO/SiO2 and CuO-ZnO/CeO2-SiO2 Catalysts Synthesized with β-Cyclodextrin Template

A series of mixed copper (II)—zinc oxide catalysts supported on unmodified and ceria-modified silica supports were synthesized using β-cyclodextrin as a template. The novelty of this work lies in the use of cyclosextrins for the template synthesis of catalyst supports. The obtained samples were analyzed by XRD, SEM-EDX, low-temperature nitrogen physisorption, XPS, and EPR. The magnetic properties of the catalysts were also measured. The thermal decomposition of precursors was analyzed by TGA combined with mass-spectrometric analysis of the evolved gases. The effects of the support pore size, the nature of the active phase and its loading, as well as the sequence of component deposition on the catalyst performance in the CO2 conversion to methanol were studied. The catalysts with cerium added at the gelation stage demonstrated the best performance. The selectivity of these samples reaches values of more than 90% over a fairly ide temperature range, with the productivity reaching 480 g/kg cat·h at 300 °C.

Toward maximizing the selectivity of diesel-like hydrocarbons from oleic acid hydrodeoxygenation using Ni/Co-Al2O3 embedded mesoporous silica nanocomposite catalysts: An experimental and DFT approach

The development of an effective hydrodeoxygenation (HDO) catalyst is crucial for controlling product selectivity and catalyst stability. In this study, we synthesized monometallic (Ni and Co), as well as a bimetallic, NiCo embedded mesoporous composite catalysts using a simple one-step method involving meso-macroporous silica, boehmite, nickel acetate, and cobalt acetate. The synthesized range of catalysts (5, 10, 15 wt% Ni, 10 wt% Co, 10 wt% NiCo) were thoroughly characterized by various techniques. The characterization results showed that the present method leads to the growth of nano-catalyst on porous silica surface (M−Al2O3/SiO2, M = Ni, Co, NiCo). These composites exhibited strong metal-support interaction, improved surface and texture properties and significant amount of weak to medium acid sites. The M−Al2O3/SiO2 composite catalysts demonstrated improved catalytic performance in the HDO of oleic acid. At temperature of 375 °C, the conversion trend of catalysts followed the order; 10NiCo-Al2O3/SiO2 (89%) > 10Ni-Al2O3/SiO2 (87%) > 10Co-Al2O3/SiO2 (85%) > 10Ni/SiO2 (81%). Moreover, the yield of C15-C18 hydrocarbons was substantially enhanced at moderate temperature compared to unmodified silica support. Time-on-stream experiments further confirmed the relative stability of the composite catalysts over a period of 20 h. Furthermore, density functional theory (DFT) ab initio calculations were performed where the adsorption of oleic acid on icosahedral monometallic M13 (M = Co or Ni) and bimetallic Ni2Co2 nanocluster deposited on γ-Al2O3 (110) support was investigated. The adsorption strength for the most stable conformations followed the order: Ni13/amorphous SiO2 >Ni2Co2/Al2O3 >Co13/Al2O3 >Ni13/Al2O3. Bader charge transfer analysis indicated higher charge transfer at the interfaces of γ-Al2O3Al2O3(110) supported catalysts compared to Ni13/amorphous SiO2 surface.

Impact of silica oxide and functionalized silica oxide nanoparticles on growth of Chlorella vulgaris and its physicochemical properties

In this study, silica oxide nanoparticles (SiO2 NPs) and methyl-functionalized SiO2 NPs were compared for their effects on the growth of Chlorella vulgaris, production of biomass, and lipid content. The synthesised nanoparticles were characterised by using techniques such as FTIR, XRD, UV-Vis, FESEM with EDX and TEM. The synthesised nanoparticles were used to enhance the gas-liquid interface areas, which increase the concentration of dissolved carbon dioxide in the growth medium in order to increase the accumulation of lipid content in C. vulgaris cultures. The most effective way to improve the gas-liquid interface area was to use SiO2 NPs at a concentration of 0.3 wt%. The hydrophobic functional group methyl was added to the hydrophilic surfaces of SiO2 NPs. Methyl-functionalized SiO2 NPs improved the gas-liquid interface area more effectively than unmodified silica nanoparticles. The concentration of dissolved CO2 was 316.66 mg L−1 with methyl-functionalized SiO2 NPs. During microalgae culture, methyl-functionalized SiO2 NPs at a concentration of 0.3 wt% considerably improved the production of dry biomass, lipid, protein, carbohydrate, and chlorophyll contents as compared to the control.

Effect of oil palm boiler ash modified with PEG 6000 on mechanical properties of high density polyethylene

The mechanical properties of material play an essential role in the material. Mechanical properties are one of the properties possessed by a material to function for various applications. Using nanostructured materials such as silica and layered silicates as fillers can significantly change the properties of the polymer matrix. OPBA preparation was carried out using calcination and ball mill methods, coprecipitation, and the addition of PEG 6000. Various methods were carried out to obtain OPBA with optimal silica content. HDPE thermoplastic was prepared with OPBA filler by mixing HDPE thermoplastic with OPBA nanoparticles modified with PEG 6000. SEM OPBA calcination and ball mill show the presence of pores on the surface. Meanwhile, the pore in OPBA does not lead to coprecipitation. However, in OPBA with added PEG 6000, it was seen again that there were pores on the surface and the presence of agglomerate dispersions in OPBA preparation with PEG 6000 showed the addition of functional groups to OPBA. The dispersion peaks of the silica contained in OPBA with state characteristics at 20o–30o appear in the XRD patterns of unmodified silica and modified silica, indicating that the precipitated silica is amorphous silica and the surface modification does not change the phase structure of the modified silica. In addition, the optimal silica content is found in OPBA PEG 6000, with a silica content of 60.7%. The addition of OPBA PEG 6000 filler generally increases the mechanical properties of tensile strength, elongation at break, and elongation modulus.

A paradigm increase in adsorption efficiency during separation of some styrylpyridinium dyes from organic media using graphene oxide modified silica (GOMS) scaffold

Graphene oxide modified silica (GOMS) has been prepared to study the adsorption of some cationic styrylpyridinium dyes in organic solvent media of variable polarities. GOMS is privileged with very unique surface structure having graphitic network and oxygen functionalities. The unmodified silica, GOMS and dye adsorbed GOMS samples have been characterized by Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) methods. Effects of various optimized conditions like temperature, contact time, adsorbate concentration and adsorbent dosages have been analysed and the kinetic and thermodynamic studies have been correlated with relevant experimental data to reach at a conclusion. The adsorption follows Freundlich isotherm model. The impacts of substituents present on the adsorbate molecules and polarities of the solvents have been discussed to understand the adsorption phenomenon. A suitable modelling has been done to demonstrate the adsorption mechanism from the experimental findings.

Surface Modification of Silica Particles with Adhesive Functional Groups or Their Coating with Chitosan to Improve the Retention of Toothpastes in the Mouth.

Silica is widely used in the oral care formulations to act as an abrasive and to give the products its distinct physical properties. In this study, silica particles were synthesized using a co-condensation of tetraethyl orthosilicate with a series of functional silane compounds [(3-mercaptopropyl)trimethoxysilane, (3-glycidyloxypropyl)trimethoxysilane, and (3-acryloxypropyl)trimethoxysilane)]. The surface of the particles based on tetraethyl orthosilicate and (3-glycidyloxypropyl)trimethoxysilane was then further modified with 3-aminophenylboronic acid. Commercial Aerosil R972 Pharma silica particles were also coated with chitosan. Additionally, commercially available (3-maleimido)propyl-functionalized silica particles were used in this study. All these functionalized silica particles were incorporated into toothpaste formulations, and their retentive properties were tested on ex vivo sheep tongue mucosa models using fluorescent microscopy-based flow-through techniques. Those surfaces with chitosan, phenylboronic acid, and acryloyl groups were shown to provide a significant improvement in the retention of the oral care formulations during the retention testing. The retention of toothpastes containing silica functionalized with maleimide and thiol groups was also superior compared to that of unmodified silica particles. This study synthesized and tested a range of silica particles and demonstrated that the functionalized silica incorporated into toothpastes can significantly improve the retention of these formulations on oral mucosal surfaces.

Adsorption removal of styrene on C–Cl grafted silica gel adsorbents

The heat desorption of styrene from adsorbents is impracticable owing to its spontaneous polymerization under heating conditions. However, the feature also brings a potential promoting effect on styrene adsorption. Therefore, it is expected to develop the non-regenerative adsorbents with large adsorption capacity by strengthening the polymerization effect. In this work, C–Cl grafted silica gel adsorbents were prepared by introducing (Chloromethyl)dimethylchlorosilane (CMDMCS) and FeCl2 into silica gel. The C–Cl grafted silica gel exhibited excellent styrene adsorption performance, its adsorption amounts for styrene were 4.67 times and 9 times of unmodified silica gel under dry air condition and high humidity condition (RH = 80%), respectively. In addition, the adsorption of styrene on C–Cl grafted silica gel was almost unaffected by the presence of toluene. The characterization of adsorbents after styrene adsorption indicated that the improvement of adsorption capacity of C–Cl grafted silica gel for styrene can be attributed to atom transfer radical polymerization (ATRP) of styrene molecules on modified silica gel during adsorption process.

In Situ Ring-Opening Polymerization of L-lactide on the Surface of Pristine and Aminated Silica: Synthesis and Metal Ions Extraction.

The development of functional materials from food waste sources and minerals is currently of high importance. In the present work, polylactic acid (PLA)/silica composites were prepared by in situ ring-opening polymerizations of L-lactide onto the surface of pristine (Silochrom) and amine-functionalized (Silochrom-NH2) silica. The characteristics of the ring-opening polymerization onto the surface of modified and unmodified silica were identified and discussed. Fourier transform infrared spectroscopy was used to confirm the polymerization of lactide onto the silica surface, and thermogravimetric analysis determined that PLA constituted 5.9% and 7.5% of the composite mass for Silochrom/PLA and Silochrom-NH2/PLA, respectively. The sorption properties of the composites with respect to Pb(II), Co(II), and Cu(II) ions were investigated, and the effect of contact time, initial metal ion concentration, and initial pH were evaluated. Silochrom-NH2/PLA composites were found to have a higher adsorption capacity than Silochrom/PLA for all chosen ions, with the highest adsorption value occurring for Pb2+ at 1.5 mmol/g (90% removal efficiency). The composites showed the highest performance in the neutral or near-neutral pH (created by distilled water or buffer pH 6.86) during the first 15 min of phase contact. The equilibrium characteristics of adsorption were found to follow the Langmuir isotherm model rather than the Freundlich and Temkin models. Perspective applications for these PLA/silicas include remediation of industrial wastewater or leaching solutions from spent lead-acid and Li-ion batteries.