Papers by Keyword: Mesoporous Silica

Abstract: A rattle-type diamine-functionalized mesoporous silica sphere (DA-RMSS) was fabricated stepwise using a self-templating method through cationic surfactant assisted selective etching strategy. The rattle-type morphology of the obtained DA-RMSS material was disclosed by transmission electron microscopy, while its chemical composition was characterized by CHN elemental analysis, Fourier transform infrared spectroscopy, and solid-state ²⁹Si cross-polarization/magic-angle-spinning nuclear magnetic resonance spectroscopic measurement, which corroborates the successful formation of siloxane network and the incorporation of organic component. Moreover, nitrogen adsorption–desorption isotherm measurement was conducted to reveal that DA-RMSS possesses large Brunauer–Emmett–Teller (BET) specific surface area of 814 m²g^–1, pore volume of 0.78 cm³g^–1, and narrow pore size distribution centered at 3.0 nm. Furthermore, its uptake property on carbon dioxide was also investigated in this contribution.

Abstract: Mesoporous silica thin films were fabricated on gold substrates with a sol-gel method including a cationic surfactant. The interface of gold and silica thin films was fixed with a mercaptosilane. The surface roughness of the thin films and their grain sizes of silica were both increased with the elimination of the cationic surfactant and polyethylene glycol (PEG) modification on its surface. The surface reaction, adsorption of bovine serum albumin (BSA), was monitored with surface plasmon resonance (SPR). Although the adsorption amount of BSA at 1 mg/mL were 7.9 ng/cm² on the mesoporous silica, the PEG modification can completely desorb BSA. The mesoporous silica thin films on gold substrates fabricated will be a good platform for analyzing surface reaction.

Abstract: Mesoporous silica (MPS) coatings on hydroxyapatite (HAp) granules and their protein adsorptive capabilities were studied. MPS particles were coated on HAp granules using a dip-coating method, but the HAp granules were not totally covered by the MPS particles. A silica interlayer was formed on the HAp granules via magnetron sputtering or the sol-gel method prior to the coating of the MPS. The HAp granules coated with the silica interlayer were fully covered by the MPS particles. An silica interlayer may offer bonding between the HAp granules and MPS coating. The adsorption of protein on the MPS-coated HAp granules was evaluated by UV-VIS spectroscopy. The adsorption capacity of protein on the HAp granules was improved by the MPS coatings on the HAp granules, and that of the HAp granules coated with the silica interlayer showed a higher protein adsorption capacity.

Abstract: The preparation of mesoporous silica compact through spark plasma sintering (SPS) and adsorption / desorption of protein onto SPS mesoporous silica (MPS) compact is reported. MPS powders, prepared using triblock copolymer, PEO₂₀PPO₇₀PEO₂₀, were compacted in carbon die and heated at 400 or 500 °C for 5 min under uniaxial pressure. The products are referred to as MPS-400 and MPS-500, respectively. The MPS sinters keep the mesoporous configuration, but the mode diameter of MPS-400 was smaller than that of MPS powders and MPS-500. The adsorbed amounts of protein on MPS-400 was higher than that on MPS-500, while the pore diameter, BET surface area, pore volume of MPS-400 are less than those of MPS-500. The interstices in MPS-500 are narrower than that in MPS-400, which may restrict the protein to penetrate through the narrow channels to reach the mesopores of MPS. The quantity of adsorbed amount of protein on MPS sinters does not depend on mesopore configuration but on the macropore configuration of the MPS sinters.

Abstract: The aim of this study was to examine the effects of active filler in resin-based pit and fissure sealant on fluoride release and recharge abilities. Mesoporous silica was synthesized from tetraethyl orthosilicate (TEOS) using sol-gel method. Resin-based sealant was incorporated with 5% w/w of filler (<45 μm): synthesized mesoporous silica (S), calcium carbonate (C), and fluoro-alumino silicate glass (F). Resin-based sealant without filler added was the control. Ten specimens of each group were separately stored in 3 mL of deionized water and the fluoride concentration, before and after fluoride recharge, were measured every 3 days (from day 3 to day 27). Fluoride release before recharge was only found in F (0.1024±0.0077 ppm) and then gradually decreased to baseline. After two recharges, the highest fluoride release was found in S (0.0804±0.0095 ppm after first recharge and 0.0601±0.0092 after second recharge), followed by F (0.0386±0.0024 ppm after first recharge and 0.0313±0.0027 ppm after second recharge), and then decreased to baseline. Fluoride recharge was not found in C and control. This result suggested that resin-based pit and fissure sealant containing synthesized mesoporous silica filler has fluoride recharge ability which might prevent secondary caries at material-enamel interface.

Abstract: We report a simple process of stabilizing metastable β-Zn₂SiO₄:Mn nanocrystals in amorphous silica. Zn and Mn ions were incorporated in mesoporous silica by immersing aqueous solution of Mn²⁺ and Zn²⁺, and the mesoporous silica was sintered at 1000-1100oC in reducing atmosphere. β-Zn₂SiO₄:Mn were formed along with α-Zn₂SiO₄:Mn in sintered mesoporous silica when diameter of pore is as small as 2.4nm. Due to the formation of β-Zn₂SiO₄:Mn, photoluminescence (PL) spectra exhibited both green and yellow emission originated from α-and β-Zn₂SiO₄:Mn, respectively. Relative intensity of the two emission was changed by changing heat treatment time and temperature. These results imply that this simple process is promising to stabilize nanocrystal of β-Zn₂SiO₄:Mn emitting yellow luminescence.

Abstract: Deoxyribonucleic acid (DNA) adsorption onto particles has applications in biosensors, separation methods, and gene delivery. Mesoporous silica (MPS), which exhibits a high surface area and large pore volume, is used in these applications because its pore size is easily controlled and its surface functional groups are easily exchanged. In this study, three types of MPSs with different pore sizes (2.4, 5.6, and 11.8 nm) were functionalized with different aminosilane coupling reagents and the effects of the MPS pore size and surface functional groups on DNA adsorption were evaluated. As the pore size of MPS increased, MPSs with diethylenetriamine (–3NH₂) adsorbed higher amounts of DNA, whereas MPSs with hexylenediamine groups (–2HNH₂) adsorbed lower amounts of DNA. Moreover, the fitting of DNA adsorption equilibrium data to Langmuir and Freundlich isotherm models was investigated.

Abstract: The preparation of mesoporous silica coated rf-sputterd apatite / titanium substrate and protein adsorptive property is reported. Hydroxyapatite coated titanium implant has been used, and the adsorption of proteins onto implant is very important for bond formation between bone and implant. Mesoporous silica (MPS) materials have been extensively studied as carriers of bio-molecules due to their potential practical applications in medical materials. Pore diameters of 1.5 – 30 nm of the periodic mesoporous materials are close to the diameters of target molecules and high adsorbed amount of proteins onto MPS has been reported, and also enclosure of the protein in a well-defined space may help to prevent denaturation. Previously, we reported the MPS coating on the porous hydroxyapatite (HAp) ceramics obtained by dip-coating method, and by the vapor phase synthesis. Protein adsorption on the porous HAp with the MPS coatings was evaluated using UV-VIS spectrometry, and the quantity of adsorbed amount of protein was remarkably improved. In this study, the HAp deposition on Ti substrate (HAp/Ti) was carried out by rf magnetron sputtering and hydrothermal treatment, and MPS coating on HAp/Ti using LB deposition apparatus to improve the protein adsorptive property of HAp/Ti. The quantity of adsorbed protein onto the HAp /Ti was around 12 times high, and that onto the MPS/HAp/Ti was 18 times high compared to that on Ti substrate.

Abstract: The series of ZnO-SBA-15 catalysts with 0.9wt% to 8.5wt% ZnO content have been synthesized by solvothermal impregnated of Zn acetate in ethanol on mesoporous silica SBA-15 platelets in order to maximize the methyl ester selectivity in transesterification reaction. The properties of these catalyst were characterized by N₂ adsorption-desorption isotherm, NH₃ temperature-programmed desorption, SEM, and XRD. The results showed that the ordered mesoporous structure of SBA-15 was remained with specific surface areas above 500 m²/g and a narrow pore size distribution observed with the mean pore size around 60 Å after ZnO modification. The strength of the acid sites and total acid amount of ZnO-SBA-15 catalysts is varied with number of ZnO loadings. The synthesized ZnO-SBA-15 catalyst was tested for catalytic activity in transesterification of crude Jatropha oil. It was found that at 200 °C for 2 h reaction of the ZnO-SBA-15 catalysts with acid capacities of 0.36-1.29 mmol H⁺/g-catal gave 68-98wt% of FAME yields and 0.4-1.4wt% of FFA yields which are comparable to the pure ZnO.

Abstract: Magnetically-separable enzyme system has been developed by adsorption, precipitation and cross-linking of enzymes in superparamagnetic hierarchically ordered mesoporous mesocellular silica (M-HMMS). The immobilization of xylanase within M-HMMS were compared between enzyme adsorption (EA), enzyme adsorption and cross-linking (EAC), and enzyme adsorption, precipitation and cross-linking (EAPC). EAPC includes higher enzyme activity immobilized within the matrix in comparison with the other methods. Furthermore, the immobilized enzyme is predicted to be prevented from leaching out of the matrix when exterior blow is being tested on the structure. Thus, the stability of the EAPC of this invention is anticipated to be maintained even after a long time passed since high enzyme activity compared with known method can be supported and immobilized within the matrix. Consequently, it is possible to improve performance of the enzymes by manipulating the preparation and operation condition.