Search

A solgel process was developed, through which silica films possessing both high antireflection and super water repellence were obtained. In this process, methyl-modified Si[O.sub.2] sols synthesized by colloidal suspension of Si[O.sub.2] particles and hexamethyldisilazane (HMDS) were used to deposit spinning-coating films on optical glass substrates. On the resultant films the contact angle for water increased with the increasing amount of HMDS in the reaction mixture. The biggest contact angle was 165[degrees] and the lowest reflectivity on one-sided film reached 0.03%. The antireflections were high all the while. One advantage of this process is that neither a roughened surface nor fluoroalkyltrialkoxylsilane (FAS) is needed to obtained super water repellence. OCIS codes: 160.6060, 160.6030, 310.1210, 310.1620.

Abstract: High dispersion Co3O4 nano-particles supported on hollow mesoporous silica spheres (HMSS) with bimodal pore distribution were prepared by “two-solvent” technique. As-synthesized catalysts were characterized by XRD, N2 adsorption–desorption, XPS, SEM, TEM, and H2-TPR. The results showed that Co3O4 nano-particles were present inside the pore system of HMSS and the particles sizes increased with the increasing loaded cobalt content. The catalysts show good performance and high selectivity of C5–C18 hydrocarbon in F–T synthesis, which should attribute to the unique bimodal pore distribution facilitating reactants to access the active sites and to transport higher hydrocarbon products. [Copyright &y& Elsevier]

Abstract: The effect of polyvinylpyrrolidone (PVP) on the structure and laser-induced damage threshold (LIDT) of sol–gel silica anti-reflective films is investigated. The results of dynamic light scattering, transmission electron microscopy, and small angle X-ray scattering, show that the PVP molecules surrounded the silica sol particles through the strong hydrogen bonds between Si-OH groups and the PVP. As a result, the growth of silica particles was restricted and thus the interface layer between the silica particles and the solvent become thickened with PVP content. Furthermore, the PVP reduced the porosity of the film, so the anti-reflection properties of the film were weakened. A multi-fractal analysis showed that the appropriate addition of PVP, 1 weight percent (wt%), could improve the surface fractal structure of the film, but that higher PVP content resulted in reduced surface uniformity. The addition of PVP lead to improved LIDT. [Copyright &y& Elsevier]

Abstract: Following a three-stepped reaction, a novel nonsurfactant method was established to synthesize mesoporous silica using dye Basic Fuchsin (BF) as template, and using m-xylenediisocyanate (m-XDI) and aminopropyltriethoxysilane (APTES) as bridging molecules. The first step is to form the intermediate product (namely XA) of m-XDI and APTES. The second step is to form the intermediate product (namely XAD) of XA and dye BF. The third step is the hydrolysis and condensation of siloxane to construct mesopores. Due to the plane structure of dye BF, it was linked with hydrolyzed siloxane precursors to form mesopores. As expected, mesoporous structure could be formed only when the XA to dye molar ratio was set to 3:1. The synthesized mesoporous silica had narrow pore size distribution centered at 3.56nm and high surface area of 716m2 g−1. [Copyright &y& Elsevier]

Abstract: Methyl-modified silica sols were prepared with the polymer of methyltriethoxysilane (MTES), the polymer of dimethyldiethoxysiloxane (DDS), and hexamethydisizane (HMDS) as mono-, di-, and tri-methyl modifiers respectively. By comparing the size and the shape of clusters in three different methyl-modified silica sols, the special nature of the sol was found to be the key to the property of films. Different modal modification of methyl to silica particles led to different cluster fractal structures that influenced the morphology, the porosity of films and consequently the anti-reflection characteristics. The contribution of methyls in or on clusters directly determined the hydrophobicity. Using mono- or di-methyl-modified silica sol, the film/water contact angles were less than 120°. But it could reach 165° when using tri-methyl-modified silica sol. The lowest reflectivity of film could reach 0.0% for all the three modified sols. As a result of the comparative study, tri-methyl-modified silica sol was more suitable to prepare hydrophobic anti-reflective film with required high optical performance. [Copyright &y& Elsevier]

A series of silica–polyvinyl alcohol (PVA) hybrids were prepared by acid-catalyzed hydrolysis of tetraethoxysilane (TEOS) in the mixture of ethanol and water containing dissolved polyvinyl alcohol via a sol–gel process. A small-angle X-ray scattering (SAXS) study on those hybrid gels has been performed utilizing synchrotron radiation. Intensive positive deviation from Porod’s law indicated that there existed density fluctuation within the matrix of silica–PVA hybrid gel. Using the differential d[q3I(q)]/d(q2) as a variant slo, plotting ln(slo) versus ln(q) can produce the dimension n and the amplitude Fl of density fluctuation. Density fluctuation resulted from both the micropores in gel and Si–O–PVA–O–Si bridge between SiO2 particle and PVA chain. When PVA increased in gel, the decreased micropores reduced the fluctuation but PVA enhanced the fluctuation. With the conjunction of correlation function C(r), it was clear that the bridge of Si–O–PVA–O–Si enlarged the compositional heterogeneity within gel matrix and made n increase with the increase of PVA. In addition, the fluctuation dimension n is a fraction rather than an integer that was formerly predicted by Ruland, which may relate to the fractal structure of hybrid gel. [Copyright &y& Elsevier]

A simple processing of preparing broadband anti-reflective single-layer silica films is presented in this article. By adding polyvinylpyrrolidone (PVP) into reactant mixture, PVP-containing SiO2 sol was obtained under base catalyzed hydrolysis and condensation of tetraethoxysilane. The spin-coating films and the dip-coating films were deposited on one side and two sides of quartz substrates. The anti-reflection band is 315 nm wide for dip-coating film and 559 nm wide for spin-coating film and the transmittance reached to 99.95 and 95.92% for dip-coating film and spin-coating film, respectively. By a Nd:YAG lasers the laser damage threshold of as-deposited films was measured at 1064 nm wavelength (1 ns pulse). It ranged from 24 to 33 J/cm2 with an average of 28.7 J/cm2. Compared to SiO2 sol without PVP, not only was the anti-reflection band broadened but the anti-reflection and laser damage threshold were retained. [Copyright &y& Elsevier]

Abstract: To investigate the driving force for bilirubin adsorption on mesoporous materials, a comparative study was carried out between pure siliceous SBA-15 and three functionalized SBA-15 mesoporous materials: CH3-SBA-15 (MS), NH2-SBA-15 (AS), and CH3/NH2-SBA-15 (AMS) that were synthesized by one-pot method. The obtained materials exhibited large surface areas (553–810m2/g) and pore size (6.6–7.1nm) demonstrated by XRD and N2-ad/desorption analysis. The SEM images showed that the materials had similar fiberlike morphology. The functionalization extent was calculated according to 29Si MAS NMR spectra and it was close to the designed value (10%). The synthesized mesoporous materials were used as bilirubin adsorbents and showed higher bilirubin adsorption capacities than the commercial active carbon. The adsorption capacities of amine functionalized samples AMS and AS were larger than those of pure siliceous SBA-15 and MS, indicating that electrostatic interaction was the dominant driving force for bilirubin adsorption on mesoporous materials. Increasing the ionic strength of bilirubin solution by adding NaCl would decrease the bilirubin adsorption capacity of mesoporous material, which further demonstrated that the electrostatic interaction was the dominant driving force for bilirubin adsorption. In addition, the hydrophobic interaction provided by methyl groups could promote the bilirubin adsorption. [Copyright &y& Elsevier]

Abstract: Mesoporous silica spheres with controllable particle size were synthesized in mixed ethanol–water solvent. These materials possessed same pore size distribution and pore channel geometry. The amount of ibuprofen (IBU) adsorbed in mesoporous channels increased with the surface area of mesoporous silica spheres. Three kinds of release fluids, simulated intestinal fluid (SIF, pH=7.4), simulated body fluid (SBF, pH=7.4), and simulated gastric fluid (SGF, HCl aqueous solution, pH=1.2) were used to investigate drug release. The effects of particle size and dispersancy of mesoporous spheres on drug release rate were discussed in detail. It was found that larger or agglomerate mesoporous silica spheres could delay the drug release process, which could be attributed to pore-mouth amount and mesopore channel length of mesoporous spheres. Furthermore, to obtain a well controlled drug release system, hydrophobic trimethylsilyl (TMS) groups were functionalized on the surface of mesoporous silica spheres. The release of IBU from TMS-functionalized mesoporous spheres was obviously delayed with the increase of TMS content. [Copyright &y& Elsevier]

Abstract: A simple pH-controlled drug release system was successfully prepared by coating pH-sensitive polymer hydroxypropyl methylcellulose phthalate (HPMCP) on drug-loaded mesoporous SBA-15 tablet. Using famotidine (Famo) as a model drug, the effects of coating times and drying temperature on drug release were studied in detail to optimize the drug release system. In simulated gastric fluid (SGF, pH 1.2), it took only 2h for Famo to be completely released from mesoporous silica tablet without HPMCP coating. Also in SGF, with the increase of coating times and drying temperature, the release of Famo was greatly delayed by HPMCP coating. For the tablet with twice coating of HPMCP and dried at 80°C, only 4.0wt.% of Famo could be released within 4h. However, in simulated intestinal fluid (SIF, pH 7.4), HPMCP coating did not show obvious effect on the release of Famo. [Copyright &y& Elsevier]

Abstract: Silica-modified titanium dioxides were prepared by a hydrothermal method and then characterized by XRD, FT-IR, XPS, TEM, and UV–visible spectroscopy. The silica-modified titanium dioxides were in anatase phase and had large surface areas. There was strong interaction between SiO2 and TiO2, and Tih name="sbnd" />Si bonds formed during the hydrothermal process. The addition of silica in TiO2 particles could effectively suppress the formation of the rutile phase and the growth of titanium dioxide crystals. DRS spectra proved an increase in the band-gap transition with the increase of silica. The silica-modified TiO2 nanoparticles exhibited better photocatalytic activity, which increased with the silica amount, in comparison with pure TiO2 nanoparticles. Due to better thermal stability, the photocatalytic activity of the silica-modified TiO2 sample held good photocatalytic activity even after calcined at 1273 K. [Copyright &y& Elsevier]

Abstract: Titania–silica composite nanoparticles were prepared by sol–gel-hydrothermal and sol–gel routes, respectively, and their physico-chemical and photocatalytic properties were compared. The results of XRD, TEM and BET surface areas showed that sol–gel-hydrothermal route led to anatase titania–silica composite nanoparticles with large specific surface area, but the sol–gel route tended to form mixture of anatase and rutile. The composite nanoparticles prepared by sol–gel-hydrothermal route had better thermal stability against phase transformation from anatase to rutile, agglomeration and particle growth than those prepared by sol–gel route. On the basis of XRD, FT-IR, XPS and 29Si MAS-NMR, a strong interaction was found between SiO2 and TiO2, and Ti–O–Si bonds formed during both the two routes. But more Ti–O–Si bonds formed in the composite nanoparticles prepared by sol–gel-hydrothermal route than those prepared by sol–gel route. As a result, the titania–silica composite nanoparticles prepared by sol–gel-hydrothermal route exhibited higher photocatalytic activity in decomposition of methylene blue than that prepared by sol–gel route, and it had excellent photocatalytic activity even after calcined at 1000°C. [Copyright &y& Elsevier]

Abstract: Dimethylsilyl (DMS) modified mesoporous silicas were successfully prepared via co-condensation and post-grafting modification methods. The post-grafting modification was carried out by the reaction of the as-synthesized MCM-41 material (before CTAB removal) with diethoxydimethylsinale (DEDMS). N2 adsorption–desorption and 29Si MAS NMR characterization demonstrated that different amount of DMS groups were successfully incorporated into the co-condensation modified samples, and the functional DMS groups were placed selectively on the pore openings and external pore surfaces in the post-grafting modified samples. Subsequently, the controlled drug delivery properties from the resulting DMS-modified mesoporous silicas were investigated in detail. The drug adsorption experiments showed that the adsorption capacities were mainly depended on the content of silanol group (CSG) in the corresponding carriers. The in vitro tests exhibited that the incorporation of DMS groups greatly retarded the ibuprofen release rate. Moreover, the ibuprofen release profiles could be well modulated by varying DMS modification levels and site-selective distribution of functional groups in mesoporous carriers. [Copyright &y& Elsevier]