In Situ Monitoring of the Generation of Monodisperse Silica Particles during the Hydrolysis of Tetraethyl Orthosilicate with Piezoelectric Quartz Crystal Impedance Analyzer

The piezoelectric quartz crystal (PQC) impedance analyzer was used to monitor in situ the generation of monodisperse silica particles during the hydrolysis of tetraethyl orthosilicate (TEOS) and their adsorption onto an Au electrode in alcohol solutions containing water (6-15 mol/L) and ammonia (0 2-2 0 mol/L). The equivalent circuit parameters, the resonance frequencies and the half peak width values of the conductance spectra of the PQC resonance were obtained. The resonant frequency decreased notably while the motional resistance changed very slightly (within 1 Ω) during the hydrolysis reaction, suggesting that the mass effect do^minated the adsorption of generated monodisperse silica particles on the gold electrode in this system. Changes in f 0 indicated that the ammonia concentration affected the hydrolytic reaction obviously, and the influence of water concentration on the reaction was small while the water was significantly excessive. Kinetics of monodisperse silica particle adsorption occurring at the electrode|solution interface was analyzed using a first order reaction scheme. In addition, the electrolyte induced precipitation of the monodisperse silica particles was monitored and discussed. The mean size, the number of adsorbed particles per area and the converge of monodisperse silica particles were obtained from scanning electron microscope (SEM) observations.

A novel fabrication of meso-porous silica film by sol-gol of TEOS

A homogeneous crack-free nano- or meso-porous silica films on silicon was fabricated by colloidal silica sol derived by hydrolyzing tetraethyl orthosilicate (TEOS) catalyzing with (C4H9)4N+OH- in water medium. The solution with ratio of H2O/TEOS15, R4N+ and glycerol as templates, combining with the hydrolyzed intermediate, controlled the silica aggregating; the templated silica film with heterostructure was developed into homogeneous nano-porous then meso-porous silica films after being annealed from 750 C to 850 C; the formation mechanism of the porous silica films was discussed; morphologies of the silica films were characterized. The refractive indexes of the porous silica films were 1.2561.458, the thermal conductivity < 0.7 W/m/K. The fabricating procedure and the sequence had not been reported before.

Protein Mediated Silica Particles with pH Controlled Porosity and Morphology

Background: The silica leaching activity of some of the mystifying non-pathogenic BKH1 bacteria present in the cluster of hot springs (temperatures range 35°C - 80°C) at Bakreshwar (West Bengal, India, 23°52'48"N;87°22'40"N) has provided some significant advancements in the field of nanotechnology. The present investigation was designed to synthesis the silica particles using bioremediase protein at different pH conditions. Methods: A secretary bacterial protein bioremediase (UniProt Knowledgebase Accession Number P86277) isolated from a thermophilic non-pathogenic bacterium BKH1 (GenBank Accession No. FJ177512) has been used to synthesis the silica particles at different pH conditions (pH at 3.0, 5.0, 8.0, 10.0, and 12.0 respectively). The silica particles were synthesized by the action of bioremediase protein on Tetra-ethyl-orthosilicate (TEOS) under ambient condition. Morphological and compositional studies of the biosynthesized silica particles were characterized by Field emission scanning electron microscope (FE-SEM) equipped with Energy dispersive X-ray analyser (EDX). Results: The Fourier transformed infra-red (FTIR) spectroscopic analysis confirmed the nature as well as occurrence of several functional groups surrounded on the silica particles. The amorphous nature of the prepared silica particles was confirmed by X-ray diffractometer (XRD) study. The Zeta potential (ζ) study revealed the stability of silica particles in neutral pH environment. The Brunauer-Emmett-Teller (BET) surface area measurement confirmed the porosity variation in all biosynthesized silica particles prepared at different pH conditions. Raman spectra analytically depend on their respective specific surface (BET) area. Thermogravimetry tool was used to monitor the effects of the thermal treatment on the surface properties of all the samples. Conclusions: The method for the synthesis of silica particles at different pH condition using the protein bioremediase has a special implication as it is an environmentally benign, cost-effective and facile technique which may have conceivable application in chromatographic packing. In addition, controlling of size as well as porosity of the silica particles can be achievable by pH as an only variable.

Preparation of hydrophobic transparent paper via using polydimethylsiloxane as transparent agent

Transparent paper with good hydrophobicity and flexibility was expected to act as an alternative substrate in fabrication of flexible electronics.However,conventional paper made of cellulose fibers was opaque and hydrophilic without undergoing special processing.Herein,cellulose fiber paper was treated by impregnating with hydrolyzed tetraethyl orthosilicate(TEOS)followed by coating with hydrophobic polydimethylsiloxane(PDMS)to prepare hydrophobic transparent pa-per.The results showed that silica nanoparticles produced by the TEOS hydrolysis improved the paper transparency to some extent,increased the paper thermal stability,but still remained the hydrophilicity of paper.After the paper was further coated with the PDMS and the PDMS was consolidated,the paper became clearly transparent and hydrophobic.The processed paper had a transmittance of more than 90%at 550 nm.The water contact angle of the paper reached about 110°.This work provided a new approach for the fabrication of hydrophobic transparent paper with conventional cellulose fiber paper.

Effect of the addition of TEOS on the SiC fibers fabricated by electrospinning

Polycarbosilane(PCS)has been widely used to fabricate silicon carbide(SiC)fibers via pyrolysis.In this paper,for improving the morphology of SiC fibers,tetraethyl orthosilicate(TEOS,m=1 g,3 g and 5 g,respectively)was added into the PCS precursor solution(containing 1.5 g PCS).The continuous fibers have been prepared by electrospinning,and then the SiC fibers were synthesized by calcination at 1300℃,1400℃and 1600℃for 4 h respectively with a heating rate of 10℃/min in flowing nitrogen(N_(2)).The morphologies of the fibers were investigated by the scanning electron microscope(SEM)and it could be seen that the crystallinity of the SiC fibers was lower,the length of the SiC fibers was increased,and the diameter was uniform with the increase of the addition amount of TEOS.