Sol-gel transition in simple silicates II

Brinker, C. Jeffrey; Keefer, Keith D.; Schaefer, Dale W.; Assink, Roger A.; Kay, Bruce D.; Ashley, Carol S.

doi:10.1016/0022-3093(84)90385-5

Cited by 496 publications

(174 citation statements)

References 9 publications

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“…Under acid conditions, three-dimensional solid phase networks consisting of extended linear M-O-M chain polymers are developed [153]. Inorganic polymerization is believed to occur in three stages during acid-catalyzed condensation [154]:…”

Section: Sol-gel Processmentioning

confidence: 99%

Nanocrystalline materials and coatings

Tjong

Chen

2004

Materials Science and Engineering: R: Reports

835

345

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In recent years, near-nano (submicron) and nanostructured materials have attracted increasingly more attention from the materials community. Nanocrystalline materials are characterized by a microstructural length or grain size of up to about 100 nm. Materials having grain size of $0.1 to 0.3 mm are classified as submicron materials. Nanocrystalline materials exhibit various shapes or forms, and possess unique chemical, physical or mechanical properties. When the grain size is below a critical value ($10-20 nm), more than 50 vol.% of atoms is associated with grain boundaries or interfacial boundaries. In this respect, dislocation pile-ups cannot form, and the Hall-Petch relationship for conventional coarse-grained materials is no longer valid. Therefore, grain boundaries play a major role in the deformation of nanocrystalline materials. Nanocrystalline materials exhibit creep and super plasticity at lower temperatures than conventional micro-grained counterparts. Similarly, plastic deformation of nanocrystalline coatings is considered to be associated with grain boundary sliding assisted by grain boundary diffusion or rotation. In this review paper, current developments in fabrication, microstructure, physical and mechanical properties of nanocrystalline materials and coatings will be addressed. Particular attention is paid to the properties of transition metal nitride nanocrystalline films formed by ion beam assisted deposition process. #

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Section: Sol-gel Processmentioning

confidence: 99%

Nanocrystalline materials and coatings

Tjong

Chen

2004

Materials Science and Engineering: R: Reports

835

345

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“…The typical process parameters which affect structure and properties of silica gels are the H 2 O:Si ratio, pH, solvent and catalyst [30].…”

Section: Process Parameters Affecting Gel Structurementioning

confidence: 99%

Immobilization of Proteins in Silica Gel: Biochemical and Biophysical Properties

Ronda

Bruno

Campanini

et al. 2015

COC

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Abstract:The development of silica-based sol-gel techniques compatible with the retention of protein structure and function started more than 20 years ago, mainly for the design of biotechnological devices or biomedical applications. Silica gels are optically transparent, exhibit good mechanical stability, are manufactured with different geometries, and are easily separated from the reaction media. Biomolecules encapsulated in silica gel normally retain their structural and functional properties, are stabilized with respect to chemical and physical insults, and can sometimes exhibit enhanced activity in comparison to the soluble form. This review briefly describes the chemistry of protein encapsulation within the pores of a silica gel three-dimensional network, the mechanism of interaction between the protein and the gel matrix, and its effects on protein structure, function, stability and dynamics. The main applications in the field of biosensor design are described. Special emphasis is devoted to silica gel encapsulation as a tool to selectively stabilize subsets of protein conformations for biochemical and biophysical studies, an application where silica-based encapsulation demonstrated superior performance with respect to other immobilization techniques.

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“…It was known that, with acidic catalyst, the hydrolysis rate of TEOS was relatively fast but the condensation rate was relatively slow, and the ultimately generated product was not in a particle shape but generally in amorphous gel because a dense condensation could not occur. 12,16 Therefore, when an acid catalyst was employed, the fast alkoxy exchange and retarded hydrolysis-and-condensation could make it possible to monitor silicon species at the early stage of the reaction in the mixed alcohol solvent systems. Even though acidic catalyst condition is not the real reaction condition for preparing SNPs, we expect that it is possible to monitor the relative amounts of alkoxy exchanged products with time and to explain the size control of SNPs in different mixed alcohol solvent systems.…”

Section: Notesmentioning

confidence: 99%

Precise Size-control of Silica Nanoparticles via Alkoxy Exchange Equilibrium of Tetraethyl Orthosilicate (TEOS) in the Mixed Alcohol Solution

Lim¹,

Ha²,

Lee³

2012

Bulletin of the Korean Chemical Society

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Silica nanoparticles (SNPs) are one of the most interesting materials with regard to their easy preparation, nontoxicity, and simple surface modification. Based on their various advantages, SNPs have been widely studied and used in various fields such as solid support materials in the column chromatography, 1 insulating layer and silica-polymer composite 2 in engineering fields, and bio-imaging and drug/gene delivery systems in nano-biotechnology.3-5 To make SNP work effectively in all these applications, it is necessary to synthesize size-controllable and mono-dispersed silica particles. Since Stöber showed that spherical silica particles having narrow size distribution could be prepared from tetraethyl orthosilicate (TEOS) as silica source in alcohol solvent with water and aqueous ammonia as catalyst, 6 his method has been used and modified to prepare monodispersed and regular sized SNPs.7 The size control of SNPs was possible by varying the concentration of reactants, the chain length of alkyl group in alcohol solvents and silica sources, base catalysts to primary amine instead of ammonia solution.8 It was also reported that the usage of amino acids and the control of the mixing ratio of their optical isomers could change the size of SNPs. 9Although it is known that the basic formation mechanism of SNPs is the hydrolysis-and-condensation of TEOS, interestingly, the role of solvent during the formation of SNPs has not been systematically investigated yet. When alcohols with long alkyl chains were used as solvent, the size of SNPs was increased due to the different hydrolysis-andcondensation rate to generate seeds. As an example, it was reported that the different sized SNPs were synthesized in methanol (4 nm) and ethanol (8 nm) because the supersaturation ratio of the hydrolyzed silica sources in methanol was higher than that in ethanol.10 In other words, many smaller seeds were generated in fast reaction environment in methanol and could grow to produce many smaller SNPs compared to those produced in ethanol. The reason of different reaction rates in different solvents was mainly described as the consequence of the changes of polarity, degree of hydrogen bond, and viscosity;11 the solvent having a low polarity, low hydrogen bonding ability, and high viscosity could retard the formation of seed leading to increase the final size of SNPs. It was also reported that silica sources with the long or bulky alkoxy groups resulted to generate the large sized SNPs due to the steric effect which decrease the rate of hydrolysis. 11 On the other hand, it was well known in silicon chemistry that the alkoxy groups of silicon compounds could be exchanged in alcohol solution, especially in the presence of acid or base catalysts, and the rate of hydrolysis and condensation reactions were also affected by the character of alkoxy groups.12-14 Therefore, we investigated the alkoxy exchange reactions in the conditions where SNPs were usually synthesized and found a new factor to give simpler and more precise control over their siz...

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Sol-gel transition in simple silicates II

Cited by 496 publications

References 9 publications

Nanocrystalline materials and coatings

Nanocrystalline materials and coatings

Immobilization of Proteins in Silica Gel: Biochemical and Biophysical Properties

Precise Size-control of Silica Nanoparticles via Alkoxy Exchange Equilibrium of Tetraethyl Orthosilicate (TEOS) in the Mixed Alcohol Solution

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