Silica xerogels of tailored porosity as support matrix for optical chemical sensors. Simultaneous effect of pH, ethanol:TEOS and water:TEOS molar ratios, and synthesis temperature on gelation time, and textural and structural properties

Estella, Juncal; Echeverría, Jesús C.; Laguna, Mariano; Garrido, Julián

doi:10.1016/j.jnoncrysol.2006.12.006

Cited by 77 publications

(47 citation statements)

References 38 publications

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“…If the curing is performed under atmospheric conditions, a xerogel is obtained [71], whereas under supercritical conditions (high temperature and pressure), the final matrix is called aerogel. In the first case, the gel suffers significant morphological changes due to the evaporation of the solvents; this process produces mechanical stress in the structure due to the vaporization of the solvents through the pores.…”

Section: Chemical Reaction and Morphologymentioning

confidence: 99%

Fiber Optic Sensors Based on Nanostructured Materials

Elosúa

Hernáez

Matı́as

et al. 2014

Springer Series in Surface Sciences

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Fiber optic sensors have been developed taking advantage on the synergy between the properties of nanostructured materials and the ones that characterize an optical fiber. The mechanical properties of optical fiber introduce some restrictions to the techniques used for the deposition of materials. As an alternative to the classical deposition procedures, wet coating techniques have been successfully applied in these cases. The current chapter put emphasis on materials that can be incorporated using wet coating techniques. The first one presented is the multilayer based nanostructures: among the different alternatives, we have focused on materials prepared with the Layer-by-Layer technique. Another type of products used for the fabrication of optical fiber sensors is sol-gel matrices, which are made of silica, so that its optical properties are similar to the ones of an optical fiber. The other two described type of products have focused the attention of many researchers in the recent years. Firstly, materials with an enhanced selectivity are presented: the molecularly imprinted polymers (MIPs). Finally, sensors based on metallic nanolayers and particles are presented. All these materials and techniques have acquired a great importance in the field of optical fiber sensors due to their versatility and the good features that offer.

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Section: Chemical Reaction and Morphologymentioning

confidence: 99%

Fiber Optic Sensors Based on Nanostructured Materials

Elosúa

Hernáez

Matı́as

et al. 2014

Springer Series in Surface Sciences

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“…This method is frequently adopted in membrane synthesis or membrane pore modification due to its controllability and homogeneity [24,30,[36][37][38], and it includes various steps such as sol preparation, gel formation, drying and thermal treatment. Many types of silicon alkoxide precursors have been utilized, but the clear majority of research describes work using tetraethoxysilane (TEOS) [39][40][41]. The sol gel synthesis has been well described in a variety of reference materials [42], and so briefly it involves the hydrolysis (Equation (3)) and condensation reactions (Equations (4) and (5)) of a metal alkoxides to form a network.…”

Section: Features Of Silica Based Membranes For Desalinationmentioning

confidence: 99%

Microporous Silica Based Membranes for Desalination

Elma

Yacou

Wang

et al. 2012

Water

103

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Abstract:This review provides a global overview of microporous silica based membranes for desalination via pervaporation with a focus on membrane synthesis and processing, transport mechanisms and current state of the art membrane performance. Most importantly, the recent development and novel concepts for improving the hydro-stability and separating performance of silica membranes for desalination are critically examined. Research into silica based membranes for desalination has focussed on three primary methods for improving the hydro-stability. These include incorporating carbon templates into the microporous silica both as surfactants and hybrid organic-inorganic structures and incorporation of metal oxide nanoparticles into the silica matrix. The literature examined identified that only metal oxide silica membranes have demonstrated high salt rejections under a variety of feed concentrations, reasonable fluxes and unaltered performance over long-term operation. As this is an embryonic field of research several target areas for researchers were discussed including further improvement of the membrane materials, but also regarding the necessity of integrating waste or solar heat sources into the final process design to ensure cost competitiveness with conventional reverse osmosis processes.

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“…Indeed, either inorganic glasses or organic-inorganic hybrid materials can be easily obtained under mild conditions (T < 100 °C) starting from a low-viscosity solution containing metal alkoxides alone or mixed with organically modified alkoxysilanes or with suitable polymers. Sol-gel process key parameters like reactant formulation, catalyst, water content and reaction temperature, can be exploited to produce a large variety of materials whose properties can be finely adjusted to tailor the physicochemical properties of the final solid in order to optimize sensor performances (Wen, 1996;Estella, 2007).…”

Section: Introductionmentioning

confidence: 99%

“…Alkoxysilanes are most frequently used as precursors of inorganic phases, and the resulting inorganic silica glasses are porous matrices, that can be characterized by tailored porosity (Wen, 1996;Estella, 2007). Compared with pure organic polymers, sol-gel inorganic glasses can offer some advantages: higher stability, optical transparency down to 250 nm, feasibility of direct coating on glass and silica fibers.…”

Section: Introductionmentioning

confidence: 99%