Sol-gel nanocomposites

Figure 5.6 Sol-gel nanocomposites are composed of an entrapped catalyst and an organically modified Si02 based matrix. Reproduced with permission from [60].

Figure 5.7 General schematic for the formation of a bio-doped sol—gel nanocomposite. Reproduced with permission from [59],...

Scheme 5.1 A systems approach to organic synthesis with doped sol-gel nanocomposites. (Reproduced from ref. 8a, with permission.)...

P. Gancitano, R. Ciriminna, M. Luisa Testa, A. Fidalgo, L. M. Ilharco and M. Pagliaro, Enhancing selectivity in oxidation catalysis with sol-gel nanocomposites, Org. Biomol. Chem., 2005, 3, 2389. 

Gill I, Ballesteros A. Immunoglobulin-polydiacetylene sol-gel nanocomposites as solid-state chromatic biosensors. Angew Chem Int Ed 2003 42 3264-3267. 

Sol-gel nanocomposites are further subdivided into six categories (1) com-positionaUy different nanocomposites, (2) structurally different nanocomposites, (3) both compositionally and structurally different nanocomposites, (4) nanocomposites of gels with precipitated phases, (5) nanocomposites of xerogels with metal phases, and (6) nanocomposites of inorganic gels and organic molecules. 

These are very intimate mixtures composed of two or more sohd phases that differ in composition and each with particle sizes of 10 to 20 mn. Solid phases of these dimensions produce sols when dispersed in a liquid. Two or more sols of different composition can be uniformly mixed and gelled to obtain compositionally different nanocomposites. Figure 13.1a shows the transmission electron microscopy (TEM) picture of a sol-gel nanocomposite of mulhte composition consisting of spherical sihca particles (20 nm) and rod-like alumina (boehmite) particles (approximately 7 nm). Such a uniform physical mixture can be distinguished from a homogeneous sol-gel material which does not show any nonuniformity because it is mixed on an atomic scale (Figure 13.1b). The compositionally... 

Keywords ionic liquid, redox electrolytes, sol-gel nanocomposites, hybrid electrochromic cells... 

Stathatos E., Lianos R., Zakeeruddin S. M., Liska P. and Gratzel M. (2003), A qnasi-solid-state dye-sensitized solar cell based on a sol-gel nanocomposite electrolyte containing ionic hqnid , Chem. of Materials 15, 1825-1829. 

Pope, E. J. A., Transparent sol-gel nanocomposites, presented at 95th Annual Meeting Am. Ceram. Soc., Cincinnati, OH, April 18-22, 1993. 

Kasemann, R, Schmidt, H. 1994. Coatings for Mechanical and Chemical Protection Based on Organic-Inorganic Sol-Gel Nanocomposites. New J. Chem., 18, 1117. 

The preparation of nanocomposite aerogels made out of zero-valent metal or alloy nanoparticles in an insulating aerogel matrix has attracted a great deal of effort in view of the preparation of materials for catalysis, biomedicine, optoelectronics, and sensors. As it is the case for aU sol-gel nanocomposites, silica is by far the most investigated matrix for supporting metal/alloy nanoparticles, although alumina, titania, chromia, and polymer supports have also been proposed. 

The metal alkoxides affect substantially these reactions. Thus Ti(OPr )4 and OV(OPr )3, cocondensates act as catalysts in transesterification of tetramethoxy- and tetraethoxysilanes (TMOS and TEOS, respectively) during sol-gel nanocomposite preparation. ... 

Toledano, R. and Mandler, D. (2010) Electrochemical codeposition of thin gold nanoparticles/sol-gel nanocomposite films. Chem. Mater., 22, 3943—3951. 

Some details about characterization of sol-gel materials by IR and Raman spectroscopy have been provided in Chapters 4 and 5 of the Handbook of Sol-Gel Science and Technology II [25,26]. In order to avoid the repetition of the same contents in this chapter, some representative results of new developments are reviewed, emphasizing results of optical spectroscopy methock for sol-gel nanocomposite films and planar waveguides. 

This chapter is structured as follows Section 46.2 provides a brief introduction to electrochemical sensors. Section 46.3 presents three different approaches to prepare sol-gel nanocomposites for electrochemical sensing applications, giving specific examples of each of them. In Section 46.4, different types of electrochemical transducers that can be prepared using the sol-gel material fabrication processes, together with the electrochemical detection mechanisms applied, are described. Section 46.5 gives an overview of the recent literature on sol-gel nanocomposites as electrochemical sensors of different types of analytes. This chapter concludes by summarizing the main conclusions and discussing some future prospects of sol-gel nanocomposites for electrochemical sensor applications. 

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