Silicic acid sensor

Segmented gas-liquid (Taylor) flow was used for particle synthesis within the liquid slugs. Tetraethylorthosilicate in ethanol was hydrolyzed by a solution of ammonia, water and ethanol (Stober synthesis) [329]. The resulting silicic acid monomer Si (OH)4 is then converted by polycondensation to colloidal monodisperse silica nanoparticles. These particles have industrial application, for example, in pigments, catalysts, sensors, health care, antireflective coatings and chromatography. 

Surface reactivity (e.g., acid-base properties, ion-exchange behavior, and ability to selectively complex metal cations) may be modified by appropriate choice of precursor metals, by derivitization with organic ligands, or by reactions of the surface with metal halides, metal alkyls, etc. (See Chapter 10.) Combining microstructure control (demonstrated for silicates) with control of surface reactivity should lead to many appiications for porous films in the areas of sensors and catalysis. 

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