Gas Sensor Applications of Mesoporous Silicas

Silica is an attractive material for many sensing applications because of its high surface area, stability over a fairly wide range of pH (excluding alkaline), relative inertness in many environments, transparency in the UV-visible spectrum, and its morphological control (Melde et al. 2008). 

Pt(II)meio-tetra(4-)V-pytidyl)potphytin Pt(II) meio-tetra(3,5-dihydroxyphenyl)porphytin Pt(II) meio-tetra(3,5-di[()V-carbazyl)-n-octyloxyphenyl]) porphyrin Pt(II) meio-tetra(3,5-di[()V-carbazyl)-n-hexyloxyphenyl]) porphyrin Pt(II) meio-tetra(3,5-di[()V-carbazyl)-n-butyloxyphenyl]) porphyrin Zhang et al. (2005) Huo et al. (2006) 

Optical sensors based on UV-visible and fluorescence spectrophotometry and a visual color change in a material are other directions for mesoporous silicates application (Melde et al. 2008). Several examples of such sensors are presented in Table 8.2. Usually optical detection of gases in mesoporous silica-based sensors takes place through the use of an incorporated dye. In particular, oxygen sensing 

Experiments have shown that other types of gas sensors can also use mesoporous silicas as the sensing layer. For example, selective sensing of nitric oxide has been accomplished in the presence of carbon monoxide through the application of quartz crystal microbalance technology employing a cobalt phthalocyanine-modified sol-gel thin film (Palaniappan et al. 2006,2008). Electrochemical detection of nitrite has been accomplished using a metalloporphyrin-modified silicate material 

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