Titania Aerogels as Sensor Platforms

Titania aerogels are generally considerably more opaque than are silica aerogels however, titania has other attractive properties including high photocatalytic ability. Many of the sensor approaches described above for silica aerogels are also applicable to titania aerogels (Chap. 7). To date, work in this area has been preliminary, more proof-of-concept rather than development of sensor devices. 

Morris et al. [14] demonstrated that the base-catalyzed, acid-modified (BCAM) approach they used for silica aerogels, and which showed considerable promise for entrapment of sensor moieties, could also be applied to titania aerogel preparation. 

Howell and Fox [26] have shown that it is possible to entrap molecular probes within titania aerogels. They used the fluorescence of pyrenyl groups, both tethered and unbound, to interrogate the porous Ti02 matrix. These probes were selected because pyrene and its derivatives are sensitive to the polarity of their environment and can form excited-state dimers (excimers) due to n stacking moreover, the fluorescence properties of pyrenyl monomers and excimers are well known [4]. Howell and Fox showed that there are local interactions between the dye species within the titania aerogel. They also used organic 

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