(25f) Detection of Gases On Biosensor Surfaces

A fractal analysis is presented for the binding and dissociation (whereever applicable) of different gases on different biosensor surfaces. Both single- and dual-fractal analysis are used. The dual-fracatal analysis is used only when the single-fractal analysis did not provide an adequate fit. Corel Quattro Pro 8.0 is used to fit the data. The fractal analysis is used to analyze (a) the binding of liquid petroleum gas (LPG) to zinc oxide films prepared by the spray pyrolysis method onto a glass substrate (Shinde et al., 2007), (b) the binding and dissociation of different ammonia concentrations in air to a sol-gel derived thin film biosensor (Roy et al., 2005), (c) binding and dissociation of different methanol concentrations (in ppm) to a polyimide thin layer biosensor (Manera et al., 2002), and binding to a nc-Fe3O4/Si-NPA (nanocrystal magnetite silicon nanoporous array)(Wang and Li, 2005).

The binding rate coefficients are quite sensitive to the degree of heterogeneity or the fractal dimension on the biosensor surface, for example, (a) the zinc oxide films sprayed on glass substrates for the detection of 0.2 volume percent LPG in the gas phase, (b) the binding of ammonia to a sol-gel derived thin film biosensor where the influence of pre-sintering temperature was analyzed,(c) the binding of different concentrtaions of ppm methanol in air to a polyimide thin layer biosensor (Manera et al, 2007), and and the influence of different carrier gases (nitrogen, air, and argon) for the detection of ammonia by an ammonia sensor.

The detection of different gases present in air and in different carrier gases using different types of biosensors provides one with an idea of what is available in the literature and what gases may de detected. Novel biosensor techniques are continuously being developed for the detection of even conventional gases such as ammonia. Hopefully, these novel biosensor techniques should help detect conventional and other gases at lower and lower detection levels; besides becoming more and more sensitive, robust, and reliable detection techniques.