A process is described to modify the chemical structure of an aerogel under conditions which inhibit plasma formation within the aerogel pores, which process includes; (a) providing an aerogel with a pore size of less than 0.1.mu.; (b) exposing the initial aerogel to at least one gas selected from the group consisting of reducing gas, oxidizing gas, noble gas and combinations thereof, with the proviso that at least one reducing gas or one oxidizing gas is present; and (c) irradiating the combination of step (b) while maintaining the temperature to preserve the structural composition of the aerogel at a pressure of between about 0.1 and 54 Torr for between and about 5 and 960 minutes. This process produces a modified aerogel wherein the pore size does not allow for plasma formation within the pore. Chemical reactions occur within the pores of the aerogel of a nonplasma nature. These modified aerogels have a number of uses, including catalysts, ceramics, composites, chemical sensors, LED's and the like.
Transparent monolithic aerogels based on silica, the bioderived polymer chitosan, and coordinated ions are employed to serve as a three-dimensional scaffold decorated with metal ions such as Au, Pt and Pd ions. It has also been found that the metal aerogels, such as Au(III) aerogels, can be imaged photolytically to produce nanoparticles.
The artificial olfactory system is an ultra-sensitive and selective odor sensing system for the detection of odorant molecules down to the part per trillion level. The system includes multiple ultra sensitive frequency sensors, such as sensors based on piezoelectric substrates or micro-machined resonators, capable of detecting frequency changes resulting from the interaction of odorant molecules with the sensor. A coating applied to the sensor greatly increases the surface of interaction between the odorant molecules or biological agents and the sensor. An array of these sensors, each responding to the interaction of an odorant molecule species but in a different manner, results in different frequency shifts. An ultra sensitive frequency measurement device measures as small as part per billion shift in frequency. An intelligent processor based on artificial neural networks and other intelligent signal processing system detects, recognizes, and generalizes the signature resulting from the collective response of all the sensors.
