In 1998, the U.S. food and beverage industry is expected to spend more than $300 million in diagnostic systems and reagents. Clearly, there are needs for real-time methods for monitoring, quantitating and performing differential analysis of gas mixtures from chemical processes and products. Although, various chemical instruments such as fast GC's have emerged recently, particularly for volatile organic measurements, it is obvious that presently available analytical instrumentation cannot meet commercial criteria such as high selectivity and sensitivity, rapid recovery times, long lifetimes if not single use, low cost, no reagents additions required and no sample preparation.The capability of light emission from silicon nanoparticles fabricated from porous silicon, raises several technologically important possibilities especially the fabrication of a truly integrated chemical sensor. The aim of the proposed program is to develop a sensitive and durable optical sensor based on porous silicon that can detect gas phase chemicals and odorants. Several different surfaces combined in an array and its attendant optics will be interfaced to an electronic nose instrument using a pattern recognition signal processing. The final form of the device will be compatible with the size and power requirements of a portable system and versatile enough to screen a wide range of chemicals.
Anticipated Results/Potential Commercial Applications of Research::An optical PL-sensing system with attendant data acquisition and electronics will be constructed. Sensitivity, stability and reproducibility will be qualified with hydrocarbon/ketone/ester mixtures or tertiary mixtures within a matrix at the 10-ppm level.The work will focus on three issues: stability of the porous silicon surface towards drift, reproducibility of the surface recognition elements from sample to sample, and sensitivity of the sensor suited for the intended application. Microfabrication issues for fieldable instrument will be planned. Small inexpensive analyzers for instantaneous monitoring could save the Food & Beverage industry more than $1 million per year per manufacturer in product recalls.
