Nanostructured porous silicon -: Optical properties, surface modification and sensor applications

Porous silicon is a very attractive material due to its intense visible photoluminescence at room temperature. Its unique physical and chemical properties are determined by the porous structure where a nanosized silicon layer is formed during the electrochemical etching of crystalline silicon. So far, the high chemical reactivity of the porous silicon surface has prevented its extensive application in optoelectronics. Considerable effort has been put into the development of suitable techniques of stabilization. On the other hand, high chemical reactivity and sorption capacity of porous silicon represent the principal advantage for the construction of sensitive sensors of chemical species. This article provides a brief overview of the ongoing activities in the development of porous-silicon-based chemical sensors at the Charles University and at the Institute of Chemical Technology. So far, the detection of chemical species is based on the measurement of the changes in photoluminescence intensity and photoluminescence decay time, other complementary electrochemical and optical detection methods will follow in order to increase the selectivity of the detection. Another approach resulting in increased selectivity of sensor response utilizes the modification of porous silicon surface - either by physical adsorption or chemical derivatization - by various molecules with recognition properties. Due to the interdisciplinary nature of the research the involved scientists have built a network of collaborating laboratories specialized in various fields - material research, surface chemistry, design and synthesis of the molecules with recognition properties and sensor development.