Spectrally encoded porous silicon 'smart dust' for chemical and biological sensing applications

This thesis describes the construction of spectrally encoded porous silicon particles and the use of these materials in chemical and biological sensing applications. The particles are called "smart dust" because of their microscopic size and ability to sense their environment and relay useful information to the macroscopic world.; The first chapter of this thesis provides an introduction to "smart dust" and the properties associated with these devices and materials. A discussion of sensing with porous silicon and of the utility of encoding microscopic materials is included. The second chapter includes a more detailed discussion of different encoding techniques and their relative advantages and disadvantages. A method for spectrally encoding porous silicon "smart dust" particles is described and its usefulness in a simple bioassay is demonstrated. In the third chapter, it is shown that these "smart dust" particles not only bear a unique and identifying code, but also have the capability of performing sensing functions.; In the fourth chapter, a new method for detecting chromophore activity is described using porous silicon rugates. More complex encoding is used to accomplish this goal. An indicator dye is incorporated into the porous silicon matrix demonstrating that the absorption properties of the dye interact with the spectral features of the host matrix.; In chapter five, it is shown that encoding techniques similar to those used in porous silicon can be extended to other semiconductors. Periodic multilayered structures are constructed in indium phosphide for biosensing applications. While the mechanism for constructing these materials is quite different from that used for silicon, the result is an similarly encoded material with useful sensing capabilities.