Abstract: Chemical and biochemical sensors have become a valuable tool for the detection and quantification of a multitude of analytes. The ideal sensor and sensor system should be portable, inexpensive, easily fabricated, stable, and monitor and quantify several key analytes simultaneously, reversibly, and accurately. This dissertation focuses on the development of new photonically-based chemical and biochemical sensors and sensor systems by exploiting sol-gel processing chemistry, luminescence, and portable detection schemes. There are three main topics described in this document. First, I describe techniques to provide a diverse sensor response to an analyte. Secondly, I describe the development of low-cost, low-power and portable sensor systems. Finally, I report improved CO₂ sensing capabilities by advanced materials manipulation. Each Chapter is designed to be independent, and they may be read in any order.