ANNALES UNIVERSITATIS MARIAE CURIE-SKŁODOWSKA LUBLIN – POLONIA VOL. LX, 21 SECTIO AA 2005 Recognition elements for metal ions as parts of optical chemical sensors A. M. Kłonkowski, K. Kledzik, M. Gwiazda and M. Orłowska Faculty of Chemistry, University of Gdask, Gdask, Poland This paper focuses on chromoionophores and fluoroionophores immobilized or covalently attached in/on a matrix or support, respectively. Silica xerogel serves as the matrix and amino-modified silicate or mesoporous silicate (MCM-48) as the support. The studied materials prepared by sol-gel procedure can be treated as potential recognition elements for optical chemical sensors. Action of the recognition elements is based on absorption spectra changes or template effect for the chromoionophores and photoinduced electron transfer (PET) effect in the case of the fluoroionophores. 1. INTRODUCTION In general, a sensor is a device that detects or measures a physical property and records, indicates or otherwise responds to it [1]. While, a chemical sensor is defined as a device this responds to a particular analyte in a selective way through a chemical reaction and can be used for the qualitative or quantitative determination of the analyte [2]. Other term used in the sensor area is transducer, defined as a device that converts an observed change (physical or chemical) into a measurable signal. In chemical sensors it is an optical signal whose magnitude is proportional to the concentration of a specific chemical or set of chemicals. Recognition elements are the key component of any sensor device (Fig. 1). They impart the selectivity that enables the sensor to responds selectively to a particular analyte or group of analytes, thus avoiding interferences from other substances [3]. Optical transducer have taken a new lease of life with the development of fiber optics, thus allowing greater flexibility and miniaturization.