Array of opto-chemical sensors based on fiber-optic spectroscopy

A compact, flexible platform for reading out the variation of the optical absorption spectra in the visible range in a number of sensing materials is illustrated in this paper. This apparatus is based on an integrated spectrophotometer, an array of suitably controlled LEDs, optical fibers to carry and collect light, and a mechanical arrangement that makes possible the measurement, in sequence, of up to 15 different sensing layers. The unit was tested with a number of metalloporphyrins, known for their outstanding sensorial and optical properties. Data were analyzed using a multiway chemometrics approach. In this regard, a methodology to investigate the properties of an array of chemical sensors is introduced. This approach allowed an evaluation of the role played in the array by each sensing material in each spectral region to be performed. The analysis revealed interesting insight into the classification properties of the sensor array and the interaction mechanisms of porphyrins. The set of metalloporphyrins showed a variety of interaction mechanisms, and the relation of these mechanisms to the structure of the metalloporphyrins was evidenced by an accurate interpretation of the loadings of the multiway analysis.