Optical Chemical Sensors and Biosensors (incl. Materials for Sensors)

An optical sensor for aqueous 1-butylamine is presented which combines two novel techniques: A fluorescent indicator dye (the "fluoro reactand") embedded in a thin polymer layer performs a reversible chemical reaction with the analyte, causing changes in luminescence intensity. At the same time, inert phosphorescent beads dispersed within the polymer layer provide luminescence signals that act as an internal reference for the indicator dye. As a consequence, the optical sensor is independent of light source fluctuations, ambient light, drifts in optoelectronic set-up or optical fiber bending. The figure shows the effect of butylamine on the emission spectra of the sensor membrane. 347. Dual Lifetime Referencing (DLR) A New Scheme for Converting Fluorescence Intensity into a Frequency-Domain or Time-Domain Information, I. Klimant, Ch. Huber, G. Liebsch, G. Neurauter, A. Stangelmayer, O. S. Wolfbeis, in: New Trends in Fluorescence Spectroscopy, B. Valeur, J. C. Brochon (eds.), Springer Verlag, Berlin (2001), chap. 13, , pp. 257-274. Abstract. We present a new and universally applicable scheme for converting fluorescence intensity into a phase shift, a signal that is hardly affected by many potential interferents. It is based on the addition of a luminescent reference dye having a decay time much longer than that of the fluorescent indicator. This scheme is called Dual Lifetime Referencing (DLR). In the preferred case of using a phosphorescent luminophore as the reference dye, the time domain is in the microsecond range, so that modulation frequencies in the lower kHz range are adequate. This enables the use of inexpensive optoelectronic devices and thus also provides cost advantages. In this overview, the fundamentals of time-domain DLR and frequency-domain DLR are demonstrated and the potential of the new method is assessed with respect to alternative schemes. Phase angle (φm) and the intensity ratio of the indicator dye (Aind) and reference luminophore (Aref) are related as shown in the following equation: