NOVEL APPLICATION OF FLUORESCENCE BASED ON RHODAMINE B

Abstract

Quantization of small amount of substance is important for environmental, material, and life sciences. Currently the sophisticated instrumentation is able to carry out sub-micro or trace analysis under various levels at a cost. On the other hand, a simple, cost-effective, conventional reagent/technique involved method is still desired for popular use, “greener” measurement, and field implementation.  In this work we studied Rhodamine B (RB) – a dye that has been extensively used in biostaining or pH indicator, for its new analytical and sensory exploration. Fluorescence of RB was studied in non-aqueous media as well as aqueous media of broad pH range.  We found a new application of RB fluorescence for several conventional environmental pollutants including thiocyanate.  Thiocyanate does not generate luminescence under conditions examines.  Nevertheless, we observed the reaction between RB and thiocyanate and its subsequent fluorescence.  Moreover, contrary to the well-known fluorescence quenching, thiocyanate actually enhances the RB fluorescence.  Our preliminary mechanism study suggested enhancement due to the more accessibility of RB fluorescing group upon reacting with thiocyanate. In its analytical exploration, this enhancement is sensitive to thiocyanate and is linearly dependent of the analyte concentration for more than an order of magnitude. The presented novel thiocyanate assay thus possesses a promise for application in monitoring toxin level in heavy smokers. This work was supported by NSAS-TSGC-NIP, SACP-UARP, UHD-ORC, Brown Foundation, and Welch Grant ( BJ-0027 ).