Redox-Active Dyes And Their Voltammetric Application

Redox-active dyes are widely used in biomedical assays and conventional chemical analysis. Homogeneous electrocatalysis based on redox-active dyes is a new development of dye and is application oriented, but has yet received few attention in measurement science and sensing chemistry.  In this study we made efforts to apply homogeneous electrocatalysis for detecting some important small molecules of toxicological and environmental significance. The electrocatalysts employed in this study are azure A, azure B, azure C, thionyl acetate (TA), and neutral red ( NR).  Among these, TA and NR exhibit well-defined, reversible voltammetric redox peaks in wide pH range with various peak potentials, which indicate their fast electron exchange features at the solution/electrode interface.  Our further examination show that these fast interfacing processes offer great potential for catalysis, which was evidenced by significantly enhanced reduction peaks of TA and NR upon adding small molecules KIO_{3 ,}KClO₃ KBrO₃ ,NaClO₄ , NaIO₄  ,Na₃AsO₄ , in acidic media. A control experiment indicated that these analytes do not produce any appreciable redoxactive transition in the potentials examined.  Our mechanistic study revealed that the enhanced reduction peaks are merely from the dyes surface chemistry, yet their redox process are coupled with a homogeneous electrocatalysis.  Further, these cathodic peak ~ concentration plots displayed linear response at various concentration ranges. Our preliminary study thus shed great promise for the new detection of these compounds by catalysis. This work was supported by NASA-TSGC-NIP, SACP-UARP, and Welch Grant ( BJ-0027 ).