Spectroelectrochemical sensing based on multimode selectivity simultaneously achievable in a single device. 6. Sensing with a mediator

The use of a mediator to detect a nonabsorbing analyte during spectroelectrochemical modulation is demonstrated. The charge-selective composite film of Nafion-SiO2 was used to entrap the mediator, Ru(bipy)3(2+). The change in deltaA as detected by attenuated total reflection was then observed upon addition of the analyte, ascorbate. The effects of scan rate, concentration of mediator, film thickness, and analyte charge were studied to achieve optimal sensor conditions. The model sensor exhibited a linear range from 0.26 to 2.0 mM (R2 = 0.998).