Measurement of the concentration gradient-induced optical beam deflection in the vicinity of a microelectrode.

A measurement of the concentration gradient-induced optical beam deflection (OBD) in the vicinity of a microelectrode has been attempted. Platinum wires with diameters of 50 p.m and 0.5 mm were used as a working microelectrode and a counter electrode, respectively. The reference electrode was a Ag/AgC1 electrode. A ferricyanide/ferrocyanide redox reaction was used as a model electrochemical reaction. The applied potential of the Pt microelectrode was controlled using a polarographic analyzer. A probe beam from a diode laser was passed through the vicinity of the Pt microelectrode. Its deflection signal was detected by a position sensor consisting of a knife edge and a photodiode. Two kinds of potential sweeps were carried out. One was a potential step mode, the other was a triangle (cyclic voltammetry) one. Data for a simultaneous measurement of the current and OBD signals indicate that the present OBD method can be used for studying the concentration gradients in the vicinity of a microelectrode.