An informative subtlety of itemperature-jump or coulostatic responses for surface-attached species

Theoretical relationships are developed to describe the open-circuit respon ses associated with the indirect laser-induced temperature-jump (ILIT) meth od, a method for measuring fast electron-transfer rate constants of surface -attached redox species. The analysis is also applicable to data obtained u sing the coulostatic charge-injection method. The unique relationship betwe en k(m), the relaxation rate constant for the ILIT (or coulostatic) respons e, and E-i, the potential at which the system is initially poised, exhibits a surprising sensitivity to the values of k(0), E-i(0') (the standard rate constant and formal potential for the redox couple), alpha (the transfer c oefficient in the Butler-Volmer equation) and gamma (a dimensionless parame ter which is directly proportional to the total surface concentration of th e redox moiety). ILIT data for several examples of surface-attached ferroce ne moieties confirm the theoretically predicted k(m) vs E-i behavior. Value s of E-i(0') and gamma extracted from the ILIT data agree well with the val ues obtained from cyclic voltammetric data thereby confirming that the ILIT and cyclic voltammogram (CV) experiments are sampling the same ferrocene p opulation. (C) 2000 Published by Elsevier Science S.A. All rights reserved.