TY - JOUR

T1 - The micro-optical ring electrode. 3: Transient photocurrent studies of photophysical-electrochemical and photophysical-chemical-electrochemical systems

AU - Andrieux, Fabrice P. L.

AU - Boxall, Colin

AU - O'Hare, Danny

PY - 2006/8/17

Y1 - 2006/8/17

N2 - The micro-optical ring electrode (MORE) is a photoelectrochemical device based on a ring microelectrode that uses the insulating material interior to the ring electrode as a light guide. In this paper, we describe the preparation and characterization of very thin ring MOREs with (ring inner radius)/(ring outer radius) > 0.99. Theoretically, we derive asymptotic analytical expressions for the time dependence of the diffusion-limited transient light-on photocurrent generated by two general types of photoelectrochemical systems: (a) the PE (photophysical-electrochemical) system, wherein the photoexcited species itself is directly detected on the ring; (b)the PCE(photophysical-chemical-electrochemical) system, wherein the photoexcited species undergoes a homogeneous electron transfer reaction prior to electrochemical detection. Experimentally, we establish that it is possible to use such MOREs to study the wavelength dependence of photocurrents derived from photoelectrochemically active systems, such as the Ru(bipy)(3)(2+)/Fe3+ PCE system, demonstrating the potential utility of the MORE as a selective electroanalytical probe. We also use our expressions for the time dependence of photocurrents at the MORE to derive values for the photoelectrochemical kinetic parameters of this system, including the rate coefficient for the back reaction of photogenerated Ru(bipy)(3)(3+) (0.115 s(-1)) and the quantum efficiency for the primary redox products, Ru( bipy)(3)(3+) and Fe2+, escaping cage recombination, phi(CE) = 0.099.

AB - The micro-optical ring electrode (MORE) is a photoelectrochemical device based on a ring microelectrode that uses the insulating material interior to the ring electrode as a light guide. In this paper, we describe the preparation and characterization of very thin ring MOREs with (ring inner radius)/(ring outer radius) > 0.99. Theoretically, we derive asymptotic analytical expressions for the time dependence of the diffusion-limited transient light-on photocurrent generated by two general types of photoelectrochemical systems: (a) the PE (photophysical-electrochemical) system, wherein the photoexcited species itself is directly detected on the ring; (b)the PCE(photophysical-chemical-electrochemical) system, wherein the photoexcited species undergoes a homogeneous electron transfer reaction prior to electrochemical detection. Experimentally, we establish that it is possible to use such MOREs to study the wavelength dependence of photocurrents derived from photoelectrochemically active systems, such as the Ru(bipy)(3)(2+)/Fe3+ PCE system, demonstrating the potential utility of the MORE as a selective electroanalytical probe. We also use our expressions for the time dependence of photocurrents at the MORE to derive values for the photoelectrochemical kinetic parameters of this system, including the rate coefficient for the back reaction of photogenerated Ru(bipy)(3)(3+) (0.115 s(-1)) and the quantum efficiency for the primary redox products, Ru( bipy)(3)(3+) and Fe2+, escaping cage recombination, phi(CE) = 0.099.

KW - SOLAR-ENERGY CONVERSION

KW - RUTHENIUM(II)

KW - TRANSPORT

KW - CELLS

KW - MICROELECTRODES

KW - LUMINESCENCE

KW - VOLTAMMETRY

KW - COMPLEXES

KW - BEHAVIOR

KW - CHELATE

U2 - 10.1021/jp0622785

DO - 10.1021/jp0622785

M3 - Journal article

VL - 110

SP - 16148

EP - 16156

JO - Journal of Physical Chemistry B

JF - Journal of Physical Chemistry B

SN - 1520-6106

IS - 32

ER -