T. Taniguchi et al., Photoelectrochemical response of polymer Langmuir-Blodgett films containing tris(2,2 '-bipyridine)ruthenium(II) complex, J PHYS CH B, 103(11), 1999, pp. 1920-1924
The tris(2,2'-bipyridine)ruthenium(II) complex (Ru(bpy)(3)(2+)) derivative
monomer was copolymerized with N-tert-pentylacrylamide and N-dodecylacrylam
ide. These copolymers, p(tPA-Ru) and p(DDA-Ru), formed stable condensed mon
olayers at the air/water interface, The monolayers could be successively tr
ansferred onto solid supports, yielding Y-type polymer LB films. The UV/vis
absorption spcctra of p(DDA-Ru) LB films indicated that Ru(bpy)(3)(2+) chr
omophore can be safely incorporated into the polymer monolayer with a conce
ntration of 3.9 x 10(-13) mol/cm(2), which is consistent with the results e
stimated from the surface pressure-area (pi-A) isotherms. The redox propert
ies of the LB films were investigated by cyclic voltammetry. The cyclic vol
tammograms of the monolayers on the electrode show a well-defined symmetric
al surface wave consisting of reversible redox peaks of Ru(bpy)(3)(2+) at v
arious potential scan rates. The surface concentrations of the redox active
Ru(bpy)(3)(2+) in the p(tPA-Ru) and p(DDA-Ru) monolayers were determined t
o be 3.3 x 10(-11) and 3.3 x 10(-11) mol/cm(2), respectively. On light irra
diation of the: LB films deposited on an ITO electrode in the presence of a
sacrificial electron donor (thiosalythilic acid) in electrolyte solution,
a large anodic photocurrent was observed with a rapid response to light int
ensity. The photocurrents as functions of light intensity, sacrificial dono
r concentration, and light wavelength (action spectrum) were measured. The
photocurrent in the p(tPA-Ru) LB monolayer is produced more efficiently com
pared with that in p(DDA-Ru) system, which is explained by the molecular en
vironment of Ru(bpy)(3)(2+) complex in their monolayers. The conversion eff
iciencies of photons absorbed by Ru(bpy)(3)(2+) to photocurrent in p(DDA-Ru
) and p(tPA-Ru) monolayers were about 0.8% and 1.1%, respectively. The phot
oenergy conversion system based on the photoinduced electron transfer with
Ru(bpy)(3)(2+) was discussed.