Enhanced Photoelectrochemistry in Supramolecular CdS-Nanoparticle-Stoppered Pseudorotaxane Monolayers Assembled on Electrodes

A pseudorotaxane monolayer consisting of a supramolecular complex generated between cyclo-bis(paraquat- p -phenylene), ( 1 ), and the 1,4-bis(mercapto ethyloxy ethyloxy ethyl)benzene monolayer, ( 2 ), that is stoppered by CdS nanoparticles (3−5 nm) is generated on Au electrodes. The surface coverage of the supramolecular complex units and the associated CdS particles corresponds to 2.4 ± 0.2 × 10 -10 mole·cm -2 and 3 × 10 12 particles·cm -2, respectively. The photocurrent generated by the ( 1 )/( 2 )-CdS pseudorotaxane architecture is 8-fold higher than in a CdS-nanoparticle monolayer system that lacks ( 1 ). The enhanced photocurrent in the pseudorotaxane assembly is attributed to vectorial electron transfer of photoexcited conduction-band electrons to the threaded electron acceptor ( 1 ), which leads to charge separation and to the retardation of the electron−hole recombination process.