Enhanced photoelectrochemistry in supramolecular CdS-nanoparticle-stoppered pseudorotaxane monolayers assembled on electrodes

A pseudorotaxane monolayer consisting of a supramolecular complex generated between cyclo-bis(paraquet-p-phenylene), (1), and the 1,4-bis(mercapto 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 × 10¹² 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.