Surface-confined crown ether-capped gold nanoclusters: Investigation on their electrochemical behavior

A new ligand 18-crown-6-aminoethanethiol (18C6-AET), in which crown ether-ammonium ion interaction was exploited, had been designed and synthesized. An estimated HOMO-LUMO gap of 0.259 eV for the 18C6-AET complex indicated a definite interaction between 18C6 and AET. Consequently, multivalent interactions interplayed for the stabilization of gold nanoclusters resulting in confined cationic clusters having a diameter in 2-5-nm range in aqueous medium. The modified indium tin oxide electrodes with immobilized 18C6-AET-capped gold nanoclusters represented a metal-insulator-semiconductor junction across which the characteristic interfacial electron transport was unraveled. A heterogeneous electron transfer rate constant of 5.082 s-1 with a transfer coefficient of 0.51 was obtained for the quasi-reversible process, complying with a core-to-core electron hopping transport along with through-bond tunneling across the linker. © 2012 Springer Science+Business Media B.V.