Electrochemically controlled assembly and logic gates operations of gold nanoparticle arrays

The reversible assembly of beta-cyclodextrin-functionalized gold NPs (beta-CD Au NPs) is studied on mixed self-assembled monolayer (SAM), formed by co-adsorption of redox-active ferrocenylalkylthiols and n-alkanethiols on gold surfaces. The surface coverage and spatial distribution of the beta-CD Au NPs monolayer on the gold substrate are tuned by the self-assembled monolayer composition. The binding and release of beta-CD Au NPs to and from the SAMs modified surface are followed by surface plasmon resonance (SPR) spectroscopy. The redox state of the tethered ferrocene in binary SAMs controls the formation of the supramolecular interaction between ferrocene moieties and beta-CD-capped Au NPs. As a result, the potential-induced uptake and release of beta-CD Au NPs to and from the surface is accomplished. The competitive binding of beta-CD Au NPs with guest molecules in solution shifted the equilibrium of the complexation decomplexation process involving the supramolecular interaction with the Fc-functionalized surface. The dual controlled assembly of beta-CD Au NPs on the surface enabled to use two stimuli as inputs for logic gate activation; the coupling between the localized surface plasmon, associated with the Au NP, and the surface plasmon wave, associated with the thin metal surface, is implemented as readout signal for "AND" logic gate operations.