Electrified Au nanoparticle sponges with controlled hydrophilic/hydrophobic properties.

Molecularly imprinted Au nanoparticle (NP) composites for the selective binding of the electron acceptors N,N′-dimethyl-4,4′-bipyridinium, MV2+ (1), or bis-N-methylpyridinium-4,4′-ethylene, BPE2+ (2), are prepared by the electropolymerization of thioaniline-functionalized Au NPs in the presence of the electron acceptor molecules and the subsequent rinsing off of the imprint substrates. The electrochemical oxidation of the π-donor bisaniline units bridging the Au NPs yields the quinoid electron acceptor bridges, which are re-reduced to the bisaniline state. By the cyclic oxidation and reduction of the bridging units, they are reversibly switched between the π-acceptor and the π-donor states, thus allowing the electrochemically triggered uptake and release of the electron acceptors (1 or 2) to and from the imprinted sites. While the electron acceptors 1 or 2 bind to the imprinted sites via donor−acceptor interactions, these substrates are released from the Au NP matrices upon the oxidation of the bridges to...