Grafting of oligoaniline on CdSe nanocrystals: spectroscopic, electrochemical and spectroelectrochemical properties of the resulting organic/inorganic hybrid

Abstract

We have synthesised a new organic/inorganic hybrid, in which electroactive aniline tetramer is grafted on the surface of quasi-monodispersed CdSe nanocrystals. The grafting reaction consists of two steps. First initial nanocrystal surface ligands (TOPO) are exchanged for 4-formyldithiobenzoate linker ligands, which contain an anchor function (the dithioate group) and an aniline grafting function (the aldehyde group). The condensation reaction between the primary amine group of aniline tetramer and the aldehyde group of the linker ligand results in the grafting of the former with simultaneous formation of an azomethine linkage between both reagents. The grafting reaction is nearly quantitative as demonstrated by ¹H NMR, FTIR and XPS studies. Voltammetric, UV-visible and EPR spectroelectrochemical studies of the hybrid compound show that after the grafting process the polyconjugated molecule retains its electrochemical activity i.e. electrochemical switching between the completely reduced state (leucoemeraldine), the semi-oxidised state (emeraldine) and the completely oxidised state (pernigraniline) is possible.