Nanoparticle-Imprinted Matrices as Sensing Layers for Size-Selective Recognition of Silver Nanoparticles

This study extends the concept of nanoparticle-imprinted matrices (NAIMs) to systems in which template nanoparticles (NPs) are immobilized on a conducting surface and a polymer matrix is built around them before the release of the template NPs. Specifically, citrate-stabilized AuNPs, 40 nm in diameter, were bound to a 3-aminopropyltriethoxysilane (APTES)-modified indium tin oxide (ITO) electrode at pH 5. Subsequently, a polymer matrix was generated by electropolymerization of a self-inhibiting poly(phenol) (PPh) layer. The template AuNPs were removed either by electro-oxidation of the Au core during linear sweep voltammetry (LSV) in Cl⁻-containing aqueous solution or by chemical oxidation in aqueous KCN solution. After template removal, remaining nanocavities were found to be size-selective in the competitive reuptake of analyte NPs, as demonstrated by the preference for citrate-stabilized silver nanoparticles (AgNPs) with 20 nm diameter over AuNPs with 50 nm diameter. The remaining nanocavities and their size-recognition ability were examined by scanning electron microscopy and LSV. Complementing studies by X-ray photoelectron spectroscopy and scanning force microscopy corroborated the template embedding, template release, and analyte NP uptake.