The Matrix Effect on the Oxidative-Dissolution of Nanoparticle-Imprinted Polymers

Nanoparticle-imprinted matrices (NAIM) have emerged as a promising approach for the selective detection of nanoparticles (NPs) based on their size, shape, and surface chemistry. However, during the electrografting of aryldiazonium salts to form the organic matrix, conductive NPs can participate in the electrochemical reduction, thereby depositing the organic film on their surfaces. This coverage hinders the complete oxidative removal of the NPs and limits the efficiency of the imprinting process. In this work, we investigate the matrix effect on the oxidative dissolution of gold NPs (AuNPs) adsorbed on polyethylenimine (PEI)-modified indium tin oxide (ITO) electrodes. Linear sweep voltammetry and electron microscopy reveal that the electrografted matrix significantly suppresses oxidation of AuNPs, indicating partial coverage of the NPs by the organic film. To prevent matrix formation on the NPs, two protective strategies were examined: esterification of 3-mercaptopropionic acid-capped AuNPs and electrostatic adsorption of alkylamines. While esterification partially protected the NPs, strong adsorption of alcohol on the positively charged ITO surface led to severe electron-transfer blocking. In contrast, the electrostatic attachment of alkylamines effectively inhibited aryldiazonium reduction on the NPs while allowing the protective layer to be removed under mild alkaline conditions, thereby increasing AuNP oxidation efficiency by 58%. Following matrix formation and NP removal, the resulting nanocavities remained active (62% reuptake) and capable of NP reuptake, with the highest reuptake efficiency observed for butylamine-modified systems. These results provide insight into the role of the organic matrix during NP imprinting and demonstrate practical strategies to control matrix deposition on conductive NPs, thereby improving the efficiency of nanoparticle-imprinted sensing platforms.