Electrochemical Detection of Silica Nanoparticles by Nanoparticle Imprinted Matrices

Nanoparticle (NP) toxicity is a severe environmental threat that calls for the development of novel field-effective platforms for NP detection and speciation according to their physicochemical properties. In this regard, nanoparticle-imprinted matrix (NAIM) is an innovative approach that enables the selective detection of NPs by their size, shape, surface chemistry, and composition. However, thus far, NAIM systems have mainly been used for detecting metallic NPs such as Au or Ag by electrochemical dissolution. Herein, we show that a facile electrochemical detection of non-conductive silica-NPs can be achieved by the NAIM approach. Specifically, the physical blocking of nanocavities was indirectly monitored by recording the redox activity of hexacyanoferrate(III) inside the nanocavities following exposure to silica-NPs using cyclic voltammetry (CV) and square wave voltammetry (SWV). This approach was examined for two different matrices based on phenol and 3-aminophenol monomers. Notably, we observed a dissimilar redox activity of hexacyanoferrate(III) upon reuptake, pointing to the importance of molecular interactions in NPs recognition. In addition, high-spatial-resolution vibrational mapping was conducted by IR scattering-type scanning near-field optical microscopy (IR-sSNOM) imaging to characterize the physical entrapment of silica-NPs by the matrix in the nanoscale.