Shell–Matrix Interaction in Nanoparticle-Imprinted Matrices: Implications for Selective Nanoparticle Detection and Separation

Abstract

Nanoparticle-imprinted matrices (NAIMs) are an innovative approach for the efficient and selective recognition of nanoparticles (NPs). The NAIM system comprises the preparation of thin films in which NPs are embedded as a template. The removal of the template forms nanometric voids, which are subsequently used for the selective reuptake of NPs identical to those imprinted. The recognition ability depends on several parameters such as the geometrical compatibility between the voids and imprinted NPs, the thickness of the matrix, and the supramolecular interactions between the matrix and the NP capping agents. Herein, we studied carefully the NP–matrix interactions in three NAIM systems, which were prepared by imprinting identical-sized AuNPs, bearing different carboxylic acid-functionalized thiols as capping agents, in a carboxylic acid-functionalized matrix. This experimental setup has enabled us to meticulously examine the selectivity of the NAIM systems driven by matrix–shell interactions. The three studied NAIM systems have shown high and selective reuptake ability once exposed to solutions of NPs stabilized with the same capping agent used for the imprinting process. In particular, the reuptake percentage of the originally imprinted AuNPs ranges from 50 to 80%, whereas the reuptake of AuNPs bearing different carboxylic capping agents than those imprinted was substantially lower (1–11%). Surface-sensitive polarization-modulation infrared reflection-absorption spectroscopy was utilized to correlate the selectivity of the NAIM systems and hydrogen bonding detected between the capping agents and the matrix. This study paves the way for the rational design of NAIM systems, which can be tuned according to the desired shell–matrix interactions and eventually applied in sensing and separation technologies.