The Effect of Structural Isomers on the Recognition in Nanoparticle Imprinted Matrices (NAIMs)

Din Zelikovich, The Hebrew University of Jerusalem, Jerusalem, Israel (din.zelikovich@mail.huji.ac.il)
Daniel Mandler, The Hebrew University of Jerusalem, Jerusalem, Israel

In the last years, nontoxicity has become at the forefront of research due to its relevance and importance to the environment and human health. In spite of the fact that the exposure risk to engineered nanomaterials depends on their physicochemical properties including their surface chemistry, the regulations are based mainly on the particle size. Since the use of NPs is unavoidable, there is an urgent need for small, easy-to-use, and field-available sensors for the detection of NPs. Electrochemical detection methods would provide a cheap and easy tool to help characterize NPs based on their surface chemistry.

The selective recognition of nanoparticles (NPs) can be achieved by nanoparticle-imprinted matrices (NAIMs), where NPs are imprinted in a matrix followed by their removal to form voids that can reuptake the original NPs. The recognition depends on supramolecular interactions between the matrix and the shell of the NPs.

In this study, we describe a NAIM-Raman combined study where we examined the imprinting and recognition of AuNPs stabilized by the three isomers of mercapto-benzoic acid (MBA) in an aryl diazonium electropolymerized based matrix. Specifically, identical 10 nm diameter AuNPs stabilized by the 2, 3, and 4-MBA isomers were formed by ligand exchange reaction. Their adsorption on an indium tin oxide (ITO) surface modified by a positively charged polymer, e.g., polyethyleneimine (PEI), was followed by the controlled electrografting of a thin 4‑carboxyphenyl diazonium (ADS-COOH) film. The AuNPs were electrochemically dissolved and the reuptake of the different isomer-stabilized AuNPs was studied by electrochemistry, Raman spectroscopy, and other techniques.  We found that the NAIM system is highly selective and differentiates between the originally imprinted AuNPs and the other particles having the same Au core, but different isomer-stabilized AuNPs.