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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 acidfunctionalized 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%). Surfacesensitive 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.

Speciation of nanoparticles, that is, their differentiation based on size, shape and stabilizing shell is becoming important since their properties depend on these parameters. Nanoparticle‐imprinted polymers (NIPs) are a new approach that aims to selectively recognize nanoparticles based on their structural properties. In this study, monolayers of cellulose acetate (CA) accommodating gold nanoparticles stabilized with dodecanethiol (AuNPs/C12) are transferred onto indium tin oxide (ITO) by the Langmuir–Blodgett technique. One to five monolayers are assembled. Electrochemical oxidation dissolves the AuNPs/C12 to form cavities in the films, which fit the size and shape of the AuNPs/C12. Reuptake of the nanoparticles from a solution is successful using the imprinted films, whereas the control films containing only CA layers do not reuptake the AuNPs/C12. The NIPs are highly selective and other gold nanoparticles stabilized by other thiols are not recognized by the imprinted matrix.

Nanoparticles imprinted matrices (NAIMs) is a new approach, in which nanoparticles (NPs) are imprinted in a matrix followed by their removal to form highly selective voids that can recognize the original NPs. In this study, the effect of a sol–gel matrix on the imprinting and reuptake of gold nanoparticles (AuNPs) is examined. Specifically, indium tin oxide (ITO) films were modified with a positively charged polymer, on which the negatively charged AuNPs stabilized with citrate (AuNPs-cit) were adsorbed. This was followed by the electrochemical deposition of sol–gel matrices with different thicknesses and functional groups onto the ITO/AuNPs-cit. Electrochemical oxidation dissolved the AuNPs-cit and formed cavities in the sol–gel films, which fit both the size and shape of the AuNPs-cit. Reuptake of these NPs from an aqueous solution was successful using the imprinted films, whereas the non-imprinted films did not re-uptake the AuNPs-cit. Furthermore, the thickness of the sol–gel layers as well as the type of the silanes that were deposited play an important role on the recognition ability of the NAIM. Finally, we found that the NAIMs are selective, and larger AuNPs-cit were not recognized by the imprinted matrix.

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