Selective Recognition by Nanoparticle Imprinted Thin Films

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Assessing the presence, distribution and toxicological potential of man-made ligand shell-protected nanoparticles (NPs) becomes an increasingly urgent issue as the ability of preparing NPs with very interesting functional properties is tremendously surpassing the ability to predict toxicological hazards of those materials. It is generally accepted that toxicological hazards of nanomaterials stem not only from their elemental composition but to a very important extent from their size, shape and the chemical nature of the ligand shell. Consequently, toxicity testing involves a costly and large variety of assays including animal testing required before NPs can be used for technological application. There are no simple and cost-effective methods available for testing the presence of specific NPs in the environment.This project aims for providing a new, simple and cost-effective approach to selectively detect NPs and predict their interactions with biological materials using nanoparticle-imprinted matrices (NAIM) for NPs speciation. This concept has recently been demonstrated for the first time by the applicant for size discrimination of NPs. A matrix is formed in the presence of template NPs. After the release of the NPs, the imprinted cavities are able to selectively reuptake analyte NPs. Within the project, the approach will be significantly extended to explore selectivity towards different shells. Our work has demonstrated that NAIM should be made of thin films because this allows addressing entrapped NPs by the substrate electrode. Different chemistries will be used to obtain NAIMs in order to provide a large variability of surface groups to detect different ligand shell systems. The approaches include grafting by reduction of functionalized aryldiazonium ions around pre-immobilized NPs and matrices based on substituted poly(phenols) formed around NPs. Of special importance is the exploitation of self-limited growth of such polymers. We will post-functionalize the films in order to enhance the selectivity and to surpress nonspecific adsorption. In order to prevent overgrowing of the templates, we will use insulating NP as templates that are equipped with a shell similar to that of the targeted analyte NPs.Electrooxidation is used as primary mean for the NP detection. The efficiency of template removal will be followed by electrochemistry, scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS) and scanning force microscopy (AFM). The reuptake process will be studied by NP batches distinguished by size, shape and shell. The use of NPs with different cores will allow distinguishing different NP batches after their immobilization in the cavities of the NAIM by surface spectroscopy.