Schiattarella, Chiara (2020) Photoemissive inorganic nanomaterials: characterization and their application in biophotonics. [Tesi di dottorato]

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Abstract

In the recent years, nanostructured materials have greatly sparked the interest of the scientific community: their small size and tunable functional properties make them appealing as tools for biomedical applications. In this perspective, the thesis work summarizes three years of research in the field of nanotechnology applied to life sciences. Specifically, three nanomaterials were studied and exploited as platforms for applications in biophotonics: porous silicon, graphene oxide and zinc oxide nanostructures. The common feature is herein given by the property of characteristic photoluminescence from inorganic nanostructures whose bulk counterpart exhibits negligible emission. The fields of bioimaging and optical biosensing were mostly explored. In the first case, several luminescent materials are exploitable such as organic dye molecules, nanoparticle clusters and quantum dots. The latter exhibit characteristic properties such as slow cooling of hot carriers and tunable absorption/emission via relatively simple processing techniques. Nevertheless, the crucial issue of the high toxicity of conventionally employed semiconductors (CdTe, CdSe) needs to be overcome and the fabrication of alternative nanostructures with efficient emission based on biocompatible materials is highly desirable. Besides, another promising path that can be followed is to combine materials with relevant optical properties, aiming at developing nanodevices with multi-parametric optical transduction so to further boosting the applicability in the biosensing field. In that, proper surface chemistry modification strategies can be designed to achieve multiple advantages: stabilization in physiological environment, improved biocompatibility, overall preservation of the optical behaviour as well as addition of functional groups, which may provide binding sites to anchor functional biomolecules. The experimental results showed that substantial improvements have been achieved in both the aforementioned contexts. In fact, the characterized and optimized nanoplatforms were successfully employed for biophotonic applications, which include in vivo time-gated imaging of Hydra vulgaris using luminescent silicon nanostructures as label-free probes and multi-parametric optical biosensing for early diagnostics, with focus on Brugada syndrome, based on on-chip porous silicon/graphene oxide nanocomposites.

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