Dottorato in SCIENZE CHIMICHE

Titolo della tesi: The Nanoparticles Point of View: Au, Ag, Pd, and Polymer-based Systems for Nanomedicine and Optoelectronics

This Ph.D work focussed on the synthesis and characterisation of metal nanoparticles (Au, Ag, Pd), methyl methacrylate-based polymeric nanoparticles and their hybrids. The synthesis of the nanoparticles was obtained carried out via wet chemical method, the reduction of metal precursor with sodium borohydride (MNPs) and surfactant-free emulsion polymerisation (PNPs). A critical parameter in order to fine tune their physico-chemical properties is the functionalisation of the surface of metal nanoparticles, which was carried out using hydrophilic and hydrophobic thiols, yielding isolated or interconnected nanoparticles. The obtained nanoparticles had small diameters and proved stable from a colloidal point of view, thus they were tested for different applications, in nanomedicine and optoelectronics. Hydrophilic gold nanoparticles, both functionalised with one and with a mixed thiol layer, were used as drug delivery probes, confirming their non-cytotoxicity and improving the cytotoxicity of drugs non-covalently loaded on their surface. Moreover, they were also used for colorimetric sensing of food adulterants. Mixed thiol systems were studied in depth by µ-liquid jet SR-XPS. Hydrophobic metal nanoparticles, both functionalised with mono- or dithiols, were synthesised and their properties in optoelectronics were explored. Extended networks of MNPs functionalised with an organometallic linker were synthesised and characterised in order to explore in depth the size of the nanoparticles and of the network and the chemical structure of both the linker and the nanoparticles. Isolated and interconnected nanoparticles networks were tested as chemiresistive sensors to assess their ability to respond to analytes in gaseous or vapour form, such as Hg0vap and BTX. Thin films with tunable morphology based on hybrid blends with P3HT and PLA of interconnected AuNPs were developed and their electrical behaviour was assessed. Polymeric nanoparticles based on MMA and DMMA were synthesised via surfactant free emulsion polymerisation, and they were efficiently loaded with 89Y3+ as a model for the radiotracer 90Y3+, their cytotoxicity was studied, and they were found to be non-toxic. Moreover, a dye, FITC isomer I, was physically encapsulated inside the PNPs as a proof of concept for the development of multimodal imaging agents. PNPs were also covalently linked to AuNPs by using p(MMA-co-UNTS) polymeric nanoparticles, exploiting the nucleation of AuNPs on the surface of PNPs thanks to the presence of a thiolate moiety, this hybrid system has the potential to be used in nanomedicine as a theranostic agent. The characterisation of these colloidal systems can be challenging, and a number of different techniques have been used in order to understand the structure, size, and stability of the nanosystems.