Gallucci, Noemi (2023) Hybrid nanostructure systems: physico-chemical properties and applications in biomedical and technological fields. [Tesi di dottorato]

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Abstract

In the last 50 years, researchers have been extensively studying how to exploit nanoparticles and nanostructured materials (NMs) in different fields. However, this is such a vast and varied area that comprehension of properties and applications of NMs is far to be complete, as nanoscience constitutes the meeting point of different disciplines, ranging from quantum physics to supramolecular chemistry, material science to biology, from medicine to agri-food. This Ph.D. project had two objectives: (i) to understand how modulation of geometric and energy parameters could induce the hierarchical organization of coated CeO2 NPs to amply photoluminescence properties; (ii) design and optimization of an aptasensor based on F-doped ZnO NPs. CeO2 NPs have been synthesized, varying synthesis temperature and capping agent, to study how the synthesis conditions could affect their physico-chemical properties. The capping agent is an amphiphilic molecule capable of modulating the shape and size of NPs, and, in turn, varying the properties of the final NMs. In this Ph.D. work, the effect of the length of alkyl chain of primary amines was investigated, using octylamine (C8), decylamine (C10), dodecylamine (C12), hexadecylmaine (C16), and oleylamine (C18), and performing the synthesis through the thermal decomposition method at three different temperatures, 150, 200, and 250 °C. Once studied the properties of coated CeO2 NPs, in terms of crystallinity, composition, size, shape, and photoluminescence, their self-assembly was induced by functionalization with oleic acid (OA) or sodium oleate (NaOA). Functionalization with NaOA led to the formation of disordered aggregates of CeO2 NPs, while OA induced the formation of ordered superlattices, with structures ranging from simple face centered cubic (FCC) to a complex pseudo hexagonal, known as C14 Frank�Kasper (C14 FK), phase. Finally, it was observed that an ordered superlattice of coated CeO2 NPs UNIVERSITY OF NAPOLI FEDERICO II POLYTECHNIC AND SCIENCE SCHOOL Department of Chemical Sciences 2 amplifies by about 400% the intensity of photoluminescence compared to disordered aggregates of the same NPs. These results open a route toward the design of complex system of NP superlattices with original physical properties for technological applications. On the other hand, in the case of ZnO NPs, the effect of several concentrations of a doping agent (from 0 to 20 % at) on their fluorescence properties was assessed, to optmize ZnO NP properties aiming at exploiting them as an optical transducer for the design of an apatsensor. The doping agent chosen was fluorine (F), capable of introducing itself in defects naturally present in the crystalline structure of ZnO NPs, increasing their fluorescence emission without changing their other physico�chemical properties. An extensive physico-chemical characterization of the various synthesized F�doped ZnO NPs has showed that 1% at F concentration is sufficient to increase the quantum yield of ZnO NPs of about 22%. Once chosen the best F-doped ZnO NPs in terms of optical properties, a protocol for formation of ZnO NP films able to act as an optical transducer has been developed. Different techniques showed that glass is the best film support, while a high concentration of the suspension (36 mg mL-1 ) and a low-speed rotation (1000 rpm) produce homogeneous film and complete coverage of the support. Finally, the physical immobilization of the LA27 aptamer was found to be a good strategy for interaction with the film, with a degree of aptamer detachment of 65%mol after 3 hours.

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