Ingegnerizzazione e design di nanoparticelle core-shell di magnetite/silice

In the past decade the study of superparamagnetic nanoparticles has been intensively developed for many biomedical applications such as magnetically assisted drug delivery, MRI contrast agents, cells separation and hyperthermia therapy. All of these applications require nanoparticles with high magnetization, equipped also with a suitable surface coating which has to be non-toxic and biocompatible. In this master thesis, the silica coating of commercially available magnetic nanoparticles was investigated. Silica is a versatile material with many intrinsic features, such as hydrophilicity, low toxicity, proper design and derivatization yields particularly stable colloids even in physiological conditions. The coating process was applied to commercial magnetite particles dispersed in an aqueous solution. The formation of silica coated magnetite nanoparticles was performed following two main strategies: the Stöber process, in which the silica coating of the nanoparticle was directly formed by hydrolysis and condensation of suitable precursor in water-alcoholic mixtures; and the reverse microemulsions method in which inverse micelles were used to confine the hydrolysis and condensation reactions that bring to the nanoparticles formation. Between these two methods, the reverse microemulsions one resulted the most versatile and reliable because of the high control level upon monodispersity, silica shell thickness and overall particle size. Moving from low to high concentration, within the microemulsion region a gradual shift from larger particles to smaller one was detected. By increasing the amount of silica precursor the silica shell can also be tuned. Fluorescent dyes have also been incorporated within the silica shell by linking with the silica matrix. The structure of studied nanoparticles was investigated by using transmission electron microscope (TEM) and dynamic light scattering (DLS). These techniques have been used to monitor the syntetic procedures and for the final characterization of silica coated and silica dye doped nanoparticles. Finally, field dependent magnetization measurements showed the magnetic properties of core-shell nanoparticles were preserved. Due to a very well defined structure that combines magnetic and luminescent properties together with the possibility of further functionalization, these multifunctional nanoparticles are potentially useful platforms in biomedical fields such as labeling and imaging.

Synthesis and metal complexes of C2 symmetric ligands obtained from (R)-(+)-Betti and dialdehydes for asymmetric induction reactions

The aim of this master’s research thesis was the employment of an enantiopure 1,3-aminoalcohol, the 1-(α-aminobenzyl)-2-naphthol, known as Betti base, for the synthesis of some novel compounds which show a C2 symmetry. Some of these compounds, after derivatization, were used as ligands in association with transition metals to prepare some catalysts for enantioselective catalytic reactions. Some aminoalcohol (Salan-type) derivatives of these compounds were obtained upon reduction and in some cases it was possible to obtain complexes with transition metals such as Mn, Ni, Co and Cu. Furthermore a novel 6-membered analogue bisoxazoline ligand, 2,6-bis((R)-1-Phenyl-1H-naphtho[1,2-e][1,3]oxazin-3-yl)pyridine, was obtained and from it two Cu-complexes were prepared. The metal complexes were employed in some reactions to test the asymmetric induction, which was in some cases up to discrete values.

Dithienopyrrole-based materials: development of new polymeric derivatives

The possibility to control molar mass and termination of the growing chain is fundamental to create well-defined, reproducible materials. For this reason, in order to apply polydithienopyrrole (PDTP) as organic conjugated polymer, the possibility of controlled polymerization needs to be verified. Another aspect that is still not completely explored is bound to the optical activity of the PDTP, which bearing appropriate substituents may adopt a helical conformation. The configuration of the helix, built up from achiral co-monomers, can be established in an enantiopure way by using only a small percentage of the chiral monomer co-polymerized with achiral co-monomer. The effect, called “sergeants and soldiers effect”, is expressed by the nonlinear increase of the chiral response vs the ratio of the chiral co-monomer used for the polymerization. To date, this effect is still not completely explored for PDTP. In this framework the project will investigate, firstly, the possibility to obtain a controlled polymerization of PDTP. Then, monomers with different side chains and organometallic functions will be screened for a CTCP-type polymerization. Also a Lewis-acid based cationic polymerization will be performed. Moreover the chemical derivatization of dithienopyrrole DTP is explored: the research is going to concern also block copolymers, built up by DTP and monomers of different nature. The research will be extended also to the investigation of optically active derivates of PDTP, using a chiral monomer for the synthesis. The possibility to develop a supramolecular distribution of the polymeric chains, together with the “sergeants and soldiers effect” will be checked investigating a series of polymers with increasing amounts of chiral monomer.