Physical Chemistry of Materials

Research topics

Nanophosphors

The project focuses on the synthesis and characterization of nanophosphors for applications in the lighting, imaging and therapeutic field. The research aims to develop of oxide nanoparticles (e.g. Y2O3, ZrO2, Bi2O3, Al2O3, CeO2 or mixed oxides) doped with rare-earth ions for optical applications and to model of the optical mechanisms involved (e.g. upconversion and downconversion energy transfer). The loading of such systems in a suitable carrier, like mesoporous silica nanoparticles, can endow the possibility of using the nanoparticles in imaging systems in nanomedicine. Moreover, these nanoparticles work well as sensitizer in the photodynamic therapy in combination with ROS generator molecules.

Theranostic systems based on non-toxic quantum dots

Copper indium sulfide (CIS) quantum dots (QDs) have proven to be a valid alternative to commercially available high quality quantum dots, based on cadmium, selenium, lead, and other relatively toxic elements. Because of their intrinsic non-toxicity , CIS QDs are of interest for biomedical applications. Furthermore, they exhibit absorption and emission which can be finely tuned to fall in the therapeutic window (i.e. between 650-1300 nm), a feature which turns to be useful when optical imaging is foreseen as diagnosis method. The embedding of these QDs in a silica shell through a sol-gel method, which involves the hydrolysis and condensation of organic precursors of SiO2 (Stöber method), can impart biocompatibility and improved stability to the nanocrystals. Also, the silica surface offers further functionalization possibilities, using a variety of moieties such as PEG and small peptides. These molecules endow the nanoparticles with stealthing properties (substantial invisibility to the immune system) and active targeting abilities (selectively recognize cancerous cells), respectively. The silica shell can be synthesized also as a mesoporous material, which allows for further impregnation of drugs or small molecules in the pores, such as other contrast agents for different diagnostic methods. Eventually, molecules able to respond to external stimuli (e.g. pH and temperature changes) attached in the proximity of the pores can act as nanovalves, to selectively control the release of the loaded drug in the site of the unhealthy tissue.

Modified silica nanoparticles

In our group, we are developing chemical-physical surface modifications of silica nanoparticles in order to impart specific properties such as: tunable charge, colloidal stability in various media, and active targeting and stealth properties.
The aim of the research is to exploit the use of simple groups (e.g. amines, thiols, carboxyls) which can be easily attached to the surface of the particles, to bio-conjugate more sophisticated molecules (metabolite and small peptides) or proteins (e.g. GFP, BSA, trypsin, haemoglobin). Another goal is that of creating a stable and reproducible system which is invisible to the immune system, so to avoid the premature clearance by the body once injected in the organism. The combination of these modifications is expected to give systems that can be used for biomedical purposes, as well as for in vitro assays.
The study of the superficial properties of the so-produced systems is carried out with electrophoresis analyses, Dynamic Light Scattering (DLS), UV-Vis spectroscopy, Infra-Red and Raman Spectroscopy, and Solid State Nuclear Magnetic Resonance (SS-NMR). The interaction of the modified nanoparticles with biological environment is tested through the study of the dissolution of the particles in simulated body fluids, cytotoxicity studies using different cell lines, haemolysis tests, and protein adsorption.

Advanced functional ceramic materials 1

Zirconia-based ceramics (ZrO2) are interesting materials for many applications fields, thanks to good mechanical, thermal, functional and wear resistance properties. Common employments for these materials are thermal barrier coatings (TBCs), dental and bone prostheses, high resistance laminates, solid oxide fuel cells (SOFCs), gas sensors and optical devices and catalysis. Nonetheless, few attention on the correspondent nanoscaled material has been put.

In general mesoporous oxide materials and nanomaterials, such as silica, are appealing to their high surface area. Moreover, mesoporous zirconia have many attractive properties, such as catalytic activity and selectivity, better chemical stability than alumina or silica, amphoteric and redox properties. With the exception of silica, the synthesis of other mesoporous oxide materials via a sol-gel route is not straightforward.

The already presented strategies involve either the use of a surfactant or co-polymer as a structure-directing agent (soft-template), or an inorganic material as the scaffold (hard-template). The major issues of these approaches lie in the moisture-sensibility and the rapid hydrolysis kinetics of the zirconium alkoxides (Zr(OR)4). Furthermore, the calcination process needed to remove the template in the former method determines the crystallization of the material, thus the loss of the pores network. Scaffolding procedures are time-consuming and the final materials are usually not homogeneous.

The aim of the project is the production of nanoscaled zirconia with high surface area synthesized with a facile sol-gel route. Both templating strategies will be investigated. 

Advanced functional ceramic materials 2

Zirconia phase transition, in particular the martensitic transformation from tetragonal (t-ZrO2) to monoclinic (m-ZrO2), is an interesting process subordinated at the presence of oxygen vacancies into the crystal lattice. This mechanism is that involved in the so-called “transformation toughening process” which makes zirconia-based materials so durable. The introduction of different polyvalent dopant cations, such as trivalent Y3+ and pentavalentTa5+, brings by the modification of the oxygen content in the matrix. 

We are currently investigating the effect of the introduction of these ions in the ceramic matrix, in order to assess the possibility of stabilizing specific phases with improved properties in terms of phase stability and mechanical properties.

Multifunctional materials based on Bi2O3

The project aims to synthesize Bi2O3 based materials for photocatalyitic and optical applications. The main interest concerns the optimization of the synthetic processes for the realization of low-dimensional systems (micro- and nano-particles, thin films and nanopowders) with the aim to manipulate the dimensions, the morphology and the crystalline structure. In addition to the traditional Pechini type sol-gel synthesis, polyol method, hydrothermal processes and core-shell synthesis one of the main lines of research is directed to green synthesis. In order to enhance the optical and photocatalytic properties bismuth oxide matrix will be loaded with metal ions (e.g. Ta, Zn, Ga, In, Ni, Cu, Ag) and rare-earth ions as dopants or to synthesize oxide heterostructures.