BRITO, Giancarlo Esposito de Souza
Preparation of materials from precursor sols produced through sol-gel processes and characterization of structures and structural changes from a starting solution, through the process of gelification (sol-gel transition), to the resulting xerogel (dry gel). Experimental techniques of low-angle X-ray scattering are employed. This method allows to obtain:
- Sols that can be deposited as thin films and nanostructured multilayers.
- Self-assembled mesoporous structures obtained by EISA (evaporation-induced self-assembly) which are employed in the preparation of films with periodic mesoporous structures formed through self-assembly of surfactants.
- Thin films with optical/electro-optical properties, displaying selective electrochromic absorption.
- Sols based on biocompatible iron oxide-hydroxide nanoparticles used in magnetic resonance imaging for the diagnosis of liver and spleen cancer.
X-ray absorption and diffraction techniques also used in the characterization of polycrystalline xerogel powder.
CRAIEVICH, Aldo Felix
Nanostructured materials: Structure and mechanisms of transformation. Description:
Various types of nanostructured materials are studied in solid and liquid states and the structural transformations that occur in the corresponding processes of production. We place a focus, in particular, on structure on a nanometric scale, and on processes of aggregation in liquid colloidal solutions, proteins in solutions, gels, porous xerogels (high-volume and thin films), hybrid nanocomposites and glasses containing quantum dots (semiconducting and metallic nanocrystals). By means of the experimental technique of small-angle X-ray scattering (SAXS), and using X-ray beams produced by synchrotron, the structural transformations are studied in situ to determine related transformation mechanisms. Characterization of the structure of aggregation mechanisms is made, in most cases, through the application of concepts of fractal geometry. The SAXS and WAXS (wide angle X-ray scattering) techniques are used together to establish relevant correlations between structures on a nanometric and atomic scale. The above described structural characterizations are employed in order to explain the physicochemical properties of the materials studied.
Site of the Crystallography Group of the Department of Applied Physics:
FANTINI, Marcia Carvalho de Abreu
Development of new materials in bulk, thin films and formed by nanoscopic dimensions with morphologic, optical, electric and structural properties that are adjustable for each specific application. The systems are fundamentally investigated using X-ray methods, including diffraction (XRD), scattering (SAXS) and absorption (XANES and EXAFS), employing both conventional X-ray sources and X-ray synchrotron radiation. They are:
1. Organized mesoporous materials prepared with triblock copolymer templates.
2. Polar lipids (monooleines) for controlled release of pharmaceuticals.
3. Nanoceramic materials based on zirconium (ZrO2), used as electrodes and solid electrolytes in solid oxide fuel cells (SOFC).
Visit the group's page: http://web.if.usp.br/cristal
Study of nanomaterials using scattering techniques (X-ray diffraction, low-angle X-ray and light scattering): micellar systems, crystalline liquids with an emphasis on phase transitions, proteins in solution (effects of additives, temperature and solvents), protein/surfactant/polyelectrolyte/polymer complexes, vesicles and model-membranes (effects of the addition of pharmaceuticals, photoactive molecules, peptides) and magnetic nanoparticles in solution.
MORELHÃO, Sérgio Luiz
* I. HYBRID RECIPROCAL SPACE. Epitaxy is a process which is fundamental to the technology of semiconductors, enabling the growth of one crystalline lattice upon the other with different lattice parameters. We study the phenomenon of X-ray diffraction of epitaxial films [Journal of Applied Crystallography 40, 546-551 (2007)].
* II. SYNCHROTRON X-RAY IMAGING. With the dissemination of synchrotron facilities around the world, which started decades ago, the exploration of properties of radiation-matter interaction of hard X-rays for imaging of biological tissues has become a very active research area. In this research we show the relevance of synchrotron X-ray imaging to the study of ophthalmologic diseases, especially to cataract, which is the most common of them [Medical Physics 33, 2338-2343 (2006)], and search for new applications.
* III. X-RAY PHYSICS IN CRYSTALLOGRAPHY AND NANOTECHNOLOGY. Crystalline materials and nanostructured semiconductive surfaces (quantum dots) are investigated through X-ray multiple diffraction [Physica status solidi A 204, 2548-2554 (2007)].
* For more details about those research lines, consult the Digital Library of USP: