Chemical and physical research on nanomaterials has received an important scientific and technological attention.The small size and large surface area can lead to unexpected or dramatically different properties. Research efforts could provide breakthroughs in building a new class of highly structured materials at the nanoscale, where physical properties can be fine-tuned for specific applications to create high-performance devices in electrochromic, nonlinear optics, electronics, magnetism, electrocatalysis, catalysis and solar energy conversion where the quest for novel photovoltaics and carrier confining structures is stressed. Dr. Chemseddine is working and collaborating in two major areas.
I. Chemistry of Nanocrystals and Nanostructured Materials
One of the challenging objectives in research on next-generation materials is the structural control at all hierarchies of organization ranging from material texture to the level of atomic structure.Dr. Chemseddine research toward this objectiv is concerned with the developement of new wet chemical approaches to generate nanoclusters and nanocrystallites as intermediate building block for extended solid. Effort is devoted to an understanding of fundamental details which relate chemical reactivity to nucleation, growth and surface restructuration processes of condensed phases. This will enable create the physico-chemical conditions for the synthesis and processing of nanocrystals with desired size, shape, core structure and well defined surface.Furthermore, this research is taking advantage of different interactions, which may exist in the nanosize regime, between inorganic cores, capping ligands and solvents to generate well defined architectures, by self-assembly from suitably designed and functionalized nanocrystals.The solvent and capping ligands which are used as vehicle to achieve organization of inorganic cores are removed and a control of mass transfer, coalescence and sintering can be achieved fulfilling some morphological requirement.
The focus is on the processing of nanostructured semiconducting films (dense or porous) of TiO2 or ZnO to build a nanostructured and all solid state injection cell (see Gallery). Other materials such as CdS, WS2 are also under investigation. New type of nanostructured WO3 films (see gallery) are made and tested for their electrochromic properties.
II. Physical Properties of Nanoscale Materials
A quantitative understanding of the effects of size, shape, composition and capping ligands on the electronic and optical properies of free standing nanocrystals is one of the objectiv in physical research. Spectroscopic techniques are used to investigate these effects in combination with TEM, STM, AFM, IR, XRD and chemical analysis.
Optical absorption and photoluminescence sepectroscopy are used to probe interactions in solution between nanocrystals during aggregation or self-assemblig processes and in the solid state assemblies as transparent films. New and interesting opto-electronic properties are observed in CdS and TiO2 nanocrystal networks. For further reading see publications 4 and 7.