Welcome to David Diaz Group web page, feel free to navigate through our web site following the links on the left.

David Diaz research group is located at the Department of Chemistry UNAM (National Autonomous University of Mexico) in Mexico City.

We have a general synthetic method of metallic and semiconductor nanoclusters (binary metal oxides and sulfides) obtained in colloidal dispersions and under mild reaction conditions. The synthesis reactions of these nanoparticles as well as the surface modifications take place in organic, polar and aprotic solvents. This general method of synthesis is novel, of low cost and extremely simple, producing very small and stable nanoparticles. Among the types of nanoparticles that we have prepared are: CdS, RuS₂, In₂S₃, Bi₂S₃, ZnO, Fe₃O₄, Cu₂O, CuO, TiO₂, SnO₂, and Ag. We have chosen such materials taking into account their natural abundance, price, and availability in Mexico. We have used different surface nanocluster modifiers (metallic carboxylates, ammines, PAMAM G_2.5 dendrimers, thiometallates, and metal transition cations) in order to stabilize the nanoparticles.

One of the challenges of our research group is the preparation of very stable colloidal dispersions, which should contain, as much as possible, small nanoparticles (2 to 7 nm of average diameter) with very narrow size distributions. We require very small nanoclusters because they exhibit a huge surface/volume ratio (for example, the RuS₂ nanoparticles prepared by our method, have S/V ratio = 2.5X10⁹ m^-1), this property is very appreciated in the field of catalysis due to the surface atoms since they have a lot of dangling bonds. Small nanoparticles are very reactive chemical species because the valence electrons are in a high quantum confinement regime.

For the characterization of the nanoparticles we have applied the electronic absorption and emission spectroscopies, in the UV-visible region, powder X-ray diffraction, and EDS. Equally, we use several microscopies (AFM, SEM, TEM and HR-TEM) to complete the characterization. In other cases we have applied ¹H-NMR. ESR, far-FTIR, and cyclic voltammetry.

We have used these colloidal dispersions successfully as catalysts in some processes such as the nitric oxide chemical reduction. We are able to grow silver and ZnO nanoparticles in pillared clays (kaolinite, hectorite and montmorillonite) as well as over several metallic oxide powders.

The great stability of the colloidal dispersions, with very narrow size distribution nanoclusters and small average diameters, as well as the great diversity of studied materials, allow applications in several technological fields, like: catalysis (hydrodesulfurization of oil derivate fuels), environmental engineering (catalytic degradation of NO and SO₂), the water electro-photocatalysis, inorganic pigments, corrosion, paints, solar cell thin films, luminescent materials, solar filters, storage magnetic devices and much more. Equally, we are ready to make the interaction of metal and semiconductor nanoparticles with biological materials like metallo-enzymes, structural proteins, RNA and DNA.