Catalysis and Nanomaterials Laboratory

9. M. S. Wong, J. N. Cha, K.-S. Choi, T. J. Deming and G. D. Stucky, "Assembly of Nanoparticles into Hollow Spheres Using Block Copolypeptides" Nano Lett. 2, 583-587 (2002). ACS Hot Article. DOI:10.1021/nl020244c

Various modes are being explored for the construction of functional materials out of nanoparticles. Despite these efforts, the assembly of nanoparticles remains challenging with respect to the requirement of multiple component organization on varying dimensions and length scales. We report here a room-temperature, wet chemical-based synthesis route in which silica and gold nanoparticles 10 nm) are cooperatively assembled with lysine−cysteine diblock copolypeptides into robust hollow spheres (diameter microns). The walls of the hollow spheres are composed of two distinct layers of silica and gold nanoparticles, and the hollow center is created without the use of a sacrificial core, emulsion phase, or hollow preformed substrate. Block copolypeptides designed with specific recognition sites for nanoparticles of various compositions provide a versatile approach for the hierarchical organization of nanoparticles into multidimensional composite arrays.

8. M. S. Wong and G. D. Stucky, "The Facile Synthesis of Nanocrystalline Semiconductor Quantum Dots" Mat. Res. Soc. Symp. Proc.; H. W. Hahn, D. L. Feldheim, C. P. Kubiak, R. Tannenbaum, and R.W. Siegel, Eds.; 2001 MRS Spring Meeting, Vol. 676, Y2.3-2.6 (2002).

Current synthetic techniques to high-quality quantum dots (“QD’s”) involve organometallic precursors that are hazardous and expensive and require they be rapidly injected into an extremely hot solvent to form the QD’s. A new method for synthesizing high-quality CdSe QD’s while circumventing these problems has been developed. Different cadmium salts were studied as Cd precursors alternative to dimethylcadmium. High-quality CdSe QD’s were found possible with cadmium acetate as the Cd precursor. Changes in solvent temperature and reaction time had a systematic effect on QD particle sizes and the accompanying optical properties. These preliminary results point to a general method for producing high-quality QD’s that is safer and much more versatile.

7. M. S. Wong, H. C. Huang and J. Y. Ying, "Supramolecular-Templated Synthesis of Nanoporous Zirconia-Silica Catalysts" Chem. Mater. 14, 1961-1973 (2002). DOI:10.1021/cm010076+

Thermally stable, mesoporous, and microporous zirconium-doped silica were prepared via supramolecular templating under low pH conditions. Zirconium loadings of up to 20 wt % were successfully incorporated into the porous silica-based framework, giving materials with very high surface areas, uniform pore sizes, and pore ordering. The zirconium cations were found dispersed throughout the material, and additionally, were preferentially located at the pore wall surface. The extent of Zr incorporation was found to be highly dependent on the synthesis pH and the nature of the Zr salt precursor and could be controlled by modifying the S+X-I+ synthesis route. These Zr-doped materials showed catalytic activity for 1-butene isomerization and cis-cyclooctene oxidation reactions.