Nanoparticle Engineering: Multifunctional Microcapsules and Bimetallic Environmental Catalysts
报告人:
Michael S. Wong
Department of Chemical and Biomolecular Engineering Department of ChemistryRice University
报告时间:
2007-05-25 14:30
报告地点:
工物馆324东会议室
主办单位:
化学工程系
简介:
With size-dependent properties that are vastly different from those of corresponding bulk solids, nanoparticles (NPs) can be made in a variety of compositions, sizes, and even shape, as a result of the advances made in synthesis chemistry over the last two decades. The full potential of NPs (and NP-containing materials) for applications remains unrealized, though, due to critical knowledge gaps in our ability to exploit their nanoscale properties and our ability to scale up their production in an economical and environmentally friendly manner. My research group's efforts focus on filling in these "gaps" through the rational design of application-specific, NP-based materials and the development of scalable synthesis techniques that lead to these materials.
In this talk, I will discuss our successful efforts in inducing the formation of microcapsule structures out of NPs and polymers, and our current work in understanding the NP assembly process. We recently discovered that, under specific solution conditions, cationic polyelectrolytes can induce negatively-charged silica NPs to form micron-sized hollow spheres rather than the randomly structured precipitate that would ordinarily result from flocculation. The synthesis conditions (room temperature, atmospheric pressure, near-neutral pH, water solvent, rapid formation) allow water-soluble compounds to be encapsulated easily and without damage, and the microcapsule formation process to be potentially scaled up.
Trichloroethene, an industrial solvent, is one of the most hazardous pollutants in US groundwaters. Palladium (Pd) catalysts are known to catalyze the hydrodechlorination of trichloroethene in water, at room temperature, and in the presence of hydrogen. We recently discovered that palladium-on-gold nanoparticles (Pd/Au NPs) can be two orders of magnitude more active than Pd supported on alumina on a per-Pd gram basis. I will discuss our progress in understanding how the gold enhances the Pd catalytic activity so dramatically, and the applicability of this catalyst for the water-phase hydrodechlorination of other chlorinated compounds, as well as efforts to immobilize these NPs onto solid supports.
