Zhenbin Ge, Former PhD student in Materials Science and Engineering from 08/02 to 5/2006
09/2000 to 07/2002 Master Degree in MSE, Tsinghua University, P.R. China
09/1996 to 07/2000 Bachelor Degree in MSE, Tsinghua University, P.R.China
personal web site
1. AuPd Metal Nanoparticles as Probes of Nanoscale Thermal Transport in Aqueous Solution
Water and alcohol soluble AuPd nanoparticles have been investigated to determine the effect of the organic stabilizing group on the thermal conductance G of the particle/fluid interface. The thermal decays of tiopronin stabilized 3-5 nm diameter AuPd alloy nanoparticles, thioalkylated-ethylene-glycol stabilized 3-5 nm diameter AuPd nanoparticles, and cetyltrimethylammonium bromide stabilized 22 nm diameter Au-core/AuPd-shell nanoparticles give thermal conductances G ~ 100 - 300 MW m-2 K-1 for the particle/water interfaces, approximately an order of magnitude larger than the conductance of the interfaces between alkanethiol-terminated AuPd nanoparticles and toluene. The similar values of G for particles ranging in size from 3-24 nm with widely varying surface chemistry indicate that the thermal coupling between AuPd nanoparticles and water is strong regardless of the self-assembled stabilizing group.
2. Thermal transport in Au-core polymer-shell nanoparticles
Thermal transport in aqueous suspensions of Au-core polymer-shell nanoparticles is investigated by time resolved measurements of optical absorption. The addition of an organic co-solvent to the suspension causes the polystyrene component of the polymer shell to swell and this change in the microstructure of the shell increases the effective thermal conductivity of the shell by a factor of approximately 2. The corresponding time-scale for the cooling of the nanoparticle decreases from 200 ps to approximately 100 ps. The threshold concentration of co-solvent that creates the changes in thermal conductivity, 5 vol% tetrahydrofuran in water or 40 vol% N,N-dimethylformamide in water, are identical to the threshold concentrations for producing small shifts in the frequency of the plasmon resonance. Because the maximum penetration of solvent into the polymer-shell is less than 20 vol%, the increase in the effective thermal conductivity of the shell cannot be easily explained by contributions to heat transport by the solvent or enhanced alignment of the polystyrene backbone along the radial direction.
This work is collaborated with Andrew Taton and Youngjong Kang at University of Minnesota.
Professor Paul Braun • Phone: +1.217.244.7293 • Fax: +1.217.333.2736 • Email: pbraun@illinois.edu
Department of Materials Science and Engineering • University of Illinois at Urbana-Champaign