305 Functional Nanomaterials Based On Janus Nanoparticles

Thursday, November 5, 2009: 4:00 PM
Ballroom C+D (Camino Real Hotel)
Sulolit Pradhan , Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA
Li-Ping Xu , Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA
Shaowei Chen , Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA
Functional nanomaterials based on Janus nanoparticles were prepared by using gold nanoparticles as the illustrating example, where ligand exchange reactions of a Langmuir monolayer of hydrophobic alkanethiolate-passivated gold nanoparticles occurred at relatively high surface pressures with hydrophilic thiol derivatives injected into the water subphase. The unique amphiphilic characters were confirmed by a variety of experimental measurements, including contact angle measurements, adhesion force microscopy, FTIR, UV-visible, and NMR spectroscopies. Interestingly, the resulting Janus nanoparticles exhibited vastly differently electronic conductivity properties when they were deposited onto an IDA electrode surface in the heads-down or tails-down configuration. In addition, the Janus nanoparticles might be used for the preparation of more complicated functional materials. For instance, Au-TiO2 snowman-like heterodimer nanoparticles have been prepared by a surface sol gel process based on gold Janus nanoparticles. TEM measurements showed that the resulting TiO2 nanoparticles exhibited well-defined lattice fringes that were consistent with the (101) diffraction planes of anatase TiO2. The heterodimer nanoparticles displayed apparent photoluminescence that was ascribed to electronic transitions involving trap states of the TiO2 particles, and the photocatalytic activity was manifested by the oxidative conversion of methanol into formaldehyde. The enhanced photocatalytic performance, as compared to that of the TiO2 nanoparticles alone, was ascribed to the effective charge separation of photogenerated electrons and holes at the Au-TiO2 interface that was facilitated by the close proximity of the gold nanoparticles. The results suggest that the snowman-like heterodimers might be exploited as a homogeneous photocatalytic system for the preparation of functional molecules and materials.