Semiconductor nanoparticles are building blocks for nano-scale structures and devices, such as a new type solar cells based on dye sensitized nanocrystalline TiO2 thin films. The performance of these devices depends critically on the charge transfer properties in and out of the nanoparticles/thin films and carrier relaxation dynamics within the particles. In this paper, we will present our recent study of electron transfer(ET) dynamics between semiconductor nanoparticles and molecular adsorbates in the solid-liquid interface using femtosecond infrared spectroscopy. Both the IR absorption of electrons in the semiconductor, and the vibrational spectra of the adsorbates are directly measured in the mid infrared region, allowing unambiguous assignment of the ET process. Ultrafast forward ET from adsorbates to nanoparticles were studied in RuL2(SCN)2 (L=2,2¹-bipyridyl-4,4¹-dicarboxylate) sensitized nanocrystalline thin films of TiO2 and ZnO. Backward electron transfer from nanoparticles to adsorbates were investigated in Fe(CN)64-/TiO2. The dependence of these ET rates on molecular adsorbate, nanoparticles, and their interaction will be discussed.
Tianquan Tim Lian Phone: (404)-727-6649
email: tlian@emory.edu
http://www.emory.edu/CHEMISTRY/faculty/lian/
Department of Chemistry:
Fax:(404)-727-6586
Atlanta, GA 30322
http://www.chem.emory.edu