Taro Toyoda
The University of Electro-Communications, Japan
Title: Appearance of anisotropic optical absorption, ground state energy, and crystal growth of CdSe quantum dots adsorbed on the (001) and (102) surfaces of anatase-TiO2
Biography
Biography: Taro Toyoda
Abstract
The present study focuses on the effect of the substrate surfaces with different crystal orientations on optical absorption and ground state energy in a system comprising CdSe quantum dots (QDs) adsorbed on (001) and (102) surfaces of anataseTiO2 (A-TiO2 ). We applied photoacoustic (PA) spectroscopy based on the photothermal phenomenon to characterize the optical absorption, not only in the bandgap absorption but in the sub-bandgap region owing to high sensitivity. Photoelectron yield (PY) spectroscopy is useful for determining the absolute ground state energy level of QDs. Adsorption time dependence by absorbance measurements shows that (1) the adsorption rate of CdSe QDs on A-TiO2 (001) is higher than that of A-TiO2 (102) in agreement with our DFT calculations ((001) >> (101) > (102)), and (2) the diameter increasing rate of CdSe QDs on A-TiO2 (102) is higher than that of A-TiO2 (001), indicating the anisotropic crystal growth. The ground state energy levels of CdSe QDs on A-TiO2 (102) are deeper than those on A-TiO2 (001), suggesting the impossibility of the sensitization from the excited state of CdSe QDs to the conduction band of A-TiO2 (102). Deeper value of the ground state energy level of CdSe QDs on A-TiO2 (102) than those on A-TiO2 (001) is the possibility due to the difference of the permittivity of A-TiO2 (001) and A-TiO2 (102).