Time-resolved near-field spectroscopic study on photophysical processes at solid/liquid interface

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1) Spectroscopic Properties of Semiconductor Nanostructures by Scanning Probe Microspectroscopy Non-linear optical properties such as two-photon absorption cross section and nonlinear refractive index of CdTe QDs were found to strongly depend on a size of QDs. The figure of merit was also found to increase with decreasing the size. The size dependence of nonlinear optical properties was analyzed by the theory derived by Sheik Bahae. CdTe nanowires synthesized from QDs was analyzed by time-resolved SPM, suggesting the heterogeneity of nanowires. In addition, the exciton annihilation of nanowires increased as compared with QDs because of the energy diffusion in nanowires. In previous experiments, blinking behavior was observed for single QD embedded by PVA and trehalose. We have found that the silica coating of a single CdTe QD dramatically suppress the blinking, suggesting that the environmental condition plays an important role for luminescence properties of single QD. Furthermore, CdS … More e nanorods and QDs were synthesized at low temperature and their physicochemical properties have been examined by SPM.2) Synthesis and Characterization of Ag Nanorods Silver nanorods were prepared by a seed-mediated growth approach with chemical reduction of Ag^+ in a detergent aqueous solution. Longitudinal and transverse modes of plasmon absorption have been clearly observed in this synthetic approach. Transient absorption dynamics indicates that the coherent acoustic vibration with oscillation period of 20 to 40 ps was originated from the heat release of nanorods that induces a periodic shift of plasmon absorption bands. By the analysis of acoustic vibration, the size of synthetic nanorods and the aspect ratio have been estimated.3) Highly-sensitive, Broadband Transient Absorption Microspectroscopy Detection wavelength region was expanded up to 1.6 μm by using InGaAs photodiode as a detector, which enables us to examine the dynamics of exciton delocalization or weak intermolecular interaction dynamics in small domains at interface with high sensitivity of △OD = 10^<-7> 〜 10^<-8>..Global-pump and local-probe geometry was also successful for transient absorption SNOM experiments. Less