Gap-mode of metal-inorganic semiconductor system

Dye sensitized Ti02 solar cell is one of the excitonic solar cells. Interfacial electron transfer (ET) plays a central role in dye-sensitized solar cells, photocatalysis, environmental chemistry, surface chemistry, and molecular electronics [56]. The forward electron transfer (FET) kinetics in various dye-Ti02 systems has typical halftimes ranging from femtoseconds to several hundred picoseconds. When the adsorbed molecule is strongly bound close to the Ti02 

We have used confocal and tip-enhanced high-resolution near-field luminescence and Raman imaging spectroscopy to anal) e the interfacial charge-transfer energetics down to the single site and single-molecule level, well beyond the spatial resolution of the optical diffraction limit [60]. 

Panels Al and Bl in Fig. 9.15 show confocal images of the Nb-doped rutile Ti02 (110) surface under the conditions of without (A) and with alizarin (B), respectively. Most of the hot spots in the confocal image (without the tip) in Fig. 9.15A1 show as donut-shape features, and only a small number of them show as circular or ellipsoidal-shaped spots. Such different diffraction limited fluorescence excitation patterns can only be observed when single quantum systems are raster scanned through the field distribution of a tightly focused radially polarized laser beam. Since the excitation rate is proportional to the square of the projection of the transition dipole moment onto the electric field. 

In the above sections, we have systematically explained the principle, the concept of design, the instrumentation and the applications of PM-assisted gap-mode optical microscopy. 

Drechsler, A., Lieb, M. A., Debus, C., Meixner, A. J., and Tarrach, G. [2001] Confocal microscopy with a high numerical aperture parabolic mirror, Opt Express, 9, 637-644. 

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