The photocurrent response of dye-sensitized, porous nanocrystalline TiO2 cells was studied as a function of light intensity, in both the time domain (photocurrent transient measurements) and the frequency domain (intensity-modulated photocurrent spectroscopy). The photocurrent transients are characterized by a fast and a slow component. The rise time of the transients was in the range of milliseconds to seconds and exhibited a power law dependence on light intensity with an exponent of −0.6 to −0.8. The response to a modulated light intensity is characterized by a depressed semicircle in the complex plane. The time constant obtained from these spectra exhibits the same power law dependence on light intensity. The transient response of these cells is dominated by electron transport in the TiO2 film, and the results are shown to be consistent with a diffusion model where the diffusion coefficient for electrons in the particle network is a function of the light intensity.

The optical and electrochemical properties of nanocrystalline Ti02 electrodes in acidic aqueous solution are reported. Cyclic voltammetry, UVlvisMIR attenuance, EPR, photocurrent spectroscopy, and electrochemical impedance measurements are presented. At negative applied potentials the Ti02 films turn black, and an EPR spectrum appears which we attribute to Ti(II1) species. The results are described in terms of a model in which the reduction of Ti02 leads to band edge unpinning.

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Sulfur-containing scaffold, as aubiquitous structural motif, has been frequently used in natural products, bioactive chemicals and pharmaceuticals, particularly CÀS/NÀS bonds are indispensable in many biological importantc ompounds and pharmaceuticals. Development of mild and general methods for CÀS/NÀSb onds formation hasg reat significance in modern research. Iodine and its derivativesh ave been recognizeda si nexpensive,e nvironmentally benign and easy-handled catalysts or reagents to promote the construction of CÀS/NÀSb onds under mild reactionc onditions, with good regioselectivities andb road substrate scope.E specially based on this, severaln ew strategies, such as oxidation relay strategy,havebeen greatlydeveloped and accelerated the advancement of this field. This review focuses on recent advances in iodine and its derivatives promoted hybridized CÀS/NÀSbonds formation.The features and mechanisms of corresponding reactions are summarized and the results of some cases are compared with those of previous reports. In addition, the future of this domain is discussed.

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