Preferential solvation of solvatochromic probe coumarin 153 has been studied in toluene−acetonitrile and toluene−methanol solvent mixtures. Solvatochromic shifts of absorption and fluorescence spectra of coumarin 153 in these nonideal systems are analyzed as a function of solvent polarity. There is no apparent preferential solvation of coumarin 153 in the ground state. For the excited-state molecule preferential solvation is observed in toluene−acetonitrile mixtures and it is confirmed by a theoretical model. For the excited C153 in toluene−methanol mixtures strong nonlinearity in the fluorescence solvatochromic shifts is attributed mainly to formation of a hydrogen bond between methanol and C153. IR spectra of C153 in solvent mixtures containing methanol confirm formation of a hydrogen bond between methanol and C153. The presence of a hydrogen-bonded C153 in toluene−methanol mixtures causes an unusual dependence of the C153 fluorescence lifetime on the mole fraction of methanol in solution.

The development and properties of doped nanomaterials including doped titanium dioxide, doped silicon, and doped cadmium telluride are reviewed, as well as their ultrafast dynamics. Doping nanomaterials provides a flexible way to tune to the properties of the materials while maintaining their high surface areas. The electronic, optical, photochemical, photoelectrochemical, photocatalytic and photoexcited relaxation properties can be tuned towards the desired direction by doping different elements. The materials can be engineered towards specific applications through careful selection of the dopants.

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