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Au-Ag and Au-Cu nanoparticles of various compositions were synthesized in chloroform and their physical properties were characterized by employing various techniques such as UV-Visible spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The synthesized alloy nanoparticles of diameter ca. 3 nm exhibit characteristic photoelectron spectra and linear optical properties. The nonlinear optical properties of the alloy nanoparticles were also investigated in the surface plasmon absorption region by the degenerate four wave mixing technique.

A colloidal suspension of exfoliated, layered cobalt oxide nanosheets has been synthesized through the intercalation of quaternary tetramethylammonium ions into protonated lithium cobalt oxide. According to atomic force microscopy, exfoliated nanosheets of layered cobalt oxide show a plateau-like height profile with nanometer-level height, underscoring the formation of unilamellar 2D nanosheets. The exfoliation of layered cobalt oxide was cross-confirmed by X-ray diffraction, UV/Vis spectroscopy, and transmission electron microscopy. The maintenance of the hexagonal in-plane structure of the cobalt oxide lattice after the exfoliation process was evidenced by selected-area electron diffraction and Co K-edge X-ray absorption near-edge structure analysis. The zeta-potential measurements clearly demonstrated the negative surface charge of cobalt oxide nanosheets. Adopting the nanosheets of layered cobalt oxide as a precursor, we were able to prepare the monodisperse CoO nanocrystals with a particle size of approximately 10 nm as well as the heterolayered film composed of cobalt oxide monolayer and polycation.

The internal rotation of a photoexcited hemicyanine dye, trans-4-[4-(dimethylamino)-styryl]-1-methylpyridinium iodide (DASPI), was investigated in water-containing reverse micelles. The rate constants for the twisting motion were obtained from the measured fluorescence lifetimes in various sizes of water nanoclusters (ca. 0.6−5.6 nm in radius) prepared from sodium bis(2-ethylhexyl) sulfosuccinate (AOT)−alkane−water solutions by changing the molar ratio of water/AOT. It was observed that the fluorescence lifetime of DASPI in the water pool formed by the reverse micelle markedly increases as the nanocluster size decreases, implying that the excited-state twisting motion is significantly influenced by the microstructure of the reverse micelle. An endeavor was made to relate the rate process for internal rotation to water pool characteristics such as polarity and viscosity.

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