Nanocomposites and Nanomaterials

Synthesis, optical and nonlinear optical properties of semiconductor hetero-nanoparticles in ionic liquid crystalline systems
Mirnaya T.1, Yaremchuk G.1, Klimusheva G.2
1 V.I.Vernadskii Institute of General and Inorganic Chemistry of the NAS of Ukraine, Prospekt Palladina, 32-34, Kyev-03142, Ukraine. 
E-mail:yaremchuk@ionc.kiev.ua 
2 Institute of Physics of the NAS of Ukraine, Prospect Nauki, 46, Kyiv-03039, Ukraine.

The paper presents on the synthesis, optical and nonlinear optical properties of composites with core-shell type metal chalcogenide hetero-nanoparticles (CdS – CdSe, Ag – CdSe, Ag – CdS, Au – CdS, Au – CdSe), which have been object of great attention in the recent few decades. By changing the structure of complex semiconductor nanoparticles, one can change their electronic structure and control thereby their optical properties. Nanocomposites with hetero-nanoparticles have promise in creating novel nonlinear optical materials, light-emitting diodes on the new generation, highly efficient luminescent marks, etc.
The synthesis of hetero-nanoparticles has been carried out cadmium caprylate based liquid crystalline systems using different methods, viz successive (fusing together of composites contaning mono-nanoparticles) and parallel (coprecipitation/coreduction) synthesis.
The effect of the composition of Ag(Au) – СdSe(СdS) hetero-nanoparticles and plasmon-exciton interaction on the optical and fluorescent properties of the synthesized glassy mesomorphic nanocomposites has been studied. It has been shown that the nanocomposites with hetero-nanoparticles are characterized by a more intense exciton fluorescence band than the composites with individual nanoparticles. A sharper quenching of luminescence has been established for mesomorphic glassy composites with Ag – СdSe(СdS) hetero-nanoparticles, whereas a gradual quenching of luminescence is observed for composites with Au – СdSe(СdS) hetero-nanoparticles. The different nature of the luminescence quenching process is due to the stronger surface resonance electromagnetic field of silver nanoparticles compared with gold nanoparticles, i.e. silver nanoparticles are stronger semiconductor shell exciton traps.
It has been found by the Z-scanning method that the optical hetero-nanocomposites have a fast nonlinear optical response and relatively high values of third-order nonlinear optical susceptibility.