Аннотация:Natural and synthetic nanoporous materials are used in a variety of physical, chemical and biological processes. Composite systems consisting of transparent nanoporous host with specific inclusions incorporated into the pores give unique possibilities for development of devices for nonlinear optics and photonics. In a numerous technological applications, porous materials are filled with a nearcritical or supercritical molecular fluids that acts as a chemical reagent or a transport media. Chemical and physical properties playing the key role in such processes are naturally connected with molecular media phase behavior, which is substantially defined by pore size, degree of their interconnection and other topological and morphological characteristics.
Nonlinear optical spectroscopy methods and coherent anti-Stokes Raman scattering (CARS) technique in particular can be an effective tool for probing composite systems consisting of transparent nanoporous host material with a fluid inside pores. The CARS signal in this case is assumed to be determined by resonant contribution of Raman active fluid and nonresonant background from host material. The fluid confined in nanopores can be in the gaseous, adsorbed on pore walls and liquid-like states simultaneously, that are characterized by definite values of spectral width and shift therefore multi-component composite system should be taken into consideration. The interference nature of CARS spectra can serve for characterization of such nanocomposites as well as for sensing low content admixtures in a fluid. On the other hand, probing the molecular media filling internal pore volume of a transparent nanoporous material or matrix makes it possible to study molecular interaction with pore walls, peculiar properties of molecular dynamics and phase behavior at nanoconfined geometry inside pores that are significantly different from ones in a bulk volume. Available transparent materials like nanoporous glasses, polymers, aerogels, zeolites provide a wide range of pore radiuses and morphology and allow realizing different confinement conditions. Recently we applied CARS method to study fluid adsorption and condensation in pores of nanoporous glasses [1,2]. A thermodynamic description of a fluid phase behavior in nanopores yields a good accordance with the experimentally observed spectral features. In the present paper, we apply the effective medium theory to calculate the nonlinear optical response of composite samples. The results of calculations are compared to experiment.
Acknowledgments: The work is supported by Russian Foundation for Basic Research (projects 11-02-01309-a, 11-02-12112-ofi-m-2011).
References:
1. V.G.Arakcheev, A.A.Valeev, V.B.Morozov, AN.Olenin, “CARS Diagnostics of Molecular Media under Nanoporous Confinement” Las. Phys., 18, 1451-1456 (2008).
2. O.V.Andreeva, V.G.Arakcheev, V.N.Bagratashvili, et al. “CARS diagnostics of fluid adsorption and condensation in small mesopores”. J.Ram.Spectr., (2011)