Amplified spontaneous emission (ASE) is demonstrated in volume-distributed feedback (DFB) structures, formed by colloidal CdSe/ZnS nanocrystals and ZrO2 nanoparticles (NPs) in a polymer matrix. Periodic redistribution of the NPs in an organic matrix was carried out by holographic photopolymerization in a specially developed light-sensitive nanocomposite. The composite consists of two acrylate monomers and two types of inorganic NPs. The NPs provide for the formation of two co-phased gratings-a refractive index grating and an optical gain (losses) grating. The core-shell CdSe/ZnS nanocrystals are used as a gain medium, while ZrO2 NPs create the refractive index grating and enhance the distributed feedback. The period of the volume structure provides the feedback for lasing at the wavelength lambda(las) of about 575 nm in the second diffraction order. In contrast to known laser systems based on volume DFB cavities, in which the different components of the formulation provide optical gain and feedback, in our case the inorganic NPs serve as an emitting material and can provide simultaneously for feedback. By pumping of DFB structures by a titanium-sapphire laser (lambda(pump) = 400 nm, pulse duration of 120 fs) normal to the sample plane, the appearance of a sharp stimulated emission along the grating-vector direction is observed. Output intensity of ASE as a function of the pump energy shows a threshold behavior and full width at half-maximum (FWHM) of the ASE spectral band decreases from 33 to 12 nm.

A new approach to producing volume periodic polymer-metal nanoparticle structures is presented. Periodic distribution of Ag nanoparticles in a polymer film can be obtained by applying the holographic patterning in the UV or visible spectral range to the composite material comprising photocurable monomers, photoinitiators and a solution of silver nitrate in acetonitrile. Photopolymerization of the composite in the interference pattern provides formation of a highly efficient volume grating composed of periodic polymer regions and Ag precursor-containing regions. Subsequent homogeneous UV irradiation and/or thermo-treatment of the grating causes reduction of silver ions to Ag nanoparticles in the areas of the film containing the metal precursor. Spectroscopic measurements confirm the formation of the nanoparticles in the gratings. Transmission electron microscopy showed a regular spatial distribution of well-defined Ag nanoparticles in a polymer film with a periodicity governed by the geometry of holographic structuring. The average diameter of nanoparticles can be controlled by the wavelength and intensity of holographic exposure as well as the composite formulation. A possible mechanism of silver nanoparticle formation by free radicals as reducing agents is presented.

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The results of the study on the properties of carbon nanotubes-polymer nanocomposites have shown that the use of nanotubes (CNT) to fill the polymer matrices of different species significantly alter their physical properties compared to the original polymers. However, the influence of CNT on the properties of nanocomposites obtained at the molecular level has not been completely ascertained yet. Therefore, the purpose of this work was to examine the interaction of CNT with fragments of polymers with the same nature, but the different structure, for example, polyethylene and polypropylene using quantum chemistry.By method of density functional theory with the exchange-correlation functional B3LYP, the basis set 6-31G(d,p) and the Grimme dispersion correction, the energy values have been calculated of interaction between carbon nanotube fragments and oligomers of polyethylene and polypropylene, the most probable structures of their intermolecular complexes being optimized.A graphene-like plane of 40 carbon atoms and 16 atoms of hydrogen was chosen as a model for the outer surface of the multi-walled nanotubes (MWNT). In addition to the above described, two larger models were used, with the general formula C 54 H 18 and C 96 H 24 in order to take into account the dimensional effect of the surface of the nanotube fragment model on the interaction energy.It has been found that the interaction energy of a carbon nanotube fragment with an oligomer of polypropylene is greater, compared with polyethylene, which is consistent with the experimental data on melting temperatures of pure polymers and nanotube-polymer composites.The polymer with an outer surface of a carbon nanotube forms an intermolecular complex do not bound covalently and retained by intermolecular dispersion forces. Oligomers of polymeric matters and nanotube surfaces in nanocomposites formed are located closer to each other than separate polymeric links between them.

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