Composite materials based on different nanoporous matrices with incorporated dye molecules are increasingly used to create tunable lasers, light guides and active elements for nonlinear optics and photonics. The unique properties of polymethine dyes converting of light energy in the visible and near infrared region of the spectrum allows their widely to use as sensitizers, active laser and nonlinear optical media, new tools for recording information. One of the most promising materials for the creation of composite optical materials based polymethine dyes are synthesized by the sol-gel SiO₂ matrices has a low light scattering, good thermal conductivity and low temperature coefficient of refractive index. The sol-gel technology allows incorporation of organic and inorganic additives during the process of the formation of SiO₂ network at room temperature. Introduction to the SiO₂ matrices polymethine dyes with different geometrical shape and concentration allows to obtain composites with desired properties. For regulation of these properties must be controlled pore size distribution of the dye molecules and their aggregation in the matrix.
     The aim of the present work was the synthesis of transparent monolithic SiO₂ matrices with DCCA (formamide, FA) and polymethine dyes (SL2651, SL3021 and SL3104) to create of composite nonlinear optical media. SiO₂ based sols were prepared by hydrolysis and polycondensation of tetraethoxysilane in ethanol with citric acid used as a catalyst. The optimal physical and chemical conditions for obtaining nanoporous SiO₂ matrices with FA were installed. TEM method confirmed the formation of pores in the matrix size as 4-10 nm. By hydrostatic weighing method was determined that porosity of the matriсes – 52%.
     Organic dyes SL2651, SL3021 and SL3104 were injected into SiO₂ matriсes directly in the sol at the synthesis stage. Based on a comparative analysis of the spectral-luminescent properties of dyes in various solvents and in the matrix, were found the effect of the microenvironment in the matrix pores on the dye molecules. Shown to increase the length of the polymethine chain in the dye SL2651 compared with dyes SL3021 and SL3104 leads to bathochromic shift of the absorption maximum for SL2651. The observed hypsochromic shift of the absorption maxima of dyes SL3021 and SL3104 in an aqueous solution with respect to ethanol and FA caused dimers of dye molecules. The polymethine dyes molecules with branched structure (SL2651, SL3021 and SL3104) form dimers in the pores of the matrices and in aqueous solutions due to their conformational features. Dimerization of the dyes in the gel due to the presence of water leads to a reduction of their luminescence in SiO₂ matrices. It was found that the dye does not form dimers SL2651 in the solvent (water) and in the pores of the matrices is in the monomeric state, resulting composite SiO₂: SL2651 has effective luminescence. Given the geometric and conformational parameters of molecules contained phosphors, and statistically derived pore sizes, was proposed the model of the location of the dye molecules in the pores of the matrix. Production of composite structures is of great interest for optoelectronics and photonics.

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