Effect of synthesis conditions on morphology and spectral properties of SiO2:DAST composites

SiO2:DAST composites based on SiO2 matrices with a porosity of 30-70% saturated with DAST molecules were synthesized both by evaporation from a solution and by lowering the temperature in a crystallizer. X-ray study of the composites showed the absence of DAST crystalline phase. There was only one luminescence band for all the composites with a maximum in the region of 620-640 nm (at their annealing at 100 degrees C). A hypsochromic shift (590-565 nm) of the luminescence band maxima of the composites was observed with an increase in their annealing temperature to 200 degrees C. Annealing at 200 degrees C also led to a change in the structure of the composite - "filling" of the pores of SiO2 matrices. This was probably due to a decrease in the interaction of the adsorbed DAST cations with the surface of SiO2 matrices due to exfoliation of DAST layers from the xerogel surface into the pores.