Spectroscopy and optical properties of HITC-doped silica sol-gel glasses

The photophysical behavior of the organic dye HITC (1,1',3,3,3',3'-hexameth ylindotrycarbocyanine iodide) incorporated into silica gel glasses prepared from different starting compositions was studied in detail by fluorescence spectroscopy and lifetime measurements. The structural and morphologic cha racterization of the hosting matrix by FTIR, Si-29-NMR, UV-VIS-NIR spectros copies, SEM and TEM techniques and measurements of the BET specific surface area, revealed the important in fluence on the optical properties of the w ater content in the starting solution of the different sol-gel compositions . An increase in the transmission at the UV cut-off as well at the NIR wave lengths was achieved in samples prepared from the specific composition of t he gel produced from low water to monomer molar ratio (r(w/m) = 1*), and av oiding during the reaction water adsorption from the air. This specific met hod of preparation is adequate to achieve the chemical stabilization of the HITC dye in gel glasses. The poor mechanical properties of these gel glass es can be improved when drying is performed under controlled pressure and h umidity conditions. (C) 1999 Elsevier Science B.V. All rights reserved.