An Investigation of the Morphological, Electrical and Optoelectronic Properties of Short Chain Di-ureasils Doped with Er3+ Ions

Hybrid organic/inorganic xerogels containing Er3+ ions have been prepared by the sol-gel process. The hybrid framework of these compounds, designated as di-ureasils and represented by U(600), is composed of a siliceous backbone to which polyether chains containing 8.5 oxyethylene repeat units are linked through urea (-NHC(=O)NH-) bridges. The trivalent cations have been incorporated in the matrix as erbium triflate, Er(CF3SO3)(3). Compositions with n (where n is the molar ratio of (OCH2CH2) repeat units per Er+ ion) between infinity and 3 have been studied. The morphology of the materials was characterized by means of X-ray Diffraction and Differential Scanning Calorimetry. Complex Impedance spectroscopy was used to evaluate the levels of conductivity exhibited by the xerogels as a function of temperature. The results obtained clearly demonstrate the amorphous character of the samples analysed. At about 100 degrees C the most conducting sample is U(600)(5)Er(CF3SO3)(3) (approximately 2x10(-5) Scm(-1)), whereas the U(600)(60)Er(CF3SO3)(3) compound displays the highest conductivity at room temperature (1x10(-7) Scm(-1)). We have shown that concentration effects on the quenching of the 1.53 mu m emission intensity (excited at 488 nm) are negligible. We have also shown that the Er3+ ions are active at room temperature.