An investigation of the morphological, electrical and optoelectronic properties of short chain Di-ureasils doped with Er3+ ions

Abstract

Hybrid organic/inorganic xerogels containing Er3+ ions have been prepared by the solgel 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 ∞ 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 °C the most conducting sample is U(600)5Er(CF3SO3)3 (approximately 2×10−5 Scm−1), whereas the U(600)60Er(CF3SO3)3 compound displays the highest conductivity at room temperature (1×10−7 Scm−1). We have shown that concentration effects on the quenching of the 1.53 μm emission intensity (excited at 488 nm) are negligible. We have also shown that the Er3+ ions are active at room temperature.