Electron paramagnetic resonance of color centers in nanoporous glasses impregnated with copper ?-diketonatewith the use of supercritical carbon dioxide

Abstract

The spectral properties of nanoporous glasses containing Cu2+ ions, which are introduced into glass pores in the form of organometallic compound of copper β-diketonate dissolved in supercritical CO2, are investigated for the first time. The analysis of the EPR and optical absorption spectra demonstrates that Cu2+ ions are located in octahedral sites with symmetry D4h. It is revealed that the intensity of the EPR spectrum decreases by one order of magnitude after annealing of the glass at a temperature of 200°C, which correlates with the temperature of decomposition of copper β-diketonate molecules (∼250°C) with the formation of CuO or metallic copper. This process is accompanied by a change in the spectrum shape and the spin-Hamiltonian parameters, even though these parameters also correspond to the octahedral environment with symmetry D4hIt is assumed that the remaining Cu2+ ions form new complexes with fragments of decomposed molecules. According to the optical data, the inference is made that high-temperature annealing leads to the formation of copper metal nanoparticles in the glass.