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Spectroscopic comparison of UV-VIS electronic transitions of Cr ions in solution, sol and Xerogel silica matrices

Wesam A.A.Twej, Baha T.Chiad, Abbas J.H.Al-Wattar, Qussay M.Salman

Electronic transitions and the oxidation state of Cr ions have been investigated in two complexes (CrCl3.6H2OandCr(NO3)3.9H2O).These complexes were dissolved in (water and ethanol) and doped in silica using sol-gel technique. Themolar ratio ofTEOS:H2O: Ethanol is 1:10:15.3with pHvalue = 1 at 60ï‚°C. The Racah parameter (B), ligand field strength () and nephelauxetic ratio â= B/Bo has been calculated for Cr3+ ions in solution, Sol and Xerogel. The sampleswere heated with temperatures ranging from 60 to 600ï‚°C. The UV-visible spectra indicated that, during the increase of heat treatment, there is a change in the chromium species from Cr3+ to Cr6+ and Cr5+. The conversion of Cr3+ï‚®Cr6+ was promoted for the samples of concentrations > 10-3Mwhile the conversion of Cr3+ï‚®Cr5+was promoted for the samples of concentrations < 10-3M