Synthesis and characterization of mixed metal oxide nanoparticles derived from Co–Cr layered double hydroxides and their thin films

In this paper, cobalt as divalent and chromium as trivalent ion layered double hydroxide was prepared in the absence and in the presence acetamide as organic molecule template by using co-precipitation method in aqueous solution at the room temperature. The resulting cobalt–chromium (Co–Cr) LDH and cobalt–chromium/acetamide (Co–Cr)/A LDH were dried at 358 K. To produce mixed metal oxides in nanoscale with appropriate physical properties form both cobalt divalent and chromium trivalent LDHs, the calcination process was applied for the prepared (Co–Cr)/A LDH samples at 873 K for 3 h. The calcined and un-calcined (Co–Cr)/A LDH samples were characterized using various techniques including FTIR, TGA, XRD and SEM techniques. Before the calcination, the XRD pattern of the (Co–Cr)/Acetamide LDH displays polycrystalline of LDH, while after calcination process, the crystallinity state changes to be semi-crystalline material. Fabrication of thin film from (Co–Cr)/A LDH was conducted by thermal evaporation method (Edwards type E 306 A, England) with thickness 200 ± 5 nm. The optical characteristics of (Co–Cr)/A LDH film, within the wavelength range of 200 nm to 1000 nm spectra for both calcined and un-calcined samples, were studied. The average optical energy gaps for (Co–Cr)/A LDH film before and after calcination were 2.79 eV and 2.81 eV, respectively. The optical absorption edges revealed the existence of blue shift with increasing of the calcination temperature. The resulting results could be useful for the fabrication of micro-nanodevices.