Effect of Calcination Temperature on the Structure and Characteristics of Cuprous Oxide (Cu2O-ONPs)

This study synthesized cuprous oxide nanoparticles (Cu2O-ONPs) from the green precursors CuSO4.3H2O and Na2SO3. The materials samples were studied at prepared temperatures of 70 °C, 80 °C, 90 °C and 100 °C. The structure and characteristics of the materials were determined by methods such as Raman shift, UV-vis absorption spectrum, SEM, XRD. The results showed that, Cu2O-ONPs were crystallized the best in octahedral form at temperature of 90 °C. The absorption spectrum of the materials was in the visible light region \(\lambda \,\, \approx\) 500–600 nm with the band gap energy defined as Eg \(\approx\) 1.78–2.1eV. At calcination temperatures of 200 °C the materials retained the octahedral shape, but the absorption spectrum was shifted strongly in visible light region \(\lambda \,\, \approx\) 600–700 nm with Eg \(\approx\) 1.94eV. At the firing temperature of 300–400 °C the octahedral shapes of the materials were slightly distorted. At 500 °C the materials particles were inflated, broken and no longer retaining the original octahedral shape. Within this high temperature range of 300–500 °C the absorption spectra of the materials samples were shifted more strongly in visible light region \(\lambda \,\, \approx\) 800–900 nm, the optical band gap energy was reduced to a value Eg \(\approx\) 1.37–1.46eV which was due to the existence of two Cu2O-CuO phases. These will be desirable of material fabrication for applications in photochemical reactions in visible light region and other specific commercial applications that need further research and exploitation.