Structural and optical investigation of combustion derived La doped copper oxide nanocrystallites

The effect of La dopant concentration (4% and6%) and annealing (400, 600 and 800 degrees C) behavior of CuO derived by solution combustion method (SCS) are investigated. Structural and optical properties were studied by XRD, SEM, diffuse reflectance spectra (DRS) and photoluminescence (PL) measurements for the prepared samples. The crystallinity of the samples increases with temperature. Incorporation of La in CuO lattice reduces the crystallinity due to the variation of ionic radii and also leads to higher angle peak shift. From SEM micrograph, it is clear that annealed samples increases the nucleation rate and agglomerates the particles. DRS study revealed the narrowing of the bandgap in doped CuO compared to undoped CuO, which is due the influence of La3+ impurity dopant ions on the electronic states of the crystallite. The band broadening in higher concentration of impurity is due to the partial curing of copper vacancies. The luminescence spectra show that there is no change in peak position but slight variation in the peak intensity related to the defect change in the CuO due to La doping. La induces the lattice distortion, increases the defect concentration in CuO and it acts as a quencher. Bandgap shift and quenching of PL intensity may provide excellent degradation efficiency of dye by the design of rare earth doped CuO-based photocatalyst.