Characterization of nanocrystalline CdO prepared by solution combustion method for photocatalytic and fluorescence sensing applications

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Here we report the characterization of pure CdO nanoparticles prepared by solution combustion method and annealed in air at 285, 385 and 485 °C. XRD study reveals their high crystallinity, face centred cubic (FCC) structure, and crystallite size as 43, 44 and 45 nm respectively. Cd and CdO2 impurity phases are detected in 285 and 485 °C annealed samples, while no impurity phase appeared in 385 °C annealed sample. Change in surface morphology of CdO in response of annealing treatment and typical grain-size ranging from 30 to 120 nm have been obtained from FESEM and TEM images. XPS, FTIR and Raman spectroscopy techniques provide strong evidence of the chemistry of these materials. Optical studies indicate a blue-shift in energy bandgap by ∼19, 26 and 27% for 285, 385 and 485 °C annealed samples when compared with the bulk CdO (2.2 eV). These materials when studied for the photocatalytic degradation of methyl orange (MO), methylene blue (MB) and picric acid (PA) under UV illumination and for fluorescence quenching of PA indicate that 385 °C annealed sample is the most effective towards these applications, despite increase in the optical bandgap. Degradation of MO, MB and PA, with rate constant: 31.6 × 10−3, 24.54 × 10−3 and 22.68 × 10−3 min−1 respectively, and detection of PA with limit of detection (LOD): 1.85, 1.44, and 1.64 μM for 285, 385 and 485 °C annealed samples were obtained. This work demonstrates that increase in electron degeneracy and improved crystallinity in 385 °C annealed oxygen-deficient nanostructured CdO both are contributing factors for the observed enhanced performances. To be more specific, this is possible contribution of charge carrier separation in consequence of UV light excitation that presumably occurred due to Burstein – Moss effect.