Structural optical and magnetic characterizations of pure and cobalt-doped CdSe nanoparticles to investigate photocatalytic degradation of methyl blue under visible light

The samples of cadmium selenide (CdSe) nanoparticles (NPs) of pure and doped with cobalt (Co) were developed in a chemical reduction route. The synthesized nanoparticles were characterized employing transmission electron microscopy (TEM), selected area electron diffraction pattern (SAED), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), energy dispersive x-ray analysis (EDX), x-ray diffractometry (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, vibrating sample magnetometer (VSM) tool, UV–Vis spectroscopy, photoluminescence (PL) spectroscopy and photocatalytic activity measurements. The average crystallite size is 5.8–8 nm as determined by TEM and XRD measurements. With increased cobalt percentage in CdSe as a doping element, strong photoluminescence quenching and improved quantum confinement are observed. The direct bandgap of CdSe nanoparticle samples of pure and doped with Co (5% & 7%), measured by UV–vis spectrometer are 2.02 eV, 2.13 eV and 2.23 eV, respectively. Photocatalytic activities of CdSe were studied by irradiating the solution of methyl blue (MB) upon its exposure to visible light. The pure CdSe, 5% Co-doped CdSe and 7% Co-doped CdSe show removal efficiency for Methyl Blue solution at pH 7 as 75%, 85% and 97% in 60 min, respectively. In particular, the 7% Co-doped CdSe photocatalyst exhibits about 97% degradation of MB dye at a rate constant (0.0076 min −1 ) which is clearly more efficient than 5% Co-doped CdSe (0.0067 min −1 ) and pure CdSe (0.0037 min −1 ).