Visible light driven photocatalytic degradation of Rhodamine B and Direct Red using cobalt oxide nanoparticles

Cobalt oxide (Co3O4) nanoparticles were prepared by simple, facile and cost effective sol–gel route. Triethanol amine (TEA) was used as surfactant to reduce the size of the particles. The XRD patterns reveal that the crystallite size of the sample prepared without surfactant yields 69 nm and with different surfactant concentrations (5 ml, 10 ml, and 15 ml), the estimated crystallite sizes were reduced to 64 nm, 52 nm, and 32 nm respectively. The morphological and elemental composition of the samples was investigated by SEM and EDS. The optical studies revealed the possible electronic transitions which are responsible for an occurrence of two energy band gap in cobalt oxide. The photoluminescence probe for the presence of defects and the results obtained specified that the defects get reduced with the addition of surfactant TEA. Photocatalytic degradation of dyes (Rhodamine B and Direct Red 80) was investigated under visible light using cobalt oxide nanoparticles as catalyst. The effect of catalyst amount and pH of the dye solution was analyzed with the help of UV–visible absorption spectra.