Inquiring the photocatalytic activity of cuprous oxide nanoparticles synthesized by a green route on methylene blue dye

Manoranjan Behera,Gitisudha Giri

doi:10.1007/s40090-016-0075-y

Abstract

We synthesized cuprous oxide (Cu2O) nanoparticles (NPs) with an average crystallite size of 8.8 nm in presence of Arka (Calotropis gigantea) leaves extract. The photo-bleaching activity of Cu2O NPs on the aqueous methylene blue (MB) dye was studied by illumination of visible light. In the absorption spectra, a decrease in the absorption peak intensity at 665 nm of MB was observed in presence of Cu2O NPs. A red shift in its peak position as a function of irradiation time is suggesting that oxide particles are degrading the organic dye in an aqueous medium. In the vibration spectra, red shift in the C–H stretching band (2954, 2926, and 2855 cm−1) of methylene group and C–N stretching band (1343 and 1226 cm−1) of MB in presence of Cu2O NPs proposes a surface adsorption of MB over NP’s surfaces. Quenching in the emission band intensity and red shifts in the peak maxima of MB in presence of Cu2O NPs is ascribed to the charge transfer interaction between MB and oxide NPs. A linear Stern–Volmer plot reveals that decrease in the emission intensity of MB dye occurs via the dynamic quenching mechanism. Synthesis of Cu2O NPs of various architectures using a green route could be use as an approach towards the cost-effective treatment of water pollutants.

Highlights

Organic dyes are the major threats to our environments
As we have not found any report on methylene blue (MB) degradation by Cu2O NPS obtained via a green route, in this manuscript we report on visible light photodegradation of MB dye by biosurfactant-capped Cu2O NPs synthesized via a green route using leaves extract of Arka plant (i.e., Calotropis gigantea)
MB solution with Cu2O NPs was kept in the dark for nearly 3 h to eliminate possibility of other effects such as adsorption and reaction without light to affect the result

Summary

Introduction

Organic dyes are the major threats to our environments. It is not an easy task to remove them from dye-bearing waste waters owing to their stability towards oxidizing agents [1,2,3]. Sun et al [9] have reported an enhanced photocatalytic activity for Cu2O–graphene oxide (GO) nanocomposite synthesized via solvothermal route towards Rhodamine B (RhB) dye They reported that more than 65 % RhB was degraded within 80 min of visible light irradiation. Zhang et al [11] have reported 80 % MO degradation after 30 min irradiation by graphene/defected Cu2O nanocomposite synthesized via a chemical vapor deposition method They stressed on the importance of O-atoms towards the charge carrier separation. Zou et al have reported synthesis of Cu2O–rGO nanocomposites of various Cu2O crystal facets They have reported only 72, 60 and 28 % MB degradation after 120 min for octahedral, dodecahedral and cubic faceted Cu2O–rGO NPs. A few reports are available on photocatalytic activity study of Cu2O NPs synthesized by green chemical route. Another sample was analyzed without irradiating to test the adsorption ability of the oxide catalyst; other test methods were the same, as mentioned above

Results and discussion

Conclusions

Compliance with ethical standards