Synthesis of ZnS/CQDs nanocomposite and its application as a photocatalyst for the degradation of an anionic dye, ARS

• Facile fabrication of ZnS/CQDs nanocomposite.
• Prepared nanocomposite exhibited higher photocatalytic activity.
• Estimation of role of active oxidation species in the photocatalytic system.
• Mechanism for photocatalytic degradation of ARS dye is illustrated.

Novel carbon quantum dots (CQDs)-modified ZnS nanocomposite was prepared via a fast and facile chemical precipitation technique and was employed for the first time as a photocatalyst for the degradation of Alizarin red S (ARS) dye under visible light irradiation. The structural, morphological and optical properties of the prepared ZnS/CQDs nanocomposite were characterized by multiple analytical techniques such as X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis, photoluminescence spectroscopy, transmission electron microscopy, field emission scanning electron microscope equipped with energy dispersive spectroscopy and UV–vis diffuse reflectance spectroscopy. Impact of affecting parameters on the photocatalytic activity of the ZnS/CQDs was studied and optimized. The results showed that the ZnS/CQDs exhibited excellent photocatalytic activity for the degradation of ARS dye i.e. 89% within 250 min, higher than that of the bare ZnS (63%). This enhancement in photocatalytic activity of ZnS/CQDs was attributed to the introduction of CQDs, which could absorb visible light efficiently, suppressing the recombination of electron–hole pairs and improving charge separation. Moreover, various scavengers have been used to study the role of reactive species in the photocatalytic degradation process.