Contents lists available at ScienceDirect Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys Engineering of ZnO/rGO nanocomposite photocatalyst towards rapid degradation of toxic dyes Sujoy Kumar Mandal a , Kajari Dutta b , Saptarshi Pal c,a , Sumit Mandal a , Avigyan Naskar d , Pabitra Kumar Pal e , T.S. Bhattacharya f , Achintya Singha f , Rezaul Saikh g , Sukanta De g , Debnarayan Jana a,* a Department of Physics, University of Calcutta, 92 A.P.C. Road, Kolkata, 700009, India b Department of Physics, Amity University, Major Arterial Road, AA II, Newtown, Rajarhat, Kolkata, 700135, India c Department of Physics, School of Natural Sciences, Shiv Nadar University, NH-91, Thesil Dadri, Gautam Buddha Nagar, Uttar Pradesh, 201314, India d Department of Chemistry, University of Calcutta, 92 A.P.C. Road, Kolkata, 700009, India e Department of Physics, Jadavpur University, 188 Raja S.C. Mallick Road, Kolkata, 700032, India f Department of Physics, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata, 700009, India g Department of Physics, Presidency University, 86/1 College Street Road, Kolkata, 7000073, India HIGHLIGHTS • ZnO QD is synthesized by soft che- mical route followed by ageing pro- cess and ZnO/rGO composites by sol- vothermal method. • XRD, RAMAN and TEM measurements confirm the ZnO/rGO composite for- mation. • Electron transfer mechanism is ex- plained from the photoluminescence lifetime measurement. • Degradation efficiency is optimized by proper composite formation. GRAPHICAL ABSTRACT ARTICLE INFO Keywords: ZnO QD Reduced graphene oxide Composite Photocatalyst Toxic dyes ABSTRACT ZnO quantum dot (QD) is prepared in a soft chemical route by ageing process and successfully embedded on reduced graphene oxide (rGO) surface using solvothermal method as confirmed by XRD, TEM and Raman stu- dies. Due to charge transfer from the lowest unoccupied molecular orbital of the rGO layer to the conduction band of ZnO, the luminescence of rGO is also found to be quenched in ZnO/rGO composites. A brief systematic study of photocatalytic behavior towards degradation of various toxic medical and textile dyes, like Safranin O, Methylene blue and Rhodamine 6G by ZnO QD and ZnO/rGO composites are showcased in this work. As a result of high surface to volume ratio, ZnO QD showed good photocatalytic activity towards degradation of different dyes under ultraviolet (UV) irradiation. A composite with ZnO and rGO in 3:1 wt ratio degraded almost 100% of dyes under UV irradiation within 15, 25 and 30 min, showing good efficacy in dye degradation. Photoluminescence lifetime measurement revealed the charge transfer process from rGO to ZnO resulting a Prompt recombination of the UV light induced electron-hole pair in ZnO/rGO composite. https://doi.org/10.1016/j.matchemphys.2018.11.002 Received 18 June 2018; Received in revised form 22 October 2018; Accepted 1 November 2018 * Corresponding author. E-mail address: djphy@caluniv.ac.in (D. Jana). Materials Chemistry and Physics 223 (2019) 456–465 0254-0584/ © 2018 Elsevier B.V. All rights reserved. T