Optik 154 (2018) 303–314 Contents lists available at ScienceDirect Optik j ourna l ho me pa ge: www.elsevier.de/ijleo Full length article Observation of high photocatalytic activity by tuning of defects in chemically synthesized ethylene glycol capped ZnO nanorods Partha Kumbhakar, Subrata Biswas, Pathik Kumbhakar ∗ Nanoscience Laboratory, Department of Physics, National Institute of Technology Durgapur, 713209, West Bengal, India a r t i c l e i n f o Article history: Received 4 July 2017 Accepted 8 October 2017 Keywords: Optical properties Photo-catalytic Photoluminescence ZnO Defect tuning Thermal annealing Chemical synthesis Nanorod a b s t r a c t In this work, we have reported the tuning of defects by simple thermal annealing of as-synthesized ethylene glycol capped ZnO nanorods at 200–600 ◦ C temperatures. X-ray diffraction (XRD) data has confirmed the formation of Wurtzite structure of ZnO and the presence of a small amount of tensile strain is confirmed by Williamson – Hall analyses of XRD data. The lattice strain is found to increase with increasing temperature up-to 400 ◦ C and on further increase in temperature it is decreased. To study the influence of defects on photo-catalytic properties of the samples, the degradation of a test dye, namely Methylene Blue (MB) under UV–vis light irradiation has been carried out and the reaction kinetics has been determined by Langmuir-Hinshelwood model. It has been found that 400 ◦ C annealed sample exhibits the highest photo-catalytic dye degradation efficiency of ∼83%, within only 20 min. The effect of initial MB dye loading on photo-catalytic efficiency of 400 ◦ C annealed sample has also been tested and reported an optimum value of dye concentration. The successful introduction of defect states in 400 ◦ C annealed sample, as confirmed by PL mea- surement, has played an important role to achieve the high photo-catalytic activity in the samples. © 2017 Elsevier GmbH. All rights reserved. 1. Introduction The uses of hazardous dyes in textile industry have been a ubiquitous problem of human civilization and efforts are required to counter its effect on environment. The use of semiconductor photo-catalyst for the degradation of dye molecules dissolved in water is an age-old technique [1–3]. When a photo-catalyst is illuminated with the light of appropriate wave- length, electron–hole pairs diffuse out to the surface of the photocatalyst and participate in the photochemical reaction. Those free electrons and holes transform the surrounding oxygen or water molecules into OH • radicals having strong oxidizing ability. These radicals are responsible for the effective decomposition of harmful organic dyes into its less hazardous simpler forms. Among different kinds of semiconductors and its composites nanomaterial of TiO 2 , ZnO, ZnS, CdS, WO 3 etc. have been considered extensively due to their useful properties [3,4]. TiO 2 is the most commonly used effective photo-catalyst. However, recently it has been found that ZnO with a wide band gap of ∼3.2 eV is a good and an alternative semiconductor material for its high efficiency, photochemical stability, non-toxic nature and low cost preparation technique [5]. It has been ∗ Corresponding author. E-mail addresses: pathik.kumbhakar@phy.nitdgp.ac.in, nitdgpkumbhakar@yahoo.com (P. Kumbhakar). https://doi.org/10.1016/j.ijleo.2017.10.039 0030-4026/© 2017 Elsevier GmbH. All rights reserved.