CdO nanospheres: Facile synthesis and bandgap modification for the superior photocatalytic activity P. Senthil Kumar a , M. Selvakumar b , S. Ganesh Babu c , S. Karuthapandian a,n , Santanu Chattopadhyay b a Department of Chemistry, VHNSN College, Virudhunagar-626001, Tamil Nadu, India b Rubber Technology Centre, Indian Institute of Technology, Kharagpur-721302, India c SRM Research Institute, SRM University, Kattankulathur-603203, Chennai, India article info Article history: Received 19 January 2015 Accepted 11 March 2015 Available online 18 March 2015 Keywords: CdO Bandgap tailoring Visible light Photocatalytic property Reusable abstract The present study reports the bandgap modified CdO nanospheres for an effective photocatalyst for the degradation of organic pollutants for the first time. CdO were successfully synthesized by facile precipitation technique and subsequently characterized by various analytical tools. Interestingly, the bandgap value is modified to 2.59 eV from 2.4 eV for the commercial CdO. The photocatalytic activities of the prepared CdO nanospheres are investigated by the degradation of Rhodamine B dye solution. Since this process does not require any oxidants and also uses in the visible light, it can be developed as an economically feasible and environment-friendly method for the wastewater treatment under sunlight which still is a challenging task in contemporary research. & 2015 Elsevier B.V. All rights reserved. 1. Introduction It is well known as well as a serious problem that the waste- water containing dye waste from the textile industry creates many problems to humans and animals, and also to the ecosystem because most of the dyes are very toxic to aquatic life and also for the human body [1]. It can also inhibit the photosynthesis of submerged plants, as dyes are highly colored waste that can reduce the penetration of the solar light [2]. It has been well proven that advanced physicochemical process using semiconduc- tor photocatalysis was applied as a promising technique for the decontamination, purification and degradation of these environ- mental pollutants such as dyestuffs and polluted water [3]. Besides, the photocatalytic treatment is one of the green technol- ogies in the direction of degrading the contaminants of water that caused by the organic dyes and chemicals used in the textile industries [4]. Therefore, a series of semiconducting photosensiti- zers especially nanostructure devices have been powerfully explored in the degradation of these environmental pollutants. Cadmium oxide (CdO) is a well known n-type semiconductor with direct and indirect band gap energy of 2.2–2.5 eV and 1.36–1.98 eV, respectively [5]. In fact, the lattice defects in the crystalline structure causes this diversity in the band gap energy. In addition, CdO not only has unique optical and optoelectrical characteristics. It also has selective catalytic properties that make the compound suitable for the use in photocatalytic degradation of toxic organic compounds, dyes, pigments, environmental pollutants and so on [6]. Several efforts have been made to enhance the photocatalytic activity of CdO by playing with many factors like doping, tuning their bulk morphology, bandgap widening and so on [7]. However, there are very few reports available regarding bandgap widening of nano CdO [8]. Herein we report the photocatalytic efficiency of the bandgap modified CdO nanospheres with controlled morphology for the first time to the best of authors. Rhodamine B was selected as a model hazardous dye to evaluate the feasibility of the photocata- lytic degradation by CdO nanospheres under visible light irradia- tion. As a result, CdO nanospheres were expected to have the complementation of advantages of each component and hence provide economically feasible and environment-friendly method in the treatment of dyes. 2. Materials and methods All the chemicals were purchased from the Merck Chemicals, India and used as received. Detailed experimental procedures were given in the Supplementary section. Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/matlet Materials Letters http://dx.doi.org/10.1016/j.matlet.2015.03.047 0167-577X/& 2015 Elsevier B.V. All rights reserved. n Corresponding author. Tel.: þ91 9486287223. E-mail address: drpandianskvhnsnc2007@gmail.com (S. Karuthapandian). Materials Letters 151 (2015) 45–48