Casein mediated green synthesis and decoration of reduced graphene oxide Sireesh Babu Maddinedi a , Badal Kumar Mandal a,⇑ , Raviraj Vankayala b , Poliraju Kalluru b , Sai Kumar Tammina a , H.A. Kiran Kumar a a Trace Elements Speciation Research Laboratory, Environmental and Analytical Chemistry Division, School of Advanced Sciences, VIT University, Vellore 632014, India b Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan, ROC highlights  A green eco-friendly method for casein mediated reduced graphene oxide synthesis.  Decoration of casein molecules on the surface of graphene sheets stabilizes it.  Amino groups of aspartic, glutamic acid residues in casein cause reduction of GO. graphical abstract Incorporated casein molecules via amino linkage onto the surface of graphene cause the stability of the graphene via their surface carboxylic acid groups [25,26]. Aspartic acid and glutamic acid residue of casein molecule are responsible for the graphene oxide reduction. article info Article history: Received 3 November 2013 Received in revised form 9 January 2014 Accepted 22 January 2014 Available online 6 February 2014 Keywords: Green synthesised graphene Graphene oxide Casein Aspartic acid Glutamic acid abstract This research is mainly focusing on one-step biosynthesis of graphene from graphene oxide and its stabilization using naturally occurring milk protein, casein. The synthesis of casein reduced graphene oxide (CRGO) was completed within 7 h under reflux at 90 °C with the formation of few layered fine graphene nanosheets. UV–Vis, XRD, XPS analysis data revealed the reduction process of the graphene oxide. Results of FT-IR, HPLC and TEM analysis have shown that the ensuing material consists of graphene decorated with casein molecules. Aspartic acid and glutamic acid residue present in casein molecules are responsible for the reduction of graphene oxide. Ó 2014 Elsevier B.V. All rights reserved. Introduction Graphene, a two-dimensional nanomaterial of single atom thickness, have received much attention in recent years because of its outstanding physical and chemical properties [1]. Due to its exceptional electrical, mechanical, and thermal properties, http://dx.doi.org/10.1016/j.saa.2014.01.114 1386-1425/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author. Tel.: +91 9442344774; fax: +91 4162243092. E-mail addresses: badalmandal@vit.ac.in, mbadal1963@gmaill.com (B.K. Mandal). Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 126 (2014) 227–231 Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa