Few layered graphene by floating catalyst chemical vapour deposition and its extraordinary H 2 O 2 sensing property Manishkumar D. Yadav a , Kinshuk Dasgupta b,⇑ , Aayushi Kushwaha a , Amit P. Srivastava b , Ashwin W. Patwardhan a,⇑ , Dinesh Srivastava b , Jyeshtharaj B. Joshi a,c a Department of Chemical Engineering, Institute of Chemical Technology, Mumbai 400019, India b Materials Group, Bhabha Atomic Research Centre, Mumbai 400085, India c Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India article info Article history: Received 14 February 2017 Received in revised form 29 March 2017 Accepted 17 April 2017 Available online 19 April 2017 Keywords: Graphene Chemical vapour deposition Electron microscopy Sensor Raman spectroscopy abstract Few layered graphene (FLG) was synthesized by substrate-free floating catalyst chemical vapour deposi- tion method for the first time. A sensor prepared from the pristine FLG coated over a glassy carbon elec- trode without further modification showed high sensitivity towards sensing of H 2 O 2 (355 lA mM 1 cm 2 ) with lower detection limit of 0.27 lM and response time of 5 s. Transmission elec- tron microscopy revealed 3–5 layers of graphene sheets with edge defects, which was supported by Raman spectroscopy. X-ray photoelectron spectroscopy confirmed that the defects are due to oxygen pre- sent in the FLG in the form of C@O, that played important role in sensing. Ó 2017 Elsevier B.V. All rights reserved. 1. Introduction Graphene is a two dimensional array of sp 2 -hybridized carbon atoms, possessing exceptional physical properties and chemical tunability. These properties have attracted attention of many sci- entists and engineers across the globe in the context of a wide range of applications in energy devices, electrochemical devices, as fillers in composites, sensors [1], etc. Graphene and graphene based materials are widely accepted as a good sensors to monitor small biomolecules, such as hydrogen peroxide (H 2 O 2 ), uric acid, ascorbic acid, etc [2]. In particular, the detection of the H 2 O 2 mole- cule is of vital importance, since it plays an essential role as a sig- naling molecule in regulating various biological signaling transduction processes [3]. Several disorders in the body, such as Parkinson’s, diabetes, cardiovascular, Alzheimer’s and neurodegen- erative occurs due to bursting of H 2 O 2 which causes release of sev- eral essential signaling proteins affecting the cell proliferation [4]. Hence, an accurate and highly sensitive detection of H 2 O 2 is of practical importance in recent years. To address this issue, various methods have been developed for the rapid and sensitive determination of H 2 O 2 concentration based on different analytical principles such as chromatography, titrimetry, spectrophotometry, chemiluminescence, fluorescence and electrochemical method [5], etc. Among them, the electrochemical method has been widely used in the detection of H 2 O 2 due to its high sensitivity, rapid response, convenient operation, etc. Graphene based materials are promising electrode materials owing to their unique properties like high surface area, electrical conductivity, excellent chemical stability, etc. Generally, graphene is produced over metallic sub- strate like, nickel and copper by chemical vapour deposition (CVD). It needs to be transferred and functionalized before using it as sensor. However, we have developed a simple method for syn- thesis of few-layered graphene (FLG) by floating catalyst chemical vapour deposition (FC-CVD) without using any substrate or sup- port. The pristine FLGs while used to make a sensor exhibited enhanced sensitivity for monitoring the H 2 O 2 concentration in comparison to other enzymatic or non-enzymatic H 2 O 2 sensor reported in the literature. 2. Materials and method High purity ferrocene (Sigma Aldrich), n-hexane (Sigma Aldrich, 95–99%), hydrochloric acid (Merck, 37%), hydrogen peroxide (SD fine chemicals) and Nafion (Duralyst Energy Pvt. Ltd) were used without any further purification. Phosphate buffer solution (0.1 M) was prepared using K 2 HPO 4 and KH 2 PO 4. Argon with high http://dx.doi.org/10.1016/j.matlet.2017.04.085 0167-577X/Ó 2017 Elsevier B.V. All rights reserved. ⇑ Corresponding authors. E-mail addresses: kdg@barc.gov.in, dasguptakinshuk@yahoo.com (K. Dasgupta), aw.patwardhan@ictmumbai.edu.in (A.W. Patwardhan). Materials Letters 199 (2017) 180–183 Contents lists available at ScienceDirect Materials Letters journal homepage: www.elsevier.com/locate/mlblue