Ultrathin graphitic carbon nitride nanosheets: a low-cost, green, and highly efficient electrocatalyst toward the reduction of hydrogen peroxide and its glucose biosensing application† Jingqi Tian, ab Qian Liu, a Chenjiao Ge, a Zhicai Xing, a Abdullah M. Asiri, cd Abdulrahman O. Al-Youbi cd and Xuping Sun * acd In this communication, we demonstrate for the first time that ultrathin graphitic carbon nitride (g-C 3 N 4 ) nanosheets can serve as a low-cost, green, and highly efficient electrocatalyst toward the reduction of hydrogen peroxide. We further demonstrate its appli- cation for electrochemical glucose biosensing in both buffer solution and human serum medium with a detection limit of 11 mM and 45 mM, respectively. Binary carbon nitrides are a new class of N-doped carbon-based materials with a 3D or 2D structure with great potential appli- cations in high-performance tribological coating, catalysis, and the production of metal nitrides. 1 As an analogue of graphite, graphitic carbon nitride (g-C 3 N 4 ) polymer possesses a stacked two-dimensional structure and is the most stable allotrope of carbon nitride under ambient conditions. 2 Compared with inorganic semiconductor counterparts, g-C 3 N 4 as an organic semiconductor consists of carbon and nitrogen, which are among the most abundant elements in our planet, and there- fore, is environmentally friendly and can be produced on a large scale with low cost by bulk condensation of N-rich precursors including cyanamide, dicyandiamide, melamine, and urea. An additional advantage is that its electronic band-gap structures can be easily manipulated by chemical functionalization or doping. Indeed, g-C 3 N 4 has attracted a great deal of attention due to its novel structures and unique properties and found wide applications in photovoltaic and photocatalytic elds in the past years. 3 The accurate determination of hydrogen peroxide (H 2 O 2 ) is of great practical importance in many elds such as food, pharmaceutical, clinical, industrial and environment protec- tion. 4 The electrochemical technique is a promising tool for the construction of simple, low-cost H 2 O 2 sensors owing to its high sensitivity, good selectivity and ease of operation. 5 Although natural peroxidase exhibits intrinsic sensitivity and selectivity for H 2 O 2 , 6 it suffers from instability and high cost. The rst issue has been successfully solved by us and others with the use of Ag or Au nanostructures as articial enzyme mimetics, 7 however, the high cost issue remains. Xu et al. reported that N-doped carbon nanotubes exhibit high electrocatalytic activity toward the oxidation of H 2 O 2 , 8 their preparation still suffers from the involvement of an expensive machine for chemical vapour deposition and the use of toxic pyridine as a carbon source. In this communication, for the rst time, we demon- strate our recent nding that ultrathin g-C 3 N 4 nanosheets directly prepared by ultrasonication-assisted liquid exfoliation of bulk g-C 3 N 4 (ref. 9) can be used as a low-cost, green, and highly efficient electrocatalyst toward the reduction of H 2 O 2 . An amperometric sensor has been constructed for the determina- tion of H 2 O 2 within the linear range from 100 mM to 90 mM (r ¼ 0.9990) and the detection limit is estimated to be 2.0 mM at a signal-to-noise ratio of 3. We further demonstrate its glucose biosensing application in both buffer solution and human serum medium with a detection limit of 11 mM and 45 mM, respectively. The scanning electron microscopy (SEM) image of the bulk g-C 3 N 4 (Fig. 1A) indicates that they are solid agglomerates about several micrometers in size. Fig. 1B shows the photograph of the dispersion of the products obtained aer ultrasonication treat- ment of bulk g-C 3 N 4 . The occurrence of the Tyndall effect of the diluted dispersion in water reveals the colloidal nature of the dispersion. Fig. 1C presents the atomic force microscopy (AFM) image of the resulting colloidal particles, revealing that they are nanosheets well separated from each other. The thickness of these nanosheets was measured by section analysis to be 1.2 nm (Fig. 1D), suggesting they are in forms of four C–N layers. a State Key Lab of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022 Jilin, China. E-mail: sunxp@ciac.jl.cn; Fax: +86-431-85262065; Tel: +86-431-85262065 b Graduate School of the Chinese Academy of Sciences, Beijing 100039, China c Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia d Center of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah 21589, Saudi Arabia † Electronic supplementary information (ESI) available: Experimental section and supplementary gures. See DOI: 10.1039/c3nr02031b Cite this: Nanoscale, 2013, 5, 8921 Received 24th April 2013 Accepted 21st July 2013 DOI: 10.1039/c3nr02031b www.rsc.org/nanoscale This journal is ª The Royal Society of Chemistry 2013 Nanoscale, 2013, 5, 8921–8924 | 8921 Nanoscale COMMUNICATION Published on 12 August 2013. Downloaded by King Abdulaziz University on 15/09/2013 12:54:10. View Article Online View Journal | View Issue