Wang et al. Nanoscale Research Letters 2012, 7:161 http://www.nanoscalereslett.com/content/7/1/161 activity of E-rGO might arise from the smaller amount of oxygen functional groups left on the surface of E- rGO. Therefore, E-rGO, instead of C-rGO, was applied to detect DA in the mixture solution in the following experiment. Using the differential pulse voltammetric (DPV) tech- nique, DA was detected with E-rGO (Figure 5). The peak intensity of DA increased with the concentration of DA (Figure 5A). Note that the DPV peak current is linear to the concentration of DA in the range of 0 to 50 μM (Figure 5B). Even at the very low concentration of DA, e.g. 1 μM, DA can be detected from the mixture of 1 mM AA, 0.1 mM UA, and 1 μM DA. Conclusions Single-layer rGO, obtained by electrochemical method (referred to as E-rGO) and hydrazine vapor reduction (referred to as C-rGO), respectively, was compared in morphology and the component change after reduction and electrocatalysis towards DA. In the hydrazine vapor reduction, nitrogen was incorporated into the product, while no additional element was introduced during the electrochemical reduction. After reduction, the mor- phology has not shown obvious difference between the single-layer GO and rGO films. However, the CV results indicate that the electrochemical method is more effec- tive to reduce GO films than does the hydrazine vapor reduction method. In addition, the product E-rGO showed better electrocatalysis towards dopamine than does C-rGO. Our comparative study is helpful for researchers to understand these two reduction methods and choose a suitable one to reduce GO based on their experimental requirements. Additional material Additional file 1: Figure S1 and Figure S2. For Figure S1, AFM images of (A) ITO-APTES-GO, (B) ITO-APTES-E-rGO, (C) SiO2-APTES-GO and (D) SiO2-APTES-C-rGO. For Figure S2, proposed mechanism for reduction of ketone in GO by hydrazine vapor [2]. Acknowledgements This work was supported by MOE under AcRF Tier 2 (ARC 10/10, No. MOE2010-T2-1-060), the Singapore National Research Foundation under CREATE programme: Nanomaterials for Energy and Water Management, and NTU under the New Initiative Fund FY 2010 (M58120031) in Singapore. Author details 1School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singaporea 2Center for Biomimetic Sensor Science, Nanyang Technological University, 50 Nanyang Drive, Singapore 637553, Singapore 3School of Chemistry and Life Science, Changchun University of Technology, 2055 Yan’an Street, Changchun, Jilin 130012, People’s Republic of China Page 6 of 7 Authors’ contributions HZ led the project, participated in the design of the experiments, analysis of the data and revision of the manuscript. ZW designed and carried out the experiments, and drafted the manuscript. SW and JZ carried out some electrochemical experiments. 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