Wang et al. Nanoscale Research Letters 2012, 7:161 http://www.nanoscalereslett.com/content/7/1/161 N A N O E X P R E S S Open Access Comparative studies on single-layer reduced graphene oxide films obtained by electrochemical reduction and hydrazine vapor reduction Zhijuan Wang1, Shixin Wu1, Juan Zhang1, Peng Chen1,2, Guocheng Yang3, Xiaozhu Zhou1, Qichun Zhang1, Qingyu Yan1 and Hua Zhang1* Abstract The comparison between two kinds of single-layer reduced graphene oxide (rGO) sheets, obtained by reduction of graphene oxide (GO) with the electrochemical method and hydrazine vapor reduction, referred to as E-rGO and C- rGO, respectively, is systematically studied. Although there is no morphology difference between the E-rGO and C- rGO films adsorbed on solid substrates observed by AFM, the reduction process to obtain the E-rGO and C-rGO films is quite different. In the hydrazine vapor reduction, the nitrogen element is incorporated into the obtained C- rGO film, while no additional element is introduced to the E-rGO film during the electrochemical reduction. Moreover, Raman spectra show that the electrochemical method is more effective than the hydrazine vapor reduction method to reduce the GO films. In addition, E-rGO shows better electrocatalysis towards dopamine than does C-rGO. This study is helpful for researchers to understand these two different reduction methods and choose a suitable one to reduce GO based on their experimental requirements. Introduction Graphene, a kind of two-dimensional carbon materials, has attracted increasing attention [1-3]. Recent studies proved that the graphene-related materials have excel- lent characteristics in various applications such as synth- esis of hybrid materials [4-11], capacitors [12,13], sensors [11,14-20], electric devices [21-24], solar cells [25-27], drug delivery [28,29], cell imaging [29], and cell cultures [30], etc. In order to produce large amount of graphene-related materials, the chemical methods are generally used [31-33]. Normally, graphene oxide (GO) is synthesized by the modified Hummers method [31-33], which is a strong oxidation method by using the concentrated sulfuric acid and potassium permanganate as oxidation agents. During the oxidation, the π-π electronic conjugation of graphite is destroyed, and the carbon sheets are * Correspondence: hzhang@ntu.edu.sg 1School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singaporea Full list of author information is available at the end of the article decorated with the epoxide and hydroxyl groups in their basal planes as well as the carbonyl and carboxyl groups at their edges [34-36]. These functional groups render GO hydrophilic, facilitating the dispersion of GO in aqueous solution. After the reduction of GO with hydroquinone [37], NaBH4 [38], hydrazine hydrate [39], hydrazine vapor [31,40-43], or hydrazine with NH3 [44], GO is deoxygenated and reduced GO (rGO] is obtained. However, these reducing agents, particularly hydrazine, are toxic, and the use of them should be with extreme care and minimized [45]. In addition, the excessive reducing agents might contaminate the resulting pro- duct, i.e. rGO. Recently, our group [46] and other groups [47-49] independently developed an electrochemical method to reduce GO, which is simple, fast, and green, as com- pared with the aforementioned chemical methods. More importantly, the highly negative potential used in the electrochemical method can overcome the energy bar- riers to efficiently reduce the oxygen-containing func- tional groups in GO [47]. © 2012 Wang et al; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.