Electronic Supplementary Material (ESM)

Electrochemical synthesis of a graphene sheet and gold nanoparticle-based nanocomposite, and its application to amperometric sensing of dopamine

Su-Juan Li*, De-Hua Deng, Qi Shi, Shui-Ren Liu

School of Chemistry and Chemical Engineering, Anyang Normal University, Anyang 455002, China

*Corresponding author, e-mail: (S.J. Li), Tel&Fax: +86-0372-2900040

FTIR and Raman spectroscopy of the prepared ERGO

FTIR spectra of the prepared ERGO films were characterized (Fig S1). Curve a shows the pure GO, the bands around 976, 1056, 1226, 1276, 1384, 1580 and 1727 cm-1 are attributed to the oxygen-containing functional groups on GO [1], while the band at ca. 1619 cm-1 could be due to the O-H stretching deformation vibration of intercalated water. After electrochemical reduction, the FTIR adsorption bands of oxygen functionalities decrease significantly and even disappear (curve b), which confirmed the successful conversion of GO into graphene.

Fig S1. FTIR spectra of GO (a) and ERGO films (b).


To obtain further information on the structure and electronic properties of graphene including disorder and defect structure, Raman spectroscopy was carried out. In many cases, the Raman spectrum of graphene is characterized by two main features, G band is usually assigned to the E2g phonon of C sp2 atoms, while D band is a breathing mode of κ-point phonons of A1g symmetry. Herein, as shown in figure S2, it should be noted that the frequency of the G and D bands in the ERGO are very similar to that observed in the GO. However, the D/G intensity ratio of ERGO is enhanced compared with exfoliated GO. These results are consistent with other’s research for fabrication of graphene from GO precursor [2]. The appearance of 2D band in curve b further indicates the conversion of GO to graphene. But because of the existence of defects on ERGO, the 2D peak is weak and broadened compared to bulk graphite [3].

Fig. S2 Raman spectra of exfoliated GO and ERGO at reduction potentials of -0.8 V


TEM image of the prepared ERGO

Fig. S3 TEM image of ERGO

Comparison of the cyclic voltammograms of AuNPs/GO/GCE and AuNPs/ERGO/GCE

Comparison of the cyclic voltammograms of AuNPs/GO/GCE and AuNPs/ERGO/GCE was displayed in Fig S4. It is obvious that the current responses of DA on AuNPs/ERGO/GCE are much larger that those on AuNPs/GO/GCE due to the increased conductivity of ERGO after electrochemical reduction.

Fig. S4 Cyclic voltammograms of different electrodes in 0.1 M phosphate buffer solution (pH=6.98) containing of 0.1 mM DA. Curves were obtained using different electrodes: AuNPs/GO/GCE (a) and AuNPs/ERGO/GCE (b); Scan rate: 50 mV·s-1.

References

[1] Zhou M, Zhai Y, Dong S (2009) Electrochemical Sensing and Biosensing Platform Based on Chemically Reduced Graphene Oxide. Anal Chem, 81:5603-5613

[2] Guo HL, Wang XF, Qian QY, Wang FB, Xia XH (2009) A green approach to the synthesis of graphene nanosheets. ACS Nano 3:2653-2659

[3] Zhu C, Guo S, Fang Y, Dong S (2010) Reducing Sugar: New Functional Molecules for the Green Synthesis of Graphene Nanosheets. ACS Nano, 4:2429-2437