Preparation and characterization of graphene oxide nanosheets - Core

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Procedia Engineering 32 (2012) 759 – 764

I-SEEC2011

Preparation and characterization of graphene oxide nanosheets T. Rattanaa,e*, S.Chaiyakuna,e, N.Witit-anuna,e, N. Nuntawongb, P. Chindaudomb, S. Oaewc ,C. Kedkeawd, P. Limsuwand,e a Department of Physics, Faculty of Science, BuraphaUniversity,Chonburi, 20131, Thailand Optical Thin- film Laboratory, National Electronis and Computer Technology Center,Pathumthani, 10120,Thailand c Biochemical Engineering and Pilot Plant Research and Development Unit,National Center for Genetic Engineering and Biotechnology, National Sciences and Technology Development Agency at King Mongkut’s University of Technology Thonburi (Bangkhuntien), Bangkok 10150, Thailand d Department of Physics, Faculty of Science, King Mongkut’s University of Technology Thonburi, Bangkok, 10140, Thailand e Thailand Center of Excellence in Physics(ThEP), CHE, Ministry of Education, Bangkok 10400, Thailand b

Elsevier use only: Received 30 September 2011; Revised 10 November 2011; Accepted 25 November 2011.

Abstract Graphene oxide (GO) has recently attracted great attention due to its unique chemical and physical properties. In this work, the GO nanosheets were prepared by a chemical exfoliation technique. The structural and optical properties of the as-prepared GO nanosheets were characterized by Raman, FTIR, UV-vis and photoluminescence spectroscopy. The FTIR results confirmed the existence of oxygen-containing groups on the GO nanosheets and the photoluminescence spectra of GO nanosheets showed the emission peak in the visible regions. These results indicate that the GO nanosheets could be used as a promising new material for biological applications such as biofunctionalization and fluorescence biosensors

© 2010 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of I-SEEC2011 Open access under CC BY-NC-ND license. Keywords: Graphene oxide,FTIR,Photoluminescence

1. Introduction During the last decade, carbon based nanomaterials such as carbon nanotube(CNT), fullerene and graphene have gained considerable interest because of their potential use as multifunctional materials and wide range of applications in different kind of devices [1]. Among these materials, graphene offers a

* Corresponding author. E-mail address: [email protected].

1877-7058 © 2012 Published by Elsevier Ltd. Open access under CC BY-NC-ND license. doi:10.1016/j.proeng.2012.02.009

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T. Rattana et al. / Procedia Engineering 32 (2012) 759 – 764

unique monolayer or few layers of sp2 hybridized carbon atoms arranged in a two-dimensional honeycomb lattice which has attracted much attention since its discovery in 2004 [2]. Due to its excellent physical and mechanical properties [3–5], it is a good candidate for various applications such as nanoelectronic, sensor, catalysis and photovoltaic [6-9]. Recently, graphene oxide (GO) an oxidized form of graphene, has gained more attention because it is easy to functionalize, able to label with fluorescent probe and compatible with most biomolecules. [10-12].These unique properties of GO make it a promising nanomaterial for bioapplication. In this study, GO nanosheets were synthesized from graphite oxide powder by chemical exfoliation method. The properties of GO including morphology structural and optical properties were investigated. 2. Experimental Section 2.1 Materials Natural graphite powder was obtained from Sigma Aldrich. Sulphuric acid of 98% concentration (98% H2SO4), hydrogen peroxide of 30% concentration (30% H2O2), potassium permanganate (KMnO4), sodium nitrate(NaNO3) and other reagents were of analytical grade and used as received. 2.2 Preparation of GO nanosheets GO nanosheets were prepared by a modified Hummers method [13]. Typically, 1.0 g natural graphite powder and 0.5 g sodium nitrate were mixed with 23 mL sulfuric acid in a 500 mL flask place in an ice bath. The obtained solution was stirred and slowly added 3 g potassium permanganate, the stirring was continued for 2 h. The mixture solution was transferred to a 35 oC water bath and stirred for 30 min. After that, 46 mL of deionized (DI) water was slowly added into the solution and the solution temperature monitored was about 98 °C. The mixture solution was maintained at this temperature by heating for 30 min. Then, 140mL deionized water and 10 mL of hydrogen peroxide was added sequentially to the mixture solution to terminate the reaction. The observed color of mixture was dark yellow. The resulting product was filtered and rinsed with 5% HCl solution followed by distilled water for several times. The graphite oxide powder was obtained after drying in vacuum at 60°C for 12 h. The powder was then dispersed in distilled water to make concentration of 0.5 mg/mL, and exfoliated by ultrasonication for 30 min to generate GO nanosheets, followed by centrifugation at 4000 rpm for 30 min to remove unexfoliated graphite oxide. Finally, the stable suspension of brown GO nanosheets was obtained. 2.3 Characterization The morphology of GO nanosheets was evaluated with a field emission scanning electron microscopy (FESEM, Hitachi, S-4700). The Fourier transformed infrared (FTIR) spectrum was measured with a Nicolet 6700 FT-IR Spectrometer in the range of 400–4000 cm-1. The microstructures of GO nanosheets were performed using Raman spectroscopy (NT-MDTNTEGRA Spectra) with a 633 nm laser beam. The UV-vis absorption spectrum was carried out in the range of 200–800 nm by a UV–vis spectrophotometer (Cary 50,Varian) and the room temperature photoluminescence (PL) spectrum were recorded with a Model Quanta Master 30 Fluorescence Spectrofluorometer. 3. Results and discussion The FESEM image of surface GO nanosheets obtained by a chemical exfoliation technique is shown in Fig. 1. It was found that GO nanosheets consists of randomly aggregated and crumpled thin sheets which


also observed with wrinkles and folds on the surface of GO nanosheets. This result confirmed that twodimensional nanosheets of GO can be produced from exfoliation of suspended graphite oxide.

Fig. 1. FESEM image of GO nanosheets

The characteristic FTIR spectrum of GO nanosheets is depicted in Fig. 2. It is seen with oxygencontaining groups in which the main absorption band at 3340 cmí1 is assigned to the O-H group stretching vibrations. The absorption peak at 1730 cmí1 and 1630 cmí1 can be assigned to C=O stretching of carboxylic and/or carbonyl moiety functional groups. The two absorption peaks at about 1226 cmí1 and 1044 cmí1 are assigned to the C–O stretching vibrations. This C=O group found in GO would facilitate the attachment of biomolecule such as DNA and protein or nanoparticles such as gold nanoparticle through a covalent coupling or electrostatic interaction, which could be further applied in biosensor applications [14-15].

Fig. 2. FT-IR spectrum of GO nanosheets

Fig. 3 reveals the UV-visible absorption spectrum of the suspened GO nanosheets. The main absorption peak at about 230 nm is attributed to the ʌ ĺ ʌ* transitions of aromatic C–C bond, and a

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shoulder at about 300 nm can be assigned to the ʌ ĺ ʌ* transitions of C=O bonds [16]. This result confirms the FTIR results on the existence of oxygen functional groups in GO nanosheets.

Fig. 3. UV-vis spectrum of GO nanosheets

Fig. 4 shows the Raman spectra of GO nanosheets which contain a strong band at ~1581 cm-1 (G band) and a weak band at ~1340 cm-1 (D band). The G and D bands are attributed to the first-order scattering from the E2g phonon of sp2 carbon bonding and structural defects (disorder-induced modes), respectively [17].

Fig. 4. The Raman spectrum of GO nanosheets


Fig. 5. PL spectrum of GO nanosheets

The PL spectrum of GO nanosheets shows PL emission maximum peak is at 450 nm for the excitation wavelength of 340 nm, as shown in Fig.5. The photoluminescence emission of GO nanosheets is believed to originate from the recombination of electron-hole pairs, localized within small sp2 carbon clusters embedded within sp3 matrix [18].The PL spectrum of GO nanosheets shows PL emission in visible range which could be applied in many fields such as biological labeling and fluorescence quenching [19-20]. 4. Conclusion In summary, GO nanosheets were prepared from exfoliation of graphite oxide powder. The structural and optical properties of the as-prepared GO nanosheets were characterized by Raman, FTIR, UV-vis and photoluminescence spectroscopy. The FTIR results confirmed the existence of oxygen-containing groups of the prepared GO nanosheets and the photoluminescence spectrum of GO nanosheets showed broad emission band peaked at 450 nm in visible region. The C=O groups of GO nanosheets enable immobilization of various biomolecules through the covalent bonding. Likewise, the photoluminescence characteristics of the prepared GO nanosheets allow them to be applied for a variety of biological applications such as biofunctionalization and fluorescence biosensors. References [1] Sharon Maheshwar, Sharon Madhuri.Carbon nanoforms and applications. New York: McGraw-Hill: 2010. [2] Novoselov KS, Geim AK, Morozov SV, Jiang D, Zhang Y, Dubonos SV, Firsov AA. Electric field effect in atomically thin carbon films, Science 2004; 306:666–669. [3] Berger C, Song Z, Li X, Wu X, Brown N, Naud C. Electronic confinement and coherence in patterned epitaxial graphene. Science 2006; 312:1191–6. [4] Stankovich S, Dikin1 DA, Dommett GHB, Kohlhaas KM, Zimney EJ, Stach EA. Graphene-based composite materials. Nature 2006; 442: 282–286. [5] Gao Y, Hao P. H. Mechanical properties of monolayer graphene under tensile and compressive loading. Physica E: Lowdimensional Systems and Nanostructures 2009; 41:1561-1566.

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