graphene oxide nanocomposite

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2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of .... spectrometer (made in Bruker Company). .... [1] Liu F, Choi JY, Seo TS.
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Procedia Engineering 00 (2011) 000–000 Procedia Engineering 27 (2012) 1478 – 1487

Procedia Engineering www.elsevier.com/locate/procedia

2011 Chinese Materials Conference

Praparation, characterizations, and its potential applications of PANi/ graphene oxide nanocomposite Jing Zhenga, Xingfa Ma a, b,*, Xiaochun Hea, Mingjun Gaoa, and Guang Lic a

School of Environmental and Material Engineering, Center of Advanced Functional Materials, Yantai University, Yantai 264005, P. R. China. b State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027, P. R. China. c National Laboratory of Industrial Control Technology, Institute of Advanced Process Control, Zhejiang University, Hangzhou 310027, P. R. China.

Abstract Graphene oxide (GO), nano/micro-structured polyaniline (PANi) are some typical important functional materials, which have many applications in lithium ion battery with high energy, supercapacitor, catalysts, solar cells, nanodevices, chemical sensors, biosensors and biomedical fields. In this paper, GO was obtained by using chemical oxidation method at room temperature, and nano/micro-structured GO/PANi composite was prepared with in-situ polymerization of aniline in the presence of GO suspension. A series of characterizations were examined by TEM (transmission electron microscopy), SEM (scanning electron microscope), XRD (X-ray diffraction), the FourierTransform Infrared (FTIR) spectra, UV-Vis, et al. The results indicated that most of the surface of GO sheets was covered with a smooth thin layer of polyaniline, and some domains of the surface of GO sheets were clearly observed polyaniline nanowires anchored. To examine the surface and interface properties of GO/PANi nanocomposite, chemical prototype sensors were constructed based on GO/PANi nanocomposite and a QCM (quartz crystal microbalance) device. The response behaviors of the sensor to some typical volatile compounds operating at room temperature were investigated. The adsorption features to some typical volatile compounds were discussed. Some key issues and modification ideas were suggested for further investigation.

©©2011 2011Published PublishedbybyElsevier ElsevierLtd. Ltd.Selection Selectionand/or and/orpeer-review  peer-reviewunder underresponsibility responsibilityof ofChinese ChineseMaterials Materials Research ResearchSociety SocietyOpen access under CC BY-NC-ND license. Keywords: Graphene oxide (GO); Nanocomposites; Surface and Interface Features; Adsorption Response; Chemical sensors

*

Corresponding author. Tel.: +86-535-6706039; fax: +86-535-6902264. E-mail address: [email protected], [email protected].

1877-7058 © 2011 Published by Elsevier Ltd. Selection and/or peer-review  under responsibility of Chinese Materials Research Society Open access under CC BY-NC-ND license. doi:10.1016/j.proeng.2011.12.611

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1. Introduction Currently, nano/micro-structured functional materials and their applications have received considerable attentions due to many outstanding properties. These typical important applications are involved in lithium ion battery with high energy, supercapacitor, catalysts, solar cells, nanodevices, chemical sensors, biosensors and biomedical fields. As simple and typical devices, chemical sensors have potential applications in many fields, such as environmental monitoring, detection of explosives, medical diagnoses, and so on [1-20]. Due to the large surface to volume ratios, nano/micro-structured functional materials have been predicted and demonstrated to be excellent functional material candidates for catalysis, solar cells, rechargeable batteries, ultrasensitive sensors, et al. These functional material, include inorganic materials, organic materials and organic-inorganic hybrid materials. Graphene, as one of the most hot-spot functional materials, a two-dimensional monolayer of sp2bonded carbon atoms, has attracted increasing attention in recent years, mainly due to its extraordinarily high electrical conductivities, large specific surface area, and low manufacturing cost. Graphene has been explored for applications in fabricating nanoelectronic devices, energy storage devices, sensors, transparent electrodes and nanocomposites [1-10, 17-20]. In particular, the composites of graphene and polymers are of scientific and industrial interest because of synergetic or complementary behaviors. Currently, the research on graphene and its composites have mainly focused on the preparation, modification and different applications. Reviewed the current references on GO and its composites, good progress was obtained. For example, Liu and co-workers [1] used GO sheets as a novel DNA biosensor by applying the GO in an array format to recognize specific DNA/DNA hybridization interaction. Fang and co-workers [2] reported the use of cationic polyelectrolyte poly (diallyldimethyl ammonium chloride) (PDDA) functionalized graphene nanosheets (GNs) as the building block in the self-assembly of GNs/Au nanoparticles (NPs) heterostructure to enhance the electrochemical catalytic ability, and employed the high-loading Au NPs on graphene (GN/Au-NPs) as the material for H2O2 electrochemical sensing. Wang and co-workers [21] examined the effect of graphene oxide on the properties of its composite with polyaniline. These results showed enhanced specific capacitance and cycling life implies a synergistic effect between two components. In the case of functional films, modified synthetic methods, and properties examinations, there are still large numbers of relative reports on graphene and its composites. Yan and co-workers [22] fabricated the free-standing, electrochemically active, and biocompatible graphene oxide/polyaniline and graphene/polyaniline hybrid papers. These hybrid papers displayed a remarkable combination of excellent electrochemical performances and biocompatibility, making the paperlike materials attractive for new kinds of applications in biosciences. Liu and co-workers [17] reported graphene-based supercapacitor with an ultrahigh energy density. Zhang and co-workers [18] demonstrated a general approach to the preparation of layered graphene oxide nanostructures with sandwiched conducting polymers as supercapacitor electrodes. Kim and co-workers [23] prepared silver (Ag) nanoparticles deposited on graphene sheets by chemical reduction and Ag doped graphene (Ag-GR)/polypyrrole (PPy) nanocomposites by oxidation polymerization method. The effect of the Ag-GR incorporation on the electrochemical properties of the PPy nanocomposites was investigated. It was found that highly dispersed Ag nanoparticles (2–5 nm) could be deposited onto the GR and that Ag/GR was successfully coated by PPy. Ag/GR showed higher electrocatalytic activity than that of pristine GR. Furthermore, the Ag-GR/PPy showed remarkably increased current density, quicker response, and better specific capacitance compared with GR/Ppy composite. Xu and co-workers [24] introduced a facile method to construct hierarchical nanocomposites by combining one-dimensional (1D) conducting polyaniline (PANI) nanowires with 2D graphene oxide (GO) nanosheets. PANI nanowire arrays are aligned vertically on GO substrate. The morphologies of PANI

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nanowires can be controlled by adjusting the ratios of aniline to GO, which are attributed to different nucleation processes. The hierarchical nanocomposite structures of PANI/GO were further proved by UV-vis, FTIR, and XRD measurements. The hierarchical nanocomposite possessed higher electrochemical capacitance and better stability than each individual component as supercapacitor electrode materials, showing a synergistic effect of PANI and GO. Zhang and co-workers [19] prepared chemically modified graphene and polyaniline (PANI) nanofiber composites. The obtained graphene oxide/PANI composites with different mass ratios were reduced to graphene using hydrazine followed by reoxidation and reprotonation of the reduced PANI to give the graphene/PANI nanocomposites. It was found that the chemically modified graphene and the PANI nanofibers formed a uniform nanocomposite with the PANI fibers absorbed on the graphene surface and/or filled between the graphene sheets. Such uniform structure together with the observed high conductivities afforded high specific capacitance and good cycling stability during the charge-discharge process when used as supercapacitor electrodes. Laith and co-workers [25] reported the synthesis of a graphene/polyaniline (PANI) nanocomposite and its application in the development of a hydrogen (H2) gas sensor. It showed that the graphene/PANI nanocomposite-based device sensitivity is 16.57% toward 1% of H 2 gas, which is much larger than the sensitivities of sensors based on only graphene sheets and PANI nanofibers. Sanjib and co-workers [26] developed a novel nanoarchitecture by combining the nanostructured polypyrrole with highly electrically conductive graphene nanosheets in a multilayered configuration to achieve high specific capacitance and low electronic resistance for supercapacitor electrode applications. This multilayer composite electrode exhibited a high specific capacitance with a nearly ideal rectangular cyclic voltammogram at increasing voltage scanning rates and high electrochemical cyclic stability. Zhao and co-workers [27] reported polyaniline electrochromic devices with transparent graphene electrodes. Yan and co-workers [20] prepared a graphene nanosheet/polyaniline composite with high specific capacitance. Wu and co-workers [28] introduced supercapacitors based on flexible graphene/polyaniline nanofiber composite films. Si and co-workers [29] synthesized water soluble graphene. This method is facile and scalable, which has promising applications in many fields. Marcano and co-workers [30] improved method for the preparation of graphene oxide (GO) by performing the reaction in a 9:1 mixture of H2SO4/H3PO4. This improved method provides a greater amount of hydrophilic oxidized graphene material as compared to Hummers’ method or Hummers’ method with additional KMnO4. Lu and co-workers [31] demonstrated highperformance gas sensors based on graphene oxide (GO) sheets partially reduced via low-temperature thermal treatments. Goncalves and co-workers [32] carried out surface modification of graphene nanosheets with gold nanoparticles. Kamat [33] anchored semiconductor and metal nanoparticles on a twodimensional graphene support and discussed potential applications in catalysis, light energy conversion, and fuel cells. Xu and co-workers [34] prepared graphene-metal particle nanocomposites. Li and coworkers [35] assembled gold nanoparticles on graphene oxide sheets with dip pen nanolithographygenerated templates. Subrahmanyam and co-workers [36] studied graphene decorated with metal nanoparticles by employing raman spectroscopy and first-principles calculations. Zhou and co-workers [3] developed a novel hydrogen peroxide biosensor based on Au/graphene/HRP/chitosan biocomposites. Robinson and co-workers [4] reported molecular sensors based on reduced graphene oxide. Fowler and coworkers [5] fabracated practical chemical sensors from chemically derived graphenen and so on. On the other hand, conducting polymers (CPs) also have been extensively studied and widely applied in various organic devices and functional films [11,15,16,28]. To improve the performances or extend the functions and applications of the materials, CPs usually have to be nanostructured or modified with different modifiers. Polyaniline (PANI) is a typical CP with good environmental stability, interesting electroactivity, and unusual doping/dedoping chemistry. Nano/micro-structured PANI can be synthesized through various chemical approaches. Up to now, the methods to prepare conductive polymers with micro/nano-structures involve in hard template methods, soft template approachs, electropolymerization,

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electro-spinning, nano-fiber seeding approaches, biological templated approach and so on, and they have been applied for fabricating chemical sensors, biosensors, actuators, memory devices, batteries, and supercapacitors [37-45]. Up to now, many references reported graphene or graphene oxide and polyaniline nanocomposite with enhanced some properties [7,18-26,46-50], specially electrochemical properties. And most of the applications is mainly focussed on the supercapacitors. In order to obtain some chemical sensors and biosensors with controlled sensitivity and selectivities, we [14] had ever obtained nanowire-structured conductive polymers, which showed good responses to several chemical vapors. We also prepared some polyaniline/inorganic nanocomposites, and examined their gas-sensing behaviors to some gases, and reviewed morphology tailoring of nano/micro-structured conductive polymers, composites and their applications in chemical sensors [42-44]. In order to further widen nanocomposites for construction of some chemical sensors and biosensors, we prepared the GO/polyaniline nanocomposite and studied the gas sensing behaviors to several typical gases. Herein, the praparation, characterizations, and its potential applications of PANi/graphene oxide nanocomposite were reported. Some suggestions were proposed. 2. Experimental 2.1. Materials Graphite, Potassium Permanganate (KMnO4)(AR), Aniline (Analytical Reagent, i.e. AR) was freshly distilled in vacuum prior to use, ammonium peroxydisulfate (AR), hydrochloride acid (AR), dry sulfuric acid (AR), nitric acid (AR), ammonia (AR) were all commercially available. Deionized filtered water was used in all studies. 2.2. Preparation of graphene oxide (GO) About 1-3 g portion of graphite was added to 1000 mL of a mixture of dry sulfuric acid/ nitric acid (3:1 by volume, respectively). Appropriate potassium permanganate (KMnO4) was added. The mixture was sonicated in a bath for 0.5-1 h at ambient temperature. Standing over 96 h, then the mixture was diluted with distilled water, followed by filtering, and washed with an excess of water until no residual acid was present. GO suspension was obtained. 2.3. Preparation of GO/ polyaniline(PANi) nanocomposite 50-60 mL GO suspension was added to 500 mL vessel, equimolar aniline and ammonium peroxydisulfate were added to form a homogeneous solution, sonicated in a bath for 10-30 min., and placed at room temperature over 24h. The blue-black solution of polyaniline/GO in water was obtained. After the reaction was completed, the resulting solid product was washed with distilled water repeatedly to remove possibly remnant in the final products. The resulting-products of GO/polyaniline nanocomposite were obtained. 2.4. Morphology observations with TEM The transmission electron microscopy (TEM) observation was performed with a JEM-2000CX under an acceleration voltage of 160 kV. 2.5. Morphology observations with SEM

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The scanning electron microscopy (SEM) observation was performed with Hitachi SU-70 (Japan). The sample obtained was washed with deionized water, deposited on the glass substrate, dried at room temperature, and sputtered with a thin layer of Pt on the surface for SEM observation. 2.6. Measurement of FTIR Spectrum The FTIR spectrmu were taken with KBr, and recorded on an IFS 66V/S Fourier transform infrared spectrometer (made in Bruker Company). A small amount of polyaniline/GO powder and some amounts of KBr were mixed, pressed into a small slice of sample, and then dried at room temperature for determination. 2.7. Measurement of UV-vis Spectrum The UV-vis was recorded by a CARY Bio100 spectrophotometer. The samples were GO or GO/PANi suspension. 2.8. XRD characterization X-ray diffraction (XRD) patterns were recorded using a Rigaku D/max 2550 Pe diffraction device, rotating anode X-ray generator working at 40 kV, 300 mA, with Cu Ka monochromatic radiation. 2.9. Construction of prototype sensors GO/PANi nanocomposite above-prepared was firstly dispersed in deionized water (about 0.1-0.2 % wt.), which was used as the sensing layer of the QCM sensors [51]. The QCM sensors were fabricated as follows: the AT-cut 6.000 MHz crystal was rinsed repeatedly into ethanol and deionized water and dried in air at room temperature. Two microliters of GO/PANi dispersion aqueous solution was dispensed onto the surface of the electrode using a micropipette. After the device was dried at room temperature, a GO/PANi modified QCM sensor was obtained. 2.10. Characterization of the gas-response of the sensors (Sensor’s Gas-Sensitivity) Two same type QCM devices were set in a sealed chamber [51]. One coated with GO/PANi film was used as the sensing device while the other without GO/PANi was used as the reference. The frequency difference between two QCMs was determined by mass changes of the GO/PANi coated on the sensing QCM. The instrumentation utilized consisted of driving circuits and a frequency counter. The driving circuits made the QCMs oscillate and output the frequency difference. The frequency difference was measured by the frequency counter and sent to an IBM compatible computer via a RS-232 serial communication port. 3. Results and discussion We prepared GO, PANi, and GO/PANi nanocomposites in the experiments. Their typical TEM images are shown in Fig. 1. The morphology of GO obtained by chemical oxidation is shown in Fig. 1 (a). The typical morphology of PANi obtained for comparsion is shown in Fig. 1 (b). The typical morphology of GO/PANi nanocomposite is shown in Fig. 1 (c).

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(a)

(b)

(c)

Fig. 1 Comparative TEM images of (a) GO, (b) PANi and (c) GO/PANi nanocomposite.

As shown from Fig. 1(a), some corrugations on GO sheet were clearly observed. This is very good agreement with some references reported. Fig.1(b) showed that nanowire structure of PANi obtained in our experiments. As shown from Fig. 1(c), we can see that most of GO surface was covered with a smooth thin polyaniline layer, and some domains of the surface of GO sheets was anchored polyaniline nanowires. In order to observe the surface of GO/PANi nanocomposite more distinctly, we took SEM imgaes for comparsion. The results are shown in Fig.2. (a)

(b)

Fig. 2 Comparative SEM images of (a) PANi and (b) GO/PANi nanocomposite.

As shown from Fig.2, we can more clearly observe the surface features of GO/PANi nanocomposites. These results are good consistent with the information of TEM images obtained. The results still indicated that most of GO surface was coated with a smooth thin polyaniline layer, and some regions of the surface of GO sheets were deposited polyaniline nanowires. The experiments of FTIR and UV-Vis of GO/PANi nanocomposites were also carried out. The FTIR and UV-Vis curves are shown in Fig.3 and Fig.4. Fig.3 shows that some chief characteristic bands of polyaniline were clearly observed in the GO/PANi nanocomposite. Such as, the bands at 3233, 3406, 3475 cm-1 are attributed to N-H stretching in the quinoid ring of the emeraldine base and emeraldine salt, 1591, 1604 cm-1 are attributed to C=C stretching in the quinoid ring of the emeraldine base and emeraldine salt, 1303, 1315 cm-1 are attributed to C-N C=N stretching, respectively. These results illustrate that this resulting-product contained polyaniline.

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Fig.4 shows that two clear peaks in 432, 760 nm in UV-Vis spectrum in GO/PANi nanocomposite, similar to that of PANi. These also illustrate that this resulting-product contained polyaniline.

Fig. 3 FTIR of GO/PANi nanocomposite.

Fig. 4 UV-Vis of GO/PANi nanocomposite.

So far, for GO/PANi nanocomposites, most of researches have focussed on the applications in lithium ion battery with high energy, supercapacitor, catalysts, et al. Some good progresses were obtained and several reviews have been published [52, 53]. However, there is a little references on chemical sensors, although some reports on chemical senosrs and biosensors have been reported. There are still great challenges on GO based sensors. Herein, preliminary experiments on properties of GO/PANi nanowire composite based chenmical sensors were carried out. We all know that the ammonia, toluene gas are typical toxic gases in common. Herein, the response behaviors of GO/PANi nanocomposite to some typical organic vapors were examined. The results are shown in Fig.5-7.

Fig.5 Response behavior of GO/PANi nanocomposite to 30 mL saturated ammonia vapor diluted in a 1000 mL chamber with N2.

Fig.6 Response behavior of GO/PANi nanocomposite to 30 mL saturated toluene vapor diluted in a 1000 mL chamber with N2 at similar conditions.

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Fig.7. Response behaviors of GO/PANi nanocomposites to different vapors in similar test conditions.

Fig.5-7 showed that GO/PANi nanocomposite exhibited good responses to some typical organic vapors, which showed different sensitivities to different vapors at similar test conditions. Therefore, the GO/PANi nanocomposites would have many important potential applications in chemical sensors or biosensors, which deserved for further invertigation in details, specially improved their sensitivity, selectivity, and processing technology with some more simple approaches. We also examined the gassensing behaviors of GO based nanocomposites modified with several metal oxides, metals and some functional polymers, and obtained some good results. Herein, the improvements of the nanocomposites to organic vapors were not intended to be introduced for save space, which have been published in another paper. 4. Conclusion In summary, GO was prepared by using chemical oxidation method at room temperature, and GO/PANi nanowire composite was obtained with in-situ polymerization of aniline in the presence of GO suspension. A series of characterizations were examined by TEM (transmission electron microscopy), SEM (scanning electron microscope), XRD (X-ray diffraction), the Fourier-Transform Infrared (FTIR) spectra, UV-Vis, et al. These results showed that most of the surface of GO sheets was covered with a smooth thin layer of polyaniline, and some domains of the surface of GO sheets were clearly observed polyaniline nanowires anchored. To examine the surface and interface properties of GO/PANi nanocomposite, chemical prototype sensors were constructed based on GO/PANi nanocomposite and QCM device. The GO/PANi nanocomposite exhibited good responses to some typical organic vapors. Therefore, the GO/PANi nanocomposites would have potential applications in chemical sensors, biosensors or flexible nanoelectronic devices. Acknowlegements This project was supported by the Natural Science Foundation of Shandong Province (project No. Y2008F24), Science Fundation of National Laboratory of Industrial Control Technology (ICT1005 ), and Science Fundation of State Key Lab of Silicon Materials (project No. SKL2008-7), Zhejiang University.

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