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[2] Chambers A, Park C, Baker RTK, Rodriguez NM. J Phys [5] Ackley MW, Yang RT. AIChE J, 1991;37:1645.Chem B, 1998;102:4253. [6] Chen P, Zhang H-B, Lin G-D, Hong Q, Tsai KR. Carbon,

[3] Chen P, Wu X, Lin J, Tan KL. Science, 1999;285:91. 1997;35:1495.[4] Goethel PJ, Yang RT. J Catal, 1986;101:342. [7] Chen SG, Yang RT. J Catal, 1993;141:102.

Direct synthesis of a polyaniline-intercalated graphite oxidenanocomposite

Peng Xiao, Min Xiao, Pinggui Liu, Kecheng Gong*Polymer Structure & Modification Research Laboratory, South China University of Technology, Guangzhou, 510640, PR China

Received 4 October 1999; accepted 17 November 1999

Keywords: A. Graphite oxide; B. Intercalation; D. Electrical properties

Although conducting polymers such as doped poly- (electrical and thermal properties, etc) of graphite oxide tobe greatly changed. But the X-ray diffraction analysisacetylene can possess near metallic properties, ideal con-shows that this nanocomposite had a poor crystallineducting polymers for use in electronic devices are not atstructure. Here a new approach was developed for thepresent a reality because charge carriers mobilities are toosynthesis of polyaniline-intercalated GO nanocomposites.low to be useful. Garnier and his coworkers [1] hasThe result of X-ray diffraction shows that this compoundprepared organized thin films of oligomers, but even forhas a higher crystallinity regularity than that of thethese the mobilities are around 4 orders of magnitudepreviously prepared materials.lower than those in crystalline silicon. For optimum carrier

GO was prepared by the previously reported proceduremobility, it appears to be necessary to produce a single[12]. 2 g of dried GO were put into 50 ml of aniline in acystal polymer, or at least a form that is largely crystalline.closed vessel, and this was stirred at ambient temperatureBased on these reason, research on electroactive polymersfor 24 hours and then centrifuged. The precipitate washas recently focused on developing materials with a well-washed with acetone three times and dried at 508C for 24defined microstructure that is controllable at the nanometerhours and the aniline /GO intercalation complex waslevel [2–7]. Toward this end, the Langmuir-Blodgett (L-B)obtained.techniques widely used for processing electrically conduct-

Polyaniline /GO nanocomposite was prepared using theing polymers into well-defined multilayered film structuresfollowing procedure. 2 g of the aniline /GO intercalate waswith alternating conducting / insulating layers [8–10].added in a closed vessel to 50 ml of a diethyl etherAnother way to obtain orientation of polymer chains wouldsolution of anhydrous FeCl and the suspension was keptbe to grow them inside a structurally organized host 3

stirring at ambient temperature for 48 hours, then cen-framework. Among these systems, a intercalation oftrifuged, and the precipitate was washed with redistilledpolymers into the interlayer space of two-dimensionalwater until FeCl was removed completely. The solid wasinorganic systems has received a great deal of attention 3

dried under vacuum at 508C for 24 hours.because the intercalation offers a means to simultaneouslyFig. 1 shows the X-ray diffraction patterns of theassemble thousands of layers by allowing guest molecules

polyaniline-GO nanocomposite together with that ofto diffuse in the van der Walls gaps provided by theaniline-GO intercalation compound and pristine graphitelayered lattice.oxide. XRD analysis of the aniline-GO intercalation com-Intercalation of polyaniline into layered host materials

˚pound revealed a stacking height of 14.43A (Fig. 1b), anhas been extensively studied. More recently a polyaniline-˚ ˚intercalated graphite oxide (GO) nanocomposite, which expansion of 6.6A relative to the pristine GO (7.82A),

was prepared via an exfoliation-adsorption process, has which is indicative of formation of the aniline-intercalatedalready been reported [11,12]. The existence of polyaniline GO nanocomposite structure. When this compound isbetween the layers enables the physiochemical properties exposed to the diethyl ether solution of anhydrous FeCl ,3

oxidative polymerization of aniline occurred and the*Corresponding author. polyaniline-GO nanocomposite was formed. The interlayer

˚E-mail address: psyhzhan@scut.edu.cn (K. Gong). spacing increased to 15.28 A (Fig. 1c), which is contrary to

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Letters to the editor / Carbon 38 (2000) 623 –641 627

Fig. 1. X-Ray Patterns of (a) GO, (b) Aniline /GO Compound, and (c) Polyaniline /GO Nanocomposite.

the observed that the interlayer spacing decreased after crystalline structure favoring higher mobilities of themonomer polymerization [12]. The reason for this can be charge carriers.ascribed to the fact that anhydrous FeCl functions both as3

a polymerization initiator and a dopant. The volume ofpolyaniline doped with FeCl3 is larger than that of Acknowledgementsundoped polyaniline.

Evidence for the polymerization of aniline was provided Financial Support from Key Project of the Nationalby IR spectroscopy. The basic form of polyaniline can be Science Foundation of China (No. 59836230) is gratefullydescribed by the general formula h[–(C H )–NH– acknowledged.6 4

(C H )–NH–] [–(C H )–N5(C H )5N–] j , where6 4 1–x 6 4 6 4 x n

the value x,0,1) defines the oxidation state of thepolymer [13]. In FTIR spectra of the above intercalation Referencescompounds, bands at 1571.7, 1475.3, 1141.7 and

211297.9 cm of polyaniline were observed, this suggests [1] Garnier F, Horowitz G, Peng XZ, Fichou D. Structural basisthat aniline formed the emeraldine salt form during in situ for high carrier mobility in conjugated oligomer. Synth Metpolymerization. 1991;45(2):163–71.

Electrical Conductivity data were obtained by DC ´[2] Fusalba F, Belanger D. Chemical synthesis and characteriza-measument on 1.5 cm diameter pellets pressed from tion of polyaniline-molybdenum trisulfide composite. J

Mater Res 1999;14(5):1805–13.powders, using a SDY-IV four-probe instrument. The[3] Challier T, Slade RCT. Nanocomposite materials:poly-polyaniline intercalated GO nanocomposite was molded

aniline-intercalated layered double hydroxides. J Materinto discs (typically 1 mm thick) by compression (¯100Chem 1994;4(3):367–71.MPa). The result shows that the electrical conductivity of

[4] Mehrotra V, Giannelis EP. Metal-insulator molecular multi-23the intercalation compound is 3.65310 S/cm, fourlayers of electroactive polymers:intercalation of polyaniline

orders of magnitude higher than that of the pristine GO. in mica-type layered silicates. Solid State CommunicationWhen polyaniline-intercalated GO was reduced with aque- 1991;77(2):155–8.ous hydrazine hydrate (50% w/v) solution for 24 hr, the [5] Hong K, Ronser RB, Rubner MF. Langmuir-Blodgett ma-conductivity increased to 0.52 S/cm. Augmentation of nipulation of electrically conductive polypyrroles. Chemconductivity of the nanocomposite indicates a regular Mater 1990;2(1):82–8.

628 Letters to the editor / Carbon 38 (2000) 623 –641

[10] Royappa AT, Rubner MF. Novel Langmuir-Blodgett films of[6] Wu CG, Degroot DC, Marcy HO, Schindler JL, Kannewurfconducting polymers. 1. polyion complexes and their multi-CR, Bakas T et al. Reaction of aniline with FeOCl. formationlayer heterostructures. Langmuir 1992;8(12):3168–77.and ordering conducting polyaniline in a crystalline layered

host. J Am Chem Soc 1995;117(36):9229–42. [11] Higashika S, Kimura K, Matsuo Y, Sugie Y. Synthesis ofpolyaniline-intercalated graphite oxide. Carbon[7] Leroux F, Goward G, Power WP, Nazar LF. Electrochemical1999;37(2):354–6.Li insertion into conductive polymer /V O nanocomposites.2 5

[12] Liu P, Gong K. Synthesis of polyaniline-intercalated graphiteJ Electrochem Soc 1997;114(11):3886–95.oxide by an in situ oxidation polymerization reaction.[8] Dabke RB, Dhanabalan A, Major S, Talwar SS, Lai R,Carbon 1999;37(4):706–7.Contractor AO. Thin Solid Films 1998;335:203.

[13] Asturias GE, MacDiarmid AG, McCall RP, Epstein AJ. The[9] Nicolae CA, Cantin-Riviere S, El Abed A, Peretti P. Study ofoxidation of ‘emeraldine’ base. Synth Met 1989;29(1):E157–mixed enzyme/pyrrole derivative Langmuir-Blodgett films62.for biosensing application. Langmuir 1997;13(20):5507–10.

Adsorption of chlorinated hydrocarbons from air and aqueoussolutions by carbonized rice husk

*A. Imagawa, R. Seto, Y. NagaosaDepartment of Applied Chemistry and Biotechnology, Faculty of Engineering, Fukui University, Bunkyo, Fukui 910-8507, Japan

Received 4 June 1999; accepted 24 November 1999

Keywords: A. Carbon precursor; B. Carbonization; C. Adsorption; D. Adsorption properties

Tetrachloroethylene (PCE), trichloroethylene (TEC) and that the adsorbent has a property of strong adsorption and1,1,1,-trichloroethane (TCA) present in the aquatic en- easy desorption of the organics on heating.vironment (drinking and river waters) come from different Rice husk and other waste materials were collected fromsources, such as the manufacture of electrical devices, rice farms and were dried in sunlight. The rice husk wasmechanical parts, dyes, cleaning agents etc. The chlori- heated to 4008C for 3 h in the atmosphere. The carbonized

2nated hydrocarbons have been known to cause damage to material had a BET surface area of 44 m /g. A particlethe nervous system, liver and kidney of the human body size of 250–500 mm was used. For comparison, we also

2and cancers [1]. Due to their toxicity, the Japanese used granular activated carbon (384 m /g BET surfaceMinistry of the Environment has regulated that the toler- area, coal-based) from Wako Pure Chemicals. A Gastechance limits for PCE, TEC and TCA are 0.01 mg/ l, 0.03 Model GV-100 gas sampler was used to put 100 ml of amg/ l and 1 mg/ l for the environmental level, respectively gas sample into a detecting tube manufactured by Gastech[2]. Treatment methods to remove the organic compounds Co. Ltd. An Iwaki Model mechanical shaker was used tofrom the wastes are therefore necessary to protect the agitate the carbonized rice husk and the organic sample.diffusion and pollution into the environment. Many papers Batch mode adsorption experiments (gas phase) werehave been published for the effective removal of chemical carried out with 5.0 g of adsorbent and 5.0 l of thecompounds from air and aqueous solutions using activated chlorinated hydrocarbon of a desired concentration (200carbons [3,4]. Coal- and wood-based activated carbons ppm) in 5.0-l Tedlar bags at room temperature and werehave been prepared using various activation processes with agitated each 2 min. The gas samples (100 ml) were takenheat treatments [5,6]. The main purpose of this study is to for the determination of the organics with detecting tubesinvestigate the feasibility of using carbonized rice husk, an at predetermined time intervals. In the aqueous phaseagricultural by-product, for the removal of the chlorinated system, 1.0 g of adsorbent and 40 ml of an aqueoushydrocarbons from air and water by adsorption. It is shown solution containing the test organic were placed into a

100-ml stoppered flask. After equilibrium, 5.0 ml of theaqueous sample were taken in a 300-ml stoppered flaskand were heated at 808C for 10 min for determinations.*Corresponding author. Fax: 181-776-278-747.The determination of the organics was performed by theE-mail address: nagaosa@acbio.acbio.fukui-u.ac.jp (Y. Naga-detecting tube method.osa)

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