Fast ethylamine gas sensing based on intermolecular charge-transfer complexation

Availableonlineatwww.sciencedirect.comCHINESESciVerse scienceDirectCHEMICALLETTERSELSEVIERChinese Chemical Letters 23(2012)484-487www.elseviercom/locate/ccletFast ethylamine gas sensing based on intermolecularcharge-transfer complexationEun Mi Lee, Seon Young Gwon, Young A Son, Sung Hoon Kim .c,BK2/ FTIT, Department of Advanced Organic Materials and Textile System Engineering, Chungnam National UniversiryDaejeon 305-764, Republic of KoreaDepartment of Textile System Engineering, Kyungpook National University, Daegu 702-70/ Republic of KoreaSchool of Chemistry Science& Technology, Zhanjiang Normal University Zhanjiang 524048, ChinaReceived 12 October 2011abstractWe have investigated the fast ethylamine gas sensing of 2-chloro-3, 5-dinitrobenzotrifluoride( CDBF) loaded poly(acryloni-rile)nanofiber based on an intermolecular charge-transfer complexation. Reversible response and recovery were achieved usingalternating gas exposure. This system shows a fast ethylamine gas sensing within 0.4 S.2012 Sung Hoon Kim. Published by Elsevier B V. on behalf of Chinese Chemical Society. All rights reservedKeywords: Ethylamine gas: Fast gas sensing: 2-Chloro-3, 5-dinitrobenzotrifluoride(CDBF; Electrospinning: PAN nanofiber; Intermolecularcharge-transfer(CT) complexationGas detection and determining their composition are a crucial point for volatile organic compounds(vOCs)monitoring, industry, and domestic purpose. There has been an intensive interest in developing high sensitivity, rapidresponse and recovery, and selective gas detection. Most studies have been shown to exhibit high sensitivity forsensing gas molecules such as CO2, CO, SO2, O2, O3, N2, NO2, H2O, NH,, and some organic vapors [1-3]. A widerange of amines are pollutants in industrial and manufacturing areas because they are extensively used in thepreparation of fertilizer, herbicides, pharmaceuticals, surfactants, rubber latex, biological buffer substances andcolorants. Turner et al. investigated the ability of a hemithioacetal-based polymer to react with primary amines and toform a fluorescent isoindole complex [4]. Chemosensing methods are widely used for the detection of amines, but theirlow selectivity and sensitivity toward different types of amines make them impractical [5]. Among various types ofamines, ethylamine is a colorless, flammable liquid and an ammonia-like odor. It has an air odor thresholdconcentration of 0.95 ppm of air. Inhalation exposure to ethylamine may cause eye imitation, tearing, conjunctivitis,and comeal edema. Qiu et al. worked with a supramolecular metal-organic framework(MOF)constructed by two-dimensional) infinite coordination polymers, (Zn(1, 4benzenedicarboxyate)(H2O)Im, and they evaluated thefluorescence response of the MOF nanosheets in the presence of ethylamine solution [6]. In this paper, we reporton the fast ethylamine gas sensing based on intermolecular charge-transfer(CT)complexation. A number of methods4 Coresponding author.E-mail address: shoki@@knu ack(S H. Kim).1001-8417/s-see front matter 2012 Sung Hoon Kim. Published by Elsevier B V. on behalf of Chinese Chemical Society. All rights reserved.doi:l0.06/clet20201020中国煤化工CNMHGE.M. Lee et al. /Chinese Chemical Letters 23(2012)484-487have been investigated to detect gases using metal oxides(response time is 20 s for CH4 [71), metal nanoparticles(10-20 s for O2 [81, 2 s for H2 [91), organic polymers(15-27 s for humidity [10], 100 s for C2HSOH [111), unfunctionalizedCNTs(10 min for NO2[ 12D, CNT-polymer(100 s for tetrahydrofuran [ 13]), and CNT-metal nanoparticles(20 minfor CH4 [14], 9 min for NO2 [15])[16]. It takes relatively a long time to reach equilibrium for the sensing of analytesfrom gas phase onto the surface of the sensor device. To the best knowledge of the authors, this is the first report tostudy the fast response and recovery of gas sensing within 0.4 s Chromogenic chemodosimeters are popular due totheir capability for 'naked eye' detection without resorting to any expensive instruments. To develop simple and nakedeye sensing tools, a great effort has recently been made for the design and synthesis of selective chemosensors. Herewe report on the naked eye sensing of ethylamine gas based on n- intermolecular CT interaction using 2-chloro-3, 5-dinitrobenzotrifluoride(CDBF) as an acceptor. It is well known that the absorption spectra of intramolecular CTcomplexes are affected by a donor and/or an acceptor natureDuring the complex formation, charge transfer transitions occur with the excitation of an electron from donormolecule to a vacant orbital of acceptor molecule. Charge transition involves an electron transfer from HOMO ofdonor to LUMO of the acceptor. The interaction of p-chloranil with amines and amino acids has been reported by liuet al.[17]. We have also demonstrated the colorimetric signaling of mono-, di-, and triethylamine basedintermolecular CT interaction [18]. The formation of the n-I CT complex and spectra were showed in their studyCDBF is used as an acceptor to sensing ethylamine molecule by the n-T CT interaction between electron richethylamine donor and electron deficient CDBF acceptor. The electron transfer from ethylamine to CDBF leads to theformation of an n-T CT complex, as illustrated in Fig. 1Fig. I shows the changes in absorption spectra of dimethyl sulfoxide(DMsO) solution upon addition of theethylamine; as the ethylamine concentration increases, the absorption intensity of CT complex increase. A red colorwas obtained on interaction of the CDBF acceptor colorless solution and ethylamine in DMSO mentioned a CTformation. The maxima of the most intensive transitions in the absorption spectra are around 398 and 503 nm forethylamine-CDBF CT complex. The first and the second Ct bands are considered to be due to the Ct from the HOMOand NHOMO levels of the donor, respectively, to the LUMO level of the acceptor [19]The local orbital density function(DF) method, DMol optimized geometry of CDBF-ethylamine CT complex isdepicted in Fig. 2(B), where the important distances between donor and acceptor molecules are also shown. Benzenepart of the CDBF approaches to ethy lamine within an inter-atomic Van der Waals distance of 2.7 AElectrospinning is a well-known and convenient technique for generating ultrathin nanofiber materials, withdiameters in fabrica the polymer solution for electrospinning is injected from a small nozzle under the influencege of nanometers to several micrometers [20, 21]. The electrospinning technique allows for rapidand cost-effectiveation of fibrous polymer membranes with great length and high specific surface area. In theprocess of electrospinning.of an electric field and electrospun fibers are collected on the grounded collector screen. Thus, we felt that acombination of the CT complexing properties between CDBF and ethylamine gas and the interesting properties ofelectrospun nanofibers. A typical procedure used for the fabrication of electrospunnanofiber is schematicallypresented in Fig. 2(C). CDBf has good solubility in poly (acrylonitrile)(PAN, Mw=150,000)andethylamineNoFacCT complO2NCDBFFig. I.(A)Schematic illustration for the formation of the CT complex between CDBF and ethylamine.( B)Photograph of (a)0. I mmol/L only CDBFsolution,(b)ethylamine donor-CDBF acceptor complex solution(0.1 mmol/L)中国煤化工CNMHGE.M. Lee et al./Chinese Chemical Letters 23(2012)484-487High Voltage Power Supply1.0PANso1P-ENwN-H complexOINFig. 2.(A) Absorption spectra of CT complex as a function of [ethylamine] in DMSO. (B)DMoloptimized geometry of CT complex. The distancesare given in A units. (C)schematic representation of the preparation and ethylamine gas sensing of CDBF loaded PAN nanofiber.N, N-dimethylformamide(DMF). Therefore, PAN was selected as a promising matrix for the preparation ofelectrospunnanofiber. A viscous DMF solution containing PAN and CDBf is placed in a syringe. A high voltage(20 kV)is then applied to the syringe needle. The nanofibers are collected on the surface of a grounded aluminum foilDetailed electrospinning process is provided in Supporting information(Si)Fig 3 shows a span of 0. 2 s still images in which PAN nanofiber containing CDBF have been exposed to 0.1%ethylamine gas for 0.8 s. These still images were selected from video clip. (Supporting information, video cameraVIXIA HFM 31 Canon, Japan) Upon exposing PAN nanofiber mat to ethylamine gas, a red color was promptlyappeared and color intensity increased, depending on the exposing time(Figs. 2(C)and 3). After removal of theethylamine gas stimuli, the original pattern is reversibly recovered within 0.4 s. This coloration is ascribable to thegeneration of the intermolecular CT complex between CDBF acceptor and ethylamine donor. We can judge fromFig 3 that the fast color changing response exhibits an excellent response and recovery characteristic(please contactthe corresponding author directly for a copy of the video clip if required)In summary, we have investigated the fast ethylamine gas sensing of 2-chloro-3, 5-dinitrobenzotrifluoride(CDBF)oaded poly(acrylonitrile)nanofiber based on an intermolecular charge-transfer complexation. The presentethylamine gas sensing system operates at room temperature and shows fast color changes in the n-I CTinteractionwithin 0.4 smore than 1000 timesEtNH2 gas ON-EtNH, gas OFFFig. 3. Still images of fast and reproducible responses of PAN nanofiber mat upon expogas as a function of time中国煤化工CNMHGE.M. Lee et al. /Chinese Chemical Letters 23(2012)484487AcknowledgmentsThis work was supported by Basic Science Research Program through the National Research Foundation(NRF)grant funded by the Korea Government(MEST)(No 2011-0001084). This research was supported by a grant from theFundamental R&D Program for Core Technology of Materials funded by the Ministry of Knowledge Economy,Republic of KoreaAppendix A. Supplementary dataSupplementary data associated with this article can be found, in the online version at doi: 10. 1016/j cclet.2012.01.020.References[1] J.Z. Wang, x. Chen, M.Q. Li, et al. Chin J. Chem. 26(2008)649[2]C w. Yu, S.H. Li, H. Zheng, J.G. Xu, Chin J. Chem. 25(2007)797.[3] Y.F. Ding. G.P. Jin, J.G. Yin, Chin J. Chem. 25(2007)109[41 S. Subrahmanyam, S.A. Piletsky, E.V. Piletska, et al. Acta Mater. 12(2000)722[5](a)S.Reinert, G.J. Mohr, Chem. Commun. 19(2008)2272(b)J H. Jung. S.J. Lee, J.S.Kim, et al. Org. Lett. 8(2006)3009:(c)K. Takahiro, U Shinichi, I. Yuka, et al. J. Am. Chem. Soc. 111(1989)1881:(d)F. Kaoru, T. Kazunin. T Kiyoshi, et al. J. Am. Chem. Soc. 121(1999)3807[6] Z.Q. Li, L.G. Qiu, W. Wang, et al. Inorg. Chem. Commun. 11(2008)1375[7]SJ Hong. J. 1. Han Sens. Actuators A 112(2004)80[8]T. 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