Sensors and Actuators B 163 (2012) 107–114
Contents lists available at SciVerse ScienceDirect
Sensors and Actuators B:
Chemical
j o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /s n
b
Gas sensor based on p-phenylenediamine reduced graphene oxide
Nantao Hu a ,Yanyan Wang b ,?,Jing Chai a ,Rungang Gao a ,Zhi Yang a ,Eric Siu-Wai Kong a ,Yafei Zhang a
a
Key Laboratory for Thin Film and Microfabrication of the Ministry of Education,Research Institute of Micro/Nanometer Science &Technology,Shanghai Jiao Tong University,Shanghai 200240,PR China b
Institute of Information Optical Engineering,Soochow University,Suzhou 215006,PR China
a r t i c l e
i n f o
Article history:
Received 19August 2011
Received in revised form 4January 2012Accepted 5January 2012
Available online 25 January 2012
Keywords:Graphene
p-Phenylenediamine Drop drying DMMP Gas sensor
a b s t r a c t
We present a useful gas sensor based on chemically reduced graphene oxide (CRG)by drop drying method to create conductive networks between interdigitated electrode arrays.CRG,which is formed from the reduction of graphene oxide by p-phenylenediamine (PPD),can be used as an excellent sensing mate-rial.Its ef?cient dispersion in organic solvents (i.e.,ethanol)bene?ts the formation of conductive circuits between electrode arrays through drop drying method.Preliminary results,which have been presented on the detection of dimethyl methylphosphonate (DMMP)using this simple and scalable fabrication method for practical devices,suggest that PPD reduced CRG exhibits much better (5.7times with the concentration of DMMP at 30ppm)response to DMMP than that of CRG reduced from hydrazine.Fur-thermore,this novel gas sensor based on CRG reduced from PPD shows excellent responsive repeatability to DMMP.Overall,the ef?cient dispersibility of CRG reduced from PPD in organic solvents facilitates the device fabrication through drop drying method,the resultant CRG-based sensing devices,with miniature,low cost,portable characteristics,as well as outstanding sensing performances,can ensure its potential application in gas sensing ?elds.
? 2012 Elsevier B.V. All rights reserved.
1.Introduction
With the development of sensing technology in many ?elds,including environment monitoring,industry and agriculture pro-duction,medical diagnosis,military and public safety,etc.,chemiresistive sensors play more and more important roles,due to their low power consumption and the ease of high precision resistance measurements [1–5].Many sensing materials,including semi-conducting metal oxide [6],organic semiconductors [7],car-bon nanotubes (CNTs)[8],etc.,have been used for chemiresistive sensors and exhibit great potential for gas sensing applications.As a nanometer-thick two-dimensional analog of CNTs,graphene has emerged as another promising candidate for sens-ing,owing to its exceptional electronic,mechanical,chemical,and thermal properties [9–15].Similar with CNTs,the high fraction of surface atoms in graphene makes this carbon nanosheet an ideal candidate for sensing applications.Since Novoselov et al.[16]?rstly demonstrated the gas sensing potential of graphene through exposure of the devices to water,ethanol vapors,or ammonia gas,many research papers focused on this topic emerged [17–20].It has been demonstrated that excellent sensing performance of graphene toward NO 2,NH 3,H 2O,CO,trimethylamine,I 2,ethanol,
?Corresponding authors.
E-mail addresses:hunantao@https://www.doczj.com/doc/b016023044.html, (N.Hu),yywang@https://www.doczj.com/doc/b016023044.html, (Y.Wang),yfzhang@https://www.doczj.com/doc/b016023044.html, (Y.Zhang).
HCN,dimethyl methylphosphonate (DMMP),DNT,etc.,could be achieved [17–22].Several methods,including micromechanical exfoliation of graphite [16],chemical vapor deposition [23],and solution-based chemical reduction of graphene oxide (GO)[24],have been developed to prepare graphene nanosheets and hold great potential for gas sensing applications.Among,chemically reduced graphene oxide (CRG),which is synthesized by the chem-ical reduction of GO,has been aroused much attention for using as chemiresistors [25–29],due to its scalable production,solution processibility,large available surface area,etc.Chemical reduc-tion of GO by hydrazine has been successfully achieved through elimination of oxygen-containing groups,and the resultant CRG exhibits a substantially rapid electrical response to many gases or vapors [18,25].Ruoff group [30]has reported an all-organic vapor sensor based on CRG,which is synthesized by the reduction of GO using ascorbic acid as a mild and green reducing agent.The resultant rugged and ?exible sensor using inkjet-printed ?lms of CRG on poly(ethylene terephthalate)can reversibly detect NO 2and Cl 2vapors in air at ppb level.Although many reports have been reported on the sensing properties of CRG,it is still a great chal-lenge to develop the sensing devices based on CRG with miniature,low cost and portable characteristics.
Herein,we have reported for the ?rst time that CRG reduced from p-phenylenediamine (PPD)could be used as an excellent sensing material.Sensing devices can be easily fabricated through using drop drying method to create conductive CRG networks between interdigitated electrode arrays.The DMMP gas sensing
0925-4005/$–see front matter ? 2012 Elsevier B.V. All rights reserved.doi:10.1016/j.snb.2012.01.016
108N.Hu et al./Sensors and Actuators B163 (2012) 107–114
performance of the resultant sensing device is much better than that of the devices based on CRG reduced from hydrazine fabricated via drop drying method.We expect the easy,green and scalable fab-rication of the sensors based on CRG reduced by PPD,with excellent performance,miniature,low cost and portable characteristics,can pave a new avenue for the application of CRG in gas sensing?eld.
2.Experimental
2.1.Materials
The natural graphite(500meshes)used in this study was obtained from Shandong Tianyuan Co.Ltd in China.DMMP(97%) was purchased from Sigma–Aldrich and used as received.All of other chemicals(analytical reagent grade)were purchased from Shanghai Chemical Reagents Co.Ltd.(China)and were used with-out further puri?cation.All of organic solvents were puri?ed by distillation.
2.2.Preparation of graphene oxide(GO)
Modi?ed Hummers method was exploited here to prepare GO. The typical procedure was as follows,graphite(1g,500meshes) and concentrated sulfuric acid(25mL)were added into a250mL of ?ask,and vigorous stirring was executed.Then1.25g of NaNO3was added.After keeping stirring for1h,the mixture was cooled to0?C using an ice-water bath.3.7g of KMnO4was added in small portions during2h.Followed by increasing the temperature to35?C,the reaction was allowed to take place for another2h.Subsequently, the reaction was quenched by adding0.1L of ice water and3.5mL of H2O2(30%).The resultant GO was?ltered,and washed with plenty of aqueous HCl(3%)until no precipitation of BaSO4occurred in the presence of aqueous BaCl2solution.Further washing with water was carried out until the chloride test with AgNO3was neg-ative,and the resultant products were dried at40?C for24h in the vacuum oven.
2.3.Preparation of chemically reduced graphene oxide(CRG)
The CRG reduced from PPD was obtained by the method reported by Chen et al.[31].Typically,75mg of GO was dispersed in75mL of water through ultrasonication for1h at room temper-ature,and PPD(680mg)dissolved in ethanol(75mL)was added. The mixture was allowed to be sonicated for another10min,and the reaction took place by re?uxing the mixture in a water bath at90?C for24h.After cooling down the temperature,the black suspensions were?ltered,washed with water and acetone several times.The resultant black powder,noted as CRG,was transferred into ethanol,followed by mild ultrasonication,and consequently, stable graphene colloids in ethanol with different concentrations (1mg/mL and0.025mg/mL)were formed.The CRG powder was also obtained by drying the puri?ed CRG in the vacuum oven at 80?C overnight.
For the purpose of the comparison,the CRG reduced by hydrazine,noted as CRG-2,was also prepared according to the Refs.[32,33].A typical process was as follows,90?L of ammonium hydroxide(32%)and7.2?L hydrazine hydrate were added to10mL of the suspension of the GO(1mg/mL).Reduction was carried out by stirring the mixture at100?C for1h.The resulting stable black suspension was diluted40times with water for further use.
2.4.Fabrication of sensing devices based on CRG
The standard microfabrication procedures,which have been illustrated by us before[34–37],were exploited here in order to obtain the electrodes for the sensors array.The interdigitated elec-trode?ngers were formed by sputtering10nm Cr and180nm Au onto a patterned photoresist mold.A lift-off process was further carried out to remove the photoresist.The resultant electrodes were sonicated in ethanol,washed with deionized water thor-oughly and?nally dried by nitrogen?ow.
In order to fabricate the sensing devices based on CRG,the typi-cal protocols have been designed as follows:0.1?L of CRG ethanol suspension(0.025mg/mL)was extracted and deposited onto the electrode gap using a microsyringe.After evaporation of the solu-tion through putting the devices in the vacuum oven at80?C for1h, networks of CRG bridged each electrode gap could be formed.The sensing devices based on CRG-2could be also fabricated according to the method mentioned above.
2.5.Characterization
Fourier transform infrared(FT-IR)spectra were recorded on a Bruker(Germany)VERTEX70spectrometer(KBr pellets)over a range from400to4000cm?1with DTGS or MCT as detector.Raman scattering was performed on a Renishaw inVia Re?ex Raman spec-trometer using a514-nm laser source.The thermogravimetric analysis(TGA)was performed under a nitrogen atmosphere using a heating rate of10?C/min started from50?C up to600?C.To avoid the thermal expansion of the GO due to rapid heating,GO samples were also heated from50?C to600?C at1?C/min.The mor-phologies of the samples were observed by?eld emission scanning electron microscopy(FE-SEM,Carl Zeiss Ultra55).Transmission electron microscopy(TEM)was obtained on JEM-2100(Japan),and the accelerating voltage was200kV.
A homemade gas handling system,which can generate and deliver DMMP vapor as illustrated in our previous reports[34–37], is used to evaluate the sensing properties of the sensors.Dry air,as both of the carrier and of the diluting gas,was used to bubble DMMP liquid through a porous glass-disc bubbler,in order to obtain DMMP vapor.The concentration of DMMP vapor can be easily controlled by dilution with dry air using mass?ow controllers.The humidity inside the test chamber was monitored by a Honeywell HIH-4000 humidity sensor(Honeywell Inc.)and is less than20%.All gas sens-ing tests were carried out at room temperature(25?C).The?ow rate of the balance gas(dry air)was controlled to be at1L min?1.The resistance variation during testing was monitored using a precision semiconductor parameter analyzer(Agilent4156C).The sensor response was evaluated by the resistance change at a sampling voltage of50mV.
3.Results and discussion
3.1.Synthesis and characterization of CRG
Modi?ed Hummers method was executed to oxidize graphite, and consequently,a stable yellow-brown aqueous solution of GO (as shown in Fig.1(a))was formed.During the reduction process of GO,PPD was used as a green reducing agent as well as an excellent stabilizer,the resultant CRG(without drying)can be ef?ciently dis-persed in ethanol.As shown in Fig.1(b),the homogenous colloid suspension of CRG in ethanol with the concentration at1mg/mL can be formed.After diluting with ethanol,the colloid with a brown color was formed(as shown in Fig.1(c)),no precipitates can be observed,even after several weeks.This is fascinating,since the process is very easy and green,which can also bene?t further fab-rication of sensing devices through solution operations.
The FT-IR spectroscopy was utilized to con?rm the process for the preparation of CRG.Fig.2(a)illustrates the typical spectra of the natural graphite.As shown in Fig.2(a),a broad peak located
N.Hu et al./Sensors and Actuators B163 (2012) 107–114
109
Fig.1.Photograph of(a)GO aqueous solution(1mg/mL);(b)and(c)CRG disper-sions in ethanol(1mg/mL and0.025mg/mL,respectively).(For interpretation of the references to color in the text,the reader is referred to the web version of this article.)
at3504cm?1,which corresponded to the absorbed water,can be observed;a weak peak appeared at1636cm?1was attributed to the C C stretching vibration band of graphite[38–40].After oxidized by modi?ed Hummers method,the resultant GO was also charac-terized by FT-IR as shown in Fig.2(b).The spectrum of GO illustrates O H( (carboxyl)at～1412cm?1,while the band at ca.3432cm?1 could be due to the O H stretching mode of intercalated water.
C O( (epoxy or alkoxy))at～1231cm?1,C O in carboxylic acid (～1636cm?1)and carbonyl moieties( (carbonyl)at1737cm?1, suggested that the oxidation of graphite by modi?ed Hummers method took place and the formation of GO achieved successfully. After the reduction of GO,the band appeared at3432cm?1shifted to3446cm?1,which could be assigned to the N H stretching mode of oxidized PP
D or decomposition products of hydrazine,or O H stretching mode of intercalated water(Fig.2(c)and(d)).Further-more,the C O vibration band located at1737cm?1,together with the C O stretching bands located at1231cm?1,had been disap-peared,suggesting the CRG and CRG-2had been formed by using PPD and hydrazine as reducing agents.
Raman spectroscopy is a powerful nondestructive tool to dis-tinguish ordered and disordered crystal structure of carbon.Fig.3 exhibits the Raman spectra of(a)graphite,(b)GO and(c)CRG.All of spectra contained the following characteristic peaks:the D band located at1340–1360cm?1(disorder mode),which was a breathing mode of?-point phonons of A1g symmetry;and G band centered at1570–1590cm?1(tangential mode),assigned to the E2g phonon
of C sp2atoms.As shown in Fig.3(a),the spectrum of the
natural
Fig.2.FT-IR spectra of(a)graphite;(b)GO;(c)CRG;and(d)
CRG-2.
Fig.3.Raman spectra of(a)graphite;(b)GO and(c)CRG with the excitation wave-
length at514nm.
graphite displayed a strong G band at1579cm?1,and a weak D
band at1351cm?1.As to GO(Fig.3(b)),the D band and G band
widened and shifted to1345cm?1and1588cm?1,respectively,
and the relative intensity of D band increased substantially,indi-
cating the decrease in size of the in-plane sp2domains,which was
possibly due to the extensive oxidation and ultrasonic exfoliation
[41,42].When the GO was chemically reduced,the D band and G
band shifted to1342cm?1and1583cm?1,respectively,and fur-
ther increase of the relative intensity of the D band occurred,i.e.,
an increase of D/G intensity ratio of graphene compared to that
of the GO could be observed(Fig.3(c)).This changes suggested
an increase in the average size of the sp2domains upon reduc-
tion of GO,which agrees well with the Raman spectrum of the GO
reduced by hydrazine reported by Stankovich et al.[41],indicat-
ing the reduction did happen.In addition,the size of the crystalline
domains in within the CRG?akes could be estimated from the D/G
intensity ratio and the excitation wavelength of the Raman spec-
tra[32,42].According to the Ref.[42],the crystalline size can be
determined by the following equation:
L a(nm)=(2.4×10?10) 4
laser
I D
I G
?1
(1)
where L a is the size of the crystalline domains in within CRG, laser is
the excitation wavelength of the Raman spectra,and I D/I G is the D/G
intensity ratio.A D/G ratio of1.09and the excitation wavelength at
514nm for CRG in our work(Fig.3(c)),suggested that crystalline
domains with the size at ca.15nm had been formed in within the
resultant CRG?akes.
TGA analysis has also been carried out in order to investigate the thermal decomposition as increase of calcinations tempera-
ture in an inert atmosphere.Fig.4exhibits the TGA curves of
(a)
Fig.4.TGA curves of(a)graphite;(b)GO and(c)CRG heated in a nitrogen atmo-
sphere.
110N.Hu et al./Sensors and Actuators B 163 (2012) 107–
114
Fig.5.SEM images of (a)graphite,(b)GO and (c)CRG;and TEM image of (d)CRG.
graphite,(b)GO and (c)CRG under nitrogen atmosphere.As shown in Fig.4(a),the natural graphite is quite stable below 600?C,no obvious changes of weight loss can be observed.The decomposi-tion of GO (Fig.4(b))begins at 200?C and about 55%of weight loss occurs at 600?C (due to the loss of the acidic functional groups and residues).As far as CRG is concerned,18%of weight loss at 600?C has occurred (as shown in Fig.4(c)),which suggests that the enhancement of thermal stability achieved after the oxygen-containing functional groups had been removed during reduction.
As SEM and TEM provide suf?cient resolution that they can be used to obtain some direct visualization of the size distribution,it is necessary to clarify the morphology of CRG by TEM and SEM.Fig.5(a)–(c)depicts the morphology variation during the process of CRG preparation.The natural graphite (as shown in Fig.5(a))with several decades of micrometers in size,exhibits a plate-like struc-ture.After oxidization,the size of the resultant GO sheets decreases rapidly,which is due to the strong oxidation attacking and ultra-sonic destruction [41].Further decrease of the size happens after the reduction of GO sheets.The size of the resultant CRG sheets is less than 5?m,which is suitable for the gas sensing device fabri-cation with the electrode gap larger than 5?m.TEM has also been carried out in order to observe the morphology of CRG (as shown in Fig.5(d)).We can see that the ?ake CRG has been obtained,and the edge of the sheet slightly curved.
3.2.Evaluation of sensing device based on CRG
Gas sensors based on the resultant CRG was fabricated through depositing CRG on the electrode by drop drying method.The elec-trode arrays (as shown in Fig.6(a)),with the size ?xed at 10?m (larger than the size of the resultant CRG),were fabricated.A 0.1?L drop of CRG in ethanol (the concentration was ?xed at 25?g mL ?1)was used here to dip on the electrodes,and then dried.The membrane of CRG sheets with some ridges formed between the electrodes (as shown in Fig.6(b)),suggesting that network struc-ture of CRG sheets was formed.As a result,the sensing device with the diameter less than 2cm was easily fabricated (as shown in Fig.6(c)).The resistance of the resultant sensing device was mea-sured by applying 50mV of voltage,and a value of 1.5M suggested that a perfect circuit of the sensing device had been achieved.
In order to demonstrate the potential utility and probe the sens-ing properties of the resultant CRG based sensors,DMMP was used here as analyte.The sensors were tested toward different con-centrations of DMMP vapor balanced in synthetic air.The sensor response (R )toward DMMP vapor was calculated according to the following equation:
R (%)=100×
R R 0
=100×
R
gas
?R 0R 0
(2)
where R 0is the resistance of CRG membrane before the exposure to DMMP vapors and R gas is the resistance of CRG membrane in the DMMP/air mixed gas [36].
The sensory response of the fabricated devices toward DMMP vapor is investigated according to a conductance measurement between the two electrodes at a low sampling voltage (50mV).Fig.7displays the dynamic response of the resultant CRG based sensing devices toward DMMP vapor under the concentration of 80ppm.We can observe that the resistance of the device increases signi?cantly when the DMMP vapor was introduced into the cham-ber.Moreover,the resistance changes become smaller and smaller with the exposure time.However,we have not observed the sat-urated state of the CRG based sensing device,even when the exposure time was prolonged to 8000s.It is suggested that the resultant CRG based sensing device exposed to DMMP vapor is very dif?cult to be saturated,this maybe due to the following rea-sons:(1)the intrinsic properties of carbon atoms,which is similar with CNTs [34];(2)the stacked structure of graphene nanosheets,which prevents the DMMP gas molecules rapidly penetrating into the inside of the membranes.Despite of this,the signi?cant increase of the resistance during the preliminary period of the exposure time (less than 18min)can ensure the practical application of the sens-ing devices.Thus,we de?ne the exposure time of about 18min as the effective response time,and the responses of the sensing devices to different concentrations of DMMP vapor (5–80ppm)over a period of 18min have been further studied (as shown in Fig.8(a)).The results reveal that the sensing devices exhibit an excellent and highly reversible response to different concentra-tions of DMMP vapors.When the DMMP vapor was introduced into the chamber,the resistance of the sensing device increased signi?cantly over a period of 18min.Furthermore,the increase of
N.Hu et al./Sensors and Actuators B163 (2012) 107–114
111
Fig.6.SEM images of(a)electrode array and(b)CRG membrane formed between electrodes;(c)photograph of the resultant sensing device. the concentration of DMMP vapor can result in the increase of the
resistance of the device.And all of the resistance variations can be
distinctly observed when the devices expose to the DMMP vapors
with the concentration ranging from5ppm to80ppm.When the
concentration of DMMP vapor is?xed at80ppm,ca.14.5%of the
resistance change can be observed.As the decrease of the con-
centration of DMMP vapor,the resistance change of the device
decreases accordingly.And ca.5.0%of the resistance change can
be also observed when the concentration of DMMP vapor was as
low as5ppm.Further probing the sensing properties of the CRG
sensor in lower concentration(ppb levels)of DMMP has not been
executed here due to the limited capability of the testing system.In
order to evaluate the sensing performance of CRG sensor,the com-
parison has also been made between CRG sensor and other DMMP
sensors(Table1).As shown in Table1,CRG sensors fabricated in our
work exhibit comparable response ability with CNTs based sensors,
especially when the same deposition method(drop drying method)
is exploited.
Furthermore,the sensor response exhibits an excellent recov-
ery characteristic(as shown in Fig.8(a)).As illuminated with IR
lamp together with?ushing with dry air over a period of6min,the
resistance decreased and essentially recovered to the initial
values.
Fig.7.The response curve of the CRG sensor to DMMP vapor under the concentra-tion of80ppm.Since the CRG sensors can be easily recovered,long-term practical work of the devices can be promised.
In addition,the sensor displays a linear response to differ-ent concentrations(ranging from5ppm to80ppm)of DMMP(as shown in Fig.8(b)),which is similar with other CRG based
sensors Fig.8.(a)The response curve of the CRG sensor to DMMP vapor under the concen-trations of5–80ppm and(b)relationship of the response of the sensors with the concentrations of DMMP.
112N.Hu et al./Sensors and Actuators B163 (2012) 107–114
Table1
The comparison of the sensing performance between CRG sensor and other sensors for the detection of DMMP vapor.
DMMP sensing materials Deposition method Response time(s)R to20ppm DMMP(%)Recovery time(s)Reference CRG Dip-dropping10808360–
SnO2Precipitation500>80–[43]
6FBPA modi?ed CNTs Dip-dropping960 5.1720[37] Polymer-modi?ed CNTs Dip-dropping1200<5600[44] reported before[27,30,45].Judging from the slope of the linear?t
of the calculation curve data in Fig.8(b),a magnitude of response
of0.122±0.008ppm?1can be obtained.The correlation coef?cient
of0.995suggests that the CRG based sensors exhibit an excellent
linearity of response to DMMP vapors,which is advantageous for
its practical applications in the gas sensing?eld.
It is suggested that the excellent sensing properties of CRG based
sensors are governed by the intrinsic properties of https://www.doczj.com/doc/b016023044.html,ually,
CRG,which is prepared by the reduction of GO through eliminat-
ing many of oxygen-containing functional groups and restoring
the original properties of the sheets,still contains oxygen-based
moieties and structure defects[9].Therefore,it is not the same as
pristine graphene[46,47].The existing oxygen-based moieties and
structure defects,which are electron-withdrawing and promote
holes in the valence band of CRG,lead to the p-type semiconducting
behavior of the resultant CRG[25,48],and play important roles in
the sensing properties of the resultant CRG.As we know,DMMP is
a strong electron donor[36],as it gets close to the CRG,depletion of
holes from the valence band of CRG occurs,resulting in the increase
of the resistance of the CRG networks(as shown in Fig.8(a)).
The repeatability of the gas sensor has also been studied,as
shown in Fig.9,?ve cycles of responses to DMMP vapors has been
executed through exposure of the CRG based sensor to20ppm
DMMP vapor repeatedly.We found that the response levels of the
sensor are maintained after repeated cycles of exposure to DMMP
and recovery,which suggested that the CRG based gas sensor exhib-
ited a high repeatability characteristic.Actually,the performance
of the gas sensor based on CRG is very stable for a long period time
under normal operating conditions.Even after several months,the
sensing device still shows excellent sensing performance.There-
fore,it is suggested that CRG(reduced from PPD)can be considered
as excellent sensing materials and have potential applications in the
sensing areas.
Since the selectivity is another key factor for the evaluation
of a gas sensor,it is essential to study the selectivity properties
of the CRG sensor.Different analytes, e.g.,DMMP,methanol,
dichloromethane,hexane,chloroform,and xylene,have
been
Fig.9.Reproducibility of the response of CRG sensors to20ppm DMMP vapor.studied.The saturated concentration of vapors were produced at room temperature and diluted with dry air to5%concentrations. As shown in Fig.10,more than three times magnitude of response to DMMP vapors for the CRG sensor can be observed in comparison with other analytes.The result suggests that the CRG sensors exhibit a high selectivity and can be considered as an excellent candidate for the detection of DMMP.
Furthermore,the in?uences of the relative humidity(RH)on the resistance response of the CRG based sensor were investigated(see Fig.S1).It was suggested that the effects of RH on the resistance of CRG based sensor cannot be neglected,and the dry system was nec-essary when the CRG based sensor worked in humid environments.
Finally,the sensing performance of the sensor based on CRG has been compared to that of gas sensor based on CRG-2(reduced from hydrazine),through exposure of the sensors to DMMP vapors at different concentrations(10ppm and30ppm).In order to decrease the effects of the differences of?lm morphologies on the?nal sens-ing performance,the devices with the close resistance values have been chosen.As shown in Fig.11(a)and(b),the gas sensor based on CRG exhibits much better response than that of the gas sen-sor based on CRG-2.About4.7times larger response to DMMP with30ppm concentration for the sensor based on CRG can be achieved compared with the sensor based on CRG-2.Moreover, the response of the sensor based on CRG is more than3.3times higher than that of the sensor based on CRG-2,when the DMMP concentration is decreased to10ppm.The reason for the difference of the sensing performance is not fully understood.It is suggested that more oxygen-based moieties and structure defects existed in CRG(reduced from PPD),or better structures formed in CRG mem-branes,dominate the higher sensing performance of the gas sensor. Usually,the existed oxygen-based moieties and structure defects may result in the instability of the resultant sensing devices[9]. Since the sensing device based on CRG(reduced from PPD)is very stable,and shows better response than the senor based on CRG-2(fabricated by drop drying method),it is suggested that CRG (reduced from PPD)can be used as a promising sensing material. Comparing with CRG-2,the fabrication of the sensing devices based on CRG via drop drying method is environmentally friend,easy and scalable,which is expected to pave a new avenue for the gas
sensing
Fig.10.Response of CRG sensors to DMMP compared with other analytes diluted to5%of saturated vapor concentrations.
N.Hu et al./Sensors and Actuators B163 (2012) 107–114
113
Fig.11.The comparison(a)curves and(b)volumes of the resistant changes between CRG sensor and CRG-2sensor at different concentrations of DMMP.
application with the advantage of low cost,low power,and portable properties.
4.Conclusions
In this work,novel gas sensing devices based on p-phenylenediamine(PPD)reduced graphene oxide have been successfully fabricated and studied for the?rst time.Chemically reduced graphene oxide(CRG),which is formed from the reduction of graphene oxide(GO)by PPD,can be used as an excellent sensing material.Drop drying method can be exploited to create conduc-tive networks of CRG between interdigitated electrode arrays.The DMMP gas sensing performance of the resultant sensing device has been investigated and compared with that of sensors based on CRG reduced from hydrazine(CRG-2).It is found that the resultant sens-ing devices exhibit much better response to DMMP than that of the devices based on https://www.doczj.com/doc/b016023044.html,paring with the sensor based on CRG-2,about4.7times and3.3times larger responses to DMMP with concentrations at30ppm and10ppm,respectively,for the sensor based on CRG can be achieved.It showed excellent respon-sive repeatability to DMMP,as well.The easy,green and scalable achievement of the sensors based on CRG reduced by PPD with excellent performance is expected to pave a new avenue for the gas sensing application with the advantage of low cost,low power, and portable properties.
Acknowledgments
The authors gratefully acknowledge?nancial supports by the Hi-Tech Research and Development Program of China no. 2011AA050504,the Shanghai Science and Technology grant no. 09JC1407400,no.1052nm02000,and no.1052nm06800,and the National Natural Science Foundation of China no.51102164,no. 50730008,and no.50902092.Appendix A.Supplementary data
Supplementary data associated with this article can be found,in the online version,at doi:10.1016/j.snb.2012.01.016.
References
[1]J.Im,S.K.Sengupta,M.F.Baruch,C.D.Granz,S.Ammu,S.K.Manohar,J.E.Whit-
ten,A hybrid chemiresistive sensor system for the detection of organic vapors, Sens.Actuators B156(2011)715–722.
[2]Y.Zilberman,U.Tisch,G.Shuster,W.Pisula,X.L.Feng,K.Mullen,H.Hoick,
Carbon nanotube/hexa-peri-hexabenzocoronene bilayers for discrimination between nanopolar volatile organic compounds of cancer and humid atmo-spheres,Adv.Mater.22(2010)4317–4320.
[3]L.N.Cella,W.Chen,N.V.Myung, A.Mulchandani,Single-walled carbon
nanotube-based chemiresistive af?nity biosensors for small molecules:ultra-sensitive glucose detection,J.Am.Chem.Soc.132(2010)5024–5026.
[4]C.M.Hangarter,M.Bangar,A.Mulchandani,N.V.Myung,Conducting polymer
nanowires for chemiresistive and FET-based bio/chemical sensors,J.Mater.
Chem.20(2010)3131–3140.
[5]D.C.Meier, B.Raman,S.Semancik,Detecting chemical hazards with
temperature-programmed microsensors:overcoming complex analytical problems with multidimensional databases,Annu.Rev.Anal.Chem.2(2009) 463–484.
[6]A.Kolmakov,M.Moskovits,Chemical sensing and catalysis by one-dimensional
metal-oxide nanostructures,Annu.Rev.Mater.Res.34(2004)151–180.
[7]R.A.Potyrailo,Polymeric sensor materials:toward an alliance of com-
binatorial and rational design tools,Angew.Chem.Int.Ed.45(2006) 702–723.
[8]E.S.Snow,F.K.Perkins,E.J.Houser,S.C.Badescu,T.L.Reinecke,Chemical detec-
tion with a single-walled carbon nanotube capacitor,Science307(2005) 1942–1945.
[9]K.R.Ratinac,W.Yang,S.P.Ringer,F.Breat,Toward ubiquitous environmental
gas sensors-capitalizing on the promise of graphene,Environ.Sci.Technol.44 (2010)1167–1176.
[10]D.Du,J.Liu,X.Zhang,X.Cui,Y.Lin,One-step electrochemical deposition
of a graphene–ZrO2nanocomposite:preparation,characterization and appli-cation for detection of organophosphorus agents,J.Mater.Chem.21(2011) 8032–8037.
[11]H.Song,L.Zhang,C.He,Y.Qu,Y.Tian,Y.Lv,Graphene sheets decorated with
SnO2nanoparticles:in situ synthesis and highly ef?cient materials for catalu-minescence gas sensors,J.Mater.Chem.21(2011)5972–5977.
[12]Z.Jiang,J.Wang,L.Meng,Y.Huang,L.Liu,A highly ef?cient chemical sen-
sor material for ethanol:Al2O3/graphene nanocomposites fabricated from graphene oxide,https://www.doczj.com/doc/b016023044.html,mun.47(2011)6350–6352.
[13]W.Wu,Z.Liu,L.A.Jauregui,Q.Yu,R.Pillai,H.Cao,J.Bao,Y.P.Chen,S.S.Pei,Wafer-
scale synthesis of graphene by chemical vapor deposition and its application in hydrogen sensing,Sens.Actuators B150(2010)296–300.
[14]R.K.Joshi,H.Gomez,F.Alvi,A.Kumar,Graphene?lms and ribbons for sensing
of O2,and100ppm of CO and NO2in practical conditions,J.Phys.Chem.C114 (2010)6610–6613.
[15]R.Pearce,T.Iakimov,M.Andersson,L.Hultman,A.L.Spetz,R.Yakimova,Epi-
taxially grown graphene based gas sensors for ultra sensitive NO2detection, Sens.Actuators B155(2011)451–455.
[16]K.S.Novoselov,A.K.Geim,S.V.Morozov,I.V.Grigorieva,A.A.Firsov,Electric?eld
effect in atomically thin carbon?lms,Science306(2004)666–669.
[17]F.Schedin,A.K.Geim,S.V.Morozov,E.W.Hill,P.Blake,M.I.Katsnelson,K.S.
Novoselov,Detection of individual gas molecules adsorbed on graphene,Nat.
Mater.6(2007)652–655.
[18]J.T.Robinson,F.K.Perkins,E.S.Snow,Z.Q.Wei,P.E.Sheehan,Reduced graphene
oxide molecular sensors,Nano Lett.8(2008)3137–3140.
[19]R.Arsat,M.Breedon,M.Sha?ei,P.G.Spizziri,S.Gilje,R.B.Kaner,K.Kalantar-
Zadeh,W.Wlodarski,Graphene-like nano-sheets for surface acoustic wave gas sensor applications,Chem.Phys.Lett.467(2009)344–347.
[20]I.Jung,D.Dikin,S.Park,W.Cai,S.L.Mielke,R.S.Ruoff,Effect of water on electrical
properties of individual reduced graphene oxide sheets,J.Phys.Chem.C112 (2008)20264–20268.
[21]M.Qazi,G.Koley,NO2detection using microcantilever based potentiometry,
Sensors8(2008)7144–7156.
[22]E.H.Hwang,S.Adam,S.S.Das,Transport in chemically doped graphene in the
presence of adsorbed molecules,Phys.Rev.B76(2007)195421.
[23]K.S.Kim,Y.Zhao,H.Jang,S.Y.Lee,J.M.Kim,K.S.Kim,J.H.Ahn,P.Kim,J.Y.
Choi,B.H.Hong,Large-scale pattern growth of graphene?lms for stretchable transparent electrodes,Nature457(2009)706–710.
[24]S.Park,R.S.Ruoff,Chemical methods for the production of graphenes,Nat.
Nanotechnol.4(2009)217–224.
[25]J.D.Fowler,M.J.Allen,V.C.Tung,Y.Yang,R.B.Kaner,B.H.Weiller,Practi-
cal chemical sensors from chemically derived graphene,ACS Nano3(2009) 301–306.
[26]Y.P.Dan,Y.Lu,N.J.Kybert,Z.T.Luo,A.T.C.Johnson,Intrinsic response of
graphene vapor sensors,Nano Lett.9(2009)1472–1475.
[27]H.Vedala,D.C.Sorescu,G.P.Kotchey,A.Star,Chemical sensitivity of graphene
edges decorated with metal nanoparticles,Nano Lett.11(2011)2342–2347.
114N.Hu et al./Sensors and Actuators B163 (2012) 107–114
[28]M.Myers,J.Cooper,B.Pejcic,M.Baker,B.Raguse,L.Wieczorek,Functionalized
graphene as an aqueous phase chemiresistor sensing material,Sens.Actuators B155(2011)154–158.
[29]G.Lu,S.Park,K.Yu,R.S.Ruoff,L.E.Ocola,D.Rosenmann,J.Chen,Toward prac-
tical gas sensing with highly reduced graphene oxide:a new signal processing method to circumvent run-to-run and device-to-device variations,ACS Nano 5(2011)1154–1164.
[30]V.Dua,S.P.Asurwade,S.Ammu,S.R.Agnihotra,S.Jain,K.E.Roberts,S.Park,
R.S.Ruoff,S.K.Manohar,All-organic vapor sensor using inkjet-printed reduced graphene oxide,Angew.Chem.Int.Ed.49(2010)2154–2157.
[31]Y.Chen,X.Zhang,P.Yu,Y.Ma,Stable dispersions of graphene and highly
conducting graphene?lms:a new approach to creating colloids of graphene monolayers,https://www.doczj.com/doc/b016023044.html,mun.30(2009)4527–4529.
[32]https://www.doczj.com/doc/b016023044.html,nge,T.Hirsch,V.M.Mirsky,O.S.Wolfbeis,Hydrogen sensor based on a
graphene–palladium nanocomposite,Electrochim.Acta56(2011)3707–3712.
[33]D.Li,M.B.Muller,S.Gilje,R.B.Kaner,G.G.Wallace,Processable aqueous dis-
persions of graphene nanosheets,Nat.Nanotechnol.3(2008)101–105. [34]Y.Wang,Z.Zhou,Z.Yang,X.Chen,D.Xu,Y.Zhang,Gas sensors based on
deposited single-walled carbon nanotube networks for DMMP detection,Nano-technology20(2009)345502.
[35]Y.Wang,Z.Yang,Z.Hou,D.Xu,L.Wei,E.S.W.Kong,Y.Zhang,Flexible gas sensors
with assembled carbon nanotube thin?lms for DMMP vapor detection,Sens.
Actuators B150(2010)708–714.
[36]Y.Wang,N.Hu,Z.Zhou,D.Xu,Z.Wang,Z.Yang,H.Wei,E.S.W.Kong,Y.Zhang,
Single-walled carbon nanotube/cobalt phthalocyanine derivative hybrid mate-rial:preparation,characterization and its gas sensing properties,J.Mater.
Chem.21(2011)3779–3787.
[37]Y.Wang,Z.Wang,N.Hu,L.Wei,D.Xu,H.Wei,E.S.W.Kong,Y.Zhang,Hexa?u-
orobisphenol A covalently functionalized single-walled carbon nanotubes for detection of DMMP vapor,J.Nanosci.Nanotechnol.11(2011)4874–4881. [38]C.Hontoria-Lucas, A.J.Lopez-Peinado,J.D.Lopez-Gonzalez,M.J.Rojas-
Cervantes,R.M.Martin-Aranda,Study of oxygen-containing groups in a series of graphite oxides:physical and chemical characterization,Carbon33(1995) 1585–1592.
[39]H.K.Jeong,Y.P.Lee,https://www.doczj.com/doc/b016023044.html,haye,M.H.Park,K.H.An,I.J.Kim,C.W.Yang,C.Y.Park,
R.S.Ruoff,Y.H.Lee,Evidence of graphitic AB stacking order of graphite oxides, J.Am.Chem.Soc.130(2008)1362–1366.
[40]H.L.Guo,X.F.Wang,Q.Y.Qian,F.B.Wang,X.H.Xia,A green approach to syn-
thesis of graphene sheets using electrochemical technique,ACS Nano3(2009) 2653–2659.
[41]S.Stankovich, D.A.Dikin,R.D.Piner,K.A.Kohlhaas, A.Kleinhammers,Y.
Jia,Y.Wu,S.T.Nguyen,R.S.Ruoff,Synthesis of graphene-based nanosheets via chemical reduction of exfoliated graphite oxide,Carbon45(2007) 1558–1565.
[42]M.A.Pimenta,G.Dresselhaus,M.S.Dresselhaus,L.G.Cancado,A.Jorio,R.Saito,
Studying disorder in graphite-based systems by Raman spectroscopy,Phys.
Chem.Chem.Phys.9(2007)1276–1291.
[43]S.C.Lee,S.Y.Kim,W.S.Lee,S.Y.Jung,B.W.Hwang,D.Ragupathy,D.D.Lee,S.Y.
Lee,J.C.Kim,Effects of textural properties on the response of a SnO2-based gas sensor for the detection of chemical warfare agents,Sensors11(2011) 6893–6904.[44]K.Cattanach,R.D.Kulkarni,M.Kozlov,S.K.Manohar,Flexible carbon
nanotube sensors for nerve agent simulants,Nanotechnology17(2006) 4123–4128.
[45]A.Kaniyoor,S.Ramaprabhu,Hybrid carbon nanostructured ensembles as
chemiresistive hydrogen gas sensors,Carbon49(2011)227–236.
[46]C.Gomez-Navarro,R.T.Weitz,A.M.Bittner,M.Sacolari,A.Mews,M.Burghard,
K.Kern,Electronic transport properties of individual chemically reduced graphene oxide sheets,Nano Lett.7(2007)3499–3503.
[47]D.Yang,A.Velamakanni,G.Bozoklu,S.Park,M.Stoller,R.D.Piner,S.Stankovich,
I.Jung,D.A.Field,C.A.Ventrice,R.S.Ruoff,Chemical analysis of graphene oxide
?lms after heat and chemical treatments by X-ray photoelectron and micro-Raman spectroscopy,Carbon47(2009)145–152.
[48]L.AI-Mashat,K.Shin,K.Kalantar-Zadeh,J.D.Plessis,S.H.Han,R.W.Kojima,
R.B.Kaner,D.Li,X.Gou,S.J.Ippolito,W.Wlodarski,Graphene/polyaniline nanocomposite for hydrogen sensing,J.Phys.Chem.C114(2010) 16168–16173.
Biographies
Nantao Hu received the Ph.D.degree in Polymer Chemistry and Physics from Jilin University,China,in2007.He is currently an assistant researcher at Shang-hai Jiaotong University,China.His research interests include chemical sensors and biosensors.
Yanyan Wang received the Ph.D.degree in Microelectronic and Solid-state Electron-ics at Shanghai Jiaotong University in China.She is currently an assistant researcher at Soochow University,China.Her research interests include gas sensing materials and gas sensors.
Jing Chai received her B.A.degree in Chemistry from Lanzhou University,China,in 2009.She is currently working toward the M.S.degree in Electronic and Communi-cation Engineering at Shanghai Jiaotong University in China.Her research interests include gas sensors based on low dimensional nanomaterials.
Rungang Gao received her B.A.degree in Chemistry from Lanzhou University,China, in2009.She is currently working toward the M.S.degree in Electronic and Commu-nication Engineering at Shanghai Jiaotong University in China.Her research interests include gas sensors based on graphene.
Zhi Yang received the Ph.D.degree in Physical Chemistry from Lanzhou University, China,in2005.He is currently an assistant professor at Shanghai Jiaotong University, China.His research interests include chemical sensors and biosensors.
Eric Siu-Wai Kong is currently a professor at Shanghai Jiaotong University,China. His research interests include electrochemistry and chemical sensor technology. Yafei Zhang is currently a professor at Shanghai Jiaotong University,China.His research interests include synthesis of gas-sensing nanomaterials and biomaterials and their applications in nanodevice.
On the contrary Onthecontrary, I have not yet begun. 正好相反，我还没有开始。 https://www.doczj.com/doc/b016023044.html, Onthecontrary, the instructions have been damaged. 反之，则说明已经损坏。 https://www.doczj.com/doc/b016023044.html, Onthecontrary, I understand all too well. 恰恰相反，我很清楚 https://www.doczj.com/doc/b016023044.html, Onthecontrary, I think this is good. ⑴我反而觉得这是好事。 https://www.doczj.com/doc/b016023044.html, Onthecontrary, I have tons of things to do 正相反，我有一大堆事要做 Provided by jukuu Is likely onthecontrary I in works for you 反倒像是我在为你们工作 https://www.doczj.com/doc/b016023044.html, Onthecontrary, or to buy the first good. 反之还是先买的好。 https://www.doczj.com/doc/b016023044.html, Onthecontrary, it is typically american. 相反，这正是典型的美国风格。 222.35.143.196 Onthecontrary, very exciting.
恰恰相反，非常刺激。 https://www.doczj.com/doc/b016023044.html, But onthecontrary, lazy. 却恰恰相反，懒洋洋的。 https://www.doczj.com/doc/b016023044.html, Onthecontrary, I hate it! 恰恰相反，我不喜欢！ https://www.doczj.com/doc/b016023044.html, Onthecontrary, the club gathers every month. 相反，俱乐部每个月都聚会。 https://www.doczj.com/doc/b016023044.html, Onthecontrary, I'm going to work harder. 我反而将更努力工作。 https://www.doczj.com/doc/b016023044.html, Onthecontrary, his demeanor is easy and nonchalant. 相反，他的举止轻松而无动于衷。 https://www.doczj.com/doc/b016023044.html, Too much nutrition onthecontrary can not be absorbed through skin. 太过营养了反而皮肤吸收不了. https://www.doczj.com/doc/b016023044.html, Onthecontrary, I would wish for it no other way. 正相反，我正希望这样 Provided by jukuu Onthecontrary most likely pathological. 反之很有可能是病理性的。 https://www.doczj.com/doc/b016023044.html, Onthecontrary, it will appear clumsy. 反之，就会显得粗笨。 https://www.doczj.com/doc/b016023044.html,
一般过去式 时间状语：yesterday just now (刚刚) the day before three days ag0 a week ago in 1880 last month last year 1. I was in the classroom yesterday. I was not in the classroom yesterday. Were you in the classroom yesterday. 2. They went to see the film the day before. Did they go to see the film the day before. They did go to see the film the day before. 3. The man beat his wife yesterday. The man didn’t beat his wife yesterday. 4. I was a high student three years ago. 5. She became a teacher in 2009. 6. They began to study english a week ago 7. My mother brought a book from Canada last year. 8.My parents build a house to me four years ago . 9.He was husband ago. She was a cooker last mouth. My father was in the Xinjiang half a year ago. 10.My grandfather was a famer six years ago. 11.He burned in 1991
●I wonder if it’s because I have been at school for so long that I’ve grown so crazy about going home. ●It is because she wasn’t well that she fell far behind her classmates this semester. ●I can well remember that there was a time when I took it for granted that friends should do everything for me. ●In order to make a difference to society, they spent almost all of their spare time in raising money for the charity. ●It’s no pleasure eating at school any longer because the food is not so tasty as that at home. ●He happened to be hit by a new idea when he was walking along the riverbank. ●I wonder if I can cope with stressful situations in life independently. ●It is because I take things for granted that I make so many mistakes. ●The treasure is so rare that a growing number of people are looking for it. ●He picks on the weak mn in order that we may pay attention to him. ●It’s no pleasure being disturbed whena I settle down to my work. ●I can well remember that when I was a child, I always made mistakes on purpose for fun. ●It’s no pleasure accompany her hanging out on the street on such a rainy day. ●I can well remember that there was a time when I threw my whole self into study in order to live up to my parents’ expectation and enter my dream university. ●I can well remember that she stuck with me all the time and helped me regain my confidence during my tough time five years ago. ●It is because he makes it a priority to study that he always gets good grades. ●I wonder if we should abandon this idea because there is no point in doing so. ●I wonder if it was because I ate ice-cream that I had an upset student this morning. ●It is because she refused to die that she became incredibly successful. ●She is so considerate that many of us turn to her for comfort. ●I can well remember that once I underestimated the power of words and hurt my friend. ●He works extremely hard in order to live up to his expectations. ●I happened to see a butterfly settle on the beautiful flower. ●It’s no pleasure making fun of others. ●It was the first time in the new semester that I had burned the midnight oil to study. ●It’s no pleasure taking everything into account when you long to have the relaxing life. ●I wonder if it was because he abandoned himself to despair that he was killed in a car accident when he was driving. ●Jack is always picking on younger children in order to show off his power. ●It is because he always burns the midnight oil that he oversleeps sometimes. ●I happened to find some pictures to do with my grandfather when I was going through the drawer. ●It was because I didn’t dare look at the failure face to face that I failed again. ●I tell my friend that failure is not scary in order that she can rebound from failure. ●I throw my whole self to study in order to pass the final exam. ●It was the first time that I had made a speech in public and enjoyed the thunder of applause. ●Alice happened to be on the street when a UFO landed right in front of her. ●It was the first time that I had kept myself open and talked sincerely with my parents. ●It was a beautiful sunny day. The weather was so comfortable that I settled myself into the
高中英语~词性~句子成分~语法构成 第一章节：英语句子中的词性 1.名词：n. 名词是指事物的名称，在句子中主要作主语.宾语.表语.同位语。 2.形容词;adj. 形容词是指对名词进行修饰~限定~描述~的成份，主要作定语.表语.。形容词在汉语中是（的）.其标志是: ous. Al .ful .ive。. 3.动词：vt. 动词是指主语发出的一个动作，一般用来作谓语。 4.副词：adv. 副词是指表示动作发生的地点. 时间. 条件. 方式. 原因. 目的. 结果.伴随让步. 一般用来修饰动词. 形容词。副词在汉语中是（地）.其标志是：ly。 5.代词：pron. 代词是指用来代替名词的词，名词所能担任的作用，代词也同样.代词主要用来作主语. 宾语. 表语. 同位语。 6.介词：prep.介词是指表示动词和名次关系的词，例如：in on at of about with for to。其特征：
介词后的动词要用—ing形式。介词加代词时，代词要用宾格。例如：give up her（him）这种形式是正确的，而give up she（he）这种形式是错误的。 7.冠词：冠词是指修饰名词，表名词泛指或特指。冠词有a an the 。 8.叹词：叹词表示一种语气。例如：OH. Ya 等 9.连词：连词是指连接两个并列的成分，这两个并列的成分可以是两个词也可以是两个句子。例如：and but or so 。 10.数词：数词是指表示数量关系词，一般分为基数词和序数词 第二章节：英语句子成分 主语：动作的发出者，一般放在动词前或句首。由名词. 代词. 数词. 不定时. 动名词. 或从句充当。 谓语：指主语发出来的动作，只能由动词充当，一般紧跟在主语后面。 宾语：指动作的承受着，一般由代词. 名词. 数词. 不定时. 动名词. 或从句充当. 介词后面的成分也叫介词宾语。 定语：只对名词起限定修饰的成分，一般由形容
M A: Has the case been closed yet? B: No, the magistrate still needs to decide the outcome. magistrate n.地方行政官，地方法官，治安官 A: I am unable to read the small print in the book. B: It seems you need to magnify it. magnify vt.１．放大，扩大；２．夸大，夸张 A: That was a terrible storm. B: Indeed, but it is too early to determine the magnitude of the damage. magnitude n.１．重要性，重大；２．巨大，广大 A: A young fair maiden like you shouldn’t be single. B: That is because I am a young fair independent maiden. maiden n.少女，年轻姑娘，未婚女子 a.首次的，初次的 A: You look majestic sitting on that high chair. B: Yes, I am pretending to be the king! majestic a.雄伟的，壮丽的，庄严的，高贵的 A: Please cook me dinner now. B: Yes, your majesty, I’m at your service. majesty n.１．［Ｍ－］陛下（对帝王，王后的尊称）；２．雄伟，壮丽，庄严 A: Doctor, I traveled to Africa and I think I caught malaria. B: Did you take any medicine as a precaution? malaria n.疟疾 A: I hate you! B: Why are you so full of malice? malice n.恶意，怨恨 A: I’m afraid that the test results have come back and your lump is malignant. B: That means it’s serious, doesn’t it, doctor? malignant a.１．恶性的，致命的；２．恶意的，恶毒的 A: I’m going shopping in the mall this afternoon, want to join me? B: No, thanks, I have plans already. mall n.（由许多商店组成的）购物中心 A: That child looks very unhealthy. B: Yes, he does not have enough to eat. He is suffering from malnutrition.
意见应以事实为根据. 3 来自辞典例句 192. The bombers swooped ( down ) onthe air base. 轰炸机 突袭 空军基地. 来自辞典例句 193. He mounted their engines on a rubber base. 他把他们的发动机装在一个橡胶垫座上. 14 来自辞典例句 194. The column stands on a narrow base. 柱子竖立在狭窄的地基上. 14 来自辞典例句 195. When one stretched it, it looked like grey flakes on the carvas base. 你要是把它摊直, 看上去就象好一些灰色的粉片落在帆布底子上. 18 来自辞典例句 196. Economic growth and human well - being depend on the natural resource base that supports all living systems. 经济增长和人类的福利依赖于支持所有生命系统的自然资源. 12 1 来自辞典例句 197. The base was just a smudge onthe untouched hundred - mile coast of Manila Bay. 那基地只是马尼拉湾一百英里长安然无恙的海岸线上一个硝烟滚滚的污点. 6 来自辞典例句 198. You can't base an operation on the presumption that miracles are going to happen. 你不能把行动计划建筑在可能出现奇迹的假想基础上.
英语造句大全English sentence 在句子中，更好的记忆单词！ 1、(1)、able adj. 能 句子：We are able to live under the sea in the future. (2)、ability n. 能力 句子：Most school care for children of different abilities. (3)、enable v. 使。。。能句子：This pass enables me to travel half-price on trains. 2、(1)、accurate adj. 精确的句子：We must have the accurate calculation. (2)、accurately adv. 精确地 句子：His calculation is accurately. 3、(1)、act v. 扮演 句子：He act the interesting character. （2）、actor n. 演员 句子：He was a famous actor. (3)、actress n. 女演员 句子：She was a famous actress. (4)、active adj. 积极的 句子：He is an active boy. 4、add v. 加 句子：He adds a little sugar in the milk. 5、advantage n. 优势 句子：His advantage is fight. 6、age 年龄n. 句子：His age is 15. 7、amusing 娱人的adj. 句子：This story is amusing. 8、angry 生气的adj. 句子：He is angry. 9、America 美国n.
主语+谓语 1. 理解主谓结构 1) The students arrived. The students arrived at the park. 2) They are listening. They are listening to the music. 3) The disaster happened. 2．体会状语的位置 1) Tom always works hard. 2) Sometimes I go to the park at weekends.. 3) The girl cries very often. 4) We seldom come here. The disaster happened to the poor family. 3. 多个状语的排列次序 1) He works. 2) He works hard. 3) He always works hard. 4) He always works hard in the company. 5) He always works hard in the company recently. 6) He always works hard in the company recently because he wants to get promoted. 4. 写作常用不及物动词 1. ache My head aches. I’m aching all over. 2. agree agree with sb. about sth. agree to do sth. 3. apologize to sb. for sth. 4. appear (at the meeting, on the screen) 5. arrive at / in 6. belong to 7. chat with sb. about sth. 8. come (to …) 9. cry 10. dance 11. depend on /upon 12. die 13. fall 14. go to … 15. graduate from 16. … happen 17. laugh 18. listen to... 19. live 20. rise 21. sit 22. smile 23. swim 24. stay (at home / in a hotel) 25. work 26. wait for 汉译英： 1.昨天我去了电影院。 2.我能用英语跟外国人自由交谈。 3.晚上7点我们到达了机场。 4.暑假就要到了。 5.现在很多老人独自居住。 6.老师同意了。 7.刚才发生了一场车祸。 8.课上我们应该认真听讲。9. 我们的态度很重要。 10. 能否成功取决于你的态度。 11. 能取得多大进步取决于你付出多少努力。 12. 这个木桶能盛多少水取决于最短的一块板子的长度。
【it's time to和it's time for】 ——————这其实是一个句型,只不过后面要跟不同的东西. ——————It's time to跟的是不定式（to do）.也就是说,要跟一个动词,意思是“到做某事的时候了”.如： It's time to go home. It's time to tell him the truth. ——————It's time for 跟的是名词.也就是说,不能跟动词.如： It's time for lunch.(没必要说It's time to have lunch) It's time for class.(没必要说It's time to begin the class.) They can't wait to see you Please ask liming to study tonight. Please ask liming not to play computer games tonight. Don’t make/let me to smoke I can hear/see you dance at the stage You had better go to bed early. You had better not watch tv It’s better to go to bed early It’s best to run in the morning I am enjoy running with music. With 表伴随听音乐 I already finish studying You should keep working. You should keep on studying English Keep calm and carry on 保持冷静继续前行二战开始前英国皇家政府制造的海报名字 I have to go on studying I feel like I am flying I have to stop playing computer games and stop to go home now I forget/remember to finish my homework. I forget/remember cleaning the classroom We keep/percent/stop him from eating more chips I prefer orange to apple I prefer to walk rather than run I used to sing when I was young What’s wrong with you There have nothing to do with you I am so busy studying You are too young to na?ve I am so tired that I have to go to bed early
《The Kite Runner》追风筝的人--------------------------------美句摘抄 1.I can still see Hassan up on that tree, sunlight flickering through the leaves on his almost perfectly round face, a face like a Chinese doll chiseled from hardwood: his flat, broad nose and slanting, narrow eyes like bamboo leaves, eyes that looked, depending on the light, gold, green even sapphire 翻译：我依然能记得哈桑坐在树上的样子，阳光穿过叶子，照着他那浑圆的脸庞。他的脸很像木头刻成的中国娃娃，鼻子大而扁平，双眼眯斜如同竹叶，在不同光线下会显现出金色、绿色，甚至是宝石蓝。 E.g.: A shadow of disquiet flickering over his face. 2.Never told that the mirror, like shooting walnuts at the neighbor's dog, was always my idea. 翻译：从来不提镜子、用胡桃射狗其实都是我的鬼主意。E.g.:His secret died with him, for he never told anyone. 3.We would sit across from each other on a pair of high
一、翻译 1. The idea of consciously seeking out a special title was new to me., but not without appeal. 让我自己挑选自己最喜欢的书籍这个有意思的想法真的对我具有吸引力。 2.I was plunged into the aching tragedy of the Holocaust, the extraordinary clash of good, represented by the one decent man, and evil. 我陷入到大屠杀悲剧的痛苦之中，一个体面的人所代表的善与恶的猛烈冲击之中。 3.I was astonished by the the great power a novel could contain. I lacked the vocabulary to translate my feelings into words. 我被这部小说所包含的巨大能量感到震惊。我无法用语言来表达我的感情（心情）。 4，make sth. long to short长话短说 5.I learned that summer that reading was not the innocent(简单的) pastime(消遣) I have assumed it to be., not a breezy, instantly forgettable escape in the hammock(吊床)，( though I’ ve enjoyed many of those too ). I discovered that a book, if it arrives at the right moment, in the proper season, will change the course of all that follows. 那年夏天，我懂得了读书不是我认为的简单的娱乐消遣，也不只是躺在吊床上，一阵风吹过就忘记的消遣。我发现如果在适宜的时间、合适的季节读一本书的话，他将能改变一个人以后的人生道路。 二、词组造句 1. on purpose 特意，故意 This is especially true here, and it was ~. (这一点在这里尤其准确，并且他是故意的) 2.think up 虚构，编造，想出 She has thought up a good idea. 她想出了一个好的主意。 His story was thought up. 他的故事是编出来的。 3. in the meantime 与此同时 助记：in advance 事前in the meantime 与此同时in place 适当地... In the meantime, what can you do? 在这期间您能做什么呢？ In the meantime, we may not know how it works, but we know that it works. 在此期间，我们不知道它是如何工作的，但我们知道，它的确在发挥作用。 4.as though 好像，仿佛 It sounds as though you enjoyed Great wall. 这听起来好像你喜欢长城。 5. plunge into 使陷入 He plunged the room into darkness by switching off the light. 他把灯一关，房
The effective sentences:(improve the sentences!) 1.She hopes to spend this holiday either in Shanghai or in Suzhou. 2.Showing/to show sincerity and to keep/keeping promises are the basic requirements of a real friend. 3.I want to know the space of this house and when it was built. I want to know how big this house is and when it was built. I want to know the space of this house and the building time of the house. 4.In the past ten years,Mr.Smith has been a waiter,a tour guide,and taught English. In the past ten years,Mr.Smith has been a waiter,a tour guide,and an English teacher. 5.They are sweeping the floor wearing masks. They are sweeping the floor by wearing masks. wearing masks,They are sweeping the floor. 6.the drivers are told to drive carefully on the radio. the drivers are told on the radio to drive carefully 7.I almost spent two hours on this exercises. I spent almost two hours on this exercises. 8.Checking carefully,a serious mistake was found in the design. Checking carefully,I found a serious mistake in the design.
M1 U1 一. 把下列短语填入每个句子的空白处（注意所填短语的形式变化）： add up (to) be concerned about go through set down a series of on purpose in order to according to get along with fall in love (with) join in have got to hide away face to face 1 We’ve chatted online for some time but we have never met ___________. 2 It is nearly 11 o’clock yet he is not back. His mother ____________ him. 3 The Lius ___________ hard times before liberation. 4 ____________ get a good mark I worked very hard before the exam. 5 I think the window was broken ___________ by someone. 6 You should ___________ the language points on the blackboard. They are useful. 7 They met at Tom’s party and later on ____________ with each other. 8 You can find ____________ English reading materials in the school library. 9 I am easy to be with and _____________my classmates pretty well. 10 They __________ in a small village so that they might not be found. 11 Which of the following statements is not right ____________ the above passage? 12 It’s getting dark. I ___________ be off now. 13 More than 1,000 workers ___________ the general strike last week. 14 All her earnings _____________ about 3,000 yuan per month. 二.用以下短语造句： 1.go through 2. no longer/ not… any longer 3. on purpose 4. calm… down 5. happen to 6. set down 7. wonder if 三. 翻译： 1.曾经有段时间，我对学习丧失了兴趣。（there was a time when…） 2. 这是我第一次和她交流。（It is/was the first time that …注意时态） 3.他昨天公园里遇到的是他的一个老朋友。（强调句） 4. 他是在知道真相之后才意识到错怪女儿了。（强调句） M 1 U 2 一. 把下列短语填入每个句子的空白处（注意所填短语的形式变化）： play a …role (in) because of come up such as even if play a …part (in) 1 Dujiangyan(都江堰) is still ___________in irrigation(灌溉) today. 2 That question ___________ at yesterday’s meeting. 3 Karl Marx could speak a few foreign languages, _________Russian and English. 4 You must ask for leave first __________ you have something very important. 5 The media _________ major ________ in influencing people’s opinion s. 6 _________ years of hard work she looked like a woman in her fifties. 二.用以下短语造句： 1.make (good/full) use of 2. play a(n) important role in 3. even if 4. believe it or not 5. such as 6. because of
English sentence 1、(1)、able adj. 能 句子：We are able to live under the sea in the future. (2)、ability n. 能力 句子：Most school care for children of different abilities. (3)、enable v. 使。。。能 句子：This pass enables me to travel half-price on trains. 2、(1)、accurate adj. 精确的 句子：We must have the accurate calculation. (2)、accurately adv. 精确地 句子：His calculation is accurately. 3、(1)、act v. 扮演 句子：He act the interesting character.（2）、actor n. 演员 句子：He was a famous actor. (3)、actress n. 女演员 句子：She was a famous actress. (4)、active adj. 积极的 句子：He is an active boy. 4、add v. 加 句子：He adds a little sugar in the milk. 5、advantage n. 优势 句子：His advantage is fight. 6、age 年龄n. 句子：His age is 15. 7、amusing 娱人的adj. 句子：This story is amusing. 8、angry 生气的adj. 句子：He is angry. 9、America 美国n. 句子：He is in America. 10、appear 出现v. He appears in this place. 11. artist 艺术家n. He is an artist. 12. attract 吸引 He attracts the dog. 13. Australia 澳大利亚 He is in Australia. 14.base 基地 She is in the base now. 15.basket 篮子 His basket is nice. 16.beautiful 美丽的 She is very beautiful. 17.begin 开始 He begins writing. 18.black 黑色的 He is black. 19.bright 明亮的 His eyes are bright. 20.good 好的 He is good at basketball. 21.British 英国人 He is British. 22.building 建造物 The building is highest in this city 23.busy 忙的 He is busy now. 24.calculate 计算 He calculates this test well. 25.Canada 加拿大 He borns in Canada. 26.care 照顾 He cared she yesterday. 27.certain 无疑的 They are certain to succeed. 28.change 改变 He changes the system. 29.chemical 化学药品