Polycurcumin acrylate and Polycurcumin methacrylate: Novel bio-based polymers for explosive chemical...

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Sensors and Actuators B 181 (2013) 144– 152

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Sensors and Actuators B: Chemical

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Polycurcumin acrylate and polycurcumin methacrylate: Novel bio-basedpolymers for explosive chemical sensor

Bedanta Gogoi, Priyanka Dutta, Niloy Paul, Narendra N. Dass, Neelotpal Sen Sarma ∗

Physical Sciences Division, Polymer Section, Institute of Advanced Study in Science and Technology, Guwahati 781035, Assam, India

a r t i c l e i n f o

Article history:Received 17 October 2012Received in revised form 11 January 2013Accepted 15 January 2013Available online 7 February 2013

Keywords:CurcuminPolycurcumin methacrylatePolycurcumin acrylateChemical sensorSensitivity

a b s t r a c t

This article reports the development of a very simple chemical sensor for nitroaromatic compound froma couple of novel bio-based polymers polycurcumin methacrylate (PCUMA) and polycurcumin acry-late (PCUA). The polymers were characterized by spectroscopic methods and the thermal behavior wasobserved by thermo gravimetric analysis. Molecular weight of the polymers was determined by gel per-meation chromatography. The polymers exhibit purely electronic conduction and was confirmed byWagner polarization technique. Sensitivities of the polymers were observed by monitoring the impedanceresponse and current–voltage characteristics in presence of the vapor of analytes. The conduction level ofPCUMA in presence of the analytes was found to be remarkably high compared to that of PCUA. PCUMAshowed one order decrease in log Z values in impedance measurements and 90.44% increase in currentdensity in current–voltage characteristics in presence of picric acid.

© 2013 Elsevier B.V. All rights reserved.

1. Introduction

Explosive sensors are substances capable of detecting specificchemicals used in explosives and transforms chemical informationinto an analytically useful signal [1]. The non-destructive detectionof explosives is essential for protection and criminal investigations,minefield remediation, military applications, ammunition reme-diation sites, homeland security applications etc., and chemicalsensors plays a vital role in such cases [2,3]. Generally nitroaro-matic compounds viz. TNT, DNT, RDX, picric acid etc. are regardedas explosive chemicals due to their very low vapor pressure andhigh volatility. For example vapor pressure of TNT and RDX are5.8 × 10−6 Torr and 4.6 × 10−9 Torr respectively [4]. These chem-icals upon initiation can undergo highly exothermic reactionsyielding gaseous products. Besides, they also causes soil and waterpollution [5]. Hence it is very important to detect the presence ofsuch explosive chemicals in our environment.

Literature shows that there are numerous examples of polymerbased explosive sensors that are prepared from materials which arenot readily available and further causes health and environmen-tal problems. So it becomes pertinent to produce some bio-basedexplosive chemical sensors to minimize such problems. We haveobserved that some bio-based polymer obtained from curcumin,polycurcumin methacrylate (PCUMA) and polycurcumin acrylate(PCUA) can also be employed as chemical sensors for the detection

∗ Corresponding author. Tel.: +91 0361 2270084; fax: +91 0361 2740659.E-mail address: [email protected] (N.S. Sarma).

of nitroaromatic compounds. The former is a potential chemicalsensor for nitroaromatic compounds. The construction of the sen-sor depends upon the materials incorporated, their properties alongwith the type and nature of the analyte. Different processes werealso developed depending upon the properties of the materials to beused. For example if the material is conducting then there is changein its electrochemical properties [6–8], if the material is originallyfluorescent then there is change in the fluorescence property [9,10],if the material have characteristic color then there is change in itscolorimetric properties [11,12] etc. in presence of the analyte.

Curcumin [1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione] [13] is well known as yellow coloringdye and is found in rhizomes of turmeric plant (Curcuma Longa).It constitutes 77% of curcuminoids in C. longa [14]. Extensiveresearch over the past 30 years has indicated that this moleculehas therapeutic potential against a wide range of diseases, suchas cancer, lung diseases, neurological diseases, liver diseases,metabolic diseases, autoimmune diseases, cardiovascular diseases,and various other inflammatory diseases [15]. The compound wasisolated by Vogel in 1815 [16] and in 1910 Milobedzka deter-mined the structure as diferuloylmethane and this compound wassynthesized in 1918 by Lampe [17,18]. The proposed structure ofthe compound has a �-diketone moiety and hence can undergoKeto-enol tautomerism [19] as follows. The free hydroxyl groupof the enol form can also form hydrogen bond with the carbonyloxygen atom.

Esterification of the molecule is possible due to the presence ofhydroxyl groups. In this work, we have successfully synthesized thepolymers for the first time with a great applicability in the field of

0925-4005/$ – see front matter © 2013 Elsevier B.V. All rights reserved.http://dx.doi.org/10.1016/j.snb.2013.01.071


B. Gogoi et al. / Sensors and Actuators B 181 (2013) 144– 152 145

chemical sensors as it acts as selective chemical sensor for nitroaro-matic compounds. These two polymers showed satisfactory resultseven in a very simple experimental set up that we have designedin our laboratory for testing.

2. Experimental

2.1. Materials

Curcumin was extracted from turmeric powder as reported ear-lier [20]. Acrylic acid (Merck), ethyl methyl ketone (Merck), triethylamine (Merck), methanol (Ranbaxy) were used without furtherpurification. Commercially available picric acid (LOBA CHEMIE) isstored in bottles with about 50% water for safety reasons. Before thesensing experiments it was withdrawn from the bottle and repeat-edly dried in vacuum desiccators for long times to remove eventrace amount of water molecules.

2.2. Preparation of methacryloyl chloride and acryloyl chloride

A mixture of methacrylic acid and benzoyl chloride (1:2 molratios) was distilled at its boiling point in a three neck round bottomflask in presence of small amount of hydroquinone. The distilledproduct was collected in a collector placed inside an ice bath. Theproduct was redistilled for further purification. Acryloyl chloridewas prepared in the same manner using acrylic acid instead ofmethacrylic acid.

2.3. Preparation of PCUMA and PCUA

One gram mol of curcumin was dissolved in 100 ml of ethylmethyl ketone in two necks round bottom flask. To it 2 g mol ofmethacryloyl chloride mixed with 25 ml of ethyl methyl ketonewas added drop wise and the reaction mixture was stirred con-tinuously for about 2 h on an ice bath. 1.1 g mol of triethyl aminewas then added to this reaction mixture to neutralize the acid pro-duced during the reaction. The reaction mixture was again stirredfor about an hour at room temperature and allowed to stand for24 h. It was then filtered, washed with Milli Q water and furtherwashed by 0.1 N NaOH solution. The organic layer produced afterfiltration was separated through separating funnel and distilled toremove the solvent. The final product polycurcumin methacrylate

(PCUMA) was obtained by heating the viscous solution containingmonomeric curcumin methacrylate to about 100 ◦C. The prod-uct was washed with methanol and Milli Q water to remove theimpurities as well as oligomers. Synthetic route for PCUA is verysimilar except the acid chloride used. The acid chloride used forPCUMA is methacryloyl chloride while that for PCUA it is acryloylchloride.

2.4. Physical measurements

The molecular weight was determined in THF by threecolumns GPC system (WATERS 2414). FT-IR spectra were recordedusing Brucker Vector 22 Spectrophotometer in the range of400–4000 cm−1. Samples for FT-IR measurements were preparedin the form of pellets by mixing about 20 mg of IR spectroscopicgrade potassium bromide with about 2 mg of dried samples. Thespectra were recorded in transmission mode over 32 scans. Theelectronic transitions were observed by UV–vis spectral analysis,recorded in 1800 SHIMADZU UV–vis spectrophotometer. Thermo-gravimetric analysis was performed using Perkin Elmer TGA 4000at a heating rate of 10 ◦C per minute in nitrogen environment witha N2 flow rate of 20 ml/min.

2.5. Ac impedance and electronic conductivity measurements

The sensitivity of PCUA and PCUMA towards nitroaromatic com-pounds was evaluated using HIOKI 3532-50, LCR Hi-TESTER. Theplots were recorded in the frequency range of 100 Hz at roomtemperature and under a relative humidity of 60%. Sensitivity mea-surements were done by monitoring impedance response (Z) andcurrent–voltage (I–V) characteristics of the polymers in presenceof nitroaromatic compounds. A detector was made by pressing thepolymer in between two stainless steel plates of 1 cm2 area withunsymmetrical holes, end of these stainless steel plates were con-nected to the impedance analyzer. This detector was placed veryclose to the analyte inside a 100 c.c. vessel. Fabrication of devices forthe sensitivity experiments is shown in Fig. 1. The experimental setup is sufficiently small to place inside a humidity-controlled desic-cator to observe the sensitivity of the polymers at varying humidityconditions.

Fig. 1. Experimental setup used for the study of sensing properties of the prepared polymers.


146 B. Gogoi et al. / Sensors and Actuators B 181 (2013) 144– 152

3. Results and discussion

3.1. Reaction schemes

The chemical reactions taking place during the synthesis ofPCUMA is supposed to be as follows:

O O

OO

H

OO

O O

OO

H

OO

OCCH3 OCCH3H3CCO

*

H3CCO

*

O O

OO

H

OO

O O

OO

H

OO

OCCH3 OCCH3H3CCO

*

H3CCO

*

n

n

O O

OH

H

OCCH3

HO

H3CCO

Cl

O

I. Stirred for two hours in ice bath

II. Triethyl ammine

III. Stirred for 1 hr at room temperature

(b)

(c)

O O

OO

H

OO

OCCH3H3CCO

I. Distillation

II. 60-80oC for two hrs.

(a)

The monomer (a) formed in the first step of the reac-tion undergoes polymerization through the terminal C C doublebonds at a temperature range = 100 ◦C resulting into the chainpolymer (b). The structure of the polymer PCUA is shownin (c).

3.2. Characterization

3.2.1. FT-IR analysisFT-IR studies were done to investigate the changes in func-

tionalities of curcumin after esterification [Fig. 2(a)] to obtainthe polymer. One major change is observed due to the appear-ance of a new peak in the polymer, which is assigned to be thestretching vibration of ester carbonyl group. There is no appre-ciable shift in peak positions for the rest of the spectra indicating

no change in functionalities after polymerization; this is in accor-dance with the reaction scheme as discussed above. Two importantpeaks observed in curcumin are at 1630 and 1593 cm−1, assignedas stretching vibration of C C group in extended conjugationand aromatic C O stretching vibration [21]. Appearance of thenew peak at around 1733–1745 cm−1 in the polymers indicates

complete esterification of curcumin as it corresponds to symmet-ric stretching of C O bond of the ester group [22]. Aromatic C Cstretching vibration for curcumin, PCUA and PCUMA are observedat around 1442 cm−1, 1456 cm−1 and 1437 cm−1respectively [23].Peaks at around 1270–1280 cm−1are due to in plane C H bend-ing vibration of phenyl ring [24]. Ester C O single bond stretchingvibration is observed at 1034 cm−1 and 989 cm−1in PCUA and inPCUMA respectively [22]. The peaks at around 800 cm−1 is due toout of plane vibration of aromatic ring [25]. Besides these, broadpeaks at around 3300 cm−1 are assigned as the stretching vibra-tion of OH group as well as for H-bond of the enol form [16]. Bothsp2 CH stretch and sp3 CH stretch are observed for all the threecompounds [23].



4000 350 0 300 0 250 0 200 0 150 0 100 0 50 0

(a)

% T

ran

smit

tan

ce (

a.u

.)

Wave number (cm-1)

curcu min

PCUMA

PCUA

1733

1745

330 360 390 420 450 4800.0

0.2

0.4

0.6

0.8

1.0(b)

Ab

sorb

ance

Wave length (nm)

curcu min

PCUA

PCUMA

200 400 600 8000

20

40

60

80

100

(c)

% w

eight

loss

Tempera ture (oC)

PCUMA

PCUA

Fig. 2. (a) FT-IR spectra, (b) UV–vis spectra of curcumin, PCUMA and PCUA, (c) TGA thermograms of PCUMA and PCUA.

3.2.2. UV–vis spectraThe UV–vis spectra of curcumin and the polymers are given

in [Fig. 2(b)] were done using CHCl3 as the solvent. In eachspectrum two distinct absorptions are observed. In curcumin themajor peak at 390 nm is due to �–�* transition of the extended�-conjugated chromophore. The organic solution of curcuminexhibits a bright yellow color due to the low energy �–�* excita-tion of the chromophore. A very weak electronic dipole forbiddenn–�* transition of the carbonyl group of curcumin is located to thelonger wavelength side [26]. The absorption wavelength shifts tolonger wavelength in both the polymers. This is attributed due tothe fact that polymerization results in the extension of the conjuga-tion upto some extent which results in the decrease of the energy ofthe �* orbital. Hence in the polymers electronic excitation occursby absorbing lower amount of energy from UV-radiation resultinginto the shifting of the absorption maxima to longer wavelengthside.

Considering the �–�* transition we can determine the band gapfor electronic transition with the help of the formula E = h� = hc/�.The results are:

For curcumin, E = 3.18 eVFor PCUMA, E = 2.93 eVFor PCUA, E = 3.06 eV,The values are in the range of semiconductors.

3.2.3. Thermogravimetric analysisThe Fig. 2(c) shows the TGA thermograms and was recorded in

non-oxidative nitrogen environment within the temperature range50–900 ◦C. It shows two steps decomposition processes, in the firststep PCUA and PCUMA losses around 1.4% and 1.7% respectively ataround 100 ◦C. This weight loss is very small and is assumed to bedue to evaporation of moisture present in the polymer. Second step

decomposition occurs at around 415 ◦C, which shows 47% weightloss for PCUA and 50% for PCUMA. Due to tentative decompositionmechanism of the high molecular weighted polymer, it is difficultto identify the actual molecular fractions leaving at this tempera-ture. We assume that decomposition is due to removal of CO, CO2,hydrocarbons etc. After second decomposition the weight loss isvery slow up to 900 ◦C for both PCUMA and PCUA.

3.2.4. Molecular weight determinationThe molecular weights of the polymers were estimated from

GPC (gel permeation chromatography) method. The distributioncurves of GPC were given in Figure S1 in electronic supplementaryinformation (ESI). The results of GPC are

PCUMA : Mn = 81, 000 g mol−1, Mw = 85,000 g mol−1

and PDI = 1.07

PCUA : Mn = 400, 000 g mol−1, Mw = 540, 000 g mol−1

and PDI = 1.30

Hence both the polymers are of high molecular weight havinguniform chain length as the PDI approaches to 1. So it is monodis-persed.

3.3. Determination of transport number

The total electronic conduction can be determined by standardWagner polarization technique [27,28]. According to this methodwhen a voltage (V) is applied to a cell, ionic migration will occur



Fig. 3. (a) Schematic representation of cell circuit used in determination of electronic conductivity, (b) Polarized current vs time plot of PCUMA and PCUA.

until steady state is achieved. At the steady state, the cell is polar-ized and any residual current flows because of electron migrationacross the sample and interfaces. This is because the ionic cur-rents through an ion-blocking electrode fall rapidly with time if thesample is primarily ionic. We designed a circuit to monitor the elec-tronic conductivity, placing the sample (in pellet form) in betweentwo stainless steel anvils. A step potential of about 1.0 V was thenapplied and resulting potentiostatic current was monitored as afunction of time. The stainless steel anvils act as ion blocking elec-trodes for the above cell. The circuit diagram of the cell is shown inFig. 3(a).

For the experimental polymers the current v/s time plot, Fig. 3(b)shows no initial decrease in the total current with respect to time.That is the polymers are non-ionic in nature and its conductivityarises predominantly due to the electronic migration.

3.4. Sensitivity towards nitroaromatic compounds

Experimental setup used for this sensing experiment wasdemonstrated earlier. Fig. 4 shows the impedance response (Z) ofPCUMA and PCUA in presence of trace amount of nitrobenzene,picric acid and nitric acid. Here log Z v/s. time graph are plottedinstead of Z for better trace. All the measurements were doneat room temperature and at about 60% humidity. PCUMA showsone order decrease in log Z values when exposed to picric acid for10 min. However, a drastic decrease in log Z was observed within40 s as shown in Fig. 4(b) and after this a gradual decrease of Zvalue was observed till the end. For PCUA the decrease was not veryappreciable as shown in Fig. 4(c) and (d). The reversibility curveindicates the corresponding log Z values after removal of the ana-lytes. The plots for the polymers in presence of nitric acid are givenin ESI Figure S2 (a) and (b).

To study the effect of common interferent like humidity, CO2,ammonia etc., we measure the impedance at different humidity(20%, 40%, 60% and 80%) and also the sensitivity for picric acid atthese humidity condition. It was observed that variation of humid-ity cannot alter the sensitivity of the polymers. All these plots aregiven in ESI Figure S3 (a)–(d). The polymers also neither showedeffective sensing for other organic solvents like chloroform, 2-vinylpyridine, ammonia, triethylamine and CO2 nor decrease in sensi-tivity for picric acid in presence of the these chemicals that havesome common uses in laboratories [ESI Figure S3 (e) and (f)].

Along with impedance measurements we also determined thechange in the I–V characteristics of the polymers using same set upin presence of trace amount of the analytes as shown in Fig. 5. Herethe ac applied bias was increased to 5 V, up to which the polymersshows linear I–V characteristics. These measurements indicate thatthe sensitivity of the polymers can also be checked by applyinga bias voltage. PCUMA shows 61% and 90.44% increase in current

density in presence of nitrobenzene and picric acid respectively atthe maximum applied bias of 5 V. The values are found to be 17.69%and 53.29% respectively for PCUA.

Nitroaromatic compounds are good electron acceptor due tothe presence of electron withdrawing nitro groups in the aromaticrings. The reduction potential of the compounds become more andmore negative with the increase in the number of such groups in thearomatic ring and takes part in redox reactions [29]. Besides this,conducting polymers with extended conjugation are good electrondonors possessing �* electron delocalization. These are regardedto be good candidates for the redox interaction with nitroaromaticcompounds that blocks the �* electron delocalization of the conju-gated polymers [2]. The experimental polymers can also undergoredox reaction with nitroaromatic compounds for the same reason(Fig. 6). Ionic contribution for sensing of nitroaromatic compoundscannot be considered as the polymers were initially found to benon-polar by Wagner polarization technique. Germain et al. [30]introduced the term �-stacking interaction in between the poly-mer and analyte. This is a noncovalent interaction between thearomatic rings of the polymer and nitroaromatic compounds. Elec-trons participating in such interaction are now free to migrate andcause the increase in conductivity. These interactions occur selec-tively with electron withdrawing nitroaromatic compounds andhence no significant response was observed for other chemicalsand interferent mentioned in the previous paragraph. The differ-ence in sensitivities of the polymers PCUMA/PCUA is attributeddue to structural factors. The repeating unit of PCUMA contains twoelectron repelling methyl groups. With the +I effect of these methylgroups the electron donor ability of this polymer is quite high com-pared to that of PCUA in which no such elelctrophobic groups arepresent. Varying humidity has very negligible effect on the sens-ing level of the two polymers because these polymers undergoredox interaction preferentially with electron withdrawingcompounds.

It is now important to determine the sensitivity of cur-cumin alone. We performed the sensing experiments for curcuminalone by measuring impedance response and only a bit-changein log Z values was observed. It does not lead to the con-clusion that curcumin alone can be employed as detectorfor such purposes. The log Z v/s time plot for curcumin inpresence of picric acid and nitrobenzene were given in ESIFigure S4 (a) and (b).

3.5. Validation of method

Validation of the proposed method for chemical sensing wasdone with the help of I–V characteristics of PCUMA in picric acidfor convenience, as it requires very less time (within 10 s) to showthe results.



0 2 4 6 8 10

6.8

7.0

7.2

7.4

7.6

(a)

log Z

(k

Ohm

s)

Time (min)

in air

in nitroben zene

reversibility

0 2 4 6 8 103.80

3.84

3.88

3.92

3.96 (c)

log Z

(k

Ohm

s)

Time ( min)

in air

in nitrobenzene

reversibi lity

0 2 4 6 8 10

6.6

6.8

7.0

7.2

7.4

7.6

(b)

log Z

(k

Ohm

s)

Time ( min)

in air

in picric acid

reversibi lity

0 2 4 6 8 10

3.80

3.84

3.88

3.92

3.96 (d)

log Z

(k

ohm

s)

Time ( min)

in air

in picric acid

reversibility

Fig. 4. Sensitivity of (a) PCUMA in nitrobenzene, (b) PCUMA in picric acid, (c) PCUA in nitrobenzene and (d) PCUA in picric acid.

3.5.1. Calibration curveCalibration curve was constructed by plotting the mean current

developed at different amounts of picric acid. The current densityof the polymer increases as the number of nitro groups increaseswith the increase in the amount of picric acid [Fig. 7(a)]. The corre-lation coefficient for the calibration curve [Fig. 7(b)] was found to be0.9954 with relative standard deviation (RSD) of 5.07%. Detectionlimit (DL) was determined using the formula DL = 3.3 �/S, where,

‘�’ is the standard deviation of the response and ‘S’ is the slope ofcalibration curve and was found to be approximately 1.3 × 10−3 gof picric acid.

3.5.2. Precision of measurements and stability of sensorThe precision of measurements was determined by evaluating

inter and intra assay precision. To estimate the former we recordedthe I–V characteristics for picric acid (0.02 g) with three different

0 1 2 3 4 50

1

2

3

4

5

6(a)

Curr

ent

(A X X

XX 1

0-4)

Applied bias (V)

in air

in nitrobenzene

reversibility

0 1 2 3 4 50.0

0.3

0.6

0.9

1.2(c)

Cu

rren

t (A

1

0-4)

Applied bias (V)

in air

in nitrobenzene

reversibility

0 1 2 3 4 50.0

0.5

1.0

1.5

2.0

2.5(b)

Cu

rren

t (A

1

0-3)

Applied bias (V)

in air

in picric acid

reversibility

0 1 2 3 4 50.0

0.5

1.0

1.5

2.0(d)

Curr

ent

(A

10

-4)

Applied bias (V)

in air

in picric acid

reversibility

Fig. 5. I–V characteristics of (a) PCUMA in nitrobenzene, (b) PCUMA in picric acid, (c) PCUA in nitrobenzene and (d) PCUA in picric acid done at 100 Hz.



Fig. 6. Schematic representation of the sensing mechanism.

0 1 2 3 4 5

0

5

10

15

20

25(a)

Curr

ent

(A X

10

-4)

Applied bi as ( V)

in 0.02g

in 0.04g

in 0.06g

in 0.08g

in 0.1g

in 0.12g

in 0.14g

0.00 0.05 0.10 0.15

0.0

2.5

5.0

7.5

10.0

12.5

(b)

Curr

ent

(A X

10

-4)

Picric a cid (g)

Fig. 7. (a) I–V characteristics of PCUMA at different amounts of picric acid and (b) Calibration curve for PCUMA.

detectors (inter) and for the later three replicate measurementswere done with a single detector (intra). Now t-test on these resultsshowed that at level 0.05, the two means of all the I–V charac-teristics are not significantly different in both the inter and intraassay. But these characteristics before and after sensing are signif-icantly different. Also the RSD were found to be 5.96% and 5.58%respectively. So, the measurements are precise and give repro-ducible results. The plots and the results of t-test are given in ESIFigure S5 (a) and (b) and Table-S1 (a) and (b). The stability of thesensor was determined by performing sensing experiment witha single detector for three consecutive days. There is only about7.2% decrease in the current density in between day 1 and day 3measurements (ESI Figure S6). So, the sensor is stable.

The response of the sensor is also compared with the data avail-able on similar works. In a recent article [31], the response timefor sensing nitro group is reported to be about 10 min at an exper-imental temperature of 250 ◦C. But practically, high temperatureshould not be applied as even unreactive chemicals may becomeexplosive at such temperature. The device at this high temperature

shows an increase of one order resistance typically from around104–105 k�. At lower temperature (50 ◦C) this increase is even verysmall. Pochekailov et al. [32] reported room temperature sensorsbut the response time is about one hour although it showed twoorder increases in conductivity at higher NO2 conc. In another workR. Blue et al. [33], observed 35 fF (i.e. 35 × 10−15 F in presence of90 ppm of nitrobenzene) increases in capacitance, which is neg-ligibly small. Compared to these, results obtained by our methodare appreciable as we observed one order decrease in log Z val-ues i.e. 10-fold decreases in Z value and 90.44% increase in currentdensity in presence of picric acid at room temperature. So unlikethese devices our device is novel as it is very simple, gives pre-cise results, room temperature operating and requires less responsetime.

4. Conclusion

The present study includes the synthesis and characterizationof bio-based polymers PCUMA and PCUA obtained from curcumin.



We successfully determined their chemical sensitivity towardspicric acid and nitrobenzene. PCUMA is found to be more effec-tive as nitroaromatic vapor sensor than PCUA as confirmed byconductivity measurements such as impedance response and I–Vcharacteristics.

The polymer is found to be a good detector for nitroaromaticcompound at room temperature. Graft polymerization and copoly-merization is also possible due to the presence of the aromatic ringsin the monomer, which may lead to another new nitroaromatic sen-sor with better response. The same detector that we prepared canbe used for sensing different nitroaromatic compounds showinggood reversibility, which is another advantage of the sensors. Ourcurrent interest revolves around the changes in conductivity anddielectric properties, which enhances the chemical sensing abil-ity of the prepared polymer. In a nutshell, the main goal of thisendeavor is the successful synthesis of the two novel polymers ofcurcumin, one of which can be employed for selective detection ofnitroaromatic chemicals. The novelty of this work also comes fromthe development of a very simple, portable, low costs and roomtemperature chemical sensor for nitroaromatic detection devoid ofusing any sophisticated instruments which are generally used forsuch purposes.

Acknowledgement

Authors are thankful to DeitY, Govt. of India for financialsupport.

Appendix A. Supplementary data

Supplementary data associated with this article can be found, inthe online version, at http://dx.doi.org/10.1016/j.snb.2013.01.071.

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Biographies

Bedanta Gogoi a junior research fellow in the polymer laboratory, physical sciencedivision, IASST. His field of interest is on polymer based chemical sensors. He hascompleted his M.Sc. degree from Gauhati University, Department of Chemistry in2011 and joined this lab in October 2011.

Priyanka Dutta is a junior research fellow, in the same lab. Her field of interest ison liquid crystalline polymers. She has completed his M.Sc. degree from GauhatiUniversity, Department of Chemistry in 2008 and joined this lab in March 2011.

Niloy Paul is a junior research fellow in the same lab. He is working on the influenceof heterocyclic compounds on polymer based chemical sensors. He has completedhis M.Sc. degree from Gauhati University, Department of Chemistry in 2010 andjoined this lab in March 2011.

Dr. Narendra Nath Dass was a Lecturer in Cotton College from 1964 to 1966. A goldmedalist of Gauhati University has his Ph.D. degree from the University of Londonand DIC from Imperial College in 1969. He then joined Dibrugarh University as a



Lecturer in 1969 and became a Professor in 1985. He taught Physical Chemistry,Polymer Chemistry, Group theory and Petrochemicals in Dibrugarh University upto 2002 when he took over the assignment of the Director ship of IASST. He wasa visiting fellow in Queen’s University, Belfast (1990–1991). Professor Dass so farpublished 150 scientific papers in National and International Journals and produced24 PhDs.

Dr. Neelotpal Sen Sarma did his Ph.D. in the year 2001 and joined IASST in the year2002. He did his M.Sc. from Dibrugarh University, M.Tech. from Indian Institute ofScience, Bangalore and Pet. Tech. diploma from Dibrugarh University. His researchinterest is on LC polymers, Solid state ionics, Hydrogels, Nanocomposits, Biosorbentsetc. and he so-far published 36 research papers in International Journals and appliedfor three patents.

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