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Sensors and Actuators B 255 (2018) 1655–1662

Contents lists available at ScienceDirect

Sensors and Actuators B: Chemical

jo ur nal home page: www.elsev ier .com/ locate /snb

igh performance electrochemical electrode based on polymericomposite film for sensing of dopamine and catechol

ueyue Qiana,1, Chuang Maa,1, Shupeng Zhanga,∗, Juanjuan Gaoa, Maoxiang Liua,angjun Xiea, Shuang Wanga, Kuan Sunb,∗, Haiou Songc,∗

School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094, PR ChinaMOE Key Laboratory of Low-grade Energy Utilization Technologies and Systems, School of Power Engineering, Chongqing University, Chongqing 400044,R ChinaState Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, PR China

r t i c l e i n f o

rticle history:eceived 1 June 2017eceived in revised form 12 August 2017ccepted 23 August 2017vailable online 31 August 2017

eywords:

a b s t r a c t

A highly conductive and electrochemically active film has been successfully fabricated by combiningbeta-cyclodextrin with acid-treated poly(3, 4-ethylenedioxythiophene):polystyrene (denoted as CD-f-PEDOT:PSS). The unique properties of the high performance CD-f-PEDOT: PSS sensor was investigatedby utilizing X-ray photoelectron spectroscopy, atomic force microscope, cyclic voltammetry and amper-ometric i-t, etc. The CD-f-PEDOT:PSS film exhibits high-sensitivity towards dopamine (DA) and catechol(CT) without employing expensive noble metal or indium tin oxide (ITO) substrate and consuming much

ensorEDOT:PSSolymeric filmyclodextrin

more time to polish the surface of traditional electrodes. The detection limits (S/N = 3) for DA and CT inphosphate buffer solutions (PBS, pH = 7.4) are 9.596 nM and 0.0275 �M, respectively. Furthermore, theCD-f-PEDOT: PSS film sensor exhibits good anti-interference and reproducibility. The encouraging resultsas well as facile preparation method suggest the CD-f-PEDOT: PSS film sensor is a promising alternativeelectrode to traditional ones such as ITO, gold or glassy carbon electrodes.

© 2017 Elsevier B.V. All rights reserved.

. Introduction

Electrochemical detection is fast, sensitive, clean and accurateompared to many other detection methods, thus it has beenpplied to many aspects of our life [1]. Glassy carbon electrodeGCE) is the most popular electrode due to its good electricalonductivity, high chemical stability, and wide potential range2]. However, the pre-treatment of GCE can be tedious and time-onsuming. Subsequently, indium tin oxide (ITO) glass electrodend carbon paper electrode have been developed as two impor-ant alternatives to GCE. The ITO electrode exhibits excellentpto-electronic properties, and finds applications in solar cells,ight-emitting diodes, touch panel displays and biosensors [3]. ButTO is expensive due to limited indium source on earth [4]. More

mportantly, the electroanalytical activity of ITO is relatively low,hus surface modification is commonly required. Up to date, metalanoparticles, metal oxide, conducting polymers, carbon materials

∗ Corresponding authors.E-mail addresses: shupeng 2006@126.com (S. Zhang), kuan.sun@cqu.edu.cn

K. Sun), songhaiou2011@126.com (H. Song).1 Y.Y. Qian and C. Ma contributed equally to this work.

ttp://dx.doi.org/10.1016/j.snb.2017.08.174925-4005/© 2017 Elsevier B.V. All rights reserved.

and composites have been introduced for ITO surface modification[5]. For example, Fu used ion implantation technique to depositgold nanoparticles (Au NPs) on ITO, allowing for the detection ofglucose [6]; Ding realized the sensitive detection of copper ionswith the ITO/Au NPs electrode [7]; in-situ growth of microporousZnO nanorods on ITO also enhanced the electrochemical behavior[8]. However, there are concerns about the interface stability andbrittleness of ITO, which might hinder practical applications [9].The carbon paper electrodes that mainly constitute of grapheneand/or carbon nanotubes can be free-standing and flexible [10].But the carbon paper electrodes suffer from low conductivity andlow density of active sites for catalysis [11],thus reduction orselectively chemical doping were explored [12,13]. For example,KaderDagcı prepared graphene/Ag nanoparticles/poly(pyronin Y)hybrid paper electrode for effective nitrite detection [14]; Sunprepared graphene paper electrode decorated with Pt/Pd alloynanoparticles for electrochemical catalysis and sensing [8].

It is clear from the above-mentioned examples, ITO or carbonpaper mainly acts as a conducting substrate, surface modification

or decoration are often required for the application of electro-chemical detection [15]. It is significant to develop new electrodematerials that are both highly conductive and highly active incatalysis, and preferably stable and flexible to suit wider appli-

1656 Y. Qian et al. / Sensors and Actuators B 255 (2018) 1655–1662

of PEDOT:PSS and ˇ-cyclodextrin.

c(icp[ttoti

sAPp[wtaidkPmmt

2

2

(PPfsCK(Cp0u

2

aw

Fig. 1. Chemical structures

ations. Poly(3,4-ethylenedioxythiophene):polystyrene sulfonatePEDOT:PSS, chemical structure is shown in Fig. 1) is a conduct-ng polymer that is cheap, solution processible, chemically stable,onductive, flexible and transparent [13,16,17]. These brilliantroperties provide it great potential in electrochemical devices18]. Though GCE coated with PEDOT: PSS film realized the detec-ion of hydrazide, nitrite, and salicylic acid [19], it is still challengingo utilize neat PEDOT:PSS films without any conducting substrater plasticizer, as the film can be dissolved in water after certainime duration. Furthermore, the inherent electrochemical propertys poor for the PEDOT: PSS [20].

Here we introduce neat PEDOT:PSS film coated on glass sub-trate as an alternative electrode for electrochemical detection.fter post-treatment of concentrated H2SO4 (CSA), the PEDOT:SS film became more conductive and hydrophobic due to theartial removal of the insulting and hydrophilic PSS component21,22]. The resultant film, which is denoted as CSA-t-PEDOT:PSSas subsequently immersed in ˇ-cyclodextrin (CD, chemical struc-

ure is shown in Fig. 1) solution to create more electrochemicallyctive sites by supramolecular self-assembly. The CD functional-zed PEDOT:PSS film (CD-f-PEDOT:PSS) could realize ultrasensitiveetection of dopamine (DA) and catechol (CT). To the best of ournowledge, this is the first time we demonstrate a functionalizedEDOT:PSS film can realize highly sensitive and selective deter-ination without employing any expensive ITO glass and nobleetals and consuming much more time to polish the surface of

raditional electrodes.

. Experimental

.1. Chemicals and materials

PEDOT:PSS aqueous solution was purchased from Sigma AldrichConductive grade, Lot No. WXBB6393 V). The concentration ofEDOT:PSS was 1.3% by weight, and the weight ratio of PSS toEDOT was 8:5 in solution. ˇ-cyclodextrin (CD) was purchasedrom Aladdin Chemistry Co., Ltd. (Shanghai, China). Concentratedulfuric acid (H2SO4, CSA)was purchased from Nanjing Chemicalompany. NaH2PO4 (≥99.0%), Na2HPO4 (99%), K3Fe(CN)6 (≥99.5%),4Fe(CN)6 (99%), KCl (99.5%) and dopamine (DA, 98%) and catechol

CT) were purchased from Aladdin Chemistry Co., Ltd (Shanghai,hina). DA and CT solutions were prepared fresh prior to use. Phos-hate buffer solutions (PBS) (0.1 M, pH 7.4) were prepared using.1 M Na2HPO4 and 0.1 M NaH2PO4. And doubly distilled water wassed throughout. All the materials were used as received.

.2. Treatment of PEDOT:PSS films

PEDOT:PSS films were prepared by spin coating the PEDOT:PSSqueous solution (3000 rpm/min) on 1.2 × 1.2 cm2 glass substrate,hich were pre-cleaned successively with detergent, de-ionized

Scheme 1. The fabrication process of the CD-f-PEDOT:PSS.

(DI) water, acetone for three times before use. The PEDOT:PSS filmswere dried at room temperature for about 5 min. Then The CSAtreatment was performed by dropping 100 �L concentrated H2SO4on a PEDOT:PSS film on a hot plate at 120 ◦C. The film lasted forabout 15 min, and then they were rinsed with DI water twice topractically remove the PSS and dried at 120 ◦C again. Finally, CSA-treated film (CSA-t-PEDOT:PSS) can be achieved.

2.3. Preparation of CD-functionalized PEDOT:PSS films

The obtained CSA-treated PEDOT:PSS film was immersed inˇ-CD aqueous solutions with various concentrations for about40 s. The CD-functionalized PEDOT:PSS films (CD-f-PEDOT:PSS)were dried at 120 ◦C. The detailed fabrication process of the CD-f-PEDOT:PSS is shown in Scheme 1.

2.4. Characterization of PEDOT:PSS films

The AFM images of the polymer films were obtained using aVeecoNanoScope IV Multi-Mode AFM (Bruker, German) with thetapping mode. X-ray photoelectron spectroscopy (XPS) analysiswas obtained using PHIQuantera II with C60 high resolution spec-trometer with a monochromatized Al Ka X-ray source (1486.71 eVphotons) to analyze the chemical composition of the materials.Sheet resistances were measured by the van der Pauw four-point

probe method with a Keithley 2400 source/meter. The electricalcontacts were made by pressing indium on the four corners of eachPEDOT:PSS film on a glass substrate.

Y. Qian et al. / Sensors and Actuators B 255 (2018) 1655–1662 1657

T:PSS

2

(cE(e(to

3

3

guaioifimPmrtlsingBiae

wfimPabw1

Fig. 2. (a) XPS spectra of untreated PEDOT:PSS and CSA-t-PEDO

.5. Electrochemical performance

All electrochemical experiments including cyclic voltammetryCV), differential pulse voltammetry (DPV) and electrochemi-al impedance spectra (EIS) were carried out with a CHI660Electrochemical Workstation from Shanghai Chenhua InstrumentShanghai, China). The conventional three-electrode cell wasmployed with platinum wire and a saturated calomel electrodeSCE) as the auxiliary electrode and the reference electrode, respec-ively, the PEDOT:PSS, CSA-t-PEDOT:PSS and CD-f-PEDOT:PSS filmsn the glass as working electrode.

. Results and discussion

.1. Conductivity enhancement of CSA-induced PEDOT:PSS films

The electrical properties of PEDOT:PSS (Fig. 1) were investi-ated after post-treatment with concentrated H2SO4 (CSA). Thentreated PEDOT:PSS films have a sheet resistance of 35 k� sq.−1,nd a conductivity of ∼1 S cm−1. The sheet resistance was signif-cantly decreased after the CSA treatment. Lower sheet resistancef 230 � sq.−1 was observed for the CSA-t-PEDOT: PSS, correspond-ng to a conductivity of about 320 S cm−1. Treatment of PEDOT: PSSlms with CSA can greatly enhance the conductivity. Such enhance-ent is attributed to a significant structural rearrangement in the

EDOT: PSS with the removal of PSS, which is possibly due to for-ation of the crystallized nano-fibrils [23]. Moreover, the sheet

esistance of CD-f-PEDOT: PSS is 640 � sq.−1, which is gently higherhan that of CSA-t-PEDOT:PSS owing to the introduction of insu-ating ˇ-cyclodextrin (CD). CD is an oligosaccharide composed ofeven glucose units, which is toroidal in shape with a hydrophobicnner cavity and a hydrophilic exterior (Fig. 1). CDs have fasci-ating supramolecular recognition ability, which can bind variousuest molecules selectively to form stable host-guest complex [24].esides, CDs are environmentally friendly, water-soluble, and can

mprove the solubility and biocompatibility of functional materi-ls [25]. So it is promising that CD-f-PEDOT:PSS film will exhibitlectrochemical performance.

The loss of PSS from PEDOT:PSS films after the CSA-treatmentas confirmed by X-ray photoelectron spectroscopy (XPS). The sul-

ur atom in PSS is within the sulfonate moiety, whereas in PEDOT,t is included in the thiophene ring. Different chemical environ-

ents lead to different binding energy for the S (2p) electrons ofSS and PEDOT. Fig. 2a shows the S 2p XPS fine scans of untreated

nd CSA-t-PEDOT: PSS films. The doublet peak with binding energyetween 166 and 172 eV are ascribed to the sulfur atoms in PSS,here as the two XPS bands with binding energy between 162 and

66 eV are associated with the sulfur atoms in PEDOT [26,27]. The

; (b) S 2p XPS spectra of untreated and CSA-t-PEDOT:PSS films.

significant reduction of S2p peak intensity ratio of PSS to PEDOTsuggests the partial removal of PSS from the PEDOT:PSS film afterthe CSA treatment. In the XPS survey scans (Fig. 2b), the S2p peak isalmost disappeared for the CD-f-PEDOT: PSS sample. Because XPSis a surface characterization technique with probing depth of onlya few nanometers, the absence of S2p signal in CD-f-PEDOT:PSSsuggests that CD molecules have covered the entire surface of theCSA-t-PEDOT:PSS films, which would benefit for the increase ofelectrochemical response by supramolecular recognition towardsanalytes.

The surface roughness and morphology also play an importantrole in adjusting the performance of the film sensor. The surfacemorphology of the PEDOT:PSS film changes after the CSA treat-ment, as revealed by the AFM images (Fig. S1). The untreatedPEDOT:PSS film consists of mainly polymer particles. On the con-trary, these polymer particles turn into entangled wires with adiameter of tens of nanometers after the CSA treatment. The con-ductive nanowires can promote the charge hopping in comparisonto the particles. The root mean square roughness (Rrms) values are11.82, 12.64 and 0.41 nm for the untreated, CSA-t-PEDOT:PSS andCD-f-PEDOT:PSS films, respectively. The relatively smooth surfaceof the CD-f-PEDOT:PSS film is attributed to the complete cover-age of CD molecules onto the surface of CSA-t-PEDOT:PSS, which isbeneficial to supramolecular recognition and electrocatalytic per-formance.

3.2. Electrochemical properties

The electrochemical properties of the film sensors were char-acterized by cyclic voltammetry (CV), electrochemical impedancespectra (EIS), and amperometric i-t curve tests. The relationshipbetween electrochemical response and electrode area was pre-sented in Fig. S2. The electrochemical current increases with theincrease of detection area that immersed in detection solution.A linear regression equations could be derived as I (�A) = 35.3S(cm2) − 3.53 (R = 0.9908). So the normalized current density canserve as an indicator forelectrocatalytic activity; and all theobtained current densities should be normalized with the electrodearea for fair comparison.

In order to optimize the electrocatalytic performance, the CD-f-PEDOT: PSS films were constructed by immersing it in CD ofdifferent concentrations. The properties of each electrode wereinvestigated by CV in 0.1 M PBS (pH 7.4) containing 50 �M DA orCT. The corresponding CV behaviors and the bar diagram of Faradaiccurrent are shown in Fig. 3a–d. By comparing the faradaic currents,

it is clear that the best CD concentration is 0.01 g/mL for DA or CTdetection. The excess insulated CD would decrease the conductiv-ity of electrochemical sensors and hinder electron transportation;while low CD concentration would lead to reduction of supramolec-

1658 Y. Qian et al. / Sensors and Actuators B 255 (2018) 1655–1662

Fig. 3. The cyclic voltammogram (CV) curves and the corresponding bar diagram of Faradaic current of the obtained CD-f-PEDOT:PSS films by immersing into CD solutionsw PBS (pe an rat( Hz.

upottw

asf5

ith different concentrations in the presence of 50 �M DA (a and b) or CT (c and d) inlectrode including CD-f-PEDOT:PSS, CSA-t-PEDOT:PSS and GCE in PBS (pH 7.4); sc1:1) containing 0.1 M KCl solution. The frequency region was from 1000 KHz to 0.1

lar recognition activity towards analytes. Fig. 3(e) compares theerformance of different types of electrodes. The faradaic currentsf CD-f-PEDOT: PSS for DA is significantly higher than that of CSA--PEDOT:PSS and bare GC electrode. Such observation is attributedo the synergetic effect of high conductivity of CSA-t-PEDOT:PSS asell as good supramolecular recognition ability provided by CD.

Electrochemical impedance spectroscopy (EIS) is considereds an effective tool to investigate the interfacial properties of

urface-modified electrodes. The conductivity and electron trans-er properties of different electrodes were investigated by EIS in.0 mM Fe(CN)6

3−/4− containing 0.1 M KCl. The electron-transfer

H7.4) as a scan rate 50 mV s−1; (e) the CV behaviors for DA detection at the differente: 50 mV s−1; (f) the EIS plots of GCE, and CD-f-PEDOT:PSS in 5.0 mM Fe(CN)6

3−/4−

resistance (Rct) at the electrode surface is equal to the semi-circle diameter of EIS at higher frequencies and can be used todescribe the interface properties of the electrode. A linear por-tion at lower frequencies represents the diffusion limited processand the high frequencies correspond to the charge transfer lim-iting progress [53]. Fig. 3f indicates the results of the impedancespectrum on a bare GCE, PEDOT:PSS, CD-f-PEDOT:PSS. The semi-circle of PEDOT:PSS decreases relative to the bare GCE electrode.

This is mainly due to PEDOT: PSS is a conductive polymer, whichwould promote the electron transfer on the film. After PEDOT: PSSis functionalized by CD, the semicircle of CD-f-PEDOT:PSS signifi-

Y. Qian et al. / Sensors and Actuators B 255 (2018) 1655–1662 1659

Table 1Comparison of different chemically modified electrodes for the determination of DAwith CD-f-PEDOT: PSS film sensor.

Sensing materials Linear responserange (�M)

Limit ofdetection(�M)

Ref.

�-WO3/GCE 0.1–600 0.024 [28]GO@MWNTs-NiNC. 0.03–80 0.012 [29]PPy/CNTs-MIPs 5–50 1 [30]Cu2O HMS/CB/GCE 0.099–708 0.0396 [31]B-N CDs 1–1000 0.1 [32]PEDOT/GO 0.1–175 0.039 [33]PEDOT–CNT–Ty 100–500 2.4 [34]ZnO QDs 0.05–10 0.012 [35]ERGO/GCE 0.5–60 0.5 [46]Pd/CNFs 0.5–160 0.2 [47]PPyox/SWNTs/GCE 20–1000 0.38 [48]GNP/Ch/GCE 0.2–80 0.2 [49]CdSe QDs/PDDA-GN/AuNPs 0.1–1000 0.1 [50]CNF-CPE 0.04–5.6 0.04 [51]

citGfitecgcfm

aiorsb((b

tCdsoropw(dellamwPi

ioe

Table 2Comparison of different chemically modified electrodes for the determination of CTwith CD-f-PEDOT: PSS film sensor.

Sensing materials Linear responserange (�M)

Limit of detection(�M)

Ref.

PARS/BMIMBF4 film/GCE 0.10–500 0.026 [36]CNNS-CNT. 1–200 0.09 [37]AuNPs/Fe3O4-APTES-GO 2–145 0.8 [38]Ru-MWNTs-PA6 0.002–2 0.001 [39]CdSe@ZnS QDs/GEs 0.005–1 0.002 [40]Pt-Au-OSi@CS 0.06–90.98 0.02 [41]GR–TiO2/GCE 0.5–100 0.087 [42]

P3MT/AuNPs 1–35 0.24 [52]CD-f-CSA-PEDOT:PSS 0.05–200 0.009596 This work

antly increases relative to the PEDOT:PSS electrode, indicating thatnsulating CD layer reduce the interfacial charge transfer [54]. For-unately, The almost identical Rct values of CD-f-PEDOT: PSS andCE imply that the electron transfer between the CD-f-PEDOT: PSSlm electrode and the electrolyte is as efficient as that of the tradi-ional GCE. CDs with a hydrophobic inner cavity and a hydrophilicxterior have fascinating supramolecular recognition ability, whichan bind selectivity various guest molecules to form stable host-uest complex. A number of CDs onto the surface of PEDOT:PSSan enhance the sensitivity of detection for DA and CT through theormation of supramolecular complexes between CDs and guest

olecules.Scan rate can possibly influence the electrochemical response of

nalytes. The CVs of the CD-f-PEDOT:PSS film at various scan ratesn PBS containing DA are shown in Fig. 4a. The current densitiesf oxidation and reduction peaks increase with the increasing scanates. The peak currents increased linearly with the square root ofcan rates in the range of 20–75 mV s−1, which can be describedy the following equations: Ip (�A) = −17.34802 + 12.06783 �1/2

mVs−1) (R = 0.9998), Ip (�A) = 16.8663 − 10.52781 �1/2 (mVs−1)R = 0.9978), demonstrating that the oxidation and reduction of DAelong to diffusion controlled process (Fig. 4b).

The constructed CD-f-PEDOT: PSS film sensor was employedo investigate the electrocatalytic performance towards DA andT by amperometric i-t method [43,45]. As shown in Fig. 4c and, the current generated from the CD-f-PEDOT: PSS film sen-or exhibited a ladder rising pattern after successive additionf DA or CT into the stirring PBS solution. A fast amperometricesponse of less than 1 s was recorded. Interestingly, when the DAr CT concentration is less than 40 �M, the current-concentrationlots (Fig. 4(d) and (f)) show the linear regression equations,hich is Ip,1 (�A) = 0.1770 + 0.4869C1 (�M) (R = 0.998) and Ip,1

�A) = 0.12146 + 0.36327C1 (�M) (R = 0.9991), respectively. In theetection range from 40 to 200 �M, the plots evolved into curvilin-ar lines that could be described by equations: Ip,2 (�A) = 10.2661n(C2-13.9996)-14.4283 (�M) (R = 0.9996) and Ip,2 (�A) = 21.90116n(C2 + 4.99316)-69.37045 (�M) (R = 0.9987), respectively for DAnd CT. So, the LOD values for DA and CT determination were deter-ined to be 9.596 nmol/L and 0.0275 �mol/L (S/N = 3). Comparedith those reported DA and CT sensors (Tables 1 and 2), the CD-f-

EDOT: PSS film sensor shows superior electrochemical propertiesncluding low detection limit and wide detection range.

During chemical detection, it is of significance to overcomenterference by other chemicals. The anti-interference propertiesf CD-f-PEDOT:PSS film sensor have been investigated. In a typicalxample, 1 �M CT was added twice, followed by adding 1000 �M

GO@PDA–AuNPs 0.3–67.55 0.015 [44]CD-f-CSA-PEDOT:PSS 0.05–200 0.0275 This work

of KCl, NaNO3, MgSO4, CaCl2 and 100 �M of glucose or AA sequen-tially. After that, 1 �M CT was added twice again. The amperometrici-t plot of this experiment was presented in Fig. S3A. There areobvious changes in current response when CT was added into thesolution. And these changes can quickly reach a stable value. On thecontrary, after adding other chemicals even in much higher con-centrations, no obvious change in the current can be probed. Theseobservations support that CD-f-PEDOT:PSS film sensor has excel-lent selectivity and anti-interference property for CT detection.

To investigate the cycling stability of the film sensor, the cyclicvoltammetry was carried out for 150 cycles. Fig. S3B showed thecyclic voltammograms for CD-f-PEDOT:PSS film sensor at the 1st,80th and the 150th cycles. Clearly, the film sensor showed goodstability in the detection process. The stability indicates that thefilm can support longtime detection. The reproducibility was alsoinvestigated by utilizing five CD-f-PEDOT:PSS film sensors in thesame conditions, and the RSD values are 2.25% and 2.93% for DAand CT, respectively, indicating a good reproducibility (Fig. S4). Allthese observations indicate that CD-f-PEDOT:PSS film sensor hassatisfactory stability and reproducibility.

3.3. Real sample measurements

An excellent sensor should also be able to detect the real sample.CD-f-PEDOT:PSS film sensor was used to determine the concen-trations of DA in human serum sample and CT in tap water, riverwater from Nanjing city by standard addition method for practi-cal application, respectively (Table S1). Before measurement, theserum samples were diluted 100 times with PBS (pH 7.4) with-out no other pretreatment. It is found that the results obtained byi-t curves were in good agreement with the actual addition withthe recovery from 99.4%, 99.72% to 100.23%, indicating potentialfor practical DA and CT detection. Compared with the traditionalUV–vis spectrophotometry, it is clear that the recoveries of theproposed electrochemical method which is in good accordancewith the ranges obtained by the UV–vis spectrophotometry. Theseresults indicate that the proposed method is reliable and it haspotential for practical application.

4. Conclusions

In summary, we presented a film sensor based on ˇ-cyclodextrinfunctionalized poly(3,4-ethylenedioxythiophene):polystyrene(CD-f-PEDOT:PSS), whose conductivity was enhanced by acidtreatment. Such a film sensor could be realized by low-costand high-throughout solution processing, and it did not employexpensive ITO or graphene as conductive substrate. A series of

electrochemical tests indicated the film sensor exhibited fastresponse, low detection limit and wide detection range towardsdopamine or catechol detection. Its performance is even betterthan traditional GCE and many alternative electrodes presented

1660 Y. Qian et al. / Sensors and Actuators B 255 (2018) 1655–1662

F tes (2i (e) frA es for

itCpd

C

A

t

ig. 4. (a) CVs obtained for DA (50 �M) at the CD-f-PEDOT:PSS film at different scan ra-t curve of CD-f-PEDOT:PSS film sensor towards successive additions of DA (c) or CTmperometric response from 0 to 400 s (inset); the corresponding calibration curv

n literature. Besides, the film sensor also shows superior selec-ivity and long-term stability. The above-mentioned merits of theD-f-PEDOT:PSS film sensor suggests functionalized conductingolymer films having great potential in the field of electrochemicaletection.

onflict of interest statement

There is no conflict of interest about this article.

cknowledgments

This work was supported by the Natural Science Founda-ion of China (51402151, 51408297, 61504015, 51778281); the

0–75 mV s−1) in PBS (pH 7.4); (b) shows the resulting calibration plot; Amperometricom 0.05 to 200 �M at the applied potential of + 0.25 V at a rotation rate of 200 rpm;DA (e) and CT (f) detections.

Natural Science Foundation of Jiangsu province (BK20161493,BK20171342) and Major Science and Technology Programfor Water Pollution Control and Treatment, PR China (No.2014ZX07214-001); the QingLan Project, Jiangsu Province; andthe Zijin Intelligent Program, Nanjing University of Science andTechnology; Fundamental Research Funds for the Central Univer-sities (30917011309); A Project Funded by the Priority AcademicProgram Development of Jiangsu Higher Education Institutions(PAPD).

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.2017.08.174.

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Haiou Song obtained her Doctor Degree from Jilin University under the supervisionof Prof. Vivian Wing-Wah YAM. As a Postdoctoral Fellow, she joined Prof. Aimin Li’sgroup at Nanjing University in 2010. Now she is an Associate Researcher in Schoolof Environment, Nanjing University. Her current research interests are pollutioncontrol and resources reuse of toxic pollutant utilizing hybrid materials.

662 Y. Qian et al. / Sensors and A

AuNPs and Au nanoparticles@PDDA-graphene as amplifier, Sens. Actuators B243 (2017) 121–129.

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54] H. Guo, Y. Guo, J. Ren, Y. Zhai, S. Dong, E. Wang, Graphene hybrid nanosheetswith high supramolecular recognition capability: synthesis and host-guestinclusion for enhanced electrochemical performance, ACS Nano 4 (2010)4001–4010.

iographies

ueyue Qian has received her postgraduate degree from Nanjing University of Sci-nce and Technology under the supervision of Associate Prof. Shupeng Zhang (2017).he received her B.S. degree from the same university.

huang Ma is a graduate student at Nanjing University of Science and Technology.is research interest is the application of PEDOT:PSS.

hupeng Zhang obtained his Doctor Degree from Sichuan University in 2009. As visiting scholar, he joined Prof. Jianyong Ouyang’s group at National Univer-

ity of Singapore, Prof. Aimin Li’s group at Nanjing University in 2014 and 2016,espectively. Now he is an Associate Professor in School of Chemical Engineer-ng, Nanjing University of Science and Technology. His current research interestsre electrochemical determination and removal of pollutant utilizing carbon-basedanomaterials.

rs B 255 (2018) 1655–1662

Juanjuan Gao is currently studying for a Ph.D. degree at Nanjing University of Sci-ence and Technology. Her scientific interests focus on electrochemical applicationsof carbon-based hybrid nanomaterials.

Maoxiang Liu got a Master Degree under the supervision of Associate Prof. ShupengZhang at Nanjing University of Science and Technology. He received his B.S. degreefrom the same university (2014).

Kangjun Xie is a graduate student at Nanjing University of Science and Technology.His research interest is the application of nanomaterials.

Shuang Wang is a graduate student at Nanjing University of Science and Technology.She received her B.S. degree from Nanjing Forestry University. Her main researchtopic is the application of multicomponent nanocomposites in electrochemical sen-sors under the supervision of Associate Prof. Shupeng Zhang.

Kuan Sun is a tenure-track Assistant Professor at the School of Power Engineeringin Chongqing University, China. He received B.Appl.Sci. (Hon.) and Ph.D. degreesfrom the National University of Singapore (NUS), and post-doc trainings at the Uni-versity of Melbourne and NUS. He was also a visiting scholar at Karlsruhe Instituteof Technology and Max-Planck Institute for Polymer Research. His research focuseson printable solar cells, transparent electrodes as well as novel functional materialsand devices.

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