Fabrication of multiwalled carbon nanotubes polypyrrole Prussian blue ternary composite nanofibers
Fabrication of multiwalled carbon nanotubes/polypyrrole/
Prussian blue ternary composite nano?bers and their application for enzymeless hydrogen peroxide detection
E.Jin ?Xiujie Bian ?Xiaofeng Lu ?Ce Wang
Received:20December 2011/Accepted:18January 2012/Published online:31January 2012óSpringer Science+Business Media,LLC 2012
Abstract In this article,Prussian blue (PB)covered mul-tiwalled carbon nanotubes (MWCNTs)/polypyrrole (PPy)ternary composite nano?bers with good dispersibility in water and ethanol have been prepared by directly mixing ferric-(III)chloride and potassium ferricyanide in the pres-ence of MWCNT/PPy coaxial nano?bers under ambient conditions.Transmission electron microscopy shows that the as-synthesized PB nanoparticles covered on the surface of MWCNT/PPy nano?bers.Fourier-transform infrared spectroscopy,UV–Visible spectroscopy,and X-ray diffrac-tion patterns have been used to characterize the obtained MWCNT/PPy/PB ternary composite nano?bers.The MWCNT/PPy/PB ternary composite nano?bers exhibit good electrocatalytic response to detection of H 2O 2and provide a new material to modify electrode for amperometric biosensors.
Introduction
Multiwalled carbon nanotubes (MWCNTs)became a new kind of nanomaterials and received considerable interest due to their unique electronic properties,good chemical stability,high surface-to-volume ratio and extremely high mechanical strength and stiffness.They have promising applications in nanodevices [1],nanoprobes [2],bioelec-tronics,and sensors [3–8].Composite materials composed
of MWCNTs and conducting polymers have been exten-sively investigated in the past few years,mainly because of their wide potential applications,from supercapacitors to gas sensors [9–13].Among various intrinsic conducting polymers,polypyrrole (PPy)has potential uses in synthe-sizing polymer/MWCNT composites because of its envi-ronmental stability,good electrical conductivity,and relative ease of synthesis [14,15].
On the other hand,potassium iron(III)hexacyanofer-rate(II)or Prussian blue (PB)has been extensively studied for its attractive magnetic,electrochromic and electro-chemical properties and widely applications in the ?eld of catalysis,solid-state batteries,electrochromic devices,and biosensors [16–20].Especially,PB nanomaterials exhibit good performance for H 2O 2electroreduction,such as high sensitivity,low detection limit,and wide linear range.They have been extensively used as biosensor for H 2O 2and glu-cose detection [21,22].PB nanostructures or ?lms could be prepared by the electrochemical or chemical deposition methods [23].For the chemical synthesis of PB nanostruc-tures by the direct reaction between Fe 3?and (Fe(CN)6)4-or Fe 2?and (Fe(CN)6)3-,the reaction is so fast because the solubility constant of PB is very small (K sp =3.3910-41),thus the size of the PB is dif?cult to control.Recent works reported that PB nanoparticles could be synthesized by the reaction between Fe 3?and (Fe(CN)6)3-by adding reducing reagents,such as carbon nanotubes,graphene,or polyani-line,where Fe 3?has been reduced to Fe 2?or (Fe(CN)6)3-has been reduced to (Fe(CN)6)4-.By using this approach,MWCNT/PB,graphene/PB and PPy/PB composites have been synthesized [24–26].But as far as we know,there are few reports on the preparation of MWCNT/PPy/PB ternary composite nano?bers for sensing applications.
In this article,we demonstrated a facile method to ef?ciently prepare MWCNT/PPy/PB ternary composite
E.Jin and Xiujie Bian contributed equally to this study.E.Jin áX.Bian áX.Lu (&)áC.Wang (&)Alan G.MacDiarmid Institute,Jilin University,Changchun 130012,People’s Republic of China e-mail:x?u@https://www.360docs.net/doc/d98867363.html, C.Wang
e-mail:cwang@https://www.360docs.net/doc/d98867363.html,
J Mater Sci (2012)47:4326–4331DOI 10.1007/s10853-012-6283-8
nano?bers by directly mixing Fe3?and(Fe(CN)6)3-in the presence of MWCNT/PPy nano?bers in aqueous solution at room temperature.Furthermore,it was found that the obtained MWCNT/PPy/PB ternary composite nano?bers modi?ed electrode exhibited excellent electrocatalytic activity toward the H2O2reduction.A high sensitivity with a low detection limit based on this sensor was achieved. Experimental
Synthesis of MWCNT/PPy/PB ternary composite
nano?bers
MWCNTs with40–60nm in diameter were used without further treatment as received.The MWCNT/PPy nano?bers were synthesized according to the literature[27].In a typ-ical procedure of synthesis of MWCNT/PPy/PB nano?bers, a ferric aqueous solution(15mL)containing0.0196g FeCl3á6H2O,0.0252g K3Fe(CN)6and0.1116g KCl with pH=1.5(adjust with HCl)was prepared.Then,5mL of the above ferric solution was added into a stirring solution containing MWCNT/PPy nano?bers(5mg)in distilled water(20mL)by ultrasonication dispersion.After6h,the obtained dispersions were centrifuged and washed with water and ethanol for several times,?nally dried in vacuum for one night at40°C.The MWCNT/PPy/PB composite nano?bers could be redispersed in distilled water and eth-anol,which were suitable for further characterization. Fabrication of MWCNT/PPy/PB composite nano?bers modi?ed electrode
The glassy carbon electrodes(GCE,3mm in diameter) were polished subsequently with1.0,0.3,and0.05l m alumina slurry followed by rinsing with doubly distilled water and drying at room temperature.For H2O2reduction reactions,MWCNT/PPy/PB composite nano?bers were dispersed in ethanol to form a2.0mg/mL solution and ultrasonically treated for5min.10l L of this solution was dropped onto the pretreated GCE surface and dried before electrochemical experiments.
Characterization
Transmission electron microscopy(TEM)measurements were made on a JEM-1200EX with an accelerating voltage of100kV.Fourier-transform infrared(FTIR)spectra on sample pellets with KBr were conducted by means of a BRUKER VECTOR22Spectrometer.UV–Vis spectra were obtained using SHIMADZU UV-2501Spectropho-tometer and the samples were dispersed in ethanol to form uniform solutions for the test.X-ray diffraction(XRD)patterns were measured on Siemens D5005(with a Cu K a radiation)instrument.All electrochemical experiments were performed on a CHI660C electrochemical worksta-tion with a conventional three-electrode cell containing 0.1M H3PO4and1.0M KCl solution at room temperature, using platinum wire as the auxiliary electrode,saturated calomel electrode(SCE)as the reference electrode,and the MWCNT/PPy/PB composite nano?bers-modi?ed GCE as the working electrode.
Results and discussion
Morphology and chemical structures of MWCNT/PPy/ PB composite nano?bers
To fabricate MWCNT/PPy/PB composite nano?bers, MWCNTs were?rst covered by PPy shell with thickness about20–40nm(Fig.1a,b).In the following,PB nano-particles were decorated by putting the MWCNT/PPy nano?bers into the solutions containing Fe3?and (Fe(CN)6)3-.
Previous reports have been demonstrated that PB nano-particles could be prepared by directly mixing Fe3?and (Fe(CN)6)3-in the presence of reducing agents.Similar with that,Fe2?may be produced by the electrons transfer from PPy to Fe3?by mixing Fe3?and(Fe(CN)6)3-in the presence of PPy.Then,PB nanoparticles would be formed from the gained Fe2?and(Fe(CN)6)3-and covered on the surface of MWCNT/PPy composite nano?https://www.360docs.net/doc/d98867363.html,pared to the reaction by direct mixing Fe2?and(Fe(CN)6)3-to synthe-size PB,the size and morphology of PB could be well con-trolled by this method.TEM images con?rmed the formation of PB nanoparticles on the surface of MWCNT/PPy nanof-ibers,as shown in Fig.1c and https://www.360docs.net/doc/d98867363.html,pared to the TEM image of MWCNT/PPy nano?bers,it was evident that lots of PB nanoparticles about12–24nm were randomly deposited on the surface of MWCNT/PPy nano?bers.Moreover,the obtained MWCNT/PPy/PB composites nano?bers could be better dispersed in ethanol than MWCNT/PPy nano?bers and gave a homogeneous blue solution(Fig.2a).
Figure2b showed the FTIR spectra of MWCNT, MWCNT/PPy,and MWCNT/PPy/PB composite nano?-bers.After polymerization of pyrrole on the surface of MWCNT,the characteristic absorption bands of PPy were observed.The peaks at1556and1462cm-1corresponded to the fundamental vibration of the pyrrole ring.The peaks at1309,1097,1042cm-1could be assigned to the=C–H in-plane https://www.360docs.net/doc/d98867363.html,pared to the spectrum of MWCNT/ PPy,it could be seen that a strong absorption band around 2085cm-1appeared in MWCNT/PPy/PB composite nanof-ibers,which was the characteristic C–N stretching absorp-tion band in the Fe2?–CN–Fe3?of PB.The absorption
Fig.2a The pictures of the
before and after PB covered;
b FTIR spectra,
c UV–Vis
spectra,and d XRD pattern
of the samples
band at 500cm -1could also be observed,which was attrib-uted to the formation of M–CN–M 0structure (M =metal).Both the bands indicated the formation of PB nanoparticles [28].UV–Visible spectra of MWCNT/PPy and MWCNT/PPy/PB composite nano?bers were shown in Fig.2c.The characteristic absorption peak of PB at 740nm was observed,which was attributed to the charge transfer from Fe 2?to Fe 3?in PB [29].The XRD pattern of the as-synthesized MWCNT/PPy/PB composite nano?bers was shown in Fig.2d.After the formation of PB nanoparticles on the surface of MWCNT/PPy nano?bers,the peaks at 2h =17.3°,24.5°,35.1°,39.4°,43.4°,50.5°,54.0°,57.2°were observed,which could be indexed as pure face-centered-cubic phase of PB (JCPDS card no.73-0687),con?rming the formation of PB nanoparticles [30].Electrochemical performance of the MWCNT/PPy/PB composite nano?bers modi?ed GCE
In the past few years,the detection of low levels of H 2O 2attracted much attention due to its wide application in medical science,environmental control,and many indus-trial processes [21,31–35].In previous reports,PB is considered to be an ‘‘arti?cial enzyme peroxidase’’and could be used for fabricating the biosensors for H 2O 2.Therefore,the gained MWCNT/PPy/PB composite nanof-ibers could be used as a new material for the electro-chemical detection of H 2O 2.
We investigated the MWCNT/PPy/PB composite nano?bers response to detect H 2O 2in a wide range from -0.4to 0.6V (Fig.3).Figure 3a gave the CV curves of bare GCE,MWCNT/PPy,and MWCNT/PPy/PB composite nano?bers modi?ed GCE in 0.1M H 3PO 4and 1.0M KCl solution.Two typical pairs of redox peaks showing the oxidation of PB to Prussian green (PG)as well as the reduction to Prussian white (PW)were observed in the electrodes,indicating the effective presence of PB in the composite.After adding 1.0mM H 2O 2,(Fig.3b)it could be seen that the CV curves both of bare GCE and MWCNT/PPy almost did not change,indicating that there
was no response to H 2O 2without PB.However,compared with bare GCE and MWCNT/PPy,the MWCNT/PPy/PB composite nano?bers modi?ed electrodes exhibited a strong reduction current,indicating the high electrocata-lytic activity of the obtained MWCNT/PPy/PB composite nano?bers toward the H 2O 2reduction.
Figure 4a gave a typical amperometric response of MWCNT/PPy/PB composite nano?bers modi?ed electrode on successive addition of H 2O 2into a stirring 0.1M H 3PO 4and 1.0M KCl solution at an applied potential of -0.30V.We found that successive addition of H 2O 2resulted in a remarkable increase of reduction current,which was because that H 2O 2could oxidize PB-Fe 2?into PB-Fe 3?quickly,when PB-Fe 3?was electrochemical reduced to PB-Fe 2?.Figure 4b showed the corresponding calibration curve for H 2O 2.It could be seen that a linear response in the range of 0.004–0.517mM with a correlation coef?cient of 0.9954was obtained.The detection limit was 0.08l M on signal-to-noise ratio of 3.The corresponding sensitivity was 24.15l A mM -1.The sensitivity was divided with the area of electrode was 345l A mM -1cm -2,which was much higher than that gained from MWCNT/PB in the literature (153.7l A mM -1cm -2)[24]and others obtained from PPy/PB and single-walled carbon nanotubes (SWNT)/PB composite modi?ed electrode [26,29].The detailed analytical parameters of MWCNT/PPy/PB com-posite nano?bers in comparison with other PB modi?ed electrodes were shown in Table 1.The high sensitivity and low detection limit may attribute the superior transducing ability of PPy and the excellent performance of MWCNT/PPy composite nano?bers.The synergistic effect among MWCNTs,PPy and PB is preferable for the H 2O 2detection and improves the performances of the modi?ed electrode.Figure 4c showed the CV curves of MWCNT/PPy/PB composite nano?bers modi?ed GCE in 0.1M H 3PO 4and 1.0M KCl solution containing 1.0mM H 2O 2at different scan rates in the range of 20–250mVs -1,which repre-sented the kinetics of the obtained MWCNT/PPy/PB composite nano?bers modi?ed electrodes.It was found that the peak current increased accompanied by the scan
rates
Fig.3CVs of a :1bare GCE,2MWCNT/PPy,3MWCNT/PPy/PB composite nano?bers modi?ed electrode in the absence of H 2O 2;b :1bare GCE,2MWCNT/PPy in presence of 1.0mM H 2O 2,3–6MWCNT/PPy/PB
composite nano?bers modi?ed electrode in presence of 1.0,2.0,2.9,3.8mM H 2O 2
increasing from 20to 250mVs -1.The peak currents became proportional with a correlation coef?cient of 0.9993to the square root of the scan rate indicating dif-fusion controlled processes.
Conclusions
In summary,the MWCNT/PPy/PB composite nano?bers based electrochemical sensor in detection of H 2O 2has been demonstrated.In comparison with bare GCE and MWCNT/PPy,the response current by MWCNT/PPy/PB composite
nano?bers modi?ed GCE was greatly enhanced.The elec-trode modi?ed with MWCNT/PPy/PB composite nano?bers exhibited good sensitivity (345l A mM -1cm -2),wide linear range (0.004–0.517mM)and low detection limit (0.08l M)to detection of H 2O 2.The reduction of H 2O 2was controlled by diffusion process through the investigation of the effect of scanning rate.
Acknowledgements This study was supported by the research grants from the National 973Project (S2009061009),the National Natural Science Foundation of China (20904015,50973038),and Jilin Science and Technology Department project (20100101,
201115014).
Fig.4a Amperometric response of the MWCNT/PPy/PB composite nano?bers modi?ed electrode to successive injection of H 2O 2in a stirring 0.1M H 3PO 4and 1.0M KCl solution.The working potential was -0.30V.b Calibration plot,concentration of H 2O 2versus anodic peak current;c CVs of the MWCNT/PPy/PB composite nano?bers modi?ed GCE at different scan rates (20,50,80,100,120,150,180,200,220,250mV s -1);d The dependence of current on the square root of the scan rate
Table 1The data of some PB based electrochemical
characterization designed for the determination of H 2O 2
Linear range (mM)
Sensitivity
(l A mM -1cm -2)Detection limit (l M)References MWCNT/PB 0.01–0.4153.70.567[24]Graphene/PB 0.02–0.2196.6 1.9[25]Ppy/PB 9.9910-4
–8.2635.20.23[26]SWNT/PB 0.5–27.59.20.01[29]PB/[Bmim][Cl]5–30225.2–[35]PB nanoelectrode arrays 1910-5–10600.01[21]MWCNT/Ppy/PB
0.004–0.517
345
0.08
This paper
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