Scaly Graphene Oxide/Graphite Fiber Hybrid Electrodes for ... › zhzhao › files ›...

FULL P

APER

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim (1 of 6) 1500072wileyonlinelibrary.com

Scaly Graphene Oxide/Graphite Fiber Hybrid Electrodes for DNA Biosensors

Jian Zhang , Aixue Li , Xin Yu , Weibo Guo , Zhenhuan Zhao , Jichuan Qiu , Xiaoning Mou , Jerome P. Claverie , and Hong Liu *

J. Zhang, A. Li, X. Yu, W. Guo, X. Mou, Prof. H. Liu Beijing Institute of Nanoenergy and Nanosystems Chinese Academy of Science Beijing 100083 , China E-mail: [email protected] Z. Zhao, J. Qiu, Prof. H. Liu State Key Laboratory of Crystal Materials Shandong University Jinan 250100 , China Prof. J. P. Claverie NanoQAM Research Center Department of Chemistry University of Quebec at Montreal 2101 rue Jeanne-ManceCP 8888 , Montreal , Quebec H3C3P8 , Canada J. Zhang, X. Yu, W. Guo University of Chinese Academy of Sciences Beijing 100049 , China

DOI: 10.1002/admi.201500072

or long analysis time. Therefore, the dis-covery of a rapid, simple, sensitive, selec-tive, and economical DNA biosensor remains a lofty goal.

Electrochemistry-based DNA biosen-sors have been more and more scrutinized because they are suitable for miniaturi-zation and compatible with advanced microfabrication schemes. [ 8–11 ] Many of those contain nanomaterials with unique optical, electronic, and catalytic character-istics in order to promote highly specifi c DNA recognition with enhanced sen-sitivity, fl exibility, and adaptability. [ 12,13 ] Graphene oxide (GO), peeled off from graphite through an oxidation process, has attracted great attention because of its remarkable properties, such as high water dispersability and affi nity toward biomol-ecules. Recently, several DNA biosensors based on GO have been developed. [ 14–18 ] It

has been found that single-strand DNA (ssDNA) can adsorb on GO due to the formation of noncovalent π-stacking interactions between the hexagonal cells of graphene and the aromatic rings of the nucleic acids, while double stranded DNA (dsDNA) or hybrids of DNA/RNA are less prone to be adsorbed on GO. [ 19,20 ] In most cases, GO is prepared by the Hummers method and immobilized onto the surface of the glassy carbon (GC) elec-trode by physical adsorption or chemical assembly, leading to a complex fabrication process for the sensor. In addition, the interaction between the GO sheets and the GC electrode is not strong, which often results in GO sheets being washed away, thus causing a loss of sensor stability. Most importantly, although GO sheets are stacked at the surface of the electrode, only the top layer is accessible, leading to a sensor with low active surface area, and therefore low sensitivity. These disad-vantages must be overcome in order to generate a biosensor from carbon-based graphene hybrid electrodes. Recently, carbon/graphite fi ber microelectrodes have attracted much attention because of their special 1D morphology, small size, and high conductivity which make them particularly suitable for in vivo biodetection. [ 21,22 ] However, carbon or graphite fi bers only have few sites available for biomolecule binding. Several researchers functionalized the surface of the fi ber in order to detect some biomolecules. [ 23,24 ] Carbon fi bers coated with GO were prepared for the detection of redox-active small bioactive molecules such as ascorbic acid, but not for redox neutral oli-gonucleotides which are only present in very low concentra-tion in vivo. [ 25,26 ] In this work, we construct scaly GO/graphite

The demand for a highly sensitive and stable DNA biosensor that can be used for implantable or on-time monitoring is constantly increasing. In this work, for the fi rst time graphene oxide (GO) sheets are synthesized in situ at the surface of graphite fi bers to yield scaly GO/graphite fi ber hybrid electrodes. The partially peeled GO sheets, directly connected with the graphite fi bers, not only provide a large number of binding sites for single-stranded DNA, but also favor high electron transfer rates from GO to the graphite fi bers. Cyclic voltammetry (CV) confi rms that the scaly GO/graphite fi ber hybrid electrode has excellent electrochemical activity. As a working electrode in an electrochemical impedance DNA biosensor, the fi ber hybrid electrode exhibits high selectivity, sensitivity, and stability. Due to its simplicity, low cost, high stability, small size, and unique microfi ber morphology, the scaly GO/graphite fi ber hybrid electrode is an excellent candidate for an implantable biosensor. The method developed here could have a profound impact on the design of GO-based biosensors for DNA detection.

1. Introduction

There has been considerable interest in DNA biosensors due to their important applications in medicine, epidemic prevention, bioengineering, and clinical diagnosis. [ 1,2 ] Various techniques have been developed for DNA analysis, such as real-time polymerase chain reaction (PCR), gene chip, and fl uorescence methods. [ 3–7 ] However, these techniques require either spe-cialized and expensive equipment, complex assay procedure

Adv. Mater. Interfaces 2015, 2, 1500072

www.advmatinterfaces.dewww.MaterialsViews.com

http://doi.wiley.com/10.1002/admi.201500072

FULL

PAPER

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheimwileyonlinelibrary.com1500072 (2 of 6)

fi ber hybrid electrodes through a direct and simple Hummers method. The GO sheets are formed in situ at the surface of the graphite fi bers, one side of GO sheets connected to the graphite fi ber, and the other side suspended in water to form scale-like structures. The resulting electrode allies the high conductivity and morphology of graphite fi ber to the high sensing ability of GO. From this electrode, a high-performance DNA biosensor was constructed. Because GO-based electrodes can be used to detect various biomolecules, including DNA, RNA, miRNA, protein, small molecules, and several biorelated ions, we envi-sion that scaly GO/graphite fi ber hybrid electrodes will become an important platform for building various electrochemical biosensors.

2. Results and Discussion

2.1. Characterization of Scaly GO/Graphite Hybrid Fiber

The surface morphology of the as-prepared hybrid graphite fi bers was characterized using scanning electron microscope (SEM). As shown in Figure 1 a–c, the commercial graphite fi bers have smooth surface with stripes originating from the stretch forming process. Their diameter is about 5–6 µm. After treat-ment by a modifi ed Hummers method, nanosheets with size ≈0.5–2 µm can be observed at the surface of the graphite fi bers, as shown in Figure 1 d–f. These nanosheets are peeled off from the graphite fi bers during the oxidation treatment. One side of the nanosheet is free from the fi ber while the other side is still buried within the graphite substrate, akin to scales on the body of a fi sh. The transmission electron microscopic images of as-prepared hybrid graphite fi bers are shown in Figure S1 (Sup-porting Information). The GO nanosheets could be observed on the surface of fi ber (Figure S1c,d, Supporting Information) after treatment compared with the controlled graphite fi bers (Figure S1a,b, Supporting Information), which is consistent with the results from SEM images. As expected, the scale-like nanosheets are GO nanosheets, and the as-synthesized hybrid fi bers are scaly GO/graphite hybrid fi bers.

To further characterize GO at the surface of the graphite microfi ber, Fourier-transform infrared (FTIR) spectroscopy was

performed ( Figure 2 ). In contrast to the pristine graphite fi ber (curve b), a strong and broad absorption band attributed to the O H stretching vibration appears at 3400 cm −1 in the spectrum of the GO/graphite hybrid fi ber (curve a). Two new absorption bands appear at ≈1700 cm −1 (C O stretching vibrations) and 1300 cm −1 (C O stretching vibrations), which are characteristic of GO. Raman spectroscopy was also used to characterize GO (Figure S2, Supporting Information). Raman spectra show G peaks at 1585 cm −1 and D peaks at 1350 cm −1 , confi rming the lattice distortions. In contrast to the graphite fi ber (curve b), the intensity ratios of D/G increased after surface treatment (curve a). These results confi rm that GO sheets have been formed on the surface of graphite fi ber. [ 27,28 ]

Further confi rmation of the structure of the hybrid fi ber was obtained by X-ray photoelectron spectroscopy (XPS) ( Figure 3 ). Figure 3 a shows the XPS spectra of the graphite fi ber and the scaly GO/graphite fi ber. Although the two spectra look similar at fi rst, the enlarged C 1 s peaks of the graphite fi bers are actu-ally different. In Figure 3 b, the strong C 1 peak of the pristine graphite fi ber at 284.6 eV corresponds to the predominant sp 2


www.advmatinterfaces.de www.MaterialsViews.com

Figure 1. a–c) SEM images of graphite fi ber and d–f) GO/graphite hybrid fi ber.

Figure 2. FTIR spectra of a) GO/graphite hybrid fi ber and b) graphite fi ber.

FULL P

APER


carbon atoms, with smaller C 2 peak at 286.0 eV and C 3 peak at 288.7 eV, which are likely due to oxygen-containing mol-ecules adsorbed at the surface or produced during the stretch forming process. For the GO/graphite fi ber, the C 3 peak is notably increased and a new C 4 peak appears. This C 1 s peak was deconvoluted into four peaks arising from sp 2 carbon (C 1 , aro-matic and 284.6 eV), sp 3 carbon with C O bond (C 2 , 285.7 eV), carbonyls (C 4 , C O, 287.1 eV), and carboxylates (C 3 , O C O, 288.8 eV), as shown in Figure 3 c. [ 28–30 ] The surface oxidation effect is clear since the content of oxygen atoms in the scaly GO/graphite hybrid fi ber signifi cantly increased compared to the pure graphite fi ber, indicating that the harsh oxidation pro-cess disrupted the sp 2 carbon network of graphite.

The electrochemical behavior of scaly GO/graphite hybrid fi ber was assessed by cyclic voltammetry in 0.01 M PBS con-taining 5 × 10 −3 M K 3 [Fe(CN) 6 ]/K 4 [Fe(CN) 6 ] and 0.1 M KCl (pH 7.4), yielding the voltammograms of Figure 4 . The redox peaks are attributed to the following reaction: [ 31 ]

Fe CN e Fe CN6

3

6

4( ) ( )⎡⎣ ⎤⎦ + = ⎡⎣ ⎤⎦− −

(1)

A small redox peak appears in the CV of the untreated graphite fi ber electrode (curve a). For the scaly GO/graphite hybrid fi ber electrode (curve b), the current density is increased and the process is more reversible, indicating that the increase of the electron transfer rate in the GO/graphite fi ber electrode correlates with the presence of GO nanosheets. Therefore, GO/graphite fi ber exhibits an enhanced electrochemical activity compared to the untreated graphite fi ber.

2.2. DNA Detection Using Single-Stranded DNA Assembled on Scaly GO/Graphite Hybrid Fiber Electrode

The scaly GO/graphite hybrid fi ber was used as working elec-trode for detecting DNA. The hybridization of probe DNA and target DNA was monitored by electrochemical impedance spec-troscopy (EIS), which has proven to be a very powerful tool for probing the features of surface-modifi ed electrodes. In fact, the charge transfer process is strongly affected by surface modi-fi cation and therefore by biorecognition events. [ 32 ] Scheme 1 provides the working principle of the GO/graphite hybrid fi ber-based DNA electrochemical impedimetric biosensor. As reported previously, [ 19,20 ] GO can bind ssDNA through rela-tively stable π-stacking interactions between the DNA nucleo-bases and the hexagonal cells of GO, while it has less affi nity toward dsDNA or hybrids of DNA/RNA. When the probe DNA forms a duplex with its target DNA, it is dissociated from the GO surface, thus reducing the resistance for charge transfer, as monitored by EIS. So the reduction of the resistance refl ects the number of DNA–DNA duplexes formed or the number of ssDNA probes being dissociated from the electrode and hence the concentration of the target ssDNA.

Figure 5 shows the impedance changes of the GO/graphite hybrid fi ber electrode accompanying the stepwise modifi ca-tion process. The impedance spectrum is interpreted by fi t-ting with a simple equivalent circuit (inset of Figure 5 ). In this circuit, R s represents the resistance of the solution, R ct repre-sents the resistance to charge transfer between the solution and the electrode surface, W is the Warburg impedance due to the contribution of diffusion and CPE is associated with the capacitance of the double layer. The simulated values of the equivalent circuit elements after every modifi ed step are sum-marized in Table S1 (Supporting Information). When the probe ssDNA is immobilized on the electrode surface, R ct increases



Figure 3. a) XPS fully scanned spectrum of GO/graphite hybrid fi ber (upper) and graphite fi ber (bottom), b) C 1 s XPS spectra of graphite fi ber, and c) GO/graphite hybrid fi ber.

Figure 4. CV responses of a) graphite fi ber and b) GO/graphite hybrid fi ber recorded in 0.01 M PBS containing 5 × 10 −3 M K 3 [Fe(CN) 6 ]/K 4 [Fe(CN) 6 ] and 0.1 M KCl (pH 7.4), scan rate: 10 mV s −1 .

FULL

PAPER

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheimwileyonlinelibrary.com1500072 (4 of 6)

compared to the value for GO/graphite hybrid fi ber electrode due to the steric hindrance introduced by the probe adsorbed at the electrode surface. Another factor that contributes to the R ct increase is the electrostatic repulsion between the negative charges of the probe ssDNA and the negatively charged redox probe K 3 [Fe(CN) 6 ]/K 4 [Fe(CN) 6 ]. When the complementary target ssDNA is introduced, partial release of the probe ssDNA from the GO/graphite fi ber surface occurs, so the R ct value decreases after hybridization with complementary target DNA. The release of the ssDNA probe decreases the steric hindrance as well as the electrostatic repulsion, thus reducing the resist-ance to charge transfer.

As for a control experiment, two graphite fi ber electrodes were prepared, one is the scaly GO/graphite fi ber electrode, and the other is the pure graphite fi ber electrode. The result of EIS indicated that the increased value of R ct for the ssDNA immo-bilization of GO/graphite fi ber electrode is about 12 times greater than that for graphite electrode, as shown in Figure 6 . This result suggests that the presence of GO nanosheets on the graphite fi ber greatly improves the immobilization capacity of the ssDNA probe.

Figure 7 a shows the impedimetric response of the ssDNA probe modifi ed GO/graphite hybrid fi ber electrode for different concentrations of target ssDNA. The R ct value decreases with

the increase of target DNA concentrations. The analytical signal, Δ R ct (Δ R ct = | R ct,target − R ct,probe |), is linear with respect to the logarithmic value of the target DNA concentration ranging from 10 −11 to 10 −9 M by a correlation coeffi cient of 0.9995, as shown in Figure 7 b. The limit of detection, set at 3 σ (where σ is the relative standard deviation of the blank solution), is estimated to be 5.6 × 10 −12 M . These results indicate that this sensor exhibits high sensitivity, comparable to previously reported dendrimer-based and functionalized graphene-based DNA biosensors. [ 32,33 ] Moreover, our approach is label-free and does not need any enzyme reaction. Importantly, scaly GO/graphite hybrid fi ber could be expected to open new opportunities in microelectrode or miniaturized electrochemical sensors.

The selectivity of the electrochemical impedance DNA bio-sensor based on GO/graphite fi ber electrode was assessed using different target DNA (fully complementary, one-base mismatched sequences, and noncomplementary). As shown in Figure 8 , a pronounced increase in Δ R ct is observed with the fully complementary sequence (curve c) and a less or negligible increase in Δ R ct is obtained when incubating with single-base mismatched sequences (curve b) or noncomple-mentary sequence (curve a). When hybridization is less effec-tive, the amount of ssDNA probe released from the surface is lower, resulting in a lower Δ R ct increase. These results demon-strate that the GO/graphite-fi ber-based DNA sensor has high



Scheme 1. The schematic illustration of GO/graphite hybrid fi ber-based DNA biosensor working principle.

Figure 5. a) Nyquist diagrams of GO/graphite fi ber hybrid electrode, b) probe ssDNA modifi ed GO/graphite fi ber electrode, and c) target DNA modifi ed GO/graphite fi ber electrode recorded in 0.01 M PBS containing 5 × 10 −3 M K 3 [Fe(CN) 6 ]/K 4 [Fe(CN) 6 ] and 0.1 M KCl (pH 7.4). Inset: equiva-lent circuit used to fi t impedance data.

Figure 6. The plot of Δ R ct (Δ R ct = | R ct,probe − R ct,blank |) corresponding to the immobilization of probe ssDNA to the two kinds of fi ber electrodes. a) Graphite fi ber and b) GO/graphite fi ber.

FULL P

APER


selectivity. As for the stability of the electrode, after storage at 4 °C for 2 weeks, the sensitivity was only decreased by 12%, indicating that the GO/graphite fi ber is also stable for a long time, despite the relative fragility of ssDNA.

3. Conclusion

For the fi rst time, we successfully synthesized in situ GO nanosheets on a graphite microfi ber, and obtained a scaly GO/graphite hybrid fi ber, which was successfully used as working electrode in an electrochemistry-based DNA biosensor. The biosensor exhibits high sensitivity, high selectivity, low limit of detection, and good storage stability. The high performance of the scaly GO/graphite hybrid fi ber electrode is attributed to the presence of GO sheets directly connected to the surface of the graphite fi ber. These GO sheets provide a large number of active sites, and a high response speed because they are directly connected with the graphite substrate. Due to its simplicity, low cost, and high stability, this new material could have a

great potential for biosensing application. Moreover, due to its fi ber morphology and its fl exibility, it could be useful to per-form DNA monitoring in poorly accessible environments, such as within targeted cell compartments or even in vivo. Further research to extend the applicability of this material is currently ongoing. Clearly, 1D hybrid graphite fi ber electrochemical elec-trodes will constitute in the future an important platform for building highly sensitive and selective biosensors.

4. Experimental Section Materials : All reagents in this work are of analytic grade and are

commercially available. Sulfuric acid (H 2 SO 4 ), phosphoric acid (H 3 PO 4 ), potassium chloride (KCl), potassium permanganate (KMnO 4 ), potassium hexacyanoferrate (K 4 [Fe(CN) 6 ]), potassium ferricyanide (K 3 [Fe(CN) 6 ]), hydrochloric acid (HCl), ethanol, sodium dihydrogen phosphate anhydrous (NaH 2 PO 4 ), and dibasic sodium phosphate (Na 2 HPO 4 ) were supplied by China National Medicines Corporation Ltd. and used as received. Graphite fi bers were purchased from Toray (Japan). All DNA oligonucleotides were purchased from SBS Genetech Ltd. Company (Beijing, China) having the following sequences:

Probe DNA: 5′-AAG CGG AGG ATT GAC GAC TA-3′ Complementary DNA: 5′-TAG TCG TCA ATC CTC CGC TT-3′ Noncomplementary DNA: 5′-AAG CGG AGG ATT GAC GAC TA-3′ Single-base mismatched DNA: 5′-AAG TCG TCA ATC CTC CGC TT-3′ Ultrapure water purifi ed with a Milli-Q ultrapure water system was used throughout the experiment.

Sample Preparation : The commercially available graphite fi bers were sonicated in acetone, 3 M HNO 3 , 1.0 M KOH and distilled water sequentially for a few minutes. To produce the GO nanosheets from graphite fi ber, the improved Hummers method with some modifi cation was adopted. [ 28 ] Briefl y, a 9:1 mixture of H 2 SO 4 /H 3 PO 4 (90:10 mL) was added to KMnO 4 (4.5 g). 10 mg graphite fi bers were carefully immersed into the reaction agent. The reaction was then heated to 60 °C for 12 h. After that, the reaction was cooled to room temperature. The oxidized fi ber was then rinsed with distilled water, 30% HCl, and ethanol and dried at 40 °C in vacuum.

Characterization : A fi eld emission scanning electron microscope (FESEM) (HITACHI S-8020, Japan) was used to characterize the morphology of the synthesized samples. FTIR were collected using an IR spectrometer (NEXUS 670, America) over the range of 4000−400 cm −1 . XPS measurement was performed on an X-ray photoelectron spectroscopy (ESCALAB 250Xi, America) with a



Figure 7. a) Nyquist diagrams recorded at probe DNA immobilized GO/graphite fi ber electrode after hybridization with complementary target ssDNA of different concentrations in the presence of 5 × 10 −3 M K 3 [Fe(CN) 6 ]/K 4 [Fe(CN) 6 ] in 0.01 M PBS (pH 7.4 containing 0.1 M KCl): a–e) 1.0 × 10 −11 , 5.0 × 10 −11 , 1.0 × 10 −10 , 5.0 × 10 −10 , 1.0 × 10 −9 M . b) The plot of Δ R ct (Δ R ct = | R ct,target − R ct,probe |) versus complementary target ssDNA concentration.

Figure 8. The plot of Δ R ct (Δ R ct = | R ct,target − R ct,probe |) corresponding to hybridization with 1.0 × 10 −9 M different DNA sequences: a) noncomple-mentary DNA, b) single-mismatched DNA, and c) complementary DNA.

FULL

PAPER

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheimwileyonlinelibrary.com1500072 (6 of 6) Adv. Mater. Interfaces 2015, 2, 1500072


monochromatized AlK X-ray radiation. X-ray powder diffraction (XRD) patterns were recorded on an X-ray diffraction spectrometer (D8-advance, BrukerAXS, Germany). Raman measurement was performed on a Raman spectrometer (HORIBA / LabRAM HR Evolution, France). A fi eld emission transmission electron microscope (FEI / Tecnai G2 F20 S-TWIN TMP, Czech Republic) was also used to characterize the morphology of the samples.

Electrochemical Measurements : Electrochemical measurements were performed with a computer-controlled electrochemical workstation (Gamry Reference 3000, America) with a standard three-electrode system. Ag/AgCl (saturated KCl) was used as reference electrode and a Pt plate (area, 1 cm × 1 cm) was used as counter electrode. GO/graphite fi bers were fi xed on one side of a clean fl uorine-doped tin oxide (FTO) glass, while a copper wire was fi xed on the other side of the glass. Conductive silver adhesives were used to connect them and polydimethylsiloxane was used to encapsulate the FTO glass. The optical photographs of GO/graphite fi bers hybrid electrodes are shown in Figure S4 (Supporting Information). The as-prepared GO/graphite fi bers electrode was used as working electrode. The length of the immersed fi ber was 0.6 cm. The values of electrochemical active surface area (ECSA) of GO/graphite fi bers electrode were calculated based on the Rundles–Service equation, assuming mass transport only by diffusion process [ 25,34 ]

2.69 10p

5 1/2 3/2 1/2I AD n r C= × (2)

where n is the number of electrons participating in the reaction, D is the diffusion coeffi cient of the molecule (6.7 ± 0.02 × 10 −6 cm 2 s −1 ), A is the electroactive surface area, C is the concentration of analyte (mol cm −3 ), and r is the scan rate (V s −1 ). The calculated ECSA of GO/graphite fi bers electrode was 1.3 cm 2 .

The electrochemical measurements were performed in the presence of 5 × 10 −3 M K 3 [Fe(CN) 6 ]/K 4 [Fe(CN) 6 ] (1:1) mixture as a redox probe in 0.01 M PBS (pH 7.4, containing 0.1 M KCl). The impedance spectra were measured in the frequency range from 100 mHz to 100 kHz with voltage amplitude of 5 mV. The electrical parameters of the system were fi tted with a software package embedded in Gamry Reference 3000. All measurements were carried out at room temperature.

For the probe DNA immobilization, the GO/graphite fi bers electrode was immersed into 0.01 M PBS (pH 7.4, containing 0.1 M KCl) solution containing 100 × 10 −6 M probe DNA at 4 °C overnight. Hybridization reaction of the probe DNA with target DNA was carried out by incubating the fi bers electrode modifi ed by probe DNA into 100 µL target DNA with certain concentrations at 37 °C for 60 min.

Supporting Information Supporting Information is available from the Wiley Online Library or from the author.

Acknowledgements J.Z. and A.L. contributed equally to this work. The authors are thankful for funding from the National Natural Science Foundation of China (Grant No. 51402063), China Postdoctoral Science Foundation (Grant No. 2014M550673), the “100 Talents Program” of the Chinese Academy of Sciences and for the “thousands talents” program.

Received: February 6, 2015 Revised: March 28, 2015

Published online: May 21, 2015

[1] M. Li , Q. Wang , X. D. Shi , L. A , N. Q. Wu , Anal. Chem. 2011 , 83 , 7061 . [2] W. W. Zhao , J. J. Xu , H. Y. Chen , Chem. Rev. 2014 , 114 , 7421 .

[3] F. Wallet , S. Nseir , L. Baumann , S. Herwegh , B. Sendid , M. Boulo , M. Roussel-Delvallez , A. V. Durocher , R. J. Courcol , Clin. Microbiol. Infect. 2010 , 16 , 774 .

[4] D. Y. Xia , J. C. Yan , S. F. Hou , Small 2012 , 8 , 2787 . [5] C. F. Zhu , Z. Y. Zeng , H. Li , C. H. Fan , H. Zhang , J. Am. Chem. Soc.

2013 , 135 , 5998 . [6] Y. Zhang , B. Zheng , C. F. Zhu , X. Zhang , C. L. Tan , H. Li , B. Chen ,

J. Yang , J. Z. Chen , Y. Huang , L. H. Wang , H. Zhang , Adv. Mater. 2015 , 27 , 935 .

[7] Y. Zhang , C. F. Zhu , L. Zhang , C. L. Tan , J. Yang , B. Chen , L. H. Wang , H. Zhang , Small 2015 , 11 , 1385 .

[8] T. G. Drummond , M. G. Hill , J. K. Barton , Nat. Biotechnol. 2003 , 21 , 1192 .

[9] X. Huang , X. Y. Qi , F. Boey , H. Zhang , Chem. Soc. Rev. 2012 , 41 , 666 .

[10] J. Zhang , S. P. Song , L. H. Wang , D. Pan , C. H. Fan , Nat. Protoc. 2007 , 2 , 2888 .

[11] Z. J. Wang , J. Zhang , C. F. Zhu , S. X. Wu , Daniel Mandler , Robert , S. Marks , H. Zhang , Nanoscale 2014 , 6 , 3110 .

[12] R. M. Kong , X. B. Zhang , Z. Chen , W. H. Tan , Small 2011 , 7 , 2428 . [13] F. Li , H. Pei , L. H. Wang , J. X. Lu , J. M. Gao , B. W. Jiang , X. C. Zhao ,

C. H. Fan , Adv. Funct. Mater. 2013 , 23 , 4140 . [14] F. Li , Y. Feng , C. Zhao , P. Li , B. Tang , Chem. Commun. 2011 , 48 ,

127 . [15] X. Huang , Z. Y. Zeng , Z. X. Fan , J. Q. Liu , H. Zhang , Adv. Mater.

2014 , 24 , 5759 . [16] Y. He , X. J. Xing , H. W. Tang , D. W. Pang , Small 2013 , 9 , 1160 . [17] Z. J. Wang , J. Zhang , Z. Y. Yin , S. X. Wu , D. Mandler , H. Zhang ,

Nanoscale 2012 , 4 , 2728 . [18] Z. J. Wang , J. Zhang , P. Chen , X. Z. Zhou , Y. L. Yang , S. X. Wu ,

L. Niu , Y. Han , L. H. Wang , P. Chen , F. Boey , Q. C. Zhang , Bo Liedberg , H. Zhang , Biosens. Bioelectron. 2011 , 26 , 3881 .

[19] C. H. Lu , H. H. Yang , C. L. Zhu , X. Chen , G. N. Chen , Angew. Chem. Int. Ed. 2009 , 121 , 4879 .

[20] S. J. He , B. Song , D. Li , C. F. Zhu , W. P. Qi , Y. Q. Wen , L. H. Wang , S. P. Song , H. P. Fang , C. H. Fan , Adv. Funct. Mater. 2010 , 20 , 453 .

[21] F. C. Sales , R. M. Iost , M. V. Martins , M. C. Almeida , F. N. Crespilho , Lab Chip 2013 , 13 , 468 .

[22] R. E. Ozel , K. N. Wallace , S. Andreescu , Anal. Chim. Acta 2011 , 695 , 89 . [23] L. Xiang , P. Yu , J. Hao , M. Zhang , L. Zhu , L. Dai , L. Mao , Anal.

Chem. 2014 , 86 , 3909 . [24] M. Kang , Y. Lee , H. Jung , J. H. Shim , N. S. Lee , J. M. Baik , S. C. Lee ,

C. Lee , Y. Lee , M. H. Kim , Anal. Chem. 2012 , 84 , 9485 . [25] J. Du , R. Yue , F. Ren , Z. Yao , F. Jiang , P. Yang , Y. Du , Biosens. Bioel-

ectron. 2014 , 53 , 220 . [26] J. Du , R. Yue , Z. Yao , F. Jiang , Y. Du , P. Yang , C. Wang, Colloids Surf.,

A 2013 , 419 , 94 . [27] C. Nethravathi , M. Rajamathi , Carbon 2008 , 46 , 1994 . [28] D. C. Marcano , D. V. Kosynkin , J. M. Berlin , A. Sinitskii , Z. Z. Sun ,

A. Slesarev , L. B. Alemany , W. Lu , J. M. Tour , ACS Nano 2010 , 4 , 4806 .

[29] D. H. Long , W. Li , L. C. Ling , J. Miyawaki , I. Mochida , S. H. Yoon , Langmuir 2010 , 26 , 16096 .

[30] A. J. Patil , J. L. Vickery , T. B. Scott , S. Mann , Adv. Mater. 2009 , 21 , 3159 .

[31] C. Flox , J. Rubio-García , M. Skoumal , T. Andreu , J. R. Morante , Carbon 2013 , 60 , 280 .

[32] A. X. Li , F. Yang , Y. Ma , X. R. Yang , Biosens. Bioelectron. 2007 , 22 , 1716 .

[33] Y. Hu , F. Li , X. Bai , D. Li , S. Hua , K. Wang , L. Niu , Chem. Commun. 2011 , 47 , 1743 .

[34] J. Lu , I. Do , L. T. Drzal , R. M. Worden , I. Lee , ACS Nano 2008 , 2 , 1825 .

Scaly Graphene Oxide/Graphite Fiber Hybrid Electrodes for ... › zhzhao › files ›...

Documents

Transcript of Scaly Graphene Oxide/Graphite Fiber Hybrid Electrodes for ... › zhzhao › files ›...