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Sensors and Actuators B 191 (2014) 401– 407

Contents lists available at ScienceDirect

Sensors and Actuators B: Chemical

journa l h om epage: www.elsev ier .com/ locat e/snb

ighly selective H2O2 sensor based on 1-D nanoporous Pt@C hybridsith core–shell structure

eming Fanga, Yunyun Yanga, Liying Fua, Hongtao Zhenga, Junhua Yuana,b,∗, Li Niuc

College of Life Sciences and Chemistry, Zhejiang Normal University, Jinhua, Zhejiang 321004, ChinaSchool of Pharmacy, Hubei University of Science and Technology, Xianning, Hubei 437100, ChinaState Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022,hina

r t i c l e i n f o

rticle history:eceived 4 July 2013eceived in revised form 30 August 2013ccepted 22 September 2013vailable online 1 October 2013

a b s t r a c t

A strategy of sacrificial template was put forward to prepare porous Pt nanowires core with carbon shell(Pt PNW@C) using Te nanowires as template. These Pt PNW@C hybrids show a highly sensitive responseto H2O2 oxidation recorded by chronoamperometry at 0.2 V vs. the saturated calomel electrode (SCE).Under optimal conditions, this H2O2 transducer displays a linear range of 0.01–1.2 �M with a sensitiveof 6.28 �A �M−1 cm−2 (r = 0.9997), and a detection limit of 0.002 �M (signal/noise = 3). Moreover, the

eywords:t nanowireore–shellelective detectionlectrooxidationlucose biosensor

carbon layer on Pt PNW@C hybrids can greatly enhance the selectivity in H2O2 detection in the presenceof the common interfering species, such as lactic acid (LA), uric acid (UA), creatinine and glucose, at apositive potential by compared with porous Pt nanowires (Pt PNWs). A glucose biosensor was constructedusing this sensitive and selective H2O2 transducer combined with glucose oxidase. A calibration curveof glucose concentration can be obtained by measureing enzymatically generated H2O2, which shows alinear range from 0.5 to 20 �M with a sensitivity of 0.35 �A �M−1 cm−2 and a detection limit of 0.1 �M.

© 2013 Elsevier B.V. All rights reserved.

. Introduction

Hydrogen peroxide (H2O2) is a by-product generated bylmost all oxidases in mitochondria. H2O2 can diffuse out freelyhrough membranes to reach various cellular compartments1]. Maintaining H2O2 at an appropriate level is essential forntracellular signaling transduction and normal cell functions2,3]. H2O2 is also a major reactive oxygen species involved inarious diseases such as cancer, cardiovascular disorders andlzheimer’s disease [4–6]. To better understand the biologi-al effects of H2O2, it is critically important to monitor H2O2evel in biological environment, especially in cellular environ-

ent. Among various measurement used in H2O2 detection, thelectrochemical approach is of particular interest because of itsractical advantages, such as convenience, operation simplicity,

ow instrumentation expense, and suitability for real-time detec-ion [7].

Horseradish peroxidase has a specific catalysis on H2O2

eduction [8,9], but it is susceptible to inactivation underhe electrochemical conditions, which limits its application in2O2 detection. Pt-based nanostructures have been explored as

∗ Corresponding author. Tel.: +86 579 82282269; fax: +86 579 82282269.E-mail address: jhyuan@zjnu.cn (J. Yuan).

925-4005/$ – see front matter © 2013 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.snb.2013.09.090

alternative electrochemical catalysts for H2O2 detection due totheir high activity toward H2O2 reduction as well as H2O2oxidation [1,6]. However, Pt-based nanostructures were not suit-able for selective reduction of H2O2 in the presence of oxygen,because it is also active toward oxygen reduction in the poten-tial range applied to H2O2 reduction [10]. On the other hand, thedirect oxidation of H2O2 at common Pt electrodes often requireshigh overpotential, which is disadvantageous to the sensitiveand selective detection of H2O2 [11]. Therefore, the quantitativedetermination of H2O2 at physiological pH without interferenceis of academic and practical interest. Surface modification canremarkably change the catalytic activity of Pt-based nanostruc-tures toward H2O2 oxidation, and thus improve the sensitivityand selectivity of these sensors prepared by Pt-based nanostruc-tures in H2O2 detection [12,13]. In addition, the electrooxidationof H2O2 plays a major role in the development of biosensorsbased on the determination of enzymatically generated H2O2[14,15].

Herein, a strategy of sacrificial templates was put forward tosynthesize porous Pt nanowire core with carbon shell (Pt PNW@C)using Te nanowire as temple. This novel Pt nanostructures can serve

as efficient catalysts for H2O2 oxidation, and show a high selectiveand sensitive response to H2O2 oxidation even at a high appliedpotential. This H2O2 sensitive sensor can be combined with glucoseoxidase and applied in glucose detection.

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. Experimental

.1. Reagents and materials

Glucose oxidase (GOx) was extracted from Aspergillus nigerFluka company, 211 U/mg), and used without further purification.olyvinylpyrrolidone (PVP, molecular weight: 30,000–40,000),ydrazine hydrate (50%, w/w), aqueous ammonia solution (25%,/w), glutaraldehyde (GA) and albumin from bovine serum

BSA) were purchased from Shanghai Chemical Reagent Co. Ltd.Shanghai, China). Other chemical reagents, such as chloroplatiniccid hexahydrate (H2PtCl6·6H2O), d-glucose, lactic acid (LA), uriccid (UA), creatinine, sodium tellurite, were analytic pure, and pur-hased from Acros. Milli-Q system (18.2 M� cm) was used for thereparation of all solution.

.2. Synthesis of core–shell Te NW@C hybrids

Core–shell Te@C nanowire (Te NW@C) hybrids were synthe-ized by one-pot method, which was similar to the preparation ofe nanowire (Te NW) but in the presence of glucose [17]. Typically,.60 g PVP was dissolved in 25 mL of de-ionized water under vig-rous magnetic stirring to form a homogeneous solution at roomemperature. Then, 0.11 g of Na2TeO3 was added into the previ-us solution and dissolved, followed by the addition of hydrazineydrate (1 mL), ammonia solution (2 mL) and glucose (1 g). Then,he obtained solution was transferred into the container of Teflon-ined stainless steel autoclave, sealed and maintained at 180 ◦Cor 8 h. Finally, the product was centrifuged and washed with de-onized water and alcohol, and finally dissolved in 10 mL de-ionized

ater.Te NWs were synthesized according to previous reports [16].

.3. Synthesis of core–shell 1-D nanporous Pt @C hybrids

Te NW@C hybrids were added into 30 mL de-ionized water andollowed by adding 0.05 mmol H2PtCl6. Pt PNW@C hybrids werebtained after the mixture was continually stirred at 50 ◦C forore than 24 h. Then, the resulting dispersion was centrifuged andashed with de-ionized water for further use.

Porous Pt nanowire (Pt PNW) was prepared according to previ-us reports [17].

.4. Characterization

Transmission electron microscopy (TEM) observation was per-ormed on a JEOL 2010 microscope equipped with an electronnergy dispersive X-ray spectroscopy (EDS), operating at 200 kVith a high-brightness LaB6 electron gun. A drop of 8 �L as-repared suspension containing Te NW, Pt PNW, Te NW@C or PtNW@C hybrids were gently deposited onto a carbon-coated cop-er grid and dried in air prior to TEM observation.

.5. Electrochemical investigation

We used a 15 mL glass electrochemical cell containing threelectrodes: a glassy carbon disk working electrode (3 mm or 6 mmn diameter) embedded in Teflon, a platinum wire counter elec-rode (1 mm in diameter, 5 cm in length), and a saturated calomellectrode (SCE) as the reference electrode. Before use, the glassyarbon or bare Pt disk electrodes were polished with 0.5 �m alu-ina slurry, washed with the de-ionized water, then immersed for

0 min in a sonicator bath, and finally washed with the de-ionizedater.

To modify the glassy carbon electrode (GC, 3 mm in diameter)ith Pt PNW and Pt PNW@C hybrids, 4.0 mg of these materials

ors B 191 (2014) 401– 407

were dispersed in 400 �L de-ionized water to form a homogenouscatalysts ink by sonication, and then a 5 �L of these catalysts inkwas mixed with a 2.5 �L of 0.5% Nafion®117 ethanol solution. Themixture was spread and air-dried on the electrode at room temper-ature. For convenience, these modified electrodes were denoted asPt PNW/GC and Pt PNW@C/GC, respectively.

A three-electrode setup was configured with CHI 660C inter-faced to a personal computer at room temperature for theelectrochemical characterization. The electrolytic solution wasbubbled with nitrogen for 15 min before the electrochemical exper-iment.

H2O2 redox was investigated by cyclic voltammetry in 0.2 Mphosphate buffer solution (PBS, pH 7.4) containing 1 mM H2O2.These modified glassy carbon electrodes were scanned from −0.4 Vto +0.8 V at the scan rate of 50 mV s−1. H2O2 detection was per-formed under the potentiostatic mode at the operating potentialof 0.20 V in 0.2 M PBS (pH 7.4). A rotating disk electrode system(RDE) with a glassy carbon disk (6 mm in diameter) was appliedin the amperometric measurement under a rotate rate of 500 rpm,which was controlled by a Pine analytical rotor (Model AFMSRX).For convenience, these modified electrodes were denoted as PtPNW/RDE-GC and Pt PNW@C/RDE-GC, respectively.

The electrolytic solution was bubbled with nitrogen for 15 minbefore the electrochemical experiment, and the electrochemicalexperiments were conducted at the room temperature in ambientcondition.

2.6. Preparation of glucose biosensor and detection of glucose

To fabricate glucose biosensor, an aqueous GOx solution wasprepared by dissolving 2 mg GOx and 1 mg BSA in 100 �L of PBSsolution. Another Pt PNW@C dispersion was prepared by dispersing1.0 mg Pt PNW@C hybrids in 1 mL of PBS (pH 7.4) solution. Then a5 �L of the GOx solution and a 5 �L of the Pt PNW@C dispersion wasmixed with 4 �L of 0.025% GA, spread, rinsed with the de-ionizedwater and air-dried on a polished glassy carbon electrode (6 mmin diameter) before use. Glucose detection was also performed at0.20 V in 0.2 M PBS (pH 7.4), which is controlled by a Pine analyticalrotor under a rotate rate of 500 rpm. For convenience, this glucosebiosensor was denoted as Pt PNW@C/GOx/RDE-GC.

This glucose sensor was applied in glucose detection inblood sample. The response current was recorded at PtPNW@C/GOx/RDE-GC in 0.2 M PBS (pH 7.4) after 10 �L serum wasadded under stirring at a rotate rate of 500 rpm.

3. Results and discussion

3.1. Characterization of Pt PNW@C hybrids

Well-defined Te NW@C hybrids with core–shell structures canbe fabricated in one-pot strategy by hydrothermal carbonizationof glucose. Fig. 1A and B shows several micron-long Te NWs withhigh aspect ratios sheathed in the thin carbon cover. The averagediameter of inner Te NWs is 10 nm, and the mean thickness of outercarbon layer is 2–3 nm. Upon the basis of the high resolution TEM(HRTEM), as shown in Fig. 1B, it is clear that the d-spacing of adja-cent fringes on Te NWs is 0.592 nm, corresponding to the (0 0 1)planes of hexagonal lattice of Te [18]. Fig. 1C and D shows that Ptnanowires are covered with thin carbon layer. These as-preparedPt PNW@C hybrids still remain core-shell structure with 10.5 nm Ptnanowires core and 2–3 nm carbon shell. In addition, different from

those smooth Te nanowires, these Pt nanowires are porous, com-posed of aggregated Pt nanocrystals. The HRTEM image shows thelattice spacing on a single Pt nanocrystal is 0.230 nm, correspond-ing to the (1 1 1) planes of face-centered cubic lattice of Pt [19]. This

K. Fang et al. / Sensors and Actuators B 191 (2014) 401– 407 403

magni

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Fig. 1. TEM images of (A), (B) Te@C and (C), (D) Pt PNW@C hybrids in low

esult indicates that Te NW@C hybrids have been effectively trans-ated into Pt PNW@C hybrids. This translation was confirmed by theDS curves as shown in Fig. S1. In the case of Te NW@C hybrids, Te,

a and Lb peaks are presented at 3.75 and 3.96 keV, respectively (itselative K peak 27.3 keV), but for Pt PNW@C hybrids, No Te elementan be detected. Indeed, it can be seen Pt Ma peak at 2.1 keV withts relative La peak at 9.5 keV and Lb peak at 11.1 keV.

Fig. 2. TEM images of (A), (B) Te and (C), (D) Pt PNW in low magnification

fication (A), (C) and high magnification (B), (D). Inset: Their high HRTEMs.

For comparison, Te NWs were prepared according to previousreports, and Pt NWs was synthesized by the replacement reac-tion in ethanediol using Te NWs as template [16]. Fig. 2A and B

shows several micron-long Te NWs with an average diameter of10 nm. The surface of Te NWs is smooth, no carbon cover canbe observed. HRTEM images show the characteristic of Te (0 0 1)planes present on Te NWs with a lattice spacing of 0.592 nm. After

(A), (C) and high magnification (B), (D). Inset: Their high HRTEMs.

404 K. Fang et al. / Sensors and Actuators B 191 (2014) 401– 407

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Fig. 4. CV curves of Pt PNW@C/GC (a) and (b), Pt PNW/GC (c) and (d), Pt (e) and (f)and GC (g) and (h) in 0.2 M PBS (pH 7.4) in the presence of 1 mM H2O2 (a, c, e, g) andin the absence of 1 mM H2O2 (b, d, f, h) at the scan rate of 50 mV s−1.

ig. 3. CV curves of (a) Pt PNW/GC and (b) Pt PNW@C/GC in Nitrogen-saturated.5 M H2SO4 solution at the scan rate of 50 mV s−1.

e NWs were mixed and stirred with Pt precursor for 24 h, Te ele-ent was replaced by Pt component. As shown in Fig. 2C and D,

mooth Te NWs were disappeared, and porous Pt nanowires (PtNWs) were formed. In addition, some small Pt nanoparticles wereggregated and attached to the surface of these Pt PNWs. HRTEMmages show the characteristic of Pt (1 1 1) planes present on PtNWs with a lattice spacing of 0.592 nm, confirming the conver-ion of Te NWs into Pt PNWs through the replacement reactionetween Te NWs and Pt precursor H2PtCl6.

.2. Electrochemical investigation of Pt PNW@C hybrids

The electrochemical behavior of Pt PNW@C hybrids was stud-ed by cyclic voltammetry. Fig. 3 shows the CV curves of Pt PNW/GCnd Pt PNW@C/GC in N2-saturated 0.5 M H2SO4 solution. Both thet PNW and Pt PNW@C hybrids display the signatures of polycrys-alline Pt in the potential interval between −0.2 and 0.1 V, whichan be divided into the reductive adsorption region of protonsn the reverse cathodic scan and the oxidative desorption regionf hydrogen atom in the forward anodic scan [20]. This potentialegion is defined as the hydrogen area, which can be used to cal-ulate the electroactive surface area (ESA) of Pt based hybrids [21].s shown in Fig. 3, Pt PNW is active toward hydrogen reductionnd oxidation characterized with two well-refined current peakst the formal potential of 0.046 V and −0.085 V. But for Pt PNW@Cybrids, no observable peak current is present in hydrogen area.he ESAs of Pt PNW and Pt PNW@C hybrids were estimated by inte-rating the hydrogen region, which was 108 m2 g−1Pt for Pt PNWnd 86 m2 g−1Pt for Pt PNW@C hybrids, respectively. The less ESAf Pt PNW@C hybrids may be related to the carbon layer on theurface of Pt PNW, which will occupy the active sites of Pt, and thusimit the activity of Pt catalysts.

.3. Electro-catalytic oxidation of H2O2 at Pt PNW@C/GC

The electrochemical catalysis toward H2O2 was also investi-ated by cyclic voltammetry. In the applied potential ranged from0.4 to 0.8 V, as shown in Fig. 4, H2O2 oxidation at Pt PNW@C/GC

tarts from −0.09 V with a negative shift by 0.02 V as compared tot PNW/GC. The oxidative current of H2O2 reaches its peak valuet 0.15 V for Pt PNW@C/GC and 0.18 V for Pt PNW/GC, respectively.bviously, the carbon layer on Pt PNW does not impede H2O2 oxi-

ation. Indeed, it is conductive to oxidation to some extent, whichay account for the negative shift of its oxidative potential of H2O2.

or comparison, H2O2 oxidation was also studied at a bare plat-num electrode as control. No obvious oxidative current of H2O2 at

Fig. 5. Chronoamperometric responses of (a) Pt PNW/RDE-GC and (b) PtPNW@C/RDE-GC measured at 0.2 V in 0.2 M PBS (pH 7.4) to successive additionsof various concentration of H2O2. Inset: Their corresponding calibration plots.

the bare Pt electrode can be observed until the applied potentialwas polarized up to 0.30 V. On the other hand, the peak current ofH2O2 oxidation at the bare Pt electrode is much lower than thatof Pt PNW@C/GC. The excellent behavior of H2O2 oxidation at PtPNW@C/GC is ascribed to the higher active surface area of thesePt nanostructures by comparison with the bare Pt electrode, whichwill favor the electron transfer between H2O2 and active sits of Ptsurface. In addition, the onset potential of H2O2 oxidation at thebare Pt electrode is about 0.4 V, far above that of Pt PNW@C/GC.

3.4. Amperometric determination of H2O2 at Pt PNW@C/GC

H2O2 detection was carried out by chronoamperometry. Fig. 5shows the typical amperometric responses of Pt PNW/RDE-GC andPt PNW@C/RDE-GC to subsequent addition of H2O2 in 0.2 M PBS(pH 7.4) at 0.2 V. Both Pt PNW/RDE-GC and Pt PNW@C/RDE-GCrespond quickly to the change of glucose concentration and reach

a steady-state signal within 5 s upon H2O2 addition. Inset showsthe corresponding calibration curve of Pt PNW/RDE-GC and PtPNW@C/RDE-GC, respectively. As to Pt PNW@C/RDE-GC, its calibra-tion curve displays a linear range of 0.01–1.2 �M with a sensitive of

K. Fang et al. / Sensors and Actuators B 191 (2014) 401– 407 405

Table 1Comparison on the analytical performance of the H2O2 sensors reported previously.

Electrode materials Detection potential (V) Sensitivity (�A mM−1 cm−2) Linear range (�M) Detection limit (�M) Reference

PtPd/MWCNT 0.25 414.8 2.5–1.25 × 102 1.2 [7]PtNP-CNT arrays −0.1 140 5–2.5 × 104 1.5 [24]PtNP-TiO2 nanotube arrays 0.3 1.68 4–1.25 × 103 4.0 [25]PDDA/t-MWCNT-Pt −0.1 48.12 1–8 × 103 0.27 [22]Pt-SnO2@C 0.5 241.1 1 × 103–1.7 × 105 0.1 [11]

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Pt PNW 0.2 881.0

.28 �A �M−1 cm−2 (r = 0.9997), and a detection limit of 0.002 �M.he analytic performance on H2O2 detection at Pt PNW/RDE-GC isuperior to that at Pt PNW@C/RDE-GC, reflected in the wider lin-ar range (0.01–1.6 �M), a higher sensitivity (8.81 �A �M−1 cm−2

r = 0.9993)) and a lower detection limit of 0.001 �M. On the otherand, the amperometric response of H2O2 oxidation is dependentn the applied potentials. As shown in Fig. S2, the optimum oxi-ation potential in glucose detection is 0.2 V, which fits well with

ts CV curve. For comparison, the detection parameters on glucoset several modified electrodes were listed in Table 1. The detectionimit, linear calibration range and sensitivity for H2O2 determina-ion at Pt PNW@C/RDE-GC are comparable and even better thanhose obtained at the electrodes reported recently.

.5. Selectivity, reproducibility and stability of Pt PNW@C/GC

In real samples, the common species such as LA, UA, creati-ine and glucose, co-exist with H2O2 in biological environment,hich will interfere with H2O2 detection [18]. Fig. 6 shows the

mperometric responses of these electroactive species (pH 7.0)pon subsequent additions of 0.1 �M H2O2, 0.2 mM UA, 0.2 mMA, 0.2 mM creatinine and 0.2 mM glucose. To study the selectiv-ty of H2O2 detection at Pt PNW/RDE-GC and Pt PNW@C/RDE-GC,he applied potentials were set at −0.2 V and 0.2 V, respectively.

hen the modified electrodes were polarized at −0.2 V, the injec-ions of H2O2 gave rise to a remarkable current response to H2O2eduction immediately. Since these interfering species cannot beeduced below the potential of −0.2 V, no currents can be observedfter addition of the interfering species. This result was consis-ent with the previous reports [22]. When the modified electrodesere polarized at 0.2 V, the injections of H2O2 still produced a

onsiderable current response to H2O2 oxidation immediately, but

he addition of the interfering species caused different currentesponses at different modified electrodes. For Pt PNW@C/RDE-GC,he introduction of UA, LA, creatinine and glucose generated a neg-igible current response, but for Pt PNW/RDE-GC, the introduction

ig. 6. Chronoamperometric curves of Pt PNW/RDE-GC (a) and Pt PNW@C/RDE-GC (b) rec.1 �M H2O2, 0.2 mM UA, 0.2 mM LA, 0.2 mM creatinine and 0.2 mM glucose.

1 × 10−2–1.2 0.002 This work1 × 10−2–1.6 0.001 This work

of these interferents generated observable oxidative currents. Theresponse currents of UA, LA, creatinine and glucose at Pt PNW/RDE-GC amounted to 9.5%, 3.1%, 4.5% and 30.5% that of H2O2 oxidation,respectively. Thus, the Pt PNW@C/RDE-GC shows a highly selec-tive response to H2O2 in the presence of high concentrations ofthe interfering species even at a positive applied potential. Thisresult demonstrates that the carbon layer on Pt PNW can blockthe diffusion of these interfering species into the electrode inter-face, and restrict the electrons transfer between Pt PNW and theseinterfering species (Fig. S3).

To characterize the reproducibility of Pt PNW@C/RDE-GC, repet-itive measurements were carried out by chronoamperometry at0.2 V in 10 mL PBS (pH 7.4) upon addition of 10 �L of 0.1 M H2O2.The relative standard deviation of ten successive measurementswas 1.5%, indicative of acceptable detection reproducibility forpractical analysis.

The long-term storage and operational stability of the sensoris essential for continuous and reliable monitoring of H2O2, the PtPNW@C/GC was stored at 5 ◦C for one month, its current responseto 0.1 �M H2O2 at 0.2 V remained 94% of its initial value. In addi-tion, the stability of Pt PNW@C/GC was further evaluated by cyclicvoltammetry, which was measured by 20 repetitive potential scan-nings in PBS (pH 7.4) containing 1 mM H2O2. No obvious change inthe peak potential and peak current of the oxidation of H2O2 can beobserved. The coefficient of variation in the peak current betweenfirst and last cycles of CVs was calculated to be 0. 8%, confirmingthat the electrode keep stable without deactivation (Fig. S4).

3.6. Amperometric biosensing of glucose at PtPNW@C/GOx/RDE-GC

Since the Pt PNW@C hybrids show excellent sensitivity, selec-

tivity and high stability toward H2O2 detection, this modifiedelectrode can be used in the development of oxidase based ampero-metric biosensors. The oxidase enzymes can catalyze the oxidationof variety of analytes in the presence of oxygen. H2O2 will be

orded at −0.2 V (A) and 0.2 V (B) in 0.2 M PBS (pH 7.4) after successive additions of

406 K. Fang et al. / Sensors and Actuators B 191 (2014) 401– 407

Fig. 7. (A) Chronoamperometric response of Pt PNW@C/GOx/RDE-GC recorded at 0.2 V in 0plot.

Table 2Determination of glucose in human serum samples with the glucose sensor.

Sample no. Given by hospital Determined by sensor Relative errors

1 11.2 mM 11.6 mM +3.6%

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enerated during these enzymatic reactions. Take the glucose oxi-ase (GOx) for examples, the catalytic oxidation of glucose goes asollow:

lucose + O2GOx−→Gluconic acid + H2O2

he amount of enzymatically generated H2O2 is proportional tohe glucose concentration, thus this H2O2-sensitive electrode cane used for the measurement of glucose present in the biosamples.

Fig. 7 shows the amperometric response of PtNW@C/GOx/RDE-GC upon the successive addition of glucosen PBS (pH 7.4) at 0.2 V. This response is a fast process with annterval of 7 s, and the anodic current of increase linearly withlucose concentration over the range from 0.5 �M to 20 �Mr = 0.9988) with a sensitivity of 0.35 �A �M−1 cm−2. The detectionimit of glucose is estimated to be 0.1 �M, which is lower thanhat of 2.5 �M detected by the biosensor based on Pt nanoparticlesssembled on functionalized ordered mesoporous carbon [15]nd close up to 0.5 �M detected by the biosensor based on thelectrode modified with ionic liquid/graphene nanocomposites14].

This biosensor based on Pt PNW@C/GOx/RDE-GC can be usedo evaluate glucose concentration in blood by chronoampero-

etry. The glucose concentration was calculated from the currentesponse according to the calibration curves of glucose in Fig. 7.s a control, serum was initially detected using the Automatic Bio-hemical Analyzer in hospital, 100 �L of serum was diluted to 4 mLith PBS (pH 7.4). The methodology at the hospital was hexokinaseethod, which was a generally acknowledged optical method to

etermine glucose [23]. The results determined by the amperomet-ic methods in our works were consistent with those from hospitalTable 2). Thus, Pt PNW@C/GOx/RDE-GC biosensor can be practi-ally applied in clinical analysis to detect the glucose concentrationn blood.

. Conclusion

Pt PNW@C hybrids was synthesized though replacement reac-ion using Te NWs as template. This novel Pt PNW@C hybrids show

high sensitive and selective response to H2O2 oxidation in PBS (pH.4) without interference from the common electroactive species.

[

.2 M PBS to successive additions of 0.5 �M glucose, (B) its corresponding calibration

An application of Pt PNW@C hybrid was documented as glucosebiosensor combined with GOx. This transducer shows a good lin-ear rage (0.5–20 �M) with a high sensitivity of 0.35 �A �M−1 cm−2

and a low detection limit of 0.1 �M.

Acknowledgement

This work was supported by the National Natural Science Foun-dation of China (No. 20903082).

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.2013.09.090.

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Biographies

Keming Fang received B.S. degree from Zhejiang Normal University in 2000. Nowhe is a lab assistant at Zhejiang Normal University. Her research is focused on theelectrochemical biosensors.

Yunyun Yang received B.S. degree from Zhejiang Normal University in 2012, Hisresearch focused on biosensors.

Liying Fu is an undergraduate student at Zhejiang Normal University. His researchfocused on the electrochemical sensors and biosensors.

Hongtao Zheng is an undergraduate student at Zhejiang Normal University. Hisresearch focused on the electrochemical sensors and biosensors.

Junhua Yuan received M.S. degree from China University of Geosciences in 2003,and got a Ph.D in State Key Laboratory of Electroanalytical Chemistry, ChangchunInstitute of Applied Chemistry, Chinese Academy of Sciences in 2006, now he isan associate Professor at Zhejiang Normal University and his research focuses onelectrochemical biosensors and fabrication of nanomaterials.

Li Niu received a B.S. degree (1992) and M. S. degree (1995) from Jilin University and

Changchun Institute of Applied Chemistry, Chinese Academy of Sciences in 1998. Heis currently a full professor of analytical chemistry in Changchun Institute of AppliedChemistry. His current research interests include nanobiosensor, nanofabrication,and electrochemical biosensors.