Biosensors and Bioelectronics 60 (2014) 325–331

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An electrogenerated chemiluminescence sensor based on gold nanoparticles@C60 hybrid for the determination of phenolic compounds Qiyi Lu a, Hongxiang Hu a, Yuanya Wu b, Shihong Chen a,n, Dehua Yuan a, Ruo Yuan a,n a Key Laboratory of Luminescent and Real-Time Analytical Chemistry (Southwest University), Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, PR China b Chongqing Key Laboratory for Advanced Materials and Technologies of Clean Electrical Power Sources, Institute for Clean Energy & Advanced Materials, Southwest University, Chongqing 400715, China

art ic l e i nf o

a b s t r a c t

Article history: Received 18 March 2014 Accepted 22 April 2014 Available online 2 May 2014

This paper described a novel strategy for the construction of an electrogenerated chemiluminescence (ECL) sensor based on gold nanoparticles@C60 (AuNPs@C60) hybrid for detecting phenolic compounds. First, C60 was functionalized with L-cysteine. Subsequently, with C60 as the core, gold nanoparticles (AuNPs) are synthesized and grown through an in situ reduction method in the presence of ascorbic acid (AA). The resulted flowerlike AuNPs@C60 nanoparticles were modified onto the glassy carbon electrode to achieve the sensor (AuNPs@C60/GCE). Here, L-cysteine not only can improve the biocompatibility and hydrophilicity of C60 but also can enhance the electrogenerated chemiluminescence (ECL) of peroxydisulfate system. Furthermore, both AuNPs and C60 are also beneficial to the ECL of the peroxydisulfate system. Due to the combination of L-cysteine, AuNPs and C60, the proposed ECL sensor exhibited an excellent analytical performance. Under an optimum condition, the ECL intensity increased linearly with phenolic compounds. The linear ranges of 6.2  10  8–1.2  10  4 M, 5.0  10  8–1.1  10  4 M and 5.0  10  8–1.1  10  4 M were obtained for catechol (CC), hydroquinone (HQ) and p-cresol (PC), respectively, and the detection limits were 2.1  10  8 M, 1.5  10  8 M and 1.7  10  8 M, respectively. The AuNPs@C60 hybrid might hold a new opportunity to develop an ECL sensor. & 2014 Elsevier B.V. All rights reserved.

Keywords: Electrogenerated chemiluminescence Sensor C60 Gold nanoparticles L-Cysteine Phenolic compounds

1. Introduction Phenolic compounds are widely used in the chemical industry, oil refinery, polymer and pharmaceutical preparation (Ballesteros et al., 2006; Galeano-Díaz et al., 2000; Mu, 2006). Meanwhile, phenolic compounds are considered as pollution when they were released in the environment owing to their toxicity (Alexieva et al., 2008; Arecchi et al., 2010). Therefore, the rapid and accurate determination of phenolic compounds is of great importance. Among various determination methods for phenolic compounds, such as fluorescence quenching (Lin et al., 2010), capillary electrophoresis (Schö ning et al., 2005), high performance liquid chromatography (HPLC) (Zhang et al., 2011), and electrochemistry methods (Hellmann et al., 2003), electrogenerated chemiluminescence (ECL) is a better alternative because it not only can avoid complex

n

Corresponding authors. Tel./fax: þ86 23 68253172. E-mail addresses: [email protected] (S. Chen), [email protected] (R. Yuan). http://dx.doi.org/10.1016/j.bios.2014.04.044 0956-5663/& 2014 Elsevier B.V. All rights reserved.

manipulations, time-consuming and sample pretreatments process, but also has remarkable features including high sensitivity, good selectivity, low background signal, good temporal, and spatial control (Gao et al., 2008; Lin et al., 2008). Thus, it is acquirable to develop a promising ECL method to detect phenolic compounds. Recently, fullerene (C60), a third allotrope of carbon with numerous conjugated π electrons (Guldi et al., 2006), has aroused high attention of researchers due to their remarkable features such as high symmetry, readily available with high purity as well as outstanding physical, and chemical properties (Li et al., 2009). Moreover, C60 can improve the ECL intensity of peroxydisulfate system, because it can enhance electron transfer and charge shift (Qian and Yang, 2007). Yet, the solubility of C60 in aqueous solution is poor, which limited its applications in water (Szűcs et al., 1996; Szűcs et al., 1998). Many studies have reported that C60 can react with the compounds containing multi-polar groups (such as hydroxyl, carboxyl and amido) to generate water-soluble derivatives (Benyamini et al., 2006; Huang et al., 2011; Krishna et al., 2006; Plonska et al., 2006; Xiao et al., 2004), so as to broaden the application of C60. L-

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Cysteine (L-cys), as a compound containing –NH2 and –SH groups, not only can interact with C60 to obtain the watersoluble L-cys–C60 derivative, but also can improve the ECL intensity of the peroxydisulfate system (Niu et al., 2011). Obviously, the L-cys–C60 composite is of great benefit to amplify the ECL intensity of the peroxydisulfate system and enhance the sensitivity of the detection. In the meantime, some studies have reported that C60-based sensors act as surpassing working electrodes due to their remarkable features such as excellent biocompatibility, high electroactive surface, and outstanding electronic conductivity (Goyal et al., 2009). As is well-known, gold nanoparticles (AuNPs) have good biocompatibility, good conductivity (Brown et al., 1996), as well as strong adsorption ability (Boisselier and Astruc, 2009). Furthermore, AuNPs can promote the electron transfer and enhance the ECL intensity of the peroxydisulfate system, thus AuNPs are usually used in many ECL sensors (Yuan et al., 2013a). Inspired by the above observation, our motivation in this study is to combine the advantages of the ECL detection method and the good performance of C60, L-cys and AuNPs to construct an ECL sensor for the determination of phenolic compounds, so as to expand the application of C60 in ECL field. First, C60 was functionalized with L-cys to get the water-soluble L-cys–C60 derivative. Then, AuNPs were in situ reducted using ascorbic acid (AA) onto the L-cys–C60 to achieve the AuNPs@C60 nanoparticles. The prepared AuNPs@C60 hybrids were used to construct an ECL sensor for detecting phenolic compounds. It is found that phenolic compounds could enhance the ECL signal of AuNPs@C60 in the peroxydisulfate system. To the best of our knowledge, no progress has been made to construct AuNPs@C60 based ECL sensor for the phenolic compounds. Due to the integration of excellent performance of C60, L-cys and AuNPs in enhancing ECL intensity and improving the electron transfer rate, our proposed strategy would provide a new opportunity to develop ECL phenolic compounds sensors.

2. Experimental 2.1. Reagents and chemicals Fullerene (C60) was purchased from Yongxin Chemical Reagent Co. (Puyang, China). L-cysteine (L-cys) was purchased from Kelong Chemical Reagent Co. (Chengdu, China). 0.10 M phosphatebuffered saline (PBS) with various pH was prepared using the stock solutions of Na2HPO4 and KH2PO4. The supporting electrolyte was 0.10 M KCl. Potassium persulfate (K2S2O8) was purchased

from Shanghai Chemical Reagent Co. (Shanghai, China). Gold chloride tetrahydrate (HAuCl4  4H2O) was obtained from Sigma Chemical Co. (St. Louis, MO, USA). All other chemicals employed were of analytical grade and employed as received. Doubly distilled water was used throughout the experiments.

2.2. Apparatus The ECL emission was monitored using a model MPI-A electrochemiluminescence analyzer (Xi’an Remax Electronic Science &Technology Co. Ltd., Xi’an, China), equipped with a photomultiplier tube (PMT) with a voltage set at 800 V for detection. Electrochemical measurements were monitored using a CHI 660D electrochemical work station (CH Instruments Co., China). Scanning electron micrographs were studied using a scanning electron microscope (SEM, Hitachi, Japan). Transmission electron microscopy (TEM) was studied by a TECNAI 10 (Philips Fei Co., Hillsboro, OR). The FT-IR spectra were studied using a Nexus 670 FT-IR spectrophotometer (Nicolet Instruments).

2.3. Synthesis of L-cys–C60 derivatives and AuNPs@C60 nanoparticles The L-cys–C60 derivatives were synthesized according to a previously described method with minor modification (Zhong et al., 2011). In brief, 0.20 g L-cysteine was dissolved in 0.60 mL NaOH solution (7.1 mol/L) and then 4.0 mL ethanol was added into the solution. Next, the above mixture solution was added into C60 toluene solution (1 mg/mL) under stirring. After 5 days, the dark brown product L-cys–C60 was centrifuged, washed in doubledistilled water, and then redispersed in water. Subsequently, 1.0 mL 1.0 wt% HAuCl4 solution was added into the L-cys–C60 suspension with stirring. After the mixture solution was stayed for 2 days at room temperature, ascorbic acid (AA) was added into the mixture solution, meanwhile, the color of solution became purple black. Finally, AuNPs@C60 product was obtained through centrifugation and washed several times by double-distilled water. Scheme 1 shows the preparation process of the AuNPs@C60 nanoparticles.

2.4. Preparation of the sensor The glassy carbon electrode (GCE, 4.0 mm in diameter) was polished carefully with 0.3 mm and 0.05 mm alumina particles on silk, and then ultrasonically rinsed with double distilled water and ethanol, respectively. After that, 15 mL AuNPs@C60 suspensions were cast onto the pretreated GCE surface and dried at room temperature to obtain the sensor (AuNPs@C60/GCE). For comparison, C60/GCE and L-cys–C60/GCE were also prepared with the similar procedure for the preparation of AuNPs@C60/GCE by replacing AuNPs@C60 with C60 or L-cys–C60, respectively.

2.5. Experimental measurements

Scheme 1. Schematic diagram of the preparation process of AuNPs@C60 nanoparticles.

The ECL intensity was measured in a 3 mL PBS solution containing K2S2O8 as the detection solution at room temperature. A three-electrode system was used. A platinum wire was used as the auxiliary electrode, an Ag/AgCl (sat.) electrode acted as the reference electrode, and the working electrode was a modified glassy carbon electrode. The determination was based on the change in ECL intensity (ΔI¼ I  I0). Herein, I and I0 are the ECL intensities with and without phenolic compounds, respectively.

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327

Fig. 1. SEM images of (A) C60, (B) L-cys–C60 and (C) AuNPs@C60 nanoparticles. TEM images of (D) C60, (E) L-cys–C60 and (F) AuNPs@C60 nanoparticles.

c

b

1629

1296

b 1629

524

2080 2637

Absorbance

Transmittance

d c a

1296

a

1589 1426

1179

573 524

4000

3000

2000

Wavenumber /

1000 cm-1

200

400

600

800

Wavelength / nm

Fig. 2. (A) FT-IR spectra of (a) C60, (b) L-cys, (c) L-cys–C60 and (d) AuNPs@C60; (B) UV–vis spectra of (a) C60, (b) L-cys–C60 and (c) AuNPs@C60.

3. Results and discussion 3.1. Characterization of the AuNPs@C60 SEM and TEM were performed to characterize the C60, L-cys– C60 and AuNPs@C60. As presented in the SEM image (Fig. 1A) and TEM image (Fig. 1D) of C60, spherical structures of C60 were observed. Fig. 1B and E shows the SEM and TEM images of L-cys–C60 derivative, respectively. Fig. 1B and E presents irregular and graininess structures, which were different from the images of C60, indicating that the L-cys–C60 aggregates were successfully prepared. For the SEM image of AuNPs@C60 hybrids (Fig. 1C), welldefined flowerlike nanoparticles were observed and their sizes were about 100–200 nm. The enlarged picture of flowerlike AuNPs@C60 nanoparticles is shown in the inset of Fig. 1C. Fig. 1F presents the TEM image of AuNPs@C60 nanoparticles. Although the flowerlike structures were not clear as those in Fig. 1C, zigzag structures were clearly observed at the edge part of nanoparticles. Both the SEM and TEM images of AuNPs@C60 suggested that AuNPs were successfully synthesized and grown onto the surface of C60 in the presence of AA through an in situ reduction process.

The FT-IR spectra of a series of materials have been conducted and the results are shown in Fig. 2A. As seen from curve a, four characteristic peaks for C60 were observed at 524, 573, 1179 and 1426 cm  1, which were consistent with the reported literature (Bai et al., 2010). The FT-IR spectrum of L-cys is shown in curve b. As seen from curve b, the absorption peaks at 2637 cm  1 and 2080 cm  1 for NH3þ and the wagging vibration peak at 1296 cm  1 for CH2–S were clearly observed. As shown in curve c, the FT-IR spectrum of L-cys–C60 presented the characteristic peak of C60 at 524 cm  1, but the absorption peaks at 2637 cm  1 and 2080 cm  1 for NH3þ of L-cys disappeared. This fact indicated that –NH2 of L-cys was combined with C60 by the covalent reaction. Curve d was the FT-IR spectrum of AuNPs@C60. As expected, the wagging vibration peak of CH2–S at 1296 cm  1 for L-cys observed in both curves b and c disappeared in curve d. Instead, the stretching vibration of CQO at 1629 cm  1 for L-cys was observed not only in curve c but also in curve d, indicating that AuNPs were grown on the L-cys–C60 through thiol group of L-cys rather than the –COOH of L-cys. The ultraviolet–visible (UV–vis) absorption spectroscopy was used to investigate AuNPs@C60 nanoparticles and the results are shown in Fig. 2B. Because the dipole allowed transitions, C60 has

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three strong absorption peaks at 212, 283, and 365 nm (curve a), which was consistent with the reported literature (Graja et al., 2004). Compared with the C60, the absorption peak at 365 nm disappeared and a red-shift trend of the surface-plasmon band at 212 nm and 283 nm was observed at the L-cys–C60 derivatives (curve b), indicating the formation of L-cys–C60 derivatives. When AuNPs were grown onto the surface of C60 (curve c), the characteristic absorbance peak of AuNPs was obviously observed at 534 nm and the characteristic peaks corresponding to L-cys–C60 became weak, indicating that the AuNPs@C60 nanoparticles were formed.

3.2. EIS characterization and ECL behavior of the modified electrode Fig. 3A shows the ECL behavior of differently modified electrodes in 0.10 M PBS (pH 7.0) containing 0.10 M K2S2O8. Bare GCE produced a weak ECL signal in the detection solution (curve a). Compared with the bare GCE, an enhanced ECL signal was detected at both the C60/GCE (curve b) and L-cys–C60/GCE (curve c). As expected, the proposed sensor (AuNPs@C60/GCE) presented the strongest ECL signal (curve d). This fact indicates that all of the C60, L-cys and AuNPs would accelerate the electron transfer in ECL reaction, thereby enhancing the ECL signal of the modified electrode. Obviously, the combination of C60, L-cys and AuNPs would be more beneficial to the improvement of ECL sensor for the detection of phenolic compounds in this experiment. In order to confirm that L-cys can increase the charge transfer rate, the electrochemical impedance spectroscopy (EIS) was investigated and Fig. 3B shows the typical Nyquist plots of bare GCE (curve a), C60/GCE (curve b) and L-cys–C60/GCE (curve c). In the EIS,

the semicircle diameter of semicircle portion at higher frequencies equals the electron-transfer resistance (Ret), which relates to the electron-transfer-limited process. Compared with the bare GCE (curve a), a bigger semicircle domain was observed in EIS of C60/GCE (curve b), indicating a higher Ret on the C60/GCE, which was because the C60 modified film with a certain thickness would increase the electron-transfer distance between the redox probe [Fe(CN)6]4  /3  and the electrode, thus resulting in an increase in electron transfer resistances. As expected, the Ret of L-cys–C60/GCE was remarkably lower than that of C60/GCE, revealing the fact that L-cys can decrease the charge transfer resistances between the redox probe [Fe(CN)6]4  /3  and the electrode. Thereby, it is reasonable to draw the conclusion that L-cys can increase the charge transfer rate. In fact, Tian et al. (2002) have reported that cysteine can promote the rapid and direct electron transfer between superoxide dismutase and the electrode. Furthermore, they further confirmed that a series of COOH-terminated aliphatic thiols and disulfides with a short alkylene chain [__(CH2)__ n , (n ¼1, 2, 3)] were favorable for the electron transfer (Tian et al., 2004).

3.3. Optimization of experimental conditions The experimental conditions including the pH of PBS and the concentration of K2S2O8 were optimized since they would affect the performance of ECL sensor. The change in ECL intensity (ΔI) was tested at AuNPs@C60/GCE in 0.10 M PBS with varied pH in the range from 5.0 to 9.0. As evident from Fig. 4A, in the presence of constant concentration of K2S2O8 (0.10 M) and catechol (35 mM), the ΔI can be significantly influenced by the pH of detection

400 a

b

d

300 -Z''(ohm)

ECL Intensity / a.u.

1500

1000 a

500

c 200 100

0 6

7

8 Time / s

9

0

10

250

500

750 Z'(ohm)

1000

1250

2500

2400

2000

1800 ΔI / a.u.

ΔI / a.u.

Fig. 3. (A) ECL profiles of (a) bare GCE, (b) C60/GCE, (c) L-cys–C60/GCE and (d) AuNPs@C60/GCE in 0.10 M PBS (pH 7.0) containing 0.10 M K2S2O8. (B) EIS of (a) bare GCE, (b) C60/GCE and (c) L-cys–C60/GCE.

1500

1200 600

1000 5

6

7 pH

8

9

0 0.04

0.06 0.08 0.10 Concentration of K

0.12

Fig. 4. (A) Effect of pH on the ΔI of AuNPs@C60/GCE in 0.10 M K2S2O8 solution. (B) Effect of K2S2O8 concentration on ΔI of AuNPs@C60/GCE in 0.10 M PBS (pH 7.0).

Q. Lu et al. / Biosensors and Bioelectronics 60 (2014) 325–331

ECL Intensity / a.u.

8000 ECL Intensity / a.u.

k

6000 a

4000

8000

329

J

6000 a

4000 2000

2000

0

0 6

7

8 Time / s

9

ECL Intensity / a.u.

8000

6

10

7

8 Time / s

9

10

h

6000 a

4000 2000 0 6

7

8 9 Time / s

10

11

Fig. 5. The ECL intensity of the AuNPs@C60/GCE for (A) CC, (B) HQ and (C) PC in pH 7.0 PBS containing 0.10 M K2S2O8y. [CC]: 0.0, 0.062, 1.31, 3.81, 8.31, 13.8, 23.8, 33.8, 53.8, 73.8 and 124 μΜ. [HQ]: 0.0, 0.05, 1.05, 2.05, 7.05, 23.0, 33.0, 48.0, 73.0 and 113 μΜ. [PC]: 0.0, 0.05, 8.05, 13.0, 23.0, 38.0, 68.0 and 108 μΜ. Inset: calibration curves for CC, HQ and PC.

solution, and pH 7.0 is the most suitable for optimum ECL measurement of catechol at the sensor. The concentration of K2S2O8 in the detection solution was optimized. The change in ECL intensity (ΔI) was tested at AuNPs@C60/GCE in 0.10 M PBS (pH 7.0) containing constant concentration of catechol (35 mM) and different concentrations of K2S2O8 in the range from 0.050 to 0.12 M. The results are shown in Fig. 4B. According to the result of the experiment, optimum concentration of K2S2O8 was achieved as 0.10 M. 3.4. ECL detection of phenolic compounds Fig. 5 depicts the ECL response of AuNPs@C60/GCE towards a series of concentrations of catechol (CC), hydroquinone (HQ) and p-cresol (PC). As shown in Fig. 5A, with the increase in concentration of CC (curve a), the ECL intensity enhanced. Under optimum conditions, there was a linear relationship between the change in ECL intensity (ΔI) and the concentration of CC with the linear range of 6.2  10  8–1.2  10  4 Μ, while the detection limit (signal to noise ¼3) was 2.1  10  8 Μ. The linear regression equation CC was expressed as ΔICC(a.u.) ¼53.63CCC (μΜ) þ507.16 (R ¼0.9941). The inset shows the corresponding calibration curve. Furthermore, other types of phenols such as HQ and PC were found to be able to enhance the ECL signal of the peroxydisulfate system. Based on this fact, HQ and PC were also detected using the proposed sensor and the results are presented in Figs. 5B and C, respectively. The linear ranges for HQ and PC were 5.0  10  8–1.1  10  4 M and 5.0  10  8–1.1  10  4 M, while the detection limits (signal to noise ¼ 3) were 1.5  10  8 Μ and 1.7  10  8 Μ, respectively. The linear equations were ΔIHQ(a.u.) ¼60.61CHQ (μΜ) þ648.55 (R ¼0.9907) and ΔIPC(a.u.) ¼ 48.10CPC (μΜ)þ863.61 (R¼ 0.9912),

respectively. Table 1 exhibits details of a comparison between the proposed method and previous methods. As can be seen, the linear range of proposed sensor was improved compared with previous works. In this work, the linear range achieved four orders of magnitude, which was wider than that of previous works. Furthermore, our proposed sensor exhibited a low detection limit, on the order of 10  8 M, which was lower than that of most sensors. Although a relatively lower limit of 10  9 M was reported by Lu et al. (2010), the linear range was obviously narrower than that of our work, only achieving two orders of magnitude. The above fact indicated that our proposed sensor exhibited excellent performance for the determination of phenolic compounds such as wide linear range and low detection limit. According to the reference (Yao et al., 2008), the possible mechanisms of ECL response are as follows. Firstly, S2 O8 2  was reduced to SO4   , a strong oxidant. Meanwhile, dissolved O2 was reduced to OOH. Then, SO4   was reacted with OOH to obtain 1 ðO2 Þn2 which acts as light-emitting species. The mechanisms are presented as follows: S2 O8 2  þ e-SO4 d  þSO4 2 

ð1Þ

SO4 d  þ H2 O-HOd þ HSO4 

ð2Þ

HOd þ H2 O-HOOd þ H2

ð3Þ

O2 þ H2 O þ e-HOOd þ HO 

ð4Þ

SO4  þ HOOd -HSO4  þ 1 ðO2 Þn2

ð5Þ

1

ðO2 Þn2 -23 O2 þ hυ

ð6Þ

330

Q. Lu et al. / Biosensors and Bioelectronics 60 (2014) 325–331

Table 1 Comparison between other methods and proposed methods in this work. Sensor

Method

Analyte

Concentration range(Μ)

Detection limit (M)

References

CdS nanotubes/indium thin oxide electrode

ECL ECL

Gold nanoparticles/polyacrylonitrile nanofibers/GCE Three-dimensional graphene/MWCNTs/BMIMPF6 nanocomposite modified electrode L-Cysteine gold nanoparticles/L-cysteine/gold nanoparticles film modified electrode

ECL DPVa

CdTe quantum dots/chitosan-modified GCE Hydroxyapatite/chitosan/tyrosinase-modified Au electrode

ECL Amperometric measurement ECL

2.0  10  6–1.0  10  5 4.0  10  5–1.4  10  4 1.0  10  6–8.0  10  5 1.0  10  6–6.0  10  5 5.5  10  7–3.7  10  5 5.0  10  7–2.9  10  3 2.0  10  6–6.6  10  4 1.0  10  6–1.6  10  4 2.0  10  6–1.15  10  4 2.0  10  6–1.05  10  4 2.0  10  7–1.0  10  5 1.0  10  8–7.0  10  6

5.8  10  8 6.4  10  7 3.0  10  7 3.0  10  7 8.0  10  8 6.0  10  8 1.0  10  7 3.0  10  7 6.7  10  7 1.0  10  6 2.5  10  8 5.0  10  9

Wen et al. (2012)

Graphene/multiwall carbon nanotubes/gold nanoclusters/GCE

Catechol Hydroquinone Catechol Hydroquinone Hydroquinone Catechol Hydroquinone Catechol Hydroquinone p-Cresol Hydroquinone Catechol Catechol Hydroquinone

6.2  10  8–1.2  10  4 5.0  10  8–1.1  10  4

2.1  10  8 1.5  10  8

This work

AuNPs@C60/GCE

a

ECL

Yuan et al. (2013b) Liu et al. (2011) Wang et al. (2014) Yuan et al. (2013a)

Liu et al. (2010) Lu et al. (2010)

DPV, differential pulse voltammetry.

The stability of the ECL responses of AuNPs@C60/GCE was investigated in the peroxydisulfate solution with 35 mM catechol. It was found that the electrode lost about 13.2% of its original response after two weeks. In order to demonstrate the anti-interference of the sensor, 0.10 M interfering species such as Na þ , K þ , Cl  , Br  , Mg2 þ , Zn2 þ , and NO4  were added into the analysis solution containing 35 mM catechol. The results indicate that these substances do not result in noticeable change in ECL signal for the detection of catechol. Thus, the sensor has high selectivity for the phenolic compounds.

ECL Intensity / a.u.

4500

3000

1500

0 20

40 Time / s

60

3.6. Analytical application of the sensor in real samples

Fig. 6. The ECL stability of the constructed sensor to 35 μΜ CC.

Table 2 Recoveries of CC, HQ and PC in the river water sample at AuNPs@C60/GCE. Sample

Added (μΜ)

Found (μΜ)

Recovery (%)

Catechol

25.0 45.0 75.0 25.0 45.0 75.0 25.0 45.0 75.0

24.7 46.2 73.9 26.3 44.5 72.4 23.9 43.8 75.5

98.8 103 98.5 105 98.9 96.5 95.6 97.3 101

Hydroquinone

p-Cresol

In the proposed strategy, the phenolic compounds adsorbed onto the AuNPs@C60/GCE accelerate the electron transfer between the AuNPs@C60 hybrid and the substrate electrode, thus, greatly enhancing the ECL intensity. 3.5. Stability and interference determination of the sensor AuNPs@C60/GCE was used to detect catechol (35 mM) by ECL under optimum conditions. The relative standard deviation (R.S.D.) was 1.5% for 9 successive detections (Fig. 6).

The constructed ECL sensor was used to detect CC, HQ and PC in river water samples using the standard addition method. The results are exhibited in Table 2. The recoveries ranged between 95.6% and 105%. The result shows that AuNPs@C60/GCE had promising applications to detect phenolic compounds in the environment.

4. Conclusions A novel AuNPs@C60 sensor system was proposed for detecting phenolic compounds. Due to the integration of the outstanding ECL behaviors of C60, L-cys and AuNPs, the AuNPs@C60 nanocomposites provide a promising material to develop ECL phenolic compounds sensors. The resulting sensor exhibits remarkable performances such as high sensitivity, low detection limit, wide linear range and good reproducibility for detecting phenolic compounds.

Acknowledgments This work was supported by the National Natural Science Foundation of China (21075100 and 21275119), Specialized Research Fund for the Doctoral Program of Higher Education (20100182110015), the State Key Laboratory of Electroanalytical Chemistry (SKLEAC 2010009), the Natural Science Foundation Project of Chongqing City (CSTC2011BA7003), and the Fundamental Research Funds for the Central Universities (XDJK2012A004).

Q. Lu et al. / Biosensors and Bioelectronics 60 (2014) 325–331

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An electrogenerated chemiluminescence sensor based on gold nanoparticles@C60 hybrid for the determination of phenolic compounds.

This paper described a novel strategy for the construction of an electrogenerated chemiluminescence (ECL) sensor based on gold nanoparticles@C60 (AuNP...
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