Electrochemical preparation of activated graphene

Journal of Colloid and Interface Science 500 (2017) 54–62

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Regular Article

Electrochemical preparation of activated graphene oxide for the simultaneous determination of hydroquinone and catechol Murugan Velmurugan a, Natarajan Karikalan a, Shen-Ming Chen a,⇑, Yi-Hui Cheng a, Chelladurai Karuppiah a,b a Electroanalysis and Bioelectrochemistry Lab, Department of Chemical Engineering and Biotechnology, National Taipei University of Technology, No. 1, Section 3, Chung-Hsiao East Road, Taipei 106, Taiwan, ROC b Department of Chemistry, National Taiwan University, No.1, Section 4, Roosevelt Road, Taipei 106, Taiwan, ROC

g r a p h i c a l a b s t r a c t Electrochemical activation of graphene oxide for the effective determination of hydroquinone and catechol.

a r t i c l e

i n f o

Article history: Received 31 January 2017 Revised 29 March 2017 Accepted 30 March 2017 Available online 31 March 2017 Keywords: Screen printed carbon electrode Electrochemical activation Differential pulse voltammetry Graphene oxide Real sample analysis

a b s t r a c t This paper describes the electrochemical preparation of highly electrochemically active and conductive activated graphene oxide (aGO). Afterwards, the electrochemical properties of aGO was studied towards the simultaneous determination of hydroquinone (HQ) and catechol (CC). This aGO is prepared by the electrochemical activation of GO by various potential treatments. The resultant aGOs are examined by various physical and electrochemical characterizations. The high potential activation (1.4 to 1.5) process results a highly active GO (aGO1), which manifest a good electrochemical behavior towards the determination of HQ and CC. This aGO1 modified screen printed carbon electrode (SPCE) was furnished the sensitive detection of HQ and CC with linear concentration range from 1 to 312 lM and 1 to 350 lM. The aGO1 modified SPCE shows the lowest detection limit of 0.27 lM and 0.182 lM for the HQ and CC, respectively. The aGO1 modified SPCE reveals an excellent selectivity towards the determination of HQ and CC in the presence of 100 fold of potential interferents. Moreover, the fabricated disposable aGO1/SPCE sensor was demonstrated the determination of HQ and CC in tap water and industrial waste water. Ó 2017 Elsevier Inc. All rights reserved.

⇑ Corresponding author. E-mail address: [email protected] (S.-M. Chen). http://dx.doi.org/10.1016/j.jcis.2017.03.112 0021-9797/Ó 2017 Elsevier Inc. All rights reserved.

M. Velmurugan et al. / Journal of Colloid and Interface Science 500 (2017) 54–62

1. Introduction The separation and determination of the organic isomers are considerably receives a great importance in analytical chemistry. For instance, the hydroquinone (HQ) and catechol (CC) are the isomers of dihydroxybenzene, which are widely used in the preparation of pesticides, medicines, cosmetics, dye, flavoring agents, antioxidant and photography chemicals [1,2]. The use of HQ and CC are unavoidable, however, the HQ and CC can cause the headache, fatigue, kidney damage and decrease in liver function [3,4]. Recent studies revealed that the HQ and CC induces the DNA damage and can cause cancer in humans [5]. Moreover, these are classified as the priority pollutants by US Environmental Protection Agency (EPA) [6]. Hence, a sensitive and selective method needed to determine the HQ and CC. So far, several analytical methods have been developed, which includes the high performance liquid chromatography [7], gas chromatography/mass spectrometry [8], synchronous fluorescence [9], spectrophotometry [10] and electrochemical methods [11]. Among all, the electrochemical method is a low cost, fast response and simple operation technique, besides that, it provides the high sensitivity and excellent selectivity [12]. However, in electrochemical method, a major problem arises with the redox properties of the HQ and CC, which are generally overlapped together for the unmodified electrodes. Hence, some modified electrodes developed for the simultaneous determination of HQ and CC based on carbon nanotubes [13], mesoporous platinum [14], mesoporous carbon [15] and carbon ionic liquid [16]. In particular, the graphene based modified electrodes are exhibited the high performance due to the high surface area and good electrical conductivity. The graphene or its derivatives are the well known two dimensional (2D) carbon nanomaterials consist of sp2 carbon network and oxygen functionalities [17]. These are widely used for the fabrication of sensors and biosensors due to their attractive physical and electrochemical properties [18,19]. The graphene based nanomaterials are typically derived from graphene oxide (GO) because of its different functional groups such as ketones, epoxides, esters and carboxylic acids. These functional groups are helps to the electrode modification and act as a well support for various metal oxides. Recently, Ruoff group reported a highly porous graphenederived carbon nanomaterial based on the chemical activation process [20]. In which, the microwave-exfoliated graphite oxide (MEGO) and thermally exfoliated graphite oxide (TEGO) was subjected to KOH activation that results the highly enhanced surface area and good electrical conductivity [20]. Later, they have prepared the activated reduced graphene oxide (aGO) by the KOH and thermal treatment. The resultant activated graphene oxides furnished excellent electrochemical behavior compare to the ordinary GO [21]. Inspired by their work, we have prepared the activated graphene oxide (aGO) by electrochemical activation. In this

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method, we have avoided the chemical oxidant and high temperature annealing. The electrocatalytic activity of the aGO varying by altering the activation potential. The resultant aGO was examined by various physicochemical characterizations. The electrochemical behavior of the HQ and CC at aGO produced a distinct redox couple for the oxidation-reduction of HQ and CC whereas the ordinary GO exhibits the overlapped redox peak. Moreover, aGO modified screen printed carbon electrode (SPCE) was used as a disposable sensor for the determination of HQ and CC in water samples. 2. Experimental 2.1. Materials and methods Hydroquinone, catechol, resorcinol, phenol, ascorbic acid, glucose, uric acid and graphite powder (average diameter >20 lM) were purchased from Sigma Aldrich and screen printed carbon electrode was obtained from Zensor R&D Co., LTD, Taiwan. All the samples are used as received without any further purification and the solutions were prepared by milli-Q water. All the electrochemical experiments were performed in the 0.05 M phosphate buffer (PB) solution by using Na2HPO4 and NaH2PO4 solutions and the pH of the electrolyte was maintained to 7.0. Differential pulse voltammetry (DPV) and cyclic voltammetry (CV) experiments were carried out by CHI 900 electrochemical work station. The surface morphology of the aGO was examined by using scanning electron microscopy (SEM Hitachi S-3000 H). Raman spectra were obtained from a Raman spectrometer (Dong Woo 500i, Korea) equipped with a charge-coupled detector. All the electrochemical studies were performed in a conventional three electrode cell system, in which, screen printed carbon electrode (SPCE with working area = 0.07 cm2) as a working electrode, saturated Ag/AgCl (saturated KCl) as a reference electrode and platinum wire as a counter electrode. The DPV studies were recording by applying the potential window from 0.5 to 0.8 V with the optimized pulse amplitude (0.05 V) and pulse width (0.05 s). 2.2. Electrochemical activation of GO The GO was prepared by the modified Hummer’s method as reported previously [40]. The 10 mg of GO was dispersed in 2 mL of deionized water and ultrasonicated for 30 min. The 6 mL of well dispersed solution of GO suspension was drop casted on the SPCE and dried at room temperature. The resultant GO modified SPCE was subjected to the electrochemical activation in 0.1 M Na2SO4 at a scan rate of 50 mV/s. The electrochemical activations were carried out in different potentials ranging from 0.0 to 1.5 V (Fig. 1a), 0.5 to 1.5 V (Fig 1b) and 1.4 to 1.5 V (Fig. 1c). In all those activation processes, the reduction potential was applied up to 1.5 V

Fig. 1. CV responses of electrochemical activation for the various potentials; 0 to 1.5 V (a), 0.5 to 1.5 V (b) and 1.4 to 1.5 V (c).

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Fig. 2. (a) FT-IR spectra of GO and aGO, (b) Raman spectra of GO and aGOs, (c and d) SEM images of GO and aGO.

because according to Guo et al., the hydroxyl and epoxy groups were hardly reduced at a more negative potential (i.e., 1.5 V vs. SCE) [22]. However, the anodic potential was increased from 0 to 1.4 V for the further activation. This activation process furnished the electrochemically active functional groups on GO with various surface functionalities for the aGO1 (1.4 to 1.5), aGO2 (0.5 to 1.5) and aGO3 (0 to 1.5). These activated aGO modified SPCEs were gently washed with deionized water and dried in room temperature. These aGO modified SPCEs were further used for the physical and electrochemical characterizations.

3. Results and discussion 3.1. Selection of materials Generally, the graphene based nanomaterials are employed in several electrochemical sensor applications due to its versatile physicochemical properties. The graphene can be synthesized by the reduction of GO by various processes. In which, the electrochemical reduction process eliminates the oxygen functionalities from GO and furnished more sp2 carbon networks [20,21]. Herein, we choose the electrochemical activation process to increase the electrochemically active functional groups on GO. This electrochemical activation process was manifested a highly activated GO which revealed the high electrochemical capacitance compare to GO. Among the reported carbon nanomaterials, the aGO

exhibited a superior electrocatalytic activity towards the simultaneous determination of HQ and CC [13,15,16]. 3.2. Characterizations Fig. 2a shows the FT-IR spectra of GO and aGO, the predominant peaks were observed at approximately 3400 cm1, 1500– 1540 cm1, 1370–1391 cm1 and 1100 cm1 for the OAH stretching of carboxyl groups, C@C stretching of graphitic carbon, epoxy CAO vibration and alkoxy CAO stretching vibrations, respectively [23]. Almost all those characteristic peaks of oxygen functionalities in GO progressively displaced for the aGO. The electrochemical activation was highly reduced the alkoxy CAO and carboxylic AOH groups. However, the C@C vibration mode remain unchanged for the aGO, this results confirmed that electrochemical activation furnished the GO to target graphene material [24]. In addition, the defects and disorder of the activated GOs are assessed by Raman spectroscopy. Fig. 2b shows the Raman spectrum of GO and activated GOs, where all the compounds exhibited the typical D and G bands. Among all, the high potential activated GO (aGO1) shows the high disorder band (D), which confirmed that the aGO1 has less oxygen functionalities. These less oxygen functionalities are motivates the GO to high electrochemical activities. The surface morphology of the GO and aGO were assessed by SEM. Fig. 2c and d displays the SEM image of GO and aGO, which reveals the layered sheet like morphology for GO and aggregated layered flake like morphology for the aGO. These results confirmed that


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reversible redox reaction of [Fe(CN)6]3/4. The electro active surface area of the modified electrode was calculated by the Randles–Sevcik equation [26]:

ip ¼ 2:69 105 n3=2 A D1=2 C t1=2

Fig. 3. Electrochemical impedance spectra of GO and activated GOs.

the electrochemical activation process was successfully modified the GO to target graphene material. 3.3. Electrochemical behavior of aGO modified SPCEs In order to assess the electrochemical properties of aGO/SPCEs, the [Fe(CN)6]3/4 system was used as a probe. This case, EIS spectra provide the information about the electrode-electrolyte interface properties of modified SPCEs. Fig. 3 depicts the EIS spectrum of aGO1/SPCE, aGO2/SPCE, aGO3/SPCE, GO/SPCE recorded in 0.1 M KCl containing 5 mM [Fe(CN)6]3/4 redox probe. The EIS of GO/SPCE revealed a larger semicircle with a charge transfer resistance (Rct) of 11.4 kX, this is quite high compared with other modified SPCEs. This high value of Rct implies that the GO/SPCE has very low electron transfer ability due to high oxygen functionalities. These oxygen functional groups are created the more resistance at interface, hence GO/SPCE was unable to conduct the electrons as good as aGO/SPCEs. The EIS spectrum of other aGO/SPCEs exhibited the Rct values of 0.645, 2.85, 6.3 kX for the aGO1/SPCE, aGO2/SPCE, aGO3/SPCE, respectively. Among all modified SPCEs, aGO1/SPCE shows the lower semicircle which indicates that the higher electron transfer was observed when compared to other modified SPCEs. This high electron transfer capability was achieved by the high potential activation. Fig. 4a shows the CV responses of the aGO1/SPCE, aGO2/SPCE, aGO3/SPCE, GO/SPCE and bare SPCE were recorded in 0.1 M KCl containing 5 mM [Fe(CN)6]3/4 redox probe at a scan rate of 20 mV s1. Compared with the aGO/SPCEs, the redox peak current of the [Fe(CN)6]3/4 probe was almost vanished for the GO/SPCE. This is due to the more oxygen functional groups of GO, which holds nearly the insulating properties. Hence, it increased the internal resistance at electrode interface and blocks the diffusion of [Fe(CN)6]3/4 [25]. As a result, the mass transfer and electron transfer are hindered at the electrode surface. However, the aGO/ SPCEs revealed a well defined redox peaks for the [Fe(CN)6]3/4 probe, because most of the oxygen functionalities are reduced while the activation. The peak-to-peak potential separations (DEp) were obtained as 128, 114 and 100 mV for the aGO3/SPCE, aGO2/SPCE, and aGO1/SPCE respectively. In which, the aGO1/SPCE was exhibited a low DEp compare to the other modified SPCEs, because of the high potential activation. In contrast, the peak current of the [Fe(CN)6]3/4 probe was increased at the aGO1/SPCE. Moreover, the ratio of anodic to cathodic peak current (Ipa/Ipc) is 0.986 (1) for the aGO1/SPCE which further confirmed that the

ð1Þ

where ip is the peak current (A), C is the concentration of the [Fe(CN)6]3/4 molecules (taken to be 0.005 mol L1), A is the electrochemical active area (cm2), n is the number of electron transfer (1 e), D is the diffusion coefficient of [Fe(CN)6]3/4 molecules (7.6 106 cm2 s1) and t1/2 is the scan rate (V s1). From the slopes of the Ipa versus t1/2 the electro active surface areas were calculated to be 0.003, 0.039 (411.5 lA V s1), 0.041 (426.8 lA V s1) and 0.056 cm2 (577.6 lA V s1) for the GO/SPCE, aGO3/SPCE, aGO2/SPCE, and aGO1/SPCE respectively. These results indicated that the electrochemical activation process was furnished the electro active functional groups on GO, especially at high potential activation (1.4 to 1.5 V). Fig. 4b displays the CV responses of the aGO1/SPCE, aGO2/SPCE, aGO3/SPCE, GO/SPCE and bare SPCE in 0.05 M PB solution (pH = 7.0) at a scan rate of 50 mV/s. Here, the aGO1/SPCE exhibited the redox peak for the electro active functional groups of aGO1 whereas the GO/SPCE and other aGO/SPCEs show no appreciable redox peak, besides, it exposes only the double-layer capacitance behavior. However, the background current was much increased for the aGO2/SPCE and aGO3/SPCE compare to the GO/SPCE. This electrochemical behavior of aGO/SPCEs confirmed that the GO was successfully activated by the electrochemical treatment and showed the evidence for electro active functional groups. 3.4. Electrochemical behavior of HQ and CC Fig. 4c depicts the CV responses of the electrochemical behavior of 100 lM HQ and 100 lM CC at aGO1/SPCE, aGO2/SPCE, aGO3/ SPCE, GO/SPCE and bare SPCE in 0.05 M PB solution (pH = 7.0) at a scan rate of 50 mV/s. It can be noticed that only a single oxidation peak was obtained for the GO/SPCE. This is may be assigned to overlapping the oxidation peak of HQ and CC. This phenomenon apprises that the HQ and CC cannot be differentiated by the GO/SPCE. However, it exhibited the two separated reduction peaks for the HQ and CC at 0.04 and 0.08 V. This reduction peaks disclose that the electrocatalytic reduction process was selective at particular potentials for HQ and CC. In the case of aGO/SPCEs, the well-separated oxidation peaks were arises at the potentials of 0.118 V and 0.222 V for the oxidation of HQ and CC, respectively. However, the aGO1/SPCE exhibited the well shaped oxidation and reduction peaks compare to other modified electrodes and revealed the high oxidation and reduction peak current. This can be achieved by the more electro active functional groups on the GO, further it promotes the fast electron transfer kinetics for the CC and HQ. On the basis of this observation, the aGO1/SPCE was further used for the simultaneous determination of HQ and CC. Fig. 4d shows the CV responses of the aGO1/SPCE in the absence and presence of 100 lM HQ and 100 lM CC in 0.05 M PB solution (pH = 7.0) at a scan rate of 50 mV/s. As seen by earlier, the aGO1/ SPCE exhibited the electrocatalytic responses for electro active functional groups of aGO1 in the absence of HQ and CC. In contrast, it revealed a strong redox peak for the HQ and CC with the DEp of 46 mV and 37 mV in presence of 100 lM HQ and 100 lM CC. This aGO1/SPCE was subjected to the simultaneous detection of HQ and CC in the presence of 100 lM HQ and CC. The good electrocatalytic redox responses were observed for the simultaneous detection of HQ and CC. However, the reduction peak potentials of HQ and CC were shifted to negative direction due to the interference of oxidative product (HQox and CCox) at the surface of aGO1/SPCE. Although, the oxidation peak potentials were not changed in simultaneous

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Fig. 4. CVs of GO/SPCE and aGO/SPCEs in 0.1 M KCl containing 5 mM [Fe(CN)6]3/4 (a) and in 0.05 M PB solution (b). The CV responses of GO/SPCE and aGO/SPCEs in presence of 100 lM HQ and 100 lM CC (c). Simultaneous determination of HQ and CC at aGO1/SPCE (d).

Fig. 5. CVs of aGO1/SPCE in HQ and CC for various scan rates ranging from 10 to 500 mV/s (a) and the corresponding plot of peak current vs. scan rate in (b).


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detection, hence this modified electrode can applied to the further studies.

behavior of HQ and CC at the surface of aGO1/SPCE was controlled by the adsorption controlled electrochemical process [28].

3.5. Effect of scan rate

3.6. Simultaneous determination of HQ and CC

The scan rate dependant electrocatalytic behavior of HQ and CC was investigated at the aGO1/SPCE by CV. Fig. 5a depicts the CV responses of the aGO1/SPCE recorded in 0.05 M PB solution (pH = 7.0) containing 100 lM HQ and CC for the various scan rates from 10 to 500 mV/s. The redox peak currents of HQ and CC were linearly increased with increasing the scan rates. The resultant peak potential was slightly shifted to the more positive and negative side when increasing the scan rates from 10 to 500 mV/s, because, the size of the diffusion layer is depends on the scan rate. In a lower scan rates, the diffusion layer has been grown much further from the electrode surface when compare to the higher scan rates [27]. Therefore the flux is significantly higher at the electrode surface when sweeping the potential at higher scan rates. As a result, it creates an internal resistance at the electrodeelectrolyte interface, hence the redox peak potential was shifted. Fig. 5b shows the plot of oxidation peak current vs. scan rate for the HQ and CC which exhibited the linearity with the linear regression equation Ipa (lA) = 0.114 ⁄ 106 A/mV s1 + 3.63 lA (R2 = 0.9966) for HQ and Ipa (lA) = 0.133 ⁄ 106 A/mV s1 + 6.15 lA (R2 = 0.9959) for CC. This study indicates that the electrocatalytic

DPV was used for the determination of HQ and CC at aGO1/ SPCE in the 0.05 M PB solutions (pH = 7.0) containing various concentrations of HQ (1–612 lM) and CC (1–579 lM). Fig. 6a displays the DPV responses of aGO1/SPCE, which exhibited the sharp response for the addition of 1 lM HQ with the coexistence of 50 lM CC. The CC has no effect on the determination HQ rather the peak current of the CC was decreased when increased the HQ concentration from 1 to 612 lM this is because of the accumulation of more HQ at the electrode surface which deviates the peak current of CC. The DPV responses of HQ oxidation were linearly increased when consecutively increased the concentration, which shows the linear over concentration range from 1 to 312 lM. From the calibration plot (Fig. 6b), the lowest detection limit (LOD) of HQ was calculated to be 0.27 lM. Fig. 6c shows the DPV responses of aGO1/SPCE for the various concentration of CC with co-existence of 50 lM HQ. The HQ doesn’t affect the electrocatalytic behavior of CC, comparatively, the response of the HQ was decreased. The aGO1/SPCE determined the CC with linear concentration range from 1 to 350 lM and the LOD 0.182 lM (Fig. 6d). Moreover, the aGO1/SPCE furnished

Fig. 6. DPV responses of aGO1/SPCE in various concentrations of HQ ranging from 1 to 612 lM in presence of 50 lM CC (a) and the corresponding calibration plot in (b). The DPVs of aGO1/SPCE in various concentrations of CC from 1 to 579 lM in presence of 50 lM HQ (c) and the corresponding calibration plot in (d).

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Fig. 7. DPVs of aGO1/SPCE for the simultaneous determination of HQ and CC ranging from 50 to 90 lM (a). DPV response of HQ and CC in the presence of interfering ions.

Table 1 Comparison of the analytical performances of HQ and CC with previous reported modified electrodes.

a b c d e f g h i

Modified electrode

pH

Analyte

Linear range (lM)

Detection limit (lM)

Reference

ECF-CPEa

7.0

HQ CC

1–200 1–200

0.40 0.20

[29]

SPEb/MWCNTs/AuNPs

7.0

HQ CC

2–730 2–730

0.39 0.26

[30]

AuNPs-CNFc/Au

7.0

HQ CC

9–500 5–350

0.86 0.36

[31]

PDA-RGOd/GCE

4.5

HQ CC

1–230 1–250

0.72 0.82

[32]

SBA-15/CPEe

5.0

HQ CC

55–550 20–320

0.60 0.50

[33]

Au/pAMTf-MWNTs

7.0

HQ CC

7.2–391.2 3.6–183.6

0.30 0.24

[34]

N-GCEg

5.0

HQ CC

5–260 5–260

0.2 0.2

[35]

P-rGOh

7.0

HQ CC

5–90 5–120

0.08 0.18

[36]

Graphene–Pd/GCE

4.0

HQ CC

75–5000 75–5000

1.25 1

[37]

NiO/MWCNT/GCE

6.0

HQ CC

7.4–56 7.4–56

0.039 0.015

[38]

AuNPs/Fe3O4-APTES-GO/GCEi

7.4

HQ CC

3–137 2–145

1.1 0.8

[39]

aGO1/SPCE

7.0

HQ CC

1–312 1–350

0.27 0.182

Present work

Electrospun carbon nanofiber-modified carbon paste electrode. Screen-printed electrode. Au nanoparticles-carbon nanofibers. Polydopamine-reduced grapheme oxide. Hydrophobic ionic liquid-functionalized SBA-15 modified carbon paste electrode. Poly-3-amino-5-mercapto-1,2,4-triazole. Nitrogenated GCE. Porous reduced graphene oxide. 3-Aminopropyl)triethoxysilane.

the determination of HQ and CC with sensitivity of 1.6 mA lM1 and 2.8 lA lM1 respectively. In addition, the simultaneous increment of the HQ and CC were performed in the 0.05 M PB solutions with concentration range from 50 to 90 lM (Fig. 7a). The resultant oxidation peak currents of HQ and CC increased when increased the concentration. The obtained analytical parameters were compared with the previously reported

modified electrodes and displayed in Table 1. Recently reported carbon based HQ and CC sensors were well demonstrated the determination of HQ and CC. In contrast, the aGO1/SPCE sensor electrode showed much improved analytical performance than that of previously reported sensors (Table 1). The aGO1/SPCE exhibited the better performance towards the simultaneous determination of HQ and CC compare to the previous reports.

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M. Velmurugan et al. / Journal of Colloid and Interface Science 500 (2017) 54–62 Table 2 Simultaneous determination of HQ and CC in real water samples by aGO1/SPCE. Samples

Added (lM)

Found (lM)

Recovery (%)

HQ

CC

HQ

CC

HQ

CC

Tap water

10 30

10 30

9.8 28.8

9.9 29.5

98.0 96.0

99.0 98.33

Industrial waste water

10 30

10 30

9.69 28.7

9.78 29.2

96.9 95.66

97.89 97.33

Therefore, the aGO1/SPCE can be a promising electrode for the sensitive and selective determination of HQ and CC. 3.7. Stability, selectivity and reproducibility Stability and selectivity is considerably important for the electrochemical sensor electrode, hence the aGO1/SPCE sensor was investigated for the stability test in presence of HQ and CC in 0.05 M PB solution (pH = 7.0). The aGO1/SPCE sensor exhibited the relative standard deviation (RSD) of 3.60% for the six fabricated sensors towards the determination of 100 mM HQ and 100 mM CC. The aGO1/SPCE sensor electrode was stored in below 10 °C when not in use and examined to the detection of HQ and CC for the successive weeks. This sensor was retains about 92.15% of its initial current response after 6 weeks. These results confirmed that the aGO1/SPCE sensor has an excellent stability and reproducibility. The selectivity of the disposable aGO1/SPCE sensor was evaluated in presence of 100 lM HQ and 100 lM CC with the co-existence of 100-fold excess of Na+, K+, Mg2+, Cu2+, Ca2+, Zn2+, Al3+, 10-fold excess of phenol and resorcinol. Moreover, it was analyzed in 10fold excess of ascorbic acid, glucose and uric acid. Fig. 7b shows the DPV responses of HQ and CC oxidation in presence and absence of the aforementioned interferents. These potential interfering ions doesn’t affect the determination of HQ and CC (signals change below 5%). This result exhibited that the disposable aGO1/SPCE sensor has an excellent selectivity in potential interfering ions. 3.8. Real sample analysis In order to evaluate the practicability of the disposable aGO1/ SPCE sensor, it was applied to the determination of HQ and CC in tap water and industrial waste water. The obtained results notified there was no HQ and CC in those samples, hence, the target analyte was added to that sample by spiked method. The samples are prepared by the appropriate dilution with standard solutions of HQ and CC. This samples are directly used for the determination by using the disposable aGO1/SPCE sensor and it was attains a good recoveries from 96 to 100%. The obtained recoveries of the HQ and CC were given in Table 2. 4. Conclusion In summary, we have developed a sensitive and selective HQ and CC sensor based on the electrochemically activated GO modified SPCE. The electrochemical activation process was successfully demonstrated and discussed towards the materials aspect. The activated GO exhibited the better electrochemical behavior compare to ordinary GO. The aGO1 modified SPCE manifested an excellent electrocatalytic performance than that of other activated GOs. The disposable aGO1/SPCE sensor was simultaneously determined the HQ and CC with the linear concentration range from 1 to 312 lM and 1 to 350 lM and the lowest detection limit of 0.27 lM and 0.182 lM, respectively. Moreover, the disposable aGO1/SPCE sensor showed good stability, selectivity and reproducibility. In addition, the fabricated disposable aGO1/SPCE sensor

was applied to the determination HQ and CC in the real sample analysis and gathered good recoveries. Therefore, the fabricated sensor is applicable for the determination HQ and CC in practical applications.

Acknowledgements This project was supported by the Ministry of Science and Technology, Taiwan, ROC.

References [1] M.M. Khodaei, A. Alizadeh, N. Pakravan, Polyfunctional tetrazolic thioethers through electrooxidative/Michael-type sequential reactions of 1,2- and 1,4dihydroxybenzenes with 1-phenyl-5-mercaptotetrazole, J. Org. Chem. 73 (7) (2008) 2527–2532. [2] Z. Zeng, W. Qiu, Z. Huang, Solid-phase microextraction using fused-silica fibers coated with sol-gel-derived hydroxy-crown ether, Anal. Chem. 73 (11) (2001) 2429–2436. [3] G.C. Jagetia, R. Aruna, Hydroquinone increases the frequency of micronuclei in adose-dependent manner in mouse bone marrow, Toxicol. Lett. 93 (2) (1997) 205–213. [4] L. Taysse, D. Troutaud, N.A. Khan, P. Deschaux, Structure-activity relationship of phenolic compounds (phenol, pyrocatechol and hydroquinone) on natural lymphocytotoxicity of carp (Cyprinus carpio), Toxicology 98 (1) (1995) 207– 214. [5] K. Hirakawa, S. Oikawa, Y. Hiraku, I. Hirosawa, S. Kawanishi, Catechol and hydroquinone have different redox properties responsible for their differential DNA-damaging ability, Chem. Res. Toxicol. 15 (2002) 76–82. [6] Environmental Protection Agency, Toxic Substance Control Act, E.P. Agency1, Washington, DC (1979). [7] A. Asan, I. Isildak, Determination of major phenolic compounds in water by reversed-phase liquid chromatography after pre-column derivatization with benzoyl chloride, J. Chromatogr. A 988 (1) (2003) 145–149. [8] S. Moldoveanu, M. Kiser, Gas chromatography/mass spectrometry versus liquid chromatography/fluorescence detection in the analysis of phenols in mainstream cigarette smoke, J. Chromatogr. A 1141 (1) (2007) 90–97. [9] M.F. Pistonesi, M.S.D. Nezio, M.E. Centurión, M.E. Palomeque, A.G. Lista, B.S.F. Band, Determination of phenol, resorcinol and hydroquinone in air samples by synchronous fluorescence using partial least-squares, Talanta 69 (5) (2006) 1265–1268. [10] P. Nagaraja, R.A. Vasantha, K.R. Sunitha, A new sensitive and selective spectrophotometric method for the determination of catechol derivatives and its pharmaceutical preparations, J. Pharm. Biomed. Anal. 25 (3) (2001) 417–424. [11] U. Binesh, P.L. Ru, S.M. Chen, Electrochemically synthesized Pt–MnO2 composite particles for simultaneous determination of catechol and hydroquinone, Sens. Actuat. B: Chem. 169 (2012) 235–242. [12] C.Y. Lin, A. Balamurugan, Y.H. Lai, K.C. Ho, A novel poly (3, 4ethylenedioxythiophene)/iron phthalocyanine/multi-wall carbon nanotubes nanocomposite with high electrocatalytic activity for nitrite oxidation, Talanta 82 (5) (2010) 1905–1911. [13] D.W. Li, Y.T. Li, W. Song, Y.T. Long, Simultaneous determination of dihydroxybenzene isomers using disposable screen-printed electrode modified by multiwalled carbon nanotubes and gold nanoparticles, Anal. Methods 2 (7) (2010) 837–843. [14] M.A. Ghanem, Electrocatalytic activity and simultaneous determination of catechol and hydroquinone at mesoporous platinum electrode, Electrochem. Commun. 9 (10) (2007) 2501–2506. [15] J. Yu, W. Du, F. Zhao, B. Zeng, High sensitive simultaneous determination of catechol and hydroquinone at mesoporous carbon CMK-3 electrode in comparison with multi-walled carbon nanotubes and Vulcan XC-72 carbon electrodes, Electrochim. Acta 54 (3) (2009) 984–988. [16] Y. Zhang, J.B. Zheng, Comparative investigation on electrochemical behavior of hydroquinone at carbon ionic liquid electrode ionic liquid modified carbon paste electrode and carbon paste electrode, Electrochim. Acta 52 (25) (2007) 7210–7216.

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[17] D.A. Dikin, S. Stankovich, E.J. Zimney, R.D. Piner, G.H. Dommett, G. Evmenenko, S.T. Nguyen, R.S. Ruoff, Preparation and characterization of graphene oxide paper, Nature 448 (7152) (2007) 457–460. [18] Y. Liu, D. Yu, C. Zeng, Z. Miao, L. Dai, Biocompatible graphene oxide-based glucose biosensors, Langmuir 26 (9) (2010) 6158–6160. [19] M. Velmurugan, N. Karikalan, S.M. Chen, Z.C. Dai, Studies on the influence of bcyclodextrin on graphene oxide and its synergistic activity to the electrochemical detection of nitrobenzene, J. Colloid Interface Sci. 490 (2017) 365–371. [20] Y. Zhu, S. Murali, M.D. Stoller, K.J. Ganesh, W. Cai, P.J. Ferreira, A. Pirkle, R.M. Wallace, K.A. Cychosz, M. Thommes, D. Su, Carbon-based supercapacitors produced by activation of graphene, Science 332 (6037) (2011) 1537–1541. [21] L.L. Zhang, X. Zhao, M.D. Stoller, Y. Zhu, H. Ji, S. Murali, Y. Wu, S. Perales, B. Clevenger, R.S. Ruoff, Highly conductive and porous activated reduced graphene oxide films for high-power supercapacitors, Nano Lett. 12 (4) (2012) 1806–1812. [22] H.L. Guo, X.F. Wang, Q.Y. Qian, F.B. Wang, X.H. Xia, A green approach to the synthesis of graphene nanosheets, ACS Nano 3 (9) (2009) 2653–2659. [23] C. Liu, K. Wang, S. Luo, Y. Tang, L. Chen, Direct electrodeposition of graphene enabling the one-step synthesis of graphene-metal nanocomposite films, Small 7 (9) (2011) 1203–1206. [24] X. Peng, X. Liu, D. Diamond, K.T. Lau, Synthesis of electrochemically-reduced graphene oxide film with controllable size and thickness and its use in supercapacitor, Carbon 49 (11) (2011) 3488–3496. [25] P. Wang, Z.G. Liu, X. Chen, F.L. Meng, J.H. Liu, X.J. Huang, UV irradiation synthesis of an Au–graphene nanocomposite with enhanced electrochemical sensing properties, J. Mater. Chem. A 1 (32) (2013) 9189–9195. [26] N. Karikalan, R. Karthik, S.M. Chen, M. Velmurugan, C. Karuppiah, Electrochemical properties of the acetaminophen on the screen printed carbon electrode towards the high performance practical sensor applications, J. Colloid Interface Sci. 483 (2016) 109–117. [27] M. Buleandra, A.A. Rabinca, C. Mihailciuc, A. Balan, C. Nichita, I. Stamatin, A.A. Ciucu, Screen-printed Prussian Blue modified electrode for simultaneous detection of hydroquinone and catechol, Sens. Actuat. B: Chem. 203 (2014) 824–832. [28] T. Gan, J. Sun, K. Huang, L. Song, Y. Li, A graphene oxide–mesoporous MnO2 nanocomposite modified glassy carbon electrode as a novel and efficient voltammetric sensor for simultaneous determination of hydroquinone and catechol, Sens. Actuat. B: Chem. 177 (2013) 412–418. [29] Q.H. Guo, J.S. Huang, P.Q. Chen, Y. Liu, H.Q. Hou, T.Y. You, Simultaneous determination of catechol and hydroquinone using electrospun carbon nanofibers modified electrode, Sens. Actuat. B: Chem. 163 (2012) 179–185.

[30] D.M. Zhao, X.H. Zhang, L.J. Feng, L. Jia, S.F. Wang, Simultaneous determination of hydroquinone and catechol at PASA/MWNTs composite film modified glassy carbon electrode, Colloids Surf., B 74 (2009) 317–321. [31] Z.H. Huo, Y.L. Zhou, Q. Liu, X.L. He, Y. Liang, M.T. Xu, Sensitive simultaneous determination of catechol and hydroquinone using a gold electrode modified with carbon nanofibers and gold nanoparticles, Microchim. Acta 173 (1–2) (2011) 119–125. [32] L.Z. Zheng, L.Y. Xiong, Y.D. Li, J.P. Xu, X.W. Kang, Z.J. Zou, S.M. Yang, J. Xia, Facile preparation of polydopamine-reduced graphene oxide nanocomposite and its electrochemical application in simultaneous determination of hydroquinone and catechol, Sens. Actuat. B: Chem. 177 (2013) 344–349. [33] S.Y. Dong, P.H. Zhang, Z. Yang, T.L. Huang, Simultaneous determination of catechol and hydroquinone by carbon paste electrode modified with hydrophobic ionic liquid-functionalized SBA-15, J. Solid State Chem. 16 (2012) 3861–3868. [34] C. Wang, R. Yuan, Y.Q. Chai, F.X. Hu, Simultaneous determination of hydroquinone, catechol, resorcinol and nitrite using gold nanoparticles loaded on poly-3-amino-5-mercapto-1,2,4-triazole-MWNTs film modified electrode, Anal. Methods 4 (6) (2012) 1626–1628. [35] X. Wang, M. Xi, M. Guo, F. Sheng, G. Xiao, S. Wu, S. Uchiyama, H. Matsuura, An electrochemically aminated glassy carbon electrode for simultaneous determination of hydroquinone and catechol, Analyst 141 (3) (2016) 1077– 1082. [36] H. Zhang, X. Bo, L. Guo, Electrochemical preparation of porous graphene and its electrochemical application in the simultaneous determination of hydroquinone, catechol, and resorcinol, Sens. Actuat. B: Chem. 220 (2015) 919–926. [37] M. Zhang, F. Gan, F. Cheng, Preparation of flower-like Pd–graphene composites for simultaneous determination of catechol and hydroquinone, Res. Chem. Intermed. 42 (2) (2016) 813–826. [38] L.A. Goulart, L.H. Mascaro, GC electrode modified with carbon nanotubes and NiO for the simultaneous determination of bisphenol A, hydroquinone and catechol, Electrochim. Acta 196 (2016) 48–55. [39] S. Erogul, S.Z. Bas, M. Ozmen, S. Yildiz, A new electrochemical sensor based on Fe3O4 functionalized graphene oxide-gold nanoparticle composite film for simultaneous determination of catechol and hydroquinone, Electrochim. Acta 186 (2015) 302–313. [40] D.R. Dreyer, S. Park, C.W. Bielawski, R.S. Ruoff, The chemistry of graphene oxide, Chem. Soc. Rev. 39 (2010) 228–240.