N–doped graphene quantum dots embedded in BiOBr nanosheets as hybrid thin film electrode for quantitative photoelectrochemical detection paracetamol

Electrochimica Acta 318 (2019) 422e429

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Electrochimica Acta journal homepage: www.elsevier.com/locate/electacta

Nedoped graphene quantum dots embedded in BiOBr nanosheets as hybrid thin film electrode for quantitative photoelectrochemical detection paracetamol Kai Gao a, Xue Bai a, b, *, Yi Zhang a, Yetong Ji a a

Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education, College of Environment, Hohai University, Nanjing, 210098, PR China National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety, Hohai University, Nanjing, 210098, PR China

b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 12 February 2019 Received in revised form 2 June 2019 Accepted 16 June 2019 Available online 17 June 2019

A facile strategy of electrophoretic deposition has been employed to fabricate a thin film photoelectrochemical (PEC) sensor of functionalized Nedoped graphene quantum dots (FeNGQDs) embedded in BiOBr nanosheets, which were prepared by a twoestep hydrothermal method, loaded onto indium etineoxide coated glass substrate (FeNGQDs/BiOBr/ITO). Electrophoretic deposition provides a mild and environmentally friendly method for PEC film formation. Multiple techniques were applied to investigate the electronic, optical properties and structure of FeNGQDs/BiOBr thin films photoelectrodes. It was found that FeNGQDs/BiOBr thin films with NGQDs/BiOBr heterojunction possess an enhanced charge transfer and absorption wavelengths under visible light, particularly when compared to pristine FeBiOBr films, thus producing an increase in the observed photocurrent. Sensing performance measurements showed the FeNGQDs/BiOBr/ITO photoelectrode has a higher photoelectric response current to paracetamol, it was used to detect trace paracetamol under visible light irradiation. The sensor exhibited a wide linear range, low detection limit and good sensitivity, given the photoactivity of NGQDs/BiOBr heterojunction. The developed PEC sensor displayed an acute response to paracetamol in a linear range of 0.01 mMe20.0 mM with a detection limit of 3.33 nM, under optimal conditions. Here we present evidence that FeNGQDs/BiOBr/ITO photoelectrode is a promising candidate for PEC analysis. © 2019 Elsevier Ltd. All rights reserved.

Keywords: Photoelectrochemical BiOBr Nedoped graphene quantum dots Electrophoretic deposition

1. Introduction Paracetamol (Neacetylepeaminophenol) is a ubiquitous drug used worldwide due to its antipyretic and analgesic properties, prolific in relief from headaches, fevers, neuralgia, arthritis and osteoarthritis [1,2]. However, the overdose of paracetamol is extremely harmful leading to childhood asthma, acute liver and kidney failure, and in many cases can prove fatal if left untreated [3]. Thus, the development of a simple, sensitive and accurate quantification tool for the analysis of paracetamol is vital, with the potential for application in quality control and clinical diagnostic analysis of paracetamolecontaining medicines. Traditional techniques for the detection and analysis of

* Corresponding author. Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education, College of Environment, Hohai University, Nanjing, 210098, PR China. E-mail address: [email protected] (X. Bai). https://doi.org/10.1016/j.electacta.2019.06.101 0013-4686/© 2019 Elsevier Ltd. All rights reserved.

paracetamol are not limited to, but include; titrimetry [4], UVevis spectrophotometry [5], capillary electrophoresis (CE) [6], high performance liquid chromatography (HPLC) [7], thermogravimetric analysis [8], and electrochemical techniques [9]. More recently the photoelectrochemical (PEC) method has attracted much attention for the potential development of PEC paracetamol sensors, not least because there is minimal instrumentation setup, in addition to simple sample preparation. Although the analysis of paracetamol has been extensively studied, to our knowledge there are no reports based on PEC sensors for detecting paracetamol. Similarly, a great deal of attention has focused on the use of BiOBr semiconductors, due to their narrow bandegap (around 2.85 eV) relative to the widely used TiO2 (3.2 eV) or ZnO (3.4 eV) [10]. Owing to BiOBr's high visibleelight responsive activity, and good physicochemical stability, various strategies have been developed for the preparation of BiOBrebased nanocomposites, with improved photocatalytic performance, examples of these include C3N4/BiOBr [11], BiOBr/ZnO [12], and BiOBr/CTFe3D [13].

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Several other heterostructures also been proven to act be excellent candidates for the fabrication of a novel class of optoelectronic devices, such as graphene quantum dots/BiOBr (GQDs/BiOBr) [14]. Such GQD nanoscale architectures could improve the photoactivity and photostability, whilst maintaining conductivity, a high specific surface area and good biocompatibility [15]. The doping of nitrogen atoms into GQD type structures, could further alter their distinctive optical properties and electronic characteristics, due to CeN configurations [16]. Ni et al. reports that Nedoped graphene/TiO2 nanocomposites exhibit excellent photoelectrochemical properties for use in antioxidant capacitance assays [17]. Therefore, NGQDs were assembled in designing the photoelectric responsive materials, which could further enhance the photoelectric signal. Electrophoretic deposition (EPD) is a simple and low cost technique employed for thin film deposition, particularly when compared to other similar methods such as soleairbrush technology [18], rotating disk electrode [19], ultrasonic spray pyrolysis [20] and reactive direct current magnetron sputtering [21]. EPD can be used for the fabrication of large area coatings, and has been found to result in enhanced adherence to the electrode surface, due to the formation of corresponding chemical bond [22]. Therefore, EPD offers important advantages for the deposition of nanostructured functional films with a high surface area [23]. In EPD, charged particles in a colloidal solution are moved and deposited on the electrode surface under the action of electric field force [24]. Ghrera et al. have successfully used electrophoretic deposition to grow carboxylemodified multiwalled carbon nanotubes (MWCNTs) on a patterned indiumetineoxide (ITO) coated glass substrate [25]. In summary, EPD offers an attractive approach for preparation of FeNGQDs/BiOBr/ITO electrode because of simple deposition conditions and the stable deposition effect. Herein, NGQDs/BiOBr nanocomposites functionalized with cetyltrimethyl ammonium bromide (FeNGQDs/BiOBr) were electrophoretic deposition on to an ITO, resulting in an FeNGQDs/ BiOBr/ITO photoelectrochemical sensor for paracetamol (PA) determination. Furthermore, the surfactant cetyltrimethyl ammonium bromide (CTAB) acted as an electron donor for NGQDs/BiOBr nanocomposites during the process of ITO electrode deposition under an electric field force. This process is outlined in Fig. 1. Investigation of the structural and optical properties of the PEC sensor, using a number of techniques, indicates that the PEC sensor exhibits high sensitivity and good stability for practical application of PA.

2. Experimental 2.1. Reagents and materials Bismuth nitrate pentahydrate (Bi(NO3)3$5H2O), cetyltrimethyl ammonium bromide (CTAB), paracetamol and acetone were purchased from SigmaeAldrich (USA). Potassium bromide (KBr), citric acid monohydrate (C6H8O7$H2O), urea (CO(NH2)2), sodium sulfate

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(Na2SO4), sulfuric acid (H2SO4), Sodium hydroxide (NaOH), ethylene glycol (EG), methanol (CH3OH), hydrogen peroxide (H2O2) and ammonia (NH3$H2O) were purchased from Chinese National Medicine Group Chemical Reagent Co., Ltd. (Shanghai, China). The indiumetin oxide (ITO) coated glass substrate were purchased from Zhuhai Kaivo Optoelectronic Technology Co., Ltd. (sheet resistance < 10 U/sq, China). All chemicals were used without further purification. All aqueous solutions were prepared with deionized water. 2.2. Apparatus Scanning electron microscopy (SEM, Hitachi Se4800, Japan) was performed at an acceleration voltage of 5.0 kV. Transmission electron microscopy (TEM) and higheresolution transmission electron microscopy (HReTEM) images were obtained on a JEOL JEMe2100F/CESCOR electron microscope equipped with a fieldeemission gun operating at 200 kV. Xeray photoelectron spectroscopy (XPS) was performed with an AXISeUltra instrument from Kratos Analytical using monochromatic Al Ka radiation (225 W, 15 mA, 15 kV) and loweenergy electron flooding for charge compensation. The optical absorption study was performed with UVevis diffuse reflectance spectra (Cary 5000, USA). Photoelectrochemical measurements and the electrochemical impedance spectroscopy (EIS) are recorded with a CHI 660E electrochemical workstation (CH Instruments, Shanghai, China). In this three electrode system, with the platinum electrode acts as a counter electrode, an Ag/AgCl (saturated KCl solution) reference electrode and a modified indium tin oxide working electrode. Photoelectrochemical experiments were conducted in 0.1 M Na2SO4 solution under a 300 W Xe arc lamp. In addition, the EIS measurements were conducted in a 0.1 M KCl solution containing 5 mM Fe(CN)6 3-. 2.3. Preparation of NGQDs NGQDs was synthesized according to Qu et al. [26]. Briefly, 0.21 g (1 mmol) citric acid and 0.18 g (3 mmol) urea were dissolved into 5 mL water and stirred. The solution was then transferred into a 20 mL Teflonelined stainless autoclave and heated to 160
C for 4 h in an electric oven. The product was further dialyzed in a dialysis bag (retained molecular weight: 1000Da) for 48 h and used in the next experiment. 2.4. Preparation of NGQDs/BiOBr nanohybrids Briefly, a total of 0.5 mmol Bi(NO3)3$5H2O was added to 10 mL of ethylene glycol under stirring at room temperature until dissolved, and then addition of 5 mL aseprepared NeGQDs solution containing 0.5 mmol of KBr. The mixture was subsequently transferred into a 50 mL Teflonelined stainless autoclave and heated at 120
C for 5 h. After cooling down to room temperature, the products were washed with distilled water and ethanol several times, and dried at 60
C for 6 h. 2.5. Preparation of modified electrodes

Fig. 1. Schematic for the fabrication of FeNGQDs/BiOBr/ITO sensor by EPD.

CTAB functionalized NGQDs/BiOBr (FeNGQDs/BiOBr) thin film were deposited on the ITO electrode using electrophoretic deposition (EPD) [27]. 300 mg of NGQDs/BiOBr nanohybrids were dispersed in 30 mL of water with CTAB (1%) solution and sonicated in water bath for 6 h, resulting in a highly stable white dispersion. Purification was by centrifugation at 5000 rpm before reedispersion in 30 mL acetone. ITO electrodes (4 cm  1.2 cm) were washed with acetone and water then hydrolized with a

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solution containing H2O:H2O2:NH3 (5:1:1) for about 1 h at 75
C. The above CTAB functionalized NGQDs/BiOBr nanohybrid materials are used as electrophoretic deposition colloidal solutions, deposited onto the ITO by application of a 15 V DC voltage for multiple time intervals (60, 120, 180, 240 and 300 s). Functionalization with CTAB results in an overall positive charge on the NGQDs/BiOBr nanohybrids resulting deposition onto the negatively charged ITO electrode by application of an electric field. In this EPD process, one ITO electrode acts as the cathode and the other separated by 1.0 cm served as the anode. After successful deposition of the FeNGQDs/ BiOBr the ITO electrodes were washed with DI water three times followed by drying. The working surface of the F-NGQDs/BiOBr/ITO electrode was 2.8  1.2 cm. 2.6. HPLC analysis of paracetamol The content of paracetamol in commercial pharmaceutical samples was determined using HPLC (Agilent 1260, Agilent Technologies Inc., USA) followed the methods performed as indicated in PHARMACOPOEIA OF THE PEOPLE’S REPUBLIC CHIAN. The chromatographic separation was applied using a mobile phase of water and methanol (60/40), through a C18 column (Eclipse PluseC18, 4.6  150 mm, 5 mm) and were analyzed at 273 nm by the ultravioletevisible (UV/VIS) variable wavelength detector (VWD G1314A, Agilent Technologies Inc, USA). The column temperature, the flow rate and the injection volume were set at 30
C, 20 mL and 1 mL/min, respectively. 3. Results and discussion 3.1. Characterization of the modified electrode and NGQDs/BiOBr nanocomposites The surface morphology of the PEC sensor and interior structure of the asesynthesized pure BiOBr and NGQDs/BiOBr products were characterized by SEM and TEM. As displayed in Fig. 2a, the bare ITO electrode surface appeared to be uniform and smooth, and following electrophoretic deposition of the FeNGQDs/BiOBr film onto the electrode surface, many uniform FeNGQDs/BiOBr nanoparticles can be observed (Fig. 2b). Fig. 2c shows the particle sizes of the pristine BiOBr were approximately 100e170 nm and appearing to have smooth surface. Addition of a specific volume of the NGQDs aqueous solution during BiOBr preparation, resulted in the production of a NGQDs/BiOBr heterojunction. NGQDs embedded in BiOBr nanosheets exhibits a relatively rough surface morphology upon comparison with BiOBr, this is due to the addition of NGQDs (Fig. 2d). An enlarged view of the TEM and HRTEM image shown in Fig. 2e and f indicates NGQDs embedded in BiOBr nanosheets. The HRTEM result also reveals the high crystallinity of the NGQDs, with a lattice spacing of 0.21 nm and a diameter of 10e20 nm. Fig. 3 shows Xeray photoelectron spectroscopy (XPS) and UVeVis diffuse reflectance spectroscopy (UVevis DRS) image of the prepared FeNGQDs/BiOBr/ITO, the chemical composition and oxidation states of the FeNGQDs/BiOBr nanocomposites have been investigated by XPS spectra. Each survey spectra shows four binding energy peaks at 68.9, 159.2, 284.8, and 531.3eV, which correspond to Br 3d, Bi 4f, C 1s, and O 1s, respectively, were shown in Fig. 3a. In addition to these four elements, the higheresolution spectra of N 1s was observed (inset of Fig. 3a) at the FeNGQDs/ BiOBr/ITO surface [28]. As depicted in Fig. 3b, two strong peaks at 159.6 and 164.9 eV are associated with Bi 4f7/2 and Bi 4f5/2, respectively, revealing the existence of Bi3þ. Fig. 3c shows the binding energies of Br 3d5/2 and Br 3d3/2 located at 68.6 and 69.6 eV, respectively，this has been assigned to Br in tetragonal BiOBr [29,30], whilst the peak at a binding energy of 69.1 eV were the

feature of Bi in cetyltrimethyl ammonium bromide. The C 1s (Fig. 3d) spectrum of FeNGQDs/BiOBr/ITO can be fitted into four peaks at 284.7, 285.3, 285.9, and 287.5eV, which can be correspond to CeC, CeN, C]N, and C]O, respectively [30,31]. As shown in Fig. 3e, the O1s can be deconvoluted into two peaks, the peak at 530.5 eV is attributed to crystal lattice O atoms (BiAO) in BiOBr, while the peak at 531.0 eV rises from C]O bonding [32], indicating that FeNGQDs/BiOBr/ITO electrode have been successfully prepared. Further study to investigate the optical properties of electrodes, the aseprepared FeNGQDs/BiOBr/ITO were measured by UVevis DRS in the wavelength range of 200e800 nm. UVevis DRS shows that the FeBiOBr/ITO electrode exhibited a steep absorption edge less than 439 nm (Fig. 3f, curve I), this is attributed to its hierarchical structure and the intrinsic visibleelight response ability [33]. When compared to the FeBiOBr/ITO electrode, the FeNGQDs/ BiOBr/ITO electrode exhibits a noticeable red shift in the absorption wavelength; implying a wider light absorption edge up to 459 nm (curve II). The band gap energy of the aseprepared electrode was calculated from the following equation:

aðhvÞ ¼ Aðhv  EgÞn=2

(1)

where a, h, v, A, and Eg are absorption coefficient, Planck's constant, photon frequency, constant and energy band gap, respectively [13]. As shown in Fig. 3f inset, the bandgap of FeNGQDs/BiOBr/ITO was calculated to be 2.76 eV (curve II), lower than that of FeBiOBr/ITO (2.85 eV, curve I). A lower band gap is beneficial for the electronic transitions and excitations, generating active species more easily. 3.2. Optimization of conditions The experimental parameters involved in the PEC sensor synthesis process for the fabrication of an optimal photoelectrochemical sensor for PA detection, have been optimized. The electrophoretic deposition time was found to have a great effect on the performances of the proposed sensor [23], this is seen in Fig. 4a showing the photocurrent response with increasing deposition time. A linear relationship is observed between increasing photocurrent and the corresponding deposition time, with the highest photocurrent signal response achieved at 3 min. This indicates increased amounts of FeNGQDs/BiOBr deposited on the electrodes, resulting in an increased photoelectric response ability, the photocurrent response plateaus at 4.6 mA, despite increasing deposition time. This plateau may be due to the thickness of the deposited layer, therefore, 3 min was selected as the optimal electrophoretic deposition time, for the development of the PA sensor electrode. The effect of pH on the PEC performance of FeNGQDs/BiOBr/ITO was also evaluated, in Na2SO4 with the pH range from 6 to 9. As shown in Fig. 4b, the photocurrent of the PEC sensor reached its maximum at pH 7. Hence, the pH value of 7 was exploited in subsequent studies. 3.3. EIS and photoelectrochemical behavior Nyquist plots of the aseprepared PEC electrodes are shown in Fig. 5a, these show a smaller arc radius in the high frequency region, which could be ascribed to chargeetransfer resistance (Rct), indicating efficient charge transfer [34]. A small semicircle for bare ITO, indicates a successful interface electron transfer resistance of 36.8U (curve I). After ITO was modified with FeBiOBr nanosheets, an increase in the resistance to 75.1 U (curve III), due to the poor conductivity of the BiOBr NPs. When FeNGQDs/BiOBr nanocomposites are used for ITO coating, the Rct value decreased to 48.9 U (curve II),

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Fig. 2. SEM images of bare ITO (a) FeNGQDs/BiOBr/ITO (b) BiOBr (c) and NGQDs/BiOBr nanoflakes (d). (e) TEM and (f) HRTEM and image of NGQDs/BiOBr.

indicating that the heterogeneous junction formed by NGQDs and BiOBr, is beneficial in enhancing the electron transport ability of the pristine BiOBr nanoplates. Therefore, EIS results suggest the successful fabrication of the PEC sensor. Further investigation of the photoinduced behavior of the various material coated electrodes, the photocurrent responses of bare ITO, FeBiOBr/ITO and FeNGQDs/BiOBr/ITO electrodes, when exposed to visible light are shown in Fig. 5b. It can be found that the photocurrent signal response of the FeBiOBr/ITO electrode was approximately 1.62 mA, showing improved photocurrent response when compared with the bare ITO electrode. This improved photocurrent response can be attributed to a higher electronehole separation efficiency on the surface of BiOBr [28]. The highest photoelectric response current, obtained by the FeNGQDs/BiOBr/ ITO electrode was found to be of 5.18 mA, this is owing to the formation of NGQDs/BiOBr heterojunction, which can reduce the recombination rate of the photogenerated electrons and holes [35]. This further enhances the PEC activity of the FeNGQDs/BiOBr nanohybrids. 3.4. Photocurrent behaviors of the modified photoactive electrodes Based on the performance of the electrode described above, the photocurrents of the modified electrode in 0.1 M Na2SO4 solution

was recorded (Fig. 6a). The photocurrent of FeNGQDs/BiOBr/ITO increased from 13.1 mA to 17.4 mA when 1 mM PA was added into the electrolyte solution. This phenomenon indicates that adding PA has a marked effect on the photocurrent of FeNGQDs/BiOBr/ITO. The possible mechanism for PA detection is proposed in Scheme 1. As we know, the band gap of NGQDs and BiOBr is about 1.7 eV and 2.85 eV, respectively [36], and the positions of the valence band (VB) and conduction band (CB) for NGQD are higher than those of BiOBr. When exposed to visible light irradiation, NGQD nanoparticles are excited and undergo charge separation to yield electrons (e) and holes (hþ). The photoegenerated electrons are then quickly transferred to BiOBr due to their differing CB energy levels, before the separated holes on VB of BiOBr can enter into NGQDs and further oxidise PA to obtain electrons for the continued to production of photoelectrons. The above explain further explains how FeNGQDs/BiOBr/ITO can be used for PA detection. Fig. 6b shows the photocurrent response of the FeNGQDs/BiOBr/ITO electrode in the presence of increasing PA concentration. The photocurrent of the sensor increases with the concentrations of PA. The linear regression equation for this response can be expressed as:

DIðmAÞ ¼ 5:606CðmMÞ þ 5:403ðr ¼ 0:9975Þ

(2)

The photocurrents display a linear range of 0e2 mM (inset of

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Fig. 3. XPS spectra of FeNGQDs/BiOBr: (a) survey scan (Inset: XPS of N 1s peaks of the FeNGQDs/BiOBr), (b) Bi 4f, (c) Br 3d, (d) C 1s, and (e) O 1s. (f) UVevis diffuse reflectance spectra of FeBiOBr (I) and FeNGQDs/BiOBr (II), Inset: the band gap energies of FeBiOBr (I) and FeNGQDs/BiOBr (II).

Fig. 4. (a) Effect of different deposition time on response current on FeNGQDs/BiOBr/ITO electrode in 0.1 M Na2SO4 solution. (b) Effect of different pH on the photocurrent response of FeNGQDs/BiOBr/ITO electrode in 0.1 M Na2SO4 solution.

Fig. 6b), with a limit of detection of 3.33 nM (S/N ¼ 3). As shown in Table 1, the FeNGQDs/BiOBr/ITO exhibited enhanced performance including wide linear range and low detection limit for PA detection when compared with the electrochemical sensors presented in previous studies.

3.5. Selectivity, reproducibility, and stability The selectivity of the fabricated PEC sensor has been evaluated by the photoelectrochemical detection of 0.1 mM PA in an Na2SO4 solution containing either 3 mM of ascorbic acid, dopamine, and uric acid, respectively. As shown in Fig. 7a, the photocurrent changes are

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Fig. 5. (a) Nyquist plot of various modified ITO electrodes in 5 mM K3Fe(CN)6 containing 0.1 M KCl: (I) bare ITO, (II) FeNGQDs/BiOBr/ITO, (III) FeBiOBr/ITO. (b) Photocurrent response of the modified ITO electrodes (I) bare ITO, (II) FeBiOBr/ITO, (III) FeNGQDs/BiOBr/ITO in 0.1 M Na2SO4 solution.

Fig. 6. (a) PEC responses of FeNGQDs/BiOBr/ITO electrode in the absence (I) and presence (II) of 1 mM PA in 0.1 M Na2SO4 solution. (b) Photocurrent response of FeNGQDs/BiOBr/ITO in 0.1 M Na2SO4 solutions in the presence 0, 0.01, 0.03, 0.05, 0.08, 0.1, 0.3, 0.5, 0.8, 1.0, 1.3, 1.5, 1.8, and 2 mM PA. Inset: calibration curve for PA on FeNGQDs/BiOBr/ITO based PEC sensor.

Fig. 7. (a) The interference study of related chemicals, 1 represent 0.1 mM PA in Na2SO4 solution, 2e4 represent 0.1 mM PA in Na2SO4 solution containing individually 3 mM ascorbic acid, dopamine, and uric acid, respectively. The error bar represents the response peak current of three independence experiments. (b) Stability of FeNGQDs/ BiOBr/ITO in Na2SO4 solution (pH 7) under illumination of a 300 W xenon lamp (with a visible light band pass filter glass, 390e770 nm) at 0 V (vs. Ag/AgCl) repeated every 90 s.

FeNGQDs/BiOBr/ITO electrodes in the presence of 1 mM PA using a single electrode for five times, with a relative standard deviation (RSD) of 2.6%, demonstrating superior reproducibility of this sensor. As shown in Fig. 7b, the response to 1 mM PA did not show any obvious change when the process was repeated at 90 s intervals, indicating that the PEC sensor was stable throughout, and the excellent reproducibility of the fabricated sensor. 3.6. Application in real sample Scheme 1. Electronetransfer mechanism of PEC sensor based on FeNGQDs/BiOBr/ITO electrode in Na2SO4 electrolyte containing PA.

less than 14% (n ¼ 3) for each of these reagents, indicating that it has negligible effect on PA detection at the photoelectrochemical sensor. It was found that the designed PA photoelectrochemical sensor has excellent antieinterference performance. The reproducibility of the sensor is examined by detecting photoresponses of

The feasibility of the fabricated photoelectrochemical sensor was explored by determining PA in commercial pharmaceutical samples, which was bought from the local drugstore. First, there paracetamol commercial tablets were ground to powders and the content of paracetamol in three tablets was determined by HPLC. The results show that the average concentration of paracetamol was detected to be 253 mg/tablet, which is in good agreement with the content of paracetamol (250 mg/tablet) provided by the manufacturer. Then the above paracetamol powders were

Table 1 Comparison of the major characteristics of several reported methods used in detecting PA. Electrode

Detection methods

Detection limit

Linear range (mM)

Reference

GAgD/GCE Co/CTS/f-MWCNTs/GCE FAPeCPE Pd/GO/GCE PEDOT/AG/GCE FeNGQDs/BiOBr/ITO

Chronoamperometry Differential Pulse Voltammetry Square Wave Voltammetry Differential Pulse Voltammetry Differential Pulse Voltammetry Photoelectrochemistry

0.025 mM 0.01 mM 5.8 nM 2.2 nM 0.041 mM 3.33 nM

0.025mMe0.5 mM and 0.5mMe10mM 0.1e400 mM 1000e4.00 mM and 200e0.04 mM 0.005e0.5 mM and 0.5e80.0 mM 0.15e5881.09 mM 0.01e2 mM

[38] [39] [40] [1] [2] This work

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K. Gao et al. / Electrochimica Acta 318 (2019) 422e429 Table 2 Detection of paracetamol in tablet (n ¼ 3). Sample

Labeled (mM))

Found (mM)

Recovery (%)

Compound paracetamol tablets (II)

0.06 0.6 1.6

0.05 0.67 1.63

83.3 111.7 101.9

dissolved in 0.1 M Na2SO4 solution and diluted to a working concentration range for the PEC determination. The mean percentage recoveries of paracetamol were found to be 83.3e101.9% using the proposed method (Table 2). The results indicate that the FeNGQDs/ BiOBr/ITO electrode has high sensitivity and selectivity for detecting PA in commercial pharmaceutical samples. 4. Conclusion A promising thin film photoelectrochemical sensor for detecting PA was constructed based on electrophoretic deposition of FeNGQDs/BiOBr on ITO electrode. The thin film FeNGQDs/BiOBr/ ITO electrodes prepared by electrophoretic deposition were not only simple and mild, but also have good detection stability. Moreover, the FeNGQDs/BiOBr/ITO electrode exhibited excellent PEC performance, specifically low detection limit, wide linear range as well as gratifying stability for the detection of trace PA under visible light illumination. This excellent performance of the electrode can be attributed to the formation of NGQDs/BiOBr heterojunction efficiently suppressed the recombination of photogenerated charges and the high photocatalytic. Thus, this thin film photoelectrochemical sensor may provide a unique opportunity for potential applications in clinical diagnostics with good selectivity, high sensitivity, acceptable reproducibility and stability. Acknowledgments The authors gratefully acknowledge the support provided by the National Natural Science Foundation of China (Grant No. 21876044), the Outstanding Youth Fund of Jiangsu province (Grant No. BK20170098), the Fundamental Research Funds for the Central Universities (Grant No. 2018B14414, 2018B42314), and a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions. References [1] J. Li, J. Liu, G. Tan, J. Jiang, S. Peng, M. Deng, D. Qian, Y. Feng, Y. Liu, Highsensitivity paracetamol sensor based on Pd/graphene oxide nanocomposite as an enhanced electrochemical sensing platform, Biosens. Bioelectron. 54 (2014) 468. [2] M. Li, W. Wang, Z. Chen, Z. Song, X. Luo, Electrochemical determination of paracetamol based on Au@graphene core-shell nanoparticles doped conducting polymer PEDOT nanocomposite, Sens. Actuators, B (2018) 260. [3] B.L. Woolbright, H. Jaeschke, Role of the inflammasome in acetaminopheninduced liver injury and acute liver failure, J. Hepatol. 66 (4) (2016) 836e848. [4] M.K. Srivastava, S. Ahmad, D. Singh, I.C. Shukla, Titrimetric determination of dipyrone and paracetamol with potassium hexacyanoferrate(III) in an acidic medium, Analyst 110 (1985) 735e737. [5] G. Abirami, T. Vetrichelvan, Simultaneous determination of Tolperisone and Paracetamol in pure and fixed dose combination by UV - Spectrophotometry, Int. J. Pharm. Pharm. Sci. 5 (2013) 488e492. [6] Q. Chu, L. Jiang, X. Tian, J. Ye, Rapid determination of acetaminophen and paminophenol in pharmaceutical formulations using miniaturized capillary electrophoresis with amperometric detection, Anal. Chim. Acta 606 (2008) 246e251. [7] M.H. Langlois, A. Vekris, C. Bousses, E. Mordelet, N. Buhannic, C. Seguard, P.O. Couraud, B.B. Weksler, K.G. Petry, K. Gaudin, Development of a solventfree analytical method for paracetamol quantitative determination in Blood Brain Barrier in vitro model, J. Chromatogr. B 988 (2015) 20e24. [8] M. Khanmohammadi, M. Soleimani, F. Morovvat, A.B. Garmarudi, M. Khalafbeigi, K. Ghasemi, Simultaneous determination of paracetamol and codeine phosphate in tablets by TGA and chemometrics, Thermochim. Acta

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