CeO2@Cu2O Carbon-Based Electrode To

Subscriber access provided by UNIV OF WESTERN ONTARIO

Article

Novel Nanostructured Pt/CeO2@Cu2O Carbon - Based Electrode to Magnify the Electrochemical Detection of the Neurotransmitter Dopamine and Analgesic Paracetamol Athimotlu Raju Rajamani, and Sebastian C. Peter ACS Appl. Nano Mater., Just Accepted Manuscript • DOI: 10.1021/acsanm.8b01217 • Publication Date (Web): 30 Aug 2018 Downloaded from http://pubs.acs.org on September 9, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Nano Materials

Novel Nanostructured Pt/CeO2@Cu2O Carbon - Based Electrode to Magnify the Electrochemical Detection of the Neurotransmitter Dopamine and Analgesic Paracetamol Athimotlu Raju Rajamani,1,2 Sebastian C. Peter1,2* New Chemistry Unit1, School of Advanced Materials2, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064, India. *E-mail: [email protected] Keywords:

Pt/CeO2@Cu2O,

Nanocomposite,

Electrochemical

sensor,

Drug

detection,

Dopamine, Paracetamol ABSTRACT The fabrication of nanocomposites is essential because a multi-phase interface delivers highly sensitive and selective method for the individual and simultaneous electrochemical determination of drugs. Herein, we introduce an electrochemical sensor using Pt/CeO2@Cu2O nanocomposites for simultaneous detection of dopamine (DA) and paracetamol (PA), which were synthesized using a low temperature clean aqueous phase additives-free method with Cu2O as sacrificial template. We investigated the electrochemical behavior of the various modified electrodes by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), in which Pt/CeO2@Cu2O proved to be highly sensitive and selective towards individual and simultaneous detection of DA and PA. Sensitive electrooxidation peak potential at 160 mV and 380 mV from the DPV technique was observed for DA and PA, respectively. Both DA and PA exhibit linear response over the range of 0.5 µM to 100 µM. The stability, reproducibility and repeatability of the Pt/CeO2@Cu2O were also inspected. The lower detection limits of 0.079 µM and 0.091 µM were recorded for DA and PA, respectively. The practical applicability of the Pt/CeO2@Cu2O-carbon paste electrode (CPE) is towards the simultaneous detection of DA and PA in drugs, as well as in spiked human serum and urine samples.

*Corresponding author: [email protected]. Phone: 080-22082998, Fax: 080-22082627

ACS Paragon Plus Environment

1

ACS Applied Nano Materials 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Introduction Dopamine is an important neurotransmitter in the central nervous system which is essential for signal transduction, behavioral responses and etc..1-3 Dopamine also acts as a chemical messenger in the peripheral nervous systems and plays a pivotal role in maintaining the proper functioning of cardiovascular, renal, and hormonal systems.4-5 Hence, abnormal levels of DA in the brain fluids eventually may lead to several neurological disorders, such as Parkinson’s disease.6 Therefore, regular monitoring the concentration of DA is essential. The catecholamine level can be determined through urine test investigation as DA metabolites tend to be excreted through urine.7 Paracetamol is one of the most widely used analgesic and antipyretic drug. It practically has non-steroidal anti-inflammatory properties8 and has been comprehensively used all over the world as a safe and effective chronic pain, releiver.9 Metabolization of PA is carried out by liver through the oxidative pathway. Inhibition of prostaglandin synthesis is specifically linked to the capability of PA in relieving pain. PA is known to curtail fever sedating the hypothalamic heatregulating center.10 It is also observed that, single dose of PA induces relieve from pain in a variety of pain diseases without any concomitant.11-12 Paracetamol is reported to be therapeutically potent in neurodegenerative diseases, particularly Alzheimer’s disease characterized by its effect as antioxidant. In-vitro studies reveals indicative of its ability to protect dopaminergic neurons against the oxidative stress damage caused by short-term exposure to higher levels of dopamine. Whereas in-vivo models on the long-term intake of paracetamol have been found to reduce the DA levels significantly. However, overdose of PA may affect the sympathetic nervous system resulting in fatal


2

Page 2 of 34

Page 3 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


hepatotoxicity and nephrotoxicity. Therefore, simultaneous analysis of DA and PA is of paramount interest to understand the clinical and pharmacological importance.13-16 Individually and simultaneously detection of DA and PA have already been reported by various techniques such as titrimetry,17 HPLC,18 spectrophotometry,19 chromatography20 and chemiluminescence.21 However, it is of paramount interest to develop an analytical technique that can determine accurate pharmaceutical dosage of DA and PA and their biocompatibility in biological fluids. Electrochemical techniques have been recently reported to be superior in terms of sensitivity, stability, repeatability and selectivity to detect DA and PA in biological fluids with relatively simple and low-cost instruments.16, 22-28 In case of utilizing electrochemical sensors, it is difficult to selectively detect DA and PA using unmodified electrode. Nanomaterials are known to increase the efficacy due to its morphology, surface property and crystallinity apart from the particle size.29 The development of modified electrodes for detection purposes is one of the modern feats of electro analytical chemistry. Overpotential arises from biological substrate poses difficulties, which can easily be tuned by chemically modified electrodes. These issues can be resolved by modifying the surface of the electrode using suitable materials. A wide variety of noble metal based nanomaterials have been used to fabricate and enhance the electrochemical sensing platform. Metal oxides,30 semiconductors,31 noble metal oxide32 are preferred in the aspects of cost reduction, stability and sensitivity. Especially graphene based materials play a vital role in biomolecule detection, due to its unique electronic configuration, electron transfer property and high specific surface area.33 Few literatures have already reported electrochemical deduction of biomolecules using graphene modified electrodes.24,

34-37

Despite all this, the manufacturability of graphene based electrodes remains


3


questionable.25 However Cuprous oxide (Cu2O) has excellent electrocatalytic activity towards the oxidation of biomolecules and it is highly preferred due to large surface area, and reversible redox activity.32 Cu2O nanoparticles of various shapes and sizes can be prepared by various methods which are used to modify electrodes to detect H2O2,38 glucose,39 DA and PA34, 40-41 at lower potentials. However, the use of Cu2O is limited by the issues related to its dispersion on the unmodified electrode. Cerium oxide (CeO2) based materials on the other hand, have been drawing continuous attention owing to their high surface oxygen mobility, chemical inertness, bio-compatibility, high surface area, non-toxicity and applicability over a wide range of areas.32, 42-47

In addition to this, CeO2 nanoparticles have also been observed as potent catalytic

antioxidants in various invitro studies. The biological characteristics of the CeO2 nanoparticles are a result of their variable oxidation state, allows the reversible of Ce4+ ↔ Ce3+ transition thus delivering inherent catalytic properties and act as a radical scavenger at the surface.32, 48 Hence CeO2 is highly capable in participating in redox reactions and its oxygen rich surface could very well facilitate the oxidation of Dopamine to Dopamine-o-quinone.48-49 Introducing platinum to nanocomposites has been of great significance due to the high electrocatalytic activity, outstanding conductivity, adsorption capabilities and biocompatibility in electrochemical sensors.50 Herein, we have developed Pt/CeO2@Cu2O nanocomposite for simultaneous detection of DA and PA. For the fabrication of electrochemical sensor, the similarity in size and surface area of noble metal nanoparticles with the biomolecules provides pathways for steady immobilization of biomolecules with their bioactivity remaining intact.51 In this present study, we have developed a novel Pt/CeO2@Cu2O nanocomposite modified with carbon paste electrode for the first time the to detect precise amount of DA and PA using electroanalytical method. Large surface area, good biocompatibility, excellent electron


4

Page 4 of 34

Page 5 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


conductivity and

of Pt/CeO2@Cu2O exhibit

superior electro-catalytic

the excellent

electrocatalytic activity, promising reproducibility and high stability towards the individual and simultaneous oxidation of DA and PA in 0.1 M PBS (pH 7.0). This excellent performance of the developed Pt/CeO2@Cu2O electrochemical sensor reveals its feasibility and performance for real sample analysis. Experimental methods Apparatus and Chemicals. Copper sulphate pentahydrate (CuSO4.5H2O, extrapure AR), sodium hydroxide (NaOH), trisodium citrate dihydrate (99%), sodium chloride (NaCl) and ascorbic acid (C6H8O6, 99.7%) were purchased from Finar chemicals. Cerium ammonium nitrate pentahydrate ((NH4)2Ce(NO3)6, 99%), potassium chloroplatinate (K2PtCl4) were purchased from Alfa Aesar. All the reagents were analytical grade and used for synthesis without further purification. Deionized water (Millipore, 18.2 MΩ.cm) was used throughout the synthesis and electrochemical measurements. Powder X-ray diffraction (PXRD) data were collected on a Rigaku Miniflex X-ray diffractometer using a Cu-Kα X-ray source (λ = 1.5406 Å). Transmission electron microscopy (TEM) images and selected area electron diffraction (SAED) patterns were obtained from Tecnai instrument. Scanning electron microscope (SEM) images are obtained using Quanta FEG250 field emission environmental SEM (FEI). All the electrochemical sensors-based measurements were carried out on CHI760E electrochemical workstation. Electrochemical cell contained three-electrodes such as-CPE Pt/CeO2@Cu2O modified CPE as the working electrode, Ag/AgCl electrode as the reference electrode and a Pt wire as auxiliary electrode. Samples of blood and urine from volunteers were


5


collected in accordance with an approved JNCASR ethical committee protocol approved by institutional ethics committee (IEC) for human research, JNCASR, Bangalore, India. Synthesis of Cu2O 50 nm nanocubes Uniform nanocubes of Cu2O were synthesized according to an established procedure.42 In the typical synthesis, 0.25 M of trisodium citrate was maintained at 20 °C and dispersed in 400 mL of deionized water for 20 min with vigorous stirring. The Cu2+ ions (1 M) were chelated by citrate ions (0.25 M) to form copper-citrate due to the addition of sodium citrate (0.25 M) (chelating agent). Followed these steps, 1.2 M (1 mL) CuSO4 solution was introduced using a pipette. After the duration of 5 min, 4.8 M (1 mL) sodium hydroxide solution was added into the solution. A clear blue solution immediately turned into turbid blue, indicating the precipitation of Cu(OH)2. After 5 min of this process, 1 mL (1.2 M) of reducing agent ascorbic acid was injected and the solution was maintained in a water bath for another 30 min. Visual confirmation indicated that the color of the solution rapidly turned from turbid blue to yellowish brown. The final product was collected after centrifugation process and then dried in vacuum chamber at ambient condition. Synthesis of Cu2O@CeO2 The CeO2@Cu2O nanocomposites were synthesized by Ramani et al.42 In the first step, 0.855 M NaCl aqueous solution was added to the synthesized Cu2O nanocubes, which is presented in ethanol solution. The suspension was dispersed for 30 min under ultrasonication. Then ceric ammonium nitrate ethanol solution (0.4 mM) was added dropwise to the above solution at 40 °C in an oil bath under vigorous stirring condition. The reaction was allowed to proceed for an additional 1 hr at the same condition. The solid product was collected after


6

Page 6 of 34

Page 7 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


centrifugation at 5000 rpm and then dried in vacuum chamber at ambient condition. To control CeO2 shell thickness, the concentration of ceric ammonium nitrate was maintained as 1mM. Synthesis of Pt/CeO2@Cu2O The synthesis of Pt/CeO2@Cu2O was performed under ultrasonic condition by dispersing Cu2O@CeO2 in 20 mL DI water. An amount of 20 wt% K2PtCl4 solution was added to this suspension. The reaction was initiated by adding 3-4 drops of glacial acetic acid under constant sonication. The solution immediately turned black, indicating the formation of platinum nanoparticles. The reaction was maintained for 1 h and the black precipitate was collected by centrifuging. The product obtained from the above reaction was etched with 1 M HCl for 2-3 h to partial eliminate the trace of Cu2O template. Electrode preparation Carbon paste electrode was fabricated by using graphite powder and paraffin oil with the help of a mortar and pestle. The carbon paste was inserted into glass tube. Contact was initiated by carefully introducing a piece of copper wire down the glass tube. Finally, the carbon paste electrode surface was obtained by removing the excess paste out of the tube and polishing with a weighing paper. Same procedure was followed for Cu2O, Cu2O@CeO2, Pt/CeO2@Cu2O modified carbon paste electrode with different ratio (15 mg catalyst and 85 mg graphite powder) of nanocomposites. Thus, the fabricated electrode was used for the determination of dopamine and paracetamol concentration individually and simultaneously. Prior to the electrochemical measurements, the modified electrode was gently washed with DA water and 0.1 M PBS solution. Results and discussion


7


Page 8 of 34

Crystallinity and Morphologies: The pXRD pattern of Cu2O nanocubes in Figure 1 represents shows the peaks at 2θ 29.5°, 36.4°, 42.3°, 52.4°, 61.3°, 73.5° and 77.3°, which are attributed to the corresponding lattice planes (110), (111), (200), (211), (220), (311) and (222) of Cu2O in the cubic structure (3) and confirming the formation of Cu2O pure phase. The peak positions of CeO2 in Cu2O@CeO2 are at 2θ 27.2°, 31.8°, 45.5°, 56.5° that can be indexed to the crystallographic planes (111), (200), (220), (311) respectively. The other predominant peaks at 2θ 36°, 43° and 62° correspond to Cu2O with crystal structure of CeO2 (Fm3m), and also shift in PXRD profile indicates the strain generated at the interface of Cu2O and CeO2 due the formation of Ce3+ ions and oxygen vacancies.52 The diffraction peaks for Pt/CeO2@Cu2O confirms that formation of Pt/CeO2 nanocomposite and partial elimination of Cu2O from this final composite. The presence of small peaks at 2θ, ~ 36° and ~ 43° are characteristics of Cu2O traces, which remain after the partial elimination from the Pt/CeO2 nanocomposites. There is noticeable broadening in the diffraction peaks that clearly indicating a small particle size of Pt/CeO2@Cu2O nanocomposites. SEM images show that the as-obtained Cu2O nonocubes are 50 nm (Figure S1a) with uniform size distribution. This is further supported by TEM analysis (Figure 2a-b). The size of Cu2O

cubes

can

be

varied

with

respect

to

the

ratio

of

(CuSO4:C6H5Na3O7.2H2O:NaOH:C6H8O6).53 In the presence of NaOH, Cu2+ ions forms as copper hydroxide very rapidly. Then the copper hydroxide turns into Cu2O with the help of ascorbic acid (reducing agent). But for the different size of Cu2O nanocubes, need to introduce sodium citrate (chelating agent), which initially forms as copper-citrate complex to prevent the precipitation of copper hydroxide upon the addition of NaOH. Chelating agent strongly affects


8

Page 9 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


the nucleation growth of Cu2O nanocubes. The mechanism of the formation of Cu2O nanocubes is given as eqns (1) and (2).53 + → ( )

(1)

( ) + → + +

(2)

XPS analysis in our previous work demonstrated that the surface of Cu2O nanocubes, the formation of Ce(iv) oxide and the two bands of Pt(0); 4f7/2 and 4f5/2.42 The SEM images exhibit Cu2O@CeO2 core-shell nanostructure (Figure S1b) and well duplicates the cubic morphology of Cu2O cubes, which was later confirmed by TEM images (Figure 2c-d) and elemental color mapping (Figure 3a). The formation of ultra-thin homogeneous layer of CeO2 was also observed on the surface of Cu2O, which is due to presence of the low concentration of Ce. In the case of high concentration of Ce, deformation for core shell was observed.42,54 The incorporation of Pt and removal of partial Cu2O nanocubes led to the formation of uniform nanoboxes of Pt/CeO2@Cu2O composite (Figure 2e-f). TEM image of Pt/CeO2@Cu2O nanocomposites (Figure 2f) confirms that controlled nanobox morphology and also color mapping process highlights distribution of nanocomposites (Figure 3b). Electrochemical Behavior of Dopamine and Paracetamol Electrochemical Impedance Spectroscopy (EIS) was obtained to investigate the electronic charge transfer resistance of different nanocomposites modified with CPE. Figure 4, shows the EIS of bare CPE, Cu2O, Cu2O@CeO2 and Pt/CeO2@Cu2O in 5 mM of [Fe(CN)6]3-/4- containing 0.1 M KCl solution. The measurements were carried out in the frequency range from 0.1 Hz to 100 kHz. From Randle equivalent circuit model,55 the parameters such as, electron transfer resistance (Rct), solution-phase resistance (Rs), double layer capacitance (Cdl) and Warburg impedance (Zw) between electrode/electrolyte interfaces. The lower frequency region


9


(semicircular) corresponds to electron transfer resistance and the higher frequency region (linear part) corresponds to electrolyte diffusion process. The Rct value of the CPE, Cu2O, Cu2O@CeO2 and Pt/CeO2@Cu2O electrodes were 37.0 Ω, 44.9 Ω, 218.9 Ω, 312.8 Ω respectively. The rapid electron transfer showcases the superiority of Pt/CeO2@Cu2O modified electrode compared to other electrodes. The cyclic voltammogram of the four different modified electrodes such as (a) carbon paste electrode (CPE), (b) Cu2O-CPE, (c) Cu2O@CeO2-CPE and (d) Pt/CeO2@Cu2O-CPE were investigated in the presence of 50 µM dopamine and 100 µM paracetamol in 0.1 M Phosphate buffer solution (PBS) (pH 7.0) at a scan rate of 50 mVs-1 are shown in Figure 5(a-b). The oxidation peak current (I) and peak potential (E) of dopamine and paracetamol as follows: (a) IDA:3.5 µA, EDA: 0.250 V; IPA: 3.5 µA, EPA: 0.488 V; (b) IDA:5.3 µA, EDA: 0.278 V; IPA: 6.7 µA, EPA: 0.481 V; (c) IDA:7.3 µA, EDA: 0.220 V; IPA: 9.2 µA, EPA: 0.462 V; (d) IDA:9.4 µA, EDA: 0.229 V; IPA: 10.5 µA, EPA: 0.467 V respectively. In bare CPE, the oxidation peak current of DA and PA were obtained at low current and Cu2O-CPE shows high oxidation potential with less peak current than other types of listed CeO2 modified electrodes. This is because Cu2O exhibits higher resistance compared to pure CeO2.56 The high resistance hinders the electrons diffusion from the surface of the electrode to the analyte during the oxidation. The Cu2O/CeO2 and Pt/CeO2@Cu2O nanocomposite significantly promotes dopamine and paracetamol oxidation. At the applied potential, electrons can be elated from dopamine and paracetamol to the electrode surface. Because CeO2 possesses high oxygen mobility on its surface, it can facilitate the oxidation of dopamine to dopamine-o-quinone (D-o-Q) and paracetamol into N-Acetyl-Pbenzoquinone imine (NAPQI) while reducing Ce4+ ↔ Ce3+ at the electrode surface.48 On the introduction of Pt, the composite becomes rather stable in terms of maintaining its size and shape


10

Page 10 of 34

Page 11 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


owing to the mutual inhibition between Pt and CeO2.43 The formation of Pt on CeO2 surface with a considerable number of oxygen vacancies and the flow of charge occurs from CeO2, giving rise to the formation of redox couple (Ce4+ ↔ Ce3+) on the intermediate layer of Pt/CeO2 interface. These in situ redox couple not only increase the catalytic activity, but also enhance the electronic conductivity of CeO2.42,57 The Pt/CeO2@Cu2O nanocomposite exhibits enhancement in peak current of dopamine and paracetamol oxidation due to its in situ redox couple and high electronic conductivity. The superior performance of Pt/CeO2@Cu2O-CPE as electrochemical sensor as well as electron promoter is showcased by the electrochemical oxidation of DA and PA. The overall fabrication of Pt/CeO2@Cu2O and electrochemical oxidation process towards the detection of DA and PA is shown as scheme 1. The oxidation of dopamine is directly electrooxidized into dopamine-o-quinone (D-o-Q) and paracetamol oxidized into N-Acetyl-Pbenzoquinone imine (NAPQI). The electrochemical behavior of DA redox couple has been projected via the electron transfer-chemical reaction-electron transfer (ECE) mechanism.58-59 Figure 5a shows well-defined redox couple of dopamine detection using the Pt/CeO2@Cu2O electrode. The oxidation peak current (Ipa) of DA to D-o-Q and reduction peak current (Ipc) of D-o-Q to DA is not equal (Ipa/Ipc ≈ 1, for reversible couple). The electrochemical oxidation reaction of PA is expected via ECE mechanism.60-61 Similar behavior was obtained in Figure 5b

for PA, the Ipc is too smaller than Ipa (PA NAPB & NAPB PA), which indicates that electrochemical DA and PA reactions are quasi-reversible at electrode surface. The electroanalytical techniques found for the simultaneous determination of DA and PA using PtCeO2@Cu2O-CPE and other reported materials are presented in Table 1.4,23-26, 28, 47 It is clear that the proposed materials provided excellent detection of both analytes (DA and PA) at very low concentration levels.


11


Effect of pH The pH of the electrolyte has a vital role in electrochemical detection, because it changes the redox potential and peak current of analytes. For developing electrochemical sensor, the material designing should be based on the redox potential. Figure S2 shows the influence of the pH effect of the solution on the electrocatalytic oxidation potential/current of dopamine (50 µM) and paracetamol (100 µM) at Pt/CeO2@Cu2O-CPE in 0.1 M PBS solution by DPV in the pH range from 5 to 9 and the data at pH 7.0 exhibited suitable oxidation potential and peak current for dopamine and paracetamol. Therefore pH 7.0 was considered for further experiments. Effects of Scan Rate The effects of scan rates on the electrochemical oxidation behaviour of DA and PA were investigated in 0.1 M PBS (pH 7.0). Figure 6(a&b), shows the cyclic voltammetric profiles of 100 µM DA and 100 µM PA at different scan rates from 10 mVs-1 to 300 mVs-1 respectively. The redox peak current of DA is linearly dependent with the square root of scan rate. Also the peak potential of redox couple was found to shift towards the higher/lower potentials respectively. The analysis of peak current versus the square root of scan rate was found to exhibit good linearity. On fitting it using linear regression, we obtained the following equations and results: (for DA; Ipa (µA) = 1.2502υ – 0.5745, R2 = 0.9922, for PA; Ipa (µA) = 0.1624υ – 0.2563, R2 = 0.9958). These observations show that the oxidation reaction of DA and PA was diffusion controlled electron transfer at Pt/CeO2@Cu2O electrode.62-63 The apparent diffusion coefficient (D) could be attributed to the difference in the electroactive surface area from the modified electrode systems. Using Randles-Sevick equation27 (eqn 3), the diffusion coefficient values can be calculated for different modified electrodes.64-65 The D values for dopamine were 3.46 × 10−5 cm2 s−1 at the CPE, 7.94 × 10−5 cm2 s−1 at the


12

Page 12 of 34

Page 13 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Cu2O-CPE, 1.50 × 10−4 cm2 s−1 at the Cu2O@CeO2-CPE and 2.49 × 10−4 cm2 s−1 at the Pt/CeO2@Cu2O-CPE, respectively. And also, the D values for paracetamol were 0.91 × 10−5 cm2 s−1 at the CPE, 3.17 × 10−5 cm2 s−1 at the Cu2O-CPE, 5.98 × 10−5 cm2 s−1 at the Cu2O@CeO2CPE and 7.79 × 10−5 cm2 s−1 at the Pt/CeO2@Cu2O-CPE, respectively. = (. × "#$ )%/ '("/ υ υ"/

(3)

where, Ipa is the peak current, n is the number of electron transfer, n = 2 for oxidation of DA and PA respectively, D is the diffusion co-efficient and C is the surface concentration, A is the electrode surface area, and υ is the scan rate. Analysis of Dopamine and Paracetamol The electrochemical performance of the Pt/CeO2@Cu2O-CPE modified electrode was examined under the optimized conditions. Prior to the sensing of DA and PA, cyclic voltammetry at the modified Pt/CeO2@Cu2O-CPE was recorded using 0.1 M PBS (pH 7.0) clearly indicated the absence of any peak characteristic of DA and PA. Thereafter, the DPV at different concentrations of DA was performed on Pt/CeO2@Cu2O-CPE modified electrode. An increase in the peak current was observed when concentration of DA was changed from 0.5 µM to 160 µM (Figure 7a). The calibration plot (insert Figure 7a) confirms that DA concentration is linearly dependent to the oxidation peak current over the range of 0.5 µM to 160 µM with the linear regression equation of I (µA) = 0.044c + 0.5081 (DA µM), (R2 = 0.9982). The limit of detection for DA was found to be 0.081 µM. Similarly, DPV on Pt/CeO2@Cu2O-CPE electrode for different concentration of PA also recorded. In this case also, the PA peak current is increased with concentration of PA from 0.5 µM to 160 µM (Figure 7b). The calibration plot (inset figure 7b) displays a linear increase of PA concentration with oxidation peak current over


13


the range from 0.5 µM to 160 µM with the linear regression equation of I (µA) = 0.0318c + 0.5594 (PA µM), (R2 = 0.997). The limit of detection for PA was found to be 0.093 µM. For the simultaneous detection of DA and PA, the oxidation peak current for both the compounds increased linearly (Figure 8). The calibration plot (inset figure 8) shows that both DA and PA concentrations have a linear association to the oxidation peak current in the range 0.5 µM to 100 µM with the linear regression equation of I (µA) = 0.049c + 0.3667 (DA µM), R2 = 0.9971 and I (µA) = 0.0564c + 0.577 (PA µM), R2 = 0.9980, respectively. The limit of detection (LOD) and limit of quantification (LOQ) for DA was found to be 0.079 µM, 0.26 µM respectively. Similarly, the LOD and LOQ for PA was found to be 0.091 µM and 0.30 µM, respectively. The LOD and LOQ were calculated from the equation (4) and (5). ) ( = *⁄+

(4)

) - = "#*⁄+

(5)

where, m is the slope of the calibration plot and σ is the standard deviation of blank solution (0.1 M PBS). These results clearly conclude that Pt/CeO2@Cu2O-CPE has the capability to detect these compounds (DA and PA) individually and simultaneously over a wide linear range and even at low concentrations. Stability, Reproducibility and Interference Studies of Pt/CeO2@Cu2O-CPE The Pt/CeO2@Cu2O-CPE modified electrode was performed towards stability over a period of three weeks. DPV was carried out on Pt/CeO2@Cu2O-CPE to detect DA and PA in the presence of 0.1 M PBS at a regular interval of three days by determining the current response. It is observed (Figure S3a) that the current responses of DA and PA decreased by about 5 and 7% respectively. The modified electrode was stored in 0.1 M PBS solution during the measurements. The reproducibility of Pt/CeO2@Cu2O was also investigated with five different electrodes in the


14

Page 14 of 34

Page 15 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


presence of 50 µM of DA and 50 µM of PA (Figure S3b). The current obtained from the five independent modified electrodes for DA and PA showed a RSD of 0.83% and 1.39%, respectively. Thus, the proposed materials are observed to have excellent reproducibility and good stability. The major challenge in the detection of DA and PA are the co-existing compounds in biological fluids, which could be solved by electrochemical detection. Chronoamperometric was investigated for interfering compounds such as ascorbic acid (AA), uric acid (UA), caffeic acid (CA) and serotonin (SE). Figure S4a, shows the chronoamperometric response of Pt/CeO2@Cu2O to the experiments conducted with 10-fold higher adding of above compounds subsequently at 50s intervals along with DA at 0.16 V. We can clearly see a peak on addition of DA while such distinctive peaks are absent in other compounds. A similar behavior was observed with PA at 0.36 V (Figure S4b). DPV was investigated for 50 µM of DA, 50 µM of PA, 100 of µM AA and 100 of µM (Figure S5), the obtained peak of DA, PA, AA and UA were well separated. The DA and PA were not interfered with AA and PA even at higher concentration. The results reveal that no serious interference occurred from the most common co-exist interferences species. Real sample analysis For Pt/CeO2@Cu2O-CPE sensor to be practically feasible the simultaneous determination of DA and PA in real samples is highly mandatory. Originally drugs containing dopamine (dopamine injection) and paracetamol (paracetamol tablet 500 mg) were purchased from market. The tablets were weighed and powered. And then, DA solution and PA powder were dissolved in 0.1 M PBS. The solution containing DA and PA was diluted to the working range and then DPV was carried out using Pt/CeO2@Cu2O modified electrode. The concentration of DA and PA


15


were determined from the calibration curve. Table 2 shows the analysis of drugs contain DA and PA in 0.1 M PBS of pH 7.0. The recovery results of commercial drugs for the proposed method are in the range from 97.07 to 104.085 %, the intra assay and inter assay precision of DA and PA are obtained in Table S1 with the coefficient of variation were found in the range of 0.89 % to 3.44 %, revealing that the Pt/CeO2@Cu2O modified electrode is reliable for practical application. CONCLUSION In conclusion, we report a Pt/CeO2@Cu2O nanocomposites synthesized from sacrificial Cu2O nanocubes by low temperature galvanic replacement method and involving phase interfacial reaction. Pt/CeO2@Cu2O nanocomposites was prepared with well-controlled, environment-friendly low-cost method and without any organic additives. The interfacial involvement between Cu2O and CeO2 leads to the strong core-shell formation. Further incorporation of Pt and partial removal of Cu2O form Cu2O@CeO2 core-shell provide stable and controlled Pt/CeO2@Cu2O nonoboxes that exhibited high electrocatalytic activity towards individual and simultaneous electrooxidation of dopamine and paracetamol by electroanalytical method. With these features, Pt/CeO2@Cu2O nanocomposites provides a new strategy for the electrochemical determination of DA and PA in real sample analysis with good recovery results. Acknowledgment: We thank the Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Department of Science and Technology and Technical Research Centre in JNCASR (TRC) for financial support. A R R is grateful to JNCASR and TRC for the research fellowship. Supporting Information. The supporting information is available free of charge via the Internet at http://pubs.acs.org.


16

Page 16 of 34

Page 17 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


References 1.

Wightman, R. M.; May, L. J.; Michael, A. C., Detection of Dopamine Dynamics in the Brain. Anal. Chem. 1988, 60, 769A-779A.

2.

Kurian, M. A.; Gissen, P.; Smith, M.; Heales, S. J. R.; Clayton, P. T., The Monoamine Neurotransmitter Disorders: An Expanding Range of Neurological Syndromes. Lancet Neurol 2011, 10, 721-733.

3.

Pandikumar, A.; Soon How, G. T.; See, T. P.; Omar, F. S.; Jayabal, S.; Kamali, K. Z.; Yusoff, N.; Jamil, A.; Ramaraj, R.; John, S. A.; Lim, H. N.; Huang, N. M., Graphene and Its Nanocomposite Material Based Electrochemical Sensor Platform for Dopamine. RSC Adv 2014, 4, 63296-63323.

4.

Kokulnathan, T.; Joseph Anthuvan, A.; Chen, S.-M.; Chinnuswamy, V.; Kadirvelu, K., Trace Level Electrochemical Determination of the Neurotransmitter Dopamine in Biological Samples Based on Iron Oxide Nanoparticle Decorated Graphene Sheets. Inorg. Chem. Front. 2018, 5, 705-718.

5.

Sajid, M.; Nazal, M. K.; Mansha, M.; Alsharaa, A.; Jillani, S. M. S.; Basheer, C., Chemically Modified Electrodes for Electrochemical Detection of Dopamine in the Presence of Uric Acid and Ascorbic Acid: A Review. TrAC Trends Anal. Chem. 2016, 76, 15-29.

6.

Goyal, R. N.; Singh, S. P., Simultaneous Voltammetric Determination of Dopamine and Adenosine Using a Single Walled Carbon Nanotube – Modified Glassy Carbon Electrode. Carbon 2008, 46, 1556-1562.

7.

Sieber-Ruckstuhl, N.; Salesov, E.; Quante, S.; Riond, B.; Rentsch, K.; HofmannLehmann, R.; Reusch, C.; Boretti, F., Effects of Trilostane on Urinary Catecholamines and their Metabolites in Dogs with Hypercortisolism. BMC Vet. Res. 2017, 13, 279-285.

8.

Ying Li, S.-M. C., The Electrochemical Properties of Acetaminophen on Bare Glassy Carbon Electrode. Int. J. Electroche. Sci. 2012, 7, 2175-2188.

9.

Mahmoud, B. G.; Khairy, M.; Rashwan, F. A.; Banks, C. E., Simultaneous Voltammetric Determination of Acetaminophen and Isoniazid (Hepatotoxicity-Related Drugs) Utilizing Bismuth Oxide Nanorod Modified Screen-Printed Electrochemical Sensing Platforms. Anal. Chem. 2017, 89, 2170-2178.


17


10. Andersson, D. A.; Gentry, C.; Alenmyr, L.; Killander, D.; Lewis, S. E.; Andersson, A.; Bucher, B.; Galzi, J.-L.; Sterner, O.; Bevan, S.; Högestätt, E. D.; Zygmunt, P. M., TRPA1 Mediates Spinal Antinociception Induced by Acetaminophen and the Cannabinoid ∆9Tetrahydrocannabiorcol. Nat. Comm. 2011, 2, 551. 11. Helene Faber, M. V., Uwe Karst, Electrochemistry/Mass Spectrometry as a Tool in Metabolism Studies - a Review. Anal. Chim. Acta 2014, 834, 9-21. 12. Zhou, F.; Van Berkel, G. J., Electrochemistry Combined Online with Electrospray Mass Spectrometry. Anal. Chem. 1995, 67, 3643-3649. 13. Song, J.; Yang, J.; Zeng, J.; Tan, J.; Zhang, L., Graphite Oxide Film-Modified Electrode as an Electrochemical Sensor for Acetaminophen. Sens. Actuators B: Chem. 2011, 155, 220-225. 14. Locke, C. J.; Fox, S. A.; Caldwell, G. A.; Caldwell, K. A., Acetaminophen Attenuates Dopamine Neuron Degeneration in Animal Models of Parkinson's Disease. Neurosci. Lett. 2008, 439, 129-133. 15. Courade J. P, C. F., Martin K, Besse D, Delchambre C, Hanoun N, Hamon M, Eschalier A, Cloarec A., Effects of Acetaminophen on Monoaminergic Systems in the Rat Central Nervous System. N. S. Arch Pharmacol. 2001, 364, 534-537. 16. Chandra, P.; Son, N. X.; Noh, H.-B.; Goyal, R. N.; Shim, Y.-B., Investigation on the Downregulation of Dopamine by Acetaminophen Administration Based on Their Simultaneous Determination in Urine. Biosens. Bioelectron. 2013, 39, 139-144. 17. Kumar, K. G.; Letha, R., Determination of Paracetamol in Pure Form and in Dosage Forms Using N,N-Dibromo Dimethylhydantoin. J. Pharm. Biomed. Anal. 1997, 15, 1725-1728. 18. Yoshitake, T.; Kehr, J.; Yoshitake, S.; Fujino, K.; Nohta, H.; Yamaguchi, M., Determination of Serotonin, Noradrenaline, Dopamine and Their Metabolites in Rat Brain Extracts and Microdialysis Samples by Column Liquid Chromatography with Fluorescence Detection Following Derivatization with Benzylamine and 1,2Diphenylethylenediamine. J. Chromatogr. B 2004, 807, 177-183. 19. Németh, T.; Jankovics, P.; Németh-Palotás, J.; Kőszegi-Szalai, H., Determination of Paracetamol and Its Main Impurity 4-Aminophenol in Analgesic Preparations by Micellar Electrokinetic Chromatography. J. Pharm. Biomed.Anal. 2008, 47, 746-749.


18

Page 18 of 34

Page 19 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


20. Ing-Lorenzini, K. R.; Desmeules, J. A.; Besson, M.; Veuthey, J.-L.; Dayer, P.; Daali, Y., Two-Dimensional Liquid Chromatography–Ion Trap Mass Spectrometry for the Simultaneous Determination of Ketorolac Enantiomers and Paracetamol in Human Plasma: Application to a Pharmacokinetic Study. J. Chromatogr. A 2009, 1216, 38513856. 21. Zhang, L.; Teshima, N.; Hasebe, T.; Kurihara, M.; Kawashima, T., Flow-Injection Determination of Trace Amounts of Dopamine by Chemiluminescence Detection. Talanta 1999, 50, 677-683. 22. Kemmegne-Mbouguen, J. C.; Ngameni, E., Simultaneous Quantification of Dopamine, Acetaminophen and Tyrosine at Carbon Paste Electrodes Modified with Porphyrin and Clay. Anal. Methods 2017, 9, 4157-4166. 23. Babaei, A.; Yousefi, A.; Afrasiabi, M.; Shabanian, M., A Sensitive Simultaneous Determination of Dopamine, Acetaminophen and Indomethacin on a Glassy Carbon Electrode Coated with a New Composite of Mcm-41 Molecular Sieve/Nickel Hydroxide Nanoparticles/Multiwalled Carbon Nanotubes. J. Electroanal. Chem. 2015, 740, 28-36. 24. Cheemalapati, S.; Palanisamy, S.; Mani, V.; Chen, S. M., Simultaneous Electrochemical Determination

of

Dopamine

and

Paracetamol

on

Multiwalled

Carbon

Nanotubes/Graphene Oxide Nanocomposite-Modified Glassy Carbon Electrode. Talanta 2013, 117, 297-304. 25. Keeley, G. P.; McEvoy, N.; Nolan, H.; Kumar, S.; Rezvani, E.; Holzinger, M.; Cosnier, S.; Duesberg, G. S., Simultaneous Electrochemical Determination of Dopamine and Paracetamol Based on Thin Pyrolytic Carbon Films. Anal. Methods 2012, 4, 2048-2053. 26. Gholivand, M. B.; Amiri, M., Simultaneous Detection of Dopamine and Acetaminophen by Modified Gold Electrode with Polypyrrole/Aszophloxine Film. Journal of Electroanal. Chem. 2012, 676, 53-59. 27. Atta, N. F.; Galal, A.; Abu-Attia, F. M.; Azab, S. M., Simultaneous Determination of Paracetamol and Neurotransmitters in Biological Fluids Using a Carbon Paste Sensor Modified with Gold Nanoparticles. J. Mater. Chem. 2011, 21, 13015-13024. 28. Alothman, Z. A.; Bukhari, N.; Wabaidur, S. M.; Haider, S., Simultaneous Electrochemical Determination of Dopamine and Acetaminophen Using Multiwall


19


Page 20 of 34

Carbon Nanotubes Modified Glassy Carbon Electrode. Sens. Actuators B: Chem. 2010, 146, 314-320. 29. Wang, T.; Zhou, S.; Zhang, C.; Lian, J.; Liang, Y.; Yuan, W., Facile Synthesis of Hematite Nanoparticles and Nanocubes and Their Shape-Dependent Optical Properties. New J. Chem. 2014, 38, 46-49. 30. Ansari, A. A.; Kaushik, A.; Solanki, P. R.; Malhotra, B. D., Sol–Gel Derived Nanoporous Cerium Oxide Film for Application to Cholesterol Biosensor. Electrochem. Comm. 2008, 10, 1246-1249. 31. Yang, M.; Li, H.; Javadi, A.; Gong, S., Multifunctional Mesoporous Silica Nanoparticles as Labels for the Preparation of Ultrasensitive Electrochemical Immunosensors. Biomaterials 2010, 31, 3281-3286. 32. Li F, L. Y., Feng J, Dong Y, Wang P, Chen L, Chen Z, Liu H, Wei Q, Ultrasensitive Amperometric

Immunosensor for PSA Detection

Nanocomposites as

Based

on

Cu2O@CeO2-Au

Integrated Triple Signal Amplification Strategy. Biosens.

Bioelectron. 2017, 87, 630-637. 33. Bollella, P.; Fusco, G.; Tortolini, C.; Sanzò, G.; Favero, G.; Gorton, L.; Antiochia, R., Beyond Graphene: Electrochemical Sensors and Biosensors for Biomarkers Detection. Biosens. Bioelectron. 2017, 89, 152-166. 34. He, Q.; Liu, J.; Liu, X.; Li, G.; Deng, P.; Liang, J., Preparation of Cu2O-Reduced Graphene Nanocomposite Modified Electrodes Towards Ultrasensitive Dopamine Detection. Sensors 2018, 18, 199-211. 35. Rajamani, A. R.; Kannan, R.; Krishnan, S.; Ramakrishnan, S.; Mohanraj, S.; Kumaresan, D.; Kothurkar, N.; Rangarajan, M., Electrochemical Sensing of Dopamine, Uric Acid and Ascorbic Acid Using tRGo-TiO2 Nanocomposites. J. nanosci. nanotechnol. 2015, 15, 5042-5047. 36. Quanguo He, J. L., Xiaopeng Liu, Guangli Li , Dongchu Chen , Peihong Deng, Jing Liang, Fabrication of Amine-Modified Magnetite-Electrochemically Reduced Graphene Oxide Nanocomposite Modified Glassy Carbon Electrode for Sensitive Dopamine Determination. Nanomater. 2018, 8, 194-208. 37. Tezerjani, M. D.; Benvidi, A.; Dehghani Firouzabadi, A.; Mazloum-Ardakani, M.; Akbari, A., Epinephrine Electrochemical Sensor Based on a Carbon Paste Electrode


20

Page 21 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Modified

with

Simultaneous

Hydroquinone Determination

Derivative of

and

Epinephrine,

Graphene

Oxide

Acetaminophen

Nano-Sheets:

and

Dopamine.

Measurement 2017, 101, 183-189. 38. Chirizzi, D.; Guascito, M. R.; Filippo, E.; Malitesta, C.; Tepore, A., A Novel Nonenzymatic Amperometric Hydrogen Peroxide Sensor Based on CuO@Cu2O Nanowires Embedded into Poly(Vinyl Alcohol). Talanta 2016, 147, 124-131. 39. Ji, Y.; Liu, J.; Liu, X.; Yuen, M. M. F.; Fu, X.-Z.; Yang, Y.; Sun, R.; Wong, C.-P., 3d Porous Cu@Cu2O Films Supported Pd Nanoparticles for Glucose Electrocatalytic Oxidation. Electrochim. Acta 2017, 248, 299-306. 40. Aparna, T. K.; Sivasubramanian, R.; Dar, M. A., One-Pot Synthesis of Au-Cu2O/RGo Nanocomposite Based Electrochemical Sensor for Selective and Simultaneous Detection of Dopamine and Uric Acid. J.Alloys Compd 2018, 741, 1130-1141. 41. Devaraj, M.; Saravanan, R.; Deivasigamani, R.; Gupta, V. K.; Gracia, F.; Jayadevan, S., Fabrication of Novel Shape Cu and Cu/Cu2O Nanoparticles Modified Electrode for the Determination of Dopamine and Paracetamol. J. Mol. Liq. 2016, 221, 930-941. 42. Ramani, S.; Sarkar, S.; Vemuri, V.; Peter, S. C., Chemically Designed CeO2 Nanoboxes Boost the Catalytic Activity of Pt Nanoparticles toward Electro-Oxidation of Formic Acid. J. Mater, Chem. A 2017, 5, 11572-11576. 43. Wang, X.; Liu, D.; Song, S.; Zhang, H., Pt@CeO2 Multicore@Shell Self-Assembled Nanospheres: Clean Synthesis, Structure Optimization, and Catalytic Applications. J. Am. Chem. Soc 2013, 135, 15864-15872. 44. Lijuan Wang, X. W., Zhaohui Meng, Hongjiang Hou, Baokuan Chen, Mof-Templated Thermolysis for Porous Cuo/Cu2O@CeO2 Anode Material of Lithium-Ion Batteries with High Rate Performance. J. Mater. Sci. 2017, 52, 7140-7148. 45. Patil, D.; Dung, N. Q.; Jung, H.; Ahn, S. Y.; Jang, D. M.; Kim, D., Enzymatic Glucose Biosensor Based on CeO2 Nanorods Synthesized by Non-Isothermal Precipitation. Biosens. Bioelectron. 2012, 31, 176-181. 46. Gougis, M.; Tabet-Aoul, A.; Ma, D.; Mohamedi, M., Nanostructured Cerium Oxide Catalyst Support: Effects of Morphology on the Electroactivity of Gold toward Oxidative Sensing of Glucose. Microchim. Acta 2014, 181, 1207-1214.


21


47. Sivakumar, M.; Sakthivel, M.; Chen, S.-M., One Pot Synthesis of CeO2 Nanoparticles on a Carbon Surface for the Practical Determination of Paracetamol Content in Real Samples. RSC Adv. 2016, 6, 104227-104234. 48. Hayat, A.; Andreescu, D.; Bulbul, G.; Andreescu, S., Redox Reactivity of Cerium Oxide Nanoparticles against Dopamine. J. Colloid Interface Sci. 2014, 418, 240-245. 49. Peng, Y.; Chen, X.; Yi, G.; Gao, Z., Mechanism of the Oxidation of Organic Dyes in the Presence of Nanoceria. Chem. Comm. 2011, 47, 2916-2918. 50. Anuar, N. S.; Basirun, W. J.; Ladan, M.; Shalauddin, M.; Mehmood, M. S., Fabrication of Platinum Nitrogen-Doped Graphene Nanocomposite Modified Electrode for the Electrochemical Detection of Acetaminophen. Sens. Actuators B: Chem. 2018, 266, 375383. 51. Wang, J., Electrochemical Biosensing Based on Noble Metal Nanoparticles. Microchim. Acta 2012, 177, 245-270. 52. Chen, S.; Li, L.; Hu, W.; Huang, X.; Li, Q.; Xu, Y.; Zuo, Y.; Li, G., Anchoring HighConcentration Oxygen Vacancies at Interfaces of CeO2–X/Cu toward Enhanced Activity for Preferential CO Oxidation. ACS Appl Mater. Interfaces 2015, 7, 22999-23007. 53. Chang, I. C.; Chen, P.-C.; Tsai, M.-C.; Chen, T.-T.; Yang, M.-H.; Chiu, H.-T.; Lee, C.Y., Large-Scale Synthesis of Uniform Cu2O Nanocubes with Tunable Sizes by in-Situ Nucleation. CrystEngComm 2013, 15, 2363-2366. 54. Bao, H.; Zhang, Z.; Hua, Q.; Huang, W., Compositions, Structures, and Catalytic Activities of CeO2@Cu2O Nanocomposites Prepared by the Template-Assisted Method. Langmuir 2014, 30, 6427-6436. 55. Suni, I. I., Impedance Methods for Electrochemical Sensors Using Nanomaterials. TrAC Trends in Analytical Chemistry 2008, 27, 604-611. 56. Guan, P.; Li, Y.; Zhang, J.; Li, W., Non-Enzymatic Glucose Biosensor Based on CuoDecorated CeO2 Nanoparticles. Nanomaterials 2016, 6, 159-166. 57. Tereshchuk, P.; Freire, R. L. H.; Ungureanu, C. G.; Seminovski, Y.; Kiejna, A.; Da Silva, J. L. F., The Role of Charge Transfer in the Oxidation State Change of Ce Atoms in the Tm13-CeO2(111) Systems (Tm = Pd, Ag, Pt, Au): A Dft + U Investigation. Phys. Chem. Chem. Phys 2015, 17, 13520-13530.


22

Page 22 of 34

Page 23 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


58. Zhao, J.; Zhang, W.; Sherrell, P.; Razal, J. M.; Huang, X.-F.; Minett, A. I.; Chen, J., Carbon Nanotube Nanoweb–Bioelectrode for Highly Selective Dopamine Sensing. ACS Appl. Mater. Interfaces 2012, 4, 44-48. 59. Mercante, L. A.; Pavinatto, A.; Iwaki, L. E. O.; Scagion, V. P.; Zucolotto, V.; Oliveira, O. N.; Mattoso, L. H. C.; Correa, D. S., Electrospun Polyamide 6/Poly(Allylamine Hydrochloride) Nanofibers Functionalized with Carbon Nanotubes for Electrochemical Detection of Dopamine. ACS Appl. Mater. Interfaces 2015, 7, 4784-4790. 60. Filik, H.; Cetintas G.; Avan Ashhan A.; Koc, S. N.; ,Boz, Đ., Electrochemical Sensing of Acetaminophen on Electrochemically Reduced Graphene Oxide-Nafion Composite Film Modified Electrode. Int. J. Electrochem. Sci. 2013, 8, 5724-5737. 61. David J. Miner, J. R. R., Ralph M. Riggin, Peter T. Kissinger, Voltammetry of Acetaminophen and Its Metabolites. Anal. Chem. 1981, 53, 6. 62. Kannan, A.; Sevvel, R., A Highly Selective and Simultaneous Determination of Paracetamol and Dopamine Using Poly-4-Amino-6-Hydroxy-2-Mercaptopyrimidine (Poly-Ahmp) Film Modified Glassy Carbon Electrode. J. Electroanal. Chem. 2017, 791, 8-16. 63. Ghanbari, K. H.; Bonyadi, S., An Electrochemical Sensor Based on Reduced Graphene Oxide Decorated with Polypyrrole Nanofibers and Zinc Oxide-Coper Oxide

p-n

Voltammetric Determination of Ascorbic Acid, Dopamine, Paracetamol, and Tryptophan. New J. Chem. 2018, 42, 8512-8523. 64. Karikalan, N.; Karthik, R.; Chen, S. M.; Velmurugan, M.; Karuppiah, Chelladurai., Electrochemical Properties of the Acetaminophene on the Screen Printed Carbon Electrode Towards the High Performance Practical Sensor Applications. J. Colloid Interface Sci. 2016, 483, 109-117. 65. Narayana, P. V.; Reddy, T. M.; Gopal, P.; Naidu, G. R., Electrochemical Sensing of Paraetamol and its Samultaneous Resolution in the Presence of Dopamine and Folic Acid at a Multi-walled Carbon Nanotubes/Poly(glycine) Composite Modified Electrode. Anal. Methods. 2014, 6, 9459-9468


23


Page 24 of 34

Tables Table 1. Comparison of the proposed Pt/CeO2@Cu2O-CPE with reported electrochemical detection of DA and PA. Modified electrode

Target analyte

Linear (µ µM)

MWCNTsNHNPs-MCM41/GCE

Dopamine, 1.0-45 and 70-350 acetaminophen and 0.2-20 and 20-220 indomethacin 0.8-40 and 60-160

0.15

CeO2

Paracetamol

1-1200

0.07

49

Ppyox/Az/Au

Dopamine

0.1-30

0.05

26

Paracetamol

0.2-100

0.08

0.2-400

0.022

Paracetamol

0.5 to 400

0.047

Dopamine

3-200

0.8

Paracetamol

3-300

0.6

Dopamine

0.01-195.18

0.004

4

18-270

2.3

25

Paracetamol

15-225

1.4

Dopamine

0.5-160

0.079

Paracetamol

0.5-160

0.091

MWCNT/GO/GCE Dopamine MWCNT/GCE Fe2O3-GRS/GCE Pyrolytic film

carbon Dopamine

Pt/CeO2@Cu2OCPE

range LOD (µ µM)

Ref. 23

0.11 0.31

24

28

This work

Table 2. Results obtained using the proposed DPV method in the simultaneous determination of dopamine hydrochloride injection and paracetamol tablet spiked into biological fluids (human serum and urine). Samples

Amount sample (µ µM)

of Found (µ µM)

Recovery (%)

DA

PA

DA

PA

DA

PA

DA injection and PA tablet (serum)

20

20

19.41

19.30

97.07

96.05

30

30

30.78

31.07

102.6

103.56

DA injection and PA tablet (urine)

20

20

20.97

19.94

104.85

99.70

30

30

31.30

30.56

104.33

101.86

n = 3. DA: Dopamine; PA: Paracetamol


24

Page 25 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Scheme 1. Schematic representation of Pt/CeO2@Cu2O and electrochemical oxidation of DA and PA.


25


Figures

Figure 1. Powder XRD patterns of Cu2O, Cu2O@CeO2, Pt/CeO2@Cu2O, simulated patterns of Cu2O CeO2, and Pt (* represents Cu2O).


26

Page 26 of 34

Page 27 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 2. TEM images: (a&b) Cu2O_nanocubes, (c&d) Cu2O@CeO2_coreshell, (e&f) Pt/CeO2@Cu2O_nanocubes. The red dashed lines highlighting the nanocubes.


27

ACS Applied Nano Materials 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

Figure 3. (a) Elemental mapping of Cu2O@CeO2 core-shell and Cu, Ce and O respectively; (b) Elemental mapping of Pt/CeO2@Cu2O nanobox and Pt, Ce, Cu and O, respectively.


28

Page 28 of 34

Page 29 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 4. EIS spectra for the bare CPE, Cu2O, CeO2@Cu2O and Pt/CeO2@Cu2O in 5 mM of [Fe(CN)6]3-/4- in 0.1 M KCl solution. The frequency range used from 0.1 Hz to 100 kHz.


29


Figure 5. Cyclic voltammograms of bare CPE, Cu2O-CPE, Cu2O@CeO2-CPE and Pt/CeO2 modified CPEs (a) 50 µM of dopamine in 0.1 M PBS (pH 7.0) (b) 100 µM of paracetamol in 0.1 M PBS (pH 7.0).


30

Page 30 of 34

Page 31 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47


Figure 6. Cyclic voltammetry curves of different scan rate from 10 − 300 mVs-1. a) 100 µM of DA in 0.1 M PBS (pH 7.0); b) 100 µM PA in 0.1 M PBS (pH 7.0). Inset: linear calibration of peak current versus square root of scan rate.


31


Figure 7. DPV response of Pt/CeO2@Cu2O modified CPEs for (a) Dopamine from 0.5 µM to 160 µM in 0.1 M PBS (pH 7.0) (b) Paracetamol from 0.5 µM to 160 µM in 0.1 M PBS (pH 7.0). Insets: corresponding calibration plots of DPV current vs concentration.


32

Page 32 of 34

Page 33 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 8. DPV response (a) of Pt/CeO2@Cu2O modified CPEs in the presence of different concentration of dopamine and paracetamol from 100 µM to 0.5 µM at pH 7.0. Insets shows calibration plot of DPV current vs dopamine and paracetamol concentration.


33


Table of Contents

Graphical Abstract A facile synthetic method was employed for the fabrication of nanostructured Pt/CeO2@Cu2O carbon - based electrodes as efficient electrochemical sensor for dopamine and paracetamol


34

Page 34 of 34

CeO2@Cu2O Carbon-Based Electrode To

Recommend Documents