MoOx composite modified glassy carbon electrode for the electrocatalytic determination of d -penicillamine

Journal Pre-proof Sphere-like Ni3S4/NiS2/MoOx composite modified glassy carbon electrode for the electrocatalytic determination of dpenicillamine

Deivasigamani Ranjith Kumar, Marjorie Lara Baynosa, Ganesh Dhakal, Jae-Jin Shim PII:

S0167-7322(19)35688-0

DOI:

https://doi.org/10.1016/j.molliq.2020.112447

Reference:

MOLLIQ 112447

To appear in:

Journal of Molecular Liquids

Received date:

14 October 2019

Revised date:

11 December 2019

Accepted date:

2 January 2020

Please cite this article as: D.R. Kumar, M.L. Baynosa, G. Dhakal, et al., Sphere-like Ni3S4/NiS2/MoOx composite modified glassy carbon electrode for the electrocatalytic determination of d-penicillamine, Journal of Molecular Liquids(2020), https://doi.org/ 10.1016/j.molliq.2020.112447

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

© 2020 Published by Elsevier.

Journal Pre-proof Sphere-like Ni3S4/NiS2/MoOx composite modified glassy carbon electrode for the electrocatalytic determination of D-penicillamine

Deivasigamani Ranjith Kumar, Marjorie Lara Baynosa, Ganesh Dhakal, Jae-Jin Shim*

School of Chemical Engineering, Yeungnam University, 280 Daehak-ro, Gyeongsan, Gyeongbuk

Jo

ur

na

lP

re

-p

ro

of

38541, Republic of Korea

*Email address: [email protected]; Tel: +82 53 810 2587; Fax: +82 53 810 4631

1

Journal Pre-proof Abstract This article describes the synthesis of Ni3S4/NiS2/MoOx composite as an electrode material for the electrocatalytic sensor for D-penicillamine (D-PA). The detection of D-PA is important in biodiagnostics and therapeutic dosage control. The present study compared the performance of Ni3S4/NiS2/GC and Ni3S4/NiS2/MoOx/GC electrodes for the electrocatalytic detection of D-PA. The nickel sulfide phases containing MoOx demonstrated two-fold higher

of

catalytic current response than the controlled one (Ni3S4/NiS2/GC). The excellent performance of

ro

the Ni3S4/NiS2/MoOx/GC electrode is confirmed by electrochemical parameters such as

-p

electrochemical charge transfer resistance (138 Ω), diffusion coefficient (3.56910–6 cm2 s–1),

re

and catalytic rate constant (7.415105 M–1 s–1). The Ni3S4/NiS2/MoOx/GC electrode exhibited wide concentration detection of D-PA from 5 to 796 M with high sensitivity (0.08 A M-1),

lP

low limit of detection (0.26 M), and good interference tolerance ability. The proposed electrode

na

was also successfully utilized towards D-PA detection in human urine samples, wherein good

ur

recovery ranges (105.6 and 103.5%) were obtained.

Amperometry.

Jo

Keywords: Nickel sulfide; Molybdenum oxide; D-penicillamine; Cyclic voltammetry;

2

Journal Pre-proof 1. Introduction D-Penicillamine (D-PA, 2-amino-3-methyl-3-sulfanyl-butanoic acid) is a sulfurcontaining amino acid, which belongs to the aminothiol family [1]. It is a derivative of the antibiotic penicillin through hydrolytic decomposition, but it does not have antibiotic activity. Owing to its excellent metal chelating property, D-PA can be utilized in the treatment of hepatolenticular degeneration (Wilson’s disease), which means extreme copper deposition in the

of

body tissues and heavy metal poisoning [2]. In addition, D-PA is generally used for the treatment

ro

of various illnesses, such as cystinuria, primary biliary cirrhosis, rheumatoid arthritis,

-p

scleroderma, and fibrotic lung diseases [3-5]. The acceptable therapeutic dose of orally

re

administered D-PA in the human body ranges from 0.5 to 2.0 g daily [6]. Increasing the amount of D-PA intake in human therapeutics causes rashes in early treatment. Also, it can cause the loss

lP

of appetite, polymyositis, abdominal pain, agranulocytosis, loss of sense of the taste, nausea,

na

serious kidney disease, and bone marrow suppression [7-9]. Therefore, monitoring the D-PA concentration in human biological fluids is important for the treatment of the above-mentioned

ur

diseases without getting any side effect and for pharmaceutical preparation.

Jo

There are various analytical methods available for the determination of D-PA in biological and pharmaceutical preparation samples, which comprise liquid chromatography [10], nuclear magnetic resonance (NMR) spectrometry [11], colorimetry [12], chemiluminescence [13], capillary electrophoresis [14], and electrochemical methods [1]. Among these methods, the electrochemical technique with its decentralized/automated analysis has attracted tremendous interest due to the fast response, less time consumption, high sensitivity, and simple manipulation in real-time determination [15]. Numerous electrode materials have been used for the electrochemical detection of D-PA. Typically, the ―SH groups can be examined by mercury and 3

Journal Pre-proof mercury amalgam electrodes, but mercury-based electrodes have toxicity issues and easily damageable electrode surfaces, which lead to the decrease in the sensor response [16]. Gholivand et al. reported the good performance of sodium montmorillonite nanoclay modified carbon paste electrode for the electrochemical determination of D-PA despite its high operating peak potential [1]. The development of alternative electron transfer mediators for the electrocatalytic determination of D-PA is an interesting and important research endeavor. In this method,

of

emphasis is on the reduction of operating potential for the desired electrochemical reaction and

ro

enhanced selectivity and sensitivity. Salmanipour et al. developed 1-benzyl-4-ferrocenyl-1H-

-p

[1,2,3]-triazole/carbon nanotube modified electrode for the electrocatalytic detection of D-PA

re

with good limit of detection but limited dynamic concentration range [2]. Ferrocene modified electrodes, such as ferrocene carboxylic acid, 2,7-bis(ferrocenylethyl)-fluoren-9-one, and

lP

Cu2+/carbon paste electrodes, have also been utilized for D-PA determination with comparable

na

analytical parameter results [17-19]. However, the aforementioned literature reports showed limited concentration range, sensitivity, and limit of detection. Hence, the development of

ur

electrode materials with excellent analytical parameters for D-PA determination is very important.

Jo

Noble metal and metal composites are extensively used as electrode materials. However, noble metals are expensive and have issues regarding supply, therefore it is necessary to find alternative highly conducting, low cost, and earth abundant electrode materials. Recently, metal sulfides have exhibited significant performance in electronic and optoelectronic devices [20]. Ni3S4 (polydymite) and NiS2 (pyrite) are naturally occurring S-rich nickel sulfide phases [21, 22]. Great interest in using nickel sulfide in quantum dot-sensitized solar cells, hydrogen evolution reaction, oxygen evolution reaction, sodium ion batteries, supercapacitors, and electrochemical sensors has arisen due to its conductivity and low cost [22-24]. Qin et al. demonstrated that the 4

Journal Pre-proof MoS2/Ni3S4 nanosheet composite offers excellent supercapacitor performance in terms of long term cycle life at high current density [25]. Deng et al. prepared Ni3S4 nanorods with reduced graphene oxide, which was utilized as the negative electrode material in sodium ion battery application [22]. Resemble Li et al. synthesized pomegranate-like NiS2/nitrogen-doped porous carbon composites with excellent sodium ion storage ability [26]. Wu et al. fabricated hollow Ni3S2/MoOx microsphere composite with excellent catalytic activity and stability [24]. Based on

of

the above studies, Ni3S4/NiS2 along with support materials like CNT, graphene, and MoOx is

ro

expected to high electrocatalytic activity for D-PA determination. In the present work, we

-p

synthesized Ni3S4/NiS2/MoOx composite materials and modified on glassy carbon (GC) electrode for electrocatalytic determination of D-PA. The increase in the peak current comes from the

re

oxidation of Ni3S4/NiS2 to Ni3S4/NiS2(OH)2, which is catalytically reduced by the –SH (D-PA)

lP

groups in cycle. Therefore, the mechanism is EC’ in nature [27, 28]. The electrocatalytic

na

oxidation mechanism of D-PA on Ni3S4/NiS2/MoOx and the corresponding surface area and charge transfer resistance were investigated. Finally, the Ni3S4/NiS2/MoOx/GC modified

ur

electrode was used in the realistic analysis of human urine samples.

2.1. Materials

Jo

2. Experimental section

Nickel (II) nitrate hexahydrate (Ni(NO3)26H2O), thioacetamide (C2H5NS), Dpenicillamine,

potassium

ferricyanide

(K3Fe(CN)6),

and

potassium

ferrocyanide

(K4Fe(CN)6·3H2O) were purchased from Alfa Aesar, and ammonium molybdate tetrahydrate ((NH4)6Mo7O24·4H2O) was bought from Fluka. Sodium hydroxide (NaOH) was purchased from Duksan Pure Chemicals. All other reagents were received as analytical grade, and solutions were prepared using deionized (DI) water. 5

Journal Pre-proof 2.2. Synthesis of Ni3S4/NiS2/MoOx and Ni3S4/NiS2 The Ni3S4/NiS2/MoOx was synthesized as follows: the reaction mixture was prepared by mixing Ni(NO3)26H2O (232 mg), C2H5NS (90 mg), (NH4)6Mo7O24·4H2O (40 mg), and Pluronic® triblock copolymer (100 mg) in 30 mL of DI water with stirring for 30 minutes. The resulting reaction mixture was transferred into a 50 mL Teflon-lined autoclave, which was sealed and maintained at 200 °C for 24 h. The obtained black colored product was washed successively

of

with DI water and ethanol for four times and dried in a vacuum oven for 12 h. The obtained final

ro

product was labeled as Ni3S4/NiS2/MoOx. For the control experiment, Ni3S4/NiS2 was also

-p

synthesized using the above procedure without the addition of ammonium molybdate.

re

2.3. Fabrication of Ni3S4/NiS2/MoOx modified GC electrode The GC electrode (0.0707 cm2) was cleaned sequentially with 1.0, 0.3, and 0.05 μm

lP

alumina slurry followed by thorough washing with DI water and sonication for 10 minutes.

na

Afterwards, 1 mg of Ni3S4/NiS2/MoOx was dispersed in 1 mL of ethanol with 5 μL of 5% Nafion® by sonication for 20 minutes. Then, 10 μL of the Ni3S4/NiS2/MoOx suspension was

ur

dropcasted on the GC electrode surface and dried at ambient temperature. The same method was

Jo

used for the fabrication of the Ni3S4/NiS2/GC electrode. 2.4. Preparation of human urine samples Human urine samples, which were obtained from laboratory co-workers, were centrifuged at 3000 rpm for 15 minutes. The resultant supernatant solutions were collected and filtered. One milliliter each of the human urine sample was diluted 100 times in 0.1 M NaOH solution. The collected samples were directly transferred into the electrochemical cell setup without further pretreatment and tested for D-PA content by standard addition method. 2.5. Characterization 6

Journal Pre-proof X-ray diffraction (XRD) measurements were performed using a PANalytical, X-ray powder diffractometer instrument with Cu Kα radiation of λ = 0.1518 nm. The surface morphologies of the electrode materials were examined by field-emission scanning electron microscopy (FESEM, Hitachi S-4800). Transmission electron microscopy (TEM, HITACHI H7600, HRTEM, FEI-Tecnai TF-20 with accelerating voltage 200 kV). The chemical composition and elemental oxidation states of the as-prepared samples were studied by X-ray photoelectron

of

spectroscopy (XPS) using the Thermo Scientific K-Alpha X-ray Photoelectron Spectrometer,

ro

which utilizes a monochromatized Al-Kα X-ray source. All electrochemical experiments were

-p

conducted using an Autolab PGSTAT302 N (Metrohm, Netherlands) electrochemical workstation with a conventional three-electrode system. The surface modified GC (3 mm in diameter)

re

electrode, saturated calomel electrode (SCE), and platinum wire (1 mm in diameter) were used as

lP

working, reference, and counter electrodes, respectively.

na

3. Results and discussion

3.1. Surface morphology of Ni3S4/NiS2/MoOx

ur

Fig. 1 (A-D) shows the FE-SEM images of the Ni3S4/NiS2 and Ni3S4/NiS2/MoOx

Jo

samples. The Ni3S4/NiS2 images shows irregular bulk particles, size range from 1.5 to 3 m (Fig. 1(A and B)). In contrast, the Ni3S4/NiS2/MoOx sample showed comparably homogeneous microspheres (size 2 to 4.5 m) with nanosheets intertwined on the surface of the spheres (Fig. 1C and D). The thickness and diameter of the nanosheets range from 20 to 40 nm and from 150 to 300 nm, respectively. To further confirm the Ni3S4/NiS2/MoOx structure and elemental distribution are characterized by HRTEM and elemental mapping. Fig. 1(E and F) revealed the Ni3S4/NiS2/MoOx microspheres with the surface nanosheets presence, it is resemble to SEM image. The high-angle annular dark field imaging−scanning transmission electron microscopy 7

Journal Pre-proof (HAADF−STEM) technique is an important tool for the study of multi element composite materials presence and distribution. The HAADF−STEM elemental mapping study indicates that for the Ni3S4/NiS2/MoOx sample, Ni, S, Mo, and O elements are present on the entire region (Fig. 2(A-E). EDX detected Ni, S, Mo, and O elements, which further confirms the formation of Ni3S4/NiS2/MoOx sample (Fig. 2 (F)).

A B C D

-p

ro

of

A B C D

A B C D

E F

ur

E

na

lP

re

A B C D

Jo

F

Fig. 1. FESEM images of (A and B) Ni3S4/NiS2 and (C and D) Ni3S4/NiS2/MoOx composites; (E and F) HRTEM image of Ni3S4/NiS2/MoOx.

8

Journal Pre-proof

A B C D E F

re

-p

ro

of

A B C D E A FB C D E F

ur

na

lP

A B C D E A FB C D E F

Jo

Ni Mo S Ni Mo S Ni Mo SNi Mo S Ni Mo S Ni Ni Mo Mo S S

Fig. 2. (A) Scanning HAADF-STEM image of Ni3S4/NiS2/MoOx and corresponding elemental mapping of (B) Ni, (C) S, (D) Mo, (E) O, and (F) EDX spectrum elemental identification of Ni3S4/NiS2/MoOx.

9

Journal Pre-proof 3.2. XRD, FTIR, and XPS studies Fig. 3(A) displays the X-ray diffraction (XRD) patterns of the Ni3S4/NiS2 and Ni3S4/NiS2/MoOx samples. Notably, for both samples (Ni3S4/NiS2 and Ni3S4/NiS2/MoOx), two sulfide phase diffraction peaks are present, that of Ni3S4 and NiS2. The diffraction peaks at 2 values of 16.2°, 26.6°, 31.3°, 38.0°, 46.8°, 50.0°, 54.6°, 57.6°, 58.5°, 64.56°, 68.71°, and 77.46° can be indexed to the lattice planes (111), (220), (311), (400), (422), (511), (440), (531), (442), (533),

of

(444), and (553), respectively, which are well-matched with JCPDS card no. 76-1813 for Ni3S4

ro

[29]. Moreover, the diffractions peaks at 2 values of 31.4°, 38.8°, 45.1°, 53.5°, 61.0°, 70.3°, 72.5°,

-p

and 74.6° correspond to the planes (200), (210), (211), (220), (311), (321), (411), and (420),

re

respectively, which match well with JCPDS card no. 89-1495 for NiS2 [30]. For the MoOx, there are no obvious peaks that are exhibited from 10° to 80°, which confirms the amorphous behavior

lP

of the sample [31]. Also, Soultati et al. prepared MoOx film through microwave synthesis with a

na

resulting similar amorphous oxide formation [32]. Hence, the presence of MoOx in the Ni3S4/NiS2/MoOx sample was confirmed by FT-IR spectroscopy. Fig. S1 (a and b) shows the FT-

ur

IR spectra of the as-prepared Ni3S4/NiS2 and Ni3S4/NiS2/MoOx samples. For the Ni3S4/NiS2

Jo

samples Ni-S-Ni and Ni-S stretching vibration band observed at 478 and 577 cm-1, respectively [33]. Also, band for Ni-SO2 attributed around 1013 cm-1 (Fig. S1 (a)). In contrast, Ni3S4/NiS2/MoOx sample Mo-O bands exist along with Ni-S/Ni-S-Ni peaks. The various modes of Mo-O vibrations peaks at 778, 842, 996, and 1177 cm-1, are corresponds to the Mo3-Ov, Mo2O, Mo=Ov, and Mo-O-H band, respectively [34]. The Mo-Ox characteristics peaks confirmed that the presence of MoOx in Ni3S4/NiS2/MoOx sample (Fig. S1 (b)).

10

 Ni 3S 4 JCPDS no. 76 1813

Journal Pre-proof

40

(a)

80

0

S 2p3/2

Jo

2– SO4

165

n r u

Intensity (a.u)

Intensity (a.u)

l aF

E

170

Ni 2p

160

Binding Energy (eV)

Intensity (a.u)

o r p

e

500

r P

Ni 2p

E

2+

Sa

1/2

Sb

3+

Ni

890

1000

870

850

Binding Energy (eV)

F

2–

O

4+

Mo 3d 5/2 6+

Mo 3d 5/2

S 2s

4+

Mo 3d3/2 6+

Mo 3d 3/2

240

Sc Sd

Ni

f o

1000

Binding Energy (eV)

A B C D

175

Ni LLN

(b)

2Theta (dgree)

S 2p1/2

Ni 2p

S 2p S 2s C 1s

(442) (321) (533) (444) (411) (420) (553)

60

O 1s

(b) 0

     

3/2

Ni LLM

80(a)

O 1s

(321) (533) (444) (411) (420) (553)

(442) (a.u) Intensity

(531)

(440)

60

Ni 2p

Ni 3p S 2p Mo 3d / S 2s C 1s

(311) (440)



–   

A B C D

Intensity (a.u)

20



(422)

(b)

 

  



A B C D

(531)





(220) (511) (311)

(311) (200)

40

(210) (211) (400)





(220)

(a)

 NiS 2 JCPDS no. 89 –1495

(210) (400) (211) (220) (422) (511)

(111)



20

 Ni 3S 4 JCPDS no. 76 –1813

 

(220)



(b)

   



(111)

(a)

Intensity (a.u)

(311) (200)



Ni 3p

A B C D

Intensity (a.u)

 NiS 2 JCPDS no. 89 –1495 

230

Binding Energy (eV) 11

220

OH

538

534

530

Binding Energy (eV)

–

526

Journal Pre-proof Fig. 3. (A) XRD patterns of (a) Ni3S4/NiS2 and (b) Ni3S4/NiS2/MoOX, (B) XPS survey spectra of (a) Ni3S4/NiS2 and (b) Ni3S4/NiS2/MoOX, and the high-resolution spectra of Ni3S4/NiS2/MoOX in the energy range of the (C) Ni 2p, (D) S 2p, (E) Mo 3d, and (F) O 1s signals.

The detailed elemental composition and oxidation state of the as-prepared composites were further characterized by XPS studies. Fig. 3(B) shows the survey spectra of Ni3S4/NiS2 and

of

Ni3S4/NiS2/MoOx electrodes, wherein the peaks corresponding to the elements Ni, S, and O can

ro

be observed. In addition, the spectrum for Ni3S4/NiS2/MoOx indicates the presence of molybdenum oxide through the peaks corresponding to Mo 3d and O 1s (Fig. 3(B)(b)). The high

-p

resolution region spectrum of Ni3S4/NiS2/MoOx sample Ni2p peaks of Ni3S4 spinel (Ni2+ and

re

Ni3+) and NiS2 are merged spin-orbit splitting of Ni2+ 2p 2p3/2 and Ni 2p1/2 are deconvoluted

lP

binding energies are 853.3, and 870.5 eV, respectively (Fig. 3(C)). Similarly, Ni3+ binding energies exist at 854.3 eV (2p3/2) and 872.2 eV (2p1/2) [35, 36]. The core level electron splitting

na

binding energies differences (ΔE = Ni 2p1/2 - Ni 2p3/2) calculated ΔE = 17.2 eV (Ni2+) and ΔE =

ur

17.9 eV (Ni3+), which is typical nickel sulfide values [36]. The Ni 2p3/2 satellite peaks obtained at

Jo

the 856.4 (Sa) and 860.4 eV (Sb). The Ni 2p1/2 satellite also existed at 875.94, and 880.8 eV [37]. Fig. 3(D) displays the S 2p region deconvoluted into two doublets peaks. The lower binding energy spin-orbit splitting energies obtained at 161.3 and 162.7 correspond to the 2p3/2 and 2p1/2, which are attributed to the planar sulfide-sulfide sulfur atom [38]. The higher binding energy spin-orbit values at 162.5 eV (2p3/5) and 163.7 eV (2p1/2) are assigned to the S―Ni, and the peak at 168.9 eV is ascribed to the S―O bond due to the surface oxidized SO42‒ species. Fig. 3(E) shows that the Mo 3d two doublet and S 2s are overlapping at the same binding energy region. The S 2s peak binding energy exists at 226.0 eV [39]. The Mo4+ lower binding 12

Journal Pre-proof energy doublets at 227.0, and 230.1 eV correspond to the 3d5/2 and 3d3/2, respectively. The higher binding energy peaks exhibited at 232.3 and 235.5 eV are ascribed to the 3d5/2 and 3d3/2 of Mo6+. The core level spin-orbit splitting energy difference is 3.2 eV (ΔE = Mo 3d5/2 – Mo 3d3/2) [36]. The O 1s was deconvoluted into two peaks at 531.9 and 532.7 eV, which are ascribed to the O2in MoOx and the hydroxyl groups (OH-) of the Mo-OH, respectively (Fig. 3(F)) [40]. Wu et al. synthesized MoOx/Ni3S2 composites and obtained similar results for MoOx [24]. Thus, it was

of

confirmed that MoOx is present along with the Ni3S4/NiS2 phases in the sample.

ro

3.3. Electrochemical behavior of Ni3S4/NiS2/MoOx

-p

Electrochemical impedance spectroscopy (EIS) is a powerful tool to characterize the changes in the modified electrode probes [41]. The EIS study was performed in 0.1 M KCl containing 5.0

re

mM of [Fe(CN)6]3−/4− at a frequency range of 105–0.01 Hz. Fig. S2 presents the Nyquist plots of

lP

the (a) bare GC, (b) Ni3S4/NiS2/GC, and (c) Ni3S4/NiS2/MoOx/GC electrodes. A typical

na

impedance spectrum shows the Nyquist plot, which consists of a semicircle portion and a linear part. The high frequency semicircle portion is associated with the electron transfer limited

ur

process, and the low frequency linear part represents a diffusion limited process [42]. The

Jo

diameter of the high frequency semicircle part corresponds to the charge transfer resistance (Rct), which can be used to evaluate the electron transfer process of the modified electrodes. To establish the correct values of the above components, experimental data were fitted with an equivalent circuit, and corresponding values were tabulated in Table S1. The obtained Rct values of the bare GC, Ni3S4/NiS2/GC, and Ni3S4/NiS2/MoOx/GC electrodes are 288, 1420, and 133 Ω, respectively (Fig. S2(a–c)). The Ni3S4/NiS2/GC electrode shows higher Rct value indicating lower electron transfer rate compared to the Ni3S4/NiS2/MoOx/GC modified electrode, which has a lower Rct value (Fig. S2(c)) due to the amorphous structure of MoOx, led to the increase in 13

Journal Pre-proof electron transfer rate. This is evident in an earlier report on the MoOx/Ni3S2 composite, which was prepared by Wu et al. and showed electron transfer behavior aided by molybdenum oxide with metal sulfide [24]. Similarly, the Ni3S4/NiS2/MoOx/GC modified electrode also exhibited lower Rct value, which agrees with the previous study. 3.4. Electrochemical determination of D-PA The electrocatalytic determination of D-PA was performed using CV measurements. Fig.

of

4(A) presents the CV responses of the (a) bare GC, (b) Ni3S4/NiS2/GC, and (c)

ro

Ni3S4/NiS2@MoOx/GC modified electrodes in the absence (dotted lines) and presence (solid

-p

lines) of 250 µM D-PA. No peaks can be found in the CV curve of the bare GC within the

Jo

ur

na

lP

re

potential window of +0.25 to +0.5 V. After the addition of D-PA, a small increase in the

Scheme 1. The proposed electrocatalytical oxidation mechanism of of D-PA occurring on Ni3S4/NiS2/MoOx/GC. 14

Journal Pre-proof background current was observed for the bare GC (Fig. 4(A)(a)). In contrast, the Ni3S4/NiS2/GC and Ni3S4/NiS2/MoOx/GC electrodes exhibited excellent oxidation and reduction peaks at Epa = +0.38 V and Epc = +42 V. The obtained redox couple in 0.1 M NaOH reaction are written in equation 1 [43, 44]. The Ni3S4/NiS2/MoOx/GC has a higher peak current response than that of the Ni3S4/NiS2/GC electrode. The forward electrochemical oxidation of Ni(II) → Ni(III) and its reduction appeared at the negative sweep potential conversion of Ni(III) → Ni(II) (eq. 1). This

of

indicates that the nickel sulfide modified electrode’s redox couples greatly feature in the

ro

electrocatalytic activity with analytes. Upon addition of D-PA (250 µM), the anodic oxidation

-p

peak current swiftly increased for both Ni3S4/NiS2/GC and Ni3S4/NiS2@MoOx/GC electrodes (Figs. 4(A(b) and (c)). The D-PA (for reaction understanding, D-PA = R-SH) was oxidized by

re

Ni(III) of the Ni3S4/NiS2(OH)2 resulting in the R-S* structure, which consequently forms R-S-S-

lP

R (eqs. 1‒5). The chemically regenerated Ni3S4/NiS2 species (via R-SH) is electrochemically oxidized through a one-electron oxidation process in eq. 4 (scheme 1). A possible mechanism for

na

the electrocatalytic oxidation of D-PA on the surface of the Ni3S4/NiS2 electrode surface is

ur

proposed as follows:

Ni3S4/NiS2 + 2OH‒ → Ni3S4/NiS2(OH)2 + 2e‒

Jo

(1)

R–SH + OH‒ → R–S‒ + H2O

(2)

Ni3S4/NiS2(OH)2 + 2R–SH → [Ni3S4/NiS2(OH)2∙∙∙∙(HS–R)2]

(3)

2[Ni3S4/NiS2(OH)2∙∙∙∙(HS–R)2] → 2Ni3S4/NiS2 + 4H2O + 4R–S*

(4)

2R–S* → R–S–S–R

(5)

The electrocatalytic oxidation peak current response of D-PA on Ni3S4/NiS2@MoOx/GC is higher than that of the Ni3S4/NiS2/GC modified electrode. Here, Ni2+ is employed as an excellent redox couple (Ni2+/Ni3+), which is used for the catalytic oxidation of D-PA (–SH group to -S-S15

Journal Pre-proof formation. To enhance the electrocatalytic activity of single components (nickel sulfide), binary combinations, such as with another metal oxide, result in improved performance as in the recent literature on the MoOx entity [45-47]. The faster charge transfer kinetics is attributed to the MoOx, which enhanced the catalytic activity through the auxiliary effects of the amorphous MoOx [24].

A B C D

48

40

44

ro

20

90

120

150

a 180

Conc. of D-PA (M)

re

b a

60

-p

20



40

2

R = 0.9846

of

I / A

c

40



f

A B C D

0.4

−20

0.5

na

−20 0.3

0

lP

0

0.3

0.4

Potential / (V vs. SCE)

0.5

ur

Potential / (V vs. SCE)

Jo

Fig. 4. (A) CV curves of the (a) bare GC, (b) Ni3S4/NiS2/GC, and (c) Ni3S4/NiS2/MoOx/GC electrodes in 0.1 M NaOH at a scan rate of 100 mV s–1. The dotted and solid lines indicate the absence and presence of 250 µM D-PA in the electrolyte solution. (B) CV curves of the Ni3S4/NiS2/MoOx/GC electrode in the presence of D-PA with increasing concentration from 60 to 180 μM at a scan rate of 100 mV s-1 in 0.1 M NaOH. Inset: corresponding calibration plot of current as a function of the concentration of D-PA.

In a previous study, Yan et al. emphasized the pronounced impact of amorphous MoOx matrix on 16

Journal Pre-proof the catalytic activity of CoO/MoOx material towards hydrogen and oxygen evolution reactions [48]. Likewise, the Pt/MoOx-C modified electrode facilitated the electro-oxidation of methanol with ∽3 times higher efficiency than that of the Pt/C−H electrode [47]. The aforementioned results are in accordance with the present study on the electro-oxidation of D-PA on

Icat / I L



100

of

A 5B C D

A B C D

2

R = 0.999

ro

200

re

10 mM

-p

4

blank

0

20

lP

2 mM

0

Time (s)

0.65

0.66

0.67

1/2 1/2

t (s )

na

A B C D 4.6

400

Jo

Icat / I L

ur

A B C D



0.64

40

4.4

2

R = 0.990

200

4.2 10 mM

0

2 mM

blank

0

20

4

40

Time (s)

0.64

0.65

1/2

t1/2(s )

0.66

Fig. 5. (A) Chronoamperograms of the Ni3S4/NiS2/GC electrode at varying concentrations of D17

Journal Pre-proof PA (Inset: current versus t–½).

(B) Plot of Icat/IL versus t½ obtained from the data of the

chronoamperometric (8 mM D-PA) measurements. (C) Chronoamperograms of the Ni3S4/NiS2/MoOx/GC electrode at varying concentrations of D-PA (Inset: current versus t–½). (D) Plot of Icat/IL versus t½ obtained from the data of the chronoamperometric (8 mM D-PA) measurements. All measurements were carried out at an operating potential of +0.42 V in 0.1 M

ro

of

NaOH.

-p

Ni3S4/NiS2/MoOx/GC electrode resulting in a significantly improved peak current response compared to the Ni3S4/NiS2/GC modified electrode. In Fig. 4(A)(c) CV curve found that the

re

Ni2+/Ni3+ is a reversible redox species at absence of analyte (dashed line). Though, consecutive

lP

addition of D-PA lead to increase the catalytic currents with respect to the analyte concentration. It is due to the reductive addition of Ni2+ to D-PA resulting disulfide formation -S-S-,

na

simultaneously Ni3+ regenerated by anodic oxidation. The effect of increasing concentrations of

ur

D-PA from 60 to 180 μM on the electrocatalytic activity of the Ni3S4/NiS2/MoOx/GC electrode

Jo

was investigated (Fig. 4(B)). Increasing the D-PA concentration resulted in a linear increase in the catalytic peak current with typical cathodic current decreases, which proves the electrocatalytic behavior of the Ni3S4/NiS2/MoOx/GC electrode [49]. The obtained linear regression equation for anodic current is Ipa (μA) = 0.0868 CD-PA + 32.843 (R2 = 0.9846) (Fig. 4(B), inset). This clearly indicates that the modified electrode is a promising composite material for the electrochemical determination of D-PA. 3.5. Reaction kinetics of D-PA on Ni3S4/NiS2/MoOx/GC The CV plots (Figs. S3(A and B)) revealed that increasing the scan rate results in an 18

Journal Pre-proof increase in the peak current. The trend wherein the peak current increases with the scan rate denotes a diffusion-controlled process. It is further confirmed by the double logarithmic plot of current versus scan rate where the slope values of Ni3S4/NiS2/GC and Ni3S4/NiS2/MoOx/GC electrodes are 0.50 and 0.55, respectively (Fig. S3(C and D)). Furthermore, in order to gain more insight on the electrocatalytic oxidation process of D-PA on Ni3S4/NiS2/GC and Ni3S4/NiS2@MoOx/GC, chronoamperometry studies were carried out. This technique is used to

of

estimate the diffusion coefficient and rate constant of the analyte on the modified electrode. The

ro

chronoamperometric measurements were performed at various concentrations from 2 to 10 mM of D-PA on the Ni3S4/NiS2/GC and Ni3S4/NiS2/MoOx/GC electrode at an operating potential of

-p

+0.42 V (Fig. 5(A–D)). Based on the slope of the plot of current (I) versus t–1/2 at varying

re

concentrations of D-PA (Fig. 5(A and C, insets)), the diffusion coefficient (D) of D-PA in the two

lP

systems were calculated using the Cottrell equation (eq. 6): I = nFACD½π –½t–½

(6)

na

where D is the diffusion coefficient (cm2 s–1), C is the bulk concentration of D-PA (mol cm–3), A

ur

is the geometric area of the GC electrode (cm2), and I corresponds to the current measured

Jo

during the diffusion of D-PA from the bulk solution towards the electrode/electrolyte portion. The calculated D values of the Ni3S4/NiS2/GC and Ni3S4/NiS2/MoOx/GC electrodes are 1.64410–6 cm2 s–1 and 3.56910–6 cm2 s–1, respectively. The high diffusion coefficient value of the Ni3S4/NiS2/MoOx/GC electrode, which was revealed by nanometer-sized flake-like sheets surface morphologies, results in a shorter diffusion path length of the D-PA when compared with the bulky irregular particles of the Ni3S4/NiS2 modified electrode. This is confirmed by the electrochemical active surface area measurement through OH- diffusion coefficient. In addition, the chronoamperometry studies can be utilized to estimate the catalytic rate constant (kcat M–1 s–1) 19

Journal Pre-proof of D-PA using the following equation (eq. 7): Icat/IL = (πkcatC0t)½

(7)

where IL and Icat denote the current response of the modified electrodes in the absence and presence of D-PA. Figs. 5(B) and (D) display the plots of Icat/IL versus t½ for a D-PA concentration of 8 mM for the Ni3S4/NiS2/GC and Ni3S4/NiS2/MoOx/GC electrodes, respectively. From the slopes of these plots, the calculated catalytic rate constants for Ni3S4/NiS2/GC and

of

Ni3S4/NiS2/MoOx/GC are 6.092104 M–1 s–1 and 7.415105 M–1 s–1, respectively.

ro

In summary, the Ni3S4/NiS2@MoOx/GC modified electrode has a higher diffusion coefficient

-p

and catalytic rate constant than the Ni3S4/NiS2/GC. The high catalytic rate constant of Ni3S4/NiS2/MoOx/GC electrode might be attributed to the sheet-like morphologies and

re

interconnected redox active sites. This is confirmed by measurements done on both

lP

(Ni3S4/NiS2/GC and Ni3S4/NiS2/MoOx/GC) electrodes in the absence of analyte at varying scan

na

rates (5400 mV s-1) in 0.1 M NaOH electrolyte. The interconnected sheet-like structured Ni3S4/NiS2/MoOx/GC revealed higher current response than those of the bulk particles of

ur

Ni3S4/NiS2/GC. The plot of the square root of scan rate versus oxidation (Ni2+) peak current

Jo

resulted in a linear plot where the slope gives the diffusion coefficient (D) of OH- using the Randles–Sevcik equation (eq. 8) [50], where Ip is the peak current (µA), n the number of electrons involved in the redox reaction, A the electrode surface area (cm 2), DOH- the diffusion coefficient of the modified electrode (cm2 s-1), C-OH- the concentration of protons (M), and ν scan rate (V s-1). The diffusion coefficient is directly related to the electrochemical surface area of the active materials. (8) The

ratio

of

the

diffusion

coefficients 20

of

the

two

samples

is

given

by:

Journal Pre-proof D(Ni3S4/NiS2/MoOx)/D(Ni3S4/NiS2) = [(Ip/ν1/2) (Ni3S4/NiS2/MoOx)/(Ip/ν1/2) (Ni3S4/NiS2)]2 = (10.20/7.25)2 = 1.98. The resulting Ni3S4/NiS2/MoOx diffusion coefficient is almost twice as much as that of the Ni3S4/NiS2 electrode material. This indicates that the Ni3S4/NiS2/MoOx electrode material provides facile access to the mobility of the D-PA molecules. 3.6. Amperometric detection of D-PA Fig. 6(A) shows the amperometric measurement (I-t curve) with the successive addition

of

of each 20 M D-PA at an operating potential of +0.42 V. The I-t plots of Ni3S4/NiS2/GC (curve

ro

(a)) and Ni3S4/NiS2/MoOx/GC (curve (b)) electrodes clearly indicate that the composite with

-p

MoOx has higher current response than the nickel sulfide electrode alone using the same experimental conditions. The current response of both Ni3S4/NiS2/GC and Ni3S4/NiS2/MoOx/GC

re

increased over the concentration range of 20 to 196 M. The obtained linear regression equations

lP

for the Ni3S4/NiS2/GC and Ni3S4/NiS2/MoOx/GC electrodes are Y = 0.0559 X + 1.844 (R2 =

na

0.9972) and Y = 0.146 X + 3.1088 (R2 = 0.9959), respectively (Fig. 6(B)). Furthermore, to validate the capability of the Ni3S4/NiS2/MoOx/GC modified electrode to determine D-PA on a

ur

wide concentration range, the modified electrode was tested using D-PA concentrations ranging

Jo

from 5 to 796 M (Fig. 6(C)). The acquired linear equation is Y = 0.08X -0.6324 (R2 = 0.993). In addition, the calculated limit of detection (LOD) for D-PA is 0.26 M using the equation, LOD = 3σ/s, where σ is the standard deviation of the signal in the absence of analyte and s is the sensitivity of the electrode, which can be obtained from the slope of the calibration curve (Fig. 6(D)). The performance of the proposed electrode was compared with the results in the literature, as shown in Table S2. The Ni3S4/NiS2/MoOx/GC modified electrode exhibits excellent values of linear range, operating potential, and limit of detection. 3.7. Reproducibility, stability, and interference studies 21

Journal Pre-proof To evaluate the reproducibility of the Ni3S4/NiS2/MoOx/GC electrode, five different electrodes were prepared and used for the detection of D-PA, The relative standard deviation (RSD) of the slopes of the five calibration plots, which were derived from the amperometry experiments was calculated to be 6.9%, indicating the good reproducibility of the fabricated Ni3S4/NiS2/MoOx/GC electrode. The stability of the as-fabricated electrode during the long-term storage was tested after fourteen days. The RSD value of the slopes of the calibration plots from

of

the five sets of experiments was found to be 6.8%, which clearly reveals the excellent stability of

30

A B C D

b

A B C D

-p

30



a

na

10

0 200

400

20

2

R = 0.9972

100

600

Conc. of D −PA 

Time (s)

An o B C D

Jo

A B C D 60

m

f

l

e 5

d a

40

k

c

b

j i

0

g

h

20 0

200

400

Time (s)

0 0

a b

10

0

ur

0

 

a b

2

R = 0.9959

re

20

lP



ro

the modified electrode during storage.

1000

Time (s) 22

200

Journal Pre-proof Fig. 6. (A) Amperometric I-t curves of the (a) Ni3S4/NiS2/GC and (b) Ni3S4/NiS2/MoOx/GC electrodes with 20 μM successive additions of D-PA at an applied potential of +0.42 V with their corresponding (B) calibration plots: (a) Ni3S4/NiS2/GC and (b) Ni3S4/NiS2/MoOx/GC. (C) Amperometric I–t response of the Ni3S4/NiS2/MoOx/GC modified electrode in varying D-PA concentrations from 5 to 796 μM in 0.1 M NaOH at an operating potential of +0.42 V with the middle inset showing the enlarged amperometric response, (D) calibration plot of current vs. D-

ro

of

PA concentration.

-p

Furthermore, the selectivity of the Ni3S4/NiS2/MoOx/GC electrode for D-PA was also tested using a four-fold higher concentration of commonly interfering bioactive species like ascorbic

re

acid (AA), uric acid (UA), sodium nitrate (NaNO3), glucose (GLU), and fructose (FA). Moreover,

lP

homocysteine (HA), cysteine (CySH), and glutathione (GLT) with the same concentrations as DPA were also added. The other common metal ions interference such as Zn2+ and Cu2+ also tested

na

with D-PA. Fig. S4 (A and B) shows that no obvious current response changes were observed

ur

with the addition of common bioactive molecules such as AA, UA, NaNO3, GLU, and FA, Cu2+

Jo

and Zn2+. In contrast, thiol-containing interferences, HA, CySH, and GLT, induced small current changes, which are given in terms of percentage (Fig. S4 (A and C)). These studies confirmed that the proposed Ni3S4/NiS2/MoOx/GC modified electrode could be applied in the real time detection of D-PA in human urine samples even in the presence of common interferents. 3.8. Real-sample analysis In order to evaluate the realistic application of the Ni3S4/NiS2/MoOx/GC electrode, the detection of D-PA in human urine samples was carried out by standard addition method. The asprepared human urine samples were diluted using appropriate volumes and were used to perform 23

Journal Pre-proof amperometric measurements. The resulting amperometry upon the standard addition of D-PA on the modified electrode. From the calibration plot, the y-intercepts on the x-axis give the concentration of D-PA as 10.56 and 20.7 µM with the addition of 10.00 and 20.00 µM, respectively. Recovery values of 105.6 and 103.5% prove the practicability of applying the asfabricated electrode as a realistic D-PA sensor. 4. Conclusion

of

In this study, we synthesized Ni3S4/NiS2 and Ni3S4/NiS2/MoOx electrode materials by a

ro

one-pot hydrothermal method. The as fabricated Ni3S4/NiS2/GC and Ni3S4/NiS2/MoOx/GC

-p

electrodes were effectively utilized for the electrocatalytic determination of D-PA. The Ni3S4/NiS2/MoOx/GC electrode possesses unique advantages over the Ni3S4/NiS2/GC, such as

re

lower impedance (Rct), high catalytic peak current (Icat), diffusion coefficient (D), catalytic rate

lP

constant (k) and excellent sensitivity (s). The detailed electrocatalytic oxidation mechanism of DPA on the Ni3S4/NiS2/MoOx/GC electrode was proposed. The proposed electrode can operate in a

na

wide concentration range of D-PA from 5 to 796 M at a low operating potential of +0.42 V. The

its

practicability

was

tested

under

an

optimized

system,

wherein

the

Jo

Finally,

ur

optimized electrode offered high sensitivity (0.08 A M–1) and low limit of detection (0.26 M).

Ni3S4/NiS2/MoOx/GC electrode revealed good recovery ranges of D-PA in human urine samples. Therefore, the proposed Ni3S4/NiS2/MoOx electrode material can be used in realistic sensor applications. Acknowledgments This study was supported by the National Research Foundation (NRF) of the Republic of Korea under the frameworks of Priority Research Centers Program (NRF-2014R1A6A1031189) and Basic Science Research Program (NRF-2015R1D1A1A09060292), funded by the Ministry 24

Journal Pre-proof of Education of Korea, and International Cooperation Program (NRF-2015K2A2A7053101). Declaration of interests ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

References [1] M.B. Gholivand, M. Shamsipur, S. Dehdashtian, N.B. Adeh, Construction of a sensitive sensor for D-

of

penicillamine using sodium montmorillonite nonoclay as a modifier, Journal of Electroanalytical Chemistry, 725 (2014) 7-11.

ro

[2] A. Salmanipour, M.A. Taher, H. Beitollahi, R. Hosseinzadeh, An electrochemical sensor based on 1benzyl-4-ferrocenyl-1H-[1,2,3]-triazole/carbon nanotube; detection of D-penicillamine in the presence

-p

of tryptophan, Materials Science and Engineering: C, 33 (2013) 3160-3165. [3] J.C. Crawhall, C.J. Thompson, Cystinuria: Effect of D-Penicillamine on Plasma and Urinary Cystine

re

Concentrations, Science, 147 (1965) 1459-1460.

[4] R. Saetre, D.L. Rabenstein, Determination of penicillamine in blood and urine by high performance

lP

liquid chromatography, Analytical Chemistry, 50 (1978) 276-280. [5] M.E. Suarez‐Almazor, E. Belseck, C. Spooner, Penicillamine for treating rheumatoid arthritis,

na

Cochrane Database of Systematic Reviews, (2000).

[6] M. Mazloum-Ardakani, H. Beitollahi, Z. Taleat, H. Naeimi, N. Taghavinia, Selective voltammetric determination of d-penicillamine in the presence of tryptophan at a modified carbon paste electrode 6.

ur

incorporating TiO2 nanoparticles and quinizarine, Journal of Electroanalytical Chemistry, 644 (2010) 1-

Jo

[7] Cuprimine Side Effects Center,

https://www.rxlist.com/cuprimine-side-effects-drug-

center.htm#overview, 2018.

[8] D. Joly, P. Rieu, A. Méjean, M.-F. Gagnadoux, M. Daudon, P. Jungers, Treatment of cystinuria, Pediatric Nephrology, 13 (1999) 945-950. [9] G. Dunea, Kidney Stones: Medical and Surgical Management, JAMA, 276 (1996) 577-577. [10] K. Kuśmierek, E. Bald, Simultaneous determination of tiopronin and d-penicillamine in human urine by liquid chromatography with ultraviolet detection, Analytica Chimica Acta, 590 (2007) 132-137. [11] S.E. Ibrahim, A.A. Al-badr, Application of PMR Spectrometry in Quantitative Analysis of Penicillamine, Spectroscopy Letters, 13 (1980) 471-478. [12] A. Besada, N.B. Tadros, Y.A. Gawargious, Spectrophotometric Determination of Pure and CapsuleFormulated Penicillamine, Analytical Letters, 20 (1987) 809-820. [13] Z. Zhang, W.R.G. Baeyens, X. Zhang, Y. Zhao, G. Van Der Weken, Chemiluminescence detection 25

Journal Pre-proof coupled to liquid chromatography for the determination of penicillamine in human urine, Analytica Chimica Acta, 347 (1997) 325-332. [14] J. Russell, D.L. Rabenstein, Speciation and Quantitation of Underivatized and Ellman's Derivatized Biological Thiols and Disulfides by Capillary Electrophoresis, Analytical Biochemistry, 242 (1996) 136144. [15] R.M. Wightman, Probing Cellular Chemistry in Biological Systems with Microelectrodes, Science, 311 (2006) 1570-1574. [16] G.T. Yamashita, D.L. Rabenstein, Determination of penicillamine, penicillamine disulfide and penicillamine-glutathione mixed disulfide by high-performance liquid chromatography with electrochemical detection, Journal of Chromatography B: Biomedical Sciences and Applications, 491

of

(1989) 341-354.

[17] J.-B. Raoof, R. Ojani, F. Chekin, Electrochemical Analysis of D-Penicillamine Using a Carbon Paste

ro

Electrode Modified with Ferrocene Carboxylic Acid, Electroanalysis, 19 (2007) 1883-1889. [18] J.-B. Raoof, R. Ojani, F. Chekin, Voltammetric sensor for D-penicillamine determination based on

-p

its electrocatalytic oxidation at the surface of ferrocenes modified carbon paste electrodes, Journal of Chemical Sciences, 121 (2009) 1083.

re

[19] A. Ghaffarinejad, F. Hashemi, Z. Nodehi, R. Salahandish, A simple method for determination of dpenicillamine on the carbon paste electrode using cupric ions, Bioelectrochemistry, 99 (2014) 53-56.

lP

[20] X. Rui, H. Tan, Q. Yan, Nanostructured metal sulfides for energy storage, Nanoscale, 6 (2014) 9889-9924.

na

[21] R.L. Kautz, M.S. Dresselhaus, D. Adler, A. Linz, Electrical and Optical Properties of Ni${\mathrm{S}}_{2}$, Physical Review B, 6 (1972) 2078-2082. [22] J. Deng, Q. Gong, H. Ye, K. Feng, J. Zhou, C. Zha, J. Wu, J. Chen, J. Zhong, Y. Li, Rational Synthesis

ur

and Assembly of Ni3S4 Nanorods for Enhanced Electrochemical Sodium-Ion Storage, ACS Nano, 12 (2018) 1829-1836.

Jo

[23] P. Luo, H. Zhang, L. Liu, Y. Zhang, J. Deng, C. Xu, N. Hu, Y. Wang, Targeted Synthesis of Unique Nickel Sulfide (NiS, NiS2) Microarchitectures and the Applications for the Enhanced Water Splitting System, ACS Applied Materials & Interfaces, 9 (2017) 2500-2508. [24] Y. Wu, G.-D. Li, Y. Liu, L. Yang, X. Lian, T. Asefa, X. Zou, Overall Water Splitting Catalyzed Efficiently by an Ultrathin Nanosheet-Built, Hollow Ni3S2-Based Electrocatalyst, Advanced Functional Materials, 26 (2016) 4839-4847. [25] S. Qin, T. Yao, X. Guo, Q. Chen, D. Liu, Q. Liu, Y. Li, J. Li, D. He, MoS2/Ni3S4 composite nanosheets on interconnected carbon shells as an excellent supercapacitor electrode architecture for long term cycling at high current densities, Applied Surface Science, 440 (2018) 741-747. [26] J. Li, J. Li, D. Yan, S. Hou, X. Xu, T. Lu, Y. Yao, W. Mai, L. Pan, Design of pomegranate-like clusters with NiS2 nanoparticles anchored on nitrogen-doped porous carbon for improved sodium ion 26

Journal Pre-proof storage performance, Journal of Materials Chemistry A, 6 (2018) 6595-6605. [27] K. Senthilkumar, J.-M. Zen, Free chlorine detection based on EC’ mechanism at an electroactive polymelamine-modified electrode, Electrochemistry Communications, 46 (2014) 87-90. [28] K.R. Ward, N.S. Lawrence, R.S. Hartshorne, R.G. Compton, Cyclic Voltammetry of the EC′ Mechanism at Hemispherical Particles and Their Arrays: The Split Wave, The Journal of Physical Chemistry C, 115 (2011) 11204-11215. [29] R. Karthikeyan, M. Navaneethan, J. Archana, D. Thangaraju, M. Arivanandhan, Y. Hayakawa, Shape controlled synthesis of hierarchical nickel sulfide by the hydrothermal method, Dalton Transactions, 43 (2014) 17445-17452. [30] M. Lu, X.-P. Yuan, X.-H. Guan, G.-S. Wang, Synthesis of nickel chalcogenide hollow spheres using

of

an l-cysteine-assisted hydrothermal process for efficient supercapacitor electrodes, Journal of Materials Chemistry A, 5 (2017) 3621-3627.

ro

[31] C. Guo, X. Sun, X. Kuang, L. Gao, M. Zhao, L. Qu, Y. Zhang, D. Wu, X. Ren, Q. Wei, Amorphous Codoped MoOx nanospheres with a core–shell structure toward an effective oxygen evolution reaction,

-p

Journal of Materials Chemistry A, 7 (2019) 1005-1012.

[32] A. Soultati, I. Kostis, P. Argitis, D. Dimotikali, S. Kennou, S. Gardelis, T. Speliotis, A.G. Kontos, D.

re

Davazoglou, M. Vasilopoulou, Dehydration of molybdenum oxide hole extraction layers via microwave Chemistry C, 4 (2016) 7683-7694.

lP

annealing for the improvement of efficiency and lifetime in organic solar cells, Journal of Materials [33] P.-F. Yin, C. Zhou, X.-Y. Han, Z.-R. Zhang, C.-H. Xia, L.-L. Sun, Shape and phase evolution of nickel

na

sulfide nano/microcrystallines via a facile way, Journal of Alloys and Compounds, 620 (2015) 42-47. [34] G. Tsilomelekis, S. Boghosian, In Situ Raman and FTIR Spectroscopy of Molybdenum(VI) Oxide Supported on Titania Combined with 18O/16O Exchange: Molecular Structure, Vibrational Properties,

ur

and Vibrational Isotope Effects, The Journal of Physical Chemistry C, 115 (2011) 2146-2154. [35] R. Karthikeyan, D. Thangaraju, N. Prakash, Y. Hayakawa, Single-step synthesis and catalytic activity

Jo

of structure-controlled nickel sulfide nanoparticles, CrystEngComm, 17 (2015) 5431-5439. [36] D. Briggs, Handbook of X-ray Photoelectron Spectroscopy C. D. Wanger, W. M. Riggs, L. E. Davis, J. F. Moulder and G. E.Muilenberg Perkin-Elmer Corp., Physical Electronics Division, Eden Prairie, Minnesota, USA, 1979. 190 pp. $195, Surface and Interface Analysis, 3 (1981) v-v. [37] P. Yu, L. Wang, J. Wang, D. Zhao, C. Tian, L. Zhao, H. Yu, Graphene-like nanocomposites anchored by Ni3S2 slices for Li-ion storage, RSC Advances, 6 (2016) 48083-48088. [38] D. Ranjith Kumar, S. Kesavan, M.L. Baynosa, J.-J. Shim, Flower-like Cu1.8S nanostructures for highperformance flexible solid-state supercapacitors, Applied Surface Science, 448 (2018) 547-558. [39] L. Sangaletti, F. Parmigiani, T. Thio, J.W. Bennett, Electronic-correlation effects in the x-rayphotoemission spectra of ${\mathrm{NiS}}_{2}$, Physical Review B, 55 (1997) 9514-9519. [40] S. Shao, J. Liu, J. Bergqvist, S. Shi, C. Veit, U. Würfel, Z. Xie, F. Zhang, In Situ Formation of MoO3 in 27

Journal Pre-proof PEDOT:PSS Matrix: A Facile Way to Produce a Smooth and Less Hygroscopic Hole Transport Layer for Highly Stable Polymer Bulk Heterojunction Solar Cells, Advanced Energy Materials, 3 (2013) 349-355. [41] R. Ehret, W. Baumann, M. Brischwein, A. Schwinde, K. Stegbauer, B. Wolf, Monitoring of cellular behaviour by impedance measurements on interdigitated electrode structures, Biosensors and Bioelectronics, 12 (1997) 29-41. [42] A. Hatamie, R. Rahmati, E. Rezvani, S. Angizi, A. Simchi, Yttrium Hexacyanoferrate Microflowers on Freestanding Three-Dimensional Graphene Substrates for Ascorbic Acid Detection, ACS Applied Nano Materials, 2 (2019) 2212-2221. [43] Y. Li, J. Xu, H. Liu, Y. Liu, M. Wang, J. Li, H. Cui, Surface topography control of NiS/Ni3S4 nanosheets for the promotion of electrochemical performance, Journal of Sol-Gel Science and

of

Technology, 87 (2018) 546-553.

[44] J. Wang, ANALYTICAL ELECTROCHEMISTRY John Wiley & Sons, Inc., Hoboken, New Jersey, 2006.

ro

[45] K.V. Ozdokur, B. Demir, E. Atman, A.Y. Tatli, B. Yilmaz, D.O. Demirkol, S. Kocak, S. Timur, F.N. Ertas, A novel ethanol biosensor on pulsed deposited MnOx-MoOx electrode decorated with Pt

-p

nanoparticles, Sensors and Actuators B: Chemical, 237 (2016) 291-297. [46] N.R. Elezović, B.M. Babić, V.R. Radmilović, S.L. Gojković, N.V. Krstajić, L.M. Vračar, Pt/C doped by

re

MoOx as the electrocatalyst for oxygen reduction and methanol oxidation, Journal of Power Sources, 175 (2008) 250-255.

lP

[47] Z. Yang, M. Li, P. Cui, G. Zhang, X. Jiang, Y. Wang, Designed Formation of Hollow Pt Nanocrystals Supported on MoOx-Modified Carbon for High-Performance Methanol Electro-Oxidation, ACS

na

Sustainable Chemistry & Engineering, 6 (2018) 14026-14032. [48] X. Yan, L. Tian, S. Atkins, Y. Liu, J. Murowchick, X. Chen, Converting CoMoO4 into CoO/MoOx for 3749.

ur

Overall Water Splitting by Hydrogenation, ACS Sustainable Chemistry & Engineering, 4 (2016) 3743[49] C. Sandford, M.A. Edwards, K.J. Klunder, D.P. Hickey, M. Li, K. Barman, M.S. Sigman, H.S. White, S.D.

Jo

Minteer, A synthetic chemist's guide to electroanalytical tools for studying reaction mechanisms, Chemical Science, 10 (2019) 6404-6422. [50] S. Liu, S.C. Jun, Hierarchical manganese cobalt sulfide core–shell nanostructures for highperformance asymmetric supercapacitors, Journal of Power Sources, 342 (2017) 629-637.

28

Journal Pre-proof AUTHOR STATEMENT

Title: Sphere-like Ni3S4/NiS2/MoOx composite modified glassy carbon electrode

for the electrocatalytic determination of D-penicillamine 1. Deivasigamani Ranjith Kumar: Conceptualization, Data curation, Investigation, Visualization, Writing - original draft. 2. Marjorie Lara Baynosa: Writing - review & editing.

of

3. Ganesh Dhakal: Image editing, graphical abstract drawing.

Jo

ur

na

lP

re

-p

ro

4. Jae-Jin Shim: Project administration and Supervision.

29

Journal Pre-proof

Graphical Abstract

f o

l a

e

o r p

r P

n r u

Jo

30

Journal Pre-proof

Highlights  Ni3S4/NiS2/MoOx composite were synthesized by hydrothermal method.  Ni3S4/NiS2/MoOx/GC was used for electrocatalytic detection of D-penicillamine.  Ni3S4/NiS2/MoOx/GC exhibited higher current response than Ni3S4/NiS2/GC.

Jo

ur

na

lP

re

-p

ro

of

 Ni3S4/NiS2/MoOx/GC exhibited wide range detection of D-penicillamine 5 - 796 M.

31