Potentiometric detection of copper ion using chitin grafted polyaniline electrode

Journal Pre-proof Potentiometric detection of copper ion using chitin grafted polyaniline electrode

Vinay Kr Singh, Chandra Shekhar Kushwaha, S.K. Shukla PII:

S0141-8130(19)36328-7

DOI:

https://doi.org/10.1016/j.ijbiomac.2019.12.209

Reference:

BIOMAC 14237

To appear in:

International Journal of Biological Macromolecules

Received date:

9 August 2019

Revised date:

17 December 2019

Accepted date:

23 December 2019

Please cite this article as: V.K. Singh, C.S. Kushwaha and S.K. Shukla, Potentiometric detection of copper ion using chitin grafted polyaniline electrode, International Journal of Biological Macromolecules(2018), https://doi.org/10.1016/j.ijbiomac.2019.12.209

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.

© 2018 Published by Elsevier.

Journal Pre-proof Potentiometric detection of copper ion using chitin grafted polyaniline electrode Vinay Kr Singh1, Chandra Shekhar Kushwaha2 and S.K. Shukla2* 1

2

Department of Chemistry, Sri Aurobindo College, University of Delhi, Delhi-110017, India.

Department of Polymer Science, Bhaskaracharya College of Applied Sciences, University of Delhi, Delhi-110075, India;

Corresponding author Tel. 091-11-25087595: Fax: 091-11-25081015; Email: [email protected] (S.K.

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*

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Shukla).

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ABSTRACT

Potentiometric detection of copper ion over chemically interactive and electrically responsive

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chitin grafted polyaniline (Chit-g-PANI) electrode has been demonstrated for natural as well as

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artificial samples under optimized conditions using a portable sensing setup. The physical properties and chemical structure of developed electrode were evaluated by different Infra red

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spectrometry, X-ray diffraction, scanning electron microscope, thermal gravimetric analyzer and

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ASTM methods. The result indicates the formation of electrically responsive, chemically interactive, stable grafted hybrid matrix for durable and reproducible potentiometric electrode for a self-designed portable potentiometric cell. The potentiometric response of electrode toward Cu2+ ions follows the nernst relation in the range from 1 to 103 ppm with detection limit of 13.77 ppm and negligible interference for different co-existing cations and anions. Further, on the basis of interaction between cupric ion and Chit-g-PANI matrix, the sensing mechanism and ion to electron transduction has been discussed along with future prospects for on-site applications.

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Journal Pre-proof Keywords: Chitin grafted polyaniline; potentiometric detection; sensing mechanism.

1. Introduction Copper is an important element for humans, animals and plants for various physiological process as well as in different industries. Its optimum concentration is essential to regulate the

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functioning of different organs and metabolic processes [1]. However, excess concentration of

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copper is hazardous and causes toxicity in water as well as several diseases like nausea,

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diarrhoea, tissue injury and lever damage in humans [2]. The accumulation of Cu2+ ion in the neuronal cytoplasm causes alzheimer's and parkinson's diseases [3, 4]. Further, the oxidation

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potential of copper ion is also high, which causes toxicity when ingested in excess. As the

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difference between toxic and essential concentration levels of copper is quite small, thus its

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accurate detection at low concentration is highly desirable in analytical chemistry [5]. The techniques used for detection of Cu2+ are atomic absorption spectroscopy [6], ion

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chromatography [7], chemiluminescence [8], fluorimetric spectroscopy [9], resonance scattering

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spectroscopy [10] and spectrophotometric [11]. Although some of these techniques are very sensitive, reliable and efficient but they bear several drawbacks like bulky size instruments, sophisticated procedure, high cost and long analysis time. These techniques are also not suitable for on-site monitoring of copper in different sources. As a consequence, it is of great interest to develop a portable sensor, for determination of Cu2+ concentration in biological fluid, food, water and other environmental samples [12]. Regarding, this different sensors like electrochemical (voltammetric, amperometric and potentiometric) and opto-chemical have been reported for determination of trace amount of copper [13]. In the different electrochemical method, potentiometric sensing method is more reliable due to high degree of linearity [14].

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Journal Pre-proof However, the efficiency of potentiometric sensor is depending on used electrode materials. Further, the current progress in material science has produced several advanced electrode materials comprising of metal oxides, polymers and carboneous materials with newer ion to electron transformation mechanism, miniaturized and calibration free in nature [15]. In this context

several

conducting

polymers

like

polypyrrole,

polythiophene,

polyaniline,

polynapthalene have also been explored as electrode materials to be probed in potentiometry for

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efficient sensing of metal ions [16, 17]. Among, different CPs the polyaniline (PANI) is

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frequently explored in sensing technology due to ease of synthesis, low cost and high stability.

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However, the processability, biocompatibility and functionality of PANI restrict its long term

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applications in sensing technology. It is reported that composite formation, size confinements and grafting of PANI with biopolymers make it more suitable in sensing sciences due to

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biocompatibility, responsiveness and formation of interactive sites [18-21]. Shukla et al. reported

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that film forming ability, mechanical strength and responsiveness of PANI can be improved by grafting them with biopolymers [22-24]. In an example the grafting of diethylenetriamine with

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glyoxal crosslinked chitosan yields improved mechanical strength and biocompatible in

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composite structure. The grafting generates more interactive sites for efficient adsorption of several heavy metal ions like Cu, Pb, Zn, Cd, Ni and Cr. The composite with better adsorption and interactive sites will also be more suitable for making better sensors [25, 26]. The grafted PANI with a biopolymer was reported suitable for advancing the sensing technology due to generation of functionality along with the optimized the surface properties like reactivity and porosity [27].

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Journal Pre-proof In this context, Chit is a biodegradable, long-chain biopolymer, which can be extracted from shell of moluscus. The availability of -NHCO- group in each glucose ring of Chit, allows entrapping metal ions by complexation for sensing purposes [28, 29]. The complexation behaviour of a molecule supports its application for opto-chemical, mechano-chemical and electrochemical sensing of metal ions after chemical modification. Some of the conducting polymer used in this regards are PPy nano-array [30], PTh film [31], poly (1,5-

[34]

polythiophene-quinoline

(PTQ)-modified

[33],

phytic

3',4'-diamino-2,2';5',2''-terthiophene/ethylenediaminetetraacetic

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acid/polypyrrole

[32],

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diaminonaphthalene)

methyl]-

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(EDTA)[35] and Poly(N,N-ethylene-bis[N-[(3-(pyrrole-1-yl)propyl) carbamoyl)

acid

glycine]) [36] were reported with limited features. In the light of the above development, the

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present work reports a rapid, sensitive, selective and inexpensive potentiometric set up for Cu2+

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ions using Chit-g-PANI based electrode. The structural features and sensing mechanism of Chit-

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g-PANI were also established with the help of infrared spectroscopy (FT-IR), x-ray diffraction (XRD) and scanning electron microscopy (SEM). The other analytical parameters like pH,

2. Experimental

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response time and interference were optimized for determination of Cu2+ ion.

2.1. Chemicals Chit (M.W. 400.00), aniline (99.5%), ammonium persulfate (APS) (99.5%), CuSO4.5H2O (98.8%) were purchased from E-Merk, India and used without further purification. The other used supplementary chemicals were of analytical grades and solutions were prepared with triple distilled water.

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Journal Pre-proof 2.2. Preparation of Chit-g-PANI copolymer and electrode 25 mL Chit solution was prepared by dissolving 0.25 g of Chit in requisite amount of acetic acid and water mixture (25% v/v). Thus, obtained mixture was stirred for 2 hours at room temperature on a magnetic stirrer at 1000 rpm and a homogeneous colorless solution was obtained. In resultant solution, 2.0 mL aniline was added along with constant stirring for 30 minutes. Further, the temperature of the solution was maintained between 0-50C after keeping it in a ice bath.

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Further, 25 mL acidified 0.1M aqueous solution of APS was added in above prepared Chit

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solution drop by drop in 30 minutes along with continued stirring. The stirring was also further

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continued for another 2 hours and finally a greenish black precipitate of Chit-g-PANI was

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obtained. The precipitate was filtered, washed and dried in a hot air oven at 60 oC. It was also

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2.3. Instrumentation

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purified with m-cresol and dimethyl sulfoxide in a soxhlet apparatus before further application.

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Spectroscopic analysis was carried out using a Perkin Elmer (RK-1310) FTIR spectrometer. The

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spectra were recorded in KBr phase with an accumulation of 16 scan with resolution of 2 cm−1 in the range of 4000 to 400 cm−1. The particle size and structure of materials were studied using Bruker-D8-Discover high resolution X-Ray diffractometer employing CuKα (λ=1.5405 Å) radiation at a scanning rate of 2° per min. The surface morphology was also examined by JEOL, JSM-6100 model scanning electron microscope. The microscopic picture was taken after coating of gold on the sample surface by evaporation method. Thermal gravimetric analysis was recorded on Linesis, TGA-1000 model, and thermogravimetric instrument with heating rate 10 O

C per min and 100 mL per minute nitrogen gas flow rate. The electrical conductivity of

electrode was measured by two probe method. The voltages against the prepared film (1cm x 1

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Journal Pre-proof cm) was applied with the help of 32V Aplab regulated DC power supply and respective current was measured using Scientech Digital Multimeter DM-97.

2.4. Physical properties The physio-mechanical properties i.e., solvent content, thickness, swelling and porosity of the

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2.4.1. Solvent content and degree of swelling

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electrode were estimated using earlier reported ASTM methods [37].

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Initially a film of Chit-g-PANI was cut in size of 1.0cm X 1.0 cm with a surgical blade and

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weighed with Sartorius chemical balance having least count 0.01 mg. The film was soaked in a one molar NaCl solution for 24 hours. The film was taken out and blot dried with whatman filter

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paper to remove the surface solvent and weighed immediately. Further, it was dried till it gained

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constant weight in vacuum over silica gel and temperature 50oC. The solvent uptake content (S)

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was calculated using the Eq. (1). S

Ww  Wd  100 Ww

(1)

here, Ww is the weight of wet film; Wd is the weight of dry film. However, the degree of swelling of electrode was estimated by measuring the difference between average thickness of dry film and wet film with NaCl solution for 24 hours.

2.4.2. Porosity

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Journal Pre-proof Porosity (E) was determined as the volume of solvent incorporated in the cavities per unit electrode volume using the Eq. (2). E

Ws  Wd AL w

(2)

where, Ws is soaked weight of electrode, Wd is dry weight of electrode, A is area of electrode, L is

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thickness of film and w is density of water. The measured physical properties of film are given

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in the Table 1.

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2.4.3. Development of electrode, potentiometric cell and Cu2+ detection

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Further, a film of Chit-g-PANI (1.0 cm X 1.0 cm) was casted on ITO coated glass using a 200 ppm suspension of Chit-g-PANI prepared in acetone by spin coating technique at 500 rpm. The

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for Cu2+ detection.

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coated film was thoroughly washed with deionized water and was further used as an electrode

The detection of copper ion sensing was performed on a laboratory designed potentiometric cell (Fig. 1). Cell consists of two cylindrical chambers A and B with radius 2 cm, height 4 cm, capacity of ~50 mL and wall thickness ~0.25 mm. The both chambers were connected with standard ion exchange membrane through connecting hole 1 mm. The chambers work as cathodic and anodic chamber after connecting with potentiometer. In chamber A, an additional opening was designed to add the analyte solution during sensing.

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The sensing was performed by measuring the induced potential between working electrode of Chit-g-PANI and standard reference electrode [38]. The potentiometric sensitivity toward Cu2+ ion was measured after adding the requisite amount of freshly prepared aqueous solution of

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copper ion in different concentration range from 1.0 ppm to 1000 ppm at room temperature

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between 20-25oC. The solution was stirred for 60s to stabilize after addition of analyte solution and then potential were noted after stabilization. The reading was taken in triplet and their mean

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is reported. The interference study was made by measuring the induced potential after addition of

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requisite amount common interference in potentiometric cell. The sensing response was also

3.1. FT-IR

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3. Results and discussion

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recorded after maintain different requisite pH of cell.

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FT-IR spectra of PANI, Chit and Chit-g-PANI are shown in Fig.2. The characteristics bands of PANI were present at 617 cm-1 for γ N-H, 1103 cm-1 of B-NH-B, 1388 cm-1 of C-N stretching for Q-B-Q, 1450 cm-1 of benzenoid, 1635 cm-1 for quinoid [39]. However, the bands for Chit in spectra are present for C-O-C present at 1110 cm-1, for -NHCOCH3 at 1581 cm-1 and for –OH at 3417 cm-1 [40].

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Journal Pre-proof However, IR spectra of co-polymer confirms the presence of characteristic peaks for both Chit and PANI [41, 42]. Further, the comparison of intensity and position characteristic benzenoid and quinoid of pristine PANI with copolymer is indicating the shift of quinoid peak from 1635 to 1643 in Chit-g-PANI. It is due to the interaction between acidic hydrogen of Chit from NHCOCH3 group to quinoid group of PANI. This inter molecular interaction also is supported by shift in N-H bending peak of HNCOCH3 from 1581 to 1565 cm-1, which also indicates the

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restructuring of both Chit and PANI matrix liberate the CO group for interaction with metallic

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ions. Further, a doublet broad band is also present at 3124 and 3417 cm-1 due to the presence of –

-p

NH and -OH in Chit. However, a single peak for NH hydrogen bonding is present at 3432 cm -1 in spectra of PANI. In copolymer these peaks are present at shifted values 3108, 3278 and 3448

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cm-1. These changes in spectral feature confirm the intermolecular interaction between Chit and

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PANI during grafting as illustrated in Fig. 3.

The C-H peak appeared at 2931 cm -1 in PANI is also show change in position at 2915 cm -1 and shape due to grafting with Chit molecule. Thus, shift in peak position of FTIR spectra revealing the formation of Chit-g-PANI a grafted matrix with compact carbon chain and freer amide group. Further, the red shift in peak position in grafted polymer for -NHCOCH3 is indicating loosening of Chit matrix and formation of free -NHCOCH3 group form coordination like a weak ligand with metal ions, which may be suitable for surface interaction with metal group in sensing purpose.

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3.2.

XRD

XRD of pristine PANI, Chit and Chit-g-PANI are shown in Fig. 4 and derived respective structural parameters in Table 2. The characteristic peaks of PANI are present at 2θ=20.4 and

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25.14o due to 100 and 110 planes of PANI [38].

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The characteristic most intense XRD peak of Chit is present at 19.28 for 040 plane [40]. In

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diffraction pattern of Chit-g-PANI is showing peaks for both chit and PANI present at 19.5 (040), 20.7 (100) and 25.82o (013). The peak position of chitin is showing shift after grafting,

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which indicates the compression of matrix due to grafting along with decrease in d values from

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4.39 to 4.31 A0 of PANI and 7.20 A to 6.21 A of Chit.

The compression in of matrix individual components support the generation copolymer with better stability grafting of Chit with PANI in copolymer hybrid matrix.

3.3.

SEM

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Journal Pre-proof SEM photograph of PANI, Chit and Chit-g-PANI are shown in Fig. 5. The SEM image is revealing drastic change in morphology of Chit after grafting with PANI. The image of PANI is indicating homogenous round shape particles. However, micrograph (b) of Chit is showing plate like homogeneous structure.

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However, SEM image (c) of Chit-g-PANI composite is indicating drastic change in morphology

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of Chit. It reveals the formation binary structure, which contains the round shape particles of

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PANI and plates like structure of chitin. The particle size of PANI and chitin gets reduced in

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grafting process in nano range. Thus, the method also explores the possibility for the

Thermogravimetric analysis

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3.4.

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development of one step synthesis of nano hybrid matrix.

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TG curve of PANI and Chit-g-PANI are compared in Fig. 6. The thermogram of PANI is indicating initial weight loss of 2-3% upto to 120 oC due to loss of moisture and adsorbed solvent. Further, a linear diffuse decomposition of PANI proceeded with loss between 200800oC. However, Chit-g-PANI is indicating comparatively sharp weight loss in three steps initially upto 120 oC, second 180-350oC and 350-800oC due to formation of arranged binary matrix.

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The comparison of decomposition pattern of PANI and Chit-g-PANI is indicating ~7 % weight loss between ambient to 1200 C due to the more adsorbed/residual water. It also revealed that the grafted polymer matrix is more hydrophilic than PANI due to formation porous structure consists

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of Chit. The sharper decomposition pattern of Chit-g-PANI hybrid in later step attributed to the

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enhanced arranged intermolecular and intramolecular interaction the copolymer structure than

3.5.

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PANI.

Detection of Cu2+ ion

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The trend of potential variation against the concentration of Cu2+ ion is shown in Fig. 7. The plot

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indicates linear change in potential response against Cu2+ ion concentration in the range of 1 ppm

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copper ions.

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to 1000 ppm. The linear change in potential reveals its suitability for potentiometric sensing of

To understand the basic mechanism, IR spectra of developed electrode was recorded before and after pesticide sensing. The spectra is indicating the appearance of an additional peak at 577 cm-1 due to associative interaction between copper ions and -NHCOCH3 group of Chit molecules. The peak present at 1075 cm-1 in Chit-g-PANI also becomes sharper due to interaction of copper and rearrangement of Chit-g-PANI matrix. This change in spectra due to complexation of Cu ion

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Journal Pre-proof responsible for generation of induced potential. The ion induced interaction between analyte and electrode supports the electronic conduction and basis for ion to electron conversion in proposed electrode. This, complexing nature of the electrode makes it suitable for potentiometric sensing of copper ions and other applications like metal recovery and purification of contaminated water. The slope of potential curve of Chit-g-PANI reveals the sensitivity and sensing response. The observed sensing response of proposed sensor was 2.55 mVppm-1cm-2. The limit of detection

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(LOD) of developed electrode sensor was found to be 13.77 ppm. The observed parameters for

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detection of Cu2+ are compared with different conducting polymer composites material-based

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electrodes in Table 3.

Analytical condition

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3.6.

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The influence of the pH was studied in the range from 3.0 to 8.0. The results are shown in Fig.

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8(a). The curve is indicating high response at 6 pH, this is because of protonation process is more

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favorable in mild acidic condition. The high and low pH may cause oxidative and reductive changes in substrate. Therefore, pH 6.0 is optimal pH for detection of copper in present study. Fig. 8(b) shows that potential of developed electrode continuously increases with time which is maximum in 4 min, which will be the response time of electrode in 240s.

3.7.

Interference study

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Journal Pre-proof The interference effect of possible interfering substances on the determination of Cu2+ was studied at 100 ppm concentration of Cu2+. The electrode response was examined for 10-fold higher quantity of interferent that of concentration of Cu2+ ions. The percentage interference was calculated according to Eq. 3. Interference (%) = Vi  Vu 100

(3)

Vu

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where Vi and Vu are the peak voltage recorded for the mixed analyte (interfering substance +

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Cu2+) and Cu2+ alone, respectively. The results are given in Table 4, which indicates that they

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have negligible interference (~1.15%) on the working electrode.

Application, Repeatability and reliability

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3.8.

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The proposed Chit-g-PANI/ITO coated glass electrode was applied to detect waste water sample

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collected from our laboratory and local ground water. The different samples were spiked with known amount of Cu2+ standard solution (50, 100 ppm solution) and the total concentration of Cu2+ was analyzed using the electrode under the optimal conditions. Table 5 summarizes the results of recovery study, obtained by standard addition method. Consequently, the developed Chit-g-PANI electrode presented a good accuracy for Cu2+determinations in the sample’s matrix studies.



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This sensitivity of electrode was continuously tested with time interval of 48 hours and found stable for 45 days. Only a drop of 2% sensing signal has been observed. It indicates better usability of electrode for a long time. The sensitivity and reproducibility of electrode were also tested and found stable for 10 times. Finally, we concluded that this modified electrode was

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stable and efficient for the quantitative on-site detection of Cu2+ in different wastewater samples.

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4. Conclusion

An electrochemical Cu2+ ion sensor using Chit-g-PANI coated ITO glass electrode and a

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laboratory designed potentiometric cell is reported with advancing the properties of individual

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polymers. The electrochemical sensing response showed a linearity to Cu2+ concentrations

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ranging from 1ppm to 1000 ppm with sensitivity 2.55 mVppm-1cm-2, response time of 240s and long-term stability due to formation of interactive sites and chemical responsiveness due to

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grafting of Chit and PANI. The results indicate the modified electrode has a negligible

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interference, good sensing properties due evolution to free -NHCOCH3 group. The developed sensing device could be a promising option for the portable electrochemical potentiometric sensors for on-site application in different waste and underground water.

Acknowledgement CSK is thankful to Council of Scientific and Industrial Research, Government of India [08/642(0002)/2016-EMR-I] for financial support. Further, the authors are also thankful to Dr. Balaram

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Journal Pre-proof Pani, Principal, BCAS, for maintaining socio-academic environment in the college and the Director, USIC, University of Delhi for providing instrumentation facility.

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sensing, Int. J. Biol. Macromol. 62 (2013) 531-536.

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[24] S.K. Shukla, O. Parlak, S.K. Shukla, S. Mishra, A.P.F. Turner, A. Tiwari, Self-reporting micellar polymer nanostructures for optical urea bio-sensing, Ind. Eng. Chem. Res. 53 (2014)

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https://doi.org/10.1016/j.ijbiomac.2018.11.082. [26] E. Igberase, P. O. Osifo, Application of diethylenetriamine grafted on glyoxal cross-linked chitosan composite for the effective removal of metal ions in batch system, Int. J. Biol. Macromol. 134 (2019) 1145-1155. https://doi.org/10.1016/j.ijbiomac.2019.05.179 [27] B.S. Dakshayini, K.R. Reddy, A. Mishra, N.P. Shetti, S.J. Malode, S. Basu, A.V. Raghu, Role of conducting polymer and metal oxide-based hybrids for applications in ampereometric sensors and biosensors, Microchem. J. 147 (2019) 7-24. https://doi.org/10.1016/j.microc.2019.02.061.

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Journal Pre-proof [28] G. Karthikeyan, N.M. Andal, K. Anbalagan, Adsorption studies of iron (III) onto chitin, J. Chem. Sci. 117 (2005) 663–672. https://doi.org/10.1007/BF02708296. [29] R. Karthik, S. Meenakshi. Synthesis, characterization and Cr (VI) uptake studies of polypyrrole functionalized chitin. Synth. Met. 198 (2014) 181-187. https://doi.org/10.1016/j.synthmet.2014.10.012. [30] M. Lin, X. Hu, Z. Ma, L. Chen, Functionalized polypyrrole nanotube arrays as

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[32] M.C. Pham, M. Oulahyane, M. Mostefai, M.M. Chehimi, Multiple internal reflection FT-IR

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[33] K.S. Yoo, S.B. Woo, J.Y. Jyoung, Trace mercury determination by differential pulse anodic stripping voltammetry using polythiophene-quinoline/glassy carbon modified electrode, Bull. Korean Chem. Soc. 24 (2003) 27–31. https://doi.org/10.5012/bkcs.2003.24.1.027 [34] N. Wang, H. Dai, D. Wang, H. Ma, M. Lin, Determination of copper ions using a phytic acid/polypyrrole nanowires modified glassy carbon electrode, Mater. Sci. Eng. C 76 (2017) 139– 143. https://doi.org/10.1016/j.msec.2017.03.077

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Journal Pre-proof [35] M. Rahman, M.S. Won, Y.B. Shim, Characterization of an EDTA bonded conducting polymer modified electrode: Its application for the simultaneous determination of heavy metal ions, Anal. Chem. 75 (2003) 1123–1129. https://doi.org/10.1021/ac0262917 [36] M. Heitzmann, C. Bucher, J.C. Moutet, E. Pereira, B.L. Rivas, G. Royal, E. Saint-Aman, Complexation of poly(pyrrole-EDTA like) film modified electrodes: Application to metal cations electroanalysis, Electrochim. Acta 52 (2007) 3082–3087.

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Journal Pre-proof

Captions of Figure Fig. 1. Schematic diagram of potentiometric sensing setup. Fig. 2. FT-IR spectra of (a) Chit, (b) PANI and (c) Chit-g-PANI. Fig. 3. Molecular interaction between Chit and PANI. Fig. 4. XRD pattern of (a) PANI, (b) Chit and (c) Chit-g-PANI.

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Fig. 5. SEM photograph of (a) PANI, (b) Chit and (c) Chit-g-PANI.

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Fig. 6. TG curve of (a) PANI and (b) Chit-g-PANI.

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Fig. 7. Plot of potential variation against Cu2+ concentration.

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Fig. 8 (a). Effect of pH on potential and (b). Potential variation with time at 100 ppm of Cu2+.

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Journal Pre-proof List of Tables Table 1 Physical properties of Chit-g-PANI electrode. Chit

PANI

Chit-g-PANI film

1

Water content (%)

32.4%

28.2%

55%

2

Degree of Swelling

24.3%

21.5 %

44 %

3

Porosity

0.0043%

0.0035

0.0065

4

Electrical conductivity

Insulator

4.24 x 10-4 S cm-1

8.19 x 10-5 S cm-1

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Physical properties

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S. N.

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Journal Pre-proof Table 2 XRD derived structural parameters of Chit, PANI and Chit-g-PANI. Sample

1

PANI

2

Chitin

Two Theta

Plane (hkl)

d-value(A0)

20.2o

(100)

4.39

25.2o

(110)

3.53

12.6o

(101)

7.20

of

S.N.

19.2o

(101)

6.21

(040)

4.52

(100)

4.31

25.4o

(110)

3.49

26.6 o

(013)

3.34

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3.40

14.15o

Chitin-g-PANI

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19.6o

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20.6o

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4.61

(013)

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3

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26.2o

(040)

Table 3 Comparison of observed sensing parameter of Cu2+ detection.

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Journal Pre-proof

S.

Electrode material

Analyte

Range

Remark

References

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N.

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Journal Pre-proof 1

Cu2+

PPy nanowire/PA

10 – 60 µg/L

Limit of detection

[34]

(S/N=3) was 3.33 μg·L−1. Response time 300s 2

Cu2+

PPy nanotubes

0.1–30 µM

Limit of detection

[30]

(S/N=3) was 46 nM. 3

Cu2+

HxTiS2 Nanosheet-

25 nM to 5 µM Limit of detection was 0.7 nM.

2 mM - 1.2

PANI/SWCNTs

Pb2+ &

mM Cu2+,

Hg2+

37 mM - 2

Limit of detection was

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Cu2+,

[44]

0.08 μM, 1.65 μM and 0.68 μM respectively.

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EDTA-

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PANI/GCE 4

[43]

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mM Pb2+ & 2 µM - 2 mM

rGO/MgFe2O4

Cu2+

0.02 to 3.3 µM

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5

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Hg2+

PANI-MC

[45]

0.2 nM and sensitivity was 0.0172 µA/nM.

Jo 6

Limit of detection was

Response time was 120 s. Cu2+,

1.00 × 10−8 to

Limit of detection was

Pb2+

1.00 × 10−6 M

6.0×10-9 M & 4.0×10-9

for Cu2+ &

M, respectively

[46]

2.00 × 10−8 to 1.00 × 10−6 M for Pb2+.

27

Journal Pre-proof 7

EDTA-PTh modified

Cu2+,

5.0×10-10 –

Limit of detection was

electrode

Pb2+ &

1.0×10-7 M for

6.0×10-10, 2.0×10-10, and

Hg2+

Cu2+ &

5.0×10-10 M, for Pb2+ ,

7.5×10-10 –

Cu2+& Hg2+ respectively

[35]

1.0×10-7 M for Pb2+ & Hg2+ Cu2+

MWCNT-NS

10-6-10-1 mol/L Limit of detection was >

of

8

[47]

Limit of detection is 13.77 ppm. Response

This work

time is 240 s and sensitivity 2.55 mVppm1

cm-2.

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1-1000 ppm

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Cu2+

Chit-g-PANI

Jo

9

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10-5M

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Journal Pre-proof Table 4 Interference study of developed Cu2+ sensor. Interference (%)

1

K+, Ca2+, Mg2+, Cl-, CO32-, SO42-

No interference

2

Zn2+

1.65

3

Fe2+

0.45

4

Co2+

1.02

5

Cr2+

1.15

6

Pb2+

7

Ni2+

8

Pb2+

9

L-histidine, L-cysteine, L-tyrosine,

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interfering ions

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1.12

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-p

0.87

No interference

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glycine

1.54

lP

S.N.

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Journal Pre-proof Table 5 Recovery analysis of Cu2+ in laboratory waste water and local ground water samples. Sample

Added (ppm)

Recovery (ppm)

Recovery (%)

1

Laboratory waste

50

48.5 ± 0.2

~ 97.2

water

100

101.5 ± 0.1

~ 101.5

Local Ground

50

49.5 ± 0.1

~ 99.0

water

100

98.5 ± 0.3

~ 98.5

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2

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S.N.

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Journal Pre-proof Vinay Kr Singh has performed the experiments of the manuscript Chandra Shekhar Kushwaha has characterised the sample and designed the potentiometric set up.

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S.K. Shukla has conceptualized the idea, synchronised the results and wrote the manuscript.

31

Journal Pre-proof Chitin grafted polyaniline electrode for potentiometric detection of Cu(II) ion. Electrode exhibited response time of 240 s and limit of detection is 13.77 ppm.

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Grafting of PANI with chitin produces interactive sites for coordination with metal ions.

32