Bull. Mater. Sci., Vol. xx, No. x, Month 2017, pp. xxx–xxx © Indian Academy of Sciences

DOI 10.1007/sxxxx-0xx-1xyz-8

1

Fabrication of MOF-177 for electrochemical detection of toxic Pb2+ and Cd2+

ions

SANGEETHA S1 and KRISHNAMURTHY G*2

1,2 Department of Studies in Chemistry, Bangalore University, Central College Campus, Banga-

lore-560001

1 B.M.S. College of Engineering, Basavangudi, Bangalore, India.

*Author for correspondence (drgkmurthy.bub@gmail.com)

MS received

Abstract: We have studied the electrochemical behavior of room temperature synthesized MOF-177. The MOF-177

sample was characterized by various techniques like FTIR, SEM, EDX, PXRD, NMR and CNHS elemental analy-

sis. The MOF-177 electrode was prepared and electrochemical performance was carried out to explore the electrical

activity of MOF-177. The Cyclic voltammetry studies were made in 0.05 M K4Fe(CN)6 solution and electrochemical

sensing experiments were performed in 0.05 M H2SO4 and pH 7 buffer solution. A significantly increased electron

transfer property has been observed and it has been explored for electrochemical detection of heavy metal ions. The

MOF-177/cp electrode has shown excellent sensitivity towards toxic heavy metal ions such as Pb 2+ and Cd2+ at the

limit of detection (LOD) of 0.004 µM and 0.03 µM respectively.

Keywords: MOF-177, Electrochemical sensor, Heavy metal ions, Chrono-amperometry.

1. Introduction

Here we report the electrochemical behavior of MOF-177

reported by omar M. yaghi [1,2]. MOF-177 was chosen

because they represent a cross-section of attractive prop-

erties such as highly crystalline and ultrahigh porosity

[3]. Although previously published research works [4,5]

have imply and highlighted the gas adsorption property

MOF-177, very few information is available about elec-

tochem cal sensor application of MOF-177. Hence in this

work we explored electrochemical detection of hazardous

heavy metals by MOF-177/cp electrode. The worldwide

environmental related issues have been continuously in-

creasing past from few years. Accumulation of non-

biodegradable, heavy metals such as cadmium and lead,

to the ecosystem through industrial activities increasing

day by day. Kidney damage, brain damage, mental disor-

der damage, behavior problems and development delays

are severe health issues amalgamated with subjection to

high levels of metal ions (e.g., Cd2+, Pb2+, and Hg2+) due

to their propensity to be assemble in the body, noxious

and elimination rate is very low [6,7]. For instance, the

biological half-life of lead in bone is more than 20 years,

while that for cadmium is 10–30 years [8]. Hence detec-

tion and elimination of these metal ions necessary to

maintain healthy environment and human health. Moreo-

ver, utilization of MOFs electrodes has great attention in

various areas of research and development, such as elec-

tro-catalysis, biosensors and electro-analysis [9,16].

Hence we illustrate simple, rapid and room temperature

synthesized MOF-177/cp electrode application towards

low concentration detection of heavy metals.

2. Experimental

2.1 Materials and methods

Zinc nitrate hexa-hydrated (Zn(NO3)2.6H2O) was purchased

from Sigma-Aldrich and benzene tricarboxylic acid was

purchased from spectrochem Pvt. Ltd., Mumbai (India).

Other reagents were purchased from Merck Pvt. Ltd. All

solvents and reagents were used without further purifica-

Manuscript Click here to access/download;Manuscript;Updated wordTemplate bulletin 1.doc

Click here to view linked References

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 61 62 63 64 65

B First Author et al

2

tion. ATRIR spectra were obtained with samples in KBr

for the title complexes on BRUKER-ATR-IR spectrophoto

meter in the range 3500−400 cm−1. Powder X-ray diffrac-

tion (PXRD) data were recorded on a Bruker D8 ADVANC

E X-ray powder diffractometer (CuKα, 1.5418Å). Electroch

emical analyses were made using Autolab potentiostat.

SEM images were collected using a Supra55 field emission

SEM system (Zeiss). The elemental analysis was carried

out on a Inca 2400 Series IIelement analyzer. NMR spectra

were collected by VNMRS-400 “Agilent-NMR”. Thermal

gravimetric analyses were carried out with a SDT Q600

V20,9 Build 20 thermal analyzer from room temperature to

1000°C under a nitrogen atmosphere with a heating rate of

10°C min−1. CHN elemental analysis was done in Flash EA

1112 series CHN thermo finnigan instrument.

2.2. Synthesis of MOF-177

MOF-177 was designed according to the reported method

with some modifications [1]. Benzenetribenzoic acid (0.0

6 g) and Zn(NO3)2.6H2O (0.3 g) were stirred in 50 mL of

DMF for 3 hours. The product formed was washed with

pure ethanol and sample was taken for PXRD analysis,

which showed strong similarities pattern with simulated

MOF-177 (Fig. 1).

2.3. Electrode Preparation and Electrochemical Char-

acterization:

Typical Cyclic voltammetry experiments were carried out

on a classical three-electrode cell configuration with a

platinum auxiliary electrode and MOF-177 electrode as

working electrode (surface area = 1cm x1cm) saturated

calomel as reference electrode using an Autolab

PGSTAT-30 electrochemical workstation [17]. The work-

ing electrodes were constructed by mechanical grinding

of the mixture containing the MOF-177 crystal (40%),

graphite powder (40%) and polytetrafluoroethylene

(20%). The obtained plaster was then overspread on the

surface of the nickel mesh (1cm x1cm) followed by dried

at room temperature for 24 hour [18]. Subsequently, it

was pressed and obtained the final electrode (MOF-

177/cp) material. The electrochemical activity of the elec-

trode was tested in 0.05 M H2SO4 and 0.05 M K4Fe(CN)6

electrolyte separately. Electrochemical sensor perfor-

mance studied in Buffer solution (pH 7) and H2SO4 solu-

tion separately.

3. Result and Discussion

3.1. ATR-IR Analysis

Figure.1 shows the IR spectra of synthesized MOF-177

and analysis show strong similarity with simulated IR

pattern of MOF-177[28]. The appearance of a band at

around 1581 cm'1 to 1367 cm'1 are attributed to mas(COO

) and ms(COO) respectively. The characteristic bands be-

low 1500 cm-1 of the included precursor molecules are

more or less superimposed by the MOF-177 absorptions

[26]

3.2. PXRD and TG Analysis

In order to confirm the product formation, crystalline

nature and diffraction patterns of synthesized MOF-177,

we performed powder XRD. Our powder XRD pattern

results show strong similarities and agreeable with re-

ported MOF-177 (Fig.2a) [1]. The main peaks at 4.7, 6.2,

and 10.1 and are well identified, as shown in the figure.

However, significant weight loss (approximately 45.7 wt

%) was observed at temperatures from 330℃ to 420℃ C

for the oxygen-treated sample [Fig.2b]. Hence MOF-177

synthesized at room temperature is stable till 330℃ and

shows similarities with simulated MOF-177[3]

3.3. Scanning electron microscope (SEM) and Ele-

mental Analysis.

The SEM was used to characterize the morphology of

MOF-177 material. Fig. 3a is the SEM image of the

MOF-177 sample after grinding. The shapes of synthe-

sized particles are look like aggregation of elongated

needles. Fig.3b is Energy dispersion x-ray analysis map-

ping shows percentage composition and exhibit signals of

carbon Kα (1.1 KeV), oxygen Kα (1.25keV) and Zinc Kα

(1.5 keV).

3.4. NMR and CHN analysis

The NMR (Fig. 4a), the absence of peak around 10-12

indicate the deprotonated co-ordination of carboxylic acid

group to the metal. A complex singlet observed at 7.2 to

7.9 ppm is attributed to the aromatic protons. Fig. 4b CH

analysis show the percentage composition of C is 62.43,

H is 5.89 and percentage of Carbon matches with the

composition of reported MOF-177. Trace amount of ni-

trogen might be present in precursor that is 0.08 % found

in analysis.

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 61 62 63 64 65

3

4. Electrochemical studies

4.1. Cyclic voltammetry (CV) experiments:

The MOF-177/cp electrode was used as working elec-

trode in a three electrode electrolytic cell and the redox

behavior of it was examined in 0.05 M K4Fe(CN)6 and

0.05 M H2SO4 electrolyte separately. The electro-activity

surface area can be calculated using the following equa-

tion(1).

(1)

Where Ip is the anodic peak current; C0 is the concentration

of the [Fe(CN)6]3−/4−, DR is the diffusion coefficient

(3.6×10-2 cm2/s), V is scan rate, A is the electrode surface

area, n is number of electron transfer, the electro-active

surface area of the MOF-177/cp electrode can be calculated

to be 0.50x105 cm2, respectively. Fig. 5a and b, display the

electrochemical activity of the MOF-177/cp electrode in

different electrolytes. It shows the redox peaks at around

0.1 to 0.3 V in 0.05M K4Fe(CN)6, and -0.3 to 0.2 V in

0.05M H2SO4 electrolytes (Fig. 5a and 5b) at different scan

rate respectively. There is a raise in peak current with in-

crease in scan rate from 10 mV to 100 mV/s (Fig. 5a) and

which is proportional to square root of the scan rate. This

imply that the electrochemical processes are diffusion con-

trolled [19]. The corresponding log current-log potential

calibration plot in Fig.5a is plainly visible, which indicates

the activity of MOF-177/cp electrode, which corresponds to

a good linear relationship (R2= 0.92). The anodic peak ap-

pears at around 0.25 V and the cathodic peak at about 0.15

V, which could be due to the conversion between different

oxidation states Zn to Zn(II). The counter redox reaction

associated with the electrolyte is as follows equation (2).

(2)

3.3b. Detection of Cd2+ and Pb2+ ions

Fig. 6a and b illustrated the comparison between the cy-

clic voltammetric responses of MOF-177 electrode in two

different electrolytes on addition of Cd2+ solution. While

in the presence of 10 µM Cd2+ a pair of well-defined re-

dox peaks could be observed (Fig.6a) at MOF-177/cp

electrode in 0.05 M H2SO4 electrolyte. The anodic peak

potential was -0.25 V, cathodic peak potential was -0.45

V, peak-to-peak separation ΔEp was equal to 160 mV,

which indicates that the electrode process of Cd2+ in the

acidic electrolyte was quasi-reversible [20]. Much higher

anodic current response was recognized on increasing

concentration of Cd2+. It could be seen that significant

increased anodic peak on lower concentration of 10µM.

On other hand anodic current at -0.7 V increased on suc-

cessive addition of Cd2+ ion and a prominent peak recog-

nized at 30 µM in phosphate buffer (Fig.6b). While peak-

to-peak separation ΔEp was equal to 260 mV, indicating

that the electrode process of Cd2+ in the buffer solution

electrolyte was irreversible. Signal enhancement in 0.05

M H2SO4 found to be 40%, which is greater than that ob-

tained in pH 7 phosphate buffer (15%). Comparison be-

tween two electrolytes, Signal enhancement is greater in

0.05 M H2SO4 electrolyte. Fig 6c and 6d are illustrating

the effects of different electrolytes at MOF-177/cp elec-

trode on successive addition of Pb2+. The result indicates

that, significant increased anodic peak at 0.5 V with an-

odic current 2.8 x 10-3 A in 0.05 M H2SO4 electrolyte, is

more than the anodic current is 2.5x10-4A obtained in

buffer solution at –0.3V. While peak-to-peak separation

ΔEp was equal to 260 mV, which indicates that the elec-

trode process of Pb2+ in the buffer solution electrolyte

was irreversible. Signal enhancement in 0.05 M H2SO4

found to be 76% is greater than that obtained with phos-

phate buffer (pH 7), which is about 56%. Signal en-

hancement was found to be greater in 0.05 M H2SO4

electrolyte. The obtained results show that the parameters

such as current density, response behavior of the elec-

trode and potential shift are influenced by the type of the

electrolyte used. Above result highlight the excellent

electrochemical response observed in 0.05 M H2SO4 for

both Cd2+ and Pb2+ ions. The possible mechanism at ca-

thodic scan and anodic peak current is given below equa-

tions 3, 4 and 5.

(3)

(4)

(5)

The response of the sensor to ions was evaluated by cal-

culating the % signal enhancement (% SE) and LOD us-

ing the following equation (Eq. (6) and (7):

(6)

Where I is MOF-177/cp electrode peak current in the

presence of analyte and I0 is the MOF-177/cp electrode

peak current in the absence of analyte. It was found to be

around 60 to 70%.

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B First Author et al

4

(7)

Where Sa is standard deviation and b is the slope. The

LOD calculated was 0.004 µM for cadmium ion and 0.03

µM for lead ion.

3.3c. Effect of temperature on electrode sensing

To explore the effect of temperature on electrode re-

sponse to the metal ions, we have done the CV at differ-

ent temperature for the buffer solution which contains

10µM of Cd2+ ion and 30µM of Pb2+ ion separately. The

obtained results are illustrated in Fig. 7a and 7b. It could

be seen that, higher sensitivity achieved by electrode on

increasing the temperature [45-50°C]. This should be

ascribed to the following factors, 1. Is might be collusion

of metal ions increases on electrode surface, on increas-

ing the temperature. 2 The kinetic energy of electrons

increase on increasing temperature and this result rise in

current density. But current density has been decreased

[fig. 7c and 7d] on further increases of temperature [70-

85°C] this might be predicted to be increases in resistance

of electrode. In a conductor, which already has a large

number of free electrons flowing through it, the vibration

of the atoms causes many collisions between the free

electrons and the captive electrons. Each collision uses up

some energy from the free electron and is the basic cause

of resistance. The more the atoms jostle around in the

material, the more collisions are caused and hence the

greater the resistance to current flow [27]. Hence, it is

clear that particular temperature notably affect the re-

sponse behavior of the electrode, with respect to the cur-

rent density.

3.3d. Amperometric Sensing of Cd2+ and Pb2 :

The chronoamperometry measurements of MOF-177/cp

electrode were made upon the consecutive supply of Cd2+

and Pb2+ in pH 7 phosphate buffer solution. It can be

shown that the MOF-177/cp electrode responded very

rapidly for the low concentration of the Cd2+ and Pb2+.

The calibration curves of the concentrations of Cd2+ and

Pb2+ ions and current response was shown in figure 8a

and 8b respectively. A linear relationship was noticed of

them in the range of 10 μM to 120 μM.

The corresponding linear equation for Cd2+ and Pb2+ ions

can be expressed as: I (µA) = 0.312CCd(II) (µM) + 7.55 and

I (µA) = 0.00070CPb(II) (µM) + 8.532, with a correlation

coefficient of 0.98 and 0.97 respectively. The detection

limit calculated was 0.004 µM for cadmium ion and 0.03

µM for lead ion at the signal to noise ratio of 3 (S/N=3).

Table. 1 indicate the collation of our proposed Cd[II] and

Pb[II] sensor with several reported electrochemical sensors.

Results revealed that the detection linear range of the detec-

tion limit of Cd2+ and Pb2+ using MOF-177/cp electrode is

comparable with other reported electrochemical sensors.

Therefore, the MOF-177/cp can be used for detection of the

Cd[II] and Pb[II] in real environmental samples.

4. Conclusion

In summary, we have successfully fabricated MOF-177

metal organic framework. The synthesized MOF-177 was

highly crystalline. The excellent sensing nature of MOF-

177 has been unraveled. To the extent of our literature

survey, room temperature synthesized MOF-177/cp elec-

trode rarely reported as electrochemical sensors. The as-

synthesized MOF-177/cp electrode has exhibited well-

behaved redox events and good electrochemical sensor

activity towards Cadmium and Lead ion with LOD in µM

0.004 and 0.03 respectively. Excellent electrochemical

sensing response of MOF-177/cp electrode has been

found in H2SO4 media, even at very low concentrations of

the samples. Hence, MOF-177 is a promising material for

electro-analytical application.

Electronic supplementary material

(www.ias.ac.in/matersci).

Reference

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 61 62 63 64 65

5

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 61 62 63 64 65

B First Author et al

6

[1] David J. Tranchemontagne, Joseph R. Hunt, Omar

Yaghi M. 2008 Tetrahedron 64 8553

[2] Hee K. Chae1, Diana Y. Siberio-Pe´rez1, Jaheon Kim1,

YongBok Go1,Mohamed Eddaoudi1, Adam J. Matzger,

Michael O’Keeffe and Omar Yaghi M. 2004 Nature 427

523

[3] Dipendu Saha, Shuguang Deng 2010 J. Phys. Chem. Lett.

1 73

[4] Chae H.K, Siberio-parez D.Y, Kim J, Go Y, Eddaoudi

M, Matzger A. J, O'Keeffe M and Yaghi, O. M 2004

Nature 427 523

[5] Li Y, Yang R. T 2007 Langmuir 23 12937

[6] George-Octavian Buica, Eleonora Mihaela Ungureanu, L

iviuBirzan, Alexandru C, Razusc,Luisa-Roxana Mandoc

2013 J. Electroanalytical Chemistry 693 67

[7] Goyer R.A, Klaassen C.D, 1996 (Ed.) progress in drug

research 25

[8] Mouchrek VEM, Chierice GO, Marques ALB Quím

Nova 1999 Pharm. Analytica Acta 22 312.

[9] Murray R. W, 1984 (Ed) Elements of Molecular and

Biomolecular Electrochemistry (Dekker M, New York) 3

191

[10] Abruña H.D 1988 Coord Chem Rev 86 135

[11] Murray R.W 1980 Acc Chem Res 13 135

[12] Utner W, Wang J, L’her M and Buck B.P 1998 J.

Pure Appl Chem 70 1301

[13] Arrigan D.W 1994 (Ed) Electroanalysis in Biomedical

and Pharmaceutical Sciences (F. Scholz,USA) 119 1953

[14] Kalcher K, 1990 Electroanalysis 2 419

[15] Furukawa H, Miller M. A and Yaghi M. 2007 J.Mater.

Chem. 17 3197

[16] Sber Alizadeh, Davood Nematollahi, Saber Alizadeh and

Davood Nematollahi 2017 J. Am C hem. Soc. 151 139

[17] Yang Jiao, Jian Pei, Chunshuang Yan, Dahong Chen,

Yongyuan Hu, Gang Chen, 2016 J. Mater. Chem. A 4

13344

[18] Baiing Yuan, Jingchao Zhang, Renchun Zhang, Huazhon

g Shi, Xiuli Guo,Yuanyuan G uo, Xueying Guo,

Shunshou Cai, Daojun Zhang, 2015 Int. J. Electrochem.

Sci 10 4899.

[19] Ruslan N.I, Lim D.C.K, Alang Ahmad S.A, Abdul Aziz

S.F.N, Supian F.L and Yusof N.A 2017 J.

Electroanalytical Chemistry 799 497.

[20] Guojing Fan,Dasun Zhai1and Dongsheng Zou 2016 J.

Electrochem. Sci 11 4362

[21] Mandil A, Pauliukaite R 2012 Anal. Lett. 45 395

[22] George Octavian, Buica, Eleonora, Michaela, Ungu

reanu, Liviu Birzan, Alexandru C. Ra zus Luisa-

Roxana Mandoc 2013 Chemistry and Materials Sci-

ence 75 125

[23] El Mhammedi M.A, Achak M, Najih R, Bakasse M

and Chtaini A 2009 Mater. Chem. Phys. 115 567

[24] TaherAlizadeh,Mohamad RezaGanjali,Parviz

NouroziMashaalahZare Mahmoud Ho seini,Highly

2017 Int. J. Electrochem. Sci 12 5243.

[25] Phuong Khanh Quoc Nguyen,Suzanne K. Lunsford

2013 JSM chemistry 1 1001

[26] Maike Mu¨ller, Oleg I. Lebedevb and Roland A.

Fischer 2008 Journal of Materials Chemistry J. Ma-

ter. Chem. 18 5274

[27] http://www.learnaboutelectronics.org/Resistor

s/resistors_01a.php

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 61 62 63 64 65

7

Tables

Table 1. Comparison of analytical characteristics of MOF-177/cp electrode with some previously reported Cd [II] and

Pb [II] voltammetric sensors.

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 61 62 63 64 65

B First Author et al

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Figures

Figure 1. ATR-IR analysis of synthesized MOF-177 at room temperature

Figure 2. a) PXRD pattern of synthesized MOF-177 b) TG analysis of MOF-177

a b

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9

Figure 3. (a) High-magnification SEM images of as-synthesized MOF-177 after grinding. (b) EDS of MOF-177

with (inset) percentage composition.

Figure 4. (a) NMR analysis of as-synthesized MOF-177 (b) CHNS analysis of MOF-177 with percentage composition

of C, N and H.

a b

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 61 62 63 64 65

B First Author et al

10

.

Figure 5. (a) CV of MOF-177 electrode at different scan rate (υ). Inset: plot of redox peak current versus υ1/2and (b) CV of

MOF-177/cp electrode at different scan rate in 0.05M H2SO4.

Figure 6. Cyclic voltammograms obtained by MOF-177/cp electrode at 50 mV/s for different concentrations of (a) Cadmi-

um ion in 0.05M H2SO4, (b) Cadmium ion in pH 7 phosphate buffer, (c) lead ion in 0.05M H2SO4 and (d) lead ion in pH 7

phosphate buffer.

c d

a b

a b

0.05M H2SO4

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 61 62 63 64 65

11

Figure 7. MOF-177/cp electrode response at different temperature contains, (a) 20µM Cd2+in pH 7 phosphate buffer,

(b) Pb2+in Sodium phosphate buffer. (c) & (d) Effect of temperature on current response on addition of 20µM of Cd[II]

and Pb[II] ion pH 7 phosphate buffer.

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 61 62 63 64 65

B First Author et al

12

Figure. 8.a) Amperometric sensing of Cd[II] upon successive addition at MOF-177/cp electrode at 0.3 V in pH 7.0

phosphate buffer, b) Log-log plot of amperometric response versus the concentration of cadmium ion from 10 µM to

120 µM, c) Amperometric sensing of Pb[II] upon successive addition at MOF-177/cp electrode at 0.3 V in pH 7.0

phosphate buffer and d) Log-log plot of amperometric response versus the concentration of lead ion from 10 µM to

170µM.

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101

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Fabrication of MOF-177 for electrochemical detection of toxic Pb2+ and Cd2+ ions

SANGEETHA S1 and KRISHNAMURTHY G*2

1,2 Department of Studies in Chemistry, Bangalore University, Central College Campus,

Bangalore-560001

*Author for correspondence (drgkmurthy.bub@gmail.com)

1.The information given from the XRD pattern is not sufficient, more details need to

be added in the revised manuscript?

Ans: NMR, IR, CHNS analysis has been done and inserted in the manuscript

2. Many typographical errors need to recheck and to be corrected in the revised

manuscript?

For example: 0.05M H2SO4 to 0.05 M H2SO4 ⁰ C to ⁰ C

Ans: Typographical errors has been rechecked and corrected.

3. In Fig, 3(a) SEM images should be given in originally received images with correct

scale and magnification?

Ans: Received original SEM images given.

4. In Fig. 3(b) EDS spectrum, mention the atomic (%) and wt(%) of MOF-177

quantitatively?

Ans: Atomic (%) and Wt (%) of MOF-177 has been inserted.

5. The overall results and discussion part needs to be improved and to be compared

with previous published reports in the same field?

Ans: Overall results and discussion part improved but not a good number of MOF-

177 has been reported in this field for comparison studies.

Authors' Response to Reviewers' Comments Click here to access/download;Authors' Response to Reviewers'Comments;MOF-177 revision.docx

Fabrication of MOF-177 for electrochemical detection of toxic Pb2+ and Cd2+ ions

SANGEETHA S1 and KRISHNAMURTHY G*2

1,2 Department of Studies in Chemistry, Bangalore University, Central College Campus,

Bangalore-560001

*Author for correspondence (drgkmurthy.bub@gmail.com)

Table

Table 1. Comparison of analytical characteristics of MOF-177/cp electrode with some previously

reported Cd 2+ and Pb 2+ voltammetric sensors.

Table

Bull. Mater. Sci., Vol. xx, No. x, Month 2017, pp. xxx–xxx © Indian Academy of Sciences

DOI 10.1007/sxxxx-0xx-1xyz-8

1

Fabrication of MOF-177 for electrochemical detection of toxic Pb2+ and Cd2+

ions

SANGEETHA S1 and KRISHNAMURTHY G*2

1,2 Department of Studies in Chemistry, Bangalore University, Central College Campus, Banga-

lore-560001

1 B.M.S. College of Engineering, Basavangudi, Bangalore, India.

*Author for correspondence (drgkmurthy.bub@gmail.com)

MS received

Abstract: We have studied the electrochemical behavior of room temperature synthesized MOF-177. The MOF-177

sample was characterized by various techniques like FTIR, SEM, EDX, PXRD, NMR and CNHS elemental analy-

sis. The MOF-177 electrode was prepared and electrochemical performance was carried out to explore the electrical

activity of MOF-177. The Cyclic voltammetry studies were made in 0.05 M K4Fe(CN)6 solution and electrochemical

sensing experiments were performed in 0.05 M H2SO4 and pH 7 buffer solution. A significantly increased electron

transfer property has been observed and it has been explored for electrochemical detection of heavy metal ions. The

MOF-177/cp electrode has shown excellent sensitivity towards toxic heavy metal ions such as Pb 2+ and Cd2+ at the

limit of detection (LOD) of 0.004 µM and 0.03 µM respectively.

Keywords: MOF-177, Electrochemical sensor, Heavy metal ions, Chrono-amperometry.

1. Introduction

Here we report the electrochemical behavior of MOF-177

reported by omar M. yaghi [1,2]. MOF-177 was chosen

because they represent a cross-section of attractive prop-

erties such as highly crystalline and ultrahigh porosity

[3]. Although previously published research works [4,5]

have imply and highlighted the gas adsorption property

MOF-177, very few information is available about elec-

tochem cal sensor application of MOF-177. Hence in this

work we explored electrochemical detection of hazardous

heavy metals by MOF-177/cp electrode. The worldwide

environmental related issues have been continuously in-

creasing past from few years. Accumulation of non-

biodegradable, heavy metals such as cadmium and lead,

to the ecosystem through industrial activities increasing

day by day. Kidney damage, brain damage, mental disor-

der damage, behavior problems and development delays

are severe health issues amalgamated with subjection to

high levels of metal ions (e.g., Cd2+, Pb2+, and Hg2+) due

to their propensity to be assemble in the body, noxious

and elimination rate is very low [6,7]. For instance, the

biological half-life of lead in bone is more than 20 years,

while that for cadmium is 10–30 years [8]. Hence detec-

tion and elimination of these metal ions necessary to

maintain healthy environment and human health. Moreo-

ver, utilization of MOFs electrodes has great attention in

various areas of research and development, such as elec-

tro-catalysis, biosensors and electro-analysis [9,16].

Hence we illustrate simple, rapid and room temperature

synthesized MOF-177/cp electrode application towards

low concentration detection of heavy metals.

2. Experimental

2.1 Materials and methods

Zinc nitrate hexa-hydrated (Zn(NO3)2.6H2O) was purchased

from Sigma-Aldrich and benzene tricarboxylic acid was

purchased from spectrochem Pvt. Ltd., Mumbai (India).

Other reagents were purchased from Merck Pvt. Ltd. All

solvents and reagents were used without further purifica-

Manuscript Click here to access/download;Manuscript;Updated wordTemplate bulletin 1.doc

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Manuscript Click here to access/download;Manuscript;Updated wordTemplate bulletin 1.doc

Click here to view linked References

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B First Author et al

2

tion. ATRIR spectra were obtained with samples in KBr

for the title complexes on BRUKER-ATR-IR spectrophoto

meter in the range 3500−400 cm−1. Powder X-ray diffrac-

tion (PXRD) data were recorded on a Bruker D8 ADVANC

E X-ray powder diffractometer (CuKα, 1.5418Å). Electroch

emical analyses were made using Autolab potentiostat.

SEM images were collected using a Supra55 field emission

SEM system (Zeiss). The elemental analysis was carried

out on a Inca 2400 Series IIelement analyzer. NMR spectra

were collected by VNMRS-400 “Agilent-NMR”. Thermal

gravimetric analyses were carried out with a SDT Q600

V20,9 Build 20 thermal analyzer from room temperature to

1000°C under a nitrogen atmosphere with a heating rate of

10°C min−1. CHN elemental analysis was done in Flash EA

1112 series CHN thermo finnigan instrument.

2.2. Synthesis of MOF-177

MOF-177 was designed according to the reported method

with some modifications [1]. Benzenetribenzoic acid (0.0

6 g) and Zn(NO3)2.6H2O (0.3 g) were stirred in 50 mL of

DMF for 3 hours. The product formed was washed with

pure ethanol and sample was taken for PXRD analysis,

which showed strong similarities pattern with simulated

MOF-177 (Fig. 1).

2.3. Electrode Preparation and Electrochemical Char-

acterization:

Typical Cyclic voltammetry experiments were carried out

on a classical three-electrode cell configuration with a

platinum auxiliary electrode and MOF-177 electrode as

working electrode (surface area = 1cm x1cm) saturated

calomel as reference electrode using an Autolab

PGSTAT-30 electrochemical workstation [17]. The work-

ing electrodes were constructed by mechanical grinding

of the mixture containing the MOF-177 crystal (40%),

graphite powder (40%) and polytetrafluoroethylene

(20%). The obtained plaster was then overspread on the

surface of the nickel mesh (1cm x1cm) followed by dried

at room temperature for 24 hour [18]. Subsequently, it

was pressed and obtained the final electrode (MOF-

177/cp) material. The electrochemical activity of the elec-

trode was tested in 0.05 M H2SO4 and 0.05 M K4Fe(CN)6

electrolyte separately. Electrochemical sensor perfor-

mance studied in Buffer solution (pH 7) and H2SO4 solu-

tion separately.

3. Result and Discussion

3.1. ATR-IR Analysis

Figure.1 shows the IR spectra of synthesized MOF-177

and analysis show strong similarity with simulated IR

pattern of MOF-177[28]. The appearance of a band at

around 1581 cm'1 to 1367 cm'1 are attributed to mas(COO

) and ms(COO) respectively. The characteristic bands be-

low 1500 cm-1 of the included precursor molecules are

more or less superimposed by the MOF-177 absorptions

[26]

3.2. PXRD and TG Analysis

In order to confirm the product formation, crystalline

nature and diffraction patterns of synthesized MOF-177,

we performed powder XRD. Our powder XRD pattern

results show strong similarities and agreeable with re-

ported MOF-177 (Fig.2a) [1]. The main peaks at 4.7, 6.2,

and 10.1 and are well identified, as shown in the figure.

However, significant weight loss (approximately 45.7 wt

%) was observed at temperatures from 330℃ to 420℃ C

for the oxygen-treated sample [Fig.2b]. Hence MOF-177

synthesized at room temperature is stable till 330℃ and

shows similarities with simulated MOF-177[3]

3.3. Scanning electron microscope (SEM) and Ele-

mental Analysis.

The SEM was used to characterize the morphology of

MOF-177 material. Fig. 3a is the SEM image of the

MOF-177 sample after grinding. The shapes of synthe-

sized particles are look like aggregation of elongated

needles. Fig.3b is Energy dispersion x-ray analysis map-

ping shows percentage composition and exhibit signals of

carbon Kα (1.1 KeV), oxygen Kα (1.25keV) and Zinc Kα

(1.5 keV).

3.4. NMR and CHN analysis

The NMR (Fig. 4a), the absence of peak around 10-12

indicate the deprotonated co-ordination of carboxylic acid

group to the metal. A complex singlet observed at 7.2 to

7.9 ppm is attributed to the aromatic protons. Fig. 4b CH

analysis show the percentage composition of C is 62.43,

H is 5.89 and percentage of Carbon matches with the

composition of reported MOF-177. Trace amount of ni-

trogen might be present in precursor that is 0.08 % found

in analysis.

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3

4. Electrochemical studies

4.1. Cyclic voltammetry (CV) experiments:

The MOF-177/cp electrode was used as working elec-

trode in a three electrode electrolytic cell and the redox

behavior of it was examined in 0.05 M K4Fe(CN)6 and

0.05 M H2SO4 electrolyte separately. The electro-activity

surface area can be calculated using the following equa-

tion(1).

(1)

Where Ip is the anodic peak current; C0 is the concentration

of the [Fe(CN)6]3−/4−, DR is the diffusion coefficient

(3.6×10-2 cm2/s), V is scan rate, A is the electrode surface

area, n is number of electron transfer, the electro-active

surface area of the MOF-177/cp electrode can be calculated

to be 0.50x105 cm2, respectively. Fig. 5a and b, display the

electrochemical activity of the MOF-177/cp electrode in

different electrolytes. It shows the redox peaks at around

0.1 to 0.3 V in 0.05M K4Fe(CN)6, and -0.3 to 0.2 V in

0.05M H2SO4 electrolytes (Fig. 5a and 5b) at different scan

rate respectively. There is a raise in peak current with in-

crease in scan rate from 10 mV to 100 mV/s (Fig. 5a) and

which is proportional to square root of the scan rate. This

imply that the electrochemical processes are diffusion con-

trolled [19]. The corresponding log current-log potential

calibration plot in Fig.5a is plainly visible, which indicates

the activity of MOF-177/cp electrode, which corresponds to

a good linear relationship (R2= 0.92). The anodic peak ap-

pears at around 0.25 V and the cathodic peak at about 0.15

V, which could be due to the conversion between different

oxidation states Zn to Zn(II). The counter redox reaction

associated with the electrolyte is as follows equation (2).

(2)

3.3b. Detection of Cd2+ and Pb2+ ions

Fig. 6a and b illustrated the comparison between the cy-

clic voltammetric responses of MOF-177 electrode in two

different electrolytes on addition of Cd2+ solution. While

in the presence of 10 µM Cd2+ a pair of well-defined re-

dox peaks could be observed (Fig.6a) at MOF-177/cp

electrode in 0.05 M H2SO4 electrolyte. The anodic peak

potential was -0.25 V, cathodic peak potential was -0.45

V, peak-to-peak separation ΔEp was equal to 160 mV,

which indicates that the electrode process of Cd2+ in the

acidic electrolyte was quasi-reversible [20]. Much higher

anodic current response was recognized on increasing

concentration of Cd2+. It could be seen that significant

increased anodic peak on lower concentration of 10µM.

On other hand anodic current at -0.7 V increased on suc-

cessive addition of Cd2+ ion and a prominent peak recog-

nized at 30 µM in phosphate buffer (Fig.6b). While peak-

to-peak separation ΔEp was equal to 260 mV, indicating

that the electrode process of Cd2+ in the buffer solution

electrolyte was irreversible. Signal enhancement in 0.05

M H2SO4 found to be 40%, which is greater than that ob-

tained in pH 7 phosphate buffer (15%). Comparison be-

tween two electrolytes, Signal enhancement is greater in

0.05 M H2SO4 electrolyte. Fig 6c and 6d are illustrating

the effects of different electrolytes at MOF-177/cp elec-

trode on successive addition of Pb2+. The result indicates

that, significant increased anodic peak at 0.5 V with an-

odic current 2.8 x 10-3 A in 0.05 M H2SO4 electrolyte, is

more than the anodic current is 2.5x10-4A obtained in

buffer solution at –0.3V. While peak-to-peak separation

ΔEp was equal to 260 mV, which indicates that the elec-

trode process of Pb2+ in the buffer solution electrolyte

was irreversible. Signal enhancement in 0.05 M H2SO4

found to be 76% is greater than that obtained with phos-

phate buffer (pH 7), which is about 56%. Signal en-

hancement was found to be greater in 0.05 M H2SO4

electrolyte. The obtained results show that the parameters

such as current density, response behavior of the elec-

trode and potential shift are influenced by the type of the

electrolyte used. Above result highlight the excellent

electrochemical response observed in 0.05 M H2SO4 for

both Cd2+ and Pb2+ ions. The possible mechanism at ca-

thodic scan and anodic peak current is given below equa-

tions 3, 4 and 5.

(3)

(4)

(5)

The response of the sensor to ions was evaluated by cal-

culating the % signal enhancement (% SE) and LOD us-

ing the following equation (Eq. (6) and (7):

(6)

Where I is MOF-177/cp electrode peak current in the

presence of analyte and I0 is the MOF-177/cp electrode

peak current in the absence of analyte. It was found to be

around 60 to 70%.

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 61 62 63 64 65

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B First Author et al

4

(7)

Where Sa is standard deviation and b is the slope. The

LOD calculated was 0.004 µM for cadmium ion and 0.03

µM for lead ion.

3.3c. Effect of temperature on electrode sensing

To explore the effect of temperature on electrode re-

sponse to the metal ions, we have done the CV at differ-

ent temperature for the buffer solution which contains

10µM of Cd2+ ion and 30µM of Pb2+ ion separately. The

obtained results are illustrated in Fig. 7a and 7b. It could

be seen that, higher sensitivity achieved by electrode on

increasing the temperature [45-50°C]. This should be

ascribed to the following factors, 1. Is might be collusion

of metal ions increases on electrode surface, on increas-

ing the temperature. 2 The kinetic energy of electrons

increase on increasing temperature and this result rise in

current density. But current density has been decreased

[fig. 7c and 7d] on further increases of temperature [70-

85°C] this might be predicted to be increases in resistance

of electrode. In a conductor, which already has a large

number of free electrons flowing through it, the vibration

of the atoms causes many collisions between the free

electrons and the captive electrons. Each collision uses up

some energy from the free electron and is the basic cause

of resistance. The more the atoms jostle around in the

material, the more collisions are caused and hence the

greater the resistance to current flow [27]. Hence, it is

clear that particular temperature notably affect the re-

sponse behavior of the electrode, with respect to the cur-

rent density.

3.3d. Amperometric Sensing of Cd2+ and Pb2 :

The chronoamperometry measurements of MOF-177/cp

electrode were made upon the consecutive supply of Cd2+

and Pb2+ in pH 7 phosphate buffer solution. It can be

shown that the MOF-177/cp electrode responded very

rapidly for the low concentration of the Cd2+ and Pb2+.

The calibration curves of the concentrations of Cd2+ and

Pb2+ ions and current response was shown in figure 8a

and 8b respectively. A linear relationship was noticed of

them in the range of 10 μM to 120 μM.

The corresponding linear equation for Cd2+ and Pb2+ ions

can be expressed as: I (µA) = 0.312CCd(II) (µM) + 7.55 and

I (µA) = 0.00070CPb(II) (µM) + 8.532, with a correlation

coefficient of 0.98 and 0.97 respectively. The detection

limit calculated was 0.004 µM for cadmium ion and 0.03

µM for lead ion at the signal to noise ratio of 3 (S/N=3).

Table. 1 indicate the collation of our proposed Cd[II] and

Pb[II] sensor with several reported electrochemical sensors.

Results revealed that the detection linear range of the detec-

tion limit of Cd2+ and Pb2+ using MOF-177/cp electrode is

comparable with other reported electrochemical sensors.

Therefore, the MOF-177/cp can be used for detection of the

Cd[II] and Pb[II] in real environmental samples.

4. Conclusion

In summary, we have successfully fabricated MOF-177

metal organic framework. The synthesized MOF-177 was

highly crystalline. The excellent sensing nature of MOF-

177 has been unraveled. To the extent of our literature

survey, room temperature synthesized MOF-177/cp elec-

trode rarely reported as electrochemical sensors. The as-

synthesized MOF-177/cp electrode has exhibited well-

behaved redox events and good electrochemical sensor

activity towards Cadmium and Lead ion with LOD in µM

0.004 and 0.03 respectively. Excellent electrochemical

sensing response of MOF-177/cp electrode has been

found in H2SO4 media, even at very low concentrations of

the samples. Hence, MOF-177 is a promising material for

electro-analytical application.

Electronic supplementary material

(www.ias.ac.in/matersci).

Reference

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 61 62 63 64 65

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 61 62 63 64 65

5

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 61 62 63 64 65

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 61 62 63 64 65

B First Author et al

6

[1] David J. Tranchemontagne, Joseph R. Hunt, Omar

Yaghi M. 2008 Tetrahedron 64 8553

[2] Hee K. Chae1, Diana Y. Siberio-Pe´rez1, Jaheon Kim1,

YongBok Go1,Mohamed Eddaoudi1, Adam J. Matzger,

Michael O’Keeffe and Omar Yaghi M. 2004 Nature 427

523

[3] Dipendu Saha, Shuguang Deng 2010 J. Phys. Chem. Lett.

1 73

[4] Chae H.K, Siberio-parez D.Y, Kim J, Go Y, Eddaoudi

M, Matzger A. J, O'Keeffe M and Yaghi, O. M 2004

Nature 427 523

[5] Li Y, Yang R. T 2007 Langmuir 23 12937

[6] George-Octavian Buica, Eleonora Mihaela Ungureanu, L

iviuBirzan, Alexandru C, Razusc,Luisa-Roxana Mandoc

2013 J. Electroanalytical Chemistry 693 67

[7] Goyer R.A, Klaassen C.D, 1996 (Ed.) progress in drug

research 25

[8] Mouchrek VEM, Chierice GO, Marques ALB Quím

Nova 1999 Pharm. Analytica Acta 22 312.

[9] Murray R. W, 1984 (Ed) Elements of Molecular and

Biomolecular Electrochemistry (Dekker M, New York) 3

191

[10] Abruña H.D 1988 Coord Chem Rev 86 135

[11] Murray R.W 1980 Acc Chem Res 13 135

[12] Utner W, Wang J, L’her M and Buck B.P 1998 J.

Pure Appl Chem 70 1301

[13] Arrigan D.W 1994 (Ed) Electroanalysis in Biomedical

and Pharmaceutical Sciences (F. Scholz,USA) 119 1953

[14] Kalcher K, 1990 Electroanalysis 2 419

[15] Furukawa H, Miller M. A and Yaghi M. 2007 J.Mater.

Chem. 17 3197

[16] Sber Alizadeh, Davood Nematollahi, Saber Alizadeh and

Davood Nematollahi 2017 J. Am C hem. Soc. 151 139

[17] Yang Jiao, Jian Pei, Chunshuang Yan, Dahong Chen,

Yongyuan Hu, Gang Chen, 2016 J. Mater. Chem. A 4

13344

[18] Baiing Yuan, Jingchao Zhang, Renchun Zhang, Huazhon

g Shi, Xiuli Guo,Yuanyuan G uo, Xueying Guo,

Shunshou Cai, Daojun Zhang, 2015 Int. J. Electrochem.

Sci 10 4899.

[19] Ruslan N.I, Lim D.C.K, Alang Ahmad S.A, Abdul Aziz

S.F.N, Supian F.L and Yusof N.A 2017 J.

Electroanalytical Chemistry 799 497.

[20] Guojing Fan,Dasun Zhai1and Dongsheng Zou 2016 J.

Electrochem. Sci 11 4362

[21] Mandil A, Pauliukaite R 2012 Anal. Lett. 45 395

[22] George Octavian, Buica, Eleonora, Michaela, Ungu

reanu, Liviu Birzan, Alexandru C. Ra zus Luisa-

Roxana Mandoc 2013 Chemistry and Materials Sci-

ence 75 125

[23] El Mhammedi M.A, Achak M, Najih R, Bakasse M

and Chtaini A 2009 Mater. Chem. Phys. 115 567

[24] TaherAlizadeh,Mohamad RezaGanjali,Parviz

NouroziMashaalahZare Mahmoud Ho seini,Highly

2017 Int. J. Electrochem. Sci 12 5243.

[25] Phuong Khanh Quoc Nguyen,Suzanne K. Lunsford

2013 JSM chemistry 1 1001

[26] Maike Mu¨ller, Oleg I. Lebedevb and Roland A.

Fischer 2008 Journal of Materials Chemistry J. Ma-

ter. Chem. 18 5274

[27] http://www.learnaboutelectronics.org/Resistor

s/resistors_01a.php

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7

Tables

Table 1. Comparison of analytical characteristics of MOF-177/cp electrode with some previously reported Cd [II] and

Pb [II] voltammetric sensors.

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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 61 62 63 64 65

B First Author et al

8

Figures

Figure 1. ATR-IR analysis of synthesized MOF-177 at room temperature

Figure 2. a) PXRD pattern of synthesized MOF-177 b) TG analysis of MOF-177

a b

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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 61 62 63 64 65

9

Figure 3. (a) High-magnification SEM images of as-synthesized MOF-177 after grinding. (b) EDS of MOF-177

with (inset) percentage composition.

Figure 4. (a) NMR analysis of as-synthesized MOF-177 (b) CHNS analysis of MOF-177 with percentage composition

of C, N and H.

a b

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B First Author et al

10

.

Figure 5. (a) CV of MOF-177 electrode at different scan rate (υ). Inset: plot of redox peak current versus υ1/2and (b) CV of

MOF-177/cp electrode at different scan rate in 0.05M H2SO4.

Figure 6. Cyclic voltammograms obtained by MOF-177/cp electrode at 50 mV/s for different concentrations of (a) Cadmi-

um ion in 0.05M H2SO4, (b) Cadmium ion in pH 7 phosphate buffer, (c) lead ion in 0.05M H2SO4 and (d) lead ion in pH 7

phosphate buffer.

c d

a b

a b

0.05M H2SO4

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 61 62 63 64 65

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11

Figure 7. MOF-177/cp electrode response at different temperature contains, (a) 20µM Cd2+in pH 7 phosphate buffer,

(b) Pb2+in Sodium phosphate buffer. (c) & (d) Effect of temperature on current response on addition of 20µM of Cd[II]

and Pb[II] ion pH 7 phosphate buffer.

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 61 62 63 64 65

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 61 62 63 64 65

B First Author et al

12

Figure. 8.a) Amperometric sensing of Cd[II] upon successive addition at MOF-177/cp electrode at 0.3 V in pH 7.0

phosphate buffer, b) Log-log plot of amperometric response versus the concentration of cadmium ion from 10 µM to

120 µM, c) Amperometric sensing of Pb[II] upon successive addition at MOF-177/cp electrode at 0.3 V in pH 7.0

phosphate buffer and d) Log-log plot of amperometric response versus the concentration of lead ion from 10 µM to

170µM.

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101

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Fabrication of MOF-177 for electrochemical detection of toxic Pb2+ and Cd2+ ions

SANGEETHA S1 and KRISHNAMURTHY G*2

1,2 Department of Studies in Chemistry, Bangalore University, Central College Campus, Bangalore-

560001

*Author for correspondence (drgkmurthy.bub@gmail.com)

Figures

Figure 1. ATR-IR analysis of synthesized MOF-177 at room temperature

a b

Figure

a b

Figure 2. a) PXRD pattern of synthesized MOF-177 b) TG analysis of MOF-177

Figure 3. (a) High-magnification SEM images of as-synthesized MOF-177 after grinding. (b) EDS of MOF-177

with (inset) percentage composition.

Figure 4. (a) NMR analysis of as-synthesized MOF-177 (b) CHNS analysis of MOF-177 with percentage

composition of C, N and H.

.

Figure 5. (a) CV of MOF-177 electrode at different scan rate (υ). Inset: plot of redox peak current versus υ1/2and (b) CV of

MOF-177/cp electrode at different scan rate in 0.05M H2SO4.

a b

0.05M H2SO4

Figure 6. Cyclic voltammograms obtained by MOF-177/cp electrode at 50 mV/s for different concentrations of (a)

Cadmium ion in 0.05M H2SO4, (b) Cadmium ion in pH 7 phosphate buffer, (c) lead ion in 0.05M H2SO4 and (d) lead

ion in pH 7 phosphate buffer.

c d

a b

Figure 7. MOF-177/cp electrode response at different temperature contains, (a) 20µM Cd2+in pH 7

phosphate buffer, (b) Pb2+in Sodium phosphate buffer. Effect of (c) & (d) temperature on current

response on addition of 20µM of Cd[II] and Pb[II] ion pH 7 phosphate buffer.

Figure. 8.a) Amperometric sensing of Cd[II] upon successive addition at MOF-177/cp electrode at 0.3 V

in pH 7.0 phosphate buffer, b) Log-log plot of amperometric response versus the concentration of

cadmium ion from 10 µM to 120 µM, c) Amperometric sensing of Pb[II] upon successive addition at

MOF-177/cp electrode at 0.3 V in pH 7.0 phosphate buffer and d) Log-log plot of amperometric

response versus the concentration of lead ion from 10 µM to 170µM.

Fabrication of MOF-177 for electrochemical detection of toxic Pb2+ and Cd2+ ions

SANGEETHA S1 and KRISHNAMURTHY G*2

1,2 Department of Studies in Chemistry, Bangalore University, Central College Campus, Bangalore-

560001

*Author for correspondence (drgkmurthy.bub@gmail.com)

Figures

Figure 1. ATR-IR analysis of synthesized MOF-177 at room temperature

a b

FigureManuscript Click here to access/download;Manuscript;Figure.docx

Click here to view linked References

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a b

Figure 2. a) PXRD pattern of synthesized MOF-177 b) TG analysis of MOF-177

Figure 3. (a) High-magnification SEM images of as-synthesized MOF-177 after grinding. (b) EDS of MOF-177

with (inset) percentage composition.

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Figure 4. (a) NMR analysis of as-synthesized MOF-177 (b) CHNS analysis of MOF-177 with percentage

composition of C, N and H.

.

Figure 5. (a) CV of MOF-177 electrode at different scan rate (υ). Inset: plot of redox peak current versus υ1/2and (b) CV of

MOF-177/cp electrode at different scan rate in 0.05M H2SO4.

a b

0.05M H2SO4

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Figure 6. Cyclic voltammograms obtained by MOF-177/cp electrode at 50 mV/s for different concentrations of (a)

Cadmium ion in 0.05M H2SO4, (b) Cadmium ion in pH 7 phosphate buffer, (c) lead ion in 0.05M H2SO4 and (d) lead

ion in pH 7 phosphate buffer.

c d

a b

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Figure 7. MOF-177/cp electrode response at different temperature contains, (a) 20µM Cd2+in pH 7

phosphate buffer, (b) Pb2+in Sodium phosphate buffer. Effect of (c) & (d) temperature on current

response on addition of 20µM of Cd[II] and Pb[II] ion pH 7 phosphate buffer.

Figure. 8.a) Amperometric sensing of Cd[II] upon successive addition at MOF-177/cp electrode at 0.3 V

in pH 7.0 phosphate buffer, b) Log-log plot of amperometric response versus the concentration of

cadmium ion from 10 µM to 120 µM, c) Amperometric sensing of Pb[II] upon successive addition at

MOF-177/cp electrode at 0.3 V in pH 7.0 phosphate buffer and d) Log-log plot of amperometric

response versus the concentration of lead ion from 10 µM to 170µM.

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