Synthesis, characterization and electrochemical performance of cobalt

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Oct 23, 2018 - The hydrated and sintered cobalt fluoride nanoparticles were prepared via simple and environmentally friendly reverse micro-emulsion method ...
Inorganic Chemistry Communications 98 (2018) 132–140

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Short communication

Synthesis, characterization and electrochemical performance of cobalt fluoride nanoparticles by reverse micro-emulsion method

T

Jamshid Khana, Hameed Ullaha, Muhammad Sajjadb, Akbar Alic,d, Khalid Hussain Thebod,e,



a

Department of Chemistry, Hazara University of Mansehra, 21300, Khyber Pakhtunkhwa, Pakistan Department of Physics, Kohat University of Science and Technology, Kohat 26000, Khyber Pakhtunkhwa, Pakistan c CAS State Key Laboratory of Multi-phase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China d University of CAS, Beijing 100049, People's Republic of China e Dr. M. A. Kazi Institute of Chemistry, University of Sindh Jamshoro, Pakistan b

GRAPHICAL ABSTRACT

The hydrated and sintered cobalt fluoride nanoparticles were prepared via simple and environmentally friendly reverse micro-emulsion method. Such nanoparticles show excellent electrochemical performance as cathode material for lithium ion batteries. The sintered CoF2 NPs obtained at ratio 2:2.5 with uniform composition show better electrochemical performances (0.079 mA g−1) as compared to its counterparts.

ARTICLE INFO

ABSTRACT

Keywords: Cobalt fluoride Nanoparticles Micro-emulsion Cyclic voltammetry Electrochemical

In this work, the cobalt fluoride (CoF2) nanoparticles (NPs) were prepared by reverse micro-emulsion method for first time using cetyltrimethylammonium bromide as surfactant and 2-octanol and water as solvents. Two types of hydrated and sintered CoF2 NPs were prepared with different ratio by changing water to surfactant ratio while keeping the temperature constant at 22 °C. The hydrated CoF2 NPs were sintered at 400 °C under inert atmosphere at 5.0 millibar pressure for 3 h in vacuum chamber in order to obtain sintered CoF2 NPs. The particle sizes of the as-prepared NPs were found to be ~20–70 nm. As-prepared hydrated and sintered CoF2 NPs were characterized by Energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, Scanning electron microscopy, UV–Vis spectroscopy, thermogravimetric analysis, and X-ray diffraction. Further, cyclic voltammetry has been used to measure the electrochemical performance of as-prepared NPs and the results show that electrochemical performance i.e. reversibility and cyclic stability of the synthesized NPs are highly improved. The sintered CoF2 NPs (~20–50 nm) obtained at ratio 2:2.5 with uniform composition show better electrochemical performances (0.079 mA g−1) as compared to its counterparts. This study reveals that CoF2 NPs has great potential as cathode material in energy storage devices due to its excellent efficiency, low cost, easy synthesis and high yield.



Corresponding author at: University of CAS, Beijing 100049, People's Republic of China. E-mail address: [email protected] (K.H. Thebo).

https://doi.org/10.1016/j.inoche.2018.10.018 Received 26 September 2018; Received in revised form 21 October 2018; Accepted 22 October 2018 Available online 23 October 2018 1387-7003/ © 2018 Published by Elsevier B.V.

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Table 1 Synthesis of Cobalt fluoride nanoparticles with different ratio of water to surfactant. Sample

CF1 CF2 CF3 CF4

Reagents (a) 1 g (mmol)

(b) 2 g (mmol)

Water/ surfactant

0.582 0.582 0.582 0.582

0.185 0.185 0.185 0.185

4:2.5 2:2 4:5 2:2.5

(2) (2) (2) (2)

(5) (5) (5) (5)

H2O/ CTAB (Wo)

Oil/CTAB (wt/wt) H2O/Oil

Temp (°C)

Time (Min)

Yield (%)

Particle size range by SEM (nm)

Standard deviation

Crystallite size by XRD (nm) for sintered NPs

Crystallite size by XRD (nm) for hydrated NPs

0.625 1.00 1.25 1.25

6/1 6/1 6/1 6/1

22 22 22 22

60 60 60 60

90.12 70.12 80.12 84.12

20–70 20–50 20–60 20–50

9.9 9.1 9.3 9.1

36 27 37 42

32 28 36 38

± ± ± ±

0.3 0.2 0.3 0.3

(a) Cobalt nitrate hexa hydrate and (b) Ammonium Fluoride.

Fig. 1. Structure characterization of cobalt fluoride nanoparticles. a–d surface morphology of hydrated (a, b) and sintered (c, d) CoF2 NPs respectively. e, f XRD Studies of hydrated (e) and sintered (f) CoF2 NPs.

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Fig. 2. FTIR studies of cobalt fluoride nanoparticles with different ratios before and after sintering.

Energy and environment are key issues faced by world in recent days [1–9]. Nanomaterials with controlled microstructure have been considered as good solutions for several problems related to energy and environment [10–16]. The development of metal fluorides nanostructure have potential applications as cathode material in next-generation lithium (Li) batteries due to their interesting properties including high theoretical e.m.f values and capability to transfer more than one electron per formula unit [17]. However, the use of these materials is limited in electronic applications due to their large band gap. Additionally, the reaction product of conversion reaction, lithium fluoride, is highly insulating. This has also limited use of metal fluorides in their macro crystalline state. Badway et al. reported that the electrochemical performances of metal fluorides can be improved when they are prepared in nanocrystalline state dispersed in a conductive carbon matrix [18]. Grey et al. used FeF2-NPs instead of macroscopic LiFeF3 to improve the electrochemical performances of the batteries [19]. Until now, cobalt fluoride NPs have been widely investigated for several applications, however, the less work has been carried out as cathode materials. Guan et al. have studied porous CoF2 spheres with needle-like shape and self-assembled in three-dimensional hierarchical composites which act as good cathode materials for Li- ion battery [20].

Armstrong et al. [21] synthesized CoF2 NPs by super-critical method and achieved very poor cyclic stability after 25 cycles. Teng et al. [22] also prepared carbon added CoF2 NPs which showed a charge capacity of 250 to 450 mA h g−1. To the best of our knowledge, the good cycling stability of CoF2 used as high capacity cathode materials has not been achieved yet. There is serious need to further investigate CoF2 NPs with different parameters and methods which directly influence the electrochemical performance and cyclic stability. These parameters include solvent to surfactant ratio, temperature, time and solvent effect [23]. The electrochemical performances can be further improved by adjusting particle's size which can also be achieved by using different methods available for the preparation of these NPs. Among various preparation methods [24–38], the use of micro-emulsion is an effective route for yielding a wide range of mono disperses NPs of different size and shape [23]. Herein, we have synthesized CoF2 NPs with four different water to surfactant ratios for the first time by reverse micro-emulsion method. Hydrated CoF2 NPs were prepared by changing water to surfactant ratio while keeping the temperature constant at 22 °C. Further, the hydrated CoF2 NPs were sintered at 400 °C under inert atmosphere at 5.0 millibar (MB) pressure for 3 h in vacuum chamber in order to obtain anhydrous

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Fig. 3. UV–Vis spectra of cobalt fluoride nanoparticles (a) before and (b) after sintering.

CoF2 NPs. The electrochemical properties of as-prepared NPs were measured by using cyclic voltammetry. The obtained sintered CoF2 NPs with particle size ~ 20–50 nm show excellent electrochemical performances ~ 0.079 mA g−1 as compared to other hydrated NPs. On the basis of these results, as-synthesized CoF2 NPs can be used as good cathode materials in Li-ion battery/secondary battery. Cetyltrimethylammonium bromide (CTAB), 2-octanol, cobalt nitrate hexahydrate, ammonium fluoride, potassium chloride and de-ionized (DI) water were purchased from Sigma Aldrich & Merck Ltd. respectively. The received chemicals were used for the preparation of CoF2 NPs without any further purification. The CoF2 NPs were synthesized by reverse micro-emulsion technique. In a typical synthesis process, water-in-oil micro-emulsions of identical compositions were prepared in two separate Teflon beakers by stirring together 5.0 g of CTAB, 30.0 g of 2-octanol and 4.0 g of H2O for 1 h. The water-in-oil micro-emulsions were named as micro-emulsion one (μE1) and micro-emulsion two (μE2) based on the facts that the former contained 0.58 g (2.0 mmol) of cobalt nitrate hexa-hydrate [Co (NO3)2.6H2O] and the latter contained 0.18 g (5.0 mmol) of NH4F. After stirring individually for 1 h, the two micro-emulsions were mixed by pouring down very slowly μE1 into μE2. After mixing the two microemulsions, the whole reaction mixture was stirred for 1 h. The light

pink colored precipitates were obtained after centrifuging supernatant at 4000 rpm (rpm) for 30 min. Resulting light pink powder was washed with DI and ethanol followed by further centrifugation at 4000 rpm for 10 min in order to confirm complete removal of surfactant, oil and other contamination(s). The washing process was repeated ten times. The obtained light pink powder was dried at room temperature for 24 h. A series of CoF2 NPs were prepared by changing water to surfactant ratios. The synthesized materials were then vacuum dried under nitrogen at 400 °C for 3 h at 5.0 MB pressure. The pertinent synthesis parameters are summarized in Table 1. Further, 5.0 mg of CoF2 NPs powder was dissolved in 50 ml DI water in 100 ml glass beaker and stirred for 10 min at room temperature. Then 0.1 M solution of KCl solution was added to above solution as supporting electrolyte. The potential window was setup from 0 to 1.6 V. Using three electrode system i.e. carbon glassy electrode (GCE) as working electrode and reference electrode is Ag/AgCl while gold as counter electrode at scan rate of 100 m Volt per second. In similar way, 0.1 Molar KCl solution in DI water was used as blank using carbon glassy electrode as working electrode. CV for both sintered and hydrated CoF2 NPs were recorded. Scanning electron microscopy (SEM) was used to examine the surface morphology of synthesized NPs. Fig. 1a–d clearly shows the surface

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Fig. 4. Tauc plot for band gap measurement of cobalt fluoride nanoparticles (a) before and (b) after sintering.

of hydrated CoF2 NPs and sintered CoF2 NPs. The SEM studies shows cauliflower like morphology for all sintered CoF2 NPs and hydrated CoF2 NPs (Fig. 1a–d). The average size of cauliflower like structure appears to be 2.5 μm. The flower like structure is constructed by arrangement of basic building block into layers in a three dimension structure. Such building blocks are self-assemblies of CoF2 NPs which are arranged in layer form to form this structure. The outer surface of water molecules contains hydrocarbon molecules which entangled with one another and thus layer formation starts. These self-assemblies of water molecules are acting as nano-reactor for the formation of these layers. Such studies suggest that the synthesized CoF2 NPs are uniformly distributed at nano-regime. The average particle size range from 20 to 70 nm (Table 1). The chemical compositions of as-prepared NPs were measured with help of EDX. The presence of Ni, F and O in the prepared samples was confirmed from the EDX analysis (Supplementary Fig. 1). We then used X-ray diffraction (XRD) to characterize the crystallite size and structure of synthesized NPs. The XRD pattern of sintered CoF2 NPs and hydrated CoF2 NPs were shown in Fig. 1e,f for samples ranging from CF1 to CF4. The CoF2 NPs show a clear XRD peak at 26.5° and rest of all peaks are similar to the standard tetragonal crystal structure of

CoF2 NPs indexed (PDF card No 01-072-1179) which showed that the product is single phase & tetragonal in structure for sintered CoF2 NPs, while hydrated CoF2 NPs shows space group P21ab (29) orthorhombic crystal structure (PDF card number 00-025-0243). XRD pattern of hydrated CoF2 NPs showed moisture as indicated from their XRD pattern but after sintering at 400 °C for 3 h all the samples were become dried and gives good crystallinity (Fig. 1e,f). Average particles size of sintered CoF2 NPs and hydrated CoF2 NPs were calculated by using the DebyeScherer equation: D = Kλ/Bcosθ (Table 1). Where D is the crystalline size, K is the Scherer constant, λ is the X-Rays wavelength, β is the FWHM (full width at half maximum) and θ is the Bragg's angle. It also confirmed by EDX analysis (Supplementary Fig. 1). Fourier-transform infrared spectroscopy (FTIR) has been used to measure the chemical composition of CoF2 NPs and confirmation of different functional groups. FTIR studies of the prepared NPs for hydrated (CF1–CF4) and sintered CoF2 (CF1–CF4) NPs are shown in Fig. 2a–d. It is clear from spectrum that the peaks for –OH (water) in range of 3200–3600 disappear in all ratios after sintering which is confirmation of pure anhydride CoF2 NPs. The peaks in the region at 864.24 cm−1, 762.02 cm−1and 625.14 cm−1 are observed due to CeH stretching, CeF stretching and OeH stretching respectively.

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Fig. 5. a–d Thermo-gravimetric analysis of the synthesized hydrated CoF2.4H2O NPs with different ratio i.e. CF-1 (a), CF-2 (b), CF-3 (c) and CF-4 (d) respectively. TGA of sintered CoF2 NPs with different ratio i.e. CF-1 (a), CF-2 (b), CF-3 (c) and CF-4 (d) respectively on the right. Inset (top).

Further, UV–Vis spectroscopy was used to measure the optical properties of both sintered and hydrated CoF2 NPs as well as their electromagnetic radiations interaction in aqueous environment at 25 °C temperature (Fig. 3a–d). The hydrated CoF2 NPs shows maximum absorption at 393 nm in the UV region (Fig. 3). Fig. 4a–d shows the tauc plot for both the synthesized NPs (CF1–CF4) before and after sintering. According to Kubelka-Munk function, the relationship between the absorption coefficient and band gap energy can be described by the equation (αhν)1/2 = A (hν − Eg), in which α, ν, A and Eg are absorption coefficient, light frequency, proportionality constant and band gap, respectively. The plot (αhν)1/2 vs hν as well as the band gap can be evaluated by extrapolating the straight line to the axis intercept. As shown in Fig. 4, the band gap for sintered CoF2 NPs is about 2.69 eV as compared to the hydrated CoF2 NPs which is 2.77 eV. In addition, stability as well as temperature response of CoF2 NPs was measured by thermogravimetric analysis (TGA). Fig. 5a–d shows the TGA plots of all the synthesized NPs (CF1–CF4). Initially decrease in weight was observed at 110 °C which is due to constant and gradual loss of water. Some CoF2 may be converted to cobalt oxide as the experiment was performed in air. The material is converted in to its pure form i.e. CoF2 and its weight reduced to 60% at temperature of 425 °C. At

this temperature hydrated CoF2 is totally converted to CoF2 as indicated from weight calculation = 168.99 × 60.40/100 = 101.56 which is comparable to molecular weight of pure CoF2 as also confirmed from XRD (Fig. 1). While no loss in weight occurs for all sintered CoF2 (CF1–CF4) and straight line graph is obtained up to temperature of 425 °C (Fig. 5 inset). The weight of the sample remains constant indicating that CoF2 NPs is thermally stable. Here, it is suitable to conclude that such NPs have high stability when it became completely dry. Further, differential scanning calorimetry (DSC) analysis was carried out for both CoF2 NPs before and after sintering respectively (Supplementary Figs. 2 and 3). It is clear when temperature increases for NPs, as water is gradually and constantly removed and also heat is evolved, showing exothermic reaction (Supplementary Fig. 3). All water molecules are removed at 110 °C and there is no change of phase occurs up to 500 °C which showing the thermal stability of materials. After sintering NPs as temperature increases, no change in phase occurs up to 500 °C showing that the material is single phase as indicated from XRD graph. Cyclic Voltammetry (CV) was used to investigate the cyclic stability and reversibility of dissolved electrolyte i.e. sintered CoF2 and hydrated CoF2 NPs at scan rate of 100 mVS−1 as shown in Figs. 6a–d and 7a–d.

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Fig. 6. (a–d) Cyclic voltammetry studies of synthesized cobalt fluoride nanoparticles i.e. CF-1 (a), CF-2 (b), CF-3 (c) and CF-4 (d) before sintering respectively. Scan rate: 100 mV s−1.

cathodic current of −0.08 mA g−1 at potential 0.4 V. The anodiccathodic current and potential for CF1 to CF4 before and after sintering as shown in Table 2 and 3 respectively. It is clear from Tables 1 and 2 that the electrochemical performance of sintered samples is highly improved as compared to hydrated NPs. The CoF2 NPs obtained at ratio 2:2.5 (CF4) show better electrochemical performances ~ 0.079 mA g−1 as compared to its counterparts i.e. CF1–CF3. As the water to surfactant ratio changes from CF1–CF4 the electrochemical performance are also varies in accordance showing better cyclic stability and reversibility. The obtained results were better than reported in literature [39–43]. In summary, high performances CoF2 NPs have been synthesized via reverse micro-emulsion method at room temperature. As-prepared flower like CoF2 NPs show single crystalline tetragonal structure and the average crystalline size of 32 nm. Such NPs are highly thermal stable when it is completely dry. The sintered CoF2 NPs (20–50 nm) obtained at ratio 2:2.5 with uniform composition show better electrochemical performances ~ 0.079 mA g−1 as compared to other NPs. These results suggest that the synthesized NPs may be potentially exploited as cathode materials in energy storage devices and Li-ion batteries.

The sintered CoF2 NPs exhibit good cyclic stability and reversibility at the scan rate of 100 mVS−1 and also show better electrochemical performance as compared with hydrated NPs with good oxidation potential (Figs. 6a–d and 7a–d). During electrolysis when potential is applied cobalt ions will start depositing on working electrode i.e. glassy carbon electrode (GCE) and silver ions will combine with fluoride ions forming silver fluoride. Oxidation and reduction potential will occur during forward and reverse scan and current is produced which are shown in the form of cyclic voltagram. CV was performed for both bare GCE and GCE containing 5 mg/50 ml (5 mg CoF2 dissolved in 50 ml DI water) CoF2 NPs in DI water and also 0.1 M KCl is added as supporting electrolyte to this solution. Bare GCE shows no peak in the DI water containing 0.1 M KCl as supporting electrolyte. Co+2 ions from solution are deposited at GCE electrode through electrochemical deposition. Initially as the voltage increase, deposition of Co2 ions also increases, analyte at the surface of the electrode get reduced, showing anodic peak potential. At switching potential, during reverse scan, again the material re-oxidized, showing cathodic peak potential. It shows reduction potential at 1.2 V for the first peak giving anodic current 0.075 mA g−1. While for the subsequent cycles at the same potential value (1.2 V) it gives anodic current 0.075 mA g−1. During reverse scan, it produces

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Fig. 7. (a–d) Cyclic voltammetry studies of synthesized cobalt fluoride nanoparticles i.e. CF-1 (a), CF-2 (b), CF-3 (c) and CF-4 (d) after sintering respectively. Scan rate: 100 mV s−1.

Table 2 Comparison of oxidation-reduction potential and current for cobalt fluoride nanoparticles (CF1–CF4) before sintering. Samples

CF1 CF2 CF3 CF4

Scan rate (mV/Sec)

100 100 100 100

Potential Window

0 V–1.6 V 0 V–1.6 V 0 V–1.6 V 0 V–1.6 V

Oxidation

Reduction

Reference electrode

Potential (V)

Current (mA/g)

Potential (V)

Current (mA/g)

1.0 0.3 1.0 0.5

0.0001 0.0001 0.00001 0.0001

1.0 0.3 1.0 0.5

−0.0004 −0.0001 −0.0004 −0.001

Silver/Silver Silver/Silver Silver/Silver Silver/Silver

Chloride(Ag/AgCl) Chloride(Ag/AgCl) Chloride(Ag/AgCl) Chloride(Ag/AgCl)

Table 3 Comparison of oxidation-reduction potential and current for cobalt fluoride nanoparticles (CF1–CF4) after sintering. Samples

CF1 CF2 CF3 CF4

Scan rate (mV/Sec)

100 100 100 100

Potential window

0 V–1.6 V 0 V–1.6 V 0 V–1.6 V 0 V–1.6 V

Oxidation

Reduction

Reference electrode

Potential (V)

Current (mA/g)

Potential (V)

Current (mA/g)

1.2 1.3 1.3 1.2

0.075 0.061 0.062 0.079

0.3 0.4 0.4 0.4

−0.08 −0.07 −0.08 −0.08

139

Silver/Silver Silver/Silver Silver/Silver Silver/Silver

Chloride(Ag/AgCl) Chloride(Ag/AgCl) Chloride(Ag/AgCl) Chloride(Ag/AgCl)

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Acknowledgement

[17] F. Badway, N. Pereira, F. Cosandey, G.G. Amatucci, Carbon-metal fluoride nanocomposites structure and electrochemistry of FeF3:C, J. Electrochem. Soc. 150 (2003) 1209–1218. [18] N. Yamakawa, M. Jiang, B. Key, C.P. Grey, Identifying the local structures formed during lithiation of the conversion material, iron fluoride, in a li ion battery: a solidstate NMR, X-ray diffraction, and pair distribution function analysis study, J. Am. Chem. Soc. 131 (2009) 10525–10536. [19] Q. Guan, J. Cheng, X. Li, W. Ni, B. Wang, Porous CoF2 spheres synthesized by a onepot solvothermal method as high capacity cathode materials for lithium-ion batteries, Chin. J. Chem. 35 (2017) 48. [20] Q. Guan, J. Cheng, B. Wang, W. Ni, G. Gu, X. Li, L. Huang, G. Yang, F. Nie, Needlelike Co3O4 anchored on the graphene with enhanced electrochemical performance for aqueous supercapacitors, ACS Appl. Mater. Interfaces 6 (2014) 7626–7632. [21] M.J. Armstrong, A. Panneerselvam, C. O'Regan, M.A. Morris, J.D. Holmes, Supercritical-fluid synthesis of FeF2 and CoF2 Li-ion conversion materials, J. Mater. Chem. A 1 (2013) 10667–10676. [22] Y.T. Teng, S.S. Pramana, J. Ding, T. Wu, R. Yazami, Investigation of the conversion mechanism of nanosized CoF2, Electrochim. Acta 107 (2013) 301. [23] A. Jurek, J. Reszczyńska, E. Grabowska, A. Zaleska, Micro-emulsions - An Introduction to Properties and Applications, vol. 229, (2012). [24] M.D. Morse, Clusters of transition-metal atoms, Chem. Rev. 86 (1986) 1049. [25] K. LaiHing, R.G. Wheeler, W.L. Wilson, M.A. Duncan, Photoionization dynamics and abundance patterns in laser vaporized tin and lead clusters, J. Chem. Phys. 87 (1987) 3401. [26] M. Kagawa, M. Kikuchi, R. Ohno, T. Nagae, Preparation of ultrafine MgO by the spray-ICP technique, J. Am. Ceram. Soc. 64 (1981) C7. [27] C. Wang, J.Y. Ying, Sol−Gel synthesis and hydrothermal processing of anatase and rutile titania nanocrystals, Chem. Mater. 11 (1999) 3113–3120. [28] M.Z.C. Hu, E.A. Payzant, C.H. Byers, Sol-Gel and ultrafine particle formation via dielectric tuning of inorganic salt-alcohol-water solutions, J. Colloid Interface Sci. 222 (2000) 20. [29] M. Wu, G. Lin, D. Chen, G. Wang, D. He, S. Feng, R. Xu, Sol-hydrothermal synthesis and hydrothermally structural evolution of nanocrystal titanium dioxide, Chem. Mater. 14 (2002) 1974–1980. [30] Y. Li, Y. Ding, Y. Qian, Y. Zhang, L. Yang, A solvothermal elemental reaction to produce nanocrystalline ZnSe, Inorg. Chem. 37 (1998) 2844–2845. [31] T. Hirai, T. Hirano, I. Komasawa, Preparation of Gd(2)O(3): Eu(3+) and Gd(2)O(2) S: Eu(3+) phosphor fine particles using an emulsion liquid membrane system, J. Colloid Interface Sci. 253 (2002) 62–69. [32] A. Huignard, T. Gacoin, J. Boilot, Synthesis and luminescence properties of colloidal YVO4: Eu phosphors, Chem. Mater. 12 (2000) 1090–1094. [33] C.J. O'Connor, C.T. Seip, E.E. Carpenter, S. Li, V.T. John, Synthesis and reactivity of nanophase ferrites in reverse micellar solutions, Nanostruct. Mater. 12 (1999) 65–70. [34] R.C. Plaza, J. de Vicente, S. Gomez-Lopera, A.V. Delgado, Stability of dispersions of colloidal nickel ferrite spheres, J. Colloid Interface Sci. 242 (2001) 306–313. [35] C.B. Murray, D.J. Norris, M.G. Bawendi, Synthesis and characterization of nearly monodisperse CdE (E = sulfur, selenium, tellurium) semiconductor nanocrystallites, J. Am. Chem. Soc. 115 (1993) 8706–8715. [36] L. Motte, F. Billoudet, M.P. Pileni, Synthesis in situ of nanosize silver sulphide semiconductor particles in reverse micelles, J. Mater. Sci. 31 (1996) 38–42. [37] C.M. Bender, J.M. Burlitch, D. Barber, C. Pollock, Synthesis and fluorescence of neodymium-doped barium fluoride nanoparticles, Chem. Mater. 12 (2000) 1969–1976. [38] G. Agricolae, Bermannus sive de re metallica, Dover Publications NY, 1986. [39] P. Liu, Y. Zhu, X. Gao, Y. Huang, Y. Wang, S. Qin, Y. Zhang, Rational construction of bowl-like MnO2 nanosheets with excellent electrochemical performance for supercapacitor electrodes, Chem. Eng. Sci. 350 (2018) 79–88. [40] X. Bai, W. Li, A. Wei, Q. Chang, L. Zhang, Z. Liu, Preparation and electrochemical performance of F-doped Li4Ti5O12 for use in the lithium-ion batteries, Solid State Ionics 324 (2018) 13–19. [41] Z. Jiang, J. Zhu, Y. Li, Z. He, W. Meng, Y. Jiang, L. Dai, L. Wang, Effect of Sn doping on the electrochemical performance of NaTi2(PO4)3/C composite, Ceram. Int. 44 (2018) 15646–15652. [42] Y.L. Wang, X.Q. Wei, M.B. Li, P.Y. Hou, X.J. Xu, Temperature dependence of Ni3S2 nanostructures with high electrochemical performance, Appl. Surf. Sci. 436 (2018) 42–49. [43] M. Guo, X. Zhang, W. Meng, X. Liu, G. Wang, Z. Bai, Z. Wang, F. Yang, Electrochemical performance and morphological evolution of hollow Sn microspheres, Solid State Ionics 325 (2018) 120–127.

This study is supported by Higher Education Commission of Pakistan and Mr. Khan acknowledges the support from Hazara University of Mansehra, National University of Sciences and Technology (NUST) for research facilities. Appendix A. Supplementary data Supplementary data to this article can be found online at https:// doi.org/10.1016/j.inoche.2018.10.018. References [1] M. Amiri, A. Pardakhti, M. Ahmadi-Zeidabadi, A. Akbari, M. Salavati-Niasari, Magnetic nickel ferrite nanoparticles: green synthesis by Urtica and therapeutic effect of frequency magnetic field on creating cytotoxic response in neural cell lines, Colloids Surf. B: Biointerfaces 172 (2018) 244–253. [2] M. Iqbal, A.A. Thebo, A.H. Shah, A. Iqbal, K.H. Thebo, S. Phulpoto, M.A. Mohsin, Influence of Mn-doping on the photocatalytic and solar cell efficiency of CuO nanowires, Inorg. Chem. Commun. 76 (2017) 71–76. [3] M. Amiri, A. Akbari, M. Ahmadi, A. Pardakhti, M. Salavati-Niasari, Synthesis and in vitro evaluation of a novel magnetic drug delivery system; proecological method for the preparation of CoFe2O4 nanostructures, J. Mol. Liq. 249 (2018) 1151–1160. [4] S.M. Hosseinpour-Mashkani, F. Mohandes, M. Salavati-Niasari, K. VenkateswaraRao, Microwave-assisted synthesis and photovoltaic measurements of CuInS2 nanoparticles prepared by using metal–organic precursors, Mater. Res. Bull. 47 (2012) 3148–3159. [5] E. Elahi, M. Abid, L. Zhang, S. Haq, J. Ghulam, M. Sahito, Agricultural advisory and financial services; farm level access, outreach and impact in a mixed cropping district of Punjab, Pakistan, Land Use Policy 71 (2018) 249–260. [6] M. Amiri, M. Salavati-Niasari, A. Pardakhty, M. Ahmadi, A. Akbari, Caffeine: a novel green precursor for synthesis of magnetic CoFe2O4 nanoparticles and pHsensitive magnetic alginate beads for drug delivery, Mater. Sci. Eng. C 76 (2017) 1085–1093. [7] N. A. Nahyoon, L. Liu, K. Rabe, K. L. Yuan, J. Sun, F. Yang, Significant photocatalytic degradation and electricity generation in the photocatalytic fuel cell (PFC) using novel anodic. [8] M. Amiri, M. Salavati-Niasari, A. Akbari, T. Gholami, Removal of malachite green (a toxic dye) from water by cobalt ferrite silica magnetic nanocomposite: herbal and green sol-gel autocombustion synthesis, Int. J. Hydrog. Energy 42 (2017) 24846–24860. [9] E. Elahi, M. Abid, H. Zhang, C. Weijun, S. Hasson, Domestic water buffaloes: access to surface water, disease prevalence and associated economic losses, Prev. Vet. Med. 154 (2018) 102–112. [10] M. Salavati-Niasari, F. Davar, Z. Fereshteh, Synthesis and characterization of ZnO nanocrystals from thermolysis of new precursor, J. Chem. Eng. 146 (2009) 498–502. [11] K.H. Thebo, X. Qian, Q. Zhang, L. Chen, H.M. Cheng, W. Ren, Highly stable graphene-oxide-based membranes with superior permeability, Nat. Commun. 9 (1486) (2018). [12] M. Salavati-Niasari, F. Davar, M. Mazaheri, Synthesis and characterization of ZnS nanoclusters via hydrothermal processing from [bis(salicylidene)zinc(II)], J. Alloys Compd. 470 (2009) 502–506. [13] M. Amiri, M. Salavati-Niasari, A. Akbari, A magnetic CoFe2O4/SiO2 nanocomposite fabricated by the sol-gel method for electrocatalytic oxidation and determination of L-cysteine, Microchim. Acta 184 (2017) 825–833. [14] K.H. Thebo, X. Qian, Q. Wei, Q. Zhang, H.M. Cheng, W. Ren, Reduced graphene oxide/metal oxide nanoparticles composite membranes for highly efficient molecular separation, J. Mater. Sci. Technol. 34 (2018) 1481–1486. [15] S. Zinatloo-Ajabshir, M. Salavati-Niasari, M. Hamadaniana, Praseodymium oxide nanostructures: novel solvent-less preparation, characterization and investigation of their optical and photocatalytic properties, RSC Adv. 5 (2015) 33792–33800. [16] E. Esmaeili, M. Salavati-Niasari, F. Mohandes, F. Davar, H. Seyghalkar, Modified single-phase hematite nanoparticles via a facile approach for large-scale synthesis, J. Chem. Eng. 170 (2011) 278–285.

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