Bhuvaneswari2020

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Enhanced photocatalytic activity of ethylenediamine-assisted tin oxide

(SnO

2

) nanorods for methylene blue dye degradation

K. Bhuvaneswari

a

_{, Ba-Son Nguyen}

b

_{, Van-Huy Nguyen}

b

_{, Vu-Quynh Nguyen}

b

_{, Quang-Hung Nguyen}

c

_,

G. Palanisamy

a

, Kundan Sivashanmugan

d

, T. Pazhanivel

a,⇑

a

Smart Materials Interface Laboratory, Department of Physics, Periyar University, Salem 636 011, Tamilnadu, India

b_{Key Laboratory of Advanced Materials for Energy and Environmental Applications, Lac Hong University, Bien Hoa 810000, Viet Nam} c

Institute of Research and Development, Duy Tan University, Da Nang 550000, Viet Nam

d

School of Electrical Engineering and Computer Science, Oregon State University, Corvallis, OR 97331, USA

a r t i c l e i n f o

Article history:

Received 9 June 2020

Received in revised form 13 June 2020 Accepted 16 June 2020

Available online 18 June 2020

Keywords:

Ethylenediamine Tin oxide Nanorod Methylene blue Photocatalytic activity

a b s t r a c t

Ethylenediamine (EDA) assisted tin oxide (SnO2) nanorods were successfully prepared using the solvothermal method. The prepared samples were characterized using X-ray diffraction, Fourier trans-forms infrared analysis, field emission scanning electron microscopy, ultraviolet–visible spectroscopy and photoluminescence spectroscopy analysis. The EDA significantly influences the crystallite size and crystallinity of the prepared SnO2. The optical absorption spectra after the addition of EDA showed the absorption edge red-shifted, which improves the absorption toward the visible-light region. Similarly, the spectral intensity of photoluminescence emission was decreased after the addition of EDA. The pho-tocatalytic activity of the prepared samples was investigated by monitoring the degradation of methylene blue dye under UV–visible light irradiation. The highest photocatalytic activity was attained for the nanorods structured with SnO2, which is higher than that of pristine SnO2due to the effective visible-light absorption and high charge separation of the photogenerated electron-hole pairs.

1. Introduction

To date, photocatalysis, as a green and straightforward approach, has been found effective in environmental treatment

[1–9], especially in degradation of dye pollutants[10–14]. Recently, tin oxide (SnO2) is a widely used metal-oxide semi-conductor due to its mechanical and chemical stabilities, wide bandgap (3.6 eV at bulk state)[15]. Various approaches have been established to synthesize SnO2nanostructures, including thermol-ysis of organometallic precursors, the microwave irradiation method, hydrolysis, sol-gel, and hydrothermal synthesis [16]. Interest has been recently increasing to use SnO2-based nanostruc-tures for degradation of organic pollutants[10–14]. However, the

fast recombination of the photogenerated charge carriers

(electron-hole pairs) of SnO2photocatalysts has limited application for these material systems[17]. To overcome this problem, many studies have focused on alter the phases and morphologies of photocatalysts. Hence, some organic solvents as morphological

templates are proposed to introduce to the preparation

photocatalysts, such as oleic acid [18], ethylenediamine (EDA)

[19], etc. Especially, EDA has been used as a complexing reagent, surfactant, which has a pair of chelating nitrogen atoms in each molecule that serve as bridged ligands for connecting metal atoms (M2+) [19,20]. Moreover, the EDA ligand executes a one-dimensional (1D) infrastructure and local coordination sites for metal sites, systematically establishing these substructures within the crystals via metal bridging functions [21]. Considering the above features, we are interested in using EDA as morphological template to prepare SnO2nanostructures.

Herein, a facile solvothermal method was used to prepare the EDA-assisted SnO2nanorods. The crystal structure, surface mor-phology, and chemical physical properties of the prepared samples were investigated. The photocatalytic activities of the prepared samples were examined by degradation of methylene blue (MB) dye under visible-light irradiation.

2. Experimental section

Typically, 0.152 g of thiourea (CH4N2S) was dissolved in 30 mL of double-distilled water (DDW) or EDA (C2H4(NH2)2) as morpho-logical template for preparing SnO2nanoparticles and EDA-SnO2

⇑ Corresponding author.

E-mail address:pazhanivelt@[email protected](T. Pazhanivel).

Contents lists available atScienceDirect

Materials Letters

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nanorods materials, respectively, under vigorous stirring and ultra-sonicated for 30 min. Then, 0.35 g of tin chloride (SnCl42H2O) was added into the above mixture under continuous stirring for 10 min, and the mixture was transferred to a Teflon-lined stainless steel autoclave with 50-mL capacity and was heated to 150°C for 12 h and then naturally cooled to room temperature. The precipitates were collected using centrifugation and were washed with DDW and ethanol several times to remove residual ions. Finally, the

pro-duct was dried in a vacuum at 60 °C for 3 h for further

characterization.

The morphology and structure of the hydrothermally synthe-sized samples were investigated using field emission scanning electron microscopy (SEM) using Zeiss SUPRA-25. The phase pur-ity, crystallite size, lattice parameters, and crystal structure of the samples were determined by the powder X-ray diffraction (XRD) technique using the Riguku miniflux II X ray diffractometer (10°

2h90°, Cu K

_a

radiation (1.5406 Å)). Fourier transform infrared (FTIR) spectrum was recorded through Bruker model Tensor-27

in the range of 500–4000 cm1_{. Ultraviolet–visible (UV–vis)}

spectroscopy was analysed by a Shimadzu 3600 UV–Vis-NIR

spectrophotometer. Photoluminescence (PL) spectroscopy was carried out at room temperature with a Perkin Elmer LS45 spectrometer.

The MB dye was used to examine the photocatalytic activity that using a light source of a 250 W mercury lamp (400– 700 nm). Typically, 10 mg of the prepared material was dispersed in 100 mL MB dye (20 mg/L) solution. Then, the suspension was stirred in the darkroom for 30 min to attain the adsorption/desorp-tion equilibrium. The degradaadsorption/desorp-tion ability was determined based on the absorption maximum of 664 nm using a Shimadzu UV3000 UV–Vis spectrophotometer.

3. Results and discussion

Fig. 1a-b reveals the FE-SEM images of the SnO2nanoparticles and EDA-SnO2nanorods. The observed morphologies of the pris-tine samples are agglomerated and irregular. The morphology of the SnO2nanoparticles was significantly influenced by the addition of EDA, and the morphology of the sample changed from being

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shapeless to a rod-like shape.Fig. 1c demonstrates the XRD pat-terns, which are agreed with the Joint Committee on Powder Diffraction Standards (JCPDS) no. 72–1147 tetragonal structured

SnO2[22]. The intensities of (0 0 1), (1 0 1), (1 0 2), (1 1 2), and (2 0 1) peaks of SnO2 nanoparticles are much sharper than that of EDA-SnO2nanorods, indicating the influence of EDA in the crys-tal structure.Fig. 1d presents the FTIR spectra of the SnO2 nanopar-ticles and EDA-SnO2nanorods with their major absorption bands tentatively assigned. In typical, the main IR features of SnO2, which are located at 594 and 1153 cm1_{, are assigned to}

m

(Sn–O) and

dOH(Sn–OH, terminal) vibrations, respectively [23,24]. A drastic

loss of transmission in a region of 500–1000 cm1_{, which is}

observed for EDA-SnO2, indicates the incorporation of EDA on SnO2. Acting as a complexing reagent, the EDA is combined with Sn2+_{ion surfaces (i.e., the nitrogen atoms are linearly combined} with Sn2+_{via the lone pair of electrons in each molecule). This}

phe-nomenon is also found in the NH2bending region, in which an

absorption band at 1627 cm1_{is shifted and splitted to 1629 and} 1550 cm1. The broader band located at 3000–3660 cm1is tenta-tively assigned todOH(Sn–OH)[25]or

m

(N–H) vibrations[26]. As expected, the UV–vis indicates a broad absorption of EDA-SnO2 nanorods extending into the visible light region (Fig. 1e). Based

on Tauc’s plot, the bandgap was 3.37 and 2.81 eV for SnO2

nanoparticles and EDA-SnO2 nanorods, respectively.Fig. 1f indi-cates the photoluminescence (PL) spectra under an excitation wavelength of 320 nm. As the PL emission generally originated from the recombination of the photogenerated charge carriers, the pristine sample exhibits the most substantial fluorescence emission peak implying the fastest combination rate of photogen-erated electrons and holes. All samples exhibit a wide-peak in the

Fig. 2.The photocatalytic activity of MB dye (a) MB dye concentration changes vs. irradiation of time (b) pseudo-first-order kinetic vs. irradiation of time under the visible light irradiation.

Fig. 3.Photocatalytic cyclic performance of EDA-SnO2 nanorods over MB dye

degradation.

Table 1

Comparison of degradation efficiency for different SnO2-based material systems.

No. Photocatalyst Dye Reaction conditions Degradation

efficiency (%)

Ref.

1 EDA-SnO2nanorods methylene blue

(MB)

250 W Hg lamp (400–700 nm); catalyst = 100 mg/L; dye = 20 mg/L; t = 90 min

96.3 This study

2 SnO2-ZnO heterojunction MB 125 W high pressure Hg lamp (365 and 313 nm); catalyst = 1 g/L;

dye = 10 mg/L; t = 50 min

99.3 [11]/2012

3 Chitosan-SnO2(50:50)

nanocomposites

Methyl orange (MO)

UV light (365 nm); catalyst = 1 g/L; dye = 5105_{mol/L; t = 100 min} ₉₂ _[14]_/2017

Rhodamine B (RhB)

79

4 Dy2Sn2O7-SnO2

nanocomposites

MO 400 W Hg lamp, UV light; catalyst = 40 mg; dye = 1 mg; t = 50 min 78 [13]/2017

Visible light; catalyst = 40 mg; dye = 1 mg; t = 50 min 62

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range of 350 to 500 nm, which are generally believed to come from the recombination of electrons trapped inside an oxygen vacancy with a hole in the valence band of the SnO2. Similarly, the weaker intensity of EDA-SnO2nanorods designates a lower recombination rate of charge carriers than SnO2nanoparticles. Thus, the separa-tion of charge carriers in the EDA-SnO2nanorods was more

effi-cient than that of SnO2 nanoparticles, leading to possible

enhancing the photocatalytic activity.

Fig. 2a-b illustrates the photocatalytic dye degradation activi-ties under visible-light irradiation. The blank dye was subjected to visible-light irradiation to determine the self-degradation of the MB, which shows negligible degradation. The kinetic character-istics of the MB dye degradation were observed by fitting the first-order kinetic equation as following:

lnðC=C0Þ ¼kt ð1Þ

whereC0is the concentration dye in at the initial time,Cis the con-centration of dye,tis the reaction time (min), andkis the apparent pseudo-first-order kinetic equation. Clearly, EDA-SnO2 nanorods performed significant enhancement the photocatalytic activity. Par-ticularly, the photodegradation efficiency of MB dye over EDA-SnO2 nanorods was 96.3% within 90 min, which was more than two-fold in compared with SnO2 nanoparticles. Furthermore, the recycling experiment results are given inFig. 3. Even after three successive cycles, the EDA-SnO2nanorods displays high catalytic sustainability without loss of efficiency. Although the conditions for conducting experiments are different, it is worth comparing the photodegrada-tion of dye activity over SnO2-based photocatalysts in terms of degradation efficiency in the literature (as shown inTable 1). We find that the performance over EDA-SnO2nanorods is comparable to those seen in the previous studies[11–14].

The proposed photodegradation mechanism of MB dye under UV–visible light irradiation is shown inFig. 4. Under the light irra-diation of photons with energy equal or greater than its energy bandgap, the photogenerated electrons are move from the valence band (VB) to the conduction band (CB) producing oxidative photo-generated valence holes (h+_{) and reductive conduction electrons.} Photogenerated charge carriers (h+_{- e}_{) without recombination}

move to the photocatalyst surface and chemically with the adsor-bent/dye molecules. The above process is continued for many times, and thus the dye was broken then the decolorization took place.

4. Conclusion

The EDA-SnO2rod-like structure was prepared using a simple solvothermal method and characterized using different character-ization methods. The photodegradation efficiency of MB dye over

EDA-SnO2 nanorods was 96.3% within 90 min, which was more

than two-fold in compared with SnO2nanoparticles. The enhance-ment of photocatalytic performance might be attributed to the enhanced visible-light absorption, high stability of photocatalyst, and low charge-carrier recombination where EDA serves as a

cap-ping agent. The EDA-SnO2 nanorods are expected to act as an

excellent visible-light-responsive photocatalytic material to

remove organic dyes.

CRediT authorship contribution statement

K. Bhuvaneswari:Conceptualization, Methodology, Investiga-tion, Writing - original draft.Ba-Son Nguyen:Conceptualization,

Methodology.Van-Huy Nguyen:Conceptualization, Methodology.

Vu-Quynh Nguyen: Conceptualization, Methodology, Writing

-review & editing. Quang-Hung Nguyen: Conceptualization,

Methodology. G. Palanisamy: Conceptualization, Methodology.

Kundan Sivashanmugan: Conceptualization, Methodology.

T. Pazhanivel: Supervision, Conceptualization, Methodology, Investigation, Writing - original draft.

Declaration of Competing Interest

The authors declare that they have no known competing finan-cial interests or personal relationships that could have appeared to influence the work reported in this paper.

References

[1]Y.-T. Wu, Y.-H. Yu, V.-H. Nguyen, K.-T. Lu, J.C.-S. Wu, L.-M. Chang, C.-W. Kuo, J. Hazard. Mater. 262 (2013) 717–725.

[2]J.C.-C. Yu, V.-H. Nguyen, J. Lasek, J.C.S. Wu, Appl. Catal. B 219 (2017) 391–400. [3]K.-T. Lu, V.-H. Nguyen, Y.-H. Yu, C.-C. Yu, J.C.S. Wu, L.-M. Chang, A.Y.-C. Lin,

Chem. Eng. J. 296 (2016) 11–18.

[4]V.-H. Nguyen, S.M. Smith, K. Wantala, P. Kajitvichyanukul, Arab. J. Chem. (2020).

[5]S.S. Lam, V.-H. Nguyen, M.T. Nguyen Dinh, D.Q. Khieu, D.D. La, H.T. Nguyen, D. V.N. Vo, C. Xia, R.S. Varma, M. Shokouhimehr, C.C. Nguyen, Q.V. Le, W. Peng, J. Mater. Chem. A (2020).

(5)

[6]V.-H. Nguyen, B.-S. Nguyen, C.-W. Huang, T.-T. Le, C.C. Nguyen, T.T. Nhi Le, D. Heo, Q.V. Ly, Q.T. Trinh, M. Shokouhimehr, C. Xia, S.S. Lam, D.-V.N. Vo, S.Y. Kim, Q.V. Le, J. Clean. Prod. 270 (2020) 121912.

[7]V.-H. Nguyen, Q.B. Tran, X.C. Nguyen, T.H. Le, T.T.T. Ho, M. Shokouhimehr, D.-V. N. Vo, S.S. Lam, H.P. Nguyen, C.T. Hoang, Q.V. Ly, W. Peng, S.Y. Kim, V.T. Tra, Q. Van Le, Process Saf. Environ. Prot. (2020).

[8]Y.-A. Ho, S.-Y. Wang, W.-H. Chiang, V.-H. Nguyen, J.-L. Chiu, J.C.S. Wu, J. Hazard. Mater. 379 (2019) 120750.

[9] H.-T. Do, L.-A. Phan Thi, N.H. Dao Nguyen, C.-W. Huang, Q.V. Le, V.-H. Nguyen, J. Chem. Technol. Biotechnol. n/a(n/a).

[10] C.M. Vu, V.-H. Nguyen, H.V. Thi, C.W. Jin, D.D. Nguyen, J. Chem. Technol. Biotechnol. n/a(n/a).

[11]M.T. Uddin, Y. Nicolas, C. Olivier, T. Toupance, L. Servant, M.M. Müller, H.-J. Kleebe, J. Ziegler, W. Jaegermann, Inorg. Chem. 51 (14) (2012) 7764–7773. [12]N. Verma, S. Yadav, B. Marí, A. Mittal, J. Jindal, Trans. Indian Ceram. Soc. 77 (1)

(2018) 1–7.

[13]S. Zinatloo-Ajabshir, M.S. Morassaei, M. Salavati- Niasari, J. Colloid Interface Sci. 497 (2017) 298–308.

[14]V.K. Gupta, R. Saravanan, S. Agarwal, F. Gracia, M.M. Khan, J. Qin, R.V. Mangalaraja, J. Mol. Liq. 232 (2017) 423–430.

[15]D. Mohanta, M. Ahmaruzzaman, RSC Adv. 6 (112) (2016) 110996–111015. [16]S. Danwittayakul, M. Jaisai, J. Dutta, Appl. Catal. B 163 (2015) 1–8. [17]G. Elango, S.M. Kumaran, S.S. Kumar, S. Muthuraja, S.M. Roopan, Spectrochim.

Acta A 145 (2015) 176–180.

[18]X. Gou, R. Li, G. Wang, Z. Chen, D. Wexler, Nanotechnology 20 (49) (2009) 495501.

[19]A. Hernández-Gordillo, J.C. Medina, M. Bizarro, R. Zanella, B.M. Monroy, S.E. Rodil, Ceram. Int. 42 (10) (2016) 11866–11875.

[20] H. Li, Y. Hao, H. Lu, L. Liang, Y. Wang, J. Qiu, X. Shi, Y. Wang, J. Yao, Appl. Surf. Sci. 344 (2015) 112–118.

[21]M. Hojamberdiev, G. Zhu, Z.C. Kadirova, J. Han, J. Liang, J. Zhou, X. Wei, P. Liu, Mater. Chem. Phys. 165 (2015) 188–195.

[22]K. Bhuvaneswari, T. Pazhanivel, G. Palanisamy, G. Bharathi, J. Mater. Sci.: Mater. Electron. 31 (9) (2020) 6618–6628.

[23]B. Zhang, Y. Tian, J.X. Zhang, W. Cai, Mater. Lett. 65 (8) (2011) 1204–1206. [24]D. Amalric-Popescu, F. Bozon-Verduraz, Catal. Today 70 (1) (2001) 139–154. [25]F. Gu, S. Fen Wang, C. Feng Song, M. Kai Lü, Y. Xin Qi, G. Jun Zhou, D. Xu, D.