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Structural and optical properties of Sn doped ZnO-rGO nanostructures using hydrothermal technique
Materials Today: Proceedings xxx (xxxx) xxx
Contents lists available at ScienceDirect
Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr
Structural and optical properties of Sn doped ZnO-rGO nanostructures using hydrothermal technique A. Priyadharsan a, S. Shanavas a, C. Vidya a, J. Kalyana Sundar a, R. Acevedo b, P.M. Anbarasan a,⇑ a b
Department of Physics, Periyar University, Salem 636 011, Tamil Nadu, India Facultad de Ingeniería y Tecnología, Universidad San Sebastián, Bellavista 7, Santiago 8420524, Chile
a r t i c l e
i n f o
Article history: Received 13 April 2019 Received in revised form 13 May 2019 Accepted 22 May 2019 Available online xxxx Keywords: Sn doped ZnO/rGO Nanostructures Optoelectronic Hydrothermal Reduced graphene oxide
a b s t r a c t The structural and the optoelectronic properties of reduced graphene oxide based nanostructures were manageable, creating them favourable for applications in miscellaneous electronic devices. In this present work, Tin doped Zinc oxide/reduced graphene oxide (Sn doped ZnO/rGO) nanostructures were synthesized using a hydrothermal-assisted self-assemble method, and their structural and optical studies were investigated. The microstructural results confirmed the successful decoration of Sn-doped ZnO/ rGO nanostructures. Therefore, these results can promote an excellent candidate for the applications of environmental issues. Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on Emerging Materials and Modeling.
1. Introduction Semiconductor nanomaterials have been fascinating much attention as an effect of their outstanding properties, which are altered from bulk materials [1,2]. As a result of the excellent physical and chemical properties, for instance low toxicity, electrochemical stability, super oxidative capacity and wide band gap, metal oxides are the furthermost appropriate material for the optoelectronic applications [3]. Based on the above facts, ZnO is a renowned abundant inorganic wide bandgap (3.2 eV) with n-type semiconductor and having high excitonic binding energy (60 meV), which is acting a main role in various applications like photocatalytic activity, solar cells, gas sensors, electrochemical capacitors and batteries etc., [3–6]. Furthermore, due to the enormously large exciton binding energy (about 60 meV), the excitons in ZnO were thermally stable at room temperature, thus it has important advantages in optoelectronic applications such as the UV lasing media [7]. Alteration of ZnO assets by impurity incorporation is presently alternate essential issue for potential applications in ultraviolet optoelectronics and spin electronics [8]. Doping in semiconductors with selective metals deals an effective way to amend their electrical, optical, and magnetic properties, which is necessary for their practical application [9]. It is well-known that for a large band ⇑ Corresponding author. E-mail address: [email protected] (P.M. Anbarasan).
gap semiconductor, the addition of impurities regularly convinces dramatic changes in its electrical and optical properties [10]. Besides, nanomaterials consisting of metal particles embedded in an insulating matrix have attracted considerable attention, both for fundamental and applications reasons. More recently, many interesting physical phenomena such as photochromic, magnetic, and optical properties were observed by use of ZnO, WO3, Fe2O3 and SnO2 as functional matrix materials in the preparation of metal doped metal oxide nanostructures [7,11,12]. Subsequently, metal ion doping and metal nanoparticle decoration are alternative choices for changing the electrical and optical properties of ZnO. Sn is among the most interesting metals as dispersed phases because of their remarkable chemical reactivity in solution. It is therefore interesting to understand the nature of this transparent conducting metal oxide during hydrothermal synthesis. As a result, the incorporation of reduced graphene oxide with ZnO leads to improve the properties of nanostructures for the benefit of optoelectronic applications. However, to our knowledge, there is no study concerning the preparation of Sn doped ZnO/rGO nanostructures via the simple hydrothermal technique. 2. Experimental 2.1. Reagents and materials Graphite flakes, zinc acetate dihydrate (Zn(CH3COO)2 2H2O), sodium tungsten (Na2O4W) and sodium hydroxide (NaOH) were
https://doi.org/10.1016/j.matpr.2019.05.440 2214-7853/Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on Emerging Materials and Modeling.
Please cite this article as: A. Priyadharsan, S. Shanavas, C. Vidya et al., Structural and optical properties of Sn doped ZnO-rGO nanostructures using hydrothermal technique, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.05.440
2
A. Priyadharsan et al. / Materials Today: Proceedings xxx (xxxx) xxx
purchased from Sigma-Aldrich Co. Sulfuric acid (H2SO4), hydrochloric acid (HCl), potassium permanganate (KMnO4), sodium nitrate (NaNO3) and hydrogen peroxide (H2O2) were all purchased from Merck Chemicals, India. All the above chemicals were used without further treatment. 2.2. Preparation of the Sn doped ZnO/rGO nanostructures Reduced graphene oxide was prepared by oxidation of graphite, via Hummer’s method. Sn doped ZnO/rGO nanostructures was prepared by a simple hydrothermal method. In a typical synthesis process, 100 mg of rGO was first dispersed in 60 mL of deionized water with sonication for 1 h to obtain clear brown graphene oxide dispersion. Then molar concentration of Sn was doped with the precursor solution as the source of zinc to the above rGO dispersion. Afterwards, each dispersion was transferred into a separate 100 mL Teflon-lined stainless-steel autoclave and heated at 180 °C for 24 h. The obtained precipitate was separated by centrifugation and washed with ethanol and distilled water for several times. The resulting solid was dried in vacuum oven at 60 °C overnight prior to characterization.
3. Results and discussion 3.1. Crystal structures X-ray diffraction (XRD) patterns of pure ZnO and Sn doped ZnOrGO samples are presented in Fig. 1. The presence of sharp peaks in the XRD patterns indicates the good crystalline structure of samples obtained. The pattern of pure ZnO shows the diffraction peaks of crystalline Sn doped ZnO-rGO corresponding to main diffraction planes. These peaks are also show the formation of polycrystalline nature with a hexagonal structure (JCPDS 36-1451). XRD pattern of Sn doped ZnO-rGO shows the characteristic peak of rGO clearly in synthesized nanoparticles that conforms the presence of representative amount of rGO in the Sn doped ZnO-rGO nanoparticles. It is seen that that the obtained Sn doped ZnO-rGO nanoparticle has good crystalline structure. Crystal size can be calculated by using the Scherer formula [13]. The calculated average crystallite sizes of pure ZnO in 36 nm. Similarly, the average crystalline size of Sn doped ZnO-rGO is 40 nm respectively. XRD graphs also show that the intensities of diffraction peaks of ZnO decreased as the dopant of Sn, i.e., ZnO-rGO doping with Sn caused the crystallinity to degenerate. This calculated average crystalline size reveals that there is a decrease in crystalline size at the doping of Sn with ZnO-rGO nanostructures.
Fig. 1. X-ray diffraction patterns of pure ZnO, ZnO-rGO and Sn doped ZnO-rGO nanostructures.
3.2. Functional group analysis Fig. 2 shows the FT-IR spectra recorded for pure ZnO and 3% Sn doped ZnO/rGO nanostructures in the range 4000–400 cm1. The broad peak in the range 3950–3232 cm1 corresponds to the vibrational mode of OAH bond. Also stretching modes of vibrations in asymmetric and symmetric C@O bonds are observed at 1465– 1543 cm1, respectively. The peaks located at 2283 – 2924 cm1 are due to symmetric and asymmetric CAH bonds, respectively. Furthermore, broad absorption peaks centered at around 1373 cm1 is caused by the OAH stretching of the absorbed water re-absorption through the storage of the sample in ambient air. The presence of the ZnO bond is indicated by the absorption peak at 478 cm1 for pure ZnO; similarly, for 3% Sn doped ZnO-rGO sample it is pointed out from absorption peak in the range of 470 cm1. New absorption peaks at 447 cm1, 532 cm1, 617 cm1, 624 cm1, 663 cm1, 408 cm1, 439 cm1 and 470 cm1 appear as Sn concen-
Fig. 2. FT-IR Spectra of pure ZnO, ZnO-rGO and Sn doped ZnO/rGO nanostructures.
tration increases to 3%. A peculiar peak at 1056 cm1 is observed in the 3% Sn concentration was assigned to CAO stretch bond [14]. 3.3. SEM analysis The morphology and microstructure of the Sn doped ZnO/rGO nanoparticles are examined by SEM as illustrated in Fig. 3(a)–(d).
Please cite this article as: A. Priyadharsan, S. Shanavas, C. Vidya et al., Structural and optical properties of Sn doped ZnO-rGO nanostructures using hydrothermal technique, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.05.440
A. Priyadharsan et al. / Materials Today: Proceedings xxx (xxxx) xxx
It can be seen that particles with little aggregation are attached to the rGO sheet, and distribution of Sn particles all over the surfaces of ZnO-rGO particles with a size range of 45–70 nm (Fig. 3(a) and (b)). The thin sheet shows a typical 2D structure with many wrinkles and folds. In most cases, the introduction of rGO has a negligible influence on the morphology of the product. The flexible rGO sheets can be observed clearly on the surface of the spherical aggregates, which indicates the formation of Sn doped ZnO/rGO nanostructures.
3
3.4. Energy-dispersive X-ray spectroscopy (EDS or EDX) The elemental composition in Sn doped ZnO/rGO nanostructures can be confirmed by energy dispersive EDX in Fig. 4(a) and (b). It is one of the variants of X-ray fluorescence spectroscopy which relies on the investigation of a sample through interactions between electromagnetic radiation and matter. EDX analyses in the scanning electron microscopy (FE-SEM) mode have shown the presence of Sn, O, Zn and C elements in the Sn doped ZnO/ rGO nanostructures. The EDS spectrum indicates that the marked
Fig. 3. (a–d) SEM images of as-prepared Sn doped ZnO-rGO Nanostructures.
Fig. 4. (a, b) EDX spectra of the 3% Sn doped ZnO-rGO Nanoparticles.
Please cite this article as: A. Priyadharsan, S. Shanavas, C. Vidya et al., Structural and optical properties of Sn doped ZnO-rGO nanostructures using hydrothermal technique, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.05.440
4
A. Priyadharsan et al. / Materials Today: Proceedings xxx (xxxx) xxx
Fig. 5. (a) UV–Vis diffuse reflectance spectra of pure ZnO, ZnO-rGO and Sn doped ZnO/rGO nanostructures (b) plot of band gap energy of pure ZnO, ZnO-rGO and Sn doped ZnO/rGO nanostructures.
area in Fig. 4a contains 16.17 wt% Sn, 10.11 wt% O, 55.86 wt% Zn, and 17.86 wt% C. The atomic percentage from Fig. 4b found to be 4.38 wt% Sn, 20.33 wt% O, 27.48 wt% Zn, and 47.81 wt% C. 3.5. Uv–visible–diffused reflectance spectroscopy (UV-DRS) The UV–Vis reflectance spectra of the pure ZnO, ZnO-rGO and Sn doped ZnO/rGO nanostructures are shown in Fig. 5(a) and (b). The reflectance values were transformed to absorbance by use of the Kubelka Munk translation, Eq. (1) 2
K ¼ ð1 RÞ =2R
ð1Þ
where K is the reflectance transformed according to Kubelka Munk and R is the reflectance (%). The relationship between (K * hm)1/2 = f (h * m) is shown in Fig. 5(a) and (b). This plot gives band gap energies of 3.2 eV for ZnO, 3.18 eV for ZnO-rGO and 3.15 eV for Sn doped ZnO/rGO nanostructures. It can be noticed that the band gap decreased on nanoparticles. This performance is the result of a slightly increases in the free carrier concentration due to rGO adding and the corresponding descending shift of the Fermi level to less than of the band edge. Therefore, the band gap decrement observed in Sn doped ZnO/rGO nanostructures could be attributed due to its increased size compared with ZnO and optical response of Sn doped ZnO/rGO nanostructures was enhanced in favour of dye sensitized solar cell (DSSC) and photocatalytic applications. 4. Conclusion In the present work, we have successfully synthesized ZnO, ZnO-rGO and Sn doped ZnO/rGO nanostructures using hydrothermal technique. Powder XRD pattern of the samples (rGO, ZnO) matches with the hexagonal structure and the following miller indices were good in agreement. The average particle sizes were found to be around 40 nm and 36 nm for as prepared samples of ZnO and Sn doped ZnO/rGO nanostructures. SEM analysis confirms
that both the as prepared samples are monodispersed spherical shape morphology with uniform distribution. The band gap energy was calculated as 3.2 eV, 3.18 eV, and 3.15 eV for ZnO, ZnO-rGO, Sn doped ZnO/rGO nanostructures by UV–Vis spectra analysis. Overall, these materials could have applications in different fields such as cathode materials in solid oxide fuel cell, gas sensors, photocatalytic activity, antibacterial performance and DSSC in solar cell applications. References [1] I. Khan, K. Saeed, I. Khan, Arab. J. Chem. (2017), https://doi.org/10.1016/j. arabjc.2017.05.011. [2] M.A. El-Sayed, Acc. Chem. Res. 37 (2004) 326–333, https://doi.org/10.1021/ ar020204f. [3] G. Wang, A. Morrin, M. Li, N. Liu, X. Luo, J. Mater. Chem. B 6 (2018) 4173–4190, https://doi.org/10.1039/c8tb00817e. [4] A. Priyadharsan, S. Shanavas, V. Vasanthakumar, B. Balamuralikrishnan, P.M. Anbarasan, Colloids Surf. A Physicochem. Eng. Asp. 559 (2018) 43–53, https:// doi.org/10.1016/j.colsurfa.2018.09.034. [5] J. Ding, Y. Zhou, G. Dong, M. Liu, D. Yu, F. Liu, Prog. Photovoltaics Res. Appl. 26 (2018) 974–980, https://doi.org/10.1002/pip.3044. [6] Y. Wang, X. Xiao, H. Xue, H. Pang, ChemistrySelect 3 (2018) 550–565, https:// doi.org/10.1002/slct.201702780. [7] D. Vanmaekelbergh, L.K. Van Vugt, Nanoscale 3 (2011) 2783–2800, https://doi. org/10.1039/c1nr00013f. [8] Y. Li, X. Zhao, W. Fan, J. Phys. Chem. C. 115 (2011) 3552–3557, https://doi.org/ 10.1021/jp1098816. [9] S. Kasap, C. Koughia, H.E. Ruda, Electron. Photon. Mater. (2017) 1, https://doi. org/10.1007/978-3-319-48933-9_2. [10] M. Koperski, M.R. Molas, A. Arora, K. Nogajewski, A.O. Slobodeniuk, C. Faugeras, M. Potemski, Nanophotonics 6 (2017) 1289–1308, https://doi.org/ 10.1515/nanoph-2016-0165. [11] A. Priyadharsan, V. Vasanthakumar, S. Shanavas, S. Karthikeyan, P.M. Anbarasan, Appl. Surf. Sci. 470 (2019) 114–128, https://doi.org/10.1016/j. apsusc.2018.11.130. [12] S. Shanavas, A. Priyadharsan, I. Gkanas, R. Acevedo, P.M. Anbarasan, J. Ind. Eng. Chem. 72 (2019) 512–528, https://doi.org/10.1016/j.jiec.2019.01.008. [13] G. Grübel, E.V. Shevchenko, I. Mekis, A. Kornowski, A. Robert, H. Borchert, H. Weller, Langmuir 21 (2005) 1931–1936, https://doi.org/10.1021/la0477183. [14] B. Li, T. Liu, Y. Wang, Z. Wang, J. Colloid Interf. Sci. 377 (2012) 114–121, https:// doi.org/10.1016/j.jcis.2012.03.060.
Please cite this article as: A. Priyadharsan, S. Shanavas, C. Vidya et al., Structural and optical properties of Sn doped ZnO-rGO nanostructures using hydrothermal technique, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.05.440
Contents lists available at ScienceDirect
Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr
Structural and optical properties of Sn doped ZnO-rGO nanostructures using hydrothermal technique A. Priyadharsan a, S. Shanavas a, C. Vidya a, J. Kalyana Sundar a, R. Acevedo b, P.M. Anbarasan a,⇑ a b
Department of Physics, Periyar University, Salem 636 011, Tamil Nadu, India Facultad de Ingeniería y Tecnología, Universidad San Sebastián, Bellavista 7, Santiago 8420524, Chile
a r t i c l e
i n f o
Article history: Received 13 April 2019 Received in revised form 13 May 2019 Accepted 22 May 2019 Available online xxxx Keywords: Sn doped ZnO/rGO Nanostructures Optoelectronic Hydrothermal Reduced graphene oxide
a b s t r a c t The structural and the optoelectronic properties of reduced graphene oxide based nanostructures were manageable, creating them favourable for applications in miscellaneous electronic devices. In this present work, Tin doped Zinc oxide/reduced graphene oxide (Sn doped ZnO/rGO) nanostructures were synthesized using a hydrothermal-assisted self-assemble method, and their structural and optical studies were investigated. The microstructural results confirmed the successful decoration of Sn-doped ZnO/ rGO nanostructures. Therefore, these results can promote an excellent candidate for the applications of environmental issues. Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on Emerging Materials and Modeling.
1. Introduction Semiconductor nanomaterials have been fascinating much attention as an effect of their outstanding properties, which are altered from bulk materials [1,2]. As a result of the excellent physical and chemical properties, for instance low toxicity, electrochemical stability, super oxidative capacity and wide band gap, metal oxides are the furthermost appropriate material for the optoelectronic applications [3]. Based on the above facts, ZnO is a renowned abundant inorganic wide bandgap (3.2 eV) with n-type semiconductor and having high excitonic binding energy (60 meV), which is acting a main role in various applications like photocatalytic activity, solar cells, gas sensors, electrochemical capacitors and batteries etc., [3–6]. Furthermore, due to the enormously large exciton binding energy (about 60 meV), the excitons in ZnO were thermally stable at room temperature, thus it has important advantages in optoelectronic applications such as the UV lasing media [7]. Alteration of ZnO assets by impurity incorporation is presently alternate essential issue for potential applications in ultraviolet optoelectronics and spin electronics [8]. Doping in semiconductors with selective metals deals an effective way to amend their electrical, optical, and magnetic properties, which is necessary for their practical application [9]. It is well-known that for a large band ⇑ Corresponding author. E-mail address: [email protected] (P.M. Anbarasan).
gap semiconductor, the addition of impurities regularly convinces dramatic changes in its electrical and optical properties [10]. Besides, nanomaterials consisting of metal particles embedded in an insulating matrix have attracted considerable attention, both for fundamental and applications reasons. More recently, many interesting physical phenomena such as photochromic, magnetic, and optical properties were observed by use of ZnO, WO3, Fe2O3 and SnO2 as functional matrix materials in the preparation of metal doped metal oxide nanostructures [7,11,12]. Subsequently, metal ion doping and metal nanoparticle decoration are alternative choices for changing the electrical and optical properties of ZnO. Sn is among the most interesting metals as dispersed phases because of their remarkable chemical reactivity in solution. It is therefore interesting to understand the nature of this transparent conducting metal oxide during hydrothermal synthesis. As a result, the incorporation of reduced graphene oxide with ZnO leads to improve the properties of nanostructures for the benefit of optoelectronic applications. However, to our knowledge, there is no study concerning the preparation of Sn doped ZnO/rGO nanostructures via the simple hydrothermal technique. 2. Experimental 2.1. Reagents and materials Graphite flakes, zinc acetate dihydrate (Zn(CH3COO)2 2H2O), sodium tungsten (Na2O4W) and sodium hydroxide (NaOH) were
https://doi.org/10.1016/j.matpr.2019.05.440 2214-7853/Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on Emerging Materials and Modeling.
Please cite this article as: A. Priyadharsan, S. Shanavas, C. Vidya et al., Structural and optical properties of Sn doped ZnO-rGO nanostructures using hydrothermal technique, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.05.440
2
A. Priyadharsan et al. / Materials Today: Proceedings xxx (xxxx) xxx
purchased from Sigma-Aldrich Co. Sulfuric acid (H2SO4), hydrochloric acid (HCl), potassium permanganate (KMnO4), sodium nitrate (NaNO3) and hydrogen peroxide (H2O2) were all purchased from Merck Chemicals, India. All the above chemicals were used without further treatment. 2.2. Preparation of the Sn doped ZnO/rGO nanostructures Reduced graphene oxide was prepared by oxidation of graphite, via Hummer’s method. Sn doped ZnO/rGO nanostructures was prepared by a simple hydrothermal method. In a typical synthesis process, 100 mg of rGO was first dispersed in 60 mL of deionized water with sonication for 1 h to obtain clear brown graphene oxide dispersion. Then molar concentration of Sn was doped with the precursor solution as the source of zinc to the above rGO dispersion. Afterwards, each dispersion was transferred into a separate 100 mL Teflon-lined stainless-steel autoclave and heated at 180 °C for 24 h. The obtained precipitate was separated by centrifugation and washed with ethanol and distilled water for several times. The resulting solid was dried in vacuum oven at 60 °C overnight prior to characterization.
3. Results and discussion 3.1. Crystal structures X-ray diffraction (XRD) patterns of pure ZnO and Sn doped ZnOrGO samples are presented in Fig. 1. The presence of sharp peaks in the XRD patterns indicates the good crystalline structure of samples obtained. The pattern of pure ZnO shows the diffraction peaks of crystalline Sn doped ZnO-rGO corresponding to main diffraction planes. These peaks are also show the formation of polycrystalline nature with a hexagonal structure (JCPDS 36-1451). XRD pattern of Sn doped ZnO-rGO shows the characteristic peak of rGO clearly in synthesized nanoparticles that conforms the presence of representative amount of rGO in the Sn doped ZnO-rGO nanoparticles. It is seen that that the obtained Sn doped ZnO-rGO nanoparticle has good crystalline structure. Crystal size can be calculated by using the Scherer formula [13]. The calculated average crystallite sizes of pure ZnO in 36 nm. Similarly, the average crystalline size of Sn doped ZnO-rGO is 40 nm respectively. XRD graphs also show that the intensities of diffraction peaks of ZnO decreased as the dopant of Sn, i.e., ZnO-rGO doping with Sn caused the crystallinity to degenerate. This calculated average crystalline size reveals that there is a decrease in crystalline size at the doping of Sn with ZnO-rGO nanostructures.
Fig. 1. X-ray diffraction patterns of pure ZnO, ZnO-rGO and Sn doped ZnO-rGO nanostructures.
3.2. Functional group analysis Fig. 2 shows the FT-IR spectra recorded for pure ZnO and 3% Sn doped ZnO/rGO nanostructures in the range 4000–400 cm1. The broad peak in the range 3950–3232 cm1 corresponds to the vibrational mode of OAH bond. Also stretching modes of vibrations in asymmetric and symmetric C@O bonds are observed at 1465– 1543 cm1, respectively. The peaks located at 2283 – 2924 cm1 are due to symmetric and asymmetric CAH bonds, respectively. Furthermore, broad absorption peaks centered at around 1373 cm1 is caused by the OAH stretching of the absorbed water re-absorption through the storage of the sample in ambient air. The presence of the ZnO bond is indicated by the absorption peak at 478 cm1 for pure ZnO; similarly, for 3% Sn doped ZnO-rGO sample it is pointed out from absorption peak in the range of 470 cm1. New absorption peaks at 447 cm1, 532 cm1, 617 cm1, 624 cm1, 663 cm1, 408 cm1, 439 cm1 and 470 cm1 appear as Sn concen-
Fig. 2. FT-IR Spectra of pure ZnO, ZnO-rGO and Sn doped ZnO/rGO nanostructures.
tration increases to 3%. A peculiar peak at 1056 cm1 is observed in the 3% Sn concentration was assigned to CAO stretch bond [14]. 3.3. SEM analysis The morphology and microstructure of the Sn doped ZnO/rGO nanoparticles are examined by SEM as illustrated in Fig. 3(a)–(d).
Please cite this article as: A. Priyadharsan, S. Shanavas, C. Vidya et al., Structural and optical properties of Sn doped ZnO-rGO nanostructures using hydrothermal technique, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.05.440
A. Priyadharsan et al. / Materials Today: Proceedings xxx (xxxx) xxx
It can be seen that particles with little aggregation are attached to the rGO sheet, and distribution of Sn particles all over the surfaces of ZnO-rGO particles with a size range of 45–70 nm (Fig. 3(a) and (b)). The thin sheet shows a typical 2D structure with many wrinkles and folds. In most cases, the introduction of rGO has a negligible influence on the morphology of the product. The flexible rGO sheets can be observed clearly on the surface of the spherical aggregates, which indicates the formation of Sn doped ZnO/rGO nanostructures.
3
3.4. Energy-dispersive X-ray spectroscopy (EDS or EDX) The elemental composition in Sn doped ZnO/rGO nanostructures can be confirmed by energy dispersive EDX in Fig. 4(a) and (b). It is one of the variants of X-ray fluorescence spectroscopy which relies on the investigation of a sample through interactions between electromagnetic radiation and matter. EDX analyses in the scanning electron microscopy (FE-SEM) mode have shown the presence of Sn, O, Zn and C elements in the Sn doped ZnO/ rGO nanostructures. The EDS spectrum indicates that the marked
Fig. 3. (a–d) SEM images of as-prepared Sn doped ZnO-rGO Nanostructures.
Fig. 4. (a, b) EDX spectra of the 3% Sn doped ZnO-rGO Nanoparticles.
Please cite this article as: A. Priyadharsan, S. Shanavas, C. Vidya et al., Structural and optical properties of Sn doped ZnO-rGO nanostructures using hydrothermal technique, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.05.440
4
A. Priyadharsan et al. / Materials Today: Proceedings xxx (xxxx) xxx
Fig. 5. (a) UV–Vis diffuse reflectance spectra of pure ZnO, ZnO-rGO and Sn doped ZnO/rGO nanostructures (b) plot of band gap energy of pure ZnO, ZnO-rGO and Sn doped ZnO/rGO nanostructures.
area in Fig. 4a contains 16.17 wt% Sn, 10.11 wt% O, 55.86 wt% Zn, and 17.86 wt% C. The atomic percentage from Fig. 4b found to be 4.38 wt% Sn, 20.33 wt% O, 27.48 wt% Zn, and 47.81 wt% C. 3.5. Uv–visible–diffused reflectance spectroscopy (UV-DRS) The UV–Vis reflectance spectra of the pure ZnO, ZnO-rGO and Sn doped ZnO/rGO nanostructures are shown in Fig. 5(a) and (b). The reflectance values were transformed to absorbance by use of the Kubelka Munk translation, Eq. (1) 2
K ¼ ð1 RÞ =2R
ð1Þ
where K is the reflectance transformed according to Kubelka Munk and R is the reflectance (%). The relationship between (K * hm)1/2 = f (h * m) is shown in Fig. 5(a) and (b). This plot gives band gap energies of 3.2 eV for ZnO, 3.18 eV for ZnO-rGO and 3.15 eV for Sn doped ZnO/rGO nanostructures. It can be noticed that the band gap decreased on nanoparticles. This performance is the result of a slightly increases in the free carrier concentration due to rGO adding and the corresponding descending shift of the Fermi level to less than of the band edge. Therefore, the band gap decrement observed in Sn doped ZnO/rGO nanostructures could be attributed due to its increased size compared with ZnO and optical response of Sn doped ZnO/rGO nanostructures was enhanced in favour of dye sensitized solar cell (DSSC) and photocatalytic applications. 4. Conclusion In the present work, we have successfully synthesized ZnO, ZnO-rGO and Sn doped ZnO/rGO nanostructures using hydrothermal technique. Powder XRD pattern of the samples (rGO, ZnO) matches with the hexagonal structure and the following miller indices were good in agreement. The average particle sizes were found to be around 40 nm and 36 nm for as prepared samples of ZnO and Sn doped ZnO/rGO nanostructures. SEM analysis confirms
that both the as prepared samples are monodispersed spherical shape morphology with uniform distribution. The band gap energy was calculated as 3.2 eV, 3.18 eV, and 3.15 eV for ZnO, ZnO-rGO, Sn doped ZnO/rGO nanostructures by UV–Vis spectra analysis. Overall, these materials could have applications in different fields such as cathode materials in solid oxide fuel cell, gas sensors, photocatalytic activity, antibacterial performance and DSSC in solar cell applications. References [1] I. Khan, K. Saeed, I. Khan, Arab. J. Chem. (2017), https://doi.org/10.1016/j. arabjc.2017.05.011. [2] M.A. El-Sayed, Acc. Chem. Res. 37 (2004) 326–333, https://doi.org/10.1021/ ar020204f. [3] G. Wang, A. Morrin, M. Li, N. Liu, X. Luo, J. Mater. Chem. B 6 (2018) 4173–4190, https://doi.org/10.1039/c8tb00817e. [4] A. Priyadharsan, S. Shanavas, V. Vasanthakumar, B. Balamuralikrishnan, P.M. Anbarasan, Colloids Surf. A Physicochem. Eng. Asp. 559 (2018) 43–53, https:// doi.org/10.1016/j.colsurfa.2018.09.034. [5] J. Ding, Y. Zhou, G. Dong, M. Liu, D. Yu, F. Liu, Prog. Photovoltaics Res. Appl. 26 (2018) 974–980, https://doi.org/10.1002/pip.3044. [6] Y. Wang, X. Xiao, H. Xue, H. Pang, ChemistrySelect 3 (2018) 550–565, https:// doi.org/10.1002/slct.201702780. [7] D. Vanmaekelbergh, L.K. Van Vugt, Nanoscale 3 (2011) 2783–2800, https://doi. org/10.1039/c1nr00013f. [8] Y. Li, X. Zhao, W. Fan, J. Phys. Chem. C. 115 (2011) 3552–3557, https://doi.org/ 10.1021/jp1098816. [9] S. Kasap, C. Koughia, H.E. Ruda, Electron. Photon. Mater. (2017) 1, https://doi. org/10.1007/978-3-319-48933-9_2. [10] M. Koperski, M.R. Molas, A. Arora, K. Nogajewski, A.O. Slobodeniuk, C. Faugeras, M. Potemski, Nanophotonics 6 (2017) 1289–1308, https://doi.org/ 10.1515/nanoph-2016-0165. [11] A. Priyadharsan, V. Vasanthakumar, S. Shanavas, S. Karthikeyan, P.M. Anbarasan, Appl. Surf. Sci. 470 (2019) 114–128, https://doi.org/10.1016/j. apsusc.2018.11.130. [12] S. Shanavas, A. Priyadharsan, I. Gkanas, R. Acevedo, P.M. Anbarasan, J. Ind. Eng. Chem. 72 (2019) 512–528, https://doi.org/10.1016/j.jiec.2019.01.008. [13] G. Grübel, E.V. Shevchenko, I. Mekis, A. Kornowski, A. Robert, H. Borchert, H. Weller, Langmuir 21 (2005) 1931–1936, https://doi.org/10.1021/la0477183. [14] B. Li, T. Liu, Y. Wang, Z. Wang, J. Colloid Interf. Sci. 377 (2012) 114–121, https:// doi.org/10.1016/j.jcis.2012.03.060.
Please cite this article as: A. Priyadharsan, S. Shanavas, C. Vidya et al., Structural and optical properties of Sn doped ZnO-rGO nanostructures using hydrothermal technique, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.05.440