- Email: [email protected]
Photon Upconversion in 3D Dendritic α-Fe2O3
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 4 (2017) 5620–5624
www.materialstoday.com/proceedings
ICMDA 2016
Photon Upconversion in 3D Dendritic α-Fe2O3 S. Majumdera,b*, S. Palb, S. Kumara and S. Banerjeeb aDepartment of Physics, Jadavpur University, Kolkata – 700032, India Saha Institute of Nuclear Physics , 1/AF Bidhannagar, Kolkata – 700064, India
b
Abstract In the present work, we have successfully synthesized a large scale of 3D dendritic α-Fe2O3 structures via a simple hydrothermal reaction through hydrolysis of K3Fe(CN)6 precursor. The crystallinity, composition and morphology of the synthesized sample have been characterized by powder X-ray diffraction (PXRD), field emission scanning electron microscopic (FESEM) and energy dispersive X-ray spectroscopic (EDS) techniques. PXRD study indicates that it is well crystalline and single phase in nature. FESEM images reveal that the shape of the sample is dendritic structured with symmetric branches along each arm consists of a long central trunk with secondary branches. The optical properties have been performed by UV-Vis and a photoluminescence (PL) spectrum, where UV-Vis spectra showing visible light absorption and PL exhibiting a peak near UV region indicates up-conversion property. So, we can use this sample for visible light mediated catalysis applications, photodectector and photo-voltaic application purposes. © 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of INTERNATIONAL CONFERENCE ON MULTIFUNCTIONAL MATERIALS FOR DEVICE APPLICATIONS(ICMDA-2016). Keywords: 3D dendritic architectures, hematite, up-conversion and optical detector.
Corresponding Author’s Email- [email protected]
*
2214-7853 © 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of INTERNATIONAL CONFERENCE ON MULTIFUNCTIONAL MATERIALS
FOR DEVICE APPLICATIONS(ICMDA-2016).
S.Majumder et al/ / Materials Today: Proceedings 4 (2017) 5620–5624
5621
1.
Introduction Recently nano/micro sized particles have emerged as effective applicants in the field of material physics and chemistry for their wide spread technological applications [1-10]. Iron can form several oxides of different stoichiometry and crystalline phases. The various iron oxides are namely wustite (FeO), magnetite (Fe3O4), hematite (α-Fe2O3) and maghemite (γ-Fe2O3). Hematite has an extensive attention due to its good intrinsic physical and chemical properties such as its low cost, stability under ambient condition and environmentally friendly properties. Various α-Fe2O3 nanostructures have been synthesized including nanorods, nanodots, nanowires, nanobelts, nanotubes, nanodisks and nanorings through different synthesis process [1116]. Recently, Bharathi et al. have shown that a hydrothermal reaction without surfactant leads to the formation of 3-D dendritic α-Fe2O3 structures, whereas the use of CTAB and PEG as surfactants during the reaction results in single and double layered snowflake structures of six-fold symmetry, respectively [13]. According to Zhen et al., NP-9 surfactant converts dendritic micropines of α-Fe2O3 to hexagonal micro-snowflakes [17]. Different αFe2O3 nanostructures show different size and shape dependent properties, which have been triggered lots of research on the morphology control of α-Fe2O3. Up to now, a variety of α-Fe2O3 structures, such as 0D, 1D, 2D, and 3D have been synthesized by different methods in which the 3D architectures often produce more active sites or exhibit more interesting catalytic, and optical properties than 2D or 1D architectures [13-16]. Therefore, there have been great interests in the creation of α-Fe2O3 with 3D architectures for various applications purposes. In this manuscript, 3D dendritic structured α-Fe2O3 has been synthesized by facile one-step hydrorhermal method without any surfactant. Here we have studied optical property of dendritic α-Fe2O3, which exhibits absorption spectra in the visible region and up-conversion emission spectra in the UV region, which is very interesting in optical applications. 2. Materials and Methods 2.1 Materials Potassium ferricyanide (K3[Fe(CN)6) was purchased from Loba Chemie and used without further purification for synthesis purpose. Deionized water (D.I.) was used as a solvent for all the experiments. 2.2 Synthesis of 3Dmicro-snowflake structured α-Fe2O3: 0.2666 gm. of K3[Fe(CN)6] was dissolved in 80 mL of D.I. The aqueous solution was then transferred into 100 mL teflon-lined autoclave. Then the hydrothermal reaction was conducted at 180°C for 8 hrs. After that, the autoclave was allowed to cool down to room temperature and the precipitate was washed several times in D.I. and ethanol by vigorous centrifugation. Afterward, the collected samples were dried at 65°C for 12 h in a vacuum oven. 2.3 Characterizations of micro-snowflake structured α-Fe2O3 The microstructural characterization have been performed by using field emission scanning electron microscopic (FEI, INSPECT F50) techniques. The presence of constituent elements in the sample was probed by BRUKER EDS system attached with the FESEM equipment. The powder x-ray diffraction (PXRD) pattern of the sample has been recorded by Bruker D8 Advanced Diffractometer using Cu Kα (λ = 1.54184 Å) radiation at ambient temperature (21°C). The UV-Vis data has been collected by dispersing it in D.I. through vigorous ultra-sonication using JASCO V-630 spectrophotometer. The photoluminescence (PL) spectra of the sample have been recorded by JASCO FP6700 spectrophotometer at room temperature.
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S.Majumder et al/ Materials Today: Proceedings 4 (2017) 5620–5624
3. Results and Discussion 3.1 PXRD, FESEM, EDS and FTIR study: The microstructural property and surface morphology have been investigated by field emission scanning electron microscopic (FESEM) technique. The FESEM images both at high and low magnification have been depicted in Fig. 1(a) and 1(b) respectively. The FESEM images clearly establish the formation of 3D dendritic structures of α-Fe2O3. The individual α-Fe2O3 dendritic arms consist of a long central trunk of length ~ 5-6 µm with secondary branches of length ~ 1-2 µm uniformly distributed on the both sides of the central trunk. The crystallographic phase of S1 was identified by PXRD, as shown in Fig. 1(c). The diffraction peaks at 33.3, 35.9, 41.0, 49.63, 54.27, 57.76, 62.57, 64.15, 72.19 and 75.61 correspond to the [104], [110], [113], [024], [116], [122], [214], [300], [119] and [226] planes of α-Fe2O3 are well-matched with the standard JCPDS 33-0664. The diffraction pattern indicates that the α-Fe2O3 particles are in single phase and well crystalline in nature. The presence of the constituent elements in the sample has been carried out by energy dispersive x-ray study (EDS) analysis. The EDS spectrum illustrating the well resolved peaks originating from the constituent atoms in the energy range from 0 to 8 eV has been shown in Fig. 1(d). The Au Lα peak in the EDS spectrum can be attributed to the gold coating of the sample prior to EDS study. The EDS spectrum clearly indicates the presence of all the constituent elements (Fe and O) in α-Fe2O3.
Fig. 1. (a, b) FESEM images , (c) PXRD pattern and (d) EDS spectrum of S1
Till now various types of complex architectures of α-Fe2O3 like nanoparticles, nanocage like structure, hollow spheres, snowflakes have been synthesized by different routes. So, to build up a standard, simple, reliable and high yielding reaction mechanism for the synthesis of complex architectures of α-Fe2O3 is a big challenge. In our previous manuscript we have synthesized four samples by changing the reaction time keeping reaction temperature fixed and showed that micro-snowflake structured α-Fe2O3 could be suitable platforms for enzyme-less
S.Majumder et al/ / Materials Today: Proceedings 4 (2017) 5620–5624
5623
H2O2 and N2H4 sensing [1]. Moreover, we discussed there the growth mechanism in details. Here, we have synthesized 3D architecture of dendritic α-Fe2O3 from K3[Fe(CN)6] by hydrothermal technique in normal pH without using any surfactant. Actually, [Fe(CN)6]3- ion is highly stable at room temperature. Hydrothermal procedure of the aqueous solution of K3[Fe(CN)6] at high temperature (180°C) for extended time results in the dissociation of [Fe(CN)6]3- ions into Fe3+ ions, which upon further hydrolysis gets converted into FeOOH/Fe(OH)3. Due to high temperature hydrothermal reaction the FeOOH/Fe (OH)3 further dissociates into α-Fe2O3 and forms dendritic α-Fe2O3. 3.2 Optical study The UV-Vis spectrum is depicted in Fig. 2(a). The UV-Vis spectrum exhibits a broad peak at around 573 nm due to the Fe3+ 3d–3d spin forbidden transition (indirect transition) and also shows a peak at around 350 nm due to the direct charge transfer transitions from O2- 2p to Fe3+ 3d [18]. The photoluminescence (PL) emission spectra at an excitation wavelength of 360 nm are presented in Fig. 2(b). The spectra exhibit an intense peak near UV region at around 310 nm indicating clear up-conversion of energy. Moreover at 330 nm, a small peak is present there may be due to defect sites in α-Fe2O3. So, it has been observed that visible light gives an emission in the UV region at around 310 nm. So the sample can be used for optical applications purpose.
Fig. 2. (a) UV-Vis and (b) PL spectra of S1
4.
Conclusions
In a nutshell, we have successfully synthesized 3D dendritic α-Fe2O3 structures through a simple hydrothermal reaction in normal pH without using any surfactant. The length of the as-synthesized dendritic α-Fe2O3 structure is about 3-6µm. UV-Vis and PL spectra reveal up-conversion of energy and hence the sample could be used in optical application purposes. Acknowledgments One of the authors (S.M.) gratefully acknowledges UGC, Govt. of India for providing research fellowship. Authors would like to Dr. Gayathri N. Banerjee (Scientific Officer E, VECC India) for PXRD measurement of the sample.
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S.Majumder et al/ Materials Today: Proceedings 4 (2017) 5620–5624
References [1] S. Majumder, B. Saha, S. Dey, R. Mondal, S. Kumar and S. Banerjee, RSC Advances, 6 (2016) 65. [2] S. Majumder, B. Saha, S. Dey, K. Bagani, M. K. Roy, S. K. Jana, S. Kumar and S. Banerjee, AIP Conf. Proc., 1665 (2015) 050117. [3] S. Majumder, S. Dey, K. Bagani, S. K. Dey, S. Banerjee and S. Kumar, Dalton trans., 44 (2015) 7160. [4] S. K. Jana, S. Majumder, B. Satpati, S. K. Mishra, R.K. Srivastava and S. Banerjee, RSc Advance, 5 (2015) 37729. [5] S. Dey, S. K. Dey, K. Bagani, S. Majumder, A. Roychowdhury, S. Banerjee, V. R. Reddy, D. Das and S. Kumar, Apllied Physics Letter., 105 (2014) 063110. [6] S. Majumder, S. K. Jana, K. Bagani, B. Satpati, S. Kumar and S. Banerjee, Optical materials, 40 (2015) 77-101. [7] S. Dey, R. Mondal, S. K. Dey, S. Majumder, P. Dasgupta, A. Poddar, V. R. Reddy and S. Kumar, J. Appl. Phys, 118 (2015) 103905. [8] S. Dey, S. K. Dey, S. Majumder, A. Poddar, P. Dasgupta, S. Banerjee and S. Kumar, Physica B, 448 (2014) 247-252. [9] B. Saha, S. K .Jana, S. Majumder, B. Satpati and S. Banerjee, Electrochimica Acta , 174 (2015) 853–863. [10] S. Majumder, S. Dey, P. Dasgupta, A. Poddar, S. Banerjee and S. Kumar, 1665 (2015) 130035. [11] Y. Wang, J. L. Cao, M. G. Yu, G. Sun, X. D. Wang, H. Bala and Z. Y. Zhang, Mater. Lett., 100 (2013) 102. [12] X. Cao and N. Wang, Analyst, 136 (2011) 4241. [13] S. Bharathi, D. Nataraj, M. Seetha, D. Mangalaraj, N. Ponpandian, Y. Masuda, K. Senthil and K. Yong, CrystEngComm., 12 (2010) 373. [14] M. Cao, T. Liu, S. Gao, G. Sun, X. Wu, C. Hu and Z. L. Wang, Angew. Chem., Int. Ed., 44 (2005) 4197. [15] Z. Liu, B. Lv, D. Wu, Y. Zhu and Y. Sun, CrystEngComm, 14 (2012) 4074. [16] Y. Jiao, Y. Liu, F. Qu and X. Wu, CrystEngComm, 16 (2014) 575. [17] S. Dey, R. Gomes, R. Mondal, S. K. Dey, P. Dasgupta, A. Poddar, V. R. Reddy, A. Bhaumik and S. Kumar, RSC Adv., 5 (2015) 78508. [18] R. Suresh, K. Giribabu, R. Manigandan, A. Stephen and V. Narayanan, RSC Adv., 4 (2014) 17146.
ScienceDirect Materials Today: Proceedings 4 (2017) 5620–5624
www.materialstoday.com/proceedings
ICMDA 2016
Photon Upconversion in 3D Dendritic α-Fe2O3 S. Majumdera,b*, S. Palb, S. Kumara and S. Banerjeeb aDepartment of Physics, Jadavpur University, Kolkata – 700032, India Saha Institute of Nuclear Physics , 1/AF Bidhannagar, Kolkata – 700064, India
b
Abstract In the present work, we have successfully synthesized a large scale of 3D dendritic α-Fe2O3 structures via a simple hydrothermal reaction through hydrolysis of K3Fe(CN)6 precursor. The crystallinity, composition and morphology of the synthesized sample have been characterized by powder X-ray diffraction (PXRD), field emission scanning electron microscopic (FESEM) and energy dispersive X-ray spectroscopic (EDS) techniques. PXRD study indicates that it is well crystalline and single phase in nature. FESEM images reveal that the shape of the sample is dendritic structured with symmetric branches along each arm consists of a long central trunk with secondary branches. The optical properties have been performed by UV-Vis and a photoluminescence (PL) spectrum, where UV-Vis spectra showing visible light absorption and PL exhibiting a peak near UV region indicates up-conversion property. So, we can use this sample for visible light mediated catalysis applications, photodectector and photo-voltaic application purposes. © 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of INTERNATIONAL CONFERENCE ON MULTIFUNCTIONAL MATERIALS FOR DEVICE APPLICATIONS(ICMDA-2016). Keywords: 3D dendritic architectures, hematite, up-conversion and optical detector.
Corresponding Author’s Email- [email protected]
*
2214-7853 © 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of INTERNATIONAL CONFERENCE ON MULTIFUNCTIONAL MATERIALS
FOR DEVICE APPLICATIONS(ICMDA-2016).
S.Majumder et al/ / Materials Today: Proceedings 4 (2017) 5620–5624
5621
1.
Introduction Recently nano/micro sized particles have emerged as effective applicants in the field of material physics and chemistry for their wide spread technological applications [1-10]. Iron can form several oxides of different stoichiometry and crystalline phases. The various iron oxides are namely wustite (FeO), magnetite (Fe3O4), hematite (α-Fe2O3) and maghemite (γ-Fe2O3). Hematite has an extensive attention due to its good intrinsic physical and chemical properties such as its low cost, stability under ambient condition and environmentally friendly properties. Various α-Fe2O3 nanostructures have been synthesized including nanorods, nanodots, nanowires, nanobelts, nanotubes, nanodisks and nanorings through different synthesis process [1116]. Recently, Bharathi et al. have shown that a hydrothermal reaction without surfactant leads to the formation of 3-D dendritic α-Fe2O3 structures, whereas the use of CTAB and PEG as surfactants during the reaction results in single and double layered snowflake structures of six-fold symmetry, respectively [13]. According to Zhen et al., NP-9 surfactant converts dendritic micropines of α-Fe2O3 to hexagonal micro-snowflakes [17]. Different αFe2O3 nanostructures show different size and shape dependent properties, which have been triggered lots of research on the morphology control of α-Fe2O3. Up to now, a variety of α-Fe2O3 structures, such as 0D, 1D, 2D, and 3D have been synthesized by different methods in which the 3D architectures often produce more active sites or exhibit more interesting catalytic, and optical properties than 2D or 1D architectures [13-16]. Therefore, there have been great interests in the creation of α-Fe2O3 with 3D architectures for various applications purposes. In this manuscript, 3D dendritic structured α-Fe2O3 has been synthesized by facile one-step hydrorhermal method without any surfactant. Here we have studied optical property of dendritic α-Fe2O3, which exhibits absorption spectra in the visible region and up-conversion emission spectra in the UV region, which is very interesting in optical applications. 2. Materials and Methods 2.1 Materials Potassium ferricyanide (K3[Fe(CN)6) was purchased from Loba Chemie and used without further purification for synthesis purpose. Deionized water (D.I.) was used as a solvent for all the experiments. 2.2 Synthesis of 3Dmicro-snowflake structured α-Fe2O3: 0.2666 gm. of K3[Fe(CN)6] was dissolved in 80 mL of D.I. The aqueous solution was then transferred into 100 mL teflon-lined autoclave. Then the hydrothermal reaction was conducted at 180°C for 8 hrs. After that, the autoclave was allowed to cool down to room temperature and the precipitate was washed several times in D.I. and ethanol by vigorous centrifugation. Afterward, the collected samples were dried at 65°C for 12 h in a vacuum oven. 2.3 Characterizations of micro-snowflake structured α-Fe2O3 The microstructural characterization have been performed by using field emission scanning electron microscopic (FEI, INSPECT F50) techniques. The presence of constituent elements in the sample was probed by BRUKER EDS system attached with the FESEM equipment. The powder x-ray diffraction (PXRD) pattern of the sample has been recorded by Bruker D8 Advanced Diffractometer using Cu Kα (λ = 1.54184 Å) radiation at ambient temperature (21°C). The UV-Vis data has been collected by dispersing it in D.I. through vigorous ultra-sonication using JASCO V-630 spectrophotometer. The photoluminescence (PL) spectra of the sample have been recorded by JASCO FP6700 spectrophotometer at room temperature.
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S.Majumder et al/ Materials Today: Proceedings 4 (2017) 5620–5624
3. Results and Discussion 3.1 PXRD, FESEM, EDS and FTIR study: The microstructural property and surface morphology have been investigated by field emission scanning electron microscopic (FESEM) technique. The FESEM images both at high and low magnification have been depicted in Fig. 1(a) and 1(b) respectively. The FESEM images clearly establish the formation of 3D dendritic structures of α-Fe2O3. The individual α-Fe2O3 dendritic arms consist of a long central trunk of length ~ 5-6 µm with secondary branches of length ~ 1-2 µm uniformly distributed on the both sides of the central trunk. The crystallographic phase of S1 was identified by PXRD, as shown in Fig. 1(c). The diffraction peaks at 33.3, 35.9, 41.0, 49.63, 54.27, 57.76, 62.57, 64.15, 72.19 and 75.61 correspond to the [104], [110], [113], [024], [116], [122], [214], [300], [119] and [226] planes of α-Fe2O3 are well-matched with the standard JCPDS 33-0664. The diffraction pattern indicates that the α-Fe2O3 particles are in single phase and well crystalline in nature. The presence of the constituent elements in the sample has been carried out by energy dispersive x-ray study (EDS) analysis. The EDS spectrum illustrating the well resolved peaks originating from the constituent atoms in the energy range from 0 to 8 eV has been shown in Fig. 1(d). The Au Lα peak in the EDS spectrum can be attributed to the gold coating of the sample prior to EDS study. The EDS spectrum clearly indicates the presence of all the constituent elements (Fe and O) in α-Fe2O3.
Fig. 1. (a, b) FESEM images , (c) PXRD pattern and (d) EDS spectrum of S1
Till now various types of complex architectures of α-Fe2O3 like nanoparticles, nanocage like structure, hollow spheres, snowflakes have been synthesized by different routes. So, to build up a standard, simple, reliable and high yielding reaction mechanism for the synthesis of complex architectures of α-Fe2O3 is a big challenge. In our previous manuscript we have synthesized four samples by changing the reaction time keeping reaction temperature fixed and showed that micro-snowflake structured α-Fe2O3 could be suitable platforms for enzyme-less
S.Majumder et al/ / Materials Today: Proceedings 4 (2017) 5620–5624
5623
H2O2 and N2H4 sensing [1]. Moreover, we discussed there the growth mechanism in details. Here, we have synthesized 3D architecture of dendritic α-Fe2O3 from K3[Fe(CN)6] by hydrothermal technique in normal pH without using any surfactant. Actually, [Fe(CN)6]3- ion is highly stable at room temperature. Hydrothermal procedure of the aqueous solution of K3[Fe(CN)6] at high temperature (180°C) for extended time results in the dissociation of [Fe(CN)6]3- ions into Fe3+ ions, which upon further hydrolysis gets converted into FeOOH/Fe(OH)3. Due to high temperature hydrothermal reaction the FeOOH/Fe (OH)3 further dissociates into α-Fe2O3 and forms dendritic α-Fe2O3. 3.2 Optical study The UV-Vis spectrum is depicted in Fig. 2(a). The UV-Vis spectrum exhibits a broad peak at around 573 nm due to the Fe3+ 3d–3d spin forbidden transition (indirect transition) and also shows a peak at around 350 nm due to the direct charge transfer transitions from O2- 2p to Fe3+ 3d [18]. The photoluminescence (PL) emission spectra at an excitation wavelength of 360 nm are presented in Fig. 2(b). The spectra exhibit an intense peak near UV region at around 310 nm indicating clear up-conversion of energy. Moreover at 330 nm, a small peak is present there may be due to defect sites in α-Fe2O3. So, it has been observed that visible light gives an emission in the UV region at around 310 nm. So the sample can be used for optical applications purpose.
Fig. 2. (a) UV-Vis and (b) PL spectra of S1
4.
Conclusions
In a nutshell, we have successfully synthesized 3D dendritic α-Fe2O3 structures through a simple hydrothermal reaction in normal pH without using any surfactant. The length of the as-synthesized dendritic α-Fe2O3 structure is about 3-6µm. UV-Vis and PL spectra reveal up-conversion of energy and hence the sample could be used in optical application purposes. Acknowledgments One of the authors (S.M.) gratefully acknowledges UGC, Govt. of India for providing research fellowship. Authors would like to Dr. Gayathri N. Banerjee (Scientific Officer E, VECC India) for PXRD measurement of the sample.
5624
S.Majumder et al/ Materials Today: Proceedings 4 (2017) 5620–5624
References [1] S. Majumder, B. Saha, S. Dey, R. Mondal, S. Kumar and S. Banerjee, RSC Advances, 6 (2016) 65. [2] S. Majumder, B. Saha, S. Dey, K. Bagani, M. K. Roy, S. K. Jana, S. Kumar and S. Banerjee, AIP Conf. Proc., 1665 (2015) 050117. [3] S. Majumder, S. Dey, K. Bagani, S. K. Dey, S. Banerjee and S. Kumar, Dalton trans., 44 (2015) 7160. [4] S. K. Jana, S. Majumder, B. Satpati, S. K. Mishra, R.K. Srivastava and S. Banerjee, RSc Advance, 5 (2015) 37729. [5] S. Dey, S. K. Dey, K. Bagani, S. Majumder, A. Roychowdhury, S. Banerjee, V. R. Reddy, D. Das and S. Kumar, Apllied Physics Letter., 105 (2014) 063110. [6] S. Majumder, S. K. Jana, K. Bagani, B. Satpati, S. Kumar and S. Banerjee, Optical materials, 40 (2015) 77-101. [7] S. Dey, R. Mondal, S. K. Dey, S. Majumder, P. Dasgupta, A. Poddar, V. R. Reddy and S. Kumar, J. Appl. Phys, 118 (2015) 103905. [8] S. Dey, S. K. Dey, S. Majumder, A. Poddar, P. Dasgupta, S. Banerjee and S. Kumar, Physica B, 448 (2014) 247-252. [9] B. Saha, S. K .Jana, S. Majumder, B. Satpati and S. Banerjee, Electrochimica Acta , 174 (2015) 853–863. [10] S. Majumder, S. Dey, P. Dasgupta, A. Poddar, S. Banerjee and S. Kumar, 1665 (2015) 130035. [11] Y. Wang, J. L. Cao, M. G. Yu, G. Sun, X. D. Wang, H. Bala and Z. Y. Zhang, Mater. Lett., 100 (2013) 102. [12] X. Cao and N. Wang, Analyst, 136 (2011) 4241. [13] S. Bharathi, D. Nataraj, M. Seetha, D. Mangalaraj, N. Ponpandian, Y. Masuda, K. Senthil and K. Yong, CrystEngComm., 12 (2010) 373. [14] M. Cao, T. Liu, S. Gao, G. Sun, X. Wu, C. Hu and Z. L. Wang, Angew. Chem., Int. Ed., 44 (2005) 4197. [15] Z. Liu, B. Lv, D. Wu, Y. Zhu and Y. Sun, CrystEngComm, 14 (2012) 4074. [16] Y. Jiao, Y. Liu, F. Qu and X. Wu, CrystEngComm, 16 (2014) 575. [17] S. Dey, R. Gomes, R. Mondal, S. K. Dey, P. Dasgupta, A. Poddar, V. R. Reddy, A. Bhaumik and S. Kumar, RSC Adv., 5 (2015) 78508. [18] R. Suresh, K. Giribabu, R. Manigandan, A. Stephen and V. Narayanan, RSC Adv., 4 (2014) 17146.