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Dielectric studies on PVP-CH3COONa based solid polymer electrolytes
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 5 (2018) 26405–26410
www.materialstoday.com/proceedings
PCNCM2017
Dielectric studies on PVP-CH3COONa based solid polymer electrolytes M. Seshu Kumara,b and M.C. Raob,* a b
Department of Physics, Krishna University, Machilipatnam-521001, India Department of Physics, Andhra Loyola College, Vijayawada-520008, India
Abstract Solid polymer electrolytes have been prepared with different wt% compositional ratios of PVP-CH3COONa by solution cast technique. The ionic conductivity of the prepared solid polymer electrolytes has been measured by the Nyquist plots and the higher ionic conductivity was found to be 2.32x10-5 S/cm at higher temperature for the composition 80PVP:20CH3COONa. Dielectric studies were performed on the prepared polymer films at room temperature in the frequency ranging between 5000 Hz and 50000 Hz to find the best optimum conductivity and electric relaxation process of the samples. © 2018 Elsevier Ltd. All rights reserved. Peer-review under responsibility of the scientific committee of the Proceedings of National Seminar on Physics and Chemistry of NonCrystalline Materials. Keywords: Solid polymer electrolyte; Solution cast technique; AC-ionic conductivity; Dielectric studies.
1. Introduction For the past few decades’ an attractive attention has been made towards composite based materials due to the low production cost and excellent structural, electrical, thermal and magnetic properties. Solid polymer films are expected to exhibit a major change in wide range of technological applications and industrial fields such as electrochemical cells, humidity sensors, microwave absorbing and fuel cells etc. Solid polymer films are prepared by doping inorganic salt in the host polymer. The mechanism of solid polymer electrolytes and the advantages were reported by Wright and Armand in 1970s [1-3]. Due to many advantages solid polymer electrolytes have taken a
* Corresponding author. Tel.: 0866-2453485. E-mail address: [email protected] 2214-7853© 2018 Elsevier Ltd. All rights reserved. Peer-review under responsibility of the scientific committee of the Proceedings of National Seminar on Physics and Chemistry of NonCrystalline Materials.
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M. Seshu Kumar et al./ Materials Today: Proceedings 5 (2018) 26405–26410
new development in the field of energy storage devices. The work on these polymer electrolytes has received great attention and leads a new way to the researches in the development of batteries and electrochromic windows based on the fast ion movement [4, 5]. Over a past few years batteries play a major role in the field of electric energy applications. During the last decade, applications for traditional and new practical battery systems have been increased. Due to these rapid growths, more compact, lighter, portable, safe and high energy density of the battery is required. Solid polymer electrolyte (SPE) has been the prime candidate to meet this demand. To obtain the SPE with high ionic conductivity with improved mechanical strength, a few factors have been taken into consideration. The solid polymer electrolytes must possess uniform surfaces having less brittle nature. The thickness of the films must be around 60-150 μm. By the dispersion of inorganic salt in the host polymer an improvement in ionic conductivity can be observed in the polymer films [6]. Rao et al. published their results on different materials in the earlier studies [7-20]. In the present investigation, solid polymer films were prepared with different wt% composition ratios of PVPCH3COONa in order to improve the ionic conductivity and dielectric properties of the composite polymer films. 2. Experimental 2.1. Preparation of solid polymer electrolytes: PVP with average molecular weight (M.W: 36,000 g/mol), Sodium acetate (CH3COONa) 98% pure were purchased from Sigma Aldrich chemicals, India. All the samples were prepared in different wt% compositional ratios (95:5), (90:10), (85:15) and (80:20) by using solution cast technique. In the preparation process triple distilled water was used as a solvent. The proposed wt% ratios of chemicals is taken in beakers with solvent and allowed to stir for 24 hours to obtain a homogeneous solution. After the solution was taken in dishes and kept in a hot air oven at 60 oC. Later the prepared films were placed in a vacuum desiccator. 3. Results and discussion Nyquist plots of the prepared polymer electrolyte films with different wt% compositional ratios of CH3COONa salt doped PVP polymer complex system is shown in Fig. 1.
Fig. 1. AC-Ionic conductivity of solid polymer electrolyte films. The ionic conductivity was measured by placing the sample between the two silver plates and a constant load is applied across the sample. The resultant frequency is adjusted such that the Cole-Cole plots have been obtained and are screened on a monitor. In general while increasing the frequency the Cole-Cole plots show a semi-circular arc at high frequency region later show the spike shape at the low frequency region [21]. But in Fig. 1, a semicircle has been observed which results the formation of double layer capacitance at the electrode–electrolyte interface where the drifting of ions takes place high at lower frequency region. In polymer electrolyte system the drifting of ions was found to be high at a certain frequency region where the semicircle is formed due to the parallel combination of bulk
M. Seshu Kumar et al./ Materials Today: Proceedings 5 (2018) 26405–26410
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resistance (Rb) and bulk capacitance (Cb) of the material. An inclined straight line at the low frequency region at electrode-electrolyte interfaces. The ionic conductivity is calculated by the following relation, σac = t/(Rb x A) (1) Where “Rb” is the bulk resistance, “t” is the thickness of the film and ‘A’ is the cross sectional area of the film. The calculated values of A.C. conductivity are presented in Table 1. The ionic conductivity is found to be higher and it is 2.32x10-5 S/cm for the composition of (PVP 80% + CH3COONa 20%) at 373 K. The ionic conductivity increases due to the interlinking of cations with the polymer matrix which reduces the crystalline nature [22]. As a result the mobile charge carriers increase with increasing salt percentage ratio to the host polymer. The semicrystalline nature in the polymer converts the amorphous nature. This denotes the fact the transfer of sodium ions take place freely in the polymer chains which possess the higher ionic conductivity. Table.1 Ionic conductivity of solid polymer electrolytes.
PVP: CH3COONa (95:5)
Conductivity (Scm-1) at RT 373 K 1.02x10-9 1.13x10-8 3.24x10-8 3.12x10-7
PVP: CH3COONa (90:10)
5.32x10-8
5.64x10-7
PVP: CH3COONa (85:15)
3.10x10
-7
2.52x10-6
PVP: CH3COONa (80:20)
5.35x10-7
2.32x10-5
Solid polymer electrolyte films Pure PVP
The real (εl) and imaginary parts (ε11) of dielectric constant with respect to frequency is shown in Fig. 2(a) and Fig. 2(b). From the figures it is clearly observed that the values of real and imaginary parts are continuously decreasing with increase in frequency for a particular time of interval and becomes stabilized due to polarization phenomenon and also observed that the dielectric constant value is found to be high for the sample 80PVP:20 CH3COONa. This may be due to the formation of space charge region at the electrode-electrolyte interfaces [23, 24]. The decrease in dielectric constant is due to the complete miscibility of salt in the host polymer matrix, which in turn the mobilization of ions in the polymer matrix and this lead to the enhancement of electric conductivity [25]. The logarithmic frequency with respect to real (εl) and imaginary parts (ε11) of dielectric constant is shown in Fig. 3(a) and Fig. 3(b). From the figures it is clearly observed that the values of real and imaginary parts are continuously decreasing with increase in the logarithmic frequency and the dielectric values have found to be high for the sample at 20 wt%. This may be due to the mobilization of ions resulting in the formation of electric field at the electrode surfaces [26]. Due to the complete dispersion of salt in the host polymer, the drifting of ions resulting in increase of polarizability at electrodes and is proportional to ωn-1, indicating non-Debye behavior [27, 28].
Fig. 2(a). Variation of εl with frequency for different wt% ratios.
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M. Seshu Kumar et al./ Materials Today: Proceedings 5 (2018) 26405–26410
Fig. 2(b). Variation of ε11 with frequency for different wt% ratios.
Fig. 3(a). Variation of ε1 with logarithmic frequency for different wt% ratios.
Fig. 3(b). Variation of ε1l with logarithmic frequency for different wt% ratios.
M. Seshu Kumar et al./ Materials Today: Proceedings 5 (2018) 26405–26410
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The dielectric values of the logarithmic angular frequency (ω) with respect to real (εl) and imaginary parts (ε11) for different wt% compositional ratios in shown in Fig. 4(a) and Fig. 4(b). From the figures the monotonic decrement in dielectric values has been observed with increase in the logarithmic angular frequency. The decrement of dielectric values may be due to the reduced proportion of amorphous material which leads in the magnitude of dispersion [29]. Similar behavior has been observed in the rest of the samples.
Fig. 4(a). Variation of ε1 with logarithmic angular frequency for different wt% ratios.
The variation between logarithmic conductivity with respect to the frequency is shown in Fig. 5. From the figure it is observed that the ionic conductivity increases as increasing the frequency and the maximum ionic conductivity is found for the compositional ratio 80PVP:20 CH3COONa. The enhancement of ionic conductivity due to the large scale heterogeneity of salt particles doped in the host polymer and the space charge polarization takes place at the electrode-electrolyte interfaces, where the ionic contribution is increased [30, 31].
Fig. 4(b). Variation of ε1l with logarithmic angular frequency for different wt% ratios.
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M. Seshu Kumar et al./ Materials Today: Proceedings 5 (2018) 26405–26410
Fig. 5 Variation of logarithmic conductivity vs frequency for different wt% ratios
4. Conclusions Solid polymer films have been prepared with different wt% ratios of PVP: CH3COONa by solution cast technique. AC-ionic conductivity measurements showed that the higher ionic conductivity was found to be 2.32x10-5 S/cm at higher temperature for the composition 80PVP:20 CH3COONa. Dielectric studies were performed on the prepared solid polymer electrolyte films at room temperature and found that the best optimum conductivity and electric relaxation process exist for the composition 80PVP:20 CH3COONa. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31]
P.V. Wright, Br. Polym. J. 7 (1975) 319. D.E. Fenton, J.M. Parker, P.V. Wright, Polym. 14 (1973) 589. M. B. Armand, Ann. Rev. Mater. Sci. 16 (1986) 245. X. Wang, L. Zhi, K. Muellen, Nano Lett. 8 (2008) 323-327. S. Guo, S. Dong, E. Wang, ACS Nano 4 (2010) 547-555. L. Zhang, G.J. Shi, Phys. Chem. C 115 (2011) 17206-17212. M.C. Rao, R.V.S.S.N. Ravi kumar, Sk. Muntaz Begum, AIP Conf. Proc. 1536 (2013) 27-28. Sk. Muntaz Begum, M.C. Rao, K. Ravindranadh, AIP Conf. Proc. 1349 (2011) 641-642. K. Ravindranadh, M.C. Rao, AIP Conf. Proc. 1536 (2013) 215-216. Sk. Shahenoor Basha, M.C. Rao, J. Inorg. Organomet. Polym. Mater. 27 (2017) 455-466. S. Rajyalakshmi, K. Ramachandra Rao, M.C. Rao, Int. J. ChemTech Res. 9 (1) (2016) 7-14. SK. Shahenoorbasha, K. Vijaya Kumar, M.C. Rao, Rasayan J. Chem. 9 (3) (2016) 348-354. M.S. Sekhawat, K. Ravindranadh, M.C. Rao, AIP Conf. Proc. 1536 (2013) 219-220. SK. Shahenoor Basha, K. Vijaya Kumar, M.C. Rao, Rasayan J. Chem. 9 (2016) 348-354. M.C. Rao and K. Ravindranadh, Mater. Res. Innovations 21(2) (2017) 102-105. Sk. Shahenoor Basha, G. Sunita Sundari, M.C. Rao, Rasayan J. Chem. 10 (2017) 279-285. Sk. Shahenoor Basha, K. Vijaya Kumar, M.C. Rao, J. Polym. Sci. series A 59(4) (2017) 554-565. M.C. Rao, J. Optoelecctron. Biomed. Mater. 5(1) (2013) 9-16. Sk. Shahenoor Basha, B. Ranjit Kumar, M.C. Rao, Rasayan J. Chem. 10 (2017) 1159-1166. K. Ravindranadh, R.V.S.S.N. Ravikumar , M.C. Rao, J. Non Oxide Glasses 5 (2013) 39-45. N. Li, W. Cheng, K. Ren, F. Luo, K. Wang, Q. Fu, Chin. J. Poly. Sci. 31 (2013) 98-109. L. Lin, H. Deng, X. Gao, S. Zhang, E. Bilotti, T. Peijs, Q. Fu, Poly. Int. 62 (2013) 134-140. X. Gao, S. Zhang, F. Mai, L. Lin, Y. Deng, H. Deng, Q. Fu, J. Mater. Chem. 21 (2011) 6401-6408. C.A Di, D.C. Wei, G.Yu, Y.Q. Liu, Y.L. Guo, D.B. Zhu, Adv. Mater. 20 (2008) 3289-3293. M.D. Stoller, S. Park, Y. Zhu, J. An, R.S. Ruoff, Nano Lett. 8 (2008) 3498-3502. X. Yuxi, H. Wenjing, B. Hua, L. Chun, S. Gaoquan, Carbon 47 (2009) 3538-3543. S. Stankovich, D.A. Dikin, R.D. Piner, K.M. Kohlhaas, Y. Jia, Y. Wu, S.T. Nguyen, R.S. Ruoff , Carbon 45 (2007) 1558-1565. Sk. Shahenoor Basha, B. Ranjit Kumar, K. Veera Bhadra Reddy, M.C. Rao, Chem. Sci. Rev. Lett. 6(22) (2017) 832-837. Y. Kojima, A. Usuki, M. Kawasumi, A. Okada, Y. Fukushima, T. Karauchi, O. Kamigaito, J. Poly. Sci. 31 (1993) 1775-1778. S. Morimun, M. Kotera, T. Nishino, K. Goto, K. Hata, J. Macr. Mol. 44 (2011) 4415-4421. T. Tyler, O. Shenderova, G. Cunningham, J. Walsh, J. Drobnik, G. McGuire, Diam. Relat. Mater. 15 (2006) 2078-2081.
ScienceDirect Materials Today: Proceedings 5 (2018) 26405–26410
www.materialstoday.com/proceedings
PCNCM2017
Dielectric studies on PVP-CH3COONa based solid polymer electrolytes M. Seshu Kumara,b and M.C. Raob,* a b
Department of Physics, Krishna University, Machilipatnam-521001, India Department of Physics, Andhra Loyola College, Vijayawada-520008, India
Abstract Solid polymer electrolytes have been prepared with different wt% compositional ratios of PVP-CH3COONa by solution cast technique. The ionic conductivity of the prepared solid polymer electrolytes has been measured by the Nyquist plots and the higher ionic conductivity was found to be 2.32x10-5 S/cm at higher temperature for the composition 80PVP:20CH3COONa. Dielectric studies were performed on the prepared polymer films at room temperature in the frequency ranging between 5000 Hz and 50000 Hz to find the best optimum conductivity and electric relaxation process of the samples. © 2018 Elsevier Ltd. All rights reserved. Peer-review under responsibility of the scientific committee of the Proceedings of National Seminar on Physics and Chemistry of NonCrystalline Materials. Keywords: Solid polymer electrolyte; Solution cast technique; AC-ionic conductivity; Dielectric studies.
1. Introduction For the past few decades’ an attractive attention has been made towards composite based materials due to the low production cost and excellent structural, electrical, thermal and magnetic properties. Solid polymer films are expected to exhibit a major change in wide range of technological applications and industrial fields such as electrochemical cells, humidity sensors, microwave absorbing and fuel cells etc. Solid polymer films are prepared by doping inorganic salt in the host polymer. The mechanism of solid polymer electrolytes and the advantages were reported by Wright and Armand in 1970s [1-3]. Due to many advantages solid polymer electrolytes have taken a
* Corresponding author. Tel.: 0866-2453485. E-mail address: [email protected] 2214-7853© 2018 Elsevier Ltd. All rights reserved. Peer-review under responsibility of the scientific committee of the Proceedings of National Seminar on Physics and Chemistry of NonCrystalline Materials.
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M. Seshu Kumar et al./ Materials Today: Proceedings 5 (2018) 26405–26410
new development in the field of energy storage devices. The work on these polymer electrolytes has received great attention and leads a new way to the researches in the development of batteries and electrochromic windows based on the fast ion movement [4, 5]. Over a past few years batteries play a major role in the field of electric energy applications. During the last decade, applications for traditional and new practical battery systems have been increased. Due to these rapid growths, more compact, lighter, portable, safe and high energy density of the battery is required. Solid polymer electrolyte (SPE) has been the prime candidate to meet this demand. To obtain the SPE with high ionic conductivity with improved mechanical strength, a few factors have been taken into consideration. The solid polymer electrolytes must possess uniform surfaces having less brittle nature. The thickness of the films must be around 60-150 μm. By the dispersion of inorganic salt in the host polymer an improvement in ionic conductivity can be observed in the polymer films [6]. Rao et al. published their results on different materials in the earlier studies [7-20]. In the present investigation, solid polymer films were prepared with different wt% composition ratios of PVPCH3COONa in order to improve the ionic conductivity and dielectric properties of the composite polymer films. 2. Experimental 2.1. Preparation of solid polymer electrolytes: PVP with average molecular weight (M.W: 36,000 g/mol), Sodium acetate (CH3COONa) 98% pure were purchased from Sigma Aldrich chemicals, India. All the samples were prepared in different wt% compositional ratios (95:5), (90:10), (85:15) and (80:20) by using solution cast technique. In the preparation process triple distilled water was used as a solvent. The proposed wt% ratios of chemicals is taken in beakers with solvent and allowed to stir for 24 hours to obtain a homogeneous solution. After the solution was taken in dishes and kept in a hot air oven at 60 oC. Later the prepared films were placed in a vacuum desiccator. 3. Results and discussion Nyquist plots of the prepared polymer electrolyte films with different wt% compositional ratios of CH3COONa salt doped PVP polymer complex system is shown in Fig. 1.
Fig. 1. AC-Ionic conductivity of solid polymer electrolyte films. The ionic conductivity was measured by placing the sample between the two silver plates and a constant load is applied across the sample. The resultant frequency is adjusted such that the Cole-Cole plots have been obtained and are screened on a monitor. In general while increasing the frequency the Cole-Cole plots show a semi-circular arc at high frequency region later show the spike shape at the low frequency region [21]. But in Fig. 1, a semicircle has been observed which results the formation of double layer capacitance at the electrode–electrolyte interface where the drifting of ions takes place high at lower frequency region. In polymer electrolyte system the drifting of ions was found to be high at a certain frequency region where the semicircle is formed due to the parallel combination of bulk
M. Seshu Kumar et al./ Materials Today: Proceedings 5 (2018) 26405–26410
26407
resistance (Rb) and bulk capacitance (Cb) of the material. An inclined straight line at the low frequency region at electrode-electrolyte interfaces. The ionic conductivity is calculated by the following relation, σac = t/(Rb x A) (1) Where “Rb” is the bulk resistance, “t” is the thickness of the film and ‘A’ is the cross sectional area of the film. The calculated values of A.C. conductivity are presented in Table 1. The ionic conductivity is found to be higher and it is 2.32x10-5 S/cm for the composition of (PVP 80% + CH3COONa 20%) at 373 K. The ionic conductivity increases due to the interlinking of cations with the polymer matrix which reduces the crystalline nature [22]. As a result the mobile charge carriers increase with increasing salt percentage ratio to the host polymer. The semicrystalline nature in the polymer converts the amorphous nature. This denotes the fact the transfer of sodium ions take place freely in the polymer chains which possess the higher ionic conductivity. Table.1 Ionic conductivity of solid polymer electrolytes.
PVP: CH3COONa (95:5)
Conductivity (Scm-1) at RT 373 K 1.02x10-9 1.13x10-8 3.24x10-8 3.12x10-7
PVP: CH3COONa (90:10)
5.32x10-8
5.64x10-7
PVP: CH3COONa (85:15)
3.10x10
-7
2.52x10-6
PVP: CH3COONa (80:20)
5.35x10-7
2.32x10-5
Solid polymer electrolyte films Pure PVP
The real (εl) and imaginary parts (ε11) of dielectric constant with respect to frequency is shown in Fig. 2(a) and Fig. 2(b). From the figures it is clearly observed that the values of real and imaginary parts are continuously decreasing with increase in frequency for a particular time of interval and becomes stabilized due to polarization phenomenon and also observed that the dielectric constant value is found to be high for the sample 80PVP:20 CH3COONa. This may be due to the formation of space charge region at the electrode-electrolyte interfaces [23, 24]. The decrease in dielectric constant is due to the complete miscibility of salt in the host polymer matrix, which in turn the mobilization of ions in the polymer matrix and this lead to the enhancement of electric conductivity [25]. The logarithmic frequency with respect to real (εl) and imaginary parts (ε11) of dielectric constant is shown in Fig. 3(a) and Fig. 3(b). From the figures it is clearly observed that the values of real and imaginary parts are continuously decreasing with increase in the logarithmic frequency and the dielectric values have found to be high for the sample at 20 wt%. This may be due to the mobilization of ions resulting in the formation of electric field at the electrode surfaces [26]. Due to the complete dispersion of salt in the host polymer, the drifting of ions resulting in increase of polarizability at electrodes and is proportional to ωn-1, indicating non-Debye behavior [27, 28].
Fig. 2(a). Variation of εl with frequency for different wt% ratios.
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Fig. 2(b). Variation of ε11 with frequency for different wt% ratios.
Fig. 3(a). Variation of ε1 with logarithmic frequency for different wt% ratios.
Fig. 3(b). Variation of ε1l with logarithmic frequency for different wt% ratios.
M. Seshu Kumar et al./ Materials Today: Proceedings 5 (2018) 26405–26410
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The dielectric values of the logarithmic angular frequency (ω) with respect to real (εl) and imaginary parts (ε11) for different wt% compositional ratios in shown in Fig. 4(a) and Fig. 4(b). From the figures the monotonic decrement in dielectric values has been observed with increase in the logarithmic angular frequency. The decrement of dielectric values may be due to the reduced proportion of amorphous material which leads in the magnitude of dispersion [29]. Similar behavior has been observed in the rest of the samples.
Fig. 4(a). Variation of ε1 with logarithmic angular frequency for different wt% ratios.
The variation between logarithmic conductivity with respect to the frequency is shown in Fig. 5. From the figure it is observed that the ionic conductivity increases as increasing the frequency and the maximum ionic conductivity is found for the compositional ratio 80PVP:20 CH3COONa. The enhancement of ionic conductivity due to the large scale heterogeneity of salt particles doped in the host polymer and the space charge polarization takes place at the electrode-electrolyte interfaces, where the ionic contribution is increased [30, 31].
Fig. 4(b). Variation of ε1l with logarithmic angular frequency for different wt% ratios.
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M. Seshu Kumar et al./ Materials Today: Proceedings 5 (2018) 26405–26410
Fig. 5 Variation of logarithmic conductivity vs frequency for different wt% ratios
4. Conclusions Solid polymer films have been prepared with different wt% ratios of PVP: CH3COONa by solution cast technique. AC-ionic conductivity measurements showed that the higher ionic conductivity was found to be 2.32x10-5 S/cm at higher temperature for the composition 80PVP:20 CH3COONa. Dielectric studies were performed on the prepared solid polymer electrolyte films at room temperature and found that the best optimum conductivity and electric relaxation process exist for the composition 80PVP:20 CH3COONa. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31]
P.V. Wright, Br. Polym. J. 7 (1975) 319. D.E. Fenton, J.M. Parker, P.V. Wright, Polym. 14 (1973) 589. M. B. Armand, Ann. Rev. Mater. Sci. 16 (1986) 245. X. Wang, L. Zhi, K. Muellen, Nano Lett. 8 (2008) 323-327. S. Guo, S. Dong, E. Wang, ACS Nano 4 (2010) 547-555. L. Zhang, G.J. Shi, Phys. Chem. C 115 (2011) 17206-17212. M.C. Rao, R.V.S.S.N. Ravi kumar, Sk. Muntaz Begum, AIP Conf. Proc. 1536 (2013) 27-28. Sk. Muntaz Begum, M.C. Rao, K. Ravindranadh, AIP Conf. Proc. 1349 (2011) 641-642. K. Ravindranadh, M.C. Rao, AIP Conf. Proc. 1536 (2013) 215-216. Sk. Shahenoor Basha, M.C. Rao, J. Inorg. Organomet. Polym. Mater. 27 (2017) 455-466. S. Rajyalakshmi, K. Ramachandra Rao, M.C. Rao, Int. J. ChemTech Res. 9 (1) (2016) 7-14. SK. Shahenoorbasha, K. Vijaya Kumar, M.C. Rao, Rasayan J. Chem. 9 (3) (2016) 348-354. M.S. Sekhawat, K. Ravindranadh, M.C. Rao, AIP Conf. Proc. 1536 (2013) 219-220. SK. Shahenoor Basha, K. Vijaya Kumar, M.C. Rao, Rasayan J. Chem. 9 (2016) 348-354. M.C. Rao and K. Ravindranadh, Mater. Res. Innovations 21(2) (2017) 102-105. Sk. Shahenoor Basha, G. Sunita Sundari, M.C. Rao, Rasayan J. Chem. 10 (2017) 279-285. Sk. Shahenoor Basha, K. Vijaya Kumar, M.C. Rao, J. Polym. Sci. series A 59(4) (2017) 554-565. M.C. Rao, J. Optoelecctron. Biomed. Mater. 5(1) (2013) 9-16. Sk. Shahenoor Basha, B. Ranjit Kumar, M.C. Rao, Rasayan J. Chem. 10 (2017) 1159-1166. K. Ravindranadh, R.V.S.S.N. Ravikumar , M.C. Rao, J. Non Oxide Glasses 5 (2013) 39-45. N. Li, W. Cheng, K. Ren, F. Luo, K. Wang, Q. Fu, Chin. J. Poly. Sci. 31 (2013) 98-109. L. Lin, H. Deng, X. Gao, S. Zhang, E. Bilotti, T. Peijs, Q. Fu, Poly. Int. 62 (2013) 134-140. X. Gao, S. Zhang, F. Mai, L. Lin, Y. Deng, H. Deng, Q. Fu, J. Mater. Chem. 21 (2011) 6401-6408. C.A Di, D.C. Wei, G.Yu, Y.Q. Liu, Y.L. Guo, D.B. Zhu, Adv. Mater. 20 (2008) 3289-3293. M.D. Stoller, S. Park, Y. Zhu, J. An, R.S. Ruoff, Nano Lett. 8 (2008) 3498-3502. X. Yuxi, H. Wenjing, B. Hua, L. Chun, S. Gaoquan, Carbon 47 (2009) 3538-3543. S. Stankovich, D.A. Dikin, R.D. Piner, K.M. Kohlhaas, Y. Jia, Y. Wu, S.T. Nguyen, R.S. Ruoff , Carbon 45 (2007) 1558-1565. Sk. Shahenoor Basha, B. Ranjit Kumar, K. Veera Bhadra Reddy, M.C. Rao, Chem. Sci. Rev. Lett. 6(22) (2017) 832-837. Y. Kojima, A. Usuki, M. Kawasumi, A. Okada, Y. Fukushima, T. Karauchi, O. Kamigaito, J. Poly. Sci. 31 (1993) 1775-1778. S. Morimun, M. Kotera, T. Nishino, K. Goto, K. Hata, J. Macr. Mol. 44 (2011) 4415-4421. T. Tyler, O. Shenderova, G. Cunningham, J. Walsh, J. Drobnik, G. McGuire, Diam. Relat. Mater. 15 (2006) 2078-2081.