rehman2019

Journal Pre-proof
Synthesis of Polyvinyl Acetate /Graphene Nanocomposite and its
Application as an Electrolyte in Dye Sensitized Solar Cells
Shafi ur Rehman, Muhammad Noman, Adnan Daud Khan, Abdul
Saboor, Muhammad Shakeel Ahmad, Hizb Ullah Khan
PII:
S0030-4026(19)31489-5
DOI:
https://doi.org/10.1016/j.ijleo.2019.163591
Reference:
IJLEO 163591
To appear in:
Optik
Received Date:
19 July 2019
Accepted Date:
11 October 2019
Please cite this article as: Rehman Su, Noman M, Khan AD, Saboor A, Ahmad MS, Khan HU,
Synthesis of Polyvinyl Acetate /Graphene Nanocomposite and its Application as an Electrolyte
in Dye Sensitized Solar Cells, Optik (2019), doi: https://doi.org/10.1016/j.ijleo.2019.163591
This is a PDF file of an article that has undergone enhancements after acceptance, such as
the addition of a cover page and metadata, and formatting for readability, but it is not yet the
definitive version of record. This version will undergo additional copyediting, typesetting and
review before it is published in its final form, but we are providing this version to give early
visibility of the article. Please note that, during the production process, errors may be
discovered which could affect the content, and all legal disclaimers that apply to the journal
pertain.
© 2019 Published by Elsevier.
Synthesis of Polyvinyl Acetate /Graphene Nanocomposite and its Application as an
Electrolyte in Dye Sensitized Solar Cells
Shafi ur Rehman1, Muhammad Noman1*, Adnan Daud Khan1, Abdul Saboor3, Muhammad Shakeel Ahmad1 and
Hizb Ullah Khan2
1
of
U.S.-Pakistan Center for Advanced Studies in Energy (USPCAS-E), UET Peshawar.
2
National Center of Excellence in Physical Chemistry, University of Peshawar.
3
National University of Engineering & Technology (NUST), Islamabad, Pakistan.
ro
ABSTRACT
Liquid based electrolytes used in dye synthesized solar cells (DSSCs) have stability issues due to
-p
leakage and volatilization of organic solvents. To overcome this problem, many researchers
focused on alternatives such as solid and gel based electrolytes. However, due to less ionic
conductivity, gel based electrolytes are less efficient as compared to liquid electrolytes. In this
re
work, polyvinyl acetate (PVAc)/graphene nanocomposite based gel electrolyte is synthesized for
the first time using in-situ polymerization technique to enhance the efficiency of the solar cell. The
lP
prepared nanocomposite is characterized by using Fourier-transform infrared spectroscopy (FTIR), X-ray diffractometer (XRD), scanning electron microscopy (SEM) and solar simulator
techniques. The results of the I-V curve revealed the increased photocurrent density (JSC) of the
ur
na
prepared nanocomposite based gel electrolyte as compared to its counterpart. The values for short
circuit photocurrent density (JSC), open circuit voltage (VOC) and fill factor (FF) of the
nanocomposite based gel electrolyte are 6.62 mA cm-2, 0.64 V and 43% respectively, yielding an
overall photovoltaic conversion efficiencies (PCE) of 4.57 %, which is more than the efficiency
(𝜂 = 4.35 %) of referenced PVAc gel electrolyte based DSSC and comparable to the efficiency (𝜂
Jo
= 4.75 %) of liquid electrolyte based DSSC. Finally, Electron impedance spectroscopic studies
have been conducted to understand the electron transfer kinetics.
Keywords: Charge transfer; DSSC; Graphene; nanocomposte; polymer electrolyte.
1
1. INTRODUCTION
Dye sensitized solar cells (DSSCs) are considered one of the best alternative of first generation
silicon solar cells due to their high efficiency, easy fabrication process and low cost [1][2]. Such
type of solar cell is comprised of working electrode sensitized by dye molecules, counter electrode
and electrolyte. The dye is excited by the incident light and the photoexcited electrons are
transferred to the conduction band of the working electrode and finally the dye is oxidized. The
dye is regenerated by the iodide ion (I-) in the redox couple. Subsequently, the triiodide (I3-) ion
of
moves towards the counter electrode and is reduced by receiving electrons from the external
circuit, thus completing the whole cycle. The efficiency of liquid electrolyte based DSSC is as
ro
high as 13% for Cobalt-based electrolyte [3]. But, liquid-based electrolyte has stability issues due
to leakage and evaporation of the organic solvent. Therefore, researchers are extensively working
-p
to find out the alternatives to liquid electrolyte, such as solid electrolyte, which is more stable but
comparatively less efficient. It is found that polymer-based gel electrolyte is the best alternate
re
between liquid and solid electrolytes which improves the life time of DSSC without sacrificing the
efficiency much [4][5][6]. They generally exist in semi-solid state, a state lies between liquid and
lP
solid. Henceforth, polymer-based gel electrolytes capitalize the merits of both liquid electrolyte,
such as high ionic conductivity, and solid electrolyte, such as long-term stability, lower leakage,
and evaporation. So far, many polymers and copolymers, such as polypyrrole, polyacrylonitrile,
ur
na
poly (poly (acrylic acid)-co-ethylene glycol) and poly (acrylic acid), have been used to prepare gel
electrolyte that plays an important role in determining the efficiency of DSSC [7][8][9]. In order
to further improve the conductive nature of polymer and efficiency of gel based electrolytes
nanoparticles such as graphene, CNT’s, Ag, ZnO etc, can be used [4].
Polyvinyl acetate (PVAc) is considered to be one of the good insulating polymer with low
Jo
conductivity and excellent transparency. In common organic solvents PVAc has strong adhesion
and excellent solubility, which thereby decrease the organic solvent content instantaneously. This
behavior assures that the electrolyte is in quasi-solid state and trap the liquid electrolyte in the
polymer matrix, which significantly reduces the risk of leakage and evaporation [8]. Wang et. al.
[10] prepared ionic liquid polymer gel comprised of 1-methyl-3-propylimidazolium iodide
(MPII) and poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF–HFP) used as electrolyte
in DSSC, with 5.3% conversion efficiency at AM 1.5 illumination. Similarly, Chiappone et. al [11]
2
reported sunlight conversion efficiency of 7.03% and 8.25% at simulated light intensities of 1.0
and 0.4 sun respectively, for a quasi-solid electrolyte made of nanoscale micro-fibrillated cellulose
(NMFC).
Carbon based materials, such as CNT’s, graphene, etc. have greater thermal stability due to their
thermally activated carrier hopping associated with defect states [12][13][14][15]. The
experimental discovery of graphene has revived the field of polymer nanocomposites (PNCs)
especially for their electrically conductive nature. The 2-dimensional (2D), sp2 hybridized nature
of
of graphene imparts its zero-bandgap structure to enhance the electrical conductivity and dielectric
characteristics of polymer [16-18]. Kowsari et. al. [19] reported a significant increase in
ro
photovoltaic current density (Jsc) from 7.141 to 16.847 mA cm-1 when functionalized graphene
oxide (GO) is added to ammonium based ionic liquid in DSSC. Under the optimized ratio, liquid
-p
electrolyte showed an increase in conversion efficiency from 3.96% to 8.33%. Also, recently,
Shrivatsav et. al. [20] prepared Quasi-solid state iodide/triiodide redox electrolyte composed of
reduced graphene oxide and poly (methyl methacrylate) (RGO-PMMA) nanocomposites for which
re
the electrical conductivity of PMMA increased from 10-7 to 10-4 S/cm (three orders), by the
addition of 1wt% concentration of graphene. Electrolytes also showed highest power conversion
lP
efficiency of 5.38% and the fill factor of 0.63 for 2% of RGO-PMMA. Lin Liu et. al. [21] prepared
RGO-doped TiO2 photo anode by immersing sintered TiO2 nanofilms in aqueous solution of
graphite oxide. The photoelectric conversion efficiency increased from 6.85% for RGO-doped
ur
na
TiO2, which is 11.7% higher than that of pure TiO2 (P25- TiO2) based DSSC.
In this study, initially polyvinyl acetate (PVAc) is synthesized by free-radical solution
polymerization technique. Subsequently, PVAc/Graphene nanocomposite is prepared with the
help of in-situ polymerization technique [22] and used as polymer matrix in the liquid electrolyte
Jo
for the first time. PVAc is highly soluble in commonly used organic solvents, like 3methoxypropionitrile and acetonitrile, and therefore it prevents the electrolyte leakage and
evaporation. The study shows that PCE of PVAc/graphene nanocomposite based DSSC is
increased as compared to referenced PVAc based DSSC and comparable to pure liquid electrolyte
based DSSC. It is further realized that, due to the presence of graphene, JSC of nanocomposite
based DSSC is increased as compared to its counterparts.
3
2. EXPERIMENTAL
2.1. Materials
Vinyl acetate (VAc) and sodium dodecyl sulphate are provided by Daejung chemicals, Korea.
Potassium per sulphate (K2S2O8) is purchased from Riedel-de-Haen, Czech Republic, and
Dimethyl formamide is received from RCI, Thailand. Test Cell Kit and electrolyte are purchased
of
from Solaronix, Switzerland and then employed in the fabrication of Dye sensitized solar cells.
ro
2.2. Synthesis of PVAc
-p
Polyvinyl acetate is synthesized by free-radical solution polymerization technique in the presence
of initiator, accelerator and surfactant. Concisely, 30 mL of vinyl acetate (VAc) monomer, 0.1g of
sodium dodecyl sulfate as surfactant and certain amount of water is added in a three-neck round
re
bottom flask. A mechanical stirrer is used to stir the mixture for 10 minutes at 30℃. Subsequently,
0.75 g of sodium sulphite (Na2SO3) as accelerator and 0.75 g of potassium persulphate (K2S2O8)
lP
as initiator are mixed with the solution. The temperature of the prepared solution is raised to 80 ℃
ur
na
and stirring is continued till complete polymerization.
2.3. Synthesis of PVAc/Graphene nanocomposite
In-situ polymerization technique is used to prepare PVAc/Graphene nanocomposite. In a typical
procedure, 0.01g of graphene is initially dispersed in dimethyl formamide (DMF) and sonicated
Jo
for 10 minutes. The sonicated mixture is then added with VAc in a glass reactor and placed in a
water tank at 70 ℃ with continuous stirring. Subsequently, 0.75 g of Na2SO3, 0.75 g of K2S2O8
and 0.1g of sodium dodecyl sulphate are introduced to the mixture. The stirring process is
continued till complete polymerization. The prepared composite is dried and stored for further use
as shown in the figure 1.
4
b)
a)
ro
of
Figure 1. The prepared (a) PVAc and (b) PVAc/graphene nanocomposite images.
2.4. Synthesis of gel electrolytes
-p
The prepared liquid electrolyte is consisted of 0.1 M LiI, 0.05 M I2 as redox ions, 0.5 M 4-tertbutyl pyridine as additive and acetonitrile as an organic solvent. Both gel based electrolytes are
re
prepared by adding 0.6 g of PVAc and 0.6 g of PVAc/graphene nanocomposite to 1g of the liquid
ur
na
2.5. Device fabrication
lP
electrolyte and the system was stirred till complete dissolution of the polymer.
The DSSCs were prepared using the paste of TiO2 nanoparticle paste (30nm) as photoanode.
Ru(dcbpy)2(NCS)2 (dcbpy ¼ 2,2-bipyridyl-4,4-dicarboxylato) dye solution (535-bisTBA (N719),
Solaronix) with acetonitrile has been used as active layer. Iodide/triiodide redox, PVA polymer
Jo
and PVA/graphene nanocomposite were used as electrolyte.
3. RESULT AND DISCUSSION
3.1. FT-IR Spectroscopy
FT-IR (IRTracer-100, Shimadzu) is used to find out numerous functional groups present in the
nanocomposite. The prepared polymer and nanocomposite are studied in 400–4000 cm−1 range of
wavelength which is one of the commonly used regions for infrared absorption spectroscopy. The
5
FT-IR spectra of PVAc and PVAc/graphene are shown in figure 2. The PVAc relating frequencies
and their bands are demonstrated in figure 2(a). The peak at 2932 cm-1 shows the stretching
vibration of sp3 hybridized C-H bond [23]. The C=O group is indicated by the intense peak at
1729.8 cm-1, whereas the peaks at 1015 cm-1 and 1227 cm-1 indicate the presence of CH-O and CO-C groups, respectively [24]. The twisting frequencies of O-CO are at 602 cm-1 and 793.7 cm-1.
The feeble absorption band at nearly 3500-3600 cm-1 is due to the stretching vibration of O-H
groups [25].The figure 2(b) demonstrates the FT-IR spectra of PVAc/graphene nanocomposite.
The comparison between PVAc and PVAc/graphene showed appreciable changes and confirmed
of
uniform distribution of graphene in the polymer. The peak at 2927.7 cm-1 represents the CH2
asymmetric stretching vibration of graphene. The peak at 2371.7 cm-1 shows the hydrogen bonding
ro
present in graphene due to -COOH groups. The groups contain oxygen may have presented into
ur
na
3.1. X-Ray Diffraction analysis
lP
re
-p
the sheets of graphene through oxidation [26] [27].
Figure 2. FT-IR Spectrum of (a) PVAc (b) PVAc/Graphene Nanocomposite.
Jo
XRD (JDX-3532, JEOL) technique is used to find out the crystallinity and amorphousness of the
prepared polymer and nanocomposite. Figure 3 demonstrates the XRD analysis of neat PVAc, neat
graphene and PVAc/graphene nanocomposite. There are no sharp peaks found in figure 3(a),
which clearly indicates the amorphous nature of PVAc. For neat graphene, a sharp graphitic peak
appears at 2θ ≈ 26.4o corresponding to (002) crystal plan as shown in figure 3(b) [28]. The intensity
of graphitic peak is rarely visible in the XRD curve of PVAc/graphene nanocomposites as shown
in figure 3(c), inferring its well dispersion in the polymer matrix. The FT-IR and XRD results of
6
PVAc/graphene nanocomposite establishes the fact that graphene has strong secondary bonding
ur
na
lP
re
-p
ro
of
with PVAc polymer matrix, which helps graphene to disperse uniformly.
Figure 3. XRD images of (a) PVAc, (b) graphene and (c) PVAc/graphene nanocomposite.
Jo
3.3. Conductivity curve
The figure 4(a) and (b) indicates the conductivity of the prepared polymer and nanocomposite
respectively. The figure 4(a) shows the conductivity of PVAc as 2.2×10 -3 S/cm at high frequency.
As pure PVAc is less conductive due to low level of protonation of the PVAc chains, the increment
in conductivity with frequency is because of the radiation which caused splitting of the polymer
network. It recommends that the mechanism of conduction is based on electronic jumping and
7
results in the production of high energy free electrons, ions and free radicals [29]. The electrical
conductivity of PVAc/graphene nanocomposite is shown in figure 4(b) which is 5×10 -3 S/cm. The
conductivity of the polymer is improved due to the presence of graphene nanosheets distributed
re
-p
ro
of
uniformly in the polymer matrix.
lP
Figure 4. Conductivity of (a) PVAc and (b) PVAc/graphene nanocomposite
3.4. Scanning Electron Microscopy
ur
na
Scanning electron microscope (JSM-6490, JEOL) is used to analyze the surface morphology and
size of the nanoparticles. Figure 5 indicates SEM images of PVAc and PVAc/Graphene
nanocomposite. For PVAc polymer matrix, SEM image explains the amorphous nature of PVAc.
Jo
A sheet like structure of graphene in figure 5(b) is also evident in PVAc/graphene nanocomposite.
8
The image shows the formation of secondary bond between graphene and polymer matrix, which
in turns uniformly disperse graphene in polymer matrix.
b)
-p
ro
of
a)
re
Figure 5. SEM images of (a) PVAc and (b) PVAc/Graphene nanocomposite.
3.5. Photovoltaic performance
lP
The current-voltage curves measurement for DSSCs are carried out using AAA solar simulator
with Keithley-2400 source-meter. The photovoltaic performance of Liquid, PVAc and
ur
na
PVAc/graphene nanocomposite based electrolytes under one sun illumination (1000 W/m2, AM
1.5G) is shown in figure 6. The values for open circuit voltage (VOC), short circuit current (JSC),
and fill factor (FF) of DSSC are obtained from the corresponding J-V curves. The table 1
summarized the photovoltaic performance of the corresponding DSSCs. The values for JSC, VOC
and FF of DSSC based on liquid electrolyte are 6.37 mA/cm2, 0.64 V, and 0.46 respectively,
Jo
yielding an overall efficiency (𝜂) of 4.75. Whereas, the values for JSC, VOC and FF of DSSC based
on PVAc electrolyte are 6.36 mA/cm2, 0.67 V, and 0.42 respectively, yielding an overall 𝜂 of 4.35.
The Contrast between the data of pure liquid electrolyte and PVAc electrolyte shows a slight
increase in VOC of PVAc electrolyte but decrease in FF which ultimately leads to lesser 𝜂 of PVAc
based DSSC. The values for JSC, VOC and FF of DSSC based on PVAc/graphene electrolyte are
6.62 mA/cm2, 0.64 V, and 0.43 respectively, yielding an overall 𝜂 of 4.57 which is more than the
PVAc and comparable to pure liquid electrolyte. The increase in the JSC of PVAc/graphene as
9
compared to PVAc and pure liquid electrolyte is found due to the presence of graphene which
actually improves the charge transport in the electrolyte.
Table 1. Photovoltaic parameters of liquid, polymer and composite electrolyte
Jsc (mAcm-2)
Voc (V)
FF%
𝜼%
Liquid Electrolyte
6.37
0.64
0.46
4.75
Gel Electrolyte (PVAc)
6.36
0.67
0.42
4.35
Gel Electrolyte (PVAc/graphene)
6.62
0.64
of
Samples
4.57
ur
na
lP
re
-p
ro
0.43
Jo
Figure 6. Photocurrent-voltage curves of DSSC based on liquid electrolyte, PVAc electrolyte
and PVAc/graphene electrolyte
3.6. electron transfer studies
Electron impedance spectroscopy EIS (model: PGSTAT101auto lab) has been employed to
measure charge transfer ability. The frequency range for the experiments was chosen to be 0.1–1
10
MHz and voltage was set to 10 mV. It has been observed that the second semi-circle of polymer
based DSSC is higher than the liquid electrolyte based device. Which clearly indicates that the
electron transfer resistance is more in the polymer based DSSC compared to liquid electrolyte
based counterpart. It has been observed that with the introduction of graphene particles, the second
semi-circle of EIS pattern shifts downward which is due to improved electron transfer
characteristics of graphene present in polymer matrix. It must be mentioned here that due to non-
ur
na
lP
re
-p
ro
of
utilization of spacer between two electrodes the third semi-circle is not clearly visible.
Jo
Figure 7. Electrochemical impedance spectroscopy of specimens along with equivalent circuit
4. Conclusions
The PVAc is prepared by Free-radical solution polymerization technique and PVAc/graphene
nanocomposite is synthesized by using in-situ polymerization technique. The nanocomposite is
characterized by using FT-IR, XRD, SEM and Solar simulator techniques. The substantial peaks
present in the XRD spectrum showed the presence of graphene nanoparticles in polymer matrix,
11
subsequently the SEM images showed the excellent dispersion of graphene sheets in the PVAc.
The employment of graphene in the PVAc matrix improved the electrical conductivity under high
frequency from 2.2×10 -3 S/cm to 5×10 -3 S/cm. The Photovoltaic parameters showed the improved
efficiency of PVAc/graphene nanocomposite as compared to PVAc based DSSC.
of
REFRENCES:
1. O'regan, B. and M. Grätzel, A low-cost, high-efficiency solar cell based on dye-sensitized colloidal
ro
TiO2 films. nature, 1991. 353(6346): p. 737.
2. Grätzel, M. (2009). Recent advances in sensitized mesoscopic solar cells. Accounts of chemical
-p
research, 42(11), 1788-1798.
3. Nazeeruddin, M.K., et al., Combined experimental and DFT-TDDFT computational study of
re
photoelectrochemical cell ruthenium sensitizers. Journal of the American Chemical Society, 2005.
127(48): p. 16835-16847.
lP
4. Bella, F., Sacco, A., Pugliese, D., Laurenti, M., & Bianco, S. (2014). Additives and salts for dyesensitized solar cells electrolytes: what is the best choice? Journal of Power Sources, 264, 333343.
ur
na
5. Papageorgiou, N., Athanassov, Y., Armand, M., Bonho, P., Pettersson, H., Azam, A., & Grätzel, M.
(1996). The performance and stability of ambient temperature molten salts for solar cell
applications. Journal of the Electrochemical Society, 143(10), 3099-3108.
6. Bai, Y., Cao, Y., Zhang, J., Wang, M., Li, R., Wang, P., & Grätzel, M. (2008). High-performance dyesensitized solar cells based on solvent-free electrolytes produced from eutectic melts. Nature
Jo
materials, 7(8), 626.
7. Lan, Z., Wu, J., Hao, S., Lin, J., Huang, M., & Huang, Y. (2009). Template-free synthesis of closedmicroporous hybrid and its application in quasi-solid-state dye-sensitized solar cells. Energy &
environmental science, 2(5), 524-528.
8. Wang, L., et al., Highly stable gel-state dye-sensitized solar cells based on high soluble polyvinyl
acetate. ACS Sustainable Chemistry & Engineering, 2012. 1(2): p. 205-208.
12
9. Su’ait, M.S., M.Y.A. Rahman, and A. Ahmad, Review on polymer electrolyte in dye-sensitized solar
cells (DSSCs). Solar Energy, 2015. 115: p. 452-470.
10. Wang, P., et al., High efficiency dye-sensitized nanocrystalline solar cells based on ionic liquid
polymer gel electrolyte. Chemical Communications, 2002(24): p. 2972-2973.
11. Chiappone, A., et al., Structure–Performance Correlation of Nanocellulose‐Based Polymer
Electrolytes for Efficient Quasi‐solid DSSCs. ChemElectroChem, 2014. 1(8): p. 1350-1358.
12. Huang, X. and P. Jiang, Core–shell structured high‐k polymer nanocomposites for energy storage
and dielectric applications. Advanced Materials, 2015. 27(3): p. 546-554.
of
13. Zhang, L., et al., Preparation and dielectric properties of core–shell structured Ag@
polydopamine/poly (vinylidene fluoride) composites. Composites science and Technology, 2015.
ro
110: p. 126-131.
14. Lu, Z., et al., Graphene, microscale metallic mesh, and transparent dielectric hybrid structure for
-p
excellent transparent electromagnetic interference shielding and absorbing. 2D Materials, 2017.
4(2): p. 025021.
re
15. Khan, M., et al., Investigating mechanical, dielectric, and electromagnetic interference shielding
properties of polymer blends and three component hybrid composites based on polyvinyl alcohol,
polyaniline, and few layer graphene. Polymer Composites, 2018. 39(10): p. 3686-3695.
lP
16. Singh, E. and H.S. Nalwa, Graphene-based dye-sensitized solar cells: a review. Science of advanced
Materials, 2015. 7(10): p. 1863-1912.
17. Zhang, Y., et al., Recent applications of graphene in dye-sensitized solar cells. Current Opinion in
ur
na
Colloid & Interface Science, 2015. 20(5-6): p. 406-415.
18. Khannam, M., et al., A graphene oxide incorporated TiO 2 photoanode for high efficiency quasi
solid state dye sensitized solar cells based on a poly-vinyl alcohol gel electrolyte. RSC Advances,
2016. 6(60): p. 55406-55414.
19. Kowsari, E. and M.R. Chirani, High efficiency dye-sensitized solar cells with tetra alkyl ammonium
Jo
cation-based ionic liquid functionalized graphene oxide as a novel additive in nanocomposite
electrolyte. Carbon, 2017. 118: p. 384-392.
20. Shrivatsav, R., et al., Characterization of poly methyl methaacrylate and reduced graphene oxide
composite for application as electrolyte in dye sensitized solar cells. Materials Research Express,
2018. 5(4): p. 046204.
13
21. Liu, L., et al., A detailed investigation on the performance of dye-sensitized solar cells based on
reduced graphene oxide-doped TiO 2 photoanode. Journal of materials science, 2017. 52(13): p.
8070-8083.
22. Tripathi, S.N., et al., Electrical and mechanical properties of PMMA/reduced graphene oxide
nanocomposites prepared via in situ polymerization. Journal of materials science, 2013. 48(18): p.
6223-6232.
23. Hossain, U.H., T. Seidl, and W. Ensinger, Combined in situ infrared and mass spectrometric analysis
of high-energy heavy ion induced degradation of polyvinyl polymers. Polymer chemistry, 2014.
of
5(3): p. 1001-1012.
24. Jiao, T., et al., Reduced graphene oxide-based silver nanoparticle-containing composite hydrogel
ro
as highly efficient dye catalysts for wastewater treatment. Scientific reports, 2015. 5: p. 11873.
25. Farid, M.M., et al., Molecular imprinting method for fabricating novel glucose sensor: Polyvinyl
-p
acetate electrode reinforced by MnO2/CuO loaded on graphene oxide nanoparticles. Food
chemistry, 2016. 194: p. 61-67.
re
26. Mombeshora, E.T., et al., Multiwalled carbon nanotube-titania nanocomposites: Understanding
nano-structural parameters and functionality in dye-sensitized solar cells. South African Journal of
Chemistry, 2015. 68: p. 153-164.
lP
27. Tang, Z., et al., General route to graphene with liquid-like behavior by non-covalent modification.
Soft Matter, 2012. 8(35): p. 9214-9220.
28. Ding, J., et al., Highly efficient photocatalytic hydrogen evolution of graphene/YInO 3
ur
na
nanocomposites under visible light irradiation. Nanoscale, 2014. 6(4): p. 2299-2306.
29. Fares, S., Frequency dependence of the electrical conductivity and dielectric constants of
polycarbonate (Makrofol-E) film under the effects of γ-radiation. Natural Science, 2011. 3(12): p.
Jo
1034.
14