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Conducting polymers-NiFe2O4 coated on reduced graphene oxide sheets as electromagnetic (EM) wave absorption materials
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Conducting polymers-NiFe2O4 coated on reduced graphene oxide sheets as electromagnetic (EM) wave absorption materials Jing Yan, Ying Huang* , Xuefang Chen, Chao Wei Key Laboratory of Space Applied Physics and Chemistry, Ministry of Education, School of Science, Northwestern Polytechnical University, Xi’an 710072, PR China
A R T I C L E I N F O
Article history: Received 30 July 2016 Received in revised form 18 September 2016 Accepted 19 September 2016 Available online xxx Keywords: Reduced graphene oxide Conducting polymers NiFe2O4 nanoparticles Electromagnetic wave absorption properties
A B S T R A C T
In this work, conducting polymers (polyaniline, polypyrrole and poly (3,4-ethylenedioxythiophene)) and NiFe2O4 coated on Reduced Graphene Oxide Sheets were successfully fabricated by a two-step method. The structure and morphology were characterized by several analytical techniques, including XRD, XPS, Raman, TEM and VSM. The microwave-absorbing properties of the composites were measured by a vector network analyzer. TEM photographs reveal that many NiFe2O4 nanoparticles with the sizes in the range of 5–20 nm firmly attached on the surface of RGO-CPs. The ternary composites have superparamagnetic character due to the presence of NiFe2O4 nanoparticles. The electromagnetic data demonstrates that the combination of graphene with conducting polymers and NiFe2O4 nanoparticles can improve the impedance matching, the 2D-structure RGO with large specific surface area improve the dielectric loss, the presence of CPs coating layer enhances the Debye dipole and dipole polarization enhances the dielectric loss. The maximum reflection loss of RGO-PANI-NiFe2O4, RGO-PPy-NiFe2O4 and RGO-PEDOT-NiFe2O4 are 49.7 dB, 44.8 dB and 45.4 dB, the absorption bandwidths with the reflection losses below 10 dB are 5.3 GHz, 5.3 GHz and 3.7 GHz with a thickness of 2.4 mm, 1.7 mm and 2.0 mm, respectively. Such excellent microwave absorption composites could be used as a new kind of candidate for the new types of microwave absorbing materials. ã 2016 Elsevier B.V. All rights reserved.
1. Introduction With continuing growth of electronic technique, the harm of electromagnetic wave radiation becomes more obvious. Electromagnetic wave irradiation has influenced the operation of electronic devices, not only in environmental pollution, but also being harmful to the health of human beings. Electromagnetic (EM) wave absorption materials have attracted much interest due to the expanded EM interference problems. According to different absorbing mechanism, the absorbing material can be divided into dielectric loss materials like barium titanates [1,2], carbon nanotubes [3,4], conducting polymers [5,6] and magnetic loss materials like ferrites [7,8], nickel [9] cobalt [10]. Graphene, a two-dimensional (2D) single layer of carbon atoms patterned in a hexagonal lattice, has attracted increasing attention for its potential applications due to its outstanding properties. The unique structure of graphene makes it has larger specific surface area, improve its wave absorption performance by promoting the
* Corresponding author. E-mail address: [email protected] (Y. Huang).
electromagnetic scattering and multiple reflections [11–14]. Chemical reduction of graphene oxide (GO) is considered to be an efficient approach to produce graphene on a large scale, and the reduced graphene oxide (RGO) with the residual defects and groups on the surface of RGO may be beneficial for microwave wave absorption. Wang et al. [15] studied the microwave absorption properties of RGO that reducted by hydrazine hydrate. The RGO exhibits microwave absorbing intensity as much as 6.9 dB at 7 GHz, which is not ideal for microwave absorbing materials. Conducting polymers (CPs) have become an expanding research area, polyaniline, polypyrrole and poly (3,4-ethylenedioxythiophene) are three of the most promising conductive polymers with excellent environmental stability, electrochemical activity, and high electrical conductivity, which could be used as microwave absorbing materials [16–20]. Li et al. [21] synthesized PANI nanoparticles by chemical oxidative polymerization method, the microwave absorbability revealed that the maximum reflection loss of PANI was 12.63 dB with a thickness of 2 mm. Ni et al. [22] studied the maximum reflection loss of PEDOT only 24 dB with a thickness of 2 mm, which prove one-component CPs material not the ideal microwave absorbing materials. Spinel ferrites has great saturation magnetization and coercivity, good
http://dx.doi.org/10.1016/j.synthmet.2016.09.018 0379-6779/ã 2016 Elsevier B.V. All rights reserved.
Please cite this article in press as: J. Yan, et al., Conducting polymers-NiFe2O4 coated on reduced graphene oxide sheets as electromagnetic (EM) wave absorption materials, Synthetic Met. (2016), http://dx.doi.org/10.1016/j.synthmet.2016.09.018
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chemical stability and corrosion resistance, larger magnetic permeability in wide frequency range, which can be used as microwave absorbing materials. As one of the most important spinel ferrites, NiFe2O4 has attracted much attention because of the higher magnetic loss and the absorbing mechanism of hysteresis loss, domain-wall resonance and natural resonance [23,24], but single NiFe2O4 nanoparticles easy reunion, and has a higher density, can't meet the requirements of ideal absorbing material. According to the principle of EM energy conversion, in addition to dielectric loss and magnetic loss, a proper matching between the dielectric loss and magnetic loss also determines the reflection and attenuation characteristics of EM absorbers. The composites containing both dielectric materials and magnetic materials has attracted increasing attention for its exhibit good complementarities between dielectric loss and magnetic loss. Adding RGO into the NiFe2O4 nanoparticles [25] or using the CPs coated on NiFe2O4 nanoparticles [26], the composite material not only has magnetic loss of NiFe2O4, but also has dielectric loss of graphene or polyaniline, at the same time, the coupling effect between the two also can further enhance its wave absorption performance. Many studies have been reported, but the focus is mainly on the two component composites. Recently, a novel ternary composite of RGO/CPs/Co3O4 has been synthesized, the results indicate that the RGO/CPs/Co3O4 exhibits excellent electromagnetic absorption properties than RGO, RGO-CPs, CPs-Co3O4. Inspired by this, the incorporation of RGO with CPs (dielectric loss material) and magnetic nanoparticles has great potential for EM microwave absorbing materials. In this work, we prepared the RGO-PANI-NiFe2O4, RGO-PPyNiFe2O4 and RGO-PEDOT-NiFe2O4 composites via a two-step method, in situ polymerization of CPs in the first step and followed by the reduction of graphene oxide and the crystallization of NiFe2O4 particles in the second step, which have the relative complementarities between dielectric loss and magnetic loss. The morphology and structure of the ternary nanocomposites were investigated. The electromagnetic data demonstrates that assynthesized composites display excellent microwave absorption properties. 2. Experimental section 2.1. Preparation of RGO-CPs-NiFe2O4 composites Graphene oxide (GO) was prepared from purified natural graphite by using modified Hummers method [27]. The ternary composites were prepared as illustrated in Fig. 1. Firstly, a certain amount of aniline, pyrrole or 3,4-ethylenedioxythiophene monomer was dissolved in GO (100 mL, 1 mg/mL) solution and stirring for 2 h. After cooling above solution at 0–5 C, 2 mL concentrated H2SO4 and 0.95 g (NH4)2S2O8 (APS) dissolved in deionized water were added. The mixture was stirred overnight and the resulting precipitates were washed with deionized water. Secondly, 0.3 g Ni (NO3)2 6H2O and 0.8 g Fe(NO3)3 9H2O were added in the resulting precipitates under stirring at room temperature for a period of
time, then added excess NH3 H2O to the solution slowly until pH = 11. The mixture was transferred to a Teflon-lined autoclave and maintained at 180 C for 12 h. The composites were washed with deionized water several times and dried at 60 C for 12 h in vacuum. Alkaline solution is selected to accomplish two functions. In the first place, it plays an important role in the formation of NiFe2O4 nanoparticles. In the second place, it can be used as a reducing agent, promoting the reduction reaction of graphene oxide in the solvothermal system, without using reducing agent. 2.2. Characterization X-ray powder diffraction (XRD) was carried out on a D/max-gb diffractometer with Cu Ka radiation in the 2u range from 20 to 85 . The X-ray photoelectron spectroscopy (XPS, Thermal Scientific K Alpha) was performed with a Phoibos 100 spectrometer. The Raman spectroscopy was carried out on a Jobin-Yvon HR800 Raman spectrometer. Transmission electron microscopy (TEM) micrographs were taken using a Tecnai F30 G2 transmission electron microscope, with an accelerating voltage of 200 kv. Magnetization was measured by using a BHV-55 vibrating sample magnetometer (VSM) at room temperature. The electromagnetic parameters were analyzed using a HP8753D vector network analyzer. The samples were prepared by uniformly mixing 50 wt% of the sample with 50 wt% of paraffin wax. 3. Results and discussion Fig. 2 shows XRD patterns of GO (a), RGO (b), RGO-PANINiFe2O4 (c), RGO-PPy-NiFe2O4 (d) and RGO-PEDOT-NiFe2O4 (e). The peak of GO in Fig. 2a at around 9.8 corresponding to (001) crystal plane of carbon. From Fig. 2b, we can seen that the peak of GO at 9.8 disappear entirely by alkaline conditions reduction. The peak of RGO at 24.9 corresponding to (002) crystal plane of carbon, and the broad peak indicate that RGO possess a highly disorderly stacked structure. It can be observed that the diffraction peaks for RGO-PANI-NiFe2O4 (Fig. 2c), RGO-PPy-NiFe2O4 (Fig. 2d) and RGO-PEDOT-NiFe2O4 (Fig. 2e) appearing at 18.5 , 30.3 , 35.7, 39.0 , 43.5 , 54.2 , 57.4 and 63.1 are assigned to reflections from the (111), (220), (311), (222), (400), (422), (511) and (440) planes of cubic spinel (JCPDS card no. 10-0325). In order to check the chemical composition and the structure of RGO-PANI-NiFe2O4, RGO-PPy-NiFe2O4 and RGO-PEDOT-NiFe2O4, the samples are characterized by XPS measurements and the corresponding results are presented in Fig. 3. XPS spectrum of the composites (Fig. S1 of the Supporting information) indicate that the existence of C, N, O, Fe and Ni elements in RGO-PANI-NiFe2O4 and RGO-PPy-NiFe2O4 and C, S, O, Fe and Ni elements in RGOPEDOT-NiFe2O4. N1s of RGO-PANI-NiFe2O4 and RGO-PPy-NiFe2O4 and S 2p XPS spectra of RGO-PEDOT-NiFe2O4 are shown in Fig. 3. For RGO-PANI-NiFe2O4 (Fig. 3a) and RGO-PPy-NiFe2O4 (Fig. 3b), N1s XPS spectra can be deconvoluted into three peaks. The binding energy centered at 398.2 eV is attributed to the quinoid ( N¼)
Fig. 1. Schematic illustration of the preparation process of graphene-conducting polymers-NiFe2O4 composites.
Please cite this article in press as: J. Yan, et al., Conducting polymers-NiFe2O4 coated on reduced graphene oxide sheets as electromagnetic (EM) wave absorption materials, Synthetic Met. (2016), http://dx.doi.org/10.1016/j.synthmet.2016.09.018
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Fig. 2. XRD patterns of GO (a), RGO (b), RGO-PANI-NiFe2O4 (c), RGO-PPy-NiFe2O4 (d) and RGO-PEDOT-NiFe2O4 (e).
for RGO-PANI-NiFe2O4 and RGO-PPy-NiFe2O4, amine nitrogen ( NH ) at 399.2 eV for RGO-PANI-NiFe2O4 and 399.7 eV for RGO-PPy-NiFe2O4, and the peaks at 400.7 and 401.3 eV are assigned to the cationic nitrogen atoms (N+) for RGO-PANI-NiFe2O4 and RGO-PPy-NiFe2O4, respectively [28,29]. The presence of these peaks suggests the formation of doped PANI and PPy. Fig. 3c shows the presence of sulfur spin-split doublet of PEDOT at around 164.0 eV (S2p3/2) and 165.2 eV (S2p1/2) [30]. The higher binding energy doublet at around 168.4 and 169.7 eV would be ascribed to sulfur spin-split coupling from PEDOT+ S2O32 due to the incorporation of S2O32 into PEDOT [31], suggesting the formation of doped PEDOT. Ni 2p XPS spectra of RGO-PANI-NiFe2O4, RGOPPy-NiFe2O4 and RGO-PEDOT-NiFe2O4 (Fig. S2 of the Supporting information) exhibit two peaks at 852.5 and 870.2 eV, which are assigned to the binding energy of Ni 2p 3/2 and Ni 2p 1/2, respectively. Fe 2p XPS spectra of RGO-PANI-NiFe2O4, RGO-PPyNiFe2O4 and RGO-PEDOT-NiFe2O4 (Fig. S3 of the Supporting information) exhibit two peaks at 711.6 and 725.1 eV are ascribed to the characteristic doublets of Fe 2p 3/2 and Fe 2p 1/2, respectively, suggesting the formation of the NiFe2O4 nanoparticles. The Raman spectra of RGO, RGO-PANI, RGO-PANI-NiFe2O4, RGO-PPy, RGO-PPy-NiFe2O4, RGO-PEDOT and RGO-PEDOT-NiFe2O4 are shown in Fig. 4. It can be clearly observed that RGO in Fig. 4a shows two Raman peaks centered at 1347 cm 1 (D band) and 1581 cm 1 (G band). The D band is assigned to the vibrations of sp3 carbon atoms of disordered graphite and the G band is mainly assigned to the in-plane vibration of sp2 carbon atoms in a 2D hexagonal lattice, respectively [32,33]. For RGO-PANI (Fig. b1),
Fig. 3. N1s XPS spectra of RGO-PANI-NiFe2O4 (a) and RGO-PPy-NiFe2O4 (b), S2p XPS spectra of RGO-PEDOT-NiFe2O4 (c).
apart from the D and G bands, the peaks at 1161, 1214 and 1480 cm1 are assigned to C H stretching vibration of the quinoid/phenyl group, the C N stretching vibration of benzenoid ring and the semiquinone radical cation structure of PANI respectively [34]. These peaks illustrate the presence of PANI. For RGO-PPy-NiFe2O4 in Fig. c1, three peaks at 1053, 976 and 921 cm1 are related to the C H inplane deformation, the quinoid polaronic and the bipolaronic structure, respectively [35]. indicating the successful formation of PPy. For RGO-PEDOT (Fig. d1), the bands at 575 and 989 cm1 are assigned to oxyethylene ring deformation, the band at 701 cm1 is related to symmetric C SC deformation and the bands at 1434 and 1515 cm1 are attributed to C¼C stretching, respectively, suggesting the formation of PEDOT [36]. The small red shift or blue shift of RGO-CPs in comparison with the reported data can be due to the p-p interaction of CPs with RGO [37–39]. For RGO-PANI-NiFe2O4 (b2), RGO-PPy-NiFe2O4 (c2) RGO-PEDOT-NiFe2O4 (d2), the peaks centered at 572 and 704 cm1 can be attributed to the A1g vibration mode of NiFe2O4, and the peaks at 493 and 667 cm1 can be attributed to the T2g and Eg vibration modes of NiFe2O4, respectively. These results demonstrate the existence of RGO, CPs and NiFe2O4 in the assynthesized composites. The morphologies of samples were examined by TEM. The morphology and structure of the samples are shown in Fig. 5. As can be seen in Fig. 5a, 5f and 5i, many NiFe2O4 nanoparticles with the sizes in the range of 5–20 nm are dispersed uniformly anchored onto RGO-CPs. CPs is coated on the RGO surface due to the strong
Fig. 4. Raman spectra of RGO (a), RGO-PANI (b1), RGO-PPy (c1), RGO-PEDOT (d1), RGO-PANI-NiFe2O4(b2), RGO-PPy-NiFe2O4 (c2) and RGO-PEDOT-NiFe2O4 (d2).
Please cite this article in press as: J. Yan, et al., Conducting polymers-NiFe2O4 coated on reduced graphene oxide sheets as electromagnetic (EM) wave absorption materials, Synthetic Met. (2016), http://dx.doi.org/10.1016/j.synthmet.2016.09.018
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Fig. 5. TEM images of RGO-PANI-NiFe2O4 (a, b), RGO-PPy-NiFe2O4(d, e), RGO-PEDOT-NiFe2O4 (g, h), HRTEM images of RGO-PANI-NiFe2O4 (c), RGO-PPy-NiFe2O4 (f) and RGOPEDOT-NiFe2O4 (i).
p–p interactions between the CP and the RGO sheets. [37–39] These NiFe2O4 nanoparticles firmly attached on the surface of RGOCPs, its appearance has not changed even after long time of ultrasonic, it indicated that there was a strong interaction between NiFe2O4 nanoparticles and RGO-CPs. Most of NiFe2O4 particles have a cubic geometrical morphology, as indicated by Fig. 5a arrows. The selected-area electron diffraction (SAED) pattern (inset in Fig. 5a, g) show the correspondence of (220), (311), (400), (422), (511) and (440) to the cubic spinel structure [40], indicating that NiFe2O4 particles have high crystallinity. The SAED pattern (inset in Fig. 5b) indicates that RGO-PPy has no obvious crystalline character, which is due to the perfect coverage of PPy. In order to verify the crystalline structure of NiFe2O4 particles, we present the HRTEM image of GN-CPs-NiFe2O4 in Fig. 5c, f, i. Inset in these figures, the crystal lattice fringe with a spacing of 0.25 nm can be assigned to the (311) plane of NiFe2O4, which is consistent with the XRD results. The magnetic property of RGO-CPs-NiFe2O4 is measured with VSM at room temperature and the measurement result is presented in Fig. 6. Graphene and conductive polymers are
nonmagnetic material, NiFe2O4 is magnetic materials, so the composite material of magnetic mainly comes from the NiFe2O4 nanoparticles. From Fig. 6, the significant hysteresis loop of the composites shows no remanence or coercivity, suggesting a superparamagnetic character. The saturation magnetization (Ms) value of RGO-PANI-NiFe2O4, RGO-PPy-NiFe2O4 and RGO-PEDOTNiFe2O4 is 31.1 emu g 1, 31.2 emu g 1 and 31.7 emu g 1, respectively. The value of Ms is smaller than that of NiFe2O4 nanocrystal [21], which is attributed to the existence of nonmagnetic RGO and CPs in the composites. Upon placement of a magnet beside the vial, RGO-CPs-NiFe2O4 nanoparticles were quickly attracted to the side of the vial, leaving the solution transparent (Fig. 6 inset), which suggested the formation of doped magnetic NiFe2O4 nanoparticles. The microwave absorption properties of the composites can be estimated from their dielectric and magnetic properties. The complex permittivity (er = e0 je00 ) and complex permeability (mr = m0 jm00 ) represent electronic and magnetic properties of a material subjected to an electromagnetic field, respectively. The real parts of the permittivity (e0 ) and permeability (m0 ) are
Please cite this article in press as: J. Yan, et al., Conducting polymers-NiFe2O4 coated on reduced graphene oxide sheets as electromagnetic (EM) wave absorption materials, Synthetic Met. (2016), http://dx.doi.org/10.1016/j.synthmet.2016.09.018
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Fig. 6. Magnetization hysteresis loops of RGO-PANI-NiFe2O4, RGO-PPy-NiFe2O4 and RGO-PEDOT-NiFe2O4 measured at room temperature.
associated with energy storage while the imaginary parts (e00 , m00 ) are related to energy dissipation, resulting from conduction loss, resonance and polarization relaxation, etc. [41,42]. To test and better understand the mechanism of the EM absorption, the complex permittivity real part (e0 ), permittivity imaginary part (e00 ), permeability real part (m0 ) and permeability imaginary part (m00 ) of RGO-PANI-NiFe2O4, RGO-PPy-NiFe2O4 and RGO-PEDOTNiFe2O4 are presented in Fig. 7. From Fig. 7a, we can observe that the e0 values of all samples exhibit decline in the frequency range of
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2–18 GHz, the e0 values of RGO-PANI-NiFe2O4 and RGO-PEDOTNiFe2O4 vary from 10 to 4.7 and 10.2 to 4.9 over 2–18 GHz frequency range, respectively, while e0 values of RGO-PPy-NiFe2O4 decrease from 16.7 to 6.4 with several big fluctuations in the 2– 18 GHz range. In Fig. 7b, it can be seen that e00 values of RGO-PPyNiFe2O4 sharply decrease from 11.4 to 12.2 at 2–13.5 GHz, while e00 values of RGO-PANI-NiFe2O4 and RGO-PEDOT-NiFe2O4 varying from 4.2 to 2.2 and 1.9 to 5.1 with several small fluctuations in the 2–18 GHz. The reasons of the e0 and e00 varying with frequency may be attributed to the following two points. Firstly, with an increase in the frequency of external reverse electric field, the induction charge phase of RGO-CPs-NiFe2O4 composite behind the external electric field and results in electromagnetic oscillation [43], the values of e0 and e00 decrease with an increase frequency. Secondly, the dielectric performance of the composites is influenced by the space charge polarization. The space charge polarization is associated with the heterogeneity and present at the interface among the components of the composites. The difference in dielectric constants among the RGO-CPs-NiFe2O4 composite is responsible for the generation of space charge polarization. The space charge polarization decreases with an increase in the frequency, which results in the values of e0 and e00 decrease with an increase in frequency [44] In Fig. 7c, m0 values of all samples exhibit complex variation in the 2–18 GHz range. From Fig. 7d, we can see that m00 values of RGO-PPy-NiFe2O4 exhibit a major peak at 12– 16 GHz and two minor peaks of RGO-PANI-NiFe2O4 and RGOPEDOT-NiFe2O4 at around 14 and 16 GHz. Generally, the magnetic loss of magnetic materials is originated from hysteresis loss,
Fig. 7. The real part (a) and imaginary part (b) of the complex permittivity, the real part (c) and imaginary part (d) of the complex permeability.
Please cite this article in press as: J. Yan, et al., Conducting polymers-NiFe2O4 coated on reduced graphene oxide sheets as electromagnetic (EM) wave absorption materials, Synthetic Met. (2016), http://dx.doi.org/10.1016/j.synthmet.2016.09.018
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Fig. 8. The tand of RGO-PANI-NiFe2O4 (a), RGO-PPy-NiFe2O4 (b) and RGO-PEDOT-NiFe2O4 (c).
domain-wall resonance, eddy current effect, and natural resonance [45] In general, the low m00 values indicate dielectric loss may be the main factor determining the EM wave absorbing performances of composites. To further study the EM absorbing mechanism of the composites, the dielectric loss tangent (tande) and magnetic loss tangent (tandm) of RGO-PANI-NiFe2O4 (a), RGO-PPy-NiFe2O4 (b) and RGO-PEDOT-NiFe2O4 (c) were calculated and are shown in Fig. 8. One of the biggest similarities between the measured three samples is tande curve and tandm is symmetric, When tande reach the maximum, on the contrary, the tandm reach the minimum. As far as we know, RGO-CPs is a typical dielectric loss material, whereas NiFe2O4 nanoparticles have magnetic characteristics,
thus, the composites consisting of RGO-CPs and NiFe2O4 nanoparticles could have better impedance matching between the dielectric loss and the magnetic loss, which suggests they have excellent EM wave absorption properties. From Fig. 8a, we can see that tande and tandm values of RGO-PANI-NiFe2O4 most close to 13 GHz within the band of 13–18 GHz, so the maximum absorption corresponding frequency is likely around 13 GHz. Similarly, we can guess the maximum absorption corresponding frequency of RGOPPy-NiFe2O4 and RGO-PEDOT-NiFe2O4 around 15 GHz. In addition, it also can be found from Fig. 8 that tandm are largely lower than those of tande, indicating that the electromagnetic attenuation mechanism of the ternary composites is mainly dependent on dielectric loss.
Fig. 9. Reflection loss curves of RGO-PANI-NiFe2O4 (a) RGO-PPy-NiFe2O4 (b), RGO-PEDOT-NiFe2O4 (c).
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To clarify the EM absorption properties, reflection losses (RL) are calculated by: Z 1 j RL ðdBÞ ¼ 20 logj in Zin þ 1
Z in ¼
qffiffiffiffiffiffiffiffiffiffiffiffi pffiffiffiffiffiffiffiffiffiffi mr =er tan h½jð2pf d=cÞ er mr
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properties. Hence, the RGO-PANI-NiFe2O4 ternary nanocomposites are promising as the applications of potential microwave absorber materials.
ð1Þ Acknowledgements
ð2Þ
Where Zin is the input impedance of the absorber, c is the velocity of electromagnetic waves in free space, f is the frequency and d is the layer thickness. Absorbing material of excellent performance need in frequency range, the value of RL as small as possible. As can be seen from Fig. 9, the thickness of the absorber has a great influence on the microwave absorbing properties. Fig. 9a demonstrates that the maximum reflection loss of RGO-PANI-NiFe2O4 is 49.7 dB at 12.4 GHz with a thickness of 2.4 mm. When the coating layer thickness goes up to 3.5 mm, the bandwidth less than 10 dB (90% of EM wave absorption) can reach up to 5.3 GHz (from 10.9 to 16.2 GHz). Fig. 9b demonstrates that the maximum reflection loss of RGO-PPy-NiFe2O4 is 44.8 dB at 14.9 GHz with a thickness of 1.7 mm. When the coating layer thickness goes up to 1.7 mm, the bandwidth less than 10 dB can reach up to 5.3 GHz (from 12.8 to 18 GHz). Fig. 9c demonstrates that the maximum reflection loss of RGO-PEDOT-NiFe2O4 is 45.4 dB at 15.6 GHz with a thickness of 2 mm. When the coating layer thickness goes up to 2 mm, the bandwidth less than 10 dB can reach up to 3.7 GHz (from 13.5 to 17.3 GHz). These demonstrate that RGO-CPs-NiFe2O4 have a very excellent ability to absorb EM wave, which might result from three reasons as follows: Firstly, dipole polarizations are presented in NiFe2O4 particles, especially when the size is in nanoscale, the small particle size in our case will increase the dipole polarizations, which can be contributed to the dielectric loss, Secondly, the 2Dstructure RGO with large specific surface area can form a complete conductive network, which can improve the dielectric loss. The absence of structure and residual functional groups on the surface of RGO can improve the matching characteristics, moreover, the presence of CPs coating layer enhances the Debye dipole [46] relaxation of RGO, the conjugated electron clouds of CPs molecular chains are transferred to RGO by electronic polarization to form electron tunneling between CPs and RGO, which has the tunnel effect and enhances the absorption of RGO-CPs-NiFe2O4 composites for electromagnetic wave. Thirdly, apart from dielectric loss and magnetic loss, another important concept relating to excellent microwave absorption is strongly dependent on the efficient complementarities between the relative permittivity and permeability. RGO and CPs are dielectric loss absorbents, NiFe2O4 particles have prominent magnetic characteristics, the impedance matching between RGO-CPs and NiFe2O4 particles would play an important role in increasing the electromagnetic absorption properties. 4. Conclusions In summary, conducting polymers (polyaniline, polypyrrole and poly (3,4-ethylenedioxythiophene)) and NiFe2O4 coated on Reduced Graphene Oxide Sheets were successfully fabricated by a two-step method. We found that RGO-CPs-NiFe2O4 ternary composites exhibit excellent microwave absorption properties. The maximum reflection loss of RGO-PANI-NiFe2O4, RGO-PPyNiFe2O4 and RGO-PEDOT-NiFe2O4 are 49.7 dB, 44.8 dB and 45.4 dB, the absorption bandwidths with the reflection losses below 10 dB are 5.3 GHz, 5.3 GHz and 3.7 GHz with a thickness of 2.4 mm, 1.7 mm and 2.0 mm, respectively. The impedance matching between RGO-CPs and NiFe2O4 particles would play an important role in increasing the electromagnetic absorption
This work was financially supported by the Spaceflight Foundation of China (No. 2014-HT-XGD), the Spaceflight Innovation Foundation of China (No. 2014KC11023) and the fundamental Research Funds for the Central Universities (No. 3102016QD021). Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.synthmet.2016. 09.018. References [1] F. Xia, J. Liu, D. Gu, Microwave absorption enhancement and electron microscopy characterization of BaTiO3 nano-torus, Nanoscale 3 (2011) 3860– 3867. [2] Sonai, M. Chandrasekhar, P. Kumar, Microwave sintered sol–gel derived BaTiO3, and Ba0.95La0.05TiO3, ceramic samples for capacitor applications, Ceram. Int. 42 (2016) 10587–10592. [3] X. Lu, Y. Wu, H. Cai, X. Qu, L. Ni, Fe3O4 nanopearl decorated carbon nanotubes stemming from carbon onions with self-cleaning and microwave absorption properties, RSC Adv. 5 (2015) 54175–54181. [4] Z. Ye, Z. Li, J.A. Roberts, P. Zhang, Electromagnetic wave absorption properties of carbon nanotubes-epoxy composites at microwave frequencies, J. Appl. Phys. 108 (2010) 054315–054315-7. [5] M. Fan, Z. He, H. Pang, Microwave absorption enhancement of CIP/PANI composites, Synth. Met. 166 (2013) 1–6. [6] K. Lakshmi, H. John, K.T. Mathew, R. Joseph, K.E. George, Microwave absorption, reflection and EMI shielding of PU–PANI composite, Acta Mater. 57 (2009) 371–375. [7] Z.X. Yu, Z.P. Yao, N. Zhang, Z. Wang, C. Li, Electric field-induced synthesis of dendritic nanostructureda-Fe for electromagnetic absorption application, J. Mater. Chem. A 1 (2013) 4571–4576. [8] X. Zhan, H. Tang, Y. Du, A. Talbi, J. Zha, Facile preparation of Fe nanochains and their electromagnetic properties, RSC Adv. 3 (2013) 15966–15970. [9] B. Gao, L. Qiao, J. Wang, Q. Liu, F. Li, Microwave absorption properties of the Ni nanowires composite, J. Phys. D: Appl. Phys. 41 (2008) 3850–3856. [10] C. Wang, S. Hu, X. Han, W. Huang, L. Tian, Controlled synthesis and microwave absorption property of chain-like co flower, PLoS One 8 (2013) 396–396. [11] S. Stankovich, D.A. Dikin, G.H.B. Dommett, K.M. Kohlhaas, E.J. Zimney, E.A. Stach, Graphene-based composite materials, Nature 442 (2006) 282–286. [12] C. Lee, X. Wei, J.W. Kysar, J. Hone, Measurement of the elastic properties and intrinsic strength of monolayer graphene, Science 321 (2008) 385–388. [13] A.A. Balandin, S. Ghosh, W. Bao, I. Calizo, D. Teweldebrhan, Superior thermal conductivity of single-layer graphene, Nano Lett. 8 (2008) 902–907. [14] Y. Zhao, X. Li, B. Yan, D. Li, S. Lawesb, X. Sun, Significant impact of 2D graphene nanosheets on large volume change tin-based anodes in lithium-ion batteries: a review, J. Power Sources 274 (2014) 869–884. [15] C. Wang, X. Han, P. Xu, X. Zhang, Y. Du, The electromagnetic property of chemically reduced graphene oxide and its application as microwave absorbing material, Appl. Phys. Lett. 98 (2011) 975–980. [16] P. Xu, X. Han, C. Wang, H. Zhao, J. Wang, Synthesis of electromagnetic functionalized barium ferrite nanoparticles embedded in polypyrrole, J. Phys. Chem. B 112 (2008) 2775–2781. [17] L.C. Li, C. Xiang, X.X. Liang, Zn0.6Cu0.4Cr0.5Fe1.46Sm0.04O4 ferrite and its nanocomposites with polyaniline and polypyrrole: preparation and electromagnetic properties, Synth. Met. 160 (2010) 28–34. [18] Z. Su, L. Wang, Y. Li, H. Zhao, B. Chu, Ultraviolet-ozone-treated PEDOT:PSS as anode buffer layer for organic solar cells, Nanoscale Res. Lett. 7 (2012) 1–6. [19] Z.A. King, C.M. Shaw, S.A. Spanninga, D.C. Martin, Structural chemical and electrochemical characterization of poly(3,4-ethylenedioxythiophene) (PEDOT) prepared with various counter-ions and heat treatment, Polymer 52 (2011) 1302–1308. [20] F. Zhao, Z. Wang, J. Zhang, X. Zhu, Y. Zhang, Self-doped and crown-ether functionalized fullerene as cathode buffer layer for highly-efficient inverted polymer solar cells, Adv. Energy Mater. 6 (2016) 1502120. [21] D.G. Li, W.H. Lu, C. Chen, W. Rao, Y.H. Xiong, Synthesis and microwave absorption characteristics of polyaniline, Appl. Mech. Mater. 327 (2013) 53–57. [22] X.W. Ni, X.J. Hu, S.Y. Zhou, C.H. Sun, X.X. Bai, P. Chen, Synthesis and microwave absorbing proper ties of poly(3,4-ethylenediox ythiophene) (PEDOT) microspheres, Polym. Adv. Technol. 22 (2011) 532–537. [23] W. Zhu, L. Wang, R. Zhao, J. Ren, G. Lu, Electromagnetic and microwaveabsorbing properties of magnetic nickel ferrite nanocrystals, Nanoscale 3 (2011) 2862–2864.
Please cite this article in press as: J. Yan, et al., Conducting polymers-NiFe2O4 coated on reduced graphene oxide sheets as electromagnetic (EM) wave absorption materials, Synthetic Met. (2016), http://dx.doi.org/10.1016/j.synthmet.2016.09.018
G Model SYNMET 15455 No. of Pages 8
8
J. Yan et al. / Synthetic Metals xxx (2016) xxx–xxx
[24] X. Gu, W. Zhu, C. Jia, R. Zhao, W. Schmidt, Synthesis and microwave absorbing properties of highly ordered mesoporous crystalline NiFe2O4, Chem. Commun. 47 (2011) 5337–5339. [25] M. Fu, Q. Jiao, Y. Zhao, Preparation of NiFe2O4 nanorod-graphene composites via an ionic liquid assisted one-step hydrothermal approach and their microwave absorbing properties, J. Mater. Chem. A 1 (2013) 5577–5586. [26] T. Wei, Y. Liu, W. Dong, Y. Zhang, C. Huang, Surface-dependent localized surface plasmon resonances in CuS nanodisks, ACS Appl. Mater. Interfaces 5 (2013) 10473–10477. [27] W.S. Hummers, R.E. Offeman, Preparation of graphitic oxide, J. Am. Chem. Soc. 80 (1958) 1339–1339. [28] R. Liang, H. Cao, D. Qian, J. Zhang, M. Qu, Designed synthesis of SnO2polyaniline-reduced graphene oxide nanocomposites as an anode material for lithium-ion batteries, J. Mater. Chem. 21 (2011) 17654–17657. [29] H. Wang, E. Zhu, J. Yang, P. Zhou, D. Sun, Bacterial cellulose nanofibersupported polyaniline nanocomposites with flake-shaped morphology as supercapacitor electrodes, J. Phys. Chem. C 116 (2012) 13013–13019. [30] S.A. Spanninga, D.C. Martin, Z. Chen, X-ray photoelectron spectroscopy study of counterion incorporation in poly(3,4-ethylenedioxythiophene), J. Phys. Chem. C 113 (2009) 5585–5592. [31] S. Lee, K.K. Gleason, Enhanced optical property with tunable band gap of crosslinked PEDOT copolymers via oxidative chemical vapor deposition, Adv. Funct. Mater. 25 (2015) 85–93. [32] Z. Jin, J. Yao, C. Kittrell, J.M. Tour, Large-scale growth and characterizations of nitrogen-doped monolayer graphene sheets, ACS Nano 5 (2011) 4112– 4117. [33] W. Chen, S. Li, C. Chen, L. Yan, Self-assembly and embedding of nanoparticles by in situ reduced graphene for preparation of a 3D graphene/nanoparticle aerogel, Adv. Mater. 23 (2011) 5679–5683. [34] M. Xue, F. Li, J. Zhu, H. Song, M. Zhang, Structure-based enhanced capacitance: in situ growth of highly ordered polyaniline nanorods on reduced graphene oxide patterns, Adv. Funct. Mater. 22 (2012) 1284–1290. [35] P.B. Liu, Y. Huan, X. Zhang, Enhanced electromagnetic absorption properties of reduced graphene oxide–polypyrrole with NiFe2O4 particles prepared with simple hydrothermal method, Mater. Lett. 120 (2014) 143–146.
[36] A. Schaarschmidt, A.A. Farah, A. Aby, A.S. Helmy, Influence of nonadiabatic annealing on the morphology and molecular structure of PEDOT-PSS films, J. Phys. Chem. B 113 (2009) 9352–9355. [37] Q. Yao, L. Chen, W. Zhang, S. Liufu, X. Chen, Enhanced thermoelectric performance of single-walled carbon nanotubes/polyaniline hybrid nanocomposites, ACS Nano 4 (2010) 2445–2451. [38] K.S. Choi, F. Liu, J.S. Choi, T.S. Seo, Fabrication of free-standing multilayered graphene and poly(3,4-ethylenedioxythiophene) composite films with enhanced conductive and mechanical properties, Langmuir 26 (2010) 12902– 12908. [39] J. Zhang, X.S. Zhao, Conducting polymers directly coated on reduced graphene oxide sheets as high-performance supercapacitor electrodes, J. Phys. Chem. C 116 (2012) 5420–5426. [40] P. Sivakumar, R. Ramesh, A. Ramanand, S. Ponnusamy, C. Muthamizhchelvan, Synthesis and characterization of NiFe2O4, nanoparticles and nanorods, J. Alloys Compd. 563 (2013) 6–11. [41] Z. Liu, G. Xu, M. Zhang, K. Xiong, P. Meng, Synthesis of CoFe2O4/RGO nanocomposites by click chemistry and electromagnetic wave absorption properties, J. Mater. Sci. Mater. Electron. (2016) 1–8. [42] P.B. Liu, Y. Huang, J. Yan, Magnetic graphene@PANI@porous TiO2 ternary composites for high-performance electromagnetic wave absorption, J. Mater. Chem. C 4 (2016). [43] V. Panwar, R.M. Mehra, Analysis of electrical, dielectric, and electromagnetic interference shielding behavior of graphite filled high density polyethylene composites, Polym. Eng. Sci. 48 (2008) 2178–2187. [44] K. Singh, A. Ohlan, V.H. Pham, R.B.S. Varshney, Nanostructured graphene/Fe3O4 incorporated polyaniline as a high performance shield against electromagnetic pollution, Nanoscale 5 (2013) 2411–2420. [45] L. Yan, J. Wang, X. Han, Y. Ren, Q. Liu, Enhanced microwave absorption of Fe nanoflakes after coating with SiO2 nanoshell, Nanotechnology 21 (2010) 95708–95712. [46] M.S. Cao, J. Yang, W.L. Song, D.Q. Zhang, B. Wen, Ferroferric oxide/multiwalled carbon nanotube vs polyaniline/ferroferric oxide/multiwalled carbon nanotube multiheterostructures for highly effective microwave absorption, ACS Appl. Mater. Interfaces 4 (2012) 6949–6956.
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Conducting polymers-NiFe2O4 coated on reduced graphene oxide sheets as electromagnetic (EM) wave absorption materials Jing Yan, Ying Huang* , Xuefang Chen, Chao Wei Key Laboratory of Space Applied Physics and Chemistry, Ministry of Education, School of Science, Northwestern Polytechnical University, Xi’an 710072, PR China
A R T I C L E I N F O
Article history: Received 30 July 2016 Received in revised form 18 September 2016 Accepted 19 September 2016 Available online xxx Keywords: Reduced graphene oxide Conducting polymers NiFe2O4 nanoparticles Electromagnetic wave absorption properties
A B S T R A C T
In this work, conducting polymers (polyaniline, polypyrrole and poly (3,4-ethylenedioxythiophene)) and NiFe2O4 coated on Reduced Graphene Oxide Sheets were successfully fabricated by a two-step method. The structure and morphology were characterized by several analytical techniques, including XRD, XPS, Raman, TEM and VSM. The microwave-absorbing properties of the composites were measured by a vector network analyzer. TEM photographs reveal that many NiFe2O4 nanoparticles with the sizes in the range of 5–20 nm firmly attached on the surface of RGO-CPs. The ternary composites have superparamagnetic character due to the presence of NiFe2O4 nanoparticles. The electromagnetic data demonstrates that the combination of graphene with conducting polymers and NiFe2O4 nanoparticles can improve the impedance matching, the 2D-structure RGO with large specific surface area improve the dielectric loss, the presence of CPs coating layer enhances the Debye dipole and dipole polarization enhances the dielectric loss. The maximum reflection loss of RGO-PANI-NiFe2O4, RGO-PPy-NiFe2O4 and RGO-PEDOT-NiFe2O4 are 49.7 dB, 44.8 dB and 45.4 dB, the absorption bandwidths with the reflection losses below 10 dB are 5.3 GHz, 5.3 GHz and 3.7 GHz with a thickness of 2.4 mm, 1.7 mm and 2.0 mm, respectively. Such excellent microwave absorption composites could be used as a new kind of candidate for the new types of microwave absorbing materials. ã 2016 Elsevier B.V. All rights reserved.
1. Introduction With continuing growth of electronic technique, the harm of electromagnetic wave radiation becomes more obvious. Electromagnetic wave irradiation has influenced the operation of electronic devices, not only in environmental pollution, but also being harmful to the health of human beings. Electromagnetic (EM) wave absorption materials have attracted much interest due to the expanded EM interference problems. According to different absorbing mechanism, the absorbing material can be divided into dielectric loss materials like barium titanates [1,2], carbon nanotubes [3,4], conducting polymers [5,6] and magnetic loss materials like ferrites [7,8], nickel [9] cobalt [10]. Graphene, a two-dimensional (2D) single layer of carbon atoms patterned in a hexagonal lattice, has attracted increasing attention for its potential applications due to its outstanding properties. The unique structure of graphene makes it has larger specific surface area, improve its wave absorption performance by promoting the
* Corresponding author. E-mail address: [email protected] (Y. Huang).
electromagnetic scattering and multiple reflections [11–14]. Chemical reduction of graphene oxide (GO) is considered to be an efficient approach to produce graphene on a large scale, and the reduced graphene oxide (RGO) with the residual defects and groups on the surface of RGO may be beneficial for microwave wave absorption. Wang et al. [15] studied the microwave absorption properties of RGO that reducted by hydrazine hydrate. The RGO exhibits microwave absorbing intensity as much as 6.9 dB at 7 GHz, which is not ideal for microwave absorbing materials. Conducting polymers (CPs) have become an expanding research area, polyaniline, polypyrrole and poly (3,4-ethylenedioxythiophene) are three of the most promising conductive polymers with excellent environmental stability, electrochemical activity, and high electrical conductivity, which could be used as microwave absorbing materials [16–20]. Li et al. [21] synthesized PANI nanoparticles by chemical oxidative polymerization method, the microwave absorbability revealed that the maximum reflection loss of PANI was 12.63 dB with a thickness of 2 mm. Ni et al. [22] studied the maximum reflection loss of PEDOT only 24 dB with a thickness of 2 mm, which prove one-component CPs material not the ideal microwave absorbing materials. Spinel ferrites has great saturation magnetization and coercivity, good
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chemical stability and corrosion resistance, larger magnetic permeability in wide frequency range, which can be used as microwave absorbing materials. As one of the most important spinel ferrites, NiFe2O4 has attracted much attention because of the higher magnetic loss and the absorbing mechanism of hysteresis loss, domain-wall resonance and natural resonance [23,24], but single NiFe2O4 nanoparticles easy reunion, and has a higher density, can't meet the requirements of ideal absorbing material. According to the principle of EM energy conversion, in addition to dielectric loss and magnetic loss, a proper matching between the dielectric loss and magnetic loss also determines the reflection and attenuation characteristics of EM absorbers. The composites containing both dielectric materials and magnetic materials has attracted increasing attention for its exhibit good complementarities between dielectric loss and magnetic loss. Adding RGO into the NiFe2O4 nanoparticles [25] or using the CPs coated on NiFe2O4 nanoparticles [26], the composite material not only has magnetic loss of NiFe2O4, but also has dielectric loss of graphene or polyaniline, at the same time, the coupling effect between the two also can further enhance its wave absorption performance. Many studies have been reported, but the focus is mainly on the two component composites. Recently, a novel ternary composite of RGO/CPs/Co3O4 has been synthesized, the results indicate that the RGO/CPs/Co3O4 exhibits excellent electromagnetic absorption properties than RGO, RGO-CPs, CPs-Co3O4. Inspired by this, the incorporation of RGO with CPs (dielectric loss material) and magnetic nanoparticles has great potential for EM microwave absorbing materials. In this work, we prepared the RGO-PANI-NiFe2O4, RGO-PPyNiFe2O4 and RGO-PEDOT-NiFe2O4 composites via a two-step method, in situ polymerization of CPs in the first step and followed by the reduction of graphene oxide and the crystallization of NiFe2O4 particles in the second step, which have the relative complementarities between dielectric loss and magnetic loss. The morphology and structure of the ternary nanocomposites were investigated. The electromagnetic data demonstrates that assynthesized composites display excellent microwave absorption properties. 2. Experimental section 2.1. Preparation of RGO-CPs-NiFe2O4 composites Graphene oxide (GO) was prepared from purified natural graphite by using modified Hummers method [27]. The ternary composites were prepared as illustrated in Fig. 1. Firstly, a certain amount of aniline, pyrrole or 3,4-ethylenedioxythiophene monomer was dissolved in GO (100 mL, 1 mg/mL) solution and stirring for 2 h. After cooling above solution at 0–5 C, 2 mL concentrated H2SO4 and 0.95 g (NH4)2S2O8 (APS) dissolved in deionized water were added. The mixture was stirred overnight and the resulting precipitates were washed with deionized water. Secondly, 0.3 g Ni (NO3)2 6H2O and 0.8 g Fe(NO3)3 9H2O were added in the resulting precipitates under stirring at room temperature for a period of
time, then added excess NH3 H2O to the solution slowly until pH = 11. The mixture was transferred to a Teflon-lined autoclave and maintained at 180 C for 12 h. The composites were washed with deionized water several times and dried at 60 C for 12 h in vacuum. Alkaline solution is selected to accomplish two functions. In the first place, it plays an important role in the formation of NiFe2O4 nanoparticles. In the second place, it can be used as a reducing agent, promoting the reduction reaction of graphene oxide in the solvothermal system, without using reducing agent. 2.2. Characterization X-ray powder diffraction (XRD) was carried out on a D/max-gb diffractometer with Cu Ka radiation in the 2u range from 20 to 85 . The X-ray photoelectron spectroscopy (XPS, Thermal Scientific K Alpha) was performed with a Phoibos 100 spectrometer. The Raman spectroscopy was carried out on a Jobin-Yvon HR800 Raman spectrometer. Transmission electron microscopy (TEM) micrographs were taken using a Tecnai F30 G2 transmission electron microscope, with an accelerating voltage of 200 kv. Magnetization was measured by using a BHV-55 vibrating sample magnetometer (VSM) at room temperature. The electromagnetic parameters were analyzed using a HP8753D vector network analyzer. The samples were prepared by uniformly mixing 50 wt% of the sample with 50 wt% of paraffin wax. 3. Results and discussion Fig. 2 shows XRD patterns of GO (a), RGO (b), RGO-PANINiFe2O4 (c), RGO-PPy-NiFe2O4 (d) and RGO-PEDOT-NiFe2O4 (e). The peak of GO in Fig. 2a at around 9.8 corresponding to (001) crystal plane of carbon. From Fig. 2b, we can seen that the peak of GO at 9.8 disappear entirely by alkaline conditions reduction. The peak of RGO at 24.9 corresponding to (002) crystal plane of carbon, and the broad peak indicate that RGO possess a highly disorderly stacked structure. It can be observed that the diffraction peaks for RGO-PANI-NiFe2O4 (Fig. 2c), RGO-PPy-NiFe2O4 (Fig. 2d) and RGO-PEDOT-NiFe2O4 (Fig. 2e) appearing at 18.5 , 30.3 , 35.7, 39.0 , 43.5 , 54.2 , 57.4 and 63.1 are assigned to reflections from the (111), (220), (311), (222), (400), (422), (511) and (440) planes of cubic spinel (JCPDS card no. 10-0325). In order to check the chemical composition and the structure of RGO-PANI-NiFe2O4, RGO-PPy-NiFe2O4 and RGO-PEDOT-NiFe2O4, the samples are characterized by XPS measurements and the corresponding results are presented in Fig. 3. XPS spectrum of the composites (Fig. S1 of the Supporting information) indicate that the existence of C, N, O, Fe and Ni elements in RGO-PANI-NiFe2O4 and RGO-PPy-NiFe2O4 and C, S, O, Fe and Ni elements in RGOPEDOT-NiFe2O4. N1s of RGO-PANI-NiFe2O4 and RGO-PPy-NiFe2O4 and S 2p XPS spectra of RGO-PEDOT-NiFe2O4 are shown in Fig. 3. For RGO-PANI-NiFe2O4 (Fig. 3a) and RGO-PPy-NiFe2O4 (Fig. 3b), N1s XPS spectra can be deconvoluted into three peaks. The binding energy centered at 398.2 eV is attributed to the quinoid ( N¼)
Fig. 1. Schematic illustration of the preparation process of graphene-conducting polymers-NiFe2O4 composites.
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Fig. 2. XRD patterns of GO (a), RGO (b), RGO-PANI-NiFe2O4 (c), RGO-PPy-NiFe2O4 (d) and RGO-PEDOT-NiFe2O4 (e).
for RGO-PANI-NiFe2O4 and RGO-PPy-NiFe2O4, amine nitrogen ( NH ) at 399.2 eV for RGO-PANI-NiFe2O4 and 399.7 eV for RGO-PPy-NiFe2O4, and the peaks at 400.7 and 401.3 eV are assigned to the cationic nitrogen atoms (N+) for RGO-PANI-NiFe2O4 and RGO-PPy-NiFe2O4, respectively [28,29]. The presence of these peaks suggests the formation of doped PANI and PPy. Fig. 3c shows the presence of sulfur spin-split doublet of PEDOT at around 164.0 eV (S2p3/2) and 165.2 eV (S2p1/2) [30]. The higher binding energy doublet at around 168.4 and 169.7 eV would be ascribed to sulfur spin-split coupling from PEDOT+ S2O32 due to the incorporation of S2O32 into PEDOT [31], suggesting the formation of doped PEDOT. Ni 2p XPS spectra of RGO-PANI-NiFe2O4, RGOPPy-NiFe2O4 and RGO-PEDOT-NiFe2O4 (Fig. S2 of the Supporting information) exhibit two peaks at 852.5 and 870.2 eV, which are assigned to the binding energy of Ni 2p 3/2 and Ni 2p 1/2, respectively. Fe 2p XPS spectra of RGO-PANI-NiFe2O4, RGO-PPyNiFe2O4 and RGO-PEDOT-NiFe2O4 (Fig. S3 of the Supporting information) exhibit two peaks at 711.6 and 725.1 eV are ascribed to the characteristic doublets of Fe 2p 3/2 and Fe 2p 1/2, respectively, suggesting the formation of the NiFe2O4 nanoparticles. The Raman spectra of RGO, RGO-PANI, RGO-PANI-NiFe2O4, RGO-PPy, RGO-PPy-NiFe2O4, RGO-PEDOT and RGO-PEDOT-NiFe2O4 are shown in Fig. 4. It can be clearly observed that RGO in Fig. 4a shows two Raman peaks centered at 1347 cm 1 (D band) and 1581 cm 1 (G band). The D band is assigned to the vibrations of sp3 carbon atoms of disordered graphite and the G band is mainly assigned to the in-plane vibration of sp2 carbon atoms in a 2D hexagonal lattice, respectively [32,33]. For RGO-PANI (Fig. b1),
Fig. 3. N1s XPS spectra of RGO-PANI-NiFe2O4 (a) and RGO-PPy-NiFe2O4 (b), S2p XPS spectra of RGO-PEDOT-NiFe2O4 (c).
apart from the D and G bands, the peaks at 1161, 1214 and 1480 cm1 are assigned to C H stretching vibration of the quinoid/phenyl group, the C N stretching vibration of benzenoid ring and the semiquinone radical cation structure of PANI respectively [34]. These peaks illustrate the presence of PANI. For RGO-PPy-NiFe2O4 in Fig. c1, three peaks at 1053, 976 and 921 cm1 are related to the C H inplane deformation, the quinoid polaronic and the bipolaronic structure, respectively [35]. indicating the successful formation of PPy. For RGO-PEDOT (Fig. d1), the bands at 575 and 989 cm1 are assigned to oxyethylene ring deformation, the band at 701 cm1 is related to symmetric C SC deformation and the bands at 1434 and 1515 cm1 are attributed to C¼C stretching, respectively, suggesting the formation of PEDOT [36]. The small red shift or blue shift of RGO-CPs in comparison with the reported data can be due to the p-p interaction of CPs with RGO [37–39]. For RGO-PANI-NiFe2O4 (b2), RGO-PPy-NiFe2O4 (c2) RGO-PEDOT-NiFe2O4 (d2), the peaks centered at 572 and 704 cm1 can be attributed to the A1g vibration mode of NiFe2O4, and the peaks at 493 and 667 cm1 can be attributed to the T2g and Eg vibration modes of NiFe2O4, respectively. These results demonstrate the existence of RGO, CPs and NiFe2O4 in the assynthesized composites. The morphologies of samples were examined by TEM. The morphology and structure of the samples are shown in Fig. 5. As can be seen in Fig. 5a, 5f and 5i, many NiFe2O4 nanoparticles with the sizes in the range of 5–20 nm are dispersed uniformly anchored onto RGO-CPs. CPs is coated on the RGO surface due to the strong
Fig. 4. Raman spectra of RGO (a), RGO-PANI (b1), RGO-PPy (c1), RGO-PEDOT (d1), RGO-PANI-NiFe2O4(b2), RGO-PPy-NiFe2O4 (c2) and RGO-PEDOT-NiFe2O4 (d2).
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Fig. 5. TEM images of RGO-PANI-NiFe2O4 (a, b), RGO-PPy-NiFe2O4(d, e), RGO-PEDOT-NiFe2O4 (g, h), HRTEM images of RGO-PANI-NiFe2O4 (c), RGO-PPy-NiFe2O4 (f) and RGOPEDOT-NiFe2O4 (i).
p–p interactions between the CP and the RGO sheets. [37–39] These NiFe2O4 nanoparticles firmly attached on the surface of RGOCPs, its appearance has not changed even after long time of ultrasonic, it indicated that there was a strong interaction between NiFe2O4 nanoparticles and RGO-CPs. Most of NiFe2O4 particles have a cubic geometrical morphology, as indicated by Fig. 5a arrows. The selected-area electron diffraction (SAED) pattern (inset in Fig. 5a, g) show the correspondence of (220), (311), (400), (422), (511) and (440) to the cubic spinel structure [40], indicating that NiFe2O4 particles have high crystallinity. The SAED pattern (inset in Fig. 5b) indicates that RGO-PPy has no obvious crystalline character, which is due to the perfect coverage of PPy. In order to verify the crystalline structure of NiFe2O4 particles, we present the HRTEM image of GN-CPs-NiFe2O4 in Fig. 5c, f, i. Inset in these figures, the crystal lattice fringe with a spacing of 0.25 nm can be assigned to the (311) plane of NiFe2O4, which is consistent with the XRD results. The magnetic property of RGO-CPs-NiFe2O4 is measured with VSM at room temperature and the measurement result is presented in Fig. 6. Graphene and conductive polymers are
nonmagnetic material, NiFe2O4 is magnetic materials, so the composite material of magnetic mainly comes from the NiFe2O4 nanoparticles. From Fig. 6, the significant hysteresis loop of the composites shows no remanence or coercivity, suggesting a superparamagnetic character. The saturation magnetization (Ms) value of RGO-PANI-NiFe2O4, RGO-PPy-NiFe2O4 and RGO-PEDOTNiFe2O4 is 31.1 emu g 1, 31.2 emu g 1 and 31.7 emu g 1, respectively. The value of Ms is smaller than that of NiFe2O4 nanocrystal [21], which is attributed to the existence of nonmagnetic RGO and CPs in the composites. Upon placement of a magnet beside the vial, RGO-CPs-NiFe2O4 nanoparticles were quickly attracted to the side of the vial, leaving the solution transparent (Fig. 6 inset), which suggested the formation of doped magnetic NiFe2O4 nanoparticles. The microwave absorption properties of the composites can be estimated from their dielectric and magnetic properties. The complex permittivity (er = e0 je00 ) and complex permeability (mr = m0 jm00 ) represent electronic and magnetic properties of a material subjected to an electromagnetic field, respectively. The real parts of the permittivity (e0 ) and permeability (m0 ) are
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Fig. 6. Magnetization hysteresis loops of RGO-PANI-NiFe2O4, RGO-PPy-NiFe2O4 and RGO-PEDOT-NiFe2O4 measured at room temperature.
associated with energy storage while the imaginary parts (e00 , m00 ) are related to energy dissipation, resulting from conduction loss, resonance and polarization relaxation, etc. [41,42]. To test and better understand the mechanism of the EM absorption, the complex permittivity real part (e0 ), permittivity imaginary part (e00 ), permeability real part (m0 ) and permeability imaginary part (m00 ) of RGO-PANI-NiFe2O4, RGO-PPy-NiFe2O4 and RGO-PEDOTNiFe2O4 are presented in Fig. 7. From Fig. 7a, we can observe that the e0 values of all samples exhibit decline in the frequency range of
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2–18 GHz, the e0 values of RGO-PANI-NiFe2O4 and RGO-PEDOTNiFe2O4 vary from 10 to 4.7 and 10.2 to 4.9 over 2–18 GHz frequency range, respectively, while e0 values of RGO-PPy-NiFe2O4 decrease from 16.7 to 6.4 with several big fluctuations in the 2– 18 GHz range. In Fig. 7b, it can be seen that e00 values of RGO-PPyNiFe2O4 sharply decrease from 11.4 to 12.2 at 2–13.5 GHz, while e00 values of RGO-PANI-NiFe2O4 and RGO-PEDOT-NiFe2O4 varying from 4.2 to 2.2 and 1.9 to 5.1 with several small fluctuations in the 2–18 GHz. The reasons of the e0 and e00 varying with frequency may be attributed to the following two points. Firstly, with an increase in the frequency of external reverse electric field, the induction charge phase of RGO-CPs-NiFe2O4 composite behind the external electric field and results in electromagnetic oscillation [43], the values of e0 and e00 decrease with an increase frequency. Secondly, the dielectric performance of the composites is influenced by the space charge polarization. The space charge polarization is associated with the heterogeneity and present at the interface among the components of the composites. The difference in dielectric constants among the RGO-CPs-NiFe2O4 composite is responsible for the generation of space charge polarization. The space charge polarization decreases with an increase in the frequency, which results in the values of e0 and e00 decrease with an increase in frequency [44] In Fig. 7c, m0 values of all samples exhibit complex variation in the 2–18 GHz range. From Fig. 7d, we can see that m00 values of RGO-PPy-NiFe2O4 exhibit a major peak at 12– 16 GHz and two minor peaks of RGO-PANI-NiFe2O4 and RGOPEDOT-NiFe2O4 at around 14 and 16 GHz. Generally, the magnetic loss of magnetic materials is originated from hysteresis loss,
Fig. 7. The real part (a) and imaginary part (b) of the complex permittivity, the real part (c) and imaginary part (d) of the complex permeability.
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Fig. 8. The tand of RGO-PANI-NiFe2O4 (a), RGO-PPy-NiFe2O4 (b) and RGO-PEDOT-NiFe2O4 (c).
domain-wall resonance, eddy current effect, and natural resonance [45] In general, the low m00 values indicate dielectric loss may be the main factor determining the EM wave absorbing performances of composites. To further study the EM absorbing mechanism of the composites, the dielectric loss tangent (tande) and magnetic loss tangent (tandm) of RGO-PANI-NiFe2O4 (a), RGO-PPy-NiFe2O4 (b) and RGO-PEDOT-NiFe2O4 (c) were calculated and are shown in Fig. 8. One of the biggest similarities between the measured three samples is tande curve and tandm is symmetric, When tande reach the maximum, on the contrary, the tandm reach the minimum. As far as we know, RGO-CPs is a typical dielectric loss material, whereas NiFe2O4 nanoparticles have magnetic characteristics,
thus, the composites consisting of RGO-CPs and NiFe2O4 nanoparticles could have better impedance matching between the dielectric loss and the magnetic loss, which suggests they have excellent EM wave absorption properties. From Fig. 8a, we can see that tande and tandm values of RGO-PANI-NiFe2O4 most close to 13 GHz within the band of 13–18 GHz, so the maximum absorption corresponding frequency is likely around 13 GHz. Similarly, we can guess the maximum absorption corresponding frequency of RGOPPy-NiFe2O4 and RGO-PEDOT-NiFe2O4 around 15 GHz. In addition, it also can be found from Fig. 8 that tandm are largely lower than those of tande, indicating that the electromagnetic attenuation mechanism of the ternary composites is mainly dependent on dielectric loss.
Fig. 9. Reflection loss curves of RGO-PANI-NiFe2O4 (a) RGO-PPy-NiFe2O4 (b), RGO-PEDOT-NiFe2O4 (c).
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To clarify the EM absorption properties, reflection losses (RL) are calculated by: Z 1 j RL ðdBÞ ¼ 20 logj in Zin þ 1
Z in ¼
qffiffiffiffiffiffiffiffiffiffiffiffi pffiffiffiffiffiffiffiffiffiffi mr =er tan h½jð2pf d=cÞ er mr
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properties. Hence, the RGO-PANI-NiFe2O4 ternary nanocomposites are promising as the applications of potential microwave absorber materials.
ð1Þ Acknowledgements
ð2Þ
Where Zin is the input impedance of the absorber, c is the velocity of electromagnetic waves in free space, f is the frequency and d is the layer thickness. Absorbing material of excellent performance need in frequency range, the value of RL as small as possible. As can be seen from Fig. 9, the thickness of the absorber has a great influence on the microwave absorbing properties. Fig. 9a demonstrates that the maximum reflection loss of RGO-PANI-NiFe2O4 is 49.7 dB at 12.4 GHz with a thickness of 2.4 mm. When the coating layer thickness goes up to 3.5 mm, the bandwidth less than 10 dB (90% of EM wave absorption) can reach up to 5.3 GHz (from 10.9 to 16.2 GHz). Fig. 9b demonstrates that the maximum reflection loss of RGO-PPy-NiFe2O4 is 44.8 dB at 14.9 GHz with a thickness of 1.7 mm. When the coating layer thickness goes up to 1.7 mm, the bandwidth less than 10 dB can reach up to 5.3 GHz (from 12.8 to 18 GHz). Fig. 9c demonstrates that the maximum reflection loss of RGO-PEDOT-NiFe2O4 is 45.4 dB at 15.6 GHz with a thickness of 2 mm. When the coating layer thickness goes up to 2 mm, the bandwidth less than 10 dB can reach up to 3.7 GHz (from 13.5 to 17.3 GHz). These demonstrate that RGO-CPs-NiFe2O4 have a very excellent ability to absorb EM wave, which might result from three reasons as follows: Firstly, dipole polarizations are presented in NiFe2O4 particles, especially when the size is in nanoscale, the small particle size in our case will increase the dipole polarizations, which can be contributed to the dielectric loss, Secondly, the 2Dstructure RGO with large specific surface area can form a complete conductive network, which can improve the dielectric loss. The absence of structure and residual functional groups on the surface of RGO can improve the matching characteristics, moreover, the presence of CPs coating layer enhances the Debye dipole [46] relaxation of RGO, the conjugated electron clouds of CPs molecular chains are transferred to RGO by electronic polarization to form electron tunneling between CPs and RGO, which has the tunnel effect and enhances the absorption of RGO-CPs-NiFe2O4 composites for electromagnetic wave. Thirdly, apart from dielectric loss and magnetic loss, another important concept relating to excellent microwave absorption is strongly dependent on the efficient complementarities between the relative permittivity and permeability. RGO and CPs are dielectric loss absorbents, NiFe2O4 particles have prominent magnetic characteristics, the impedance matching between RGO-CPs and NiFe2O4 particles would play an important role in increasing the electromagnetic absorption properties. 4. Conclusions In summary, conducting polymers (polyaniline, polypyrrole and poly (3,4-ethylenedioxythiophene)) and NiFe2O4 coated on Reduced Graphene Oxide Sheets were successfully fabricated by a two-step method. We found that RGO-CPs-NiFe2O4 ternary composites exhibit excellent microwave absorption properties. The maximum reflection loss of RGO-PANI-NiFe2O4, RGO-PPyNiFe2O4 and RGO-PEDOT-NiFe2O4 are 49.7 dB, 44.8 dB and 45.4 dB, the absorption bandwidths with the reflection losses below 10 dB are 5.3 GHz, 5.3 GHz and 3.7 GHz with a thickness of 2.4 mm, 1.7 mm and 2.0 mm, respectively. The impedance matching between RGO-CPs and NiFe2O4 particles would play an important role in increasing the electromagnetic absorption
This work was financially supported by the Spaceflight Foundation of China (No. 2014-HT-XGD), the Spaceflight Innovation Foundation of China (No. 2014KC11023) and the fundamental Research Funds for the Central Universities (No. 3102016QD021). Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.synthmet.2016. 09.018. References [1] F. Xia, J. Liu, D. Gu, Microwave absorption enhancement and electron microscopy characterization of BaTiO3 nano-torus, Nanoscale 3 (2011) 3860– 3867. [2] Sonai, M. Chandrasekhar, P. Kumar, Microwave sintered sol–gel derived BaTiO3, and Ba0.95La0.05TiO3, ceramic samples for capacitor applications, Ceram. Int. 42 (2016) 10587–10592. [3] X. Lu, Y. Wu, H. Cai, X. Qu, L. Ni, Fe3O4 nanopearl decorated carbon nanotubes stemming from carbon onions with self-cleaning and microwave absorption properties, RSC Adv. 5 (2015) 54175–54181. [4] Z. Ye, Z. Li, J.A. Roberts, P. Zhang, Electromagnetic wave absorption properties of carbon nanotubes-epoxy composites at microwave frequencies, J. Appl. Phys. 108 (2010) 054315–054315-7. [5] M. Fan, Z. He, H. Pang, Microwave absorption enhancement of CIP/PANI composites, Synth. Met. 166 (2013) 1–6. [6] K. Lakshmi, H. John, K.T. Mathew, R. Joseph, K.E. George, Microwave absorption, reflection and EMI shielding of PU–PANI composite, Acta Mater. 57 (2009) 371–375. [7] Z.X. Yu, Z.P. Yao, N. Zhang, Z. Wang, C. Li, Electric field-induced synthesis of dendritic nanostructureda-Fe for electromagnetic absorption application, J. Mater. Chem. A 1 (2013) 4571–4576. [8] X. Zhan, H. Tang, Y. Du, A. Talbi, J. Zha, Facile preparation of Fe nanochains and their electromagnetic properties, RSC Adv. 3 (2013) 15966–15970. [9] B. Gao, L. Qiao, J. Wang, Q. Liu, F. Li, Microwave absorption properties of the Ni nanowires composite, J. Phys. D: Appl. Phys. 41 (2008) 3850–3856. [10] C. Wang, S. Hu, X. Han, W. Huang, L. Tian, Controlled synthesis and microwave absorption property of chain-like co flower, PLoS One 8 (2013) 396–396. [11] S. Stankovich, D.A. Dikin, G.H.B. Dommett, K.M. Kohlhaas, E.J. Zimney, E.A. Stach, Graphene-based composite materials, Nature 442 (2006) 282–286. [12] C. Lee, X. Wei, J.W. Kysar, J. Hone, Measurement of the elastic properties and intrinsic strength of monolayer graphene, Science 321 (2008) 385–388. [13] A.A. Balandin, S. Ghosh, W. Bao, I. Calizo, D. Teweldebrhan, Superior thermal conductivity of single-layer graphene, Nano Lett. 8 (2008) 902–907. [14] Y. Zhao, X. Li, B. Yan, D. Li, S. Lawesb, X. Sun, Significant impact of 2D graphene nanosheets on large volume change tin-based anodes in lithium-ion batteries: a review, J. Power Sources 274 (2014) 869–884. [15] C. Wang, X. Han, P. Xu, X. Zhang, Y. Du, The electromagnetic property of chemically reduced graphene oxide and its application as microwave absorbing material, Appl. Phys. Lett. 98 (2011) 975–980. [16] P. Xu, X. Han, C. Wang, H. Zhao, J. Wang, Synthesis of electromagnetic functionalized barium ferrite nanoparticles embedded in polypyrrole, J. Phys. Chem. B 112 (2008) 2775–2781. [17] L.C. Li, C. Xiang, X.X. Liang, Zn0.6Cu0.4Cr0.5Fe1.46Sm0.04O4 ferrite and its nanocomposites with polyaniline and polypyrrole: preparation and electromagnetic properties, Synth. Met. 160 (2010) 28–34. [18] Z. Su, L. Wang, Y. Li, H. Zhao, B. Chu, Ultraviolet-ozone-treated PEDOT:PSS as anode buffer layer for organic solar cells, Nanoscale Res. Lett. 7 (2012) 1–6. [19] Z.A. King, C.M. Shaw, S.A. Spanninga, D.C. Martin, Structural chemical and electrochemical characterization of poly(3,4-ethylenedioxythiophene) (PEDOT) prepared with various counter-ions and heat treatment, Polymer 52 (2011) 1302–1308. [20] F. Zhao, Z. Wang, J. Zhang, X. Zhu, Y. Zhang, Self-doped and crown-ether functionalized fullerene as cathode buffer layer for highly-efficient inverted polymer solar cells, Adv. Energy Mater. 6 (2016) 1502120. [21] D.G. Li, W.H. Lu, C. Chen, W. Rao, Y.H. Xiong, Synthesis and microwave absorption characteristics of polyaniline, Appl. Mech. Mater. 327 (2013) 53–57. [22] X.W. Ni, X.J. Hu, S.Y. Zhou, C.H. Sun, X.X. Bai, P. Chen, Synthesis and microwave absorbing proper ties of poly(3,4-ethylenediox ythiophene) (PEDOT) microspheres, Polym. Adv. Technol. 22 (2011) 532–537. [23] W. Zhu, L. Wang, R. Zhao, J. Ren, G. Lu, Electromagnetic and microwaveabsorbing properties of magnetic nickel ferrite nanocrystals, Nanoscale 3 (2011) 2862–2864.
Please cite this article in press as: J. Yan, et al., Conducting polymers-NiFe2O4 coated on reduced graphene oxide sheets as electromagnetic (EM) wave absorption materials, Synthetic Met. (2016), http://dx.doi.org/10.1016/j.synthmet.2016.09.018
G Model SYNMET 15455 No. of Pages 8
8
J. Yan et al. / Synthetic Metals xxx (2016) xxx–xxx
[24] X. Gu, W. Zhu, C. Jia, R. Zhao, W. Schmidt, Synthesis and microwave absorbing properties of highly ordered mesoporous crystalline NiFe2O4, Chem. Commun. 47 (2011) 5337–5339. [25] M. Fu, Q. Jiao, Y. Zhao, Preparation of NiFe2O4 nanorod-graphene composites via an ionic liquid assisted one-step hydrothermal approach and their microwave absorbing properties, J. Mater. Chem. A 1 (2013) 5577–5586. [26] T. Wei, Y. Liu, W. Dong, Y. Zhang, C. Huang, Surface-dependent localized surface plasmon resonances in CuS nanodisks, ACS Appl. Mater. Interfaces 5 (2013) 10473–10477. [27] W.S. Hummers, R.E. Offeman, Preparation of graphitic oxide, J. Am. Chem. Soc. 80 (1958) 1339–1339. [28] R. Liang, H. Cao, D. Qian, J. Zhang, M. Qu, Designed synthesis of SnO2polyaniline-reduced graphene oxide nanocomposites as an anode material for lithium-ion batteries, J. Mater. Chem. 21 (2011) 17654–17657. [29] H. Wang, E. Zhu, J. Yang, P. Zhou, D. Sun, Bacterial cellulose nanofibersupported polyaniline nanocomposites with flake-shaped morphology as supercapacitor electrodes, J. Phys. Chem. C 116 (2012) 13013–13019. [30] S.A. Spanninga, D.C. Martin, Z. Chen, X-ray photoelectron spectroscopy study of counterion incorporation in poly(3,4-ethylenedioxythiophene), J. Phys. Chem. C 113 (2009) 5585–5592. [31] S. Lee, K.K. Gleason, Enhanced optical property with tunable band gap of crosslinked PEDOT copolymers via oxidative chemical vapor deposition, Adv. Funct. Mater. 25 (2015) 85–93. [32] Z. Jin, J. Yao, C. Kittrell, J.M. Tour, Large-scale growth and characterizations of nitrogen-doped monolayer graphene sheets, ACS Nano 5 (2011) 4112– 4117. [33] W. Chen, S. Li, C. Chen, L. Yan, Self-assembly and embedding of nanoparticles by in situ reduced graphene for preparation of a 3D graphene/nanoparticle aerogel, Adv. Mater. 23 (2011) 5679–5683. [34] M. Xue, F. Li, J. Zhu, H. Song, M. Zhang, Structure-based enhanced capacitance: in situ growth of highly ordered polyaniline nanorods on reduced graphene oxide patterns, Adv. Funct. Mater. 22 (2012) 1284–1290. [35] P.B. Liu, Y. Huan, X. Zhang, Enhanced electromagnetic absorption properties of reduced graphene oxide–polypyrrole with NiFe2O4 particles prepared with simple hydrothermal method, Mater. Lett. 120 (2014) 143–146.
[36] A. Schaarschmidt, A.A. Farah, A. Aby, A.S. Helmy, Influence of nonadiabatic annealing on the morphology and molecular structure of PEDOT-PSS films, J. Phys. Chem. B 113 (2009) 9352–9355. [37] Q. Yao, L. Chen, W. Zhang, S. Liufu, X. Chen, Enhanced thermoelectric performance of single-walled carbon nanotubes/polyaniline hybrid nanocomposites, ACS Nano 4 (2010) 2445–2451. [38] K.S. Choi, F. Liu, J.S. Choi, T.S. Seo, Fabrication of free-standing multilayered graphene and poly(3,4-ethylenedioxythiophene) composite films with enhanced conductive and mechanical properties, Langmuir 26 (2010) 12902– 12908. [39] J. Zhang, X.S. Zhao, Conducting polymers directly coated on reduced graphene oxide sheets as high-performance supercapacitor electrodes, J. Phys. Chem. C 116 (2012) 5420–5426. [40] P. Sivakumar, R. Ramesh, A. Ramanand, S. Ponnusamy, C. Muthamizhchelvan, Synthesis and characterization of NiFe2O4, nanoparticles and nanorods, J. Alloys Compd. 563 (2013) 6–11. [41] Z. Liu, G. Xu, M. Zhang, K. Xiong, P. Meng, Synthesis of CoFe2O4/RGO nanocomposites by click chemistry and electromagnetic wave absorption properties, J. Mater. Sci. Mater. Electron. (2016) 1–8. [42] P.B. Liu, Y. Huang, J. Yan, Magnetic graphene@PANI@porous TiO2 ternary composites for high-performance electromagnetic wave absorption, J. Mater. Chem. C 4 (2016). [43] V. Panwar, R.M. Mehra, Analysis of electrical, dielectric, and electromagnetic interference shielding behavior of graphite filled high density polyethylene composites, Polym. Eng. Sci. 48 (2008) 2178–2187. [44] K. Singh, A. Ohlan, V.H. Pham, R.B.S. Varshney, Nanostructured graphene/Fe3O4 incorporated polyaniline as a high performance shield against electromagnetic pollution, Nanoscale 5 (2013) 2411–2420. [45] L. Yan, J. Wang, X. Han, Y. Ren, Q. Liu, Enhanced microwave absorption of Fe nanoflakes after coating with SiO2 nanoshell, Nanotechnology 21 (2010) 95708–95712. [46] M.S. Cao, J. Yang, W.L. Song, D.Q. Zhang, B. Wen, Ferroferric oxide/multiwalled carbon nanotube vs polyaniline/ferroferric oxide/multiwalled carbon nanotube multiheterostructures for highly effective microwave absorption, ACS Appl. Mater. Interfaces 4 (2012) 6949–6956.
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