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A Green Approach of Conductive PEDOT:PSS Decorating MagneticGraphene to Recover Conductivity for Highly Efficient Absorption Xin Wang, Jincheng Shu, Xuemei He, Min Zhang, Xixi Wang, Chong Gao, Jie Yuan, and Maosheng Cao ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b02534 • Publication Date (Web): 22 Sep 2018 Downloaded from http://pubs.acs.org on September 23, 2018

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ACS Sustainable Chemistry & Engineering

A Green Approach of Conductive PEDOT:PSS Decorating Magnetic-Graphene to Recover Conductivity for Highly Efficient Absorption Xin Wang,† Jin-Cheng Shu,† Xue-Mei He,† Min Zhang,† Xi-Xi Wang,† Chong Gao,§ Jie Yuan,‡ ‡ Mao-Sheng Cao*†

† School of Material Science and Engineering, Beijing Institute of Technology, No. 5 Zhongguancun South Street, Beijing 100081, China ‡School of Science, Minzu University of China, No. 27 Zhongguancun South Street, Beijing 100081, China §The High School Affiliated to Minzu University of China, No. 5 Fahuasi Road, Beijing 100081, China

*Correspondence to Maosheng Cao

E-mail: [email protected]

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ABSTRACT Graphene hybrid material is the hotspot in the fields of electromagnetic interference (EMI) shielding and microwave absorption (MA). However, hybridization reduces the conductivity of graphene resulting in the dramatical decline of MA performance. Herein, a novel two-dimensional (2D) hybrid material of PEDOT:PSS-Fe3O4-rGO (P-GF) was fabricated by a green approach of decorating conductive PEDOT:PSS using molecular-atomic deposition routes. The electromagnetic properties and MA performance of the hybrid materials are effectively tuned by tailoring the deposition and hybrid ratios of atoms and molecules. The MA is significantly enhanced and the effective absorption bandwidth (BW) is widened by 140%. The maximum reflection loss reaches -61.4 dB with the maximum BW up to ~6.4 GHz (≤10 dB). The enhanced MA performance is attributed to the deposition of conductive PEDOT:PSS which reconstructs conductive network for the aggregation-induced charge transport, as well as arises from the contribution of the introduced interface to multiple relaxation. This finding provides a reference for the future design of microwave absorbing materials, and the as-prepared P-GF has broad application prospects as a highly efficient MA material.

KEYWORDS: Graphene nanohybrids, Conductive PEDOT:PSS, Magnetic nanocrystal, Molecular deposition, Microwave absorption


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INTRODUCTION In the era of electronic information technology, the electromagnetic radiation has harmful effects on the functions of precision electronic equipment and human health. Hence, preventing electromagnetic radiation has become a critical issue all over the world.1-12 An effective approach is to develop efficient MA materials to counteract the increasing electromagnetic radiation.13-16 Among the existing MA materials, graphene is one of the brightest stars.17-26 Chen et al. first reported graphene/epoxy composites and their EMI shielding performance,27 which attracted the attention of researchers.28-31 Singh, VK et al. synthesized graphene oxide (rGO) with a layered and porous structure by thermal exfoliation of graphite oxide, which presented high MA property.28 Cheng's group explored lightweight and flexible 3D graphene foam composites, showing stable EMI shielding performance under repeated bending.29 Cao's group reported that the graphene composites exhibit highly efficient EMI shielding, MA performance and heat-stabilized dielectric constants at elevated temperatures.30,31 They demonstrated that excellent permittivity and EMI shielding of graphitized r-GO/SiO2 composites can be achieved at temperatures ranging from 323 to 473 K. These findings light a new hot spot in the field. In recent years, graphene hybrids have become the focus.32-36 In the year of 2014, ZnO hollow spheres were encapsulated in graphene sheets, effectively improving dielectric constant due to the induced polarization of the graphene/ZnO interface.32 Fe3O4 or Ni magnetic particles were decorated on graphene surfaces by atomic layer deposition, successfully increasing the magnetic loss.33 Graphene/Fe nanocomposites demonstrated that the MA properties could be significantly enhanced.34 Later, multiple hierarchical structures of Graphene@Fe3O4@SiO2@NiO nanosheet were fabricated, further enhancing the electromagnetic attenuation.35 More recently, a



simple strategy of confinedly implanting small NiFe2O4 clusters on reduced graphene oxide was demonstrated and frequency-selected MA was successfully realized.36 Although hybridization can improve the MA properties of material, the introduction of non-conductive phases, however, destroys conductive networks and degrades the conductivity of hybrid material, significantly limiting the further enhancement of MA. To solve this problem, a multiwalled carbon nanotubes/silica (MWNTs/SiO2) nanocomposite have been assembled to achieve excellent dielectric properties in the temperature range of 373-873 K.37 Later, a three-dimensional (3D) nanostructure composed of chemically modified graphene/Fe3O4 (GF) doped polyaniline was constructed.38 And then, a chemically selective approach for inducing Fe3O4@ZnO core-shell nanoparticles to modify carbon nanotubes was developed to form MWCNT/Fe3O4@ZnO heterotrimers.39 However, these materials still have problems, such as the high environment temperature, harsh experimental conditions, complicated preparation process and not eco-friendly. Therefore, we expect to explore a green way for fabricating a multifunctional graphene composite without destroying the conductivity network. In this work, we propose a green approach to decorate magnetic-graphene by depositing conductive PEDOT:PSS. The formation mechanism of P-GF are demonstrated, and the deposition effect of conductive PEDOT:PSS on MA of the nanohybrids are investigated systematically. The nanohybrids exhibit enhanced MA properties. And the electromagnetic properties and MA performance are effectively tuned by tailoring the hybrid ratios of atoms and molecules. More significantly, this finding provides a feasible green method to fabricate 2D hybrid material with strong absorption and wide absorption bandwidths.


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EXPERIMANTAL SECTION Materials Graphite powder (flake graphite, grade 325) was purchased from Haida Corporation (Qingdao, China). Ferric chloride (FeCl3·6H2O, 99.0%), L-Ascorbic (C6H8O6, 99.7%) and hydrazine hydrate (N2H4·H2O, 80%) were purchased from Beijing chemical factory. All the chemical reagents were analytically pure. Graphene oxide (GO) was prepared from graphite powder by a modified Hummers method. Fabrication of Fe3O4-rGO (GF) The GF was prepared by a facile one-pot hydrothermal method. In a typical experiment, 77 mg of graphene oxide (GO) was added to 40 ml of distilled water and stirred for 12 h to form a homogeneous dispersion. Then, 0.270 g of FeCl3•6H2O and 0.528 g of C6H8O6 were added to 40 ml of GO solution, and the mixture was ultrasonicated for 1 h and then stirred for 12 h. After adding 10 ml of N2H4•H2O2, 40 ml of the mixture was transferred to a 50 ml Teflon-lined autoclave and heated at 180℃ for 8 h. Finally, the resulting product was suction-filtered, dried and ground to obtain powdery GF (P:GF=0:1). Fabrication of 2D P-GF hybrid To obtain 2D P-GF hybrid, 300 mg of GF powder was added to 200 ml of distilled water and ultrasonicated for 1 h, and then 4.68 ml of PEDOT:PSS solution was added and ultrasonicated for 3 h. Subsequently, the resulting solution was dried in an oven at 40°C. The as-obtained product is remarked as P:GF=1:4. In a similar way, P:GF=1:2 and P:GF=1:1 were prepared with 300 mg of GF and 9.375 ml, 18.75 ml of PEDOT:PSS, respectively. Samples preparation for electromagnetic parameters Typically, different mass ratios of PEDOT:PSS/GF hybrids are prepared for



comparison experiments (P:GF=0:1, P:GF=1:4, P:GF=1:2, P:GF=1:1). Then, the hybrids (20, 30, 40, 50 and 60wt.%) and paraffin wax (80, 70, 60, 50 and 40wt.%) were dispersed into C4H10O with vigorous stirring to evaporate the solution completely. Finally, the prepared mixtures were pressed into a toroidal shape (φout: 7.03 mm; φin: 3.00 mm) with the same thickness of ~2 mm. Characterization Scanning electron microscope (SEM) images were recorded by a HITACHI S-4800 microscope. Transmission electron microscope (TEM) images were collected by TEM-2100F microscope. Powder X-ray diffraction (XRD) was performed on an X'Pert PRO system with a Cu-Kα radiation source. P-GF was identified using a Fourier transform infrared spectrometer (FT-IR, NICOLE TiS50). The magnetic properties of P-GF were measured using a Lakeshore 7407 Vibration Sample Magnetometer (VSM). Dielectric constant and permeability were recorded using a vector network analyzer (VNA, Anritsu 37269D) in the range of 2-18 GHz. The conductivities of P-GF samples were investigated by four-point probe technique (Model 4200-SCS). RESULTS AND DISCUSSION The formation process of P-GF is schematically illustrated in Figure 1. The P-GF is prepared by a facile and green two-pot method. The preparation of GF adopts one-step reduction method, which is simple, convenient and energy-saving. The entire reaction process does not require very high temperature. In the Figure 1, a, b, and c are cross section views of 1, 2 and 3, respectively. The process of layer-by-layer synthesis of 2D composites is clearly demonstrated. The growth mechanism of P-GF is shown in Figure 2. Figure 2a shows the implantation of magnetic particles to form a binary hybrid. The negative functional groups (-OH, C=O, C-O-C) on GO will attract


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metal ions (Fe2+ and Fe3+) by electrostatic attraction, along with hydrolysis and nucleation.33 These functional groups and defects serve as the confined points for Fe3O4 crystallizing, growing and eventually forming small clusters.40 Further, the water-soluble conductive PEDOT:PSS is selective to 2D-microlayer sheets, which aims at recovering the conductive networks, as shown in Figure 2b. The PEDOT:PSS deposition on binary hybrids can be realized by π-π conjugates, forming the attractive pie-like structure.41 The microstructures of GF are analyzed in SEM images (Figure 3a-c). Figure 3a and 3b indicate that Fe3O4 is uniformly implanted on rGO. Their enlarged image of Figure 3c indicates that Fe3O4 is uniformly implanted in forms of small clusters. This is consistent with the growth mechanism in Figure 2a, that is the uneven distribution of defects and groups results in confined growth of the clusters. Figure 3d-f are SEM images of different resolutions of the P-GF ternary hybrid. The flexible PEDOT:PSS layers are deposited on the hybrid with multiple wrinkles as shown in Figure 3d,e. Furthermore, Figure 3f marks the Fe3O4, rGO, PEDOT: PSS in the typical position. Because the Fe3O4 clusters are covered by PEDOT: PSS, we can only see mountain-like protrusions, which indicate the implanting of magnetic clusters. The element distribution of the P-GF ternary hybrid is shown in Figure S1. The C, O, N, S and Fe elements are uniformly distributed and overlap each other within the red line region, which means that the P-GF hybrid is hierarchical structure consisting of PEDOT:PSS, Fe3O4, and rGO. The TEM images of GF and P-GF composites are shown in Figure 4. Figure 4a and 4b further confirm that Fe3O4 magnetic clusters are uniformly implanted on the rGO



nanosheets. The HRTEM images shown in Figure 4c present the crystal structure of Fe3O4. The interplanar spacing is ~0.253 nm, which corresponds to the (311) crystal plane of Fe3O4. Meanwhile, the selected-area electron diffraction (SAED) pattern shows that the Fe3O4 nanocrystal is cubic spinel structure (Figure 4d). Figure 4e shows the blurred image due to the poor crystalline property of PEDOT:PSS. The PEDOT:PSS wrinkles and the fringes of the magnetic nanocrystal clusters can be clearly seen in the HRTEM images (Figure 4f-g). The SAED pattern is consistent with Figure 4d (Figure 4h). The XRD is used to characterize the crystal structure of the samples. The corresponding results are shown in Figure S2. For GF, the seven peaks at 30.3°, 35.6°, 43.3°, 53.8°, 57.3°, and 62.9° correspond to (220), (311), (400), (422), (511) and (440) crystal faces of Fe3O4, respectively, which further confirm the cubic spinel structure of Fe3O4.42 The same series of characteristic peaks are also observed for P-GF, indicating the stability of the crystalline phase of the Fe3O4 nanoparticles after PEDOT:PSS deposition. In the FT-IR spectrum, the stretching vibration peaks of C-N and C=N at ~1194 cm-1 and ~1605 cm-1 respectively, confirm the successful doping of N (Figure 5). The successful formation of the PEDOT:PSS in hybrid materials include the presence of the peaks at 1517 and 1340 cm-1 (C=C and C-C stretching vibrations of the thiophene ring), 1200 and 1088 cm-1 (C-O-C bond stretching), and 982, 839, and 689 cm-1 (C-S bond in the thiophene ring).43,44 The saturation magnetization increases with the addition of Fe3O4, indicating the enhancement of the magnetic properties, as shown in


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Figure S3. Figure 6a-d show the complex permittivity of P-GF with different hybrid ratios when the filler loading is 50%. The real permittivity (ε') shows a decreasing trend with increasing frequency. As the decrease of the conductive PEDOT:PSS content, the ε' changes from 17.21 to 7.24. The imaginary permittivity (ε'') has two relaxation peaks at ~9 GHz and ~15 GHz. The Cole-Cole plots prove that the material has multiple relaxations (Figure 6e-f). They may arise from dipole polarization and interfacial polarization. Figure 7a-d are the real permeability (µ') and the imaginary permeability (µ") of the samples. Multiple magnetic resonance peaks can be observed. In fact, resonance loss may result from domain-wall resonance loss, hysteresis attenuation, exchange resonance loss and magnetic natural resonance loss. Due to the weak magnetic field and GHz frequency range, the magnetic hysteresis attenuation and domain-wall resonance loss can be excluded.8,45 Peaks at low frequencies are attributed to nature resonance, as shown in Figure 7e. Considering the small size effect,46-48 the resonance peak at high frequency, as shown in Figure 7f is derived from the exchange resonance. Figure 8a is the reﬂection loss (RL) plot of P:GF=1:1 samples at different thicknesses with a filler loading of 50%. It shows that, with the decrease of the thickness, the absorption peak moves toward high frequency, shifts from the C band to the Ku band. When the thickness is 1.81 mm, the maximum BW is ~6.4 GHz. It has a maximum absorption peak of -61.4 dB at 3.86 mm. Figure 8b is a graph of the RL at different hybrid ratios. Tailoring the deposition ratios can significantly tune the



MA performance. It can be seen from Figure 8b that increasing the proportion of PEDOT:PSS can significantly improve the RL by 3 times, up to -42.7 dB with a thickness of 1.81 mm. Figure 8c is the MA performance graph of P:GF=1:1 samples at different filler loadings. Changing the filler loading can significantly tune the RL. With the increasing of filler loading, the RL increases first and then decreases. When the filler loading increases to 50%, the RL has a maximum value. In addition, the peak moves to low frequency as the filler loading increases. Figure 8d is the maximum RL and BW estimation for different hybrid ratios when the thickness is changed from 1.81 to 3.96 mm and the filler loading is 50%. By comparison, it can be seen that when the hybrid ratio is 1:1, the material has the largest RL (-61.4 dB) and the widest BW (~6.4 GHz). The above results indicate that a multi-strategy control of MA performance is successfully achieved. Figure 9a-d are the 3D RL plots of P-GF samples versus frequency and thickness with different hybrid ratios when the filler loading is 50%. The maximum RL of each component is -40.6 dB (P:GF=0:1), -56.8 dB (P:GF=1:4), -59.4 dB (P:GF=1:2), and -61.4 dB (P:GF=1:1), respectively. Increasing the proportion of PEDOT:PSS can effectively improve the maximum RL from -40.6 dB to -61.4 dB. This phenomenon indicates that tailoring the hybridization ratio can effectively tune the MA performance. At the same time, it can be seen from the Figure 9d that the absorbing band (RL≤−10 dB, corresponding to 99% attenuation) reaches 16 GHz (~ 4-18 GHz, ~ 16-18 GHz) almost covering the entire investigated frequency range for composites with thickness range of 1.06-4.06 mm. And with the increase of PEDOT:PSS


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concentration, double absorption bands gradually appear and move to the low frequencies, indicating that the tailoring deposition of PEDOT:PSS can successfully tune the MA properties. For an ideal microwave absorber, both highly efficient attenuation and well impedance matching are required. Figure 9e shows the change of the absolute value of the Zin at different hybrid ratios. As the PEDOT:PSS concentration increases, |Zin| gradually closes to 1, which leads to the greatest MA performance. The result demonstrates that the tailoring deposition of PEDOT:PSS can significantly tune the impedance matching, and thus affects the MA performances. Figure 10a-e are 3D RL plots of P:GF=1:1 samples versus frequency and thickness with different filler loadings. Compared with other components, the sample with filler loading of 50% has the highest MA peak, and two peaks appear at a thickness of 1.81 mm, so that the absorption region is significantly expanded. This shows that there is a best ratio of the filler loading. To evaluate the MA capacity of the P:GF=1:1 samples, Figure 10f shows a 3D bar graph of their maximum RL at different filler loading and thicknesses. It is observed that the maximum RL of 50 % loading sample is much better than others, especially at 3.86 mm. The conductivity loss of the P-GF composites plays the main role on the dielectric loss. The conductivities of P-GF with different hybrid ratios were recorded by four-point probe technique, and the results are showed in Table S1. It is found that the GF had poor electrical conductivity, and with the increase content of PEDOT:PSS, the conductivity values of P-GF composites increased correspondingly. Table S2 shows the MA properties of some of the previous reported magnetic graphene nanocomposites. It can be clearly seen that P-GF



nanocomposites have a broader absorption BW and stronger MA capability at the same time. All the above results indicate that tailoring the molecular and atomic deposition affects the dielectric loss and magnetic loss, as shown in Figure 11. As it is well known, MA property of electromagnetic wave absorbers are strongly determined by their complex relative permittivity (εr=ε'-jε'') and complex relative permeability (µr=µ′-jµ′′). According to Debye theory, the ε' and the µ′ are corresponding to the electrical and magnetic energy (EM energy) stored within the material. The ε'' represents the loss of energy, including the conductance loss and relaxation loss. And the µ′′ represents the magnetic loss, which comes from the eddy current loss, exchange resonance and nature resonance. When magnetic clusters deposited, the strengthened energy barrier for electron hopping will hamper formation of micro-current networks, resulting in poor dielectric loss. The deposition of PEDOT:PSS can connect dispersed graphite sheets to form a stable local conductive network, which acts as a bridge for the aggregation-induced charge transport (Figure 11a, b). According to Cao's electron-hopping model and conductive network equation,49,50 when electromagnetic wave propagates in the composite, the free electrons will move or hop between the graphite sheet and PEDOT:PSS in the material, which provides excellent dielectric loss. And the multiple relaxations may arise from interfacial polarization and dipole polarization. The interfacial polarization is derived from the interface between different phases, such as Fe3O4 and rGO, Fe3O4 and PEDOT:PSS, PEDOT:PSS and rGO. In addition, the abundant defects possessed


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by graphene and the residual functional groups provide a large amount of polarization, which causes multiple relaxation losses of electromagnetic wave. The multiple polarization theory put forward by Cao's group can well support this view.51,52 At the same time, the capacitor-like structures at the interfaces may attenuate the power of incident EM waves. Moreover, magnetic nanocrystal clusters can cause nature resonance (shown in the imaginary permeability), exchange resonance, and micro eddy currents. In addition, multiple scattering also has a huge contribution to MA, which is shown in the Figure 11c, d. Therefore, tailoring the conductive PEDOT:PSS and Fe3O4 clusters can effectively tune the composites dielectric loss and magnetic loss to obtain excellent MA properties. CONCLUSIONS In summary, a novel 2D hybrid material of P-GF is fabricated by a green approach of decorating conductive PEDOT:PSS using molecular-atomic deposition routes. The electromagnetic and MA properties of 2D hybrid materials can be effectively improved by multi-strategy tuning, especially the adjustment of the hybrid ratios of materials.

The

deposition

of

conductive

PEDOT:PSS

decorating

the

magnetic-graphene, can form a complete conductive network which acts as a bridge for the aggregation-induced charge transport. This provides excellent dielectric loss. The implanted ferroferric oxide magnetic clusters can provide magnetic loss, forming magnet-electric integrated structure. All of these have a great effect on electromagnetic wave attenuation. The maximum RL reaches -61.4 dB, and the effective absorption BW can cover ~6.4 GHz at (-10 dB). Our finding provides a feasible green approach for the recovery of conductivity of magnetic hybrid materials to govern electromagnetic pollution.



SUPPORTING INFORMATION The elemental mapping images; XRD pattern; Magnetic hysteresis loops; Frequency dependence of µ"(µ')-2f-1; The conductivity of P-GF; MA Performance of Representative rGO-Fe3O4-Based Composites. ACKNOWLEDGEMENTS This work was supported by National Natural Science Foundation of China (No. 11774027, 51132002 and 51372282).


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Figure Captions Figure 1. Schematic of the green process of tailoring P-GF nanohybrids by molecular-atomic deposition. Wherein, a, b, and c correspond to the cross section views of 1, 2, and 3, respectively. Figure 2. The illustration of atomic and molecular deposition mechanisms. (a) Atomic deposition mechanisms. (b) Molecular deposition mechanisms. Figure 3. SEM images of: (a-c) GF nanohybrid with different magnifications, (d-f) P-GF nanohybrid with different magnifications. The black line represents the area where the Fe3O4 particles are concentrated, the blue line represents the PEDOT:PSS fold, and the red line represents the graphene sheet. Figure 4. (A) TEM images of GF, (a-b) TEM images, (c) HRTEM image, (d) SAED pattern. (B) TEM images of P-GF, (e-f) TEM images, (g) HRTEM image, (h) SAED pattern. Figure 5. Transmission infrared spectra of GF and P-GF samples. Figure 6. (a-d) The complex permittivity of P-GF with different hybrid ratios (the filler loading: 50%): (a) P:GF=0:1, (b) P:GF=1:4, (c) P:GF=1:2, (d) P:GF=1:1. (e-f) Cole-Cole plots of P:GF=1:1. Figure 7. (a-d) The complex permeability of P-GF with different hybrid ratios (the filler loading: 50%): (a) P:GF=0:1, (b) P:GF=1:4, (c) P:GF=1:2, (d) P:GF=1:1. (e-f) Partial magnification of Figure 7a. Figure 8. (a) The RL of P:GF=1:1 samples at different thicknesses with a filler loading of 50%, (b) The RL at different hybrid ratios when the filler loading is 50% and the thicknesses is 1.81 mm, (c) The RL of P:GF=1:1 samples at different filler loadings with a thicknesses of 1.81 mm, (d) The maximum RL and bandwidth evaluation for different hybrid ratios (the filler loading: 50%). Figure 9. (a-d) 3D RL plots of P-GF samples versus frequency and thickness with different hybrid ratios (the filler loading: 50%) (a) P:GF=0:1, (b) P:GF=1:4, (c) P:GF=1:2, (d) P:GF=1:1. (e) The modulus of |Z⁠ in| versus hybrid ratio (the filler loading: 50%). Figure 10. (a-e) 3D RL plots of P:GF=1:1 samples versus frequency and thickness with different filler loadings. (a) 20%, (b) 30%, (c) 40%, (d) 50%, (e) 60%. (f) 3D plot of maximum RL evaluation at different filler loadings and thicknesses. Figure 11. Schematic illustrations for (a)weak network, (b) reconfiguration network, (c) conductive-network, (d) multi-relaxation in P-GF.


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Figure 1. Schematic of the green process of tailoring P-GF nanohybrids by molecular-atomic deposition. Wherein, a, b, and c correspond to the cross section views of 1, 2, and 3, respectively.



Figure 2. The illustration of atomic and molecular deposition mechanisms. (a) Atomic deposition mechanisms. (b) Molecular deposition mechanisms.


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Figure 3. SEM images of: (a-c) GF nanohybrid with different magnifications, (d-f) P-GF nanohybrid with different magnifications. The black line represents the area where the Fe3O4 particles are concentrated, the blue line represents the PEDOT:PSS fold, and the red line represents the graphene sheet.



Figure 4. (A) TEM images of GF, (a-b) TEM images, (c) HRTEM image, (d) SAED pattern. (B) TEM images of P-GF, (e-f) TEM images, (g) HRTEM image, (h) SAED pattern.


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Figure 5. Transmission infrared spectra of GF and P-GF samples.



Figure 6. (a-d) The complex permittivity of P-GF with different hybrid ratios (the filler loading: 50%): (a) P:GF=0:1, (b) P:GF=1:4, (c) P:GF=1:2, (d) P:GF=1:1. (e-f) Cole-Cole plots of P:GF=1:1.


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Figure 7. (a-d) The complex permeability of P-GF with different hybrid ratios (the filler loading: 50%): (a) P:GF=0:1, (b) P:GF=1:4, (c) P:GF=1:2, (d) P:GF=1:1. (e-f) Partial magnification of Figure 7a.



Figure 8. (a) The RL of P:GF=1:1 samples at different thicknesses with a filler loading of 50%, (b) The RL at different hybrid ratios when the filler loading is 50% and the thicknesses is 1.81 mm, (c) The RL of P:GF=1:1 samples at different filler loadings with a thicknesses of 1.81 mm, (d) The maximum RL and bandwidth evaluation for different hybrid ratios (the filler loading: 50%).


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Figure 9. (a-d) 3D RL plots of P-GF samples versus frequency and thickness with different hybrid ratios (the filler loading: 50%) (a) P:GF=0:1, (b) P:GF=1:4, (c) P:GF=1:2, (d) P:GF=1:1. (e) The modulus of |Z⁠ in| versus hybrid ratio (the filler loading: 50%).



Figure 10. (a-e) 3D RL plots of P:GF=1:1 samples versus frequency and thickness with different filler loadings. (a) 20%, (b) 30%, (c) 40%, (d) 50%, (e) 60%. (f) 3D plot of maximum RL evaluation at different filler loadings and thicknesses.


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Figure 11. Schematic illustrations for (a)weak network, (b) reconfiguration network, (c) conductive-network, (d) multi-relaxation in P-GF.



TOC A novel 2D hybrid material of PEDOT:PSS-Fe3O4-rGO was fabricated by a green sustainable approach, applied as an excellent microwave absorber.


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A novel 2D hybrid material of PEDOT:PSS-Fe3O4-rGO was fabricated by a green sustainable approach, applied as an excellent microwave absorber. 381x338mm (300 x 300 DPI)



Figure 1. Schematic of the green process of tailoring P-GF nanohybrids by molecular-atomic deposition. Wherein, a, b, and c correspond to the cross section views of 1, 2, and 3, respectively. 127x127mm (300 x 300 DPI)


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Figure 2. The illustration of atomic and molecular deposition mechanisms. (a) Atomic deposition mechanisms. (b) Molecular deposition mechanisms. 169x84mm (300 x 300 DPI)



Figure 3. SEM images of: (a-c) GF nanohybrid with different magnifications, (d-f) P-GF nanohybrid with different magnifications. The black line represents the area where the Fe3O4 particles are concentrated, the blue line represents the PEDOT:PSS fold, and the red line represents the graphene sheet. 127x127mm (300 x 300 DPI)


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Figure 4. (A) TEM images of GF, (a-b) TEM images, (c) HRTEM image, (d) SAED pattern. (B) TEM images of P-GF, (e-f) TEM images, (g) HRTEM image, (h) SAED pattern. 211x127mm (300 x 300 DPI)



Figure 5. Transmission infrared spectra of GF and P-GF samples. 205x85mm (120 x 120 DPI)


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Figure 6. (a-d) The complex permittivity of P-GF with different hybrid ratios (the filler loading: 50%): (a) P:GF=0:1, (b) P:GF=1:4, (c) P:GF=1:2, (d) P:GF=1:1. (e-f) Cole-Cole plots of P:GF=1:1. 169x211mm (300 x 300 DPI)



Figure 7. (a-d) The complex permeability of P-GF with different hybrid ratios (the filler loading: 50%): (a) P:GF=0:1, (b) P:GF=1:4, (c) P:GF=1:2, (d) P:GF=1:1. (e-f) Partial magnification of Figure 7a. 169x211mm (300 x 300 DPI)


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Figure 8. (a) The RL of P:GF=1:1 samples at different thicknesses with a filler loading of 50%, (b) The RL at different hybrid ratios when the filler loading is 50% and the thicknesses is 1.81 mm, (c) The RL of P:GF=1:1 samples at different filler loadings with a thicknesses of 1.81 mm, (d) The maximum RL and bandwidth evaluation for different hybrid ratios (the filler loading: 50%). 480x219mm (300 x 300 DPI)



Figure 9. (a-d) 3D RL plots of P-GF samples versus frequency and thickness with different hybrid ratios (the filler loading: 50%) (a) P:GF=0:1, (b) P:GF=1:4, (c) P:GF=1:2, (d) P:GF=1:1. (e) The modulus of |Z⁠ in| versus hybrid ratio (the filler loading: 50%). 127x169mm (300 x 300 DPI)


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Figure 10. (a-e) 3D RL plots of P:GF=1:1 samples versus frequency and thickness with different filler loadings. (a) 20%, (b) 30%, (c) 40%, (d) 50%, (e) 60%. (f) 3D plot of maximum RL evaluation at different filler loadings and thicknesses. 338x381mm (300 x 300 DPI)



Figure 11. Schematic illustrations for (a)weak network, (b) reconfiguration network, (c) conductive-network, (d) multi-relaxation in P-GF. 254x254mm (300 x 300 DPI)


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Green Approach to Conductive PEDOT:PSS ... - ACS Publications

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