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An approach for the preparation of silver nanoparticle-reduced graphene oxide/polyurethane composites (AgNP@RGO/PU) was proposed. An electrospinning process was utilized to fabricate a lightweight and flexible PU fiber mat. Graphene oxide (GO)/PU composites were prepared using a dip-coating method. Thus there happens a hydrogen bonding interactions between the GO sheets and PU fibers. A powerful reducing agent, hydriodic acid, was used to reduce GO/PU composites which transforms into RGO/PU composites. The composite exhibited low electrical resistance (3.5 × 10 2 Ω/sq) because of reduction reaction. Furthermore, AgNPs, which were modified with thiophenol, were deposited on the RGO/PU composite through π–π interactions between the aromatic functional groups on the AgNPs and the RGO by a dip-coating method. The obtained AgNP@RGO/PU composite exhibited a remarkably enhanced electrical property (

Nitrogen-doped reduced graphene oxide (N-rGO) has been synthesized using a simple, efficient method combining instant thermal exfoliation and covalent bond transformation from a melamine-graphene oxide mixture. The capacitive performance of N-rGO has been tested in both aqueous (0.5 M H 2 SO 4 ) and organic (1 M tetraethyl-ammonium tetrafluoroborate (TEABF 4 ) in propylene carbonate (PC)) electrolytes, which are compared with those obtained from thermal-reduced graphene oxide (T-rGO) and chemical-reduced graphene oxide (C-rGO). The contributions of scan-rate-independent (double-layer-like) and scan-rate-dependent (pseudo-capacitance-like) capacitance of all reduced graphene oxides in both aqueous and organic electrolytes were evaluated and compared. The results show that relatively rich oxygen-containing functional groups on C-rGO form significant ion-diffusion barrier, resulting in worse electrochemical responses in organic electrolyte. By contrast, the N-doped structures, large surface area, and lower density of oxygen-containing groups make N-rGO become a promising electrode material for organic electric double-layer capacitors (EDLCs). The capacitance rate-retention of N-rGO reaches 71.1% in 1 M TEABF 4 /PC electrolyte when the scan rate is elevated to 200 mVs −1 , demonstrating that N-rGO improves the relatively low-power drawback of EDLCs in organic electrolytes. The specific energy and power of a symmetric N-rGO cell in the organic electrolyte reach 25 Wh kg −1 and 10 kW kg −1 , respectively.

Silver nanowire/reduced graphene oxide nanocomposites (AgNW/rGO) are synthesized using a two-step process: preparation of silver nanowire/graphene oxide (AgNW/GO) and the microwave-assisted hydrothermal (MAH) method. The nanocomposites are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) analyses. Ascorbic acid (AA), dopamine (DA), and uric acid (UA) are determined simultaneously on the AgNW/rGO-modified screen-printed carbon electrodes (SPCEs) by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The results reveal that AgNW/rGO-modified SPCEs exhibit well-resolved oxidation peaks with a negative shift in peak potential and enhanced peak currents in the simultaneous determination of AA, DA and UA in comparison with the pure rGO-modified SPCEs, demonstrating the superior catalytic activity of AgNW/rGO composites. AgNW/rGO-modified SPCEs show the linear response of AA, DA and UA in the concentration range of 45–1550, 40–450 and 35–300 μM with a detection limit of 0.81, 0.26 and 0.30 μM (S/N = 3), respectively. The covalent bonds between AgNWs and rGOs are expected to suppress the random attachment of AgNWs and facilitate the electron transfer and reactant transport by constructing a porous and continuous electrically conductive network. The excellent sensitivity of AgNW/rGO composites makes them become promising electrode materials in the field of electrochemical biosensors.

An effective method is proposed to prepare octa(aminophenyl) silsesquioxane (OAPS) functionalized graphene oxide (GO) reinforced polyimide (PI) composites with a low dielectric constant and ultrastrong mechanical properties. The amine-functionalized surface of OAPS-GO is a versatile starting platform for in situ polymerization, which promotes the uniform dispersion of OAPS-GO in the PI matrix. Compared with GO/PI composites, the strong interfacial interaction between OAPS-GO and the PI matrix through covalent bonds facilitates a load transfer from the PI matrix to the OAPS-GO. The OAPS-GO/PI composite film with 3.0 wt % OAPS-GO exhibited an 11.2-fold increase in tensile strength, and a 10.4-fold enhancement in tensile modulus compared with neat PI. The dielectric constant (D(k)) decreased with the increasing content of 2D porous OAPS-GO, and a D(k) value of 1.9 was achieved.

A powerful synthesis strategy is proposed for fabricating porous polyaniline-reduced graphene oxide (PANI-RGO) composites with transparency up to 80% and thickness from 300 to 1000 nm for the counter electrode (CE) of bifacial dye-sensitizing solar cells (DSSCs). The first step is to combine the in-situ positive charge transformation of graphene oxide (GO) through aniline (ANI) prepolymerization and the electrostatic adsorption of ANI oligomer-GO to effectively control the thickness of ultrathin PANI-GO films by adjusting pH of the polymerization media. In the second step, PANI-GO films are reduced with hydroiodic acid to simultaneously enhance the apparent redox activity for the I3−/I− couple and their electronic conductivity. Incorporating the RGO increases the transparency of PANI and facilitates the light-harvesting from the rear side. A DSSC assembled with such a transparent PANI-RGO CE exhibits an excellent efficiency of 7.84%, comparable to 8.19% for a semi-transparent Pt-based DSSC. The high light-harvesting ability of PANI-RGO enhances the efficiency retention between rear- and front-illumination modes to 76.7%, compared with 69.1% for a PANI-based DSSC. The higher retention reduces the power-to-weight ratio and the total cost of bifacial DSSCs, which is also promising in other applications, such as windows, power generators, and panel screens.

Nanofiber fabric is firstly introduced to replace common microfiber fabrics as the platform for flexible supercapacitors. Nanofiber and microfiber electrodes can be simply fabricated using a dipping process that impregnates reduced graphene oxide (RGO) nanosheets into electrospun polyamide-66 (PA66) nanofiber and microfiber fabrics. RGO nanosheets are tailored to various sizes and only RGO with a medium diameter of 250–450 nm (denoted as M-RGO) can effectively penetrate the pores of nanofiber fabrics for constructing smooth conductive paths within PA66 nanofiber fabrics. The synergistic effect between suitable sizes of RGO nanosheets and nanofiber fabrics with a high specific area provides a symmetric supercapacitor composed of M-RGO/PA66 nanofiber fabric electrodes with high-volume and high-area specific capacitance ( C S,V and C S,A , equal to 38.79 F cm −3 and 0.931 F cm −2 at 0.5 A g −1 , respectively), which are much larger than that of a symmetric supercapacitor composed of RGO/PA66 microfiber fabric electrodes (8.52 F cm −3 and 0.213 F cm −2 at 0.5 A g −1 ). The effect of impregnating nanofiber fabrics with suitably sized RGO to promote C S,V and C S,A of flexible supercapacitors has been demonstrated.

In this study, spongy iron powders (SIPs) that possess a high specific area (1.57 m2/g) were successfully prepared and used for microwave absorption. The specific area was approximately two times higher than that of commercial carbonyl iron powders (CIPs) (0.73 m2/g). The SIPs were incorporated into epoxy resin, to prepare microwave-absorbing composites. The compositions and reflection loss (R.L.) of the composites made of the CIPs and SIPs were compared at the S, C, X and Ku bands. The results showed that the SIP/epoxy composites are lighter and thinner than those of the CIP/epoxy composites. The relative weight per unit area at the four bands was 8.0, 5.0, 2.7, and 2.0 kg/m2 for the SIP/epoxy composites and 15.3, 7.9, 5.0, and 3.3 kg/m2 for the CIP/epoxy composites. The thickness of the SIP/epoxy composites and CIP/epoxy composites at the four bands was 4.4, 2.5, 1.5, and 1.1 mm and 6.2, 3.0, 2.0, and 1.2 mm, respectively. Compared with the microwave absorption performance, the maximum R.L. of the composites bound with SIPs (14.5, 23.8, 15.9, and 16.4 dB) was larger than those of the composites bound with CIPs (14.2, 11.9, 15.6, and 15.1 dB). The microwave-absorbing composites made of SIPs were lighter, thinner, and exhibited higher microwave absorption performance than did those made of the CIPs in the investigated frequency range.

This paper proposes an effective and simple approach to fabricate high-performance graphene oxide (GO)/soluble polyimide (SPI) composite films through a novel and effective process. In this method, GO is dispersed in a dissolved SPI (R-SPI) polymeric matrix with curing state, preventing the reduction of crosslinking reactions of the polymeric matrix, and resulting in substantial improvements in the mechanical and dielectric properties of the composite. The GO/R-SPI composite film contains only 1.0 wt% GO; it possesses high tensile strength (up to 288.6 MPa) and Young's modulus (7.58 GPa), which represent an increase of 260% in tensile strength and 402% in Young's modulus, compared with the neat SPI film (80.3 MPa and 1.51 GPa, respectively). The dielectric constant (Dk) decreases with an increase in the GO content; the Dk of the GO/R-SPI composite film can be as low as 2.1 (compared with 2.8 for the neat SPI film). This novel fabricating method provides a path for developing high-performance GO/R-SPI composite materials as next-generation low-k dielectric materials.

We prepared flexible, lightweight, and high electromagnetic interference (EMI) shielding performance graphene nanosheet (GNS)/water-borne polyurethane (WPU) composites. WPU, with sulfonate functional groups, was used as the polymer matrix. By adsorbing the cationic surfactant (stearyl trimethyl ammonium chloride) on the surface of the GNSs (S-GNSs), restacking and aggregation of the GNSs have been efficiently suppressed, which also attracted sulfonate groups from the WPU matrix. Because of the favorable interfacial interactions arising from electrostatic attraction, the S-GNS exhibited good compatibility with the WPU matrix. Such a homogeneous dispersion contributed to the construction of an electrical conductive network. The S-GNS/WPU composite exhibited a low electrical conductivity percolation threshold and an outstanding enhanced electrical conductivity of approximately 5.1 S/m. A high EMI shielding effectiveness of approximately 32 dB was obtained by the WPU composites with contents of 5 vol.% (approximately 7.7 wt.%) S-GNSs.

A simple, low-cost method for fabricating nitrogen-doped graphene (NG) is demonstrated by combining the ultrafast thermal exfoliation and covalent transformation from the melamine (MA)–graphene oxide (GO) mixture. NGs prepared at 300, 600, and 900 °C were systematically characterized by X-ray photoelectron spectroscopy (XPS), in which pyridinic-N, pyrrolic-N and graphitic-N are the main nitrogen-doped structures in various ratios. These NGs possess large specific surface area and porous microstructures, confirmed by the N2 adsorption–desorption isotherms. The NG-modified screen-printed carbon electrodes (SPCEs) were fabricated to detect ascorbic acid (AA), dopamine (DA) and uric acid (UA) simultaneously by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). Due to the large specific surface area, mesoporous structures and nitrogen-doped sites, these NGs show highly electrochemical sensitivity for AA, DA and UA. Notably, the pyrrolic-N structure makes the negative shift in the oxidation peak potential of these biomolecules, showing the better catalytic activity than pyridinic-N and graphitic-N structures. The large surface area of NGs provides more nitrogen-doped sites to oxidize bio-compounds and enhances the corresponding currents. The good sensitivity of NG-modified SPCEs makes them become effective sensors for determining AA, DA and UA simultaneously. The discrimination to peak potential and current among these NGs can be observed.

High thermal conductivity films were prepared by blending silver nanowires (AgNws) with epoxy resins. 3-Aminopropyltriethoxysilane (APTES) silane was used to modify the AgNws surface, to produce a high aspect ratio and high thermal conductivity. A thermal interface material with a high thermal conductivity coefficient was used to form a thermal channel in epoxy resins, which possess superior thermal conductivity when the composite contained AgNws higher than 50 phr. The phr ratio of AgNws to silver nanoparticles (AgNps) loading was 50:300 when the thermal conductivity coefficient of the composite reached approximately 8 W/mK. The composite density ratio of AgNws (50 phr) to AgNps (300 phr) was 1.512:3.650 (g/cm 3 ), which suggests that the density can be reduced by more than 50% in weight when AgNws, rather than AgNps, were used to prepare thermal interface composites. Furthermore, the adhesion test indicates that the composite containing a lower loading of AgNws exhibits higher adhesive property than that of the composite containing a higher loading of AgNps with a similar thermal conductivity coefficient, thereby resulting in enhanced adhesiveness between devices.

Silver nanowires (AgNWs), modified by cysteamine, with a high electrical conductivity can be combined with high surface area graphene nanosheets (GNs) to form AgNW–GN hybrid nanomaterials. These materials with – NH 3 + functional groups in an alkaline environment can be deposited on waterborne polyurethane surfaces with the attraction of sulfonate functional groups to prepare transparent conductive films with high transmittance and low surface electrical resistance. This self-assembly method provides highly controllable transmittance and surface electrical resistance. The AgNWs can inhibit GNs from restacking and aggregation after reduction from graphene oxide, increasing the electrical conductivity between the GN interlayers. The AgNW–GN hybrid nanomaterial films show a sheet resistance of 86 Ω/sq with 80% light transmittance, and the value of DC conductivity to optical conductivity ratio reaches 19.81.

A 3D graphene sheet–carbon nanotube (GS–CNT) structure with a good wetting property, high porosity, and large surface area is homogeneously deposited with active amorphous manganese oxide ( a -MnO x ) by potentiodynamic deposition. The flowery a -MnO x nanostructure with ultra-slender petals (ca. 5–8 nm) on the framework of hierarchically porous GS–CNT matrix not only enables nearly full utilization of a -MnO x but also retains sufficient conductivity and porosity for the high-rate charge–discharge application. The use of a -MnO x on the 3D GS–CNT material produces a specific capacitance of MnO x of 1200 F g −1 which is much-higher than that of a pure a -MnO x electrode ( C S,Mn = 233 F g −1 ). The specific energy and specific power of a -MnO x /GS–CNT are respectively as high as 46.2 Wh kg −1 and 33.2 kW kg −1 , revealing that our work conceptually provides a way to produce porous structures composed of graphene, carbon nanotubes, and various electroactive materials for high-performance energy storage devices.

This study fabricates amine (NH(2))-functionalized graphene oxide (GO)/polyimide(PI) composite films with high performance using in situ polymerization. Linear poly(oxyalkylene)amines with two different molecular weights 400 and 2000 (D400 and D2000) have been grafted onto the GO surfaces, forming two types of NH(2)-functionalized GO (D400-GO/D2000-GO). NH(2)-functionalized GO, especially D400-GO, demonstrated better reinforcing efficiency in mechanical and thermal properties. The observed property enhancement are due to large aspect ratio of GO sheets, the uniform dispersion of the GO within the PI matrix, and strong interfacial adhesion due to the chemical bonding between GO and the polymeric matrix. The Young's modulus of the composite films with 0.3 wt % D400-GO loading is 7.4 times greater than that of neat PI, and tensile strength is 240% higher than that of neat PI. Compared to neat PI, 0.3 wt % D400-GO/PI film exhibits approximately 23.96 °C increase in glass transition temperature (T(g)). The coefficient of thermal expansion below T(g) is significantly decreased from 102.6 μm/°C (neat PI) to 53.81 μm/°C (decreasing 48%) for the D400-GO/PI composites with low D400-GO content (0.1 wt %). This work not only provides a method to develop the GO-based polyimide composites with superior performances but also conceptually provides a chance to modulate the interfacial interaction between GO and the polymer through designing the chain length of grafting molecules on NH(2)-functionalized GO.

This study demonstrates that platinum–ruthenium (PtRu) nanoclusters decorated on a composite consisting of graphene sheets (GS) and carbon nanotubes (CNTs), denoted as PtRu/GS-CNT, show highly electrocatalytic activity for methanol oxidation with excellent carbon monoxide (CO) tolerance. Herein, restacking of individual GS is effectively inhibited by introducing one-dimensional CNTs to form a 3-D porous microstructure. From the SEM image, CNTs act as useful nanospacers for diminishing the face-to-face aggregation of GS. This 3-D porous structure exposes extensive surface area for evenly depositing PtRu nanoclusters and facilitates the electrolyte/reactant diffusion, leading to the highly catalytic performances of resultant materials. The voltammetric forward peak current density to the reverse peak current density for PtRu/GS-CNT ( I f / I b = 6.33) is much higher than that of commercial catalyst, PtRu/Vulcan XC-72 ( I f / I b = 1.33), revealing the synergistic effects between GS and CNT on enhancing electrochemical activities of PtRu nanoclusters for the methanol oxidation and the carbon monoxide (CO) tolerance. Therefore, the 3-D GS-CNT nanocomposite is a promising support material for dispersing noble metal catalysts in the fuel cell applications.

A method of integrating hybrid thin films of graphene nanosheets (GNSs) and silver nanoparticles (AgNps) by in situ chemical reduction to prepare transparent conductive films (TCFs) is studied. The surface functional groups of graphite oxide (GO) serve as nucleation sites of silver ions for adsorption of AgNps. To fabricate conductive films with high transmittance, polyurethane (PU) nanofibers are introduced to help construct two-dimensional conductive networks consisting of AgNps and GNSs (AgNps–GNSs). This method requires only a low percentage of conducting AgNps–GNSs covering the transparent substrate, thereby improving the transmittance. The flexible GNSs serve as nanoscale bridges between conductive AgNps and PU nanofibers, resulting in a highly flexible TCF. The optical transmittance can be further increased after melting the PU nanofibers at 100 °C. A fused film obtained after electrospinning (ES) a PU solution for 120 s and immersion in 0.05 wt.% AgNp–GNS (5:1) solution has a surface resistance of 150 Ω/sq and 85% light transmittance. Mechanical testing shows that AgNps–GNSs on flexible substrates yield excellent robustness. Thus, TCFs with a 3:1 ratio of AgNps:GNSs have high conductivity, good mechanical durability, and barely one order of magnitude increase of surface resistance when bent to an angle of 90°.

This study develops a powerful strategy for fabricating the nitrogen-doped graphene sheets with good crystallinity, high specific surface area, and high percentages of pyridinic/graphitic-nitrogen structures. Due to the specified N-doping structures and high specific surface area of 719 m2 g−1, our N-doped graphene sheets show an excellent electrocatalytic activity for the oxygen reduction reaction (ORR). Keywords: Nitrogen-doped graphene sheet, Electrocatalyst, Oxygen reduction reaction

This study used sodium borohydride to reduce graphene oxide to graphene nanosheets (GNS), which contain the carboxylic functional group that becomes carboxyl (–COOH) or carboxylate anion (–COO−)-type in the acid or alkaline environment, respectively. The GNS with didodecyldimethylammonium bromide (DDAB) particles becomes hydrophilic (A-GNS) or hydrophobic (B-GNS) in property, through control of the pH value, which can be dispersed efficiently in water or a water/THF medium to deposit on the hydrophilic (poly(acrylic acid-acryl amide)) or hydrophobic (polystyrene) substrate for preparing the transparent, conductive film (TCF) by spin coating. The DDAB particles can be removed by washing with nitric acid, and the optimal performances of the TCFs are then obtained (HA-GNS and HB-GNS). The surface electrical resistance of HA-GNS (1.5 × 103 Ω □−1 at transmittance of 82%) is similar to that of HB-GNS (2.1 × 103 Ω □−1 at transmittance of 81%), which demonstrated that, not only the hydrophilic, but also the hydrophobic surface can be chosen to prepare the TCF when the hydrophilic and hydrophobic GNS can be prepared.

In this study, we fabricated optically transparent and electrically conductive multi-walled carbon nanotube (MWCNT) thin films using a spray-coating technique. The transparency and the electrical resistance of thin film are dependent on the nanotube content deposited on the polyethylene terephthalate (PET) substrate. Poly(acrylic acid) (PAA) and poly(N-vinyl pyrrolidone) (PVP) were used as adhesion promoters to improve MWCNT coating more significantly. The cross-linked polymer resulted in a superior bond between the MWCNTs and the substrates. The surface electrical resistance was significantly lower than the original sheet after nitric acid (HNO 3 ) treatment because of the removed surfactant and the increased interconnecting networks of MWCNT bundles, thus improving the electrical and optical properties of the films. Stronger interaction between the MWCNTs and the substrates resulted in lower decomposition of the polymer chain and less amounts of MWCNTs separated into the HNO 3 solution. The lower sheet electrical resistance of PVP/PAA-g-MWCNT conductive films on the PET substrate was because of a more complete conductive path with the cross-linked polymer than that without. Such an improved sheet of electrical resistance varied from 8.83 × 10 4 Ω/□ to 2.65 × 10 3 Ω/□ with 5.0 wt.% PVP/PAA-g-MWCNT sprayed on the PET after acid treatment.

Aggregation and restacking of graphene nanosheets (GNS) can be efficiently inhibited by decorating the silver nanoparticles on the surface of GNS to form GNS/silver (GNS-Ag) composites, which can construct high transparent and electrically conductive thin films. Silver nanoparticles act as a useful nanospacer and conductor, which not only increase the interlayer distance but also improve the electrical conductivity between layers. A two-step reduction process using sodium borohydride and ethylene glycol was also demonstrated reducing graphene oxide to GNS efficiently. The GNS-Ag composite films showed a maximum sheet resistance of 93 Ω□ −1 , while maintaining up to 78% light transmittance, which was two order of magnitude lower than that of GNS (8.2 × 10 3 Ω□ −1 , 81%), and the value of DC conductivity to optical conductivity ratio was 13.5 instead of 0.25.

A remarkable synergetic effect between the multi-graphene platelets (MGPs) and multi-walled carbon nanotubes (MWCNTs) in improving the mechanical properties and thermal conductivity of epoxy composites is demonstrated. Stacking of individual two-dimensional MGPs is effectively inhibited by introducing one-dimensional MWCNTs. Long and tortuous MWCNTs can bridge adjacent MGPs and inhibit their aggregation, resulting in a high contact area between the MGP/MWCNT structures and the polymer matrix. Scanning electron microscope images of the fracture surfaces of the epoxy matrix showed that MWCNT/MGP hybrid nanofillers exhibited higher solubility and better compatibility than individual MWCNTs and MGPs did. The tensile strength of GD400-MWCNT/MGP/epoxy composites was 35.4% higher than that of the epoxy alone, compared to only a 0.9% increase in tensile strength for MGP/epoxy composites over the epoxy compound. Thermal conductivity increased by 146.9% using GD400-MWCNT/MGP hybrid fillers and 23.9% for MGP fillers, compared to non-derivatised epoxy.

Stacking of individual graphene sheets (GS) is effectively inhibited by introducing one-dimensional carbon nanotubes (CNTs) to form a 3-D hierarchical structure which significantly enhances the electrochemical capacitive performances of GS-based composites. From SEM images, inserting proper quantity of CNTs as nanospacers can effectively impede the stacking of GS and enlarge the space between GS sheets, leading to obtain a highly porous nanostructure. The specific capacitance of GS-CNTs-9-1 (∼326.5 F g−1 at 20 mV s−1) is much higher than that of GS material (∼83 F g−1). Furthermore, the energy and power densities of GS-CNTs-9-1 are respectively as high as 21.74 Wh kg−1 and 78.29 kW kg−1, revealing that the hierarchical graphene-CNT architecture provides remarkable effects on enhancing the capacitive performance of GS-based composites. Therefore, the GS-CNT composites are promising carbon materials for supercapacitors.

Direct functionalized carbon nanotubes (CNTs) were utilized to form the heat flow network for epoxy composites through covalent integration. A method of preparing a fully heat flow network between benzenetricarboxylic acid grafted multi-walled carbon nanotubes (BTC-MWCNTs) and epoxy matrix is described. A Friedel–Crafts modification was used to functionalize MWCNTs effectively and without damaging the MWCNT surface. Raman spectra, X-ray photoelectron spectra and thermogravimetric analysis reveal the characteristics of functionalized MWCNTs. The scanning electron microscope images of the fracture surfaces of the epoxy matrix showed BTC-MWCNTs exhibited higher solubility and compatibility than pristine-MWCNTs. The MWCNTs/epoxy composites were prepared by mixing BTC-MWCNTs and epoxy resin in tetrahydrofuran, followed by a cross-linking reaction with a curing agent. The BTC was grafted onto the MWCNTs, creating a rigid covalent bond between MWCNTs and epoxy resin and forming an effective network for heat flow. The effect of functionalized MWCNTs on the formation of the heat flow network and thermal conductivity was also investigated. The thermal conductivity of composites exhibits a significant improvement from 0.13 to 0.96 W/m K (an increase of 684%) with the addition of a small quantity (1–5 vol%) of BTC-MWCNTs.

Flexible and lightweight graphene nanosheet (GN)/waterborne polyurethane (WPU) composites which exhibit high electrical conductivity and electromagnetic shielding performance were prepared. Covalently modifying GNs with aminoethyl methacrylate (AEMA; AEMA-GNs) through free radical polymerization effectively inhibited the restacking and aggregation of the GNs because of the -NH3(+) functional groups grafted on the AEMA-GNs. Moreover, the AEMA-GNs exhibited high compatibility with a WPU matrix with grafted sulfonated functional groups because of the electrostatic attraction, which caused the AEMA-GNs to homogeneously disperse in the WPU matrix. This homogeneous distribution enabled the GNs to form electrically conductive networks. Furthermore, AEMA-GNs with different amounts of AEMA segments were introduced into the WPU matrix, and the effects of the surface chemistry of the GNs on the electrical conductivity and EMI shielding performance of composites were investigated. AEMA-GN/WPU composites with a GN loading of 5 vol % exhibited remarkable electrical conductivity (approximately 43.64 S/m) and EMI shielding effectiveness (38 dB) over the frequency of 8.2 to 12.4 GHz.

Multiwalled carbon nanotube (MWCNT)/carbon fiber (CF)/vinyl ester (VE) laminate composites have been fabricated in this study. Pristine MWCNTs were treated with acid solution, which formed numerous oxygen-containing functional groups onto their surface, resulting in COOH-MWCNTs. Thereafter, acrylic functional groups were grafted onto the COOH-MWCNTs to generate acryl-MWCNTs. Three types of MWCNTs (pristine MWCNTs, COOH-MWCNTs, and acryl-MWCNTs) were used to reinforce the CF/VE-based composites. The dispersion of MWCNTs in the VE matrix and the interfacial interaction between MWCNTs and the VE matrix were investigated. Thereafter, the individual reinforcement efficiencies of these MWCNTs are compared. The flexural strength of the MWCNT/CF/VE composite with 1.0 phr acryl-MWCNTs content is 29.8% greater than that of neat CF/VE composites, and the flexural modulus of the MWCNT/CF/VE composite is 9.9% higher than that of neat CF/VE composites. Compared with neat CF/VE composites, 1.0 phr acryl-MWCNT/CF/VE composites exhibit an approximately 19.9 °C increase in glass transition temperature (Tg). The coefficients of thermal expansion significantly decreased from 47.2 ppm/°C of the neat CF/VE composites to 35.6 ppm/°C of the acryl-MWCNTs/CF/VE composites with 1 phr acryl-MWCNT content. This study provides a method for developing acryl-MWCNT/CF/VE composites with good dispersion of MWCNTs in VE matrix and strong interfacial interaction between the MWCNTs and VE matrix for enhancing the stress transfer from VE matrix to CF reinforcement.

Uniform and high-quality graphene oxide thin films were prepared using a dip-coating approach and were reduced to highly electrically conductive graphene nanosheet (GN) transparent conductive films (TCFs) using hydriodic acid. Silver nanowires (AgNWs), which were modified using thiophenol and exhibited a high aspect ratio and high electrical conductivity, were deposited on the surfaces of the GN TCFs through π–π interactions between the aromatic functional groups on the AgNWs and GNs to form high-performance GN/AgNW TCFs. The GN/AgNW hybrid nanomaterial films exhibited a sheet resistance of 71 Ω □−1 and 85% light transmittance.

A simple method was developed to assemble graphite oxide (GO) densely onto electrospun (ES) polyamide 66 (PA66) nanofibrous membranes, used as a guide for the deposition of graphene nanosheet (GNS) conductive networks for preparing transparent conductive thin film (TCF). The main advantage of this technique by comparison with previous methods is that graphene does not form a uniform coating, but a percolated conductive network, when guided by PA66 nanofiber templates. A low surface coverage of the transparent substrate by GNS resulted in high transmittance. Polyvinylpyrrolidone-stabilized GO (PVP-GO) was prepared as a modifier for improving the adsorption to the nanofibers. The resulting PVP-GO material could adsorb well on PA66 nanofibers due to stronger hydrogen bonds. Hence, a lower sufficient concentration of PVP-GO (0.050 wt%) solution was required than that for GO solution (0.100 wt%) to fabricate a complete conductive path through a possible enriched adsorption process. For TCF applications, a reduction step is essential because as-deposited GO is non-conductive. In this work, we reduced GO to GNS by a combination of chemical reduction and thermal annealing. The TCF optical transmittance also could be improved after thermal annealing at 350 °C above the PA66 melting point. Light scattering by PA66 nanofibers was found as the main cause of reduced transmittance. A fused film, obtained after electrospinning PA66 solution for 120 s, and immersing in 0.050 wt% PVP-GO solution, exhibits a surface resistance of 8.6 × 10³ Ω/square, while maintaining 88% light transmittance.

This study prepared graphene nanosheet (GNS)-based transparent, conductive films (TCFs) by a self-assembly method. We used the water-borne polyurethane (WPU, with sulfonate functional groups) film as the substrate. Aggregation and restacking of the GNS were inhibited efficiently by attracting the octadecyl trimethyl ammonium chloride surfactant (cationic surfactant) to the surface of the GNS (GNS-O), which can in turn attract sulfonate groups to the WPU surface. The GNS-O was deposited on WPU to form TCFs. We obtained highly transparent and electrically conductive thin films after treatment with nitric acid (GNS-OA). The GNS-OA composite films showed a maximum sheet electrical resistance of 1.5 × 103 Ω □−1, with a light transmittance of up to 79% and a ratio of DC conductivity to optical conductivity of 0.88.

This study examined the intercalation reaction of graphite oxide (GO) with poly(acryl amide)/poly(acrylic acid) (PMA) as a method to control the spacing between GOs. The interlayer spacing of GO was increased from 0.80 to 1.21 nm by grafting PMA on the GO surface. To fabricate transparent conductive films (TCFs), GOs must be reduced to graphene nanosheets (GNS) by a two-step chemical reduction with increased conductivity. The intercalated polymer chains of poly(acrylic acid) between GNS were extended as the carboxylic acid groups were deprotonated by the Na+ ions of NaBH4 on reduction, which efficiently inhibits GNS aggregation and restacking. The Na+ bonding on the polymer chains also facilitates electron transfer between the layers, yielding lower surface electrical resistance at the same GNS film thickness. The PMA grafted GNS (NE-PMA-GNS) composite films show the lowest sheet resistance of 2.11 × 102 Ω □−1, which is one order of magnitude less than that without grafting polymer (NE-GNS, 1.86 × 103 Ω □−1); moreover, instead of 0.22, the ratio of DC conductivity to optical conductivity (σDC/σOP) was 2.60. The higher σDC/σOP ratio indicates a higher TCFs performance.

Optically transparent and electrically conductive thin films composed of multi-walled carbon nanotube (MWCNT) reinforced polymethyl methacrylate/acrylic acid (PMMA/AA) were fabricated using a wire coating technique. Poly(acrylic acid) controls the level of MWCNT dispersion in aqueous mixtures and retains the well-dispersed state in the polymer matrix after solidification resulting from extended polymer chains by adjusting the pH value. The exfoliating the MWCNT bundles by extended polymer chains results in the excellent dispersion of MWCNT. It causes a lower surface electrical resistance at the same MWCNT content. The hydrophilic functional groups (-COO( - )NA( + )) also caused a decrease in the crystallization of PMMA and led to an increase in the transmittance.