Embedded ultra-high stability flexible transparent conductive films based on exfoliated graphene-silver nanowires-colorless polyimide.

Transparent conductive films with high stability were prepared by embedding silver nanowires in colorless polyimide and adding a protective layer of exfoliated graphene. The films exhibit great light transmission and conductivity with a sheet resistance of 22 Ω sq-1at transmittance of 83%. Due to its special embedded structure, the conductive layer can withstand several peeling experiments without falling off. In addition, the most outstanding advantage is the ultra-high stability of the films, including high mechanical robustness, strong chemical corrosion resistance and high operating voltage capacity. The organic light-emitting diode devices prepared based on this transparent conductive electrode exhibit comparable efficiency to indium tin oxide (ITO) based devices, withC.E.max= 2.78 cd A-1,P-1.E.max= 1.89 lm W-1,EQEmax= 0.89%. Moreover, the efficiencies were even higher than that of ITO devices when the operating voltage of the device exceeds 5 V. The above performances show that the transparent conductive electrode based on this structure has high potential for application in organic electronic devices.

Highly transparent, low sheet resistance and stable Tannic acid modified-SWCNT/AgNW double-layer conductive network for organic light emitting diodes.

In this paper, we used tannic acid (TA) functionalized carbon nanotubes (TCNTs), and silver nanowires (AgNWs) to construct a new type of transparent conductive film (TCF) with a double-layered conductive network structure. The hybrid film exhibits excellent light transmittance, high electrical conductivity, ultra-flexibility, and strong adhesion. These outstanding performances benefit from the filling and adhesion of hydrophilic TCNT layers to the AgNW networks. Besides, we introduced the post-treatment process of mechanical pressing and covering polymer conductive polymer PEDOT:PSS, which obtained three layers of TCNT/AgNW/PEDOT hybrid film and greatly improved the comprehensive properties. The hybrid film can reach a sheet resistance of 9.2 Ω sq-1 with a transmittance of 83.4% at 550 nm wavelength, and a low root mean square (RMS) roughness (approximately 3.8 nm). After 10 000 bends and tape testing, the conductivity and transmittance of the hybrid film remain stable. The resistance of the film has no significant degradation after 14 d of exposure to high temperature of 85 °C and humidity of 85%, indicating excellent stability. The organic light-emitting diodes (OLEDs) with TCNT/AgNW/PEDOT hybrid film as anode exhibit high current density and luminosity, confirming this process has considerable potential application in photovoltaic devices.

Flexible Wearable Electronic Fabrics with Dual Functions of Efficient EMI Shielding and Electric Heating for Triboelectric Nanogenerators.

Traditional conductive fabrics are prepared by the synthesis of conductive polymers and the coating modification of metals or carbon black conductive materials. However, the conductive fabrics cause a significant decline in performance after washing or mechanical wear, which limits their application. Moreover, the single function of the traditional conductive fabric is also the reason that limits its wide application. In order to prepare a wearable, stable, high-performance, washable, multifunctional conductive fabric, we have carried out related research. In this work, polydopamine was used as a bonding layer, an adsorption reduction layer, and a protective layer to improve the bonding between silver nanoparticles and carbon nanotubes (CNTs) on the polyester fabric surface so as to prepare a multifunctional conductive fabric with a high-stability "sandwich" structure, in which a Ag-NPS@CNT structure acting as an intermediate conductive layer formed on the inner layer PDA@CNT by electroless silver plating and the outermost layer PDA@CNT coated on the surface of the intermediate conductive layer by the impregnation-drying method. The sheet resistance of an E-Fabric can reach 2.11 Ω/□ due to the uniform and dense conductive path formed by the special structure Ag-NPs@CNT. At a low voltage of 1.5 V, the E-Fabric can reach 117 °C in 50 s and remain stable. The electrical conductivity and current heating properties of the E-Fabric remain good even after multiple washing or bending tests. Due to its stable and outstanding electrical conductivity, the E-Fabric has an electromagnetic shielding efficiency (SET) of 35.3 dB in the X-band (8.2-12.4 GHz). In addition, E-Fabric-based spin-coated poly(methyl methacrylate) or polydimethylsiloxane electrodes exhibit excellent performance in nanogenerators. Through the low-frequency friction of the human body, transient voltages up to 4 V can be generated from a 2 cm × 2 cm electrode sample. The output power of a single generator can reach about 12 nW/cm2. Therefore, an E-Fabric is considered to have great potential in the fields of electric heating, electromagnetic shielding, and smart wearable devices.

Low Surface Roughness Graphene Oxide Film Reduced with Aluminum Film Deposited by Magnetron Sputtering.

Graphene film has wide applications in optoelectronic and photovoltaic devices. A novel and facile method was reported for the reduction of graphene oxide (GO) film by electron transfer and nascent hydrogen produced between aluminum (Al) film deposited by magnetron sputtering and hydrochloric acid (HCl) solution for only 5 min, significantly shorter than by other chemical reduction methods. The thickness of Al film was controlled utilizing a metal detection sensor. The effect of the thickness of Al film and the concentration of HCl solution during the reduction was explored. The optimal thickness of Al film was obtained by UV-Vis spectroscopy and electrical conductivity measurement of reduced GO film. Atomic force microscope images could show the continuous film clearly, which resulted from the overlap of GO flakes, the film had a relatively flat surface morphology, and the surface roughness reduced from 7.68 to 3.13 nm after the Al reduction. The film sheet resistance can be obviously reduced, and it reached 9.38 kΩ/sq with a high transmittance of 80% (at 550 nm). The mechanism of the GO film reduction by electron transfer and nascent hydrogen during the procedure was also proposed and analyzed.

Bilayer and three dimensional conductive network composed by SnCl2 reduced rGO with CNTs and GO applied in transparent conductive films.

Graphene oxide (GO), reduced graphene oxide (rGO) and carbon nanotubes (CNTs) have their own advantages in electrical, optical, thermal and mechanical properties. An effective combination of these materials is ideal for preparing transparent conductive films to replace the traditional indium tin oxide films. At present, the preparation conditions of rGO are usually harsh and some of them have toxic effects. In this paper, an SnCl2/ethanol solution was selected as the reductant because it requires mild reaction conditions and no harmful products are produced. The whole process of rGO preparation was convenient, fast and environmentally friendly. Then, SEM, XPS, Raman, and XRD were used to verify the high reduction efficiency. CNTs were introduced to improve the film conductive property. The transmittance and sheet resistance were the criteria used to choose the reduction time and the content ratios of GO/CNT. Thanks to the post-treatment of nitric acid, not only the by-product (SnO2) and dispersant in the film are removed, but also the doping effect occurs, which are all conducive to reducing the sheet resistances of films. Ultimately, by combining rGO, GO and CNTs, transparent conductive films with a bilayer and three-dimensional structure were prepared, and they exhibited high transmittance and low sheet resistance (58.8 Ω/sq. at 83.45 T%, 47.5 Ω/sq. at 79.07 T%), with corresponding [Formula: see text] values of 33.8 and 31.8, respectively. In addition, GO and rGO can modify the surface and reduce the film surface roughness. The transparent conductive films are expected to be used in photoelectric devices.

Tannic acid modified graphene/CNT three-dimensional conductive network for preparing high-performance transparent flexible heaters.

In this paper, the eco-friendly plant polyphenol, tannic acid (TA) was demonstrated as a non-covalent modifier for carbon nanotubes (CNTs), as well as a stripping medium to achieve exfoliated graphite to graphene by microfluidization. High-performance transparent flexible heater (TFH) with an embedded structure had been successfully fabricated by integrating conductive nanocomposites (TA-functionalized grapheme/TA-functionalized CNT/PEDOT:PSS; TG/TCNT/PEDOT) into waterborne polyurethane (WPU) film. Such a film exhibited favorable optical transmittance and sheet resistance (T = ca. 80% at 550 nm, Rs = 62.5 Ω/sq.), low root mean square (rms) roughness (approximately 0.37 nm), excellent adhesion and mechanical stability (the sheet resistance remained almost constant after 1000 bending cycle test for the bending radius of 10 mm), which are ideal as transparent heaters with high thermal efficiency. For TG/TCNT/PEDOT-WPU TFHs, the temperature increased rapidly and reached a steady state within 20 s with the maximum temperature reached to 116 °C, when the applied voltage was 20 V. Moreover, no variation in temperature was observed after the repeated heating-cooling tests and long-time stability test, indicating that TG/TCNT/PEDOT-WPU TCFs can be used as high performance TFHs. These TFH's are expected to be suitable for vehicle defrosting, smart windows, portable heating, smart wearable devices, etc.

Improvement of Corrosion Resistance of Waterborne Polyurethane Coatings by Covalent and Noncovalent Grafted Graphene Oxide Nanosheets.

The amphiphilic graphene derivative was prepared by covalent grafting of graphene oxide (GO) with isophorone diisocyanate and N,N-dimethylethanolamine and then noncovalent grafting of GO with sodium dodecylbenzenesulfonate. The results obtained from infrared spectroscopy, X-ray photoelectron spectroscopy, thermal gravimetric analysis, and X-ray diffraction analysis revealed that the short chains were successfully grafted onto the surface of GO. Subsequently, scanning electron microscopy and optical microscopy results showed that the modified GO (IP-GO) has the best dispersibility and compatibility than GO and reduced GO in the waterborne polyurethane matrix. The relationship between the corrosion resistance of composite coatings and the dispersibility of the graphene derivative and the compatibility of the graphene derivative with a polymer matrix were discussed. The anticorrosive properties were characterized by electrochemical impedance spectroscopy analysis and salt spray tests. Through a series of anticorrosion tests, it is concluded that the anticorrosion performance of a composite coating with 0.3 wt % IP-GO is significantly improved. The excellent anticorrosion performance is due to the perfect dispersion and good compatibility of IP-GO in waterborne polyurethane.

Carbon nanotube-based flexible electrothermal film heaters with a high heating rate.

High-performance, flexible film heaters with carbon nanotube transparent conducting films are easily fabricated by both a rod-coating method and a spraying method. The main conclusion we have reached is that the film demonstrates a heating rate of 6.1°C s-1 at 35 V and sheet resistance as low as 94.7 Ω sq-1 with 72.04% optical transmittance at a wavelength of 550 nm by the spraying method after a series of post-treatment processes with acid and distilled water. Then, we adopt a mathematical method of nonlinear fitting to simulate the collected experimental data and the functions effectively. Furthermore, through analysis of the formula, the correlation between temperature and time is well explained. Therefore, carbon nanotube-based, flexible, transparent heaters exhibit high electrothermal performance and are expected to find different applications, e.g. various functional devices such as heating materials, heatable smart windows or dining tables.