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With the rapid development of high-power-density electronic devices, interface thermal resistance has become a critical barrier for effective heat management in high-performance electronic products. Therefore, there is an urgent demand for advanced thermal interface materials (TIMs) with high cross-plane thermal conductivity and excellent compressibility to withstand increasingly complex operating conditions. To achieve this aim, a promising strategy involves vertically arranging highly thermoconductive graphene on polymers. However, with the currently available methods, achieving a balance between low interfacial thermal resistance, bidirectional high thermal conductivity, and large-scale production is challenging. Herein, we prepared a graphene framework with continuous filler structures in in-plane and cross-plane directions by bonding corrugated graphene to planar graphene paper. The interface interaction between the graphene paper framework and polymer matrix was enhanced via surface functionalization to reduce the interface thermal resistance. The resulting three-dimensional thermal framework endows the polymer composite material with a cross-plane thermal conductivity of 14.4 W·m−1·K−1 and in-plane thermal conductivity of 130 W·m−1·K−1 when the thermal filler loading is 10.1 wt%, with a thermal conductivity enhancement per 1 wt% filler loading of 831%, outperforming various graphene structures as fillers. Given its high thermal conductivity, low contact thermal resistance, and low compressive modulus, the developed highly thermoconductive composite material demonstrates superior performance in TIM testing compared with TFLEX-700, an advanced commercial TIM, effectively solving the interfacial heat transfer issues in electronic systems. This novel filler structure framework also provides a solution for achieving a balance between efficient thermal management and ease of processing. [ABSTRACT FROM AUTHOR]

Flexible graphene‐based paper electrodes (FGPEs) are a new class of study and the research on this electrode material has been carried out for approximately ten years. FGPEs have many advantages compared to classical solid electrodes such as being flexible, foldable, adaptable to flexible electronics, being cut, easily shaped, and effective and adjustable modification. In this work, the applicability of FGPEs modified with polyindole (PIN) thin films and zinc oxide nanoparticles (ZnO‐NPs) to energy‐storage systems as a supercapattery design is presented, and especially the limitations of ZnO‐NPs for energy‐storage applications are revealed to inform researchers working for a similar purpose. Capacitance calculations have been performed using both cyclic voltammetry (CV) and galvanostatic charge‐discharge (GCD) experiments. It was observed that the rGO/PIN paper demonstrated almost 30 times more energy‐storage capacity than that of the rGO/PIN/ZnO paper due to the electrochemical instability of ZnO‐NPs on the flexible electrode platform at the applied potential region in 1.0 M HClO4 solution. The rGO/PIN paper with a highly flexible property exhibited an energy density of 74.5 W h cm−2 and a power density of 2258 W cm−2 at a current density of 2.2 mA cm−2, revealing hopeful results for future modular and flexible approaches. [ABSTRACT FROM AUTHOR]

This paper presents the results of research on the impact of graphene paper on selected bacterial strains. Graphene oxide, from which graphene paper is made, has mainly bacteriostatic properties. Therefore, the main goal of this research was to determine the possibility of using graphene paper as a carrier of a medicinal substance. Studies of the degree of bacterial inhibition were performed on Staphylococcus aureus and Pseudomonas aeruginosa strains. Graphene paper was analyzed not only in the state of delivery but also after the incorporation of the antibiotics ciprofloxacin, cefazolin, and methicillin into its structures. In addition, Fourier-Transform Infrared Spectroscopy, contact angle, and microscopic analysis of bacteria on the surface of the examined graphene paper samples were also performed. Studies have shown that graphene paper with built-in ciprofloxacin had a bactericidal effect on the strains of Staphylococcus aureus and Pseudomonas aeruginosa. In contrast, methicillin, as well as cefazolin, deposited on graphene paper acted mainly locally. Studies have shown that graphene paper can be used as a carrier of selected medicinal substances. [ABSTRACT FROM AUTHOR]

We present a facile one-step hydrothermal method for the fabrication of free-standing graphene paper using aqueous graphene oxide (GO) dispersion as the starting material. Notably, the method does not require the use of any additives for the reduction and preparation of the graphene paper. The resulting graphene paper exhibits a high degree of reduction, as confirmed by X-ray photoelectron spectroscopy (XPS) analysis, revealing a carbon-to-oxygen (C/O) ratio of ∼7. The fabricated graphene paper also demonstrates excellent conductivity, with a measured value of ∼1900 S/m, and sheet resistance of around 100 Ω/sq. Furthermore, the energy storage capability of the graphene paper based electrode is evaluated, which shows a promising specific capacity of 249 F/g at a current density of 1 A/g in 1M H2SO4 as the ionic medium. Additionally, the electrode has also demonstrated remarkable energy density and power density values of 28.68 Wh/Kg and 455 W/Kg, respectively. Overall, the resulting graphene paper exhibits high conductivity and excellent electrochemical performance, making it a promising candidate for various energy storage applications.

With the increase in heat power density in modern integrating electronics, thermal interface materials (TIM) that can efficiently fill the gaps between the heat source and heat sinks and enhance heat dissipation are urgently needed owing to their high thermal conductivity and excellent mechanical durability. Among all the emerged TIMs, graphene-based TIMs have attracted increasing attention because of the ultrahigh intrinsic thermal conductivity of graphene nanosheets. Despite extensive efforts, developing high-performance graphene-based papers with high through-plane thermal conductivity remains challenging despite their high in-plane thermal conductivity. In this study, a novel strategy for enhancing the through-plane thermal conductivity of graphene papers by in situ depositing AgNWs on graphene sheets (IGAP) was proposed, which could boost the through-plane thermal conductivity of the graphene paper up to 7.48 W m−1 K−1 under packaging conditions. In the TIM performance test under actual and simulated operating conditions, our IGAP exhibits strongly enhanced heat dissipation performance compared to the commercial thermal pads. We envision that our IGAP as a TIM has great potential for boosting the development of next-generation integrating circuit electronics. [ABSTRACT FROM AUTHOR]

This paper presents the results of research on the impact of graphene paper on selected bacterial strains. Graphene oxide, from which graphene paper is made, has mainly bacteriostatic properties. Therefore, the main goal of this research was to determine the possibility of using graphene paper as a carrier of a medicinal substance. Studies of the degree of bacterial inhibition were performed on Staphylococcus aureus and Pseudomonas aeruginosa strains. Graphene paper was analyzed not only in the state of delivery but also after the incorporation of the antibiotics ciprofloxacin, cefazolin, and methicillin into its structures. In addition, Fourier-Transform Infrared Spectroscopy, contact angle, and microscopic analysis of bacteria on the surface of the examined graphene paper samples were also performed. Studies have shown that graphene paper with built-in ciprofloxacin had a bactericidal effect on the strains of Staphylococcus aureus and Pseudomonas aeruginosa. In contrast, methicillin, as well as cefazolin, deposited on graphene paper acted mainly locally. Studies have shown that graphene paper can be used as a carrier of selected medicinal substances.

In this work, the electrical properties of graphene papers were investigated with the aim of developing pressure sensor prototypes for measuring pressures up to 2 kPa. In order to determine which graphene paper would be the most suitable, three different types of graphene papers, synthesized by different routes, were prepared and electrically characterized. The results of electrical characterizations, in terms of electrical conductivity and sheet resistance of graphene papers, are presented and discussed. Prototypes of pressure sensors are proposed, using graphene papers obtained by chemical oxidation (graphene oxide and reduced graphene oxide) and by electrochemical exfoliation. The prototypes were tested in static compression/decompression tests in the working range of 0 kPa to 1.998 kPa. The compression/decompression sensitivity values observed in these prototype sensors ranged from 20.8% ΔR/kPa for graphene sensors obtained by electrochemical exfoliation to 110.7% ΔR/kPa for those prepared from graphene oxide obtained by chemical oxidation. More expressive sensitivity values were observed for the sensors fabricated from GO, intermediate values for those made of rGO, while prototypes made of EG showed lower sensitivity.

The present work aims to evaluate the manufacturing processes of free-standing graphene oxide (GO)/reduced graphene oxide(rGO)/carbon nanotube (MWCNT) papers-like and the effect on electrical conductivities after annealing treatment. The pure GO and the hybrid papers were obtained by vacuum filtration and submitted to mild thermal annealing at 400 °C under an argon atmosphere. Analyses comparing the carbon paper-like materials before and after thermal treatment were done by thermogravimetric analysis (TGA), Raman spectroscopy, scanning electron microscopy (SEM), and electrical conductivity measurements. The characterization results show the annealing process effect on the morphology of paper materials. The GO papers and the hybrid (GO/rGO/MWCNT) exhibited good free-standing structure properties. The SEM results suggest the formation of gas void due to the thermal treatment. TGA and Raman results showed the thermal reduction and restoration of the carbon sp2 network of the graphene oxide induced by thermal treatment. The thermal treatment was responsible for changing the almost insulator characteristic of free-standing pure GO paper, achieving an electrical conductivity of 752 S/m, and improving 45% of the free-standing hybrid carbon nanomaterials papers (GO/rGO/MWCNT) electrical conductivity, achieving the value of 1020 S/m.

In this work, the electrical properties of graphene papers were investigated with the aim of developing pressure sensor prototypes for measuring pressures up to 2 kPa. In order to determine which graphene paper would be the most suitable, three different types of graphene papers, synthesized by different routes, were prepared and electrically characterized. The results of electrical characterizations, in terms of electrical conductivity and sheet resistance of graphene papers, are presented and discussed. Prototypes of pressure sensors are proposed, using graphene papers obtained by chemical oxidation (graphene oxide and reduced graphene oxide) and by electrochemical exfoliation. The prototypes were tested in static compression/decompression tests in the working range of 0 kPa to 1.998 kPa. The compression/decompression sensitivity values observed in these prototype sensors ranged from 20.8% ΔR/kPa for graphene sensors obtained by electrochemical exfoliation to 110.7% ΔR/kPa for those prepared from graphene oxide obtained by chemical oxidation. More expressive sensitivity values were observed for the sensors fabricated from GO, intermediate values for those made of rGO, while prototypes made of EG showed lower sensitivity. [ABSTRACT FROM AUTHOR]

High-performance electromagnetic interference (EMI) shielding and thermal management materials with ultraflexibility, high strength, outstanding stability under mechanical deformation, and low cost are urgently demanded for modern integrated electronic and telecommunication systems. However, the creation and application of such desirable materials is still a potent challenge. Herein, we develop such a high-performance multifunctional multilayer composite, known as vertically aligned carbon nanotube@graphene paper/polydimethylsilane (VACNT@GP/PDMS), which involves the in situ growth of VACNTs onto GPs, vertical stacking of VACNT@GP layers, and infiltration of PDMS. The EMI shielding and mechanical properties of multilayer composites can be dramatically increased by increasing the number of VACNT@GP layers. Benefiting from the conduction loss in highly conductive GPs and polarization of huge VACNT–PDMS–VACNT microcapacitor networks, the multilayer composite with four VACNT@GP layers exhibits a superior EMI SE of 106.7 dB over a broad bandwidth of 32 GHz, covering the entire X-, Ku-, K-, and Ka-bands, which far suppresses the values of most of the reported EMI shielding materials. Moreover, the multilayer composites show excellent thermal management performance such as a high Joule-heating temperature at low supplied voltages, rapid response time, and sufficient heating stability. In addition, remarkable flexibility, high tensile strength (up to 13.4 MPa), and super stability under mechanical deformation (nearly no EMI SE degradation after repeatedly bending 10,000 times) are also discovered. These excellent comprehensive properties, along with the ease of low-cost mass production, pave the way for the practical applications of multilayer VACNT@GP/PDMS composites in EMI shielding and thermal management. [ABSTRACT FROM AUTHOR]

Real‐time and continuous monitoring of ultraviolet (UV) radiation in daily activity is critical in diverse fields ranging from personal fitness, cosmetics, to medical aspects. Here, a wearable UV monitoring patch that can be easily fixed/removed at desired locations and provide real‐time and continuous UVA levels in daily life is developed. The wearable patch consists of a highly sensitive, flexible graphene sensor for UVA measurement and a multifunctional fabric patch integrated with commercial electronic components for signal processing, wireless transmission. To achieve a high sensitive UVA sensor with high flexibility and long‐term stability, porous reduced graphene oxide (pRGO) papers are fabricated by simple solvent evaporation followed by thermochemical reduction. The flexible UVA sensors based on pRGO papers feature a high UVA photoresponsivity of 125 mA W−1, which is comparable to that of a commercial silicon‐based UV sensor. Furthermore, the polydimethylsiloxane‐encapsulated pRGO (PDMS‐pRGO) sensors exhibit stable UVA photoresponse characteristics that is maintained under severe conditions, such as a large number of bending cycles, thermal heating, and high humidity. The use of wearable patches that enable real‐time, wireless monitoring of personal UVA levels in various practical applications are demonstrated. [ABSTRACT FROM AUTHOR]

The possibility of exfoliating graphite into graphene sheets allows the researchers to produce a material, termed "graphene paper" (G‐paper), conductive as graphite but more flexible and processable. G‐paper is already used for electronic applications, like conductors, antennas, and heaters, outperforming metal conductors thanks to its high flexibility, lightness, chemical stability, and compatibility with polymeric substrates. Here, the effectiveness in the use of G‐paper for the realization of electrodes on flexible plastic substrates and textiles, and their applicability as amperometric sensors are demonstrated. The performance of these devices is compared with commercial platforms made of carbon‐based inks, finding that they outperform commercial devices in sensing nicotinamide adenine dinucleotide (NADH), a key molecule for enzymatic biosensing; the electrodes can achieve state‐of‐the‐art sensitivity (107.2 μA mm−1 cm−2) and limit of detection (0.6 × 10−6m) with no need of additional functionalization. Thanks to this property, the stable deposition of a suitable enzyme, namely lactate dehydrogenase, on the electrode surface is used as a proof of concept of the applicability of this new platform for the realization of a biosensor. The possibility of having a single material suitable for antennas, electronics, and now sensing opens new opportunities for smart fabrics in wearable electronic applications. [ABSTRACT FROM AUTHOR]

Glucose electrochemical sensors based on nanostructures of CuO/Cu(OH)2 onto graphene paper were prepared by thermal (solid) and nanosecond pulsed laser (molten phase) dewetting of a CuO layer 6 nm thin deposited by sputtering. Dewetted systems, obtained without the use of any binder, act as array of nanoelectrodes. Solid state and molten phase dewetting produce nanostructures of copper oxide-hydroxide with different average size, shape and surface composition. Molten phase dewetting originates particles with size below 100 nm, while solid state dewetting produces particles with average size of about 200 nm. Moreover, molten phase dewetting produce drop-shaped nanostructures, conversely nanostructures derived from solid state dewetting are multifaceted. X-ray photoelectron spectroscopy (XPS) characterization revealed that the surface of nanostructures is formed by a copper(II) species CuO and Cu(OH)2. Shape of anodic branch of the cyclic voltammograms of glucose in alkali solution evidenced a convergent diffusion mechanism. Analytical performances in amperometric mode are as good as or better than other sensors based on copper oxide. Amperometric detection of glucose was done at potential as low as 0.4 V versus saturated calomel electrode by both types of electrodes. Linear range from 50 ÎĽ M to 10 mM, sensitivity ranging from 7 to 43 ÎĽ A cmâˆ'2 mMâˆ'1 and detection limit of 7 ÎĽ M was obtained. Good analytical performances were obtained by laser dewetted electrodes with a low copper content up to 1.2 by atoms percentage of the surface. Analytical performance of the proposed electrodes is compliant for the determination of glucose both in blood serum, saliva or tear. [ABSTRACT FROM AUTHOR]

Free-standing flexible supercapacitive electrodes have practical application for wearable energy storage devices. In this paper, graphene paper (GP), a flexible electrode substrate, was prepared by one-step reduction of graphene oxide (GO) using HI solution. GP can be used independently as a flexible electrode with specific capacitance of 227 F/g. In order to make up for the shortage of GP specific capacitance storage, polyaniline (PANI) with high specific capacitance and good electrical conductivity was selected to composite with GP by electrochemical polymerization approach. This method to fabricate electrode material by direct electrochemical polymerization avoids the use of conductive binder and organic solvent. Owing to the specific capacitance contribution of PANI and GP, the PANI/GP composites exhibit higher specific capacitance when the polymerization time is 30 s and the polymerization voltage is 0.8 V. At 1 A/g current density, the specific capacitance of composite is up to 759 F/g, which is 3.34 times of neat GP. [ABSTRACT FROM AUTHOR]

With the increase in heat power density in modern integrating electronics, thermal interface materials (TIM) that can efficiently fill the gaps between the heat source and heat sinks and enhance heat dissipation are urgently needed owing to their high thermal conductivity and excellent mechanical durability. Among all the emerged TIMs, graphene-based TIMs have attracted increasing attention because of the ultrahigh intrinsic thermal conductivity of graphene nanosheets. Despite extensive efforts, developing high-performance graphene-based papers with high through-plane thermal conductivity remains challenging despite their high in-plane thermal conductivity. In this study, a novel strategy for enhancing the through-plane thermal conductivity of graphene papers by in situ depositing AgNWs on graphene sheets (IGAP) was proposed, which could boost the through-plane thermal conductivity of the graphene paper up to 7.48 W m−1 K−1 under packaging conditions. In the TIM performance test under actual and simulated operating conditions, our IGAP exhibits strongly enhanced heat dissipation performance compared to the commercial thermal pads. We envision that our IGAP as a TIM has great potential for boosting the development of next-generation integrating circuit electronics.

Li metal is the prospective candidate of next generation anode materials. However, the growth of dendritic Li during electrochemical cycling has severely hindered the practical application of rechargeable Li-metal batteries. Herein, "seaweed" graphene paper (SGP) is designed for 3D matrix of Li metal anode to address the growth of dendrites. SGP has abundantly exposed edges of graphene sheets and realizes ultrahigh density nucleation. Compared with nonuniform lithium deposition on parallelly stacked GP which has been observed by in-situ scanning electron microscopy, electrochemical deposition behavior of Li in SGP manifests as uniformly distributed granular lithium. Significant decrease of nucleation barrier can be observed during the dendrite-free deposition. With the elimination of dendritic Li growth and excellent stability of SGP host, the lithium anode based on SGP can run over 2500 cycles without short circuit and exhibits low voltage hysteresis. When matched with cathode LiCoO2, the full battery also presents stable cycling. There is no trace of lithium dendrite even after 1200 cycles which proves continuously regulating effect on lithium dendrites by SGP host. This work further develops potential application of graphene materials in the Li anode with high reversibility for stable cycling Li metal batteries. Ultrahigh density nucleation is realized by changing the stacked manner of graphene sheets. Compared with parallelly stacked graphene paper (GP), "seaweed" stacked GP (SGP) has more exposed edges which can supply abundant nucleation sites. As the host, SGP eliminates the growth of dendritic Li during cycling and assembled Li@SGP symmetrical batteries can stably plating/stripping for over 2500 cycles at 1.0 mA cm−2. [Display omitted] • Nonuniform lithium deposition on parallelly stacked GP was observed by in-situ SEM. • Ultrahigh density nucleation realized by "seaweed" GP with abundant exposed edges leads to dendrite-free deposition. • Corresponding batteries present extraordinary long-cycle dendrite-free performance. [ABSTRACT FROM AUTHOR]

In this work we describe the Square Wave Anodic Stripping Voltammetry (SWASV) electrochemical technique for the determination of lead (Pb2+) and cadmium (Cd2+) metal ions at concentration of sub-part per billion (ppb) in aqueous solution. Moreover, simple and low-cost procedures for the fabrication of high performance working nano-electrode are reported. The electrode structure consists of a graphene paper (GP) $240~\mu \text{m}$ thick with the function of electrical conductor and substrate, a layer of nafion 0.5- $0.7~\mu \text{m}$ thick onto the graphene paper and bismuth nanoparticles embedded in the nafion thin layer. The bismuth nanoparticles were fabricated by electrodeposition starting from Bi(III) ions, employing a key step of hydrogen ions of nafion $\text{H}^{\mathbf {+}}$ exchange with bismuth ions Bi(III). This procedure is aimed to improve the bismuth nanoparticles concentration. The SWASV applied to the low-cost nanoelectrode allows detecting Pb2+ and Cd2+ at concentration as low as 0.1 ppb. [ABSTRACT FROM AUTHOR]

The thermal conductivities of low-defect 3D graphene materials synthesized by CVD processes have been investigated experimentally. The materials investigated were prepared using pure Ni powdered catalyst (giving graphene paper, GP, so called because the bulk structure is a paper, with a 3-dimensional interconnected graphene microstructure), or nickel/polymer catalyst (giving polymer-assisted graphene paper, pGP, or, with double-thick nickel/polymer catalyst, pGP×2), all with and without additional compression. Room-temperature thermal conductivity of the graphene materials generally increased with increasing density, with values as high as 40 W m−1 K−1 and specific thermal conductivity of up to 220 mW m2 kg−1 K−1, although the porosity was quite high (~90% or higher). We show that larger graphene flakes and higher density lead to better intrinsic thermal conductivity. For compressed pGP×2, we investigated the temperature-dependence of the specific thermal conductivity, and found a broad maximum from T ~ 270 to 330 K, at a value of 230 ± 20 mW m2 kg−1 K−1.

Abstract Raman spectroscopy has been widely used to measure thermophysical properties of 2D materials. The local intense photon heating induces strong thermal nonequilibrium between optical and acoustic phonons. Both first principle calculations and recent indirect Raman measurements prove this phenomenon. To date, no direct measurement of the thermal nonequilibrium between optical and acoustic phonons has been reported. Here, this physical phenomenon is directly characterized for the first time through a novel approach combining both electrothermal and optothermal techniques. While the optical phonon temperature is determined from Raman wavenumber, the acoustic phonon temperature is precisely determined using high‐precision thermal conductivity and laser power absorption that are measured with negligible nonequilibrium among energy carriers. For graphene paper, the energy coupling factor between in‐plane optical and overall acoustic phonons is found at (1.59–3.10) × 1015 W m−3 K−1, agreeing well with the quantum mechanical modeling result of 4.1 × 1015 W m−3 K−1. Under ≈1 µm diameter laser heating, the optical phonon temperature rise is over 80% higher than that of the acoustic phonons. This observation points out the importance of subtracting optical–acoustic phonon thermal nonequilibrium in Raman‐based thermal characterization.

The flexible electrodes are the crucial components for fabricating wearable supercapacitors. In this study, we present a quick and convenient method to prepare graphene paper (GP) as a flexible current collector on a large scale by an easy one‐step method. The composite electrode integrated with GP and MnO2 as a flexible supercapacitor was obtained by an electrochemical deposition method without using binder or conductive agent. The substrate (GP) of electrode not only provides mechanical strength, but also contributes energy storage capacity. The MnO2 nanoparticles deposited on the surface of GP further improved the electrochemical performance of composite. The neat GP can give a specific capacitance of 184 F/g at a current density of 1 A/g. At a current density of 1 A/g, the specific capacitance of the GP/MnO2 composite with a deposition time of 30 s is as high as 410 F/g. The method presented here shows great potential for the development of flexible electrode materials in practical energy storage devices. [ABSTRACT FROM AUTHOR]

Raman spectroscopy has been widely used to measure thermophysical properties of 2D materials. The local intense photon heating induces strong thermal nonequilibrium between optical and acoustic phonons. Both first principle calculations and recent indirect Raman measurements prove this phenomenon. To date, no direct measurement of the thermal nonequilibrium between optical and acoustic phonons has been reported. Here, this physical phenomenon is directly characterized for the first time through a novel approach combining both electrothermal and optothermal techniques. While the optical phonon temperature is determined from Raman wavenumber, the acoustic phonon temperature is precisely determined using high‐precision thermal conductivity and laser power absorption that are measured with negligible nonequilibrium among energy carriers. For graphene paper, the energy coupling factor between in‐plane optical and overall acoustic phonons is found at (1.59–3.10) × 1015 W m−3 K−1, agreeing well with the quantum mechanical modeling result of 4.1 × 1015 W m−3 K−1. Under ≈1 µm diameter laser heating, the optical phonon temperature rise is over 80% higher than that of the acoustic phonons. This observation points out the importance of subtracting optical–acoustic phonon thermal nonequilibrium in Raman‐based thermal characterization. [ABSTRACT FROM AUTHOR]

We report for the first time a one-step fabrication by lamination of inexpensive graphene paper (GP) based Ag/AgCl pseudo-reference (RE) and K+-selective coated-film electrodes forming the novelty of this work. Contrary to our previous work about laminated GP solid-contact electrodes, the electrode fabrication in this work does not require manual drop casting steps after the lamination, simplifying the fabrication and making it suitable for mass production. We also eliminated the need of the solid contact and simplified the electrode construction by placing the plasticized potassium-selective PVC membrane (ISM) directly on the GP functioning as combined electrode substrate and ion-to-electron transducer. Both Ag/AgCl and the ISMs were pre-deposited on rectangular GP sheets (10 ×100 mm2) before placing them inside laminating pouches and feeding them through an office laminator after which the electrodes were ready for use. Five batches of 32 pseudo-REs had a very good E 0 reproducibility of ± 2.8 mV. The K+-electrodes had a slope and detection limit of 57.4 ± 0.3 mV/pK (n = 4) and 6 × 10−7 M, and the E 0 reproducibility was in the best case only ± 1.2 mV matching the performance of non-laminated K+-electrodes. This work demonstrates that the ISMs are compatible with the lamination where the temperature can momentarily rise to ca. 130 °C. [Display omitted] • Hot lamination of planar and flexible graphene paper based pseudo-REs and ISEs. • One-step fabrication by lamination of low-cost electrodes that are suitable for mass production. • The Ag/AgCl pseudo-REs had a good batch-to-batch E 0 reproducibility of ± 2.8 (n = 32). • The K+-ionophore valinomycin does not degrade during hot lamination at ca. 130 °C. • Laminated K+-selective electrodes match the performance of non-laminated ones. [ABSTRACT FROM AUTHOR]

Abstract Flexible thin-film solar cells with high weight-specific power density are highly desired in the emerging portable/wearable electronic devices, solar-powered vehicles, etc. The conventional flexible metallic or plastic substrates are encountered either overweight or thermal and mechanical mismatch with deposited films. In this work, we proposed a novel substrate for flexible solar cells based on graphene paper, which possesses the advantages of being lightweight and having a high-temperature tolerance and high mechanical flexibility. Thin-film amorphous silicon (a-Si:H) solar cells were constructed on such graphene paper, whose power density is 4.5 times higher than that on plastic polyimide substrates. In addition, the a-Si:H solar cells present notable flexibility whose power conversion efficiencies show little degradation when the solar cells are bent to a radius as small as 14 mm for more than 100 times. The application of this unique flexible substrate can be extended to CuInGaSe and CdTe solar cells and other thin-film devices requiring high-temperature processing.

With the rapid development of electronic technology, the demand for thermal management materials is increasing continuously. Recent years graphene paper is considered as a potential material to replace the traditional graphitized polyimide film. Although the current route to graphene paper can achieve a high thermal conductivity, the extremely high energy consumption in graphitization procedure and severe heavy metal contamination limit the application of graphene paper. Here we develop a high-efficiency, low-energy cost, and inexpensive technology to produce graphene paper in large quantities. Without graphitization, the thermal conductivity of this graphene laminated film can reach 975 W m−1 K−1 when the thickness of film is 65 μm. Based on this easy-operated technology, we have already completed the pilot plant test, attained capacity of 3 kg graphene per reactor in 8 h and 800 mm × 100 m of graphene film each roll which was continuously and macroscopically assembled on our self-made equipment. Image 1 [ABSTRACT FROM AUTHOR]

In this study, free-standing MnO2 coated reduced graphene oxide (MnO2/rGO) paper with high flexibility and durability was prepared. As-prepared MnO2/rGO paper was characterized by scanning electron microscopy-energy-dispersive Xray spectroscopy (SEM-EDS), X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The electrochemical behavior of dopamine (DA) was investigated on flexible MnO2/rGO paper with cyclic voltammetry and amperometry methods. Electrochemical results have shown that the flexible MnO2/rGO paper electrode exhibits excellent electrocatalytic activity to DA due to its high specific surface area. In addition, the obtained flexible electrochemical sensor showed a wide linear range, a low detection limit and a very sensitive response for the amperometric determination of DA. [ABSTRACT FROM AUTHOR]

Although Al-ion battery is attracting researchers' attention worldwide, its volumetric energy density was not so promising due to low density of graphite-based positive electrodes in the current published literatures. Thus, defect-free yet densely packed graphene electrodes with high electronic conductivity and fast ionic diffusion are crucial to the realization of compacted Al-ion batteries with high volumetric energy density. In the present work, a self-supported and defect-free graphene-positive electrode (RHG-P-2850) was successfully produced by a hydriodic acid reduction of the graphene oxide (GO) method, followed by an ultrahigh temperature (2850 °C) annealing treatment. The density of the RHG-P-2850 (0.32 g cm−3) is currently the highest positive electrode material in the preparation of graphene-positive electrodes from GO. RHG-P-2850 positive electrode enables to deliver considerably high specific capacity 27.1 mAh cm−3 (85 mAh g−1) at the current density 2 A g−1. More importantly, a remarkably stable performance was achieved with 20% fading over 8000 cycles. The results enlighten and promote the design and preparation of densely packed graphene-positive electrode to develop high-performance Al/graphene battery. [ABSTRACT FROM AUTHOR]

A flexible composite paper Fe−Cu‐based metal‐organic framework (MOF)/reduced graphene oxide (rGO) (Fe−CuMOF/rGO) electrode was prepared by using a simple electrochemical method for the simultaneous detection of catechol (CC) and resorcinol (RC). Free‐standing, flexible and double‐sided Fe−CuMOF/rGO composite paper was obtained by applying the electrochemical deposition process on the rGO paper electrode in the solution containing Fe−CuMOF composite. The morphological analysis of Fe−CuMOF/rGO composite paper showed that sea urchin‐like structures formed on the rGO electrode surface consist of numerous sharp‐edged nanorods of Fe−CuMOF. Flexible Fe−CuMOF/rGO paper electrode exhibited high sensitivity, wide linear range and low detection limit for the simultaneous determination of CC and RC. The linear ranges of concentration for CC and RC were 0.1–800 and 0.1–720 μM, respectively, and the corresponding limits of detection (S/N=3) were 0.016 and 0.020 μM. The outstanding performance of this flexible electrode could be attributed to the sharp‐edged urchin‐like Fe−CuMOF structures which provide an increment of the surface area and the electrochemical activity of the composite paper electrode. Stability tests showed that Fe−CuMOF/rGO composite paper electrode has excellent flexibility, high durability, and good reproducibility. Furthermore, this electrode exhibited high sensitivity and selectivity for the determination of CC and RC in real sample analysis. [ABSTRACT FROM AUTHOR]

Given the thermal management problem aroused by increasing power densities of electronic components in the system, graphene-based papers have raised considerable interest for applications as thermal interface materials (TIMs) to solve interfacial heat transfer issues. Significant research efforts have focused on enhancing the through-plane thermal conductivity of graphene paper; however, for practical thermal management applications, reducing the thermal contact resistance between graphene paper and the mating surface is also a challenge to be addressed. Here, a strategy aimed at reducing the thermal contact resistance between graphene paper and the mating surface to realize enhanced heat dissipation was demonstrated. For this, graphene paper was decorated with polydopamine EGaIn nanocapsules using a facile dip-coating process. In practical TIM application, there was a decrease in the thermal contact resistance between the TIMs and mating surface after decoration (from 46 to 15 K mm2 W−1), which enabled the decorated paper to realize a 26% enhancement of cooling efficiency compared with the case without decoration. This demonstrated that this method is a promising route to enhance the heat dissipation capacity of graphene-based TIMs for practical electronic cooling applications.

The emergence of graphene paper comprising well-stacked graphene flakes has promoted the application of graphene-based materials in diverse fields such as energy storage devices, membrane desalination, and actuators. The fundamental properties of graphene paper such as mechanical, electrical, and thermal properties are critical to the design and fabrication of paper-based devices. In this study, the interlayer interactions in graphene paper were investigated by double cantilever beam (DCB) fracture tests. Graphene papers fabricated by flow-directed stacking of electrochemically exfoliated few-layer graphene flakes were mechanically separated into two parts, which generated force-displacement responses of the DCB sample. The analysis based on fracture mechanics revealed that the interlayer separation energy of the graphene paper was 9.83 ± 0.06 J/m2. The results provided a fundamental understanding of the interfacial properties of graphene papers, which will be useful for developing paper-based devices with mechanical integrity.

In this study, graphene oxide paper is obtained via vacuum‐assisted filtration of graphene oxide solution to prepare self‐standing electrodes for supercapacitors. Simultaneous reduction and N‐doping of graphene oxide paper are performed by chemical reduction followed by thermal annealing. Influence of different reduction techniques on the electrochemical properties of the self‐standing papers is investigated. N‐doped reduced graphene oxide papers are decorated with iron oxide nanoparticles to increase the energy density of the material. Increasing the amount of iron oxide nanoparticles in the composite paper results in enhanced capacitance. In the galvanostatic charge‐discharge measurements, iron oxide/N‐doped reduced graphene oxide electrode exhibits specific capacitance of 203 F g−1 at 0.5 mA cm−2. This value is remarkable since the electrode has a high mass loading of 2 mg cm−2, which shows that the electrode can be used for practical purposes. Moreover, these electrodes operate in a wide potential window (1.6 V) and exhibit 79 % capacitance retention at 10000 cycles. [ABSTRACT FROM AUTHOR]

Great attention has been drawn to flexible and portable electronic devices, so it is important to develop flexible energy-storage devices. In this study, the porous Ni-Co-N nanosheets on flexible graphene paper (GP) are prepared by surface nitridation of NiCo 2 O 4 nanosheets. Compared with NiCo 2 O 4 /GP, Ni 3 N/GP and CoN/GP, Ni-Co-N/GP shows superior performance in terms of specific capacitance of 960 F/g (48.1 mF/cm2) at 4 A/g, rate performance (86% capacitance retention) and cycle life (the capacitance retention reaches 95% over 5000 cycles). The paper-based all-solid-state asymmetric supercapacitors (SCs) are manufactured based on Ni-Co-N/GP and chemical oxidized GP (graphene oxide paper, GOP), which exhibits excellent bendability, flexibility, editability. The flexible energy device shows an outstanding specific energy of 4.78 mWh/cm3 and excellent cycle life (89% capacitance retention after 8000 cycles). Image 1 • The results demonstrate that the Ni-Co-N/GP shows superior performance than NiCo 2 O 4 /GP, Ni 3 N/GP and CoN/GP. • The Ni-Co-N/GP||GOP had high volumetric energy density of 4.78 mWh/cm3 and excellent cycle life. • The assembled energy device exhibits excellent bendability, flexibility, editability. [ABSTRACT FROM AUTHOR]

The flexible, free‐standing and durable highly rough nickel metal‐organic framework/reduced graphene oxide (NiMOF/rGO) composite paper electrode was prepared with a simple electrochemical deposition of NiMOF structures on the surface of the rGO paper electrode. NiMOF/rGO composite paper electrode was characterized by using scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), X‐ray diffraction (XRD), Raman spectroscopy and electrochemical impedance spectroscopy (EIS) techniques. As‐prepared NiMOF/rGO composite paper was used in the electrochemical detection of catechol (CC). The rough and flower‐like three‐dimensional (3D) NiMOF nanostructures on the rGO paper electrode surface greatly increased the catalytic performance of the paper electrode by providing a large active surface area. CC was detected on NiMOF/rGO composite paper in a very wide linear range from 0.02 to 760 μM, a low detection limit of 1.8 nM (S/N=3), with a high sensitivity of 0.158 mA μM cm−2 and very high selectivity, especially in the presence of phenol‐derived materials. Furthermore, it was determined that NiMOF/rGO composite paper also had high stability, flexibility, and durability, which may enable this material to be used in‐vivo applications. [ABSTRACT FROM AUTHOR]

A graphene paper-based flexible solid-contact ion-selective electrode (SC-ISE) was developed to detect lead ion sensitively. Graphene paper obtained via a simple vacuum filtration method was used as the electrode substrate for direct coating of an ion-selective membrane. The Nernstian slope of the prepared paper-based potentiometric sensor toward lead ion detection was demonstrated as 29.4 mV per decade. A detection limit as low as 2.5 x 10-7 mol L-1 was achieved. Reversed chronopotentiometry and water layer test revealed that the graphene paper-based SC-ISE possessed excellent potential stability because of the hydrophobicity of graphene paper. Furthermore, reliable data were obtained from the detection of lead ion levels in real water samples using the graphene paper-based potentiometric sensor, which shows great potential in practical application. [ABSTRACT FROM AUTHOR]

Abstract Graphene paper is a promising electrode material for use in flexible supercapacitors due to its good electronic conductivity and excellent mechanical characteristics. However, layers of graphene paper have a strong tendency to restack, resulting in a seriously reduced specific surface area and limited electrochemical performance. In this paper, restacked layers of graphene paper are reopened by a vacuum-assisted method, and carbon nanotubes (CNTs) are directly deposited on the enlarged space between the opened graphene layers. Consequently, an ordered carbon composite structure with alternately arranged graphene sheets and CNTs is constructed and exhibits increased specific surface area and a 3D conductive network. The structure and morphology of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy and N 2 adsorption/desorption measurements. The electrochemical performance was tested by galvanostatic charge-discharge test (GDC), electrochemical impedance spectroscopy (EIS) and cyclic voltammograms (CV). The obtained graphene/CNT paper exhibits a remarkably improved capacity of 170.8 F g−1, which is nearly two times higher than that obtained for a regular graphene paper. Highlights • A unique carbonaceous structure with CNTs depositing between the opened layers of graphene is established. • The reopening of the graphene layers can enlarge the layer distance and increase the SSA. • The deposited CNTs can further inhibit the restacking of graphene layers and form a 3D conductive framework. • The prepared MGCP exhibits significantly enhanced electrochemical performance. [ABSTRACT FROM AUTHOR]

Abstract Flexible sensing devices have drawn tremendous attention in the past decades due to their potential applications in future hand-held, potable consumer, and wearable electronics. Here, we firstly developed an ultrasensitive wireless potentiometric aptasensor based on flexible freestanding graphene paper for kanamycin detection. Flexible graphene paper made from a simple vacuum filtration method was used as a biocompatible platform for effective immobilization of aptamer. A nuclease-assisted amplification strategy was introduced into this potentiometric biosensing system in order to significantly improve the detection sensitivity through a classic catalytic recycling reaction of target induced by the nuclease (DNase I). As expected, an ultra-low detection limit of 30.0 fg/mL for kanamycin was achieved. Furthermore, the developed potentiometric enzymatic aptasensor exhibits high selectivity, favorable flexibility, excellent stability and reproducibility, which holds great promising for its routine sensing application. Highlights • Freestanding graphene paper as a flexible, biocompatible platform for aptasensors. • A nuclease-based amplification strategy was introduced into potentiometric sensors. • Smartphone was used to realize the wireless potentiometric detection of kanamycin. • Ultrasensitive detection of kanamycin with a detection limit of 30.0 fg/mL. • Excellent flexibility, high selectivity as well as simple design and fabrication. [ABSTRACT FROM AUTHOR]

A major disadvantage of polymer-based composite materials is their poor performance when exposed to relatively high heat flux. At temperatures typically above 300–400 °C, the organic matrix decomposes releasing heat, smoke, and toxic volatiles, jeopardising the composite mechanical performances. The heat flux resistance of composites can be improved by integrating protective coatings on their surface. In the present work, graphene nanoplatelet (GNP) films are employed as thermal barrier coatings (TBCs) to mitigate the thermal degradation of Carbon Fibres Reinforced Plastic (CFRP). The films were bonded onto the heat-exposed surface of CFRP laminates. Laser spot heating tests, with different laser power densities (25–150 kW/m2), were adopted to assess the effectiveness of the coating. The effect of the thickness of the protective layer has been tested too, by changing the number of layers (from 1 to 2 layers). From the results, a significant reduction in the temperatures and damages were observed. Moreover, the damage extension and residual mechanical performances of exposed samples have been assessed as a function of the power density and the protection level. A significant improvement of the post-heat flexural moduli and a significant reduction of the damaged areas have been obtained in laminates protected with high-loaded graphene nanoplatelet films. [ABSTRACT FROM AUTHOR]

There is a huge demand for rapid, reliable and low-cost methods for the analysis of heavy metals in drinking water, particularly in the range of sub-part per billion (ppb). In the present work, we describe the preparation, characterization and analytical performance of the disposable sensor to be employed in Square Wave Anodic Stripping Voltammetry (SWASV) for ultra-trace simultaneous determination of cadmium and lead. The electrode consists of graphene paper-perfluorosulfonic ionomer-bismuth nano-composite material. The electrode preparation implies a key step aimed to enhance the Bi3+ adsorption into nafion film, prior to the bismuth electro-deposition. Finely dispersed bismuth nanoparticles embedded in the ionomer film are obtained. The electrode was characterized by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), Atomic Force Microscopy (AFM), X-ray Photoelectron Spectroscopy (XPS) and Electrochemical Impedance Spectroscopy (EIS). The electrode shows a linear response in the 5–100 ppb range, a time-stability tested up to almost three months, and detection limits up to 0.1 ppb for both Pb2+ and Cd2+. The electrode preparation method is simple and low in cost and the obtained analytical performance is very competitive with the state of art for the SWASV determination of Pb2+ and Cd2+ in solution.

The graphene paper microsieves can be applied in the filtration of biological fluids or separation of solid particles from exploitation fluids. To produce graphene paper microsieves for specific applications, good control over fabrication should be achieved. In this study, a laser ablation method using a picosecond laser was applied to fabricate graphene paper microsieves. Holes in the microsieves were drilled using pulsed laser radiation with a pulse energy from 5 to 100 µJ, a duration of 60 ps, a wavelength of 355 nm, and a repetition rate of 1 kHz. The impact method was applied using 10 to 100 pulses to drill one hole. To produce holes of a proper diameter which could separate biological particles of a certain size (≥10 µm), optimum parameters of graphene paper laser ablation were defined using the MATLAB software taking into account laser pulse energy, repetition rate, and a desired hole diameter. A series of structural tests were carried out to determine the quality of an edge and a hole shape. Experimental results and Laguerre–Gauss calculations in MATLAB were then compared to perform the analysis of the distribution of diffraction fringes. Optimum experimental parameters were determined for which good susceptibility of the graphene paper to laser processing was observed.

A free-standing, highly flexible and conductive graphene paper (GrP) was fabricated via a simple, green, and inexpensive method. The fabrication process starts with electrochemical exfoliation of graphite as partially oxidized graphene suspension, which is then vacuum-filtered and air-dried. The procedure does not warrant any binders, toxic and corrosive agents, or high temperature. The mechanically stable GrP has excellent tensile strength of 52.3 ± 2.3 MPa at peak elongation of 5.1 ± 0.4%; ultralow sheet resistance of 2.2 Ω sq −1 , which is highly stable changing by only ∼4% even after 1000 consecutive bending cycles at 10 mm bending radius; and high electrical conductivity of 3.85 × 10 5  S m −1 . The GrP also possesses high specific capacitance of 195.8 F g −1 at 1 mV s −1 in 1 M H 2 SO 4 as electrolyte at room temperature with Pt wire and Ag/AgCl as counter and reference electrodes, respectively. Moreover, the GrP can reusably absorb large amounts of oils and organic solvents. This environmentally friendly GrP fabrication method is of low cost and can be used for large-scale fabrication for applications such as energy-storage devices, flexible/wearable electronics, and removal of oil or toxic organic spills. [ABSTRACT FROM AUTHOR]

Pt-based bimetallic alloys have attracted intensive interests as highly efficient and stable heterogeneous catalysts for fuel cell applications, and searching flexible free-standing nanomembranes has been on the research focus because of their promising applications in catalysis, nanoelectronics, batteries, and sensing. Herein, a flexible free-standing paper composed of FePt alloy nanoparticles on nitrogen-doped paper (FePt-NG paper) has been developed as integrated electrode towards electrocatalytic oxidation of formic acid. It is found that, N doping is beneficial for the well dispersion of FePt nanoparticles on NG paper. The synergistic effect between Fe and Pt, as well as N doping effect simultaneously assures the improved catalytic activity of FePt-NG paper, making it the promising flexible electrode for application in fuel cell system. Moreover, the synthesis strategy could be used for the construction of other free-standing electrode towards catalysis, sensing, and battery applications. Graphical Abstract: [ABSTRACT FROM AUTHOR]

The development of Fe 2 O 3 with high conductivity and energy density is crucial for practical utilizations of supercapacitors. Here, we demonstrated the preparation of novel Fe 2 O 3 /graphene oxide paper (Fe 2 O 3 /GP) hybrid electrode for high density supercapacitors. Due to the characteristic features of large surface areas and fast electron transportation, the specific areal capacitance of the Fe 2 O 3 /GP was around 3.08 F cm −2 at the charge-discharge current density of 5 mA cm −2 , which is nearly 14 times of the Fe 2 O 3 /carbon paper (Fe 2 O 3 /CP, 0.22 F cm −2 ). More importantly, the Fe 2 O 3 /GP hybrid electrode also retained about 95% of the initial capacitance after long-term cyclic process. These findings would help us to develop high effective and stable materials for energy storage devices. [ABSTRACT FROM AUTHOR]

Electrodes for non-enzymatic glucose sensing based on gold nanostructures onto graphene paper (GP-AuNPs) have been obtained inducing dewetting, by laser annealing, of 8 nm-thick Au layer deposited by sputtering. Molten-phase dewetting of gold layer, which produces the formation of spherical nanoparticles (AuNPs), was achieved by nanosecond laser annealing using a pulsed (12 ns) Nd: yttrium aluminum garnet YAG laser operating at 532 nm. The Surface of the electrode presents gold rich regions consisting of graphene nanoplatelets covered by spherical AuNPs. The sizes of AuNPs are in the range of 10–150 nm. Glucose was detected at a potential of 0.17 V vs SCE, which corresponds to the intense peak of two electrons oxidation. Highest sensitivity of 600 µA mM−1 cm−2 of glucose detection was obtained. The resulting sensitivity, detection limit and linear range of glucose detection are very promising since comparable to the actual state of art results for nanostructured gold electrodes which are, however, produced by complex multi-steps processes.

Herein we reported a novel routine to easily access graphene/polyaniline paper (GPp) as supercapacitor electrodes through controlled in-situ polymerization followed by roll coating. According to this routine, the load fraction of PANI can be easily controlled by feed ratio of aniline to GO. In the resulting GPp, PANI nanoarrays anchored graphene nanosheets and PANI nanofibers throughout the bulk coexist, and the former construct a three-dimensional network. As a result, the GPp as a freestanding electrode exhibits excellent electrochemical properties. It can deliver a high capacitance up to 838 F/g at a current density of 1 A/g, while keeps high retention of 93.7% at 10 A/g over 5000 cycles. Kinetics analysis shows that the GPp stores both surface capacitance and diffusion capacitance, but the former dominates the latter. [ABSTRACT FROM AUTHOR]

For practical applications of graphene-based materials in flexible supercapacitors, a technological breakthrough is currently required to fabricate high-performance graphene paper by a facile method. Herein, highly conductive (∼6900 S m −1 ) graphene paper with loose multilayered structure is produced by a high-efficiency in-situ chemical reduction process, which assembles graphite oxide suspensions into film and simultaneously conducts chemical reduction. Graphene papers with different parameters (including different types and doses of reductants, different thicknesses and areas of films) are successfully fabricated through this in-situ chemical reduction method. Meanwhile, the influences of the graphene papers with different parameters upon the supercapacitor performance are systematically investigated. Flexible supercapacitor based on the graphene paper exhibits high areal capacitance (152.4 mF cm −2 at current density of 2.0 mA cm −2 in aqueous electrolyte), and excellent rate performance (88.7% retention at 8.0 mA cm −2 ). Furthermore, bracelet-shaped all-solid supercapacitor with fascinating cycling stability (96.6% retention after 10 000 cycles) and electrochemical stability (an almost negligible capacity loss under different bending states and 99.6% retention after 4000 bending cycles) is established by employing the graphene paper electrode material and polymer electrolyte. [ABSTRACT FROM AUTHOR]

An efficient synthetic route to scalable high-performance graphene paper (G-paper) with high conductivity and excellent mechanical and chemical stabilities has been demonstrated. This paper-like electrode material comprises a poly(vinyl butyral- co -vinyl alcohol- co -vinyl acetate) (P(VB- co -VA- co -VAc)) copolymer adhesion layer and water-dispersible graphene (WDG) active material. A highly conductive, ductile, and mechanically robust G-paper was obtained using the Meyer rod coating method. The P(VB- co -VA- co -VAc) copolymer played an important role in smoothing the G-paper surfaces, resulting in enhanced conductivity of the G-paper. Moreover, the copolymer enhanced the mechanical stability of the G-paper through its strong hydrogen bonding interactions with WDG sheets and cellulose molecules. The as-prepared G-paper coated with P(VB- co -VA- co -VAc) exhibited low sheet resistance (115 Ω/sq), high tensile strength (37.2 MPa), good bending stability, and excellent acid-base resistance. [ABSTRACT FROM AUTHOR]