Porous Graphene Film Research Articles

Self-supported electrochemical sensor based on uniform palladium nanoparticles functionalized porous graphene film for monitoring H2O2 released from living cells.

Graphene film has been considered a promising material for the construction of self-supported electrodes due to its favorable flexibility and high conductivity. However, the film fabricated from pristine graphene or conventional graphene sheet reduced graphene oxide processes limited electrocatalytic performance. Decorating active metal species or incorporating heteroatoms intothegraphene framework have been proved to be effective methods to enhance the electrocatalytic efficiency of graphene film-based self-supported electrodes. Herein, we present a freestanding electrode composed of uniform Pd nanoparticles decorating N,S co-doped porous graphene film (Pd/NSPGF) and explore its practical application in differentiating various human colon cell types by in situ tracking the amount of H2O2 secreted from live cells. Our findings reveal that, on the one hand, the NSPGF has abundant surface and inner pores, which promote active site exposure, and mass diffusion during electrochemical reactions; on the other hand, the substitutional doping ofthe graphene framework with heteroatoms (e.g., N or S) can tailor its electronic and chemical properties, and facilitate the uniform loading of high-density Pd nanoparticles. Moreover, the intrinsic activity of Pd/NSPGF is regulated by the interaction of Pd nanoparticles withtheNSPGF support. Taking the advantages of morphology and composition, the self-supported Pd/NSPGF electrode displays remarkable electrochemical performance with a wide linear range up to 2.0mM, low detection limit of 0.1μM (S/N = 3), high sensitivity of 665 µA cm-2mM-1, and good selectivity. When applied in real-time trackingofthe H2O2 released from normal human colon epithelial cells and human colorectal cancer cells, the Pd/NSPGF-based electrochemical sensing system can distinguish the cell types by testing the number of extracellular H2O2 molecules released per cell, which holds considerable potential for early detection and monitoring of disease-related clinical specimens.

Highly matched porous MXene anodes and graphene cathodes for high-performance aqueous asymmetric supercapacitors

Aqueous asymmetric supercapacitors (ASCs) provide promising prospects for electronic systems in the future that require high energy density, power density and cycling life, due to their advantages such as low cost, safe operation and environmental friendliness. However, developing well-matched anodes and cathodes with complementary potential windows and coordinated charge storage kinetics remains a significant challenge. Here, we constructed porous MXene- and graphene-based films with nitrogenous and phosphorous terminals as anodes and cathodes, respectively, alleviating the restacking of nanosheets, generating more electrochemical active sites and improving the electrolyte penetration. The assembled aqueous ASCs based on the porous MXene and graphene films could achieve an excellent energy density of 26.8 Wh kg−1 at 425 W kg−1, high rate performance, and remarkable cycling stability with 97.3 % retention after 20,000 cycles. This work demonstrates a novel concept to develop high-performance aqueous ASCs by surface engineering of two-dimensional porous electrodes with matched structural and electrochemical properties.

Advancing Molecular Sieving via Å-Scale Pore Tuning in Bottom-Up Graphene Synthesis.

Porous graphene films are attractive as a gas separation membrane given that the selective layer can be just one atom thick, allowing high-flux separation. A favorable aspect of porous graphene is that the pore size, essentially gaps created by lattice defects, can be tuned. While this has been demonstrated for postsynthetic, top-down pore etching in graphene, it does not exist in the more scalable, bottom-up synthesis of porous graphene. Inspired by the mechanism of precipitation-based synthesis of porous graphene over catalytic nickel foil, we herein conceive an extremely simple way to tune the pore size. This is implemented by increasing the cooling rate by over 100-fold from -1 °C min-1 to over -5 °C s-1. Rapid cooling restricts carbon diffusion, resulting in a higher availability of dissolved carbon for precipitation, as evidenced by quantitative carbon-diffusion simulation, measurement of carbon concentration as a function of nickel depth, and imaging of the graphene nanostructure. The resulting enhanced grain (inter)growth reduces the effective pore size which leads to an increase of the H2/CH4 separation factor from 6.2 up to 53.3.

High-performance flexible asymmetric supercapacitors based on Hy-NiCoS/CNTs composites on porous graphene films

This research focused on the synthesized NiCoS/CNT composites by a hydrothermal method using thiourea and then drop-cast on laser-induced graphene (LIG) with porous structures for an active electrode of flexible asymmetric supercapacitors. Surface topography, cross-sectional outline, chemical structure and properties, and electrical properties of LIG, NiCoS, and Hy-NiCoS materials were measured and analyzed. In the two-electrode device, the Hy-NiCoS electrode has a high areal capacitance of 817 mF/cm2 under 0.5 mA/cm2 current density and a low internal resistance of 5.19 Ω. Furthermore, the prepared flexible asymmetric supercapacitors (Hy-NiCoS/AC) demonstrated excellent energy density of 0.017 mWh/cm2, power density of 3.2 mW/cm2, and areal capacitance of 85 mF/cm2 under 0.5 mA/cm2 current density. When the bending angles were 0°, 45°, and 90°, the areal capacitances of the prepared flexible asymmetric supercapacitors were 77.7, 75.0, and 70.8 mF/cm2, respectively. There is no obvious capacitance decay even at a large bending angle of 90°, which means that the asymmetric supercapacitor has excellent flexibility and stability. Based on the flexible asymmetric supercapacitors with excellent electrochemical performance, the proposed supercapacitors can be widely used in wearable electronic devices and healthcare products.

Electrochemistry of chloramphenicol on laser-induced graphene electrodes and its voltammetric determination in honey.

Laser scribing is a promising technology for the rapid and large-scale production of low-cost electrochemical sensors from diverse substrates. Polyimide has been the most popular so far because of its low cost, flexibility and capability of generating high-quality porous graphene films, known as laser-induced graphene (LIG). Herein we report the electrochemistry of chloramphenicol (CAP) on LIG electrodes and its determination in honey samples. LIG electrodes were fabricated by the photothermal conversion of sp3 carbon within the polymeric matrix into sp2 carbon using a CO2 laser cutter. The LIG electrode associated with differential pulse voltammetry (DPV) showed good linearity (R2 > 0.99) in the range from 10 to 160 μmol L-1 with a limit of detection of 1.0 μmol L-1 and good precision (RSD < 5%) for the electrochemical reduction of CAP species. Detection was possible free from the interference of other antibiotics, such as amoxicillin, tetracycline, sulfanilamide, and sulfamethoxazole. Spiked honey samples were analyzed by the standard-addition method and recovery values between 86 and 109% were obtained, which confirmed the absence of sample matrix effects. Therefore, the proposed sensor is an alternative, feasible, low-cost, and powerful analytical tool for the determination of CAP in honey.

Enhancing supercapacitor performance through design optimization of laser-induced graphene and MWCNT coatings for flexible and portable energy storage

The field of supercapacitors consistently focuses on research and challenges to improve energy efficiency, capacitance, flexibility, and stability. Low-cost laser-induced graphene (LIG) offers a promising alternative to commercially available graphene for next-generation wearable and portable devices, thanks to its remarkable specific surface area, excellent mechanical flexibility, and exceptional electrical properties. We report on the development of LIG-based flexible supercapacitors with optimized geometries, which demonstrate high capacitance and energy density while maintaining flexibility and stability. Three-dimensional porous graphene films were synthesized, and devices with optimized parameters were fabricated and tested. One type of device utilized LIG, while two other types were fabricated on LIG by coating multi-walled carbon nanotubes (MWCNT) at varying concentrations. Characterization techniques, including scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), Raman spectroscopy, and voltammetry, were employed to analyze the fabricated devices. AFM analysis revealed a surface roughness of 2.03 µm for LIG due to laser treatment. SEM images displayed compact, dense, and porous surface morphology. XRD analysis confirmed the presence of graphene and graphene oxide, which was further supported by energy-dispersive X-ray spectroscopy (EDX) data. Raman spectroscopy indicated that the fabricated samples exhibited distinct D and G bands at 1362 cm–1 and 1579 cm–1, respectively. Cyclic voltammetry (CV) results showed that LIG's capacitance, power density, and energy density were 6.09 mF cm–2, 0.199 mW cm–2, and 3.38 µWh cm–2, respectively, at a current density of 0.2 mA cm–2. The LIG-MWCNT coated electrode exhibited a higher energy density of 6.05 µWh cm–2 and an areal-specific capacitance of 51.975 mF cm–2 compared to the LIG-based devices. The fabricated device has potential applications in smart electronics, nanorobotics, microelectromechanical systems (MEMS), and wearable and portable electronics.

High-orientation, defect-rich and porous graphene films for excellent electromagnetic shielding and thermal management

With the rapid development of portable electronics, the demand for flexible shielding and thermal management materials is increasing steadily. Herein, we reported a scalable flexible graphene film preapred following hydrogen iodide chemical reducing and graphitization thermal reducing. Benifitting from the coordinated reduction, the fabricated graphene film is equipped with varous characteristics of high orientation, rich defect and three-dimensional porosity. Then the graphene film deliver outstanding mechanical property and electrical conductivity (1.2 × 105 S m−1). Moreover, superior electromagnetic interference (EMI) and thermal conductivity are realized compared with the simplex thermal reduction. The EMI effectiveness can reach a high value of 70 dB when the thickness is only 35 μm, and the specific EMI effectiveness is 380 dB/g cm−3. And the relationship between the effectiveness and structure parameters (thickness and density) is uncovered. The thermal conductivity could be up to 864 W m−1 K−1. This research may not only provide a new avenue to the development of flexible shielding and thermal management materials, but also promote the application of graphene.

Atomic iron on porous graphene films for catalyzing the VO2+/VO2+ redox couple in vanadium redox flow batteries

The electrocatalytic activity of the electrode materials towards the vanadium redox couples is a major factor in determining the performance of vanadium redox flow batteries (VRFBs). Herein, we report the employment of iron single atoms supported on a monolithic porous graphene film (Fe1-PGF) as electrodes for catalyzing the VO2+/VO2+ redox couple. The high intrinsic catalytic activity of the atomic Fe sites, the superior surface hydrophilicity, along with the enhanced mass transfer efficiency and exposure of active sites benefited from the porous structure, endow the Fe1-PGF electrode with improved electrochemical performance compared to metal-free PGF counterpart and commercial graphite felt electrode. Consequently, the single-cell battery assembled with Fe1-PGF exhibits a high voltage efficiency (77.96%) and energy efficiency (70.27%) at the current density of 60 mA cm−2 as well as lower overpotential and higher rate capability compared to the control samples. This study demonstrates that single atom catalysts (SACs) are promising candidates for catalyzing the vanadium redox couples in VRFBs and motivates the exploration of SACs in other types of redox flow batteries.

Confined oriented growth of FeSe2 on a porous graphene film as a binder-free anode for high-rate lithium-ion batteries

The FeSe2 nanorod@porous graphene film prepared by vacuum filtration, annealing, and subsequent selenylation is developed as an anode for lithium ion batteries. These FeSe2 nanorods are formed via confined oriented growth of FeSe2 nanoparticles.

Biocompatible Parylene-C Laser-Induced Graphene Electrodes for Microsupercapacitor Applications.

Laser irradiation of polymeric materials has drawn great attention as a fast, simple, and cost-effective method for the formation of porous graphene films that can be subsequently fabricated into low-cost and flexible electronic and energy-storage devices. In this work, we report a systematic study of the formation of laser-induced graphene (LIG) with sheet resistances as low as 9.4 Ω/sq on parylene-C ultrathin membranes under a CO2 infrared laser. Raman analysis proved the formation of the multilayered graphenic material, with ID/IG and I2D/IG peak ratios of 0.42 and 0.65, respectively. As a proof of concept, parylene-C LIG was used as the electrode material for the fabrication of ultrathin, solid-state microsupercapacitors (MSCs) via a one-step, scalable, and cost-effective approach, aiming at future flexible and wearable applications. The produced LIG-MSC on parylene-C exhibited good electrochemical behavior, with a specific capacitance of 1.66 mF/cm2 and an excellent cycling stability of 96% after 10 000 cycles (0.5 mA/cm2). This work allows one to further extend the knowledge in LIG processes, widening the group of precursor materials as well as promoting future applications. Furthermore, it reinforces the potential of parylene-C as a key material for next-generation biocompatible and flexible electronic devices.

Honeycomb-patterned porous graphene film for electrochemical detection of dopamine

Development of simple, low-cost and facile electrochemical sensor for DA detection is of great significance for the study and treatment of several neurological and psychiatric disorders. Herein, an innovative integration of honeycomb-patterned ordered porous structure with conductive reduced graphene oxide (rGO) was realized through the convenient breath figure method, in which the self-assembly of nontoxic and inexpensive water droplets were involved. Graphene oxide (GO) can be transferred to organic phase by surfactant via a simple self-assembly process to acquire the GO/surfactant complex, which was used as the casting solution in the breath figure method, and thus the skeleton of the porous structure. After electrochemical reduction, honeycomb-patterned porous rGO film was obtained. The prepared rGO-based porous structure modified electrode exhibited a high sensitivity of 1.18 μA/μM and low detection limit of 0.12 μM to DA detection, which are 2.5 and 0.07 folds to corresponding flat films, and are also comparable or even exceeding several functionalized graphene, GO or rGO composites sensor. In addition, excellent anti-interference, reproducibility, repeatability, long-term stability and good accuracy for DA detection in real samples were shown. Importantly, the porous structure can be easily adjusted by changing the preparation conditions, thereby regulating or optimizing the electrochemical sensing performance.

Optimization of Nanofiber Wearable Heart Rate Sensor Module for Human Motion Detection.

In order to further improve the detection performance of the wearable heart rate sensor for human physiological and biochemical signals and body kinematics performance, the wearable heart rate sensor module was optimized by using nanofibers. Nanoparticle-doped graphene films were prepared by adding nanoparticles to a graphene oxide solution. The prepared film was placed in toluene, and the nanoparticles were removed to complete the preparation of a graphene film with a porous microstructure. The graphene film and the conductive film together formed a wearable heart rate sensor module. The strain response test of the porous graphene film wearable heart rate sensor module verifies the validity of the research in this paper. The resistance change of the wearable heart rate sensor module based on the PGF-2 film is 8 to 16 times higher than that of the RGO film, and the sensitivity is better, proving that the sensor module designed by this method shows significant application potential in human motion detection.

Boosting capacitive energy density of conjugated molecule modified porous graphene film as high-performance electrode materials

The increasing demand for the electronic market has put forward large requirements for electrochemical capacitors with high energy and power density. Herein, the 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) modified flame reduced graphene oxide (FRGO) film (N/FRGO) is fabricated by π−π noncovalent interactions, which has abundant wavy wrinkles and fluffy pores to improve the interfacial contact performance, thus achieving large efficient ions storage areas. And the combined NTCDA molecules provide large numbers of additional redox-active sites. The N/FRGO based symmetric supercapacitor (SSC) exhibits a high capacitance value of 246.4 F g−1 at 0.2 A g−1, excellent rate capability of 65.5% capacitance retention at the increased current density of 50 A g−1, and the outstanding cyclability of 90% capacitance retention after 40,000 cycles. Moreover, by combining Zn deposition/stripping battery behavior, the N/FRGO film can achieve a high specific capacity of 217.0 mAh g−1. The N/FRGO based zinc ion capacitor (ZIC) has the maximum energy and power density of 166.5 Wh kg−1 and 29.0 kW kg−1, and can realize the prominent capacity retention under different bending angles and 800 bending cycles. Therefore, the N/FRGO shows a promising application in high energy density capacitors.

Prussian blue-modified laser-induced graphene platforms for detection of hydrogen peroxide.

A laser-induced graphene (LIG) surface modified with Prussian blue (iron hexacyanoferrate) is demonstrated as a novel electrochemical sensing platform for the sensitive and selective detection of hydrogen peroxide. Electrochemical Prussian blue (PB) modification on porous graphene films engraved by infrared laser over flexible polyimide was accomplished. Scanning electron microscopy images combined with Raman spectra confirm the formation of porous graphene and homogenous electrodeposition of PB over this porous surface. Electrochemical impedance spectroscopy reveals a substantial decrease in the resistance to charge transfer values (from 395 to 31.4 Ω) after the PB insertion, which confirms the formation of a highly conductive PB-graphene composite. The synergistic properties of PB and porous graphene were investigated for the constant monitoring of hydrogen peroxide at 0.0V vs. Ag|AgCl|KCl(sat.), under high-flow injections (166 µL s-1) confirmingthe high stability of the modified surface and fast response within a wide linear range (from 1 to 200µmol L-1). Satisfactory detection limit (0.26µmol L-1) and selectivity verified by the analysis of complex samples confirmed the excellent sensing performance of this platform. We highlight that the outstanding sensing characteristics of the developedsensor were superior in comparison with other PB-based or LIG-based electrochemical sensors reported for hydrogen peroxide detection.

In situ self-assembly of three-dimensional porous graphene film on zinc fiber for solid-phase microextraction of polychlorinated biphenyls.

Three-dimensional porous graphene film (3DPGF) wasfabricated on Zn fiber for solid-phase microextraction(SPME) through in-situ self-assembly strategy at roomtemperature. Fast electron transfer due to ionization of zincinduces reduction of graphene oxide and thus leads to thelayer-by-layer interfacial deposition of graphene sheets,forming three-dimensional porous network morphology.The 3D interpenetrating porous structure could provide moreavailable adsorption site for the target molecules and alsoenhance mass transfer efficiency in the extraction process.Therefore, the obtained 3DPGF fiber exhibited excellent performancewhen applied in the SPME of preconcentrationand quantification of polychlorinated biphenyls (PCBs) inenvironment waters. The developed method showed a linearrange from 1.0 ng L-1 and 200 ng L-1 with an acceptablecorrelation (R2=0.990). The limit of detection (LOD) andlimit of quantification (LOQ) were found 0.03-0.2 ng L-1and 0.1-0.8 ng L-1, respectively. The proposed method wasapplied in real water samples analysis with the recoveriesranging from 63.1 to 111.3%. The present study expandedthe application of three-dimensional porous graphene materialsin sample preparation and revealed its potential inSPME application.

A facile and efficient nitrite electrochemical sensor based on N, O co-doped porous graphene film

Increasing food safety awareness in our daily life has called for the establishment of rapid toxic nitrite detection techniques. In this work, we reported on a facile, quick laser processing method for the preparation of N, O co-doped porous graphene, which was patterned using a computer-controlled system to directly engrave a commercial polyimide (PI) tape, and subsequently used as an electrode for electrochemical nitrite detection. The laser-induced graphene (LIG) was characterized using various physical methods, and the electrochemical performance of the LIG sensing electrode was investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and chronoamperometry (CA). The designed electrode exhibited outstanding sensing ability toward nitrite oxidation. The peak current of the DPV curve had a good linear relationship with analyte concentrations ranging from 5 to 450 μmol/L, and the limit of detection (LOD) was calculated to be 0.8 μmol/L (S/N = 3). None of the common cations and anions yielded a positive current response, demonstrating that the electrode showed superior selectivity for electrochemical nitrite recognition. Furthermore, we observed and elucidated the pH dependence of electrocatalytic activity, which was attributed to the synergy of the surface functional groups derived from N, O co -doped graphene. Owing to its fast response and anti-interference capacity, this new LIG electrode offers great potential as a nitrite electrochemical sensor for environmental applications.

3D Porous Graphene Films with Large‐Area In‐Plane Exterior Skins

AbstractConstruction of macroscopic 3D architectures of graphene is crucial to harness the advantageous properties of planar 2D graphene and to enable integration to many conventional and novel applications. Ideally, the 3D structure of graphene should be free of defects, covalently interconnected, and can be produced at large‐scale. Among various assembly techniques, fabrication using chemical vapor deposition (CVD) enables the production of high‐quality graphene where selection of template is the key that determines its consequent crystalline quality and structural morphology. Herein, a new method is presented to synthesize high‐quality porous graphene film by incorporating an in situ reduction–oxidation cycling treatment to generate micrometer‐sized pores on commercial Ni foil using an all‐CVD process route. Owing to the unique morphological features of the modified Ni template, the graphene film exhibits a holey surface with large‐area exterior skin coverage of &gt;94% and many interconnected ligaments within its porous interior. This extraordinary configuration gives rise to superior in‐plane electrical conductivity despite its low density. In comparison to state‐of‐the‐art materials for electromagnetic interference shielding, this porous graphene film is among the best performing materials with a specific shielding effectiveness of &gt;550 dB cm3 g−1 and absolute effectiveness of &gt;220 000 dB cm2 g−1.

Elastomeric Foldable and High-Temperature Endurance Porous Graphene Films with Superior Electromagnetic Interference Shielding Performance

Materials possessing multiple features of ultrathinness, flexibility and foldability, high-temperature resistance, and superb electromagnetic interference shielding performance are urgently needed for future portable and wearable electronics. Herein, highly flexible, robust, and porous graphene films (GFs) are controllably fabricated via a strategically combined chemical reduction with a rapid confined foaming approach. The spatially confined foaming at 500 °C in air endows the annealed GFs (AGFs) with integrated functionalities including a significantly improved surface smoothness, a lower sheet resistance, an elevated high-temperature endurance, a tailored hierarchical porous architecture, and elimination of iodine doping synchronous impurities. The resultant AGFs exhibit an excellent self-recovering elastic property, outstanding reliability during a large number of repetitive bending cycles, and remarkable flexibility and mechanical strength. More laudably, compared to the shielding effectiveness (SE) of GFs fabricated by individual HI reduction (28.63 dB) and thermal reduction (19.37 dB), the AGFs present a greatly improved SE up to a superior level of 48.37 dB due to the enhanced absorption of microwaves in the well-constructed highly conductive and hierarchical porous structure. Therefore, such thin AGFs possessing excellent flexibility and elasticity and high-temperature durability associated with superb shielding performance offer strong potential applications in the field of portable and wearable devices.

Facile preparation of graphene film and sandwiched flexible poly(arylene ether nitrile)/graphene composite films with high EMI shielding efficiency

From the industrial grade graphene nanosheet (GNS) powder, the flexible, ultra-thin and freestanding graphene films are prepared using ultrasonic-assisted dispersion and suction filtration. The sandwiched composites films are prepared by layer-by-layer assembly using poly(arylene ether nitrile) (PEN) as polymer matrix. The strong Π···Π interaction pulls the graphene sheets together in a face-to-face way and they assembly into flexible graphene films. High electromagnetic interference shielding effectiveness (EMI SE) is shown due to multiple internal reflection and absorption inside the porous graphene films. A 3 μm thick graphene film shows EMI SE over 20 dB, specific SE (SE/density/thickness, SSE/t) of 72967 dB·cm2/g and absorption ratio over 92%. Moreover, the highest EMI SE of 77 dB is reached by sandwiching 3-layers of graphene films with PEN, and the composites films exhibit high flexibility, high tensile strength over 40 MPa and glass transition temperature of 185 °C.

Electrically tunable optical filter based on tapered fiber coated with porous graphene film

A novel graphene-enabled electrically tunable optical filter (ETOF) was reported in this work with high voltage response, low power consumption, and wide working bandwidth. A fiber Bragg grating (FBG) was etched in a microfiber using a femtosecond laser, and porous graphene film was coated on the surface of a tapered fiber. Metal electrodes were fabricated using which a voltage was applied to the graphene film to heat the fiber. The wavelength shift of the ETOF has a linear relationship with the applied voltage. The devices illustrated good repeatability and the voltage sensitivity was calculated as 50.36 pm/V. A maximum voltage of 30 V was applied to the devices and a 1.62-nm wavelength shift was observed. The 3-dB bandwidth of the FBG was approximately 0.38 nm, which corresponds to a power consumption of 5.76 μW in the device. The rising and falling times of the device were measured as 44.2 and 26.7 ms, respectively.