Graphene-based Aerogels Research Articles

Microextraction by packed sorbent: Introducing a novel hybrid silica-based chitosan-graphene oxide biosorbent for the evaluation of pesticides and antibiotics in food matrices

This study introduces a novel silica-graphene oxide@chitosan (SiGO@CS) material as a packed biosorbent for microextraction by packed sorbent (MEPS), followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis of pesticides (atrazine and thiamethoxam) and antibiotics (ceftiofur and sulfonamide) in food samples. The graphene-based aerogel was modified with varying percentages of silica-graphene oxide/chitosan (w/w) and characterized to confirm successful chitosan incorporation. Optimization of the MEPS protocol, using 24–1 and 23 experimental designs, identified draw/eject and washing cycles as the most influential parameters for extraction efficiency. The SiGO@CS biosorbent with 80 % CS/SiGO (w/w) exhibited superior extraction efficiency compared to other ratios and commercial sorbents. The method demonstrated excellent linearity for all analytes (R² > 0.9900), with low limits of detection (LOD) and quantification (LOQ) ranging from 0.020 to 0.045 µg l-1 and 0.045 to 1.0 µg l-1 for pesticides, respectively, and 5 to 15 µg l-1 and 15 to 20 µg l-1 for antibiotics, respectively. Trueness values were within 82 % to 109 %. The method's green credentials were confirmed using AGREEprep and the Green Analytical Procedure Index (GAPI) approach, highlighting sorbent reusability (over 15 times) and rapid analytical throughput (5 min per sample) with low use of pre-treated sample extract volume (500 µL). The application to local corn, tomato, and milk samples confirmed the detection and quantification of thiamethoxam and atrazine at concentrations above the recommended ingestion per day for one sample of tomato and corn out of the three samples analyzed. Furthermore, using the novel SiGO@CS biosorbent in the MEPS protocol offers a green, high-performance analytical alternative to traditional sorbent phases, with the potential for evaluating trace levels of pesticides and antibiotics in food matrices.

Recent Progress of Three-Dimensional Graphene-Based Composites for Photocatalysis.

Converting solar energy into fuels/chemicals through photochemical approaches holds significant promise for addressing global energy demands. Currently, semiconductor photocatalysis combined with redox techniques has been intensively researched in pollutant degradation and secondary energy generation owing to its dual advantages of oxidizability and reducibility; however, challenges remain, particularly with improving conversion efficiency. Since graphene's initial introduction in 2004, three-dimensional (3D) graphene-based photocatalysts have garnered considerable attention due to their exceptional properties, such as their large specific surface area, abundant pore structure, diverse surface chemistry, adjustable band gap, and high electrical conductivity. Herein, this review provides an in-depth analysis of the commonly used photocatalysts based on 3D graphene, outlining their construction strategies and recent applications in photocatalytic degradation of organic pollutants, H2 evolution, and CO2 reduction. Additionally, the paper explores the multifaceted roles that 3D graphene plays in enhancing photocatalytic performance. By offering a comprehensive overview, we hope to highlight the potential of 3D graphene as an environmentally beneficial material and to inspire the development of more efficient, versatile graphene-based aerogel photocatalysts for future applications.

Graphene/carbon nanotube aerogels with ultralow filling ratio through perfect cross-linking interface for efficient microwave absorption

Utilizing high-efficiency electrostatic assembly and a scalable freeze-drying technique followed by carbonization, we have developed a series of unique, lightweight, hierarchically porous 1D+2D aerogels containing carbon nanotubes (CNTs) and reduced graphene oxide (rGO). By manipulating the interaction between CNTs and graphene oxide perjurer in cellulose nanofiber (CNF), CNTs can uniformly distribute along the graphene cell walls via an exceptional cross-linking interface in the resultant rGO/CNT aerogels. This arrangement enables abundant heterogeneous interfaces, endowing the aerogels with high conductivity and polarization loss capacity. Moreover, the 1D+2D microstructure of CNT/rGO and the hierarchical pore architecture of the aerogels facilitate multiple scattering, further enhancing their loss capacity toward electromagnetic wave absorption (EMW). Coupled with the optimized impedance matching derived from the adjustable dielectric properties, the aerogels exhibit outstanding EMW absorption with a filling ratio of merely 2 wt%. Specifically, a minimum reflection loss (RLmin) of −49.61 dB and an effective absorption bandwidth (EAB) of 4.16 GHz are achieved. With a filling ratio of 3 wt%, the RLmin reaches −77.51 dB, accompanied by an EAB of 3.84 GHz, surpassing the reported carbon or graphene-based aerogel EMW absorbers. In this work, the ultra-low filling ratio resulting from high conductivity confers a practical design for fabricating lightweight carbon-based aerogels suitable for high-efficiency EMW absorption, manifesting multiple applications in electromagnetic compatibility and aerospace contexts.

Graphene-based aerogel for efficient oil sorption and water pollution remediation

In the past few years, there has been a notable rise in the release of industrial waste oil, frequent oil spills at sea, and a significant escalation in the severity of water pollution. This issue has garnered global attention and is now recognised as a widespread concern. Hence, there is a pressing demand for an oil-absorbing material exhibiting high oil-absorption capabilities and robust mechanical properties. This study introduces a new aerogel characterised by a three-dimensional hierarchical pore size structure derived from natural corn stalk powder and graphene oxide (GO). The developed aerogel demonstrated notable sorption capacity ranging from 70.6 to 131.0 g/g, along with excellent compressibility and high elasticity. These properties enable effective oil-water separation and selective sorption. This study introduces a novel approach to treating agricultural waste and presents a straightforward, environmentally friendly, cost-effective method for synthesising high-performance graphene-based oil-absorbing agents.

Dual role of two-dimensional graphene in silica aerogel composite: Thermal resistance and heat node

Incorporating two-dimensional graphene sheets, known for their high in-plane thermal conductivity, into silica aerogel enhances both the thermal insulation and mechanical properties of the composite. This work delves into the impact of graphene doping on the solid thermal conductivity of silica composites and their mechanical characteristics, employing molecular dynamics simulations that encompass both amorphous silica bulk and porous silica aerogel structures. Our findings reveal that graphene–silica interface thermal resistance notably restricts heat conduction in graphene doped silica aerogel, with the most pronounced effect occurring when graphene aligns vertically with the heat flux. Within porous silica aerogel, graphene serves as a “heat node”, bridging and connecting adjacent pores. A notable “trade-off” emerges: high weight percentages of graphene sheets augment heat transfer through the “heat node effect”, whereas the interfacial thermal resistance between graphene and aerogel reduces solid heat transfer, leading to decreased thermal conductivity. Additionally, while the inclusion of graphene sheets offers limited mechanical property enhancements, their two-dimensional structure can cause detachment and slipping from the silica matrix, leading to localized improvements in mechanical strength. This work sets the stage for advancing graphene-based aerogel composites characterized by low thermal conductivity and enhanced mechanical properties.

Superelastic, ultralight aramid fibre/tannic acid/graphene nanohybrid aerogel constructed using a cross–scale strengthening strategy for rapid and high–flux oil–water separation

Graphene-based aerogels are efficient oil–water separation materials with enormous potential, but their poor mechanical strength and cycling stability limit their applications. A cross-scale strengthening strategy was used to construct aramid fibre (A)/tannic acid (T)/graphene (G) (ATG) aerogel using an in situ electrostatic self-assembly and freeze-drying process. At 95 % of the ultimate compressive strain, the ATG aerogel could withstand a stress of up to 147 kPa and can rebound quickly. The mechanism for the high mechanical strength of the ATG aerogel was explored by structure characterisation and density functional theory (DFT) calculation. A superhydrophobic aerogel (named H-ATG) was prepared by a hydrophobic modification of ATG using a vapor deposition reaction method. The H-ATG aerogel exhibited excellent superoleophilicity/superhydrophobicity with the oil and water contact angles of 0° and 152.48°, respectively. The hydrophobicity of the H-ATG aerogel was stable over the pH range of 1–13 and the temperature range of -80–600 °C. In addition, the aerogel had an ultra-fast absorption speed and excellent absorption capability, rapidly absorbing various oil-based organic solvents up to 101 times its own weight within 5 s. After the absorption of oil or solvents, it could be easily recovered by combustion, distillation or extrusion, and the performance remained relatively unchanged after 10 cycles. When H-ATG was used as a filter to achieve fast and efficient oil–water separation with a high flux of 20,371.83 L·h−1·g−1. Therefore, the H-ATG aerogel has excellent potential for applications in the oil–water separation and the purification of oily wastewater.

Flexible and Multifunctional Composites with Highly Strain Sensing and Impact Resistance Properties.

The development of smart protective clothing will help detect injuries from contact sports, traffic collisions, and other accidents. The combination of ecoflex, spacer fabric, and graphene-based aerogel provides a multifunctional composite. It shows a strain sensitivity of 17.71 at the strain range of 40~55%, a pressure sensitivity of 0.125 kPa-1 at the pressure range of 0~15 kPa, and a temperature sensitivity of -0.648 °C-1. After 50 impact tests, its protection coefficient only dropped from 60% to 55%. Additionally, it shows thermal insulation properties. The compression and impact process results of finite element numerical simulation analysis are in good agreement with the experimental results. The ecoflex/aerogel/spacer fabric sensor exhibits a simple structure, large pressure strain, high sensitivity, flexibility, and ease of fabrication, making it a candidate for smart protective clothing resistant to impact loads.

Robust Graphene-based Aerogel for Integrated 3D Asymmetric Supercapacitors with High Energy Density.

Three-dimensional asymmetric supercapacitors (3D ASC) have garnered significant attention due to their high operating window, theoretical energy density, and circularity. However, the practical application of 3D electrode materials is limited by brittleness and excessive dead volume. Therefore, we propose a controlled contraction strategy that regulates the pore structure of 3D electrode materials, eliminates dead volume in the 3D skeleton structure, and enhances mechanical strength. In this study to obtain reduced graphene oxide/manganese dioxide (rGO/MnO2) and reduced graphene oxide/carbon nanotube (rGO/CNT) composite aerogels with a stable and compact structure. MnO2 and CNT as nanogaskets, preventing the self-stacking of graphene nanosheets during the shrinkage process. Additionally, the high specific capacitor nanogaskets significantly enhance the specific energy density of the rGO aerogel electrode. The prepared rGO/MnO2//rGO/CNT 3D ASC exhibits a high mass-specific capacitance of 216.15 F g-1, a high mass energy density of 74 Wh kg-1 at 3.5 A g-1, and maintains a retention rate of capacitance at 99.89 % after undergoing 10,000 cycles of charge and discharge at 5 A g-1. The versatile and integrated assembly of 3D ASC units is achieved through the utilization of the robust mechanical structure of rGO-based aerogel electrodes, employing a mortise and tenon structural design.

Ultralight and strain-sensitive bacterial cellulose derived carbon fiber-reinforced graphene aerogel for broadband sound absorption

The growing severity of urban noise pollution poses a threat to the physical and mental health of residents, prompting the need for the development of effective sound-absorbing materials. Herein, we present a versatile method to fabricate ultralight and flexible graphene-based aerogels by introducing one-dimensional carbon fibers as reinforcements. These carbon nanofiber-reinforced graphene aerogels (CNF/GAs) were obtained by the carbonization of freeze-casted bacterial cellulose/graphene oxide (BC/GO). Our CNF/GAs possess a low apparent density (∼3.05 mg cm−3) and exhibit broad-band sound absorption performance with a superior noise reduction coefficient (NRC) as high as 0.65 at a thickness of 30 mm. Meanwhile, their excellent elasticity endows the CNF/GAs with strain-sensing capability, enhancing their capacity for detecting deformations when utilized as sound absorbers in engineering applications. Additionally, the highly porous structure makes the CNF/GAs excellent thermal insulators, with a thermal conductivity as low as 0.011 W m−1 K−1, further expanding their environmental reliability. Therefore, our approach develops CNF/GAs with excellent broad-band sound absorption performance and mechanical-environmental reliability, showing significant practical potential.

A controllable foaming approach for the fabrication of “rattan-like” graphene-based composite aerogel with desirable microwave absorption capacity

As a common environmental pollutant, microwave can cause great harms to human health. The development of high-performance microwave absorber with lightweight is indeed necessary. Herein, “rattan-like” graphene-based composite aerogels, having macroscopic pores surrounded by plenty of small pores, were designed and fabricated via an in-situ foaming then carbonized approach. Firstly, graphene oxide (GO), nanocellulose and ferrous ions were integrated into an aerogel with uniform large pores via a freeze-casting method. Then, the aerogel was immersed into a H2O2 solution, during which bubble clusters generated in situ. These bubbles were driven into the stacked GO sheets and formed small pores. With the increase of the H2O2 concentration from 0.5 to 10 wt%, the count percentage of the small pores in the aerogel increased from 81.5 to 95.2%. After the final carbonization, the graphene sheets were dually interconnected with magnetic nanoparticles and carbonized nanocellulose. The unique porous structure and dual-connected networks endowed the aerogel with enhanced conductive loss and optimized impedance matching capacity, and thus an excellent microwave absorption performance, whose maximum reflection loss achieves −68.5 dB. Further, the aerogel also exhibited superior sound absorption performance (noise reduction coefficient up to 0.91 in 1000–6300 Hz), and good mechanical stability.

High-Temperature Performance Evaluation of a Novel Graphene-Based Aerogel

High-Temperature Performance Evaluation of a Novel Graphene-Based Aerogel

Graphene-based aerogels in water and air treatment: A review

Graphene-based aerogels have attracted considerable interest in recent years for their ability to remove toxic pollutants, due to their attractive properties, which include a sufficient number of anchor positioning points, arbitrarily changing shapes, and adjustable functional groups and pore sizes. The potential methods for adsorption, degradation, and reduction of water and atmospheric pollutants using graphene-based aerogels have been thoroughly investigated. Firstly, this review introduced the current research on the application of graphene-based aerogels as environmentally efficient materials for removing water and atmospheric contaminants, including heavy metal ions, organic dyes, nitrogen oxides (NOx), and volatile organic compounds (VOCs). Secondly, the important role in promoting adsorption and catalysis and the types of modifications of graphene aerogels are discussed in depth. Finally, this review summarized the great potential of graphene-based aerogels as environmentally functional materials and put forward the challenges and prospects, aiming to promote the development and industrial application of graphene-based aerogels.

Progress in Research on the Preparation of Graphene-Based Aerogels Using γ-ray Irradiation Technology.

Graphene aerogels (GAs) are of significant interest in the scientific community due to their unique attributes, including a three-dimensional porous structure, exceptional specific surface area, and remarkable chemical stability. Researchers have made notable breakthroughs in aerogel preparation, focusing on aspects like porous structures and chemical stability. This review explores product morphologies and properties developed between 2011 and 2023, particularly examining applications of graphene aerogels with amine or alcohol radical scavengers. It offers a roadmap for researchers, suggesting possibilities for radiation-based preparation and indicating broader applications. These findings contribute to a deeper understanding of aerogels and expand the potential applications of graphene aerogels across various fields.

Constructing graphene-based aerogel with bi-continuous interpenetrating networks as a multi-functional microwave absorber

The design of three-dimensional networks in graphene-based aerogels is an effective strategy for fabricating a lightweight microwave absorber with strong absorption and broad effective bandwidth. Herein, a multi-functional aerogel with bi-continuous interpenetrating networks comprised of reduced graphene oxide (RGO) and cellulose nanofiber (CNF) was developed via an “ice-dissolving” (freezing and solvent exchange) and subsequent annealing strategy. Different from the conventional step-by-step construction of two independent networks, the bi-continuous interpenetrating networks were simultaneously built in a one-step freezing process. Notably, the network structure of the aerogel can be tuned by adjusting the concentration of CNF (CCNF) during the freezing stage. When the CCNF increased from 2 to 8 wt%, the network structure transitioned from a single three-dimensional RGO skeleton to ordered bi-continuous interpenetrating networks, and then to a disordered CNF/RGO mixed network. The mutual contributions from the RGO skeleton and CNF network endowed the aerogel (14.96 mg cm−3) with improved conduct loss and optimized characteristic impedance, leading to an excellent microwave absorption capacity. Consequently, the aerogel achieved a maximum reflection loss of −68.3 dB and an effective bandwidth of 6.9 GHz, respectively. Moreover, the unique network structure also enabled the sample to have superior noise absorbing performance (normalized absorption coefficient of 0.894 in 250–6300 Hz) and good structural stability. This strategy provides a facile avenue for constructing multi-functional aerogels with bi-continuous interpenetrating networks for both microwave absorption and noise absorption applications.

Synthesis of magnetic Fe3O4/graphene aerogel for the removal of 2,4-dichlorophenoxyacetic acid herbicide from water.

Graphene-based aerogels are among the lightest materials in the world and have been extensively studied for environmental remediation. In this work, an Fe3O4/graphene aerogel material was synthesized using the co-precipitation method. The prepared material was characterized using X-ray diffraction (XRD), scanning electron microscopy/X-ray energy dispersive spectroscopy (FESEM/EDX), infrared spectroscopy (FT-IR), and vibration sample magnetization (VSM). The results showed that the Fe3O4 nanoparticles with a particle size of less than 100 nm were well-distributed on the surface of the graphene aerogel. The prepared Fe3O4/graphene aerogel showed effective removal of 2,4-D herbicide from the aqueous solution with a maximal adsorption capacity of approximately 42.918 mg g-1. The adsorption isotherms and kinetics were investigated to study the adsorption behaviour of the resultant material. The saturation magnetism value of the aerogel was determined to be about 20.66 emu g-1, indicating that the adsorbent could be easily collected from the solution using an external magnet. These results implied that the prepared Fe3O4/graphene aerogel could be a promising adsorbent for the removal of 2,4-D herbicide from water.

Electrothermal Transformations within Graphene-Based Aerogels through High-Temperature Flash Joule Heating.

Flash Joule heating of highly porous graphene oxide (GO) aerogel monoliths to ultrahigh temperatures is exploited as a low carbon footprint technology to engineer functional aerogel materials. Aerogel Joule heating to up to 3000 K is demonstrated for the first time, with fast heating kinetics (∼300 K·min-1), enabling rapid and energy-efficient flash heating treatments. The wide applicability of ultrahigh-temperature flash Joule heating is exploited in a range of material fabrication challenges. Ultrahigh-temperature Joule heating is used for rapid graphitic annealing of hydrothermal GO aerogels at fast time scales (30-300 s) and substantially reduced energy costs. Flash aerogel heating to ultrahigh temperatures is exploited for the in situ synthesis of ultrafine nanoparticles (Pt, Cu, and MoO2) embedded within the hybrid aerogel structure. The shockwave heating approach enables high through-volume uniformity of the formed nanoparticles, while nanoparticle size can be readily tuned through controlling Joule-heating durations between 1 and 10 s. As such, the ultrahigh-temperature Joule-heating approach introduced here has important implications for a wide variety of applications for graphene-based aerogels, including 3D thermoelectric materials, extreme temperature sensors, and aerogel catalysts in flow (electro)chemistry.

Electromagnetic oscillation induced graphene-based aerogel microspheres with dual-chamber achieving high-performance broadband microwave absorption

Graphene-based aerogels have indeed generated significant interest in manufacturing microwave absorbers with ultra-low density and high efficiency. Nevertheless, unitary loss mechanism and impedance mismatch hinder corresponding application. Furthermore, it is essential to address the challenges related to structure control strategy and explanation of the loss mechanism. Dual-chamber graphene-based aerogel microspheres (AMs) with heterogeneous interfaces were fabricated through electrospinning-freeze drying and subsequent calcination. Significant differences are observed in reflecting and scattering of shell and dual-chamber structure against electromagnetic wave (EMW), enabling electromagnetic oscillation, sequential absorption and multi-level coupling of EMW. In addition, the dual-chamber construction is a pivotal role in optimizing impedance matching. In this regard, dual-chamber structure graphene-based AMs with 5 wt% loading were synthesized and exhibited excellent loss ability to EMW in the range of 5–18 GHz, which manifest −28.12 dB at 15.62 GHz, and accordingly, the fE is 6.0 GHz at 2.2 mm thickness, achieving full coverage dissipation of Ku-band. The results demonstrate that the dual-chamber graphene-based AMs achieve the effect of multi-frequency compatible and broadband microwave absorption at low thickness. The integration of the ideation of heterogeneous dual-chamber AMs with electromagnetic-oscillation and sequential loss provides a unique and innovative strategy for modulating lightweight and broadband efficiency absorbers.

Graphene-Based Aerogels for Biomedical Application.

Aerogels are three-dimensional solid networks with incredibly low densities, high porosity, and large specific surface areas. These aerogels have both nanoscale and macroscopic interior structures. Combined with graphene, the aerogels show improved mechanical strength, electrical conductivity, surface area, and adsorption capacity, making them ideal for various biomedical applications. The graphene aerogel has a high drug-loading capacity due to its large surface area, and the porous structure enables controlled drug release over time. The presence of graphene makes it a suitable material for wound dressings, blood coagulation, and bilirubin adsorption. Additionally, graphene's conductivity can help in the electrical stimulation of cells for improved tissue regeneration, and it is also appropriate for biosensors. In this review, we discuss the preparation and advantages of graphene-based aerogels in wound dressings, drug delivery systems, bone regeneration, and biosensors.

Influence of boron doping level and calcination temperature on hydrogen evolution reaction in acid medium of metal-free graphene aerogels

In this work, metal-free boron-doped graphene-based aerogels were successfully synthesized via a one-step autoclave assembly followed by freeze-drying and used as electrocatalysts for the hydrogen evolution reaction (HER) in acidic media. The synthesized reduced graphene oxide aerogels (rGOA) showed improved electrocatalytic activity by introducing boron and structural defects. The amount of boric acid used both as a dopant and reducing agent in the synthesis was optimized (boric acid/GO mass ratio = 17.5) to practically reach the crystallization limit of boric acid (boric acid/GO mass ratio = 20). It was observed that the higher the amount of boric acid added, the more boron was incorporated into the carbonaceous structure, improving the electrocatalytic activity of the final aerogel. Furthermore, calcination of the boron-doped electrocatalyst at 600 °C resulted in final aerogels with low oxygen content, moderate surface area, bimodal pore size distribution, and a high electrochemical active surface area. The final 3D graphene aerogel developed in this work, showed such outstanding electrocatalytic activity in HER as to replace noble metal-based electrocatalysts in the future.

Towards metal-free nitrogen-doped graphene aerogels as efficient electrocatalysts in hydrogen evolution reaction

Graphene-based materials have been researched to substitute traditional Pt-based electrocatalysts in the hydrogen evolution reaction (HER) due to its strong electrical conductivity, easy functionalization, and cheaper synthesis. Doping graphene with heteroatom is a simple way of obtaining original and active electrocatalysts. Moreover, the nitrogen on it had a positive effect on HER performance. By using a reducing agent with nitrogen while synthesising graphene-based aerogels nitrogen-doped catalysts were obtained. In addition, a better reduction rate, higher crystallography parameters and a more porous material structure were reached. The aerogels were synthesised in an one-pot hydrothermal process, in which the graphene sheets were assembled. This was followed by freeze-drying, which fixed the carbon matrix structure. As a result, the final aerogel had a 3D structure that eased mass transfer and enhanced catalytic activity, reaching an overpotential of −10 mAcm−2 at 101 mV vs RHE (η10 = 101 mV). The amount of quaternary type nitrogen generated during synthesis had a strong influence on electrocatalytic behaviour in HER. Then, quaternary nitrogen and surface area (up to 397 m2/g) were maximized to ensure a higher current density. Moreover, an effective aerogel was prepared with half the solvent per batch, as this was essential for expanding the synthesis to an industrial scale. A final calcination step resulted crucial to improve the metal-free aerogel HER performance.