Graphene-based Paper Research Articles

Laser fabrication of epidermal paper-based graphene sensors

There is an increasing demand for epidermal sensors that can adapt to the contours and the movements of the human body, but the fabrication of prevalent polymer-based epidermal sensors often involves costly materials and complex procedures. Paper has emerged as a cost-effective substrate for next-generation epidermal sensors, featuring such advantages as bendability, breathability, biocompatibility, and environment-friendliness. However, transducing materials are commonly introduced to paper substrates in post hoc manners or through time-consuming syntheses, in addition to the direct manufacturing of paper. Here we report an integrative method to fabricate epidermal paper-based graphene sensors, where graphene induction and paper cutting can be achieved in a single lasing procedure to generate both transducing components and overall sensor formats. Lasing conditions are systematically explored, mainly to control the multifaceted properties of the obtained graphene transducers. The resultant paper-based graphene structures exhibit sufficient reliability in various scenarios regarding storage, lighting, and deformation. Paper-based graphene sensors are strategically designed in terms of overall formats, geometric patterns, hydrophilicity/hydrophobicity, surface functionalization, and readouts for measuring biophysical and biochemical information relevant to human health. The sensor performance can be optimized by adjusting laser power, and the calibrated sensitivities for mechanical strain, temperature, humidity, pH, and glucose are 76.93, –0.15% °C–1, 37.06 μA %–1, 28.13 mV pH–1, and 1.26 μA mM–1, respectively. Multimodal health monitoring is demonstrated with paper-based graphene sensors. Our approach can facilitate the generation of epidermal paper-based sensors and meet diverse requirements of health monitoring.

Flexible and electrically robust graphene-based nanocomposite paper with hierarchical microstructures for multifunctional wearable devices

Multifunctional and flexible wearable devices play a crucial role in a wide range of applications, such as heath monitoring, intelligent skins, and human-machine interactions. Developing flexible and conductive materials for multifunctional wearable devices with low-cost and high efficiency methods are highly desirable. Here, a conductive graphene/microsphere/bamboo fiber (GMB) nanocomposite paper with hierarchical surface microstructures is successfully fabricated through a simple vacuum-assisted filtration followed by thermo-foaming process. The as-prepared microstructured GMB nanocomposite paper exhibits not only a high volume electrical conductivity of ∼45 ​S/m but also an excellent electrical stability (i.e., relative changes in resistance are less than 3% under stretching, folding, and compressing loadings) due to its unique structure features. With this microstructured nanocomposite paper as active sensing layer, microstructured pressure sensors with a high sensitivity (−4 ​kPa−1), a wide sensing range (0–5 ​kPa), and a rapid response time (about 140 ​ms) are realized. In addition, benefitting from the outstanding electrical stability and mechanical flexibility, the microstructured nanocomposite paper is further demonstrated as a low-voltage Joule heating device. The surface temperature of the microstructured nanocomposite paper rapidly reaches over 80 ​°C when applying a relatively low voltage of 7 ​V, indicating its potential in human thermotherapy and thermal management.

Graphene composite paper synergized with micro/nanocellulose-fiber and silk fibroin for flexible strain sensor

The fabrication of uniform and strong graphene-based conductive paper is challenging due to easy aggregation and poor film formability of graphene. Herein, on the basis of good dispersing effect of nanocellulose, high content graphene (50 wt%) composite paper with micro/nanocellulose fibers and silk fibroin (SF) was manufactured via simple casting method. The synergistic effects of cellulose microfibers (CMFs), cellulose nanofibers (CNFs) and SF result in the paper with ideal combination of flexibility, electrical conductivity and mechanical strength, where CNFs, CMFs and SF act as dispersing and film forming for GNPs, dimensional stability, and interfacial binding agents, respectively. Extraordinarily, by adding SF, graphene nanosheets are tightly coated on the surface of CMFs. The composite paper shows a tensile strength of 49.29 MPa, surface resistance of 39.0–42.1 Ω and good joints bend sensing performance. Additionally, it is found that CMFs can hinder the micro-cracks from propagating during the cyclic elbow bending test. The graphene-based conductive paper is helpful for the development of smart clothing wearable biosensing devices.

Reduced graphene oxide/MnFe2O4 nanocomposite papers for fast electrical heating and microwave absorption

Reduced graphene oxide (RGO) and magnetic metal oxide composite papers are high needed in microwave absorption, shielding and rapid electrical heating. Herein, a self-assembled multifunctional RGO/MnFe2O4 paper is effectively prepared by a simple method of solution casting and thermal reduction for electromagnetic shielding, microwave absorption, temperature-sensing, electrothermal de-icing. A fast electrical heating is achieved, a saturation temperature of 100.2 °C can be provided within 15 s at a constant current of 0.35 A. In addition, the composite paper under a thermal reduction temperature of 800 °C gives an electromagnetic shielding efficiency (SE) value of 29 dB at X-band and a reflection loss (RL) of 43.2 dB at 14.1 GHz with a thickness of 3 mm and an effective bandwidth (RL < −10 dB) from 10.5 to 16.2 GHz. More, the contact resistance between the graphene-based paper and electrode is decoupled based on the equivalent circuit model, which is greatly contribute to its higher electrothermal and other electrical performance. And the contact resistance is 19.18 Ω, which accounts for 15% of the total resistance of the RGO/MnFe2O4 composite. This RGO/MnFe2O4 paper can offer great potential for fast electrical heater, high performance microwave absorbing and shielding materials.

Directional growth of quasi-2D Cu2O monocrystals on rGO membranes in aqueous environments.

The preparation technology of unconventional low-dimensional Cu2O monocrystals, which exhibit specific crystal planes and present significantly unique interfacial and physicochemical properties, is attracting increasing attention and interest. Herein, by integrating a high-temperature oxidation process under vacuum and a pure-water incubation process under ambient conditions, we propose the self-assembled growth and synthesis of quasi-two-dimensional Cu2O monocrystals on reduced graphene oxide (rGO) membranes. The prepared Cu2O crystals have a single (110) crystal plane, regular rectangular morphology, and potentially well conductivity. Experimental and theoretical results suggest that this assembly is attributed to the pre-nucleation clusters aggregation and directional attachment of Cu and O on the rGO membranes in aqueous environment and cation-π interactions between the (110) crystal plane of Cu2O and rGO surface. Our findings offer a potential avenue for the discovery and design of advanced low-dimensional single-crystal materials with specific interfacial properties in a pure aqueous environment.

Self-healable recyclable thermoplastic polyurethane elastomers: Enabled by metal–ligand bonds between the cerium(III) triflate and phloretin

This study initially developed highly efficient self-healing materials with cerium(III) triflate [Ce(SO3CF3)3] as the metal center and phloretin as the ligand to synthesize a self-healable polyurethane elastomer with excellent self-healable and mechanical properties. Nuclear magnetic resonance data from experimental research on the self-healing mechanism indicated that Ce(SO3CF3)3 and phloretin could effectively form coordination bonds. Then, the hydroxyl group (−OH) on the para position of the phloretin reacted with the isocyanate group in the polyurethane prepolymer to form coordination-bond-facilitated self-healable polyurethane elastomers. An optimal sample (PUPC-2) with high tensile strength (5.17 Mpa) and high stretchability (1,415.7%), ideal toughness (35.08 MJ m−3), and remarkable healing efficiency (near to 100% healed after 48 h at room temperature) was obtained. In addition, the PUPC sample also exhibited good thermoplasticity, which means that the self-healable polyurethane elastomer can be recycled. These excellent performances ensure that the self-healable thermoplastic polyurethane elastomers have a wide range of practical applications. Therefore, a flexible conductive electrode with a self-healable capacity was obtained by compositing the PUPC-2 sample with flexible graphene-based conductive paper, which demonstrated good potential for application in the field of wearable devices and flexible electronics.

Supramolecular Gels with Mouldable Properties from Fatty Acid to make Graphene-Based Nanohybrid Paper

''Paper-like'' materials composed of graphene exhibit good mechanical, thermal and electronic properties and are expected to find a variety of applications. Herein, a simple and elegant strategy has been reported to obtain a graphene-based nanohybrid paper. Mysristic acid in sodium salt-containing aqueous solution forms a stable hydrogel. When myristic acid was mixed with glucose and graphene oxide produces graphene-based gel under the treatment of heating and subsequent cooling through electrostatic stabilization. By applying proper mechanical compression on gel a stable and flexible nanofibrillar graphene-based paper has been obtained without destroying the network structure. This study has enabled to develop of a facile approach to large-scale production of graphene-based paper. The properties of this graphene-based paper have been investigated using electron microscopy, FT-IR spectroscopy, X-ray diffraction and Raman spectroscopy. The obtained paper is thermally stable and resistant to a wide range of organic solvents and therefore interesting in making various advanced electronics.

Laser-assisted synthesis of graphene-based paper for both oil/water mixtures and emulsions separation

Nowadays, dealing with the complex oil/water contamination that contains both oil/water mixtures and emulsions with desirable performance remains a huge challenge. Complicated fabrication procedures, low flux, and efficiency are shortcomings of the known materials. Herein, a facile and effective laser-assisted strategy is proposed to prepare super-hydrophobic graphene/PDMS paper (L-G-P), which perfectly takes advantage of both naturally strong capillary of paper tissue and high-quality graphene. Specifically, graphene is obtained by reducing graphene oxide via laser irradiation, which avoids introducing chemical reducing agents that are either hazardous or hard to separate. Meanwhile, the super-intensive instantaneous energy would create abundant defects on graphene sheets, thus the specific surface area increased by 25%. As for oil/water mixtures, the efficient sorption/separation can realize over 99.99% deep clean, meanwhile showing excellent durability after repeated cycles. As for water-in-oil emulsions, the high separation flux of surfactant-stabilized emulsions could reach 4421 L m−2 h−1 with an efficiency up to 99.85%. Moreover, the mechanical property of the composite was 80.50% stronger than uncoated paper tissue. The proposed L-G-P with durable and efficient oil/water separation performance is a promising material for practical applications for treating oil-contaminated wastewater in harsh environments.

Fabrication and characterization of graphene-based de-icing heater

In this study, graphene based paper was utilized as a potential deicing material. Vacuum bagging technique was used to fabricate the composite panel which consisted of graphene based paper and epoxy/glass fiber. The techniques used to fabricate graphene based paper were chemical vapor deposition (CVD) and hot pressing techniques. Scanning electron microscopy (SEM), optical microscopy, X-ray diffraction and Raman spectroscopy were used to characterize graphene based paper and composite panels. The thermal conductivity and electrical conductivity were measured for graphene based paper. The temperature distribution in the composite panel during deicing tests was studied using infrared thermal imaging. The deicing test based on the joule heating of the composite panel by applying electrical potential. Various electrical potential applied to the composite panel to investigate the role of potential applied on the deicing process. Based on the results, the optimum potential applied 5 V was sufficient to remove ice from panel’s surface with low power consumption. The temperature profile of composite panels showed higher temperature for composite panel of CVD graphene-based paper compared by hot pressing sample because of higher in-plane thermal conductivity for CVD graphene-based paper.

Tungsten Disulfide Nanotube-Modified Conductive Paper-Based Chemiresistive Sensor for the Application in Volatile Organic Compounds' Detection.

Toxic and nontoxic volatile organic compound (VOC) gases are emitted into the atmosphere from certain solids and liquids as a consequence of wastage and some common daily activities. Inhalation of toxic VOCs has an adverse effect on human health, so it is necessary to monitor their concentration in the atmosphere. In this work, we report on the fabrication of inorganic nanotube (INT)-tungsten disulfide, paper-based graphene–PEDOT:PSS sheet and WS2 nanotube-modified conductive paper-based chemiresistors for VOC gas sensing. The WS2 nanotubes were fabricated by a two-step reaction, that is oxide reduction and sulfurization, carried out at 900 °C. The synthesized nanotubes were characterized by FE-SEM, EDS, XRD, Raman spectroscopy, and TEM. The synthesized nanotubes were 206–267 nm in diameter. The FE-SEM results show the length of the nanotubes to be 4.5–8 µm. The graphene–PEDOT:PSS hybrid conductive paper sheet was fabricated by a continuous coating process. Then, WS2 nanotubes were drop-cast onto conductive paper for fabrication of the chemiresistors. The feasibility and sensitivity of the WS2 nanotube-modified paper-based chemiresistor were tested in four VOC gases at different concentrations at room temperature (RT). Experimental results show the proposed sensor to be more sensitive to butanol gas when the concentration ranges from 50 to 1000 ppm. The limit of detection (LOD) of this chemiresistor for butanol gas was 44.92 ppm. The WS2 nanotube-modified paper-based chemiresistor exhibits good potential as a VOC sensor with the advantages of flexibility, easy fabrication, and low fabrication cost.

Ultrasensitive and Low-Cost Paper-Based Graphene Oxide Nanobiosensor for Monitoring Water-Borne Bacterial Contamination.

Water-borne pathogens are mostly generated due to poor sanitation, industrial effluents, and sewage sludge, leading to a significant increase in mortality rate. To prevent this, we need a simple, user-friendly, and rapid on-site detection tool of pathogens, i.e., a biosensor. As contaminated water mainly contains (80%) coliform bacteria, of which Escherichia coli is the major species, we have developed a screen-printed paper-based, label-free biosensor for the detection of E. coli in water. A nanoarchitectured graphene oxide (GO), as a fast electron-transfer flatland, was deposited on the screen-printed graphene (G) on a hydrophobic paper, followed by the immobilization of lectin Concanavalin A (ConA) as a biorecognition element for a GGO_ConA-biosensing electrode. The electrochemical characterization of GGO_ConA shows fast electron transfer with a calculated electroactive surface area of 0.16 cm2. The biosensor performance was tested in the sludge water and beach water (real sample) as an analyte using the electrochemical impedance spectroscopy (EIS) technique. The charge-transfer resistance (Rct) of GGO_ConA increases linearly with the bacterial concentration in the range of 10-108 CFU mL-1 with an estimated limit of detection (LOD) of 10 CFU mL-1, which indicates the ultrasensitivity of our biosensor, with 100 times more sensitivity than previous studies. Our reported biosensor, being cost-effective, eco-friendly, and ultrasensitive, may serve greatly as a portable monitoring kit for checking water-borne bacterial contamination.

The design of lightweight and porous graphene-based composite paper and the study on its electromagnetic interference shielding and fire resistance

Graphene composites that take advantage of lightweight, easy processing and excellent electrical conductivity are promising candidates as functional electromagnetic shielding materials. Herein, zinc oxide (ZnO) nanoparticles were prepared by hydrothermal method and then were introduced into graphene oxide dispersion. The reduced graphene oxide (RGO)/ZnO composite paper was fabricated by evaporation-assisted self-assembly and then reduced by hydrazine hydrate vapor. The results show that the shielding effect of composite paper increases with the increase in the thickness and ZnO dosage. The total electromagnetic interference (EMI) shielding effectiveness of RGO/ZnO composite paper with a thickness of approximately 1 mm is determined as 46.9 dB in the X band. Furthermore, this composite paper has excellent fire resistance. This lightweight and thin RGO/ZnO paper demonstrates a high-performance advanced composite for cutting-edge EMI shielding application in harsh conditions.

Electromagnetic shielding, resistance temperature-sensitive behavior, and decoupling of interfacial electricity for reduced graphene oxide paper

Electromagnetic shielding behavior, resistance temperature-sensitive behavior, interfacial electricity, and their variations with heating treatment of the reduced graphene oxide (RGO) paper are of concern. Herein, self-assembling RGO papers were prepared by solution-phase deposition method. An electromagnetic shielding efficiency (EMSE) of 64 dB shielding (corresponding to a SE/Grammage of 7032 dB/(g/cm2)) covering X-band (8–12 GHz) were obtained. In addition, resistance temperature-sensitive behavior of RGO paper is investigated, and equivalent circuit model is established to decouple interface electricity. The relative resistance variations of RGO paper is caused by the temperature, and the value of ∆R/R0 drops by around 36% when the RGO paper temperature increase from 200 °C to 800 °C. This graphene-based paper provides a simple experimental approach to prepare graphene papers with remarkable electromagnetic shielding performances. More importantly, a qualitative decoupling analysis method is provided for the study and analysis of interfacial electricity. These results and decoupling method can provide useful data and method for carbon-based microwave blockers, sensors and other technologies.

A Facile Approach for the Electrochemical Sensing of Dopamine using Paper-Based PEDOT:PSS/RGO Graphene Biosensor

In this study, we have developed a paper-based electrochemical biosensor for dopamine (DA) detection. For this purpose, a screen-printed graphene electrode (SPGNE) was printed on a paper substrate, and the electrode surface was modified with PEDOT:PSS/RGO. The fabricated sensor was characterized by analyzing the capacitance, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) measurements. Differential pulse voltammetry (DPV) was employed for the quantitative detection of dopamine. The paper-based SPGNE biosensor developed in this study could detect dopamine in a linear range from 0.0125 to 0.1 mM with a sensitivity of 24.9 μA mM−1. The reliability of the developed biosensor for dopamine detection was assessed by using normal serum samples. The paper-based graphene biosensor proposed in this study could be low-cost and eco-friendly, and its ability to determine the dopamine from real serum samples showed promising results. The developed SPGNE dopamine-sensing biosensor could be potentially applied for the early-stage diagnosis of various neurological diseases/disorders.

Ultrastrong Carbon Nanotubes/Graphene Papers via Multiple π-π Cross-Linking.

Considering the extraordinary properties of graphene nanosheets, graphene-based materials from a molecular level to a macroscopic level as paper-like graphene films have recently grown for promising applications in many fields. However, there is still a major challenge in the design of the interface between adjacent graphene nanosheets so as to achieve high strength, high toughness, and high conductivity. Herein, we construct the high-performance graphene-based papers by using graphene as the matrix, carbon nanotubes (CNTs) as the reinforcement, and a long-chain molecule (1-pyrenylbutyric acid-linear diamine-1-pyrenylbutyric acid, PBA-diamine-PBA) as the bridging agent. The multiple π-π interactions between the fused rings, graphene nanosheets, and CNTs are generated among the aromatic rings of PBA, rGO, and CNTs, which significantly improve the mechanical properties and electrical properties of the cross-linked composite papers (abbreviated to CLP-X, where X is the carbon chain length). Furthermore, the linear diamines with different lengths of carbon chain affect the properties of papers after cross-linking. Especially, the as-obtained graphene-based paper (CLP-6) shows a high tensile strength (625.2 MPa), high toughness (28.5 MJ/m3), and high electrical conductivity (233.4 S/cm) as well as high solvent stability, which maintains the premium stability in different solvents. The improvement of strengthening and toughening mainly comes from the effective stress transfer and the reduction of slipping distance between rGO and CNTs during the stretching, with the help of multiple π-π cross-linking by in situ Raman analysis and simulation calculations. In addition, the high electrical conductivity leads to an excellent electromagnetic interference shielding capability (44,502 dB·cm2/g). The distinguished electric heating performance with rapid response to temperature changes is also recognized. Therefore, the proposed interface design is demonstrated as an effective way for developing a graphene-based paper with superior properties.

Facile synthesis of paper based graphene electrodes for point of care devices: A double stranded DNA (dsDNA) biosensor

The demand for high-quality graphene for electronic applications is increasing due to its high carrier mobility and electrical conductivity. In this connection, printing technology is a reliable method towards the fabrication of conductive, disposable graphene-based electrode for low-cost sensor application. Herein, we aimed to report the synthesis of high-quality graphene nanosheets obtained by electrochemical exfoliation of biomass-derived from corn cob. The conductive ink was prepared from this exfoliated graphene and was utilized for the preparation of paper-based graphene electrode towards double stranded DNA (dsDNA) sensor application. This paper, based graphene electrode opens the possibility of direct electrochemical analysis of analyte without any sample preparation. In this study, two irreversible oxide peaks were obtained from paper-based printed graphene electrode, corresponds to oxidation of guanine (G) and adenine (A) of dsDNA in the linear range of 0.2 pg mL−1 to 5 pg mL−1 with the detection limit of 0.68 pg mL−1 and the sensitivity of 0.00656 mA pg−1 cm−2. Further, a small-scale printable circuit is fabricated using this graphene shows good conductivity of 1.145x103(S/m).

3D hierarchically porous NiO/Graphene hybrid paper anode for long-life and high rate cycling flexible Li-ion batteries

With the rapid emergence of wearable devices, flexible lithium-ion batteries (LIBs) are much more needed than ever. Free-standing graphene-based composite paper electrodes with various active materials have appealed wide applications in flexible LIBs. However, due to the prone-to-restacking feature of graphene layers, a long cycle life at high current densities is rather difficult to be achieved. Herein, a unique three-dimensional (3D) hierarchically porous NiO micro-flowers/graphene paper (fNiO/GP) electrode is successfully fabricated. The resulting fNiO/GP electrode shows superior long-term cycling stability at high rates (e.g., storage capacity of 359 mAh/g after 600 cycles at a high current density of 1 A/g). The facile 3D porous structure combines both the advantages of the graphene that is highly conductive and flexible to ensure rapid electrons/ions transfer and buffer the volume expansion of NiO during charge/discharge, and of the micro-sized NiO flowers that induces hierarchical between-layer pores ranging from nano-micro meters to promote the penetration of the electrolyte and prevent the re-stacking of graphene layers. Such structural design will inspire future manufacture of a wide range of active materials/graphene composite electrodes for high performance flexible LIBs.

Fabrication and characterization of graphene-based paper for heat spreader applications

In this work, in-plane thermal conductivity measurement was carried out on graphene-based papers. Graphene-based papers were fabricated using various processing techniques such as chemical vapor deposition (CVD), hot pressing of graphene slurry, and evaporation induced self-assembly. The prepared materials were characterized using scanning electron microscopy, Raman spectroscopy, and X-ray diffraction. In-plane thermal conductivity measurement was performed via a steady state thin film thermal conductivity apparatus. The in-plane thermal conductivity measurements show that the CVD based sample has the highest thermal conductivity. COMSOL Multiphysics was used to simulate the in-plane thermal conductivity of graphene-based papers.

Flash foam stamp-inspired fabrication of flexible in-plane graphene integrated micro-supercapacitors on paper

Developing patterning techniques with practicability, cost-effectiveness and safety are essential for shape-confirmable integrated energy storage devices. Herein we design a novel flash foam stamp-inspired technique for simple fabrication of flexible high energy in-plane micro-supercapacitors based on interdigital electrodes of self-depositing electrochemically exfoliated graphene on paper substrates. This technique is an attractive and novel bottom-up microfabrication technology due to its advantages of simplicity and low-cost. These novelly developed all-solid-state, paper-based in-plane graphene micro-supercapacitors exhibit excellent electrochemical performances, such as high area specific capacitance of ∼4.02 mF cm−2 and excellent cycling stability (95.6% retention at 0.08 mA cm−2 for 5000 cycles). And these solid-state flexible micro-supercapacitors are observed non-obvious structural change and loss of performance under bending state, suggesting remarkable flexibility and mechanical stability. Therefore, such all-solid-state, flexible paper-based graphene micro-supercapacitors can potentially be used for wearable and portable electronics.

Micro Paper-Based Electrochemical Device for Small Molecule Diabetes Biomarkers

Glucose monitoring has been widely established as a successful diabetes management system. However, non-glucose markers such as, autoantibodies, hormones, proteins, and other small molecules can provide better assessments for the prediction and management of the disorder. Nevertheless, the challenges our research community faces in designing an analytical device for such markers, especially the small molecules, are the dynamic range, limit of detection, selective isolation of the analyte, higher background noise due to clinical matrix, and ability to transform the system into a cheap point-of-care device. Here, we have designed a paper-based graphene amperometric sensor that can detect a model hormone (insulin, 5808 Da) from complex serum matrix. The paper platform provides for a cheap, on-site filtration system that limits the mobility of larger molecules, and upon combining with a double-blocking step before analyte detection greatly minimizes the background noise. Insulin aptamers acts as a capture probe to selectively identify and bind to insulin. Graphene, coated on working electrode, with its superior electrical conductivity provides for improved analytical features of the detection system. The amperometric signals are achieved by flowing a solution mixture of 1 mM hydroquinone mediator and 0.5 mM H2O2 and applying a constant potential of -0.1 V. The paper-based device exhibits a picomolar limit of detection for serum insulin with a reasonably good dynamic range. Our future prospect is to advance this device further for detecting even smaller molecules (< 500 Da) in complex clinical matrices, for which no current assay methods are available.