Graphene Nanocomposite Film Research Articles

Hybrid nanocomposites for enhanced photodetection: Synthesis and application of Ag2O@Graphene/Si heterojunctions

Thin silver oxide graphene (Ag2O@G) nanocomposite films were synthesized via facile spray pyrolysis and integrated into heterojunction architectures with silicon substrate. Structural characterization confirmed the successful anchoring of crystalline Ag2O nanoparticles uniformly over graphene layers with strong interfacial coupling. Optical analysis showed synergistic tuning of the band structure by hybridization, which improves light absorption. Electrical measurements showed rectification behavior of the diode and an increase in photocurrent up to milliamperes under illumination. A response time of 350 ms, a recovery time of 400 ms, stability over repeated cycles and exceptional values such as 0.39 A/W responsivity, 88 % external quantum efficiency and 4×1011 Jones detectivity at 600 nm were achieved. The nanocomposite heterojunctions utilize the superior charge mobility of graphene with the bandgap tuning of Ag2O, enabling efficient light harvesting, photogeneration, and ambipolar charge separation and transport across the multifunctional interface. Customized Ag2O@G heterostructures represent a promising material platform to drive advances in high performance photodetectors, image sensors, night vision devices and photovoltaics through the engineering of morphology, crystallinity and interfaces.

Evaluating the reactivity of polyvinyl alcohol/graphene nanocomposites

The synthesis and characterization of polyvinyl alcohol (PVA)/graphene nanocomposite films, through the solution casting technique, were thoroughly explored and studied. The integration of varying concentrations of graphene was systematically explored to enhance the structural and optical attributes of the PVA matrix. Comprehensive characterization employing X-ray Diffraction (XRD), Fourier-Transform Infrared (FTIR) Spectroscopy, and Ultraviolet–Visible (UV–Vis) Spectrophotometry revealed significant interactions between PVA and graphene, manifesting in a decrease in crystallinity and optical bandgap with increasing graphene content. DFT:B3LYP/6-31g(d,p) quantum mechanical level, corroborated these findings by indicating a diminished HOMO/LUMO bandgap energy. Additionally, molecular electrostatic potential mapping underscored an increase in PVA's reactivity post-graphene integration. The investigation further extends to evaluating global reactivity descriptors, providing insights through PDOS plots and QSAR analysis. The outcomes of this research underscore the potential of PVA/graphene nanocomposites for next-generation applications in flexible photovoltaic cells, transistors, and diodes.

Inkjet-printed sub-zero temperature sensor for real-time monitoring of cold environments

Real-time monitoring of low temperatures (usually below 0 °C) or cold environments is a specific requirement that finds its high demand in the aerospace, pharmaceutical, food, and beverage industries to maintain the temperature at high altitudes or in refrigerators and cold storage. In general, this purpose is achieved by using a sub-zero temperature sensor coupled with a control system. However, the market available such temperature sensors are very expensive, and bulky, thus not being suitable for portable operation, and also they suffer from poor accuracy. Therefore, the development of high-performance, low-cost, lightweight, and portable sub-zero temperature sensors is highly desired. In our recent work, we developed such sensors and integrated them with auxiliary electronics to demonstrate their wireless operation for the continuous and real-time monitoring of cold environments. So, in order to obtain low-cost sensors a cost-effective inkjet printing technology was employed for the fabrication of devices. A lightweight polydimethylsiloxane (PDMS) was used as the substrate and an electrically conducting graphene nanocomposite was used as the temperature-sensing material. To obtain a functional graphene nanocomposite film with a thickness of 530 nm and a conductivity of ~189 S m−1, the printed graphene nanocomposite was photonically sintered using a xenon flash lamp. This step was crucial for obtaining a sensor on the soft PDMS platform. The graphene nanocomposite film exhibited a positive temperature coefficient resistance value of approximately 0.119 %/°C, and its resistance values varied almost linearly (with an Adjusted R2 value (model accuracy) of 0.99) with temperature within the operating range of −30 °C to 80 °C. The sensor was properly encapsulated for protection without significantly affecting its performance. The sensors demonstrated sufficient flexibility, with a bending radius of 20 mm, and sustained 500 continuous bending cycles. Finally, the real-time operation of the sensors was demonstrated by wirelessly transmitting and monitoring the temperature over a smartphone platform.

Different aspects of polymer films based on low‐density polyethylene using graphene as filler

AbstractThe focus of the present work is to prepare low‐density polyethylene (LDPE)‐graphene (G) nanocomposite films with improved gas barrier properties by melt extrusion. A narrow range of the graphene (0.05–0.3 wt.%) as filler was used in the LDPE matrix. The rheological analysis indicating that there is no significant influence on the LDPE chains mobility with the addition of filler. The nanocomposites percent crystallinity (Xc%) increase from 25.0% to 31.6% compared to neat LDPE. The X‐ray diffractogram shows a change in width half height of the peak positioned at 26° ((002) plane) from 0.69 (graphite) to 1.24 (graphene), revealing the asymmetry of this plane. The optical microscopy images show a good dispersion of the nanoparticles in the polymer matrix. The mechanical properties of the nanocomposites in longitudinal direction demonstrate better improvement with addition of the filler as compared to the transverse direction. The contact angle measurements of nanocomposites for water and ethylene glycol do not shows a significant variation in comparison to neat LDPE. The nanocomposites show 26% enhancement in the oxygen barrier property. Thus, here we present the cost‐effective LDPE‐graphene nanocomposites with improve oxygen barrier property, which can be used in different industrial application especially in food packaging.

PVA biopolymer-acidic functionalized graphene hybrid nano composite for vibration isolation application: An experimental approach with variable reflux and vacuum timings

In this research work, polyvinyl alcohol (PVA)-graphene (Gr) nano composite films were fabricated by incorporating the functionalized graphene (f-Gr) for different periods of refluxing and vacuum oven time. The graphene particles were functionalized through nitric acid (HNO3). Various tests were conducted to estimate the properties and characteristics of this composite. Fourier transform infrared spectroscopy (FTIR) results confirm the bonds of carboxyl, hydroxyl and carbonyl groups, manifested of functionalization of graphene. Scanning electron microscopy was performed to investigate morphology and transparency of f-Gr nano-particles in nano-composite films. Water absorption test was carried out to evaluate water absorption (%) in the PVA based composite films. The result revealed that water absorption rate of the composite decreased with increasing refluxing time at constant vacuum oven time of f-Gr reinforced composite. Dynamic mechanical analysis (DMA) showed that the value of storage modulus was higher for PVA-f-Gr nano-composite films compared to neat PVA and PVA-Gr composite over the entire range of temperature, which lead to explore this composite material for the vibration isolation applications. Glass transition state (Tg), loss modulus and the damping factor (tan δ) of the PVA-f-Gr nano composites films were highly affected by the addition f-Gr nano crystals in the PVA matrix. The value of tan δ for f-Gr nano composite is obtained both higher as well as lower compared to PVA-Gr film for the varying vacuum oven time and refluxing time. Electrical analysis indicates an enhancement in conductivity of PVA with introduction of f-Gr nano particles. After evaluating the high damping characteristics of this composite, the authors perceive that it may be utilized to reduce noise transmission and as a shock absorber vibration isolator.

Investigation of dynamic impact responses of layered polymer-graphene nanocomposite films using coarse-grained molecular dynamics simulations

Polymer nanocomposite films have recently shown superior energy dissipation capability by using the micro-projectile impact testing method. However, how stress waves interact with nanointerfaces and the underlying deformation mechanisms have remained largely elusive. This paper investigates the detailed stress wave propagation process and dynamic failure mechanisms of layered poly(methyl methacrylate) (PMMA)-graphene nanocomposite films during piston impact through coarse-grained molecular dynamics simulations. The spatiotemporal contours of stress and local density clearly demonstrate shock front, reflected wave, and release wave. By plotting shock front velocity (Us) against piston velocity (Up), we find that the linear Hugoniot Us−Up relationship generally observed for bulk polymer systems also applies to the layered nanocomposite system. When the piston reaches a critical velocity, PMMA crazing can emerge at the location where the major reflected wave and release wave meet. We show that the activation of PMMA crazing significantly enhances the energy dissipation ratio of the nanocomposite films, defined as the ratio between the dissipated energy through irreversible deformation and the input energy. The ratio maximizes at the critical Up when the PMMA crazing emerges and then decreases as Up further increases. We also find that a critical PMMA-graphene interfacial strength is required to activate PMMA crazing instead of interfacial separation. Additionally, layer thickness affects the amounts of input energy and dissipated energy for nanocomposite films under impact. This study provides important insights into the detailed dynamic deformation mechanisms and how nanointerfaces/nanostructures affect the energy dissipation capability of layered nanocomposite films.

Fabrication of Conductive Tissue Engineering Nanocomposite Films Based on Chitosan and Surfactant-Stabilized Graphene Dispersions.

Chitosan (CS)/graphene nanocomposite films with tunable biomechanics, electroconductivity and biocompatibility using polyvinylpyrrolidone (PVP) and Pluronic F108 (Plu) as emulsion stabilizers for the purpose of conductive tissue engineering were successfully obtained. In order to obtain a composite solution, aqueous dispersions of multilayered graphene stabilized with Plu/PVP were supplied with CS at a ratio of CS to stabilizers of 2:1, respectively. Electroconductive films were obtained by the solution casting method. The electrical conductivity, mechanical properties and in vitro and in vivo biocompatibility of the resulting films were assessed in relation to the graphene concentration and stabilizer type and they were close to that of smooth muscle tissue. According to the results of the in vitro cytotoxicity analysis, the films did not release soluble cytotoxic components into the cell culture medium. The high adhesion of murine fibroblasts to the films indicated the absence of contact cytotoxicity. In subcutaneous implantation in Wistar rats, we found that stabilizers reduced the brittleness of the chitosan films and the inflammatory response.

Dielectric Biodegradable Biopolymer‐Based Graphene Nanocomposites for Use in the Packaging Industry and Capacitor Application

AbstractIn this study, polyhydroxyalkanoate (PHA) and polylactic acid (PLA)‐Graphene (G) nanocomposite films were synthesized by taking different concentrations of G via the solution casting process, and their structural, mechanical, opacity, thermal and dielectric properties were examined for the first time. Scanning electron microscopy (SEM) was used for investigating surface morphology. Films containing graphene were more opaque than films without graphene. The incorporation of graphene into the polymer matrix improved the mechanical property. The tensile strengths of the control PHA/PLA film and the graphene‐reinforced 1 %G‐PHA/PLA nanocomposite films were 18.98 and 24.34 MPa, respectively. Thermogravimetric analysis results showed that PHA/PLA−G nanocomposites had good thermal stability below 300 °C. Considering the dielectric measurements, it is seen that the dielectric constant (έ) and dielectric loss (ϵ”) decreased with increasing frequency and less changed at higher frequencies. The developer feature of graphene is remarkable in both parameters. The electrical conductivity of PHA/PLA−G nanocomposites was also examined as a function of frequency at room temperature. As the amount of G increased from 1 %wt to 5 %wt, the conductivity of the composites increased.

Modification of graphene with two strong acids and its nanocomposites with 2-hydroxyethylcellulose

Simple and cost-effective, eco-friendly, graphene-based “green” nanocomposite films are produced with the solvent casting method. For this purpose, commercially procured nanographene was used as reinforcement material and 2-hydroxyethyl cellulose (2-HEC), a cellulose-derivative natural polymer, was used as a matrix. Nanographene was modified with HCl and HNO3 to ensure blending with the cellulose matrix, and 2-HEC/acid modified graphene nanocomposite films were produced. The results show that the basic structure of the graphene is preserved after the HCl and HNO3 modifications. FT-IR, XRD, and Raman Spectroscopy results show that the graphene attained hydrophilic property by creating functional ends (hydroxyl group, –OH) on the edges of the graphene sheet with acid modification. Morphology studies with SEM and AFM methods have also confirmed the acid modification to the graphene. TGA/DTG work revealed that nanocomposite films obtained as a result of the doping of HNO3 modified graphene to the 2-HEC matrix were found to be thermally more stable than the original 2-HEC film. In this study, where 2-HEC is used as a matrix, the hydrophilic property has been achieved with the hydrophobic graphene by acid modification. The resulting 2-HEC/acid modified graphene nanocomposite materials have the potential to lead to innovation in applications such as lithium-ion batteries and sensor design, water treatment and even drug delivery systems.

Superior rate capability and cyclic stability of poly orthoaminophenol nanocomposite film in the presence of benzidine functionalized graphene oxide

AbstractIn this study, benzidine (BnZ) is used not only as a reducing agent but also as the spacer on the supercapacitive behavior of the synthesized graphene nanocomposite film. The synthesized graphene nanocomposite was examined by crystalline size, structural morphology, presence of functional groups to X‐ray diffraction, scanning electron microscope, and Fourier transform infrared spectroscopy. Furthermore, chemical composition moieties are evidenced by X‐ray photoelectron spectroscopy. Poly ortho aminophenol as a p‐type conductive polymer was introduced into the channels of Bnz‐rGOAerogel. This composite structure with a high surface area and pore volume can effectively play a synergistic role between the two materials, thus improving its overall performance. In addition, the specific capacitance of the prepared spherical composite electrode is as high as 625 F/g at 1.0 A/g current density, and the retention rate of the initial capacity is 89% after 3,000 cycles in acidic solution, which has good cycle stability.

Glucose Bio Sensor Base Nanocomposite Graphene/Tio2

The use of graphene and titanium oxide nano-mixtures in a wide variety of physical products, such as solar panels, biosensors and fuel cells. Owing to the special general physical properties of TiO2 and graphene, graphene has a huge conductivity to sustain TiO2 and is used as a photo catalyst in water and moisture solutions in bio nano sensors. TiO2 has special features, such as stability low toxicity and cost-effectiveness. Primary findings have shown that the manufacture of the system sensor displays a great and quick reaction to glucose to be the ideal biosensor unit The use of TiO2 is limited by its wide band gap energy contributing to light absorbance in the UV spectrum area and the relatively high rate of recombination of photo-generated electrons. The use of G / TiO2 to improve photocatalytic behavior and stability so that maximum electrical sensitivity can be achieved. Preparation of Titanium dioxide / Graphene nanocomposite thin film for glucose exposure by spray pyrolysis technology (SPT), Scanning Electron Microscopy ( SEM) and X-Ray Diffraction (XRD) are structural and morphology studies.

A study of conductive thermoplastic elastomeric polyurethane and graphene nanocomposite thin films for application to flexible electrical sensors

ABSTRACT Pressure-sensitive thin film is one of the major components in flexible electrical sensors (e-skin sensors). The thin film are normally conductive and durable. However, its applications are often limited, due to its big noise and hysteresis. In this research, we developed a new nanocomposite made with thermoplastic-polyurethane (TPU) and graphene to measure contact pressure. To ensure a minimum noise level in the measurement, we prepared it through an iterative heating, sonication, and phase inversion process. Then we studied the relationship between the measured resistance and applied force through the comprehensive consideration of the graphene weight percentage, the size of the sensing elements, and the loading/unloading speed. We also characterised its hysteresis and repeatability. Finally, the nanocomposite with the best comprehensive results was selected and stencil-printed in the holes on a polydimethylsiloxane film to be used as the sensing element of e-skin sensors.

Chitosan-Functionalized Graphene Nanocomposite Films: Interfacial Interplay and Biological Activity.

Graphene oxide (GO) has recently captured tremendous attention, but only few functionalized graphene derivatives were used as fillers, and insightful studies dealing with the thermal, mechanical, and biological effects of graphene surface functionalization are currently missing in the literature. Herein, reduced graphene oxide (rGO), phosphorylated graphene oxide (PGO), and trimethylsilylated graphene oxide (SiMe3GO) were prepared by the post-modification of GO. The electrostatic interactions of these fillers with chitosan afforded colloidal solutions that provide, after water evaporation, transparent and flexible chitosan-modified graphene films. All reinforced chitosan–graphene films displayed improved mechanical, thermal, and antibacterial (S. aureus, E. coli) properties compared to native chitosan films. Hemolysis, intracellular catalase activity, and hemoglobin oxidation were also observed for these materials. This study shows that graphene functionalization provides a handle for tuning the properties of graphene-reinforced nanocomposite films and customizing their functionalities.

Investigations on the properties of indium sulphide –Graphene nanocomposite thin films

Indium sulphide (In2S3) is a versatile material having applications in optoelectronics and photovoltaics, whose properties could be tailored by incorporation or doping. We report incorporation of graphene in indium sulphide (In2S3-Gr) thin films by two step process. The pure samples are synthesized by chemical bath deposition. Incorporation of graphene in these thin films is done by spin coating followed by annealing. Structural analyses of pure and In2S3-Gr thin films are carried out by using Grazing Incidence X-Ray Diffraction, Field Emission Scanning Electron Microscopy, X-ray Photoelectron Spectroscopy and Raman spectroscopy. In this work, investigations on electrical, thermal and optical properties of In2S3-Gr thin films are also conducted. The systematic characterisations revealed that In2S3-Gr nanocomposite thin films are synthesized by this process. Also, the samples showed significant modifications in its structural and optoelectronic properties by incorporation of graphene. In2S3-Gr thin films prepared could be useful in various optoelectronic devices including photovoltaics and as a photocatalyst.

Transparent, High-Thermal-Conductivity Ultradrawn Polyethylene/Graphene Nanocomposite Films.

Transparent, ultradrawn, ultrahigh molecular weight polyethylene (UHMWPE)/graphene nanocomposite films with a high thermal conductivity are successfully fabricated by solution-casting and solid-state drawing. It is found that the low optical transmittance (<75%) of the ultradrawn UHMWPE/graphene composite films is drastically improved (>90%) by adding 2-(2H-benzontriazol-2-yl)-4,6-ditertpentylphenol (BZT) as a second additive. This high transmission is interpreted in terms of a reduced void content in the composite films and the improved dispersion of graphene both of which decrease light scattering. The high thermal conductivity is attributed to the π-π interaction between BZT and graphene. In addition, a high specific thermal conductivity of ≈75 W m-1 K-1 ρ-1 of the ultradrawn UHMWPE/graphene/BZT composite films is obtained, which is higher than most metals and polymer nanocomposite. These transparent films are potentially excellent candidates for thermal management in various applications due to a combination of low density, ease of processing, and high thermal conductivity.

Valorization of sugarcane straw to produce highly conductive bacterial cellulose / graphene nanocomposite films through in situ fermentation: Kinetic analysis and property evaluation

Abstract Bacterial cellulose based nanocomposites have found a growing interest in recent decades due to their impressive inherent characteristics with potential applications in diverse sectors. However, there remain several challenges due to increased production cost, lower yield, and sustainability or biocompatibility issues after chemical-based modifications. This study demonstrates the fabrication of bacterial cellulose-reduced graphene oxide films via in-situ fermentation approach using abundantly available agricultural waste (sugarcane straw) as a feedstock. The presence of reduced graphene oxide at different concentrations in culture media, significantly altered the fermentation kinetics, as evident from kinetic parameter and yield coefficients. Higher yields of bacterial cellulose-reduced graphene oxide nanocomposites, with presence of strongly integrated network-like structures between bacterial cellulose nanofibers and reduced graphene oxide nanosheets were observed at 2 wt % reduced graphene oxide loadings. Formation of such percolated networks was confirmed from improved mechanical properties and enhanced electrical conductivity, through both experimental and modeling investigations. The proposed in-situ fermentation technique to produce highly conductive bacterial cellulose-reduced graphene oxide films provides an alternative approach to meet the growing demands of biomass-derived renewable and sustainable biomaterials with commercial significance.

Flexible cellulose nanofibril/pristine graphene nanocomposite films with high electrical conductivity

Cellulose nanofibrils extracted from wood are natural polymer nanomaterials with high specific surface area, low density, high strength, and high elastic modulus. However, they are insulating materials and cannot be directly used in the electronic devices. Herein, pristine graphene (PG) exfoliated by triethanolamine was used to composite with TEMPO-oxidized cellulose nanofibril (TOCN) to prepare the conductive nanocomposite films in aqueous system. As a reference, the graphene oxide (GO) and reduced graphene oxide (RGO) were also composited with TOCN to prepared the TOCN−GO and TOCN−RGO composite films. The maximum electrical conductivity of the TOCN−PG film was 568 S/cm with 20 wt% PG, achieving great enhancement than the TOCN film with insulation. It was also much higher than the TOCN−GO films (3.44 × 10−11 S/cm) and about 185 times more than TOCN−RGO composite films (3.06 S/cm). Moreover, the TOCN−PG composites containing 10 wt% PG exhibited excellent tensile strength, elastic modulus and the elongation at break of 389 MPa, 8.0 GPa and about 20%, respectively, much higher than those of the neat TOCN film.

TPU/graphene nanocomposites: Effect of graphene functionality on the morphology of separated hard domains in thermoplastic polyurethane

Graphene nanoplatelets with different surface functional groups and polarity were prepared by Hummer's method and electrochemical exfoliation of graphite in two aqueous acids. The XRD, FTIR and sedimentation tests performed to characterize the polarity of the prepared graphenes. The highest polarity was associated with the sample prepared by Hummer's method and the sample synthesized by electrochemical exfoliation in nitric acid medium showed the moderate polarity. Meanwhile, the sample prepared in sulfuric acid medium showed the lowest polarity. Then thermoplastic polyurethane (TPU)/graphene nanocomposite films were fabricated with solvent exchange method. While the dispersion state and interaction of graphene/segmented polymer in solution state were evaluated with rheological measurements, optical microscope images illustrated the well dispersion of more polar graphene in TPU nanocomposite film. Moreover, the effect of graphene polarity on the phase separation and formation of hard domains with crystalline structure was extensively discussed based on DSC test results. The changes in phase separation between hard and soft segments and the formation of hard domains with specific structures greatly affected the mechanical properties of final nanocomposite films. The electrical conductivity of TPU/graphene nanocomposite film showed the role of graphene polarity nanoplatelets on the development of the conductive network in TPU matrix.

On the absorption dominated EMI shielding effects in free standing and flexible films of poly(vinylidene fluoride)/graphene nanocomposite

The present work highlights the remarkably high electro-magnetic interference (EMI) shielding effectiveness of about 47 dB, exhibited by highly conducting and ordered poly(vinylidene fluoride) (PVDF)/graphene nanocomposite films of thickness around 20 µm, in the microwave frequency range 8–12 GHz, obtained by solution casting method. The films were characterized structurally using X-ray diffraction, Fourier transform infrared spectroscopy and Raman spectroscopy and the analysis indicates the enhancement in the highly ordered β phase of PVDF with the incorporation of graphene. In the entire frequency range of analysis, by absorption loss to the total EMI shielding effectiveness is very high compared to that by reflection loss. The high electrical conductivity of the composite films promotes shielding by absorption losses which is of ample significance in stealth applications. The present results identify the PVDF/graphene nanocomposite film as an effective, lightweight, free standing, flexible, mechanically and thermally stable, absorption dominated EMI shielding material with application prospects in a broad range of electromagnetic spectrum. The shielding effectiveness of these highly conducting nanocomposite films, far exceeds most of the previously reported values and meets the commercial requirements. The freestanding and flexible nature of these films facilitates EMI shielding applications without the geometrical constraints of the shape or size of the object.

Fabrication and electrical characterizations of graphene nanocomposite thin film based heterojunction diode

The use of graphene in electronic devices is becoming attractive due to its inherent scalability and is thus well suited for flexible electronic devices. Here we present the electrical characterization of heterojunction diode, based on the nanocomposite of graphene (G) with silver nanoparticles (Ag NPs), at room temperature. The diode was fabricated by depositing nanocomposite on the n-Si substrate. The current – voltage (I – V) characteristic of the fabricated junction shows rectifying behavior similar to a Schottky junction. The junction parameters such as ideality factor (n), series resistance (Rs), and barrier height (ϕb) has been extracted, using various methods, from the experimentally obtained I – V data. The measured values of n, Rs and ϕb are 3.86, 45Ω and 0.367eV, respectively, as calculated from the I – V curve. The numerical values of these parameters calculated by different methods are in good agreement with each other showing the consistency of the applied calculating techniques. The conduction mechanism of the fabricated diode seems to have been dominated by the Trap Charge Limited Conduction (TCLC) behavior. The energy distribution of interface states density determined from forward bias I – V characteristic shows an exponential decrease with bias from 27 × 1013cm−2eV−1 at (Ec – 0.345)eV to 3 × 1013cm−2eV−1at (Ec – 0.398)eV.