Graphene Carbon Nanotube Hybrid Research Articles

A Review: Synthesis and Mechanism of Growth of the Carbon Nanotubes (CNTs) – Graphene Hybrid Material and its Application as Electrodes

The CNTs–graphene hybrids have many advantages and potential for use in a wide range of electronic applications as electrodes. The CNTs–graphene hybrid structure outperforms the structure of each material in terms of characteristics and performance. There are several methods to grow CNTs. This paper reviews the chemical vapor deposition (CVD) method used to synthesize CNTs–graphene hybrid material. This paper discusses the processes and growth parameters of the synthesis of the CNTs-graphene hybrid. This paper also discusses the growth mechanism and kinetics of CNTs. In addition, the potential and performance of CNTs–Graphene hybrid material as electrodes in batteries are also reviewed.

Hybrid CoFe2O4-CNTs-graphene: Synthesis and characterization for energy storage devices

Hybrid materials play a crucial role in a spectrum of energy storage devices. Among them CoFe2O4–CNT–graphene hybrid stands out as versatile magnetic materials with wide-ranging applications spanning electronics, magnetism, and sensor industries. In this study, we synthesized CoFe2O4–CNT–graphene hybrid utilizing ultrasonication method. This fabrication method resulted in the formation of CoFe2O4 nanoparticles, along with bamboo-like carbon nanotubes (CNTs) and graphene nanosheets which collectively establish an open three-dimensional structure. Thorough analyses were conducted on the synthesized nano-composites employing various characterization techniques such as XRD, FT-IR, Raman and FESEM. Further characterization through XPS confirmed the formation of spinel ferrites, detecting the presence of carbon sp2, C1s, carboxylates (O-C-OH), and sp3 carbon, indicating the presence of carbon‑carbon (CC) bonds and confirms the energy levels of Co2p1/2 and Co2p3/2 indicating the effective incorporation of CFO onto the CNT/graphene surface. Analysis of dielectric parameters revealed promising characteristics for high-frequency devices, attributed to low dielectric loss, high quality factor, short relaxation time, and diverse responses exhibited by these materials. The M–H loops of the composite samples displayed ferromagnetic hysteresis behavior due to the presence of ferrite in the matrices. The coercivity value shows a slight improvement in the hybrid samples, while saturation magnetization values decrease, indicating a 1:1 weight ratio of ferrite particles to the host matrix with the incorporation of nonmagnetic CNTs and graphene, and the Hc value increases with the addition of these carbon-based materials due to increased surface anisotropy energy. Upon evaluation of dielectric and magnetic properties the hybrid materials demonstrated an enhanced dielectric and magnetic properties which render these materials suitable for utilization across a spectrum of energy storage devices.

Advancements in Glucose Monitoring: A Thin Film ZnO-Nanoflakes Based Highly Sensitive Wearable Biosensor for Noninvasive Sweat-Based Point-of-Care Monitoring for Diabetes

In the contemporary global landscape, diabetes is a prevalent and concerning presence that contributes to noteworthy mortality rates. The etiology of this condition involves a subtle interaction between insulin deficiency and elevated blood sugar levels which results in a complex metabolic disorder. The harmful consequences of this physiological abnormality become evident through the increased probability of kidney failure, heart attack, chronic liver diseases, and a pernicious ocular affliction leading to blindness. Against this backdrop, the necessity for prompt, accurate, and continuous monitoring of glucose concentrations with any form of flexible sensor becomes notably evident for type I and type II diabetes patients, pregnant women with diabetes, athletes, and high-risk persons. Sweat, an often-overlooked physiological excretion, is a reservoir of vital biological information due to its accessibility and analyzability. It is an advantageous matrix for glucose monitoring, surpassing blood, saliva, and tears. Its non-invasive nature offers a patient-friendly alternative to conventional blood sampling. The continuous, real-time nature of sweat extraction facilitates dynamic monitoring without the discomfort associated with invasive methods. This inherent advantage positions sweat as a promising matrix for glucose sensing, underscoring its potential as a valuable tool in diabetes management. It overcomes the limitations posed by other bodily fluids like saliva and tears in terms of accessibility, patient comfort, and reflective accuracy. The assimilation of nanomaterials into biosensing technologies heralds a paradigm shift, conferring heightened sensitivity upon these mechanisms. Noteworthy among these innovations are flexible wearable biosensors leveraging zinc oxide (ZnO) thin films, offering promising avenues for the discernment of glucose levels within sweat for healthcare monitoring. ZnO nanoflakes (ZnO-NFs) distinguish themselves by endowing flexible biosensors with unparalleled sensitivity, reliability, continuous monitoring capabilities, and non-invasiveness from zinc oxide nanoparticles incorporated graphene-carbon nanotube hybrid (GR-CNT-ZnO) and ergocalciferol-multi walled carbon nanotubes based (ERGOc-MWCNTd/Nf) traditional glucose sensors. The distinctive advantages of ZnO-NFs over bulk materials are multifaceted. Notably, the polarized (0001) plane orientation inherent in ZnO-NFs amplifies enzyme immobilization, thereby augmenting sensing performance. The elevated isoelectric point (9.5) of ZnO-NFs facilitates the immobilization of biomolecules, obviating the need for an ancillary binding layer. A single-step and efficacious sonochemical approach has been used to synthesize a thin layer of ZnO-NFs virtually on any substrate. The electrochemical flexible glucose biosensor was fabricated through the judicious immobilization of glucose oxidase (GOx) on ZnO nanoflakes, possessing a mere 20nm thickness and synthesized adeptly on an Au-coated stretchable polyethylene terephthalate (PET). The sensitivity of the flexible biosensor was determined by 29.97 μA/decade/cm² and the minimum detection limit is 100 μM. The coefficient of determination of the designed flexible electrode is found 97.76%, which is significantly linear. The designed PET/Au/ZnO-NFS/GOx flexible biosensors showed good repeatability for different sample concentrations. The enzymatic flexible sensor also showed good repeatability for three sample concentrations. The reproducibility data for two identical flexible sensors were found within the LoA of the Bland-Altman plot with a statistically significant p-value of 0.08 derived from the student t-test. Moreover, the flexible sensor exhibited notable repeatability, reproducibility, and remarkable stability conducive to the precise quantification of glucose. The application of this flexible wearable sensor has been validated through its utilization in human sweat samples, yielding results that align favorably with conventional methodology.

PH modulation for high capacity and long cycle life of aqueous zinc-ion batteries with β-MnO2/3D graphene-carbon nanotube hybrids as cathode

pH modulation for high capacity and long cycle life of aqueous zinc-ion batteries with β-MnO2/3D graphene-carbon nanotube hybrids as cathode

Novel carbon quantum dots enhanced carbon nanotubes-graphene hybrid nanocomposite for VOCs detection

In recent years, researchers have shown a significant interest in exploring carbon-based nanomaterials for their potential applications in sensing technologies. This study introduces the development of an innovative composite material through the integration of quantum dots with carbon nanotubes and graphene. This nanohybrid composite serves as a sensing material for detecting ethanol at room temperature. The carbon quantum dots (CQD) used in this study were synthesized through a solvothermal process and integrated with carbon nanotubes (CNT) and graphene nanoplates (GNP) to investigate the synergistic effects on the composite's structure and its sensing properties. The resulting hybrid composite was applied as a sensitive film onto the surface of a quartz crystal microbalance (QCM) sensor. The hybrid nanocomposite-based sensor demonstrated significantly enhanced sensing sensitivity. At an ethanol concentration of 500 ppm, the CQD-enhanced CNT-GNP composite exhibited approximately 10- and 15-fold higher responses compared to CNT- and GNP-coated sensors, respectively. The response/recovery times of the CQD-enhanced CNT-GNP composite sensor were approximately 2/0.5 min, respectively. The sensor maintained reasonable repeatability and good recovery. The findings highlight the remarkable synergistic effects observed in the sensing performance of carbon-based nanohybrids, demonstrating the promising potential of this approach to enhance the sensitivity of such sensors.

Enabling long cycle aluminum-sulfur batteries via structurally stable Co, N-doped graphene-CNTs covalently bonded hybrid

Al-S batteries offer advantages such as high energy density, low cost, and good safety. However, they face challenges including poor sulfur conductivity, volume expansion, and slow kinetics of polysulfides, leading to rapid capacity decay and short cycle life. Therefore, the design of materials with high conductivity, capable of anchoring polysulfides, and structurally robust is crucial for enhancing the overall performance of Al-S batteries. To address these issues, we propose the construction of a structurally stable graphene-carbon nanotubes (CNTs) covalently bonded hybrid and a three-dimensional (3D) conductive framework catalyzed by Co active sites. The porous Co, N-doped graphene-carbon nanotubes (CoN-GC) hybrid with excellent mechanical properties provides sufficient space for high sulfur loading, alleviating sulfur volume expansion. Co plays a key role in rapidly transporting electrons, adsorbing, and catalyzing aluminum polysulfides. The Al-S battery using S@CoN-GC cycles over 1500 cycles at a current density of 300 mA·g−1, maintaining a specific capacity of 315 mAh·g−1, and retains 278 mAh·g−1 after 2000 cycles. Additionally, utilizing the outstanding mechanical properties of CoN-GC, a flexible Al-S microbattery was successfully fabricated, maintaining a capacity retention of 90 % after folding 1000 times. These research findings are expected to accelerate the study of multivalent metal-sulfur batteries and their practical applications in various scenarios.

Improving the emission properties of graphene–carbon nanotube hybrid nanostructures through functionalization with BaO nanoparticles and laser treatment

This paper presents the manufacturing technology of hybrid nanostructures based on a buffer layer of reduced graphene oxide (rGO) flakes with vertical single-walled carbon nanotubes (SWCNTs) and their bundles functionalized with BaO nanoparticles. Using density functional theory (DFT) calculations, supercells of rGO/SWCNT/BaO films were constructed and the patterns of the electron work function were revealed. It has been demonstrated that the electron work function is influenced by both the mass fraction of BaO nanoparticles and the inter-tube distance. Branched carbon nanostructure was formed using a pulsed laser irradiation. Fragmentation of BaO nanoparticles on the carbon surface was achieved. It was shown that after laser treatment, Ba(NO3)2 particles up to 200 nm in size were fragmented into smaller BaO nanoparticles with sizes of a few nanometers, covering the nanotubes. The field emission current–voltage characteristics (CVCs) were measured and showed a 42-fold increase in emission current compared to the nanostructure without BaO functionalization and laser treatment. BaO-functionalized hybrid carbon nanostructures are predicted to be efficient field cathodes, with a current density of at least 2 A/cm2, for use in X-ray tubes, field emission displays, and vacuum microwave devices.

Effect of MnSO4 concentration on the electrochemical performance of β-MnO2/3D graphene-carbon nanotube hybrids cathode for aqueous zinc-ion batteries

Effect of MnSO4 concentration on the electrochemical performance of β-MnO2/3D graphene-carbon nanotube hybrids cathode for aqueous zinc-ion batteries

Welded Carbon Nanotube-Graphene Hybrids with Tunable Strain Sensing Behavior for Wide-Range Bio-Signal Monitoring.

Carbon nanotubes (CNTs) and graphene have commonly been applied as the sensitive layer of strain sensors. However, the buckling deformation of CNTs and the crack generation of graphene usually leads to an unsatisfactory strain sensing performance. In this work, we developed a universal strategy to prepare welded CNT-graphene hybrids with tunable compositions and a tunable bonding strength between components by the in situ reduction of CNT-graphene oxide (GO) hybrid by thermal annealing. The stiffness of the hybrid film could be tailored by both initial CNT/GO dosage and annealing temperature, through which its electromechanical behaviors could also be defined. The strain sensor based on the CNT-graphene hybrid could be applied to collect epidermal bio-signals by both capturing the faint skin deformation from wrist pulse and recording the large deformations from joint bending, which has great potential in health monitoring, motion sensing and human-machine interfacing.

Synthesis and applications of metal nanoparticles (Au, Ag)@C-graphene oxide and carbon nanotubes hybrid nanoarchitectures

In this work, we made an effort to use dopamine hydrochloride and the solid state method to anchor the gold and silver metallic nanoparticles over the graphene oxide-carbon nanotubes to improve the metal nanoparticles' interaction with the support materials. Because the hybrid nanoarchitectures of graphene-CNT provide enhanced electron transfer ability, which facilitates the catalytic activity more quickly and enhances the rate. Additionally, carbon nanotubes–graphene oxide-metal nanoparticles based hybrid catalyst was developed in a similar fashion. The formation of metallic nanoparticles in a size range of 3–15 nm is visible in the micrographs. These particles developed as nano-islands. The excess reductant formed as polydopamine acts as a stabilizer, and further, we utilise this polydoapmine into carbon by the calcination process. It results that carbonous materials will enhance the interaction between metal and support (CNT/GO). This leads to improved catalytic activity towards the reduction of 4-nitrophenol and catalytic decolorization of methylene blue at room temperature. The suggested technique for synthesizing metal nanoparticles over carbon nanostructures is simple and environmentally friendly.

Effects of Three-Dimensional Graphene-Carbon Nanotube Hybrid on the Mechanical Properties and Microstructure of Cement Paste.

This work experimentally studies the mechanical properties and microstructure of cementitious composites reinforced with a three-dimensional graphene-carbon nanotube (CNT) hybrid. Firstly, the graphene-CNT (GC) hybrid is dispersed in cement pastes using ultrasonication and surfactant, and then, the effect of the GC hybrid on the early hydration of the cement pastes is investigated. The experimental results show that adding the GC hybrid shortens the setting stage of cement hydration and accelerates the early hydration process. Moreover, the macro- and micro-mechanical properties of each group are evaluated. The 7- and 28-day strength of the cement pastes improves with addition of the GC hybrid. Finally, the microstructural analysis demonstrates that the GC hybrid is reasonably well distributed in cement and forms a spatial network, which could bridge the cracks and compact the cementitious matrix.

β-MnO2/three-dimensional graphene-carbon nanotube hybrids as cathode for aqueous zinc-ion battery

Aqueous zinc-ion batteries (RZIBs) are one of the favorable complementary candidates for lithium-ion batteries. The cathode material determines the whole performance. Herein, β-MnO2/3D GPE-CNTs hybrid cathode materials were fabricated by intermittent high-energy vibratory ball milling method. It delivered a higher specific discharge capacity of 313.31 mAh·g−1 and excellent cycling stability compared to the bare β-MnO2 sample. Morphological characterizations revealed that the enhanced electrochemical performance of the β-MnO2/3D GPE-CNTs hybrid was mainly attributed to the three-dimensional framework structure, large specific surface area, and good conductivity of GPE-CNT, as well as its resulting particle refinement with uniform dispersion and partial suppression of grain amorphization. This article provided a new sight of fabricating Mn-based materials/conducting carbon material hybrid for good performance cathode in RZIBs.

Island-Type Graphene-Nanotube Hybrid Structures for Flexible and Stretchable Electronics: In Silico Study.

Using the self-consistent charge density functional tight-binding (SCC-DFTB) method, we study the behavior of graphene-carbon nanotube hybrid films with island topology under axial deformation. Hybrid films are formed by AB-stacked bilayer graphene and horizontally aligned chiral single-walled carbon nanotubes (SWCNTs) with chirality indices (12,6) and 1.2 nm in diameter. In hybrid films, bilayer graphene is located above the nanotube, forming the so-called "islands" of increased carbon density, which correspond to known experimental data on the synthesis of graphene-nanotube composites. Two types of axial deformation are considered: stretching and compression. It has been established that bilayer graphene-SWCNT (12,6) hybrid films are characterized by elastic deformation both in the case of axial stretching and axial compression. At the same time, the resistance of the atomic network of bilayer graphene-SWCNT (12,6) hybrid films to failure is higher in the case of axial compression. Within the framework of the Landauer-Buttiker formalism, the current-voltage characteristics of bilayer graphene-SWCNT (12,6) hybrid films are calculated. It is shown that the slope of the current-voltage characteristic and the maximum values of the current are sensitive to the topological features of the bilayer graphene in the composition of graphene-SWCNT (12,6) hybrid film. Based on the obtained results, the prospects for the use of island-type graphene-nanotube films in flexible and stretchable electronic devices are predicted.

Hydrogen storage using novel graphene-carbon nanotube hybrid

Hydrogen storage is an active area of research particularly due to urgent requirements for green energy technologies. In this paper, we study the storage of hydrogen gas molecules in terms of physical adsorption on a carbon-based nanomaterial, i.e., a novel graphene-carbon nanotube hybrid. The novel carbon nanostructures were prepared from pristine nanotubes and graphene sheets using molecular dynamics simulations and hydrogen storage quantified in terms of gravimetric capacity was simulated using grand canonical Monte Carlo Simulations. We found the highest storage capacity of 5.90 wt% at room temperature and 100 bar with high reversibility of operation.

Carbon-based nano lattice hybrid structures: Mechanical and thermal properties

The hybridization of carbon-based nanomaterials (i.e CNTs, fullerenes and graphene) via chemical bonding provides a preferable way to maximize and control their exceptional properties. In line with this understanding, in this study, the design and analysis of new porous graphene-carbon nanotube (G-CNT) hybrid structures obtained by organizing graphene nanoribbons around the CNT units in three different geometric patterns (i.e. square, hexagon, diamond) is presented. With this motivation, after examining the thermodynamic feasibility of the nanostructures , the mechanical and thermal properties are examined by considering the effects of different pattern geometries through classical molecular dynamics simulations. In addition, in order to increase the compressive strength and energy absorption capacity of G-CNT structures, fullerenes are employed as filler units within the cells. Simulation results show that the proposed G-CNT structures have remarkable thermal and mechanical characteristics, which can be modified by the geometric arrangement of CNTs and graphene nanoribbons as well as by the filler agents. Controllability of the thermal conductivity and mechanical strength is promising for different application fields where their ultra-lightweight plays an eminent role. • Novel ultra-light hybrid nanostructures with remarkable thermal and mechanical properties are presented. • Controllable thermal and mechanical properties can be achieved by different geometric arrangements. • A significant enhancement on the compression behavior is demonstrated by the utilization of fullerenes. • A foam-like compressive response with remarkable energy absorbing capacity is observed. • Wide range of application fields including thermal, mechanical and hydrogen storage are targeted.

Polydopamine and Mercapto Functionalized 3D Carbon Nano-Material Hybrids Synergistically Modifying Aramid Fibers for Adhesion Improvement.

In order to solve the problem of poor interfacial adhesion between aramid fibers and a rubber matrix, an efficient and mild modification method was proposed via polydopamine and mercapto functionalized graphene oxide (GO) and carbon nanotube (CNTs) hybrids synergistically modifying aramid fibers. GO and CNTs were firstly stacked and assembled into unique 3D GO-CNTs hybrids through π-π conjugation. Then, the mercapto functionalization of the assembled 3D GO-CNTs hybrids was realized via the dehydration condensation reaction between the hydroxyls of GO and the silanol groups of coupling agent. Finally, the mercapto functionalized 3D GO-CNTs hybrids were grafted onto the aramid fibers, which were pre-modified by polydopamine through the Michael addition reaction mechanism. The surface morphology and chemical structures of GO-CNTs hybrids and fibers and the interfacial adhesion strength between fibers and rubber matrix were investigated. The results showed that the modification method had brought about great changes in the surface structure of fibers but not generated any damage traces. More importantly, this modification method could improve the interfacial strength by 110.95%, and the reason was not only the reactivity of functional groups but also that the 3D GO-CNTs hybrids with excellent mechanical properties could effectively share interfacial stress. The method proposed in this paper was universal and had the potential to be applied to other high-performance fiber-reinforced composites.

A tight-binding study of the electron transport through single-walled carbon nanotube-graphene hybrid nanostructures.

Hybrid carbon nanostructures based on the sp2 hybridized allotropes of carbon, such as graphene and single-walled carbon nanotubes (SWCNTs), hold vast potential for applications in electronics of various forms. Electronic properties of such hybrid structures are modified due to the interaction between atoms of the components, which can be utilized to tailor the properties of the hybrid structures to suite the application. In this study, we have explored charge (electron) transport through the hybrid structures of single-layer graphene (SLG) and SWCNTs (both metallic and semiconducting) using the nonequilibrium Green's function formalism within the framework of tight-binding density functional theory. Our calculations show that the electronic transport in hybrid nanostructures is affected by the interactions between SWCNT and SLG in comparison to the individual components. The changes in the electronic structure and the transport properties with increasing interaction in hybrids (captured by decreasing the separation between SWCNT and SLG) are discussed, and it is demonstrated from this analysis that the hybrids with semiconducting SWCNTs and metallic SWCNTs show different behavior in the low bias regime while they show similar behavior at higher biases. The difference in the transport properties of hybrids with semiconducting and metallic SWCNTs is explained in terms of changes in the electronic structure, the local density of states, and the energy dispersion for electrons due to the interaction between atoms of the two components.

Investigation of hydrogen production from sodium borohydride by carbon nanotube‐graphenesupportedPdRubimetallic catalyst forPEMfuel cell application

In this study, hydrogen (H2) generation from the hydrolysis of sodium borohydride (NaBH4) catalyzed by bimetallic Palladium-Ruthenium (PdRu) supported on multiwalled carbon nanotube-graphene (MWCNT-GNP) hybrid material is investigated. The effect of various parameters such as temperature, NaBH4 concentration, and catalyst loading and effect of base concentration are examined to observed optimum operating conditions. Experimental results show that the PdRu/MWCNT-GNP bimetallic catalyst has high catalytic activity on NaBH4 hydrolysis reaction. It has been found that PdRu/MWCNT-GNP catalyst shows low activation energy of 22.33 kJ/mol for hydrolysis reaction of NaBH4. The PdRu/MWCNT-GNP catalyst also exhibits H2 generation rate of 79.2 mmol/min·gcat at 45°C. It shows good cycle stability in the catalyst reusability test and retained 89% of its initial catalytic activity after fifth use. The high catalytic activity of the PdRu/MWCNT-GNP catalyst makes it promising in H2 generation from NaBH4 hydrolysis for commercial proton exchange membrane fuel cell (PEMFC) applications.

Modeling low and high temperature controls in the growth of graphene-CNT hybrids by PECVD: an interplay between process and plasma parameters

The effect of process parameters such as the pressure, power, and substrate bias on the dimensions of CNT, graphene, and graphene-CNT hybrids in the low and high temperature regime is described by a multispecies plasma-assisted and catalyst-aided phenomenological growth model of graphene-carbon nanotube (CNT) hybrids. An interplay established in the present work between the process and plasma parameters (such as the electron density and temperature, and radical flux) characterizes the process parameters effects. It is found that this interplay is remarkably different at low and high temperature owing to the different processes that dominate during the growth in these temperature regimes.

Highly selective carbon capture by novel graphene-carbon nanotube hybrids

ABSTRACT Numerous nanomaterials with novel architectural segments are being currently designed to achieve high CO2 capture selectivity and adsorption. Here, we demonstrate molecular dynamics simulations of a range of newly modelled graphene-CNT hybrids in CO2/N2 and CO2/H2O mixtures. The hybrids possess novel pseudo-triangular voids formed by embedding a graphene sheet in between multiple CNTs along with the cylindrical CNT pores. The pseudo-triangular voids formed with considerably larger diameter CNTs at an industrially relevant CO2/N2 proportion reveals extremely high CO2 capture selectivity of 0.957 compared to 0.692 by original CNT pores, resulting in an overall enhanced hybrid interior selectivity of 0.762. Simulations of these systems with a rise in temperature from 200 to 600 K revealed significant desorption, however, for an initial rise from 200 to 400 K, the triangular voids offered higher resistance to desorption compared to the CNT pores. The hybrids constructed with small diameter CNTs always depicted the overall selectivity values close to 1, independent of CO2/N2 proportion.