Graphene-based Metal Research Articles

Unveiling the molecular symphony - A DFT exploration of structure, electronic dynamics, and excited state electron transfer in D-π-A systems, enhanced by TeO2@GQD multi-junctions for solar energy conversion in DSSC

Graphene and graphene-derived materials have sparked a lot of interest because of their unique physico-chemical features, that have positioned graphene as a promising material for future opto-electronics, and energy-harvesting devices. Graphene possesses outstanding mechanical characteristics and chemical inertness, as well as great mobility and optical transparency. Single-layer graphene has a high optical transmissivity that allows it to pass through a wide variety of light wavelengths, making it a popular material for optically conducting windows. Graphene-based metal and metal oxide nanocomposites require substantial investigations to understand the fundamental interactions between nanostructures and the graphene surface in DSSC, for understanding the characteristic features of such nanocomposites. In the present study different donor-π-acceptor, systems were used, which are different in the type of the π –spacer units only. This D-π-A system was then decorated on a (TiO2)9 semiconductor leading to shifting of the absorption wavelength, the absorbed wavelength was further shifted upon interaction with tellurium–oxide@graphene, thereby exploring its application in solar energy harvesting devices. The result of such substitution was assessed in terms of various parameters such as highest occupied molecular orbital (HOMO), least unoccupied molecular orbital (LUMO), energy gap (Egap), maximum wavelength (λmax), the free energy of electron injection efficiency (ΔGinject), open-circuit voltage (Voc), reorganization energy (Δreorg), etc by the DFT method with Gaussian 09 set of codes. The study can prove beneficial for understanding the mechanism of high optical absorption over a broad spectrum in such multijunction systems, the feature which makes them promising materials for efficient optical, electronic, and light-harvesting devices.

Graphene-based metal/metal oxide nanocomposites as potential antibacterial agents: a mini-review.

Antimicrobial resistance (AMR) is a rising issue worldwide, which is increasing prolonged illness and mortality rates in the population. Similarly, bacteria have generated multidrug resistance (MDR) by developing various mechanisms to cope with existing antibiotics and therefore, there is a need to develop new antibacterial and antimicrobial agents. Biocompatible nanomaterials like graphene and its derivatives, graphene oxide (GO), and reduced graphene oxide (rGO) loaded with metal/metal oxide nanoparticles have been explored as potential antibacterial agents. It is observed that nanocomposites of GO/rGO and metal/metal oxide nanoparticles can result in the synthesis of less toxic, more stable, controlled size, uniformly distributed, and cost-effective nanomaterials compared to pure metal nanoparticles. Antibacterial studies of these nanocomposites show their considerable potential as antibacterial and antimicrobial agents, however, issues like the mechanism of antimicrobial action and their cytotoxicity need to be explored in detail. This review highlights a comparative analysis of graphene-based metal and metal oxide nanoparticles as potential antibacterial agents against AMR and MDR.

Bioinspired graphene-based metal oxide nanocomposites for photocatalytic and electrochemical performances: an updated review.

Considering the rapidly increasing population, the development of new resources, skills, and devices that can provide safe potable water and clean energy remains one of the vital research topics for the scientific community. Owing to this, scientific community discovered such material for tackle this issue of environment benign, the new materials with graphene functionalized derivatives show significant advantages for application in multifunctional catalysis and energy storage systems. Herein, we highlight the recent methods reported for the preparation of graphene-based materials by focusing on the following aspects: (i) transformation of graphite/graphite oxide into graphene/graphene oxide via exfoliation and reduction; (ii) bioinspired fabrication or modification of graphene with various metal oxides and its applications in photocatalysis and storage systems. The kinetics of photocatalysis and the effects of different parameters (such as photocatalyst dose and charge-carrier scavengers) for the optimization of the degradation efficiency of organic dyes, phenol compounds, antibiotics, and pharmaceutical drugs are discussed. Further, we present a brief introduction on different graphene-based metal oxides and a systematic survey of the recently published research literature on electrode materials for lithium-ion batteries (LIBs), supercapacitors, and fuel cells. Subsequently, the power density, stability, pseudocapacitance charge/discharge process, capacity and electrochemical reaction mechanisms of intercalation, and conversion- and alloying-type anode materials are summarized in detail. Furthermore, we thoroughly distinguish the intrinsic differences among underpotential deposition, intercalation, and conventional pseudocapacitance of electrode materials. This review offers a meaningful reference for the construction and fabrication of graphene-based metal oxides as effective photocatalysts for photodegradation study and high-performance optimization of anode materials for LIBs, supercapacitors, and fuel cells.

Two-dimensional layered MoSe2/graphene oxide (GO) nanohybrid coupled with the specific immune-recognition element for rapid detection of endosulfan

Endosulfan (En) is an organochlorine biocide (OCB), that ends up in the environment due to the enzymatic and microsomal activity even though it is not accumulated in living tissue. Endosulfan acts as an organic micro-pollutant which disrupts land as well as aquatic ecosystem. In the present study, we chemically modified endosulfan and conjugated it with a carrier protein to produce an immune response. The generated antibodies were tested for specificity against En, and characterized before further use. Transition Metal Chalcogenides (TMC) showed excellent optoelectrical potential due to its direct bandgap and distinct physical as well as chemical characteristics. Herein, we synthesized a novel nanohybrid using MoSe2 in combination with graphene oxide (GO) and characterized thoroughly. This was similar to graphene-based metal chalcogenides which were further used in this study to fabricate biosensor for the sensitive detection of En. The in-house developed antibodies (En-Ab) were coupled with the nanohybrid to make MoSe2/GO/En-Ab electrode. Fabricated electrode was tested for electrochemical parameters using differential pulse voltammetry (DPV). Working efficiency of the fabricated electrode i.e., limit of detection (LOD), was found to be 7.45 ppt. In conclusion, we hypothesized that the synthesized TMC nanohybrids could be employed for biosensing of endosulfan, and can likely be developed to test field samples.

Effects of Graphene-Based Metal Composite and Urea on Seed Germination and Performance of Berberis chitria Buch.-Ham. ex Lindl.

Being an important source of berberine, Berberis chitria Buch.-Ham. ex Lindl. (Berberidaceae) has high demand in pharmaceutical industries. Its populations are diminishing due to overexploitation, habitat loss, slow-growing nature, and climate change. It is important to develop propagation protocols to sustain its natural populations and ensure its survival in the future. Fertilizers play an essential role in the yield and productivity of different crops. Among others, urea is the most abundantly used fertilizer in crops. Its effects on the yield and survival of medicinal plants are poorly studied. However, it is known that applying urea for a long time affects the soil negatively. Due to these negative effects, alternative fertilizers such as graphene-based metal composite (GMC) are being tested for their efficiency. In the present study, for the first time, we tested the effects of urea and GMC on the germination and performance of B. chitria. GMC showed maximum germination at 30ppm (75%) and urea at 15ppm (79%). Findings reveal non-significant effects of GMC and urea on germination and performance of B. chitria, suggesting the use of GMC as an alternative fertilizer.

Unraveling the catalytic ozonation mechanisms with ZnO decorated rGO composite: Structural properties and reactive oxygen species evolution

In this study, a series of ZnO decorated rGO composites (x%ZnO@rGO) were successfully synthesized by the alkaline hydrothermal method. The crystal structure, surface morphology, and chemical property of x%ZnO@rGO were characterized by BET, XRD, FT-IR, SEM, TEM, and XPS, respectively. Amongst, 15%ZnO@rGO composite exhibited superior catalytic ozonation performance with an improvement of 68.4% on atrazine (ATZ) degradation efficiency (3 mins), more than 7.8 times of the pseudo-first-order rate constant compared with single O3. The roles of O3 and reactive oxygen species (ROSs) were confirmed and compared by the quenching and low-concentration probe experiments, suggesting that O3 and OH played an important role for ATZ degradation, while the function of 1O2 and O2− can be neglected both in single O3 and 15%ZnO@rGO/O3 system, which was contrary to that of the quenching experiments. Besides, the exposures of O3 and ROSs showed that 15%ZnO@rGO can facilitate the transformation process of 1O2 to OH in different conditions, and largely enhance the exposure of OH. The roles of electrons, Lewis acid sites, and oxygen vacancies of 15%ZnO@rGO in catalytic ozonation were identified as well, which offered us a new perspective to design a high-efficiency catalyst and may promote graphene-based metal oxides for practical pollutant elimination.

Graphene-Based Metal Oxide Composites for Lithium-ion Batteries

Graphene-Based Metal Oxide Composites for Lithium-ion Batteries

Green synthesis of graphene-based metal nanocomposite for electro and photocatalytic activity; recent advancement and future prospective

The presence of pollutants in waste water is a demanding problem for human health. Investigations have been allocated to study the adsorptive behavior of graphene-based materials to remove pollutants from wastewater. Graphene (GO) due to its hydrophilicity, high surface area, and oxygenated functional groups, is an effective adsorbent for the removal of dyes and heavy metals from water. The disclosure of green synthesis opened the gateway for the economic productive methods. This article reveals the fabrication of graphene-based composite from aloe vera extract using a green method. The proposed mechanism of GO reduction via plant extract has also been mentioned in this work. The mechanism associated with the removal of dyes and heavy metals by graphene-based adsorbents and absorptive capacities of heavy metals has been discussed in detail. The toxicity of heavy metals has also been mentioned here. The Polyaromatic resonating system of GO develops significant π-π interactions with dyes whose base form comprises principally oxygenated functional groups. This review article illustrates a literature survey by classifying graphene-based composite with a global market value from 2010 to 2025 and also depicts a comparative study between green and chemical reduction methods. It presents state of art for the fabrication of GO with novel adsorbents such as metal, polymer, metal oxide and elastomers-based nanocomposites for the removal of pollutants. The current progress in the applications of graphene-based composites in antimicrobial, anticancer, drug delivery, and removal of dyes with photocatalytic efficacy of 73% is explored in this work. It gives a coherent overview of the green synthesis of graphene-based composite, various prospective for the fabrication of graphene, and their biotoxicity.

Visible light emission enhancement from a graphene-based metal Fabry-Pérot cavity.

The high saturation current density and ultrafast heating modulation of graphene makes it a competitive candidate for future thermal emission source. However, the low emissivity and easy oxidation under high temperature in air limit graphene application in the spectral range from the visible to near infrared. Here, we report a visible graphene thermal emitter based on the metal Fabry-Pérot (FP) cavity, which can greatly enhance the emissivity of graphene at wavelength around 637 nm and protect graphene from oxidation. We investigate the temperature characteristics of the emitter, and find the temperature of hot electrons in graphene is much higher than that of graphene lattice. Moreover, we also demonstrate the wavelength and intensity of graphene emission could be controlled by tuning the dielectric thickness between two gold layers. These results are helpful in the development of advanced graphene electro-thermal emission controlling application.

Sub-Second Joule-Heated RuO2-Decorated Nitrogen- and Sulfur-Doped Graphene Fibers for Flexible Fiber-type Supercapacitors.

Graphene-based fiber-shaped supercapacitors (FSSCs) have received considerable attention as potential wearable energy storage devices owing to their simple operating mechanism, flexibility, and long-term stability. To date, energy storage capacities of supercapacitors have been significantly improved via strategies such as heteroatom doping and the incorporation of pseudocapacitive metal oxides. Herein, we develop a novel and scalable direct-hybridization method that combines heteroatom doping and metal oxide hybridization for the fabrication of high-performance FSSCs. Using porous and highly conductive nitrogen and sulfur co-doped graphene fibers (NS-GFs) as self-heating units, we successfully convert ruthenium hydroxide anchored to the surface into ruthenium oxide nanoparticles after programmed sub-second electrothermal annealing without structural damage of the fibers. The resulting fibers show an increased gravimetric capacitance of 68.88 F g-1 compared to that of the pristine NS-GF (8.32 F g-1), excellent cyclic stability maintaining 96.67% of the initial capacitance after 20 000 continuous charging/discharging cycles, and good mechanical flexibility. The findings of this work advocate a successful Joule heating strategy for preparing high-performance graphene-based metal oxide hybrid FSSCs for use in energy storage applications.

Effect of morphology-induced interfacial defects on band location and enhanced photocatalytic dye degradation activity of TiO2/Graphene aerogel

Two different morphologies of TiO2, namely nanorods (NRs) and ultrathin nanowires (uNWs), have been grown on graphene aerogel (GA), denoted as TiO2 NR@GA and TiO2 uNW@GA, to investigate the variation of band-gap structure and the generation of multiple intermediate energy levels caused by heterogeneous interfaces. In comparison to TiO2 NRs and nanowires (NWs), TiO2 in both composites shows a much smaller size or diameter due to the graphene-confined growth during the hydrothermal process. The positions of band edges and the distributions of defect energy levels have been measured and calculated. The band gap of TiO2 in TiO2 uNW@GA is more extensively modified than that in TiO2 NR@GA as a result of the ultrathin (8–10 nm) diameter of TiO2 NWs, a larger interfacial region, and blurred boundaries between interfacial defects and bulk defects. The dramatically modified band gap facilitates the separation and transmission of photoinduced electrons and holes. Thus, TiO2 uNW@GA with a bicrystalline phase (anatase:bronze, 1:3) exhibits higher photocatalytic activity than anatase TiO2 NR@GA. This study establishes a foundation for improving photocatalytic performance by engineering interfacial defects of graphene-based metal oxides.

Phenylamine-Functionalized Graphene–Copper Composites with High Thermal Conductivity: Implications for Thermal Dissipation

Developing highly efficient thermal management techniques is crucial in order to achieve the best performance of electronic equipment. Here, a delocalized conjugated system was established by the conjugation of sp2 orbitals in phenylamine groups and a delocalized big π bond in graphene to construct an electron thermal conduction route. Then, the abundant π electrons in graphene can be transferred to the adjacent copper unimpededly, leading to a remarkable thermal conductivity. These results demonstrate that the copper substrate deposited with phenylamine-functionalized graphene (PA–Gr–Cu) shows a high thermal conductivity of 506 W m–1 k–1, which is 30.8 and 44.2% higher than those of the pristine graphene–copper composite (Gr–Cu) and copper (Cu), respectively. Placed on a heat source heated from 30 to 210 °C within 5 min, the top surface temperature of PA–Gr–Cu increases to 198 °C rapidly, whereas those of Gr–Cu and Cu only increase gently to 88 and 59 °C. This work demonstrates that phenylamine with a pair of lone electrons in the N atom shows superiority as an intermediate molecule to link graphene and copper to establish a delocalized conjugated system. This innovation provides another solution to establish a conjugated structure between graphene and copper to construct an electron thermal conduction route with remarkable thermal conduction properties and will promote the research on the electron thermal conduction route for graphene-based metal matrix composites in the application of thermal dissipation.

In situ observation of metal ion interactions with graphene oxide layers: From the growth of metal hydroxide to metal oxide formation

The interactions between metal ions and graphene oxide (GO) nanosheets were investigated by in situ two-dimensional grazing incidence X-ray diffraction (GIXRD). We found that metal cations (Mn2+, Co2+, Cu2+, Fe3+) and GO can self-assemble into a hydroxide/GO superlattice by drop-casting a metal chloride and GO solution due to the electrostatic interactions between the positively charged hydroxide and the negatively charged GO nanosheets and the interlayer spacing of the superlattice can be controlled by the cation species. Moreover, based on this superlattice template, graphene-based metal oxide nanosheets can be facilely obtained by subsequent annealing. The growth mechanism and structural evolution of the GO/cation systems can be described in four stages: (1) hydrated cation intercalation of the GO interlayer in an aqueous solution; (2) metal hydroxide growth between the GO layers during annealing, with the formation of a superlattice structure at approximately 250 °C; (3) metal oxide nucleation between the reduced GO (rGO) interlayers with increasing temperature; and (4) complete graphene layer decomposition at a temperature of 600 °C, along with metal oxide nanosheet formation. This work gives a new perspective for understanding the interactions between and growth behaviour of metal cations and GO.

Frequency-dependent ultrasensitive terahertz dynamic modulation at the Dirac point on graphene-based metal and all-dielectric metamaterials

The development of terahertz (THz) technology is creating a demand for devices that can modulate THz beams. Here, we report the design and characterization of three THz modulators. One uses graphene and a metal-microstructure-integrated metamaterial, another uses a bare graphene film, and the third uses graphene-based all-dielectric metamaterials. Ultrasensitive dynamic THz modulation is achieved by shifting the quasi-Fermi level between the Dirac point, the conduction band, and the valence of graphene via continuous-wave optical illumination or bias voltages. When the Fermi level is close to the Dirac point, the modulation is ultrasensitive to the external stimuli. The modulation depth can reach the maximum value of 346% in the current public publication, breaking through the bottleneck of modulation inefficiency, and is expected to realize practical applications for the first time. For the range 0.2–2 THz, the modulation depth initially increases, then decreases. These results will enable potential designs for ultrasensitive THz devices.

Swift isotropic heat transport of 3D graphene platform-based metal-graphene composites

Despite the remarkable thermal properties of graphene, the heat transport along the z-axis is intrinsically limited by the van der Waals interactions, leading to thermal anisotropy in multilayered graphene (or graphite) and its composites. Herein, we report a graphene foam (GF) with three-dimensional (3D) pore structure-based metal composites with excellent isotropic thermal conductivity and fast heat transfer performance. The 3D periodic structure of the GF–copper composites composed of high-quality multilayer graphene and copper was formed via a chemical vapor deposition (CVD) and a spark plasma sintering (SPS) process. The high-quality graphene layers in GF were well-bonded to copper, forming a clear interface without voids in the consolidated composites. Owing to the uniform 3D interconnection of graphene layer in the GF, in spite of less than 1 vol% carbon in the copper matrix, the GF–copper composites showed high isotropic thermal conductivity, which was higher by about 11 and 6% for in-plane and through-plane, respectively, than those of the bulk copper (∼400 W m−1 K−1). The superior performance of the 3D graphene-based metal–carbon composites offers remarkable opportunities in thermal management for advanced electronic and optoelectronic devices requiring high power density and efficiency.

New construction of electron thermal conductive route for high-efficient heat dissipation of graphene/Cu composite

High-efficient heat dissipation is essential to maintain the best performance of the electron devices. A new electron thermal conductive route is first proposed and constructed for the graphene metal matrix composites in this work. Functionalization of graphene with conjugated 4-ethynylaniline (FGr) and deposition of FGr and Cu2+ ions onto the copper surface by pulsed-current co-electrodeposition are successively employed to prepare the FGr/Cu composite. The resulting thermal diffusivity of FGr/Cu is high as 1.444 cm2 s−1 at 100 °C, which is corresponding to the thermal conductivity of 497 W m−1 K−1 and higher than the reported values via single phonon thermal conductive route. FGr/Cu can maintain a superior and stable thermal conductive property at high temperature with a multiple of 1.61 and 1.31 at 100 °C and 150 °C compared to the Cu, respectively. The delocalized conjugated π bond in the graphene/Cu interface is successfully established through the bridging of graphene and metal with conjugated organic molecule possessing p orbits, which leads to the construction of a new electron thermal conductive route. This innovation presents an entirely new direction to develop graphene-based metal matrix composite with high-efficient heat dissipation.

Graphene-based metal matrix nanocomposites: Recent development and challenges

This articles reviews till-date available literature on metal matrix composites reinforced with graphene, CNT and other carbonaceous materials. The article has a special focus on the mechanical, tribological and challenges associated with the fabrication of nanocomposites. Simultaneously, it reviews the synthesis, strengthening mechanism and applications of graphene along with research gap associated with graphene metal matrix nanocomposites (GMMNC). Carbonaceous nanofillers, e.g. Graphene, are known to have extraordinary mechanical, thermal and electrical properties along with multifaceted characteristics. These materials have the potential to become an ideal material in numerous application which requires reinforcement. Graphene nanoplatelets (GNP) suffers various challenges starting from its synthesis to the uniform distribution within the matrix material. Our concern is to give details on the challenges associated with graphene and metal matrix composites along with the solution so that new research can be done at its ease. Section 1 of the article gives a detailed analysis of various carbonaceous reinforcement materials. Preparation, processing and dispersion technique for graphene and composite material is given in section 2. Section 3 of the article deals with different matrix material used in MMNC along with the properties and challenges associated with it in tabulated form. Strengthening mechanism used for the enhancement of mechanical properties of composites is described in section 4, whereas, Section 5 deals with the applications and Research gap.

Optimisation of NiO electrodeposition on 3D graphene electrode for electrochemical energy storage using response surface methodology

In this study, NiO was electrodeposited on a 3D graphene electrode to produce a nanocomposite with enhanced electrochemical properties. The electrodeposition process parameters such as electrolyte concentration, deposition time, and deposition potential were statistically optimised using response surface methodology. The statistical analysis showed that the optimal electrodeposition conditions to be 0.3 M, 10 min, and -1.2 V for electrolyte concentration, deposition time, and deposition potential, respectively. Furthermore, the predicted model and experimental results for the specific capacity of G-NiO were determined to be 240.91 C/g and 240.58 C/g at 3 mV/s. The results show that the electrochemical deposition technique can be employed as a fast and reliable synthesis route to develop graphene-based metal oxide nanocomposites. The structural and morphological properties were determined by XRD and FESEM studies. The electrochemical measurements revealed the excellent electrochemical performance of 3D graphene NiO composite (G-NiO) for energy storage applications.

Cadmium oxide nanoparticles/graphene composite: synthesis, theoretical insights into reactivity and adsorption study.

Graphene-based metal oxide nanocomposites are interesting and promising kinds of nanocomposites due to their large specific area, fast kinetics, and specific affinity towards heavy metal contaminants. In this work, a facile and cost-effective route was used to synthesize CdO nanoparticles (CdO NPs) and graphene-based CdO nanocomposite (G–CdO). The prepared nanomaterials were characterized and explored for lead removal from water. Both CdO NPs and G–CdO composite exhibited excellent sorption capacity of 427 and 398 mg g−1, respectively, at pH 4.8 and T = 298 K, which was superior to individual graphene and many other adsorbents. The results indicated that the recovered nanomaterials endure 4 times recyclability retaining up to 89% lead uptake efficiency. To complement the experimental study, DFT calculations were performed to investigate the stability of the formed G–CdO composite compared to CdO NPs; the reactivity of G–CdO compared to plain graphene as well as the interaction insights between graphene and CdO clusters were studied using natural-bond-orbital (NBO), electron-localization-function (ELF) and reduced-density-gradient (RDG) analyses.

An Overview on Graphene-Metal Oxide Semiconductor Nanocomposite: A Promising Platform for Visible Light Photocatalytic Activity for the Treatment of Various Pollutants in Aqueous Medium.

Graphene is one of the most favorite materials for materials science research owing to its distinctive chemical and physical properties, such as superior conductivity, extremely larger specific surface area, and good mechanical/chemical stability with the flexible monolayer structure. Graphene is considered as a supreme matrix and electron arbitrator of semiconductor nanoparticles for environmental pollution remediation. The present review looks at the recent progress on the graphene-based metal oxide and ternary composites for photocatalysis application, especially for the application of the environmental remediation. The challenges and perspectives of emerging graphene-based metal oxide nanocomposites for photocatalysis are also discussed.