Papers by Keyword: Graphene

Abstract: Silicon carbide (SiC) is a promising wide-bandgap semiconductor for advanced quantum technologies. Yet, despite progress in bulk and epitaxial growth, a reliable SiC-on-insulator platform remains lacking. Remote epitaxy, mediated by a 2D interlayer, offers a potential pathway to transferable SiC thin films and substrate reuse. In this work, we examine remote epitaxial growth of SiC on epitaxial graphene. We first evaluate the stability of graphene under SiC growth conditions and find that it degrades significantly at the required high temperatures, primarily due to hydrogen and silane etching. With the conditions yielding the highest-quality SiC epitaxial layer; graphene migrates above the SiC rather than remaining at the interface, demonstrating that true remote epitaxy is not achieved. These results highlight the fundamental challenges of SiC remote epitaxy on graphene and point toward critical directions for future exploration.

Abstract: In this study, we synthesize the nanocomposites of Fe₃O₄/graphene using an electrochemical exfoliation followed by thermal treatment. The morphology and bonding structure of the prepared samples have been characterized by scanning electron microscopy (SEM) and X-ray diffractometry (XRD). The photo-characteristic aspects of the prepared samples have been indicated by ultraviolet-visible diffuse reflection spectroscopy (DRS). The photocatalytic performance of Fe₃O₄/graphene demonstrated that it is an effective photocatalyst for methylene blue (MB) dye decomposition through illumination by a solar simulator. The results showed that after 10 minutes of electrooxidation/photocatalytic treatment in the presence of 1000 mg/L of the nanocomposite, dye degradation exceeded 70%, compared to only 29% with electrooxidation alone. Furthermore, after 60 minutes, degradation reached over 95% with the nanocomposite, compared to 75% for electrooxidation alone. Different MB concentrations and percentage photocatalyst loadings have been investigated. Furthermore, the results showed that as the amount of catalyst increased, the decomposition of MB enhanced. The results showed that the prepared nanocomposites had good photocatalytic activity towards water splitting and photodecomposition of MB.

Abstract: Thermoelectric materials are valued for their ability to convert waste heat into electrical energy. Antimonene nanosheets (AnNS) have recently emerged as a promising thermoelectric material due to their unique two-dimensional structure. However, developing efficient and scalable methods for preparing AnNS-based thermoelectric composites with improved performance remains challenging. In this study, we developed an efficient and environmentally friendly method for preparing antimonene nanosheet (AnNS)/graphene platelets (GNPs) composites using ultrasonic dispersion in an ethanol-based system, followed by thin film fabrication via cold-pressing. Atomic Force Microscopy (AFM) was used to characterize the microstructure and thickness of the nanosheets, while Scanning Electron Microscopy (SEM) images revealed the contact structures at different GNP concentrations. The characterization of the thermoelectric composites involved techniques such as X-ray diffraction (XRD) and Raman spectroscopy. The thermoelectric (TE) performance of the composites was systematically evaluated across different GNP volume fractions. Composites containing 1 vol% GNPs exhibited the highest electrical conductivity, measured at 2158.22 ± 25.5 S/cm, along with a Seebeck coefficient of 27.17 ± 0.15 µV/K, yielding a power factor of 159.34 ± 5.6 µW/m·K². When these composite films were integrated into a thermoelectric generator (TEG) and exposed to a human body temperature gradient of 11 °C, they produced a continuous voltage of 43.62 mV and a current of 0.21925 µA, yielding an output power of 9.56 nW. Additionally, the corrosion resistance of the composites was assessed, revealing that the 1 vol% GNPs composite exhibited superior performance compared to other compositions.

Abstract: The work aimed to obtain zirconium diboride ZrB₂ and silicon carbide SiC based ultra-high temperature ceramics, which have improved properties due to the unique morphology of starting ultrafine homogeneous composite powders. Such properties make it possible to use the product as thermal protection materials of hypersonic aircraft. The novelty of the research is the use of methods that lead to relevant selection of sintering additives/dopants and obtaining a fine microstructure, as well as the combined effect of these factors. Boron carbide B₄C, graphite powder, carbon black, and graphene structures are used as sintering additives. ZrB₂ nano powders with different stoichiometry and graphene nanostructural inclusions are produced and then their nanopowder ceramic composites with SiC are made by vacuum hot-pressing method at 1700–1750°C. The following key properties of powders and ceramics were determined: morphology, elemental and phase compositions, particle size distribution, relative density, hardness, and flexural strength and modulus.

Abstract: Graphene is an interesting 2D material to research and develop. The applications of graphene are certainly many and promising, one of which is as a semiconductor device. However, in its development as a semiconductor device, this material still has limitations such as having a zero energy band gap. Many methods and research continue to be carried out to overcome these limitations. One method of researching graphene material for its development is to modify the structure of the material. Modifications that can be made are by providing void defects and substitutions in the structure. Through material computational studies with Density Functional Theory (DFT) based calculations, this research analyzes the impact of the presence of Nitrogen with a pyridinic configuration model on modified graphene sheets. Calculations were carried out on a graphene sheet with a supercell size of 4 x 4 x 1, with the Perdew-Burke-Ernzerhof (PBE) function used as Generalized Gradient Approximation (GGA) to complete the correlation and exchange functions. The results obtained successfully provide information that there is an open energy gap and there is information regarding changes in the properties of graphene material to become a magnetic material. The research carried out has an impact on the further development of graphene.

Abstract: This study presents a novel contribution to the research of graphene-based electro-optic modulators. In this paper, we numerically demonstrate an ultra-compact and efficient graphene modulator based on metal-nanoribbon integrated hybrid plasmonic waveguide. Benefiting from the good in-plane mode polarization matching and strong hybrid surface plasmon polariton and grapheme interaction, the 10 μm-length modulator can achieve good modulation performance with a wide modulation bandwidth of 41.3 GHz and a low energy consumption of 101 fJ/bit at 1.55 μm. These compact and energy-efficient optical modulators may have broad application prospects in the future optical communication systems.

Abstract: Graphene, with its hexagonal arrangement of carbon atoms, exhibits high electrical conductivity and charge carrier mobility due to its zero bandgap. However, its semi-metallic nature limits its application in semiconductor devices. This study explores the modification of graphene’s electronic and magnetic properties by introducing defects and nitrogen substitutions in its crystal structure using spin-polarized density functional theory (DFT). Structural relaxation showed variations in supercell expansion with increasing nitrogen doping. The DFT results revealed that nitrogen substitution in a 4 × 4 × 1 graphene supercell opened an energy gap, and converting graphene into a p-type semiconductor. Additionally, nitrogen doping induced a magnetic transition, with pyridinic and combined pyrolic-pyridinic configurations showing notable spin polarization. These findings highlight the potential of nitrogen-doped graphene for magnetic and electronic applications.

Abstract: This study explores the utility of reduced graphene oxide (rGO) as a support material for gold nanoparticles (AuNPs) synthesized via an economically efficient and environmentally friendly electrochemical deposition method conducted at room temperature. Employing a chronoamperometry (CA) method, we successfully synthesize AuNPs in aqueous solutions without additional stabilizing agents. We investigate the influence of substrate and electrodeposition duration on the growth of AuNPs, on indium tin oxide glass substrates and rGO, with electrodeposition durations for comparison. This research highlights the straightforward and rapid one-step synthesis of AuNPs in an aqueous medium and explores the correlation between Au particle size and electrocatalytic performance. We evaluate the electrochemical performance of rGO-supported AuNPs in the context of methanol oxidation reaction (MOR) using cyclic voltammetry in an aqueous medium with an alkaline electrolyte. Notably, AuNPs supported by rGO, featuring an average particle size of 46 nm, exhibit superior electrochemical performance compared to their counterparts with an average particle size of 165 nm when employed as catalysts for the MOR. This superior performance is characterized by a 15 mV more negative oxidation potential (54 mv compared to 39 mV) and over 2.5 times higher oxidation peak current (0.064 mA compared to 0.025 mA), underscoring their efficiency as electrocatalysts for MOR.

Abstract: Graphene is the only carbon allotrope in which every carbon atom is densely connected to its neighbours by an electronic cloud, raising various quantum physics concerns. In recent years, many researchers have focused their efforts on developing more efficient methods for synthesizing graphene. However, only few methods can simultaneously synthesize mass-produced, cost-effective, and high-quality graphene. In this study, we are emphasizing the use of rice husk (RH) as the raw material to prepare graphene by using two-step pyrolysis. Zinc chloride (ZnCl₂) is an example of an activating agent that is used to improve the efficiency of the synthesis of graphene from rice husk. After conducting pre-treatment of rice husk, the first stage of pyrolysis was conducted by varying the ratio of ZnCl₂ to the RH (1:1, 2:1, 3:1) at a carbonization temperature of 500 °C for 1 hour, followed by second-stage pyrolysis under 900 °C for 90 minutes and post-treatment. The findings of the characterizations, which included yield analysis, scanning electron microscopy (SEM) and Raman spectroscopy, Brunauer-Emmett-Teller (BET), and CO₂ adsorption analysis, revealed the impacts of the ZnCl₂ as activating agent, on the yield and graphitic structure of graphene and the potential application of graphene as a CO₂ adsorbent. Raman spectroscopy confirmed the graphitic properties of graphene synthesized in all samples with RH1:1 produced the best quality of graphene due to its low I_D/I_G intensity ratio (0.8913) and the highest I_2D/I_G intensity at 0.24. In addition, RH1:1 exhibited the highest surface area, whereby the highest total pore and micropore volume is contributing to the highest CO₂ adsorption capacity of 8.73 mmol/g. This proves that the activating agent ratio has significant effects on the graphene quality produced from rice husk as well as the adsorption performance.

Abstract: Interleukin-6 (IL-6) is an inflammatory cytokine that serves as an important prognostic biomarker for chronic diseases such as cancer and coronavirus disease. Label-free sensors that can conveniently detect IL-6 are essential for health monitoring purposes. Here, we present an aptamer-modified liquid-gated graphene field effect transistor (GFET) biosensor fabricated using inkjet printing techniques that can detect IL-6 levels. In this work, graphene ink suitable for inkjet printing was synthesized and formulated using the ultrasonic liquid exfoliation method. Exfoliated graphene was redispersed into a cyclohexanone/terpineol solvent system and optimized to achieve jettable ink with a Z-number of 13.7. The formulated graphene ink was then used to fabricate the GFET device, which in turn was decorated with IL-6 aptamer using organic linkers. The sensor response of the GFET was measured using the shift in the transistor current-voltage (I-V) transfer curves upon specific binding of the IL-6 with the aptameric GFET. The experimental results showed that the device can sensitively and selectively detect IL-6 in a 1xPBS background with a limit of detection of 372 pM. The fabricated GFET is on a flexible substrate that may be suitably incorporated into a face mask covering that could potentially sample IL-6 from collected saliva.