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Synthesis of graphene oxide from used electrode graphite with controlled oxidation process
摘要： Graphene oxide and reduced graphene oxide attract a lot of attention due to graphene provides some properties that suitable for wider application. Properties of graphene are unique since it can be tuned regarding to its controlled synthesis method and several treatments. This work, graphene oxide was synthesized from used graphite electrode by modified Hummer’s method in which oxidation process controlled. Zinc was used to produce reduced graphene oxide. Graphene oxide and reduced graphene oxide were characterized by SEM, EDS, FT-IR, UV-vis, and XRD. Effective strategy was studied to produce graphene oxide and reduced graphene oxide by controlling its oxidation process. These results prove that chemical and structural properties of graphene oxide and reduced graphene oxide depend on oxidation duration. Furthermore, carbon/oxygen ratio was studied to evaluate effective oxidation process.
关键词： graphene oxide,reduced graphene oxide,used electrode graphite,modified Hummer’s method,controlled oxidation process
更新于2025-09-11 14:15:04
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Femtosecond transient absorption spectroscopy of laser-ablated graphite and reduced graphene oxide for optical switching behavior
摘要： Carbon based materials are considered as a rewarding contestant for optical devices due to its novel properties. In this study, graphite is laser-ablated and di?erent analytical methods such as XRD and Raman spectroscopy are used to evaluate the crystalline nature. In XRD, it indicates the decreased intensity after laser ablation but no change in peak positions resulted as graphite is very strong and hard material. Scanning electron microscopy (SEM) used to evaluate structural characteristics shows the overlapping layered structure after ablation. Reduced graphene oxide (rGO) is prepared by using modi?ed Hummers' method and reduced it by thermal reduction method. UV–Vis spectra con?rmed the peaks of graphite and rGO at 274 nm and 267 nm, respectively. To study the carrier relaxation dynamics of graphite and rGO, ultrafast Visible-pump/NIR-probe femtosecond transient absorption spectroscopy was used. Carrier relaxation occurred between 260 and 309 fs even after laser ablation damage, which is useful for future application of optical switching under high laser repetition.
关键词： Optical switching,Graphite,Graphene,Laser ablation,Transient absorption spectroscopy,Ultrafast spectroscopy
更新于2025-09-11 14:15:04
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Electrospinning a Dye-Sensitized Solar Cell
摘要： Dye-sensitized solar cells (DSSCs) offer new possibilities to harvest solar energy by using non-toxic inexpensive materials. Since they can generally be produced on flexible substrates, several research groups investigated possibilities to integrate DSSCs in textile fabrics, either by coating full fabrics with the DSSC layer structure or by producing fiber-shaped DSSCs which were afterwards integrated into a textile fabric. Here we show a new approach, electrospinning all solid layers of the DSSC. We report on electrospinning the counter electrode with a graphite catalyst followed by a thin nonconductive barrier layer and preparing the front electrode by electrospinning semiconducting TiO2 from a polymer solution dyed with natural dyes. Both electrodes were coated with a conductive polymer before the system was finally filled with a fluid electrolyte. While the efficiency is lower than for glass-based cells, possible problems such as short-circuits—which often occur in fiber-based DSSCs—did not occur in this proof-of-concept. Since graphite particles did not fully cover the counter electrode in this first study, and the typical bathochromic shift indicating adsorption of dye molecules on the TiO2 layer was not observed, several ways are open to increase the efficiency in forthcoming studies.
关键词： electrospinning,environmentally friendly,graphite,nanofibers,natural dyes,dye-sensitized solar cell (DSSC)
更新于2025-09-11 14:15:04
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Stacking Order in Graphite Films Controlled by Van der Waals Technology
摘要： In graphite crystals, layers of graphene reside in three equivalent, but distinct, stacking positions typically referred to as A, B, and C projections. The order in which the layers are stacked defines the electronic structure of the crystal, providing an exciting degree of freedom which can be exploited for designing graphitic materials with unusual properties including predicted high-temperature superconductivity and ferromagnetism. However, the lack of control of the stacking sequence limits most research to the stable ABA form of graphite. Here we demonstrate a strategy to control the stacking order using van der Waals technology. To this end, we first visualise the distribution of stacking domains in graphite films and then perform directional encapsulation of ABC-rich graphite crystallites with hexagonal boron nitride (hBN). We found that hBN-encapsulation which is introduced parallel to the graphite zigzag edges preserves ABC stacking, while encapsulation along the armchair edges transforms the stacking to ABA. The technique presented here should facilitate new research on the important properties of ABC graphite.
关键词： domains,Van der Waals assembly,zigzag,stacking order,rhombohedral graphite
更新于2025-09-11 14:15:04
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Producing graphene nanosheets by pulsed laser ablation: Effects of liquid environment
摘要： Effects of liquid environment on the characteristics of graphene nanosheets produced by the laser ablation method have been studied experimentally. The fundamental wavelength of a pulsed Nd:YAG laser at 1064 nm with 7 ns pulse width and 5 Hz repetition rate was employed to irradiate a graphite target in distilled water, liquid nitrogen, alcohol, acetone, and two concentrations of cetyltrimethylammonium bromide. Produced carbon nanostructures were diagnosed using Ultraviolet-Visible-Near Infrared and Fourier transform infrared spectroscopy, x-ray diffraction, Raman spectroscopy, transmission electron microscopy, and field emission scanning electron microscope images. Results show that different carbon nanostructures such as carbon nanoparticles and fluorine, as well as graphene nanosheets were formed in various liquid environments. The size and morphology of nanostructures strongly depends on the liquid environments and, among these liquids, water is the most capable one to produce graphene nanosheets.
关键词： Raman,carbon nanoparticles,graphene nanosheets,graphite,pulsed laser ablation
更新于2025-09-11 14:15:04
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The Electrical Property of Large Few Layer Graphene Flakes Obtained by Microwaves Assisted Exfoliation of Expanded Graphite
摘要： Few layer graphene (FLG) was synthesized by (cid:2)-wave assisted exfoliation of expanded graphite in toluene with an overall yield from c.a. 7% to 20%. A significant difference in the absorption of (cid:2)-waves by the expanded graphite and toluene allowed a rapid heating of the medium. The number of FLG sheets varies from 3 to 12, while the lateral size of the sheets exceeds few (cid:2)ms. The obtained FLG exhibits very low resistance with average value of 1.6 k(cid:3) (500 (cid:3) minimum) which is comparable to that of high quality graphenes synthesized by CVD methods, and lower than numbers of exfoliated graphenes.
关键词： (cid:2)-waves,electrical properties,expanded graphite,few layer graphene,resistance.,liquid exfoliation
更新于2025-09-11 14:12:44
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Graphene paper as an emitter for low-power X-ray sources
摘要： Carbon materials are known to be one of the most suitable platforms for the development of cold electron emitters. Here we explore field emission (FE) performance of so-called graphene paper that is a micrometer-thick foil obtained by stacking chemically exfoliated graphene layers. We find, that shaped into triangular form, graphene paper exhibits competitive FE characteristics, such as high-current density stable in time, and low threshold fields. In addition, we study the degradation of such graphene-based emitters under high emissions currents and discuss possible application for a transmission-type X-ray source.
关键词： field emission,graphite emitter,x-ray source
更新于2025-09-10 09:29:36
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Epitaxial Graphene for High-Current QHE Resistance Standards
摘要： We report the growth of large-area monolayer graphene on the centimeter scale using an optimized growth process and morphology improvements. Magneto-transport measurements on graphene quantum Hall effect devices demonstrate the applicability for high-current quantum resistance metrology.
关键词： polymer-assisted growth (PASG),face-to-graphite (FTG),epitaxial graphene,quantum resistance metrology
更新于2025-09-10 09:29:36
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Change in the morphology of SnO<sub>2</sub> crystals synthesized by thermal evaporation of SnO<sub>2</sub> powder mixed with graphite in ambient air
摘要： The morphology of tin oxide (SnO2) crystals, which were formed by thermal evaporation of SnO2/graphite powder mixture, was changed with the ratio of graphite to SnO2 powder in the source material. The synthesis process was performed in air at atmospheric pressure and no catalysts and substrates were used, which makes the process very simple and low cost. At the low ratios of graphite to SnO2 powder in the source material, the SnO2 crystals had a spherical shape with nanometer dimensions. With increasing the ratio of graphite to SnO2 powder, the morphology of SnO2 crystals changed from particle to belt. The belt-shaped SnO2 crystals had the widths in the range of 1.2–3.1 μm and the lengths of several tens of micrometers. X-ray diffraction analysis showed that all the SnO2 crystals had a rutile tetragonal crystal structure. Visible emission band with the wavelength in the range of 400–600 nm was observed in the cathodoluminescence spectra of the SnO2 crystals.
关键词： Graphite,Mixing ratio,Air,Tin oxide,Thermal evaporation,Morphology variation
更新于2025-09-10 09:29:36
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Direct and Efficient Conversion from Low-Quality Graphite to High-Quality Graphene Nanoplatelets
摘要： Low-quality graphite (L-graphite), containing various impurities (e.g., metals and inorganics), can be directly and efficiently converted into high-quality iodine-doped graphene nanoplatelets (HIGnPs) via mechanochemical ball-milling in the presence of iodine (I2) with subsequent work-up procedures. Despite using L-graphite, the resultant HIGnPs show high-quality characteristics, including large specific surface area (969 m2 g?1), lower metallic residues, and well-maintained graphitic structure. In addition, HIGnPs display remarkable electrocatalytic performance for oxygen reduction reaction (ORR), involving benefits such as higher selectivity, longer-term stability, and better tolerance to methanol crossover/CO poisoning effects. Therefore, simple mechanochemical ball-milling in solid state can produce high-quality graphene nanoplatelets in large quantity at low-cost for commercialization, regardless of the initial quality of the graphite.
关键词： Oxygen reduction reaction,Mechanochemical reaction,High-quality graphene,ball-milling,Low-quality graphite
更新于2025-09-10 09:29:36