修车大队一品楼qm论坛51一品茶楼论坛,栖凤楼品茶全国楼凤app软件 ,栖凤阁全国论坛入口,广州百花丛bhc论坛杭州百花坊妃子阁

oe1(光电查) - 科学论文

过滤筛选

出版时间
  • 2018
研究主题
  • energy distribution
  • graphene edge
  • vacuum transistor
  • Field emission
应用领域
  • Optoelectronic Information Science and Engineering
机构单位
  • Naval Research Laboratory
  • KeyW Corporation
  • Pohang University of Science and Technology (POSTECH)
1443 条数据
?? 中文（中国） ▾

  • Hydrogen Induced Etching Features of Wrinkled Graphene Domains

    摘要： Wrinkles are observed commonly in CVD (chemical vapor deposition)-grown graphene on Cu and hydrogen etching is of significant interest to understand the growth details, as well as a practical tool for fabricating functional graphene nanostructures. Here, we demonstrate a special hydrogen etching phenomenon of wrinkled graphene domains. We investigated the wrinkling of graphene domains under fast cooling conditions and the results indicated that wrinkles in the monolayer area formed more easily compared to the multilayer area (≥two layers), and the boundary of the multilayer area tended to be a high density wrinkle zone in those graphene domains, with a small portion of multilayer area in the center. Due to the site-selective adsorption of atomic hydrogen on wrinkled regions, the boundary of the multilayer area became a new initial point for the etching process, aside from the domain edge and random defect sites, as reported before, leading to the separation of the monolayer and multilayer area over time. A schematic model was drawn to illustrate how the etching of wrinkled graphene was generated and propagated. This work may provide valuable guidance for the design and growth of nanostructures based on wrinkled graphene.

    关键词： graphene,hydrogen etching,wrinkling,CVD synthesis

    更新于2025-11-21 11:01:37

  • Photocatalytic Reforming of Sugar and Glucose into H2 over Functionalized Graphene Dots

    摘要： Photocatalytic reforming of biomass into H2 combining with its photosynthesis counterpart constitutes a sustainable carbon cycle that produces a clean solar fuel. This study reports the use of environmentally benign graphene-based photocatalysts to effectively reform sugar and glucose. We produce a catalyst consisting of sulfur and nitrogen codoped graphene oxide dots (SNGODs) by sequentially annealing graphite-derived graphene oxide with sulfur and ammonia, exfoliating the annealed product into dots, and autoclaving the dots in an ammonia solution. The codoping introduces quaternary nitrogen on the graphene basal plane to patch the vacancy defects and the autoclaving creates a conjugation between the nitrogen nonbonding states and the graphitic-π orbital by introducing peripheral amide and amino groups. These functionalization steps enlarge the electron resonance domain, narrowing the bandgap and inducing charge delocalization and separation. Here, when SNGODs deposited with a Pt cocatalyst effectively catalyzed H2 production from aqueous solutions of sugar and glucose under visible light irradiation for more than 80 h. The apparent quantum yields of the reforming of sugar and glucose reach 11% and 7.4%, respectively, under 420-nm monochromatic irradiation. This pioneer study demonstrates the superiority of using carbon-based photocatalysts for biomass reforming and provides a structure-tuning strategy for enhancing the catalytic activity.

    关键词： Reforming of sugar,Hydrogen production,Graphene oxide,Reforming of glucose,Photocatalytic reforming

    更新于2025-11-20 15:33:11

  • Microwave-assisted synthesis of graphene quantum dots and nitrogen-doped graphene quantum dots: Raman characterization and their optical properties

    摘要： In this report we will present completely new results on the improvement of the graphene quantum dots (GQDs) and nitrogen-doped graphene quantum dots (N-GQD) production method, using the microwave with different power levels and durations, from citric acid and urea. This is a new and unprecedented method of fabrication. The use of microwave has allowed ultra-fast fabrication of GQDs and nitrogen doped GQDs. These GQDs had their characteristics identi?ed by Raman scattering spectra for the characteristic C–C graphene vibration mode (G-peak) and defects of GQDs (D-peak). The absorption spectra of GQDs samples were fabricated under different conditions, with the expectation of different sizes, to be compared and analyzed. These absorption spectra were also compared with those of the N-GQD produced under the same conditions. The absorption mechanism of GQDs and N-GQD will be presented in detail. Measurements of the photoluminescence (PL) spectra in GQDs and N-GQD have also been recorded and analyzed. The ?uorescence mechanism will be presented, explained, and compared with other international publications of other authors. Some of the TEM and HR-TEM images of these two samples were also presented to con?rm the shape, size and in-plane spacing lattice of the GQD structure.

    关键词： graphene quantum dots (GQDs),PL spectra,nitrogen-doped graphene quantum dots (N-GQD),microwave,Raman spectra,absorption spectra

    更新于2025-11-19 16:56:42

  • Sulfur and Nitrogen Co-Doped Graphene Quantum Dots as a Fluorescent Quenching Probe for Highly Sensitive Detection toward Mercury Ions

    摘要： Sulfur and nitrogen co-doped graphene quantum dots (SN-GQDs) were synthesized through an efficient infrared (IR)-assisted pyrolysis of glucose, urea, and ammonia sulfate at 260°C. These served as a highly selective probe for the sensing of Hg2+ ions in an aqueous solution. The IR technique can also prepare N-doped graphene quantum dots (N-GQDs), which have been compared with SN-GQDs for their fluorescence (FL) quenching sensitivities by Hg2+ ions. The FL intensities of both GQDs show decreasing functions of concentration of Hg2+ ions within the entire concentration ranges of 10 ppb?10 ppm. The sensitivity of SN-GQD is 4.23 times higher than that of N-GQD, based on the calculation of the Stern-Volmer equation. One inter-band gap structure of SN-GQDs for the detection of mercury ions is proposed. The S doping can coordinate with phenolic groups on the edge of SN-GQDs (i.e., the formation of (CxO)2Hg2+) and induce the cutting off or alleviation of photon injection paths, thereby leading to significant FL quenching. This work proves that SN-GQD offers sufficient sensitivity for probing the quality of drinking water to ensure that it contains less than 10 ppb of Hg2+ ions, as per the World Health Organization standard.

    关键词： Fluorescence quenching,Nitrogen doping,Infrared-assisted heating,Graphene quantum dots,Sulfur doping,Mercury detection

    更新于2025-11-19 16:56:42

  • Nitrogen-doped graphene quantum dots: Optical properties modification and photovoltaic applications

    摘要： In this work, we utilize a bottom-up approach to synthesize nitrogen self-doped graphene quantum dots (NGQDs) from a single glucosamine precursor via an eco-friendly microwave-assisted hydrothermal method. Structural and optical properties of as-produced NGQDs are further modified using controlled ozone treatment. Ozone-treated NGQDs (Oz-NGQDs) are reduced in size to 5.5 nm with clear changes in the lattice structure and ID/IG Raman ratios due to the introduction/alteration of oxygen-containing functional groups detected by Fourier-transform infrared (FTIR) spectrometer and further verified by energy dispersive X-ray spectroscopy (EDX) showing increased atomic/weight percentage of oxygen atoms. Along with structural modifications, GQDs experience decrease in ultraviolet–visible (UV–vis) absorption coupled with progressive enhancement of visible (up to 16 min treatment) and near-infrared (NIR) (up to 45 min treatment) fluorescence. This allows fine-tuning optical properties of NGQDs for solar cell applications yielding controlled emission increase, while controlled emission quenching was achieved by either blue laser or thermal treatment. Optimized Oz-NGQDs were further used to form a photoactive layer of solar cells with a maximum efficiency of 2.64% providing a 6-fold enhancement over untreated NGQD devices and a 3-fold increase in fill factor/current density. This study suggests simple routes to alter and optimize optical properties of scalably produced NGQDs to boost the photovoltaic performance of solar cells.

    关键词： photovoltaics,optical properties,ozone treatment,nitrogen-doped graphene quantum dots,solar cells

    更新于2025-11-19 16:56:42

  • Graphene quantum dots nanoparticles changed the rheological properties of hydrophilic gels (carbopol)

    摘要： Graphene quantum dots (GQDs) have special properties at nanosize zone, as highly tunable photoluminescence, electrochemiluminescence and multiphoton excitation, that make them promising nanoagents for drug delivery systems. In this direction the use of gels to formulate nanodrugs, for both in vitro and in vivo assay is required. However, the presence of GQDs nanoparticles may affect the rheological parameters. These changes may influence the biological behavior of this formulation as change the pharmacological application. In this study we evaluated the effect of adding GQDs to carbopol gels formulation, in terms of rheological properties. In this direction, carbopol gels alone and loaded with GQDs were studied. The results of pure carbopol formulation showed a non-Newtonian, pseudo-plastic fluid without thixotropic behavior. Otherwise, the presence of GQDs in the carbopol formulation (carbopol loaded with GQDs) caused a reduction on the viscosity and modified the interactions between the polymer chains leading to the transformation of the initial gel into a viscous fluid. This alteration can change drastically the use of these formulations, especially for drug delivery, since slightly changes in viscosity can influence the occlusion, retention and permeability of these nanoparticles into biological barriers.

    关键词： Rheological properties,Drug delivery,Graphene quantum dots,Hydrogels,Carbopol

    更新于2025-11-19 16:56:42

  • One-Step Photochemical Synthesis of Transition Metal - Graphene Hybrid for Electrocatalysis

    摘要： For widespread use of renewable energy such as water splitting, the development of electrocatalysts on a large-scale at a low-cost that remains safe and environmentally friendly is still a great challenge. Here, we report the use of α-aminoalkyl radicals in a one-step procedure that synthesizes transition metal nanoparticle - graphene composites via photoreduction. The organic photocatalyst 2-Methyl-1-[4-(methylthio)phenyl]-2-(morpholinyl) phenyl]-1-butanone (I-907) undergoes Norrish Type I photocleavage to generate strongly reducing α-aminoalkyl radicals, when exposed to UVA. For the first time we demonstrate its ability to reduce graphene oxide (GO) and successfully synthesize Co3O4 nanoparticles decorated on graphene (Co3O4NP-rGO). The α-aminoalkyl radicals simultaneously reduce GO and Co2+ salts which nucleates on the negatively charged GO sheets and grows to form nanoparticles. The resulting Co3O4NP-rGO showed decent catalytic activity and stability for the Oxygen Evolution Reaction (OER). Our work introduces a new and environmentally friendly synthesis procedure that can be used to produce earth abundant transition metal electrocatalysts.

    关键词： photochemical synthesis,reduced graphene oxide,Graphene oxide,α-aminoalkyl radicals,water oxidation,metal nanoparticles

    更新于2025-11-19 16:56:35

  • Electrolyte effects on formation and properties of PEDOT-graphene oxide composites

    摘要： This work presents a comparative electrochemical and spectroelectrochemical study of composites consisting of poly(3,4-ethylenedioxythiophene) (PEDOT) and graphene oxide (GO) synthesized in different electrolyte solutions. The electrochemical behavior of PEDOT/GO composites were studied in an ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate) as well as in conventional organic (acetonitrile) and aqueous electrolytes by cyclic voltammetry and electrochemical impedance spectroscopy. Additionally, we applied in situ Attenuated Total Reflection Fourier Transformed Infrared (ATR–FTIR) spectroelectrochemistry using a Kretschmann geometry cell to study the composite fabrication during potentiodynamic electropolymerization, and to study the electronic properties and charge carrier formation during p-doping. According to in situ ATR-FTIR analysis, the doping induced bands from charge carrier formation begin to grow at lower potentials for the composite film and the electronic absorptions indicate formation of only one type of charge carrier in the composite made and characterized in ionic liquid. The optical properties during doping were determined by in situ UV–Vis spectroelectrochemistry. The composite film fabricated in water has its absorbance maximum at slightly higher wavelengths, and the appearance of the film is changed from well-known light blue color of PEDOT to greyish.

    关键词： spectroelectrochemistry,PEDOT,composite,graphene oxide,electrolyte

    更新于2025-11-19 16:56:35

  • Dual Function of Graphene Oxide for Assisted Exfoliation of Black Phosphorus and Electron Shuttle in Promoting Visible and Near-Infrared Photocatalytic H2 Evolution

    摘要： The search for suitable photocatalysts with broadband absorption in visible and near-infrared (NIR) region is recognized as one of the most challenging issues on solar energy utilization. Black phosphorous (BP) is demonstrated as an effective visible and NIR activated material in solar energy conversion. However, traditional liquid exfoliation yield is low and the rigid structure and insoluble properties of pristine BP hinder its high-yield of hybridization. Herein, a new and stable noble-metal-free ternary photocatalyst molybdenum disulfide (MoS2)-BP/graphene oxide (GO) was constructed for splitting water to H2, showing dual functions of GO in synthetic and photocatalytic processes. Under visible-NIR light irradiation, the H2 evolution rates of MoS2-BP/GO was enhanced to 3.47 μmol h-1. Rapid electron injection efficiency from excited BP to GO and to MoS2 was confirmed by femtosecond transient absorption spectroscopy. This study provides new insight into the design of nanomaterials, and offers a noble-metal-free protocol with noble-metal-free.

    关键词： visible and NIR,hydrogen evolution,graphene oxide,black phosphorous,noble-metal-free

    更新于2025-11-19 16:51:07

  • Quantum Yield Enhancement in Graphene Quantum Dots via Esterification with Benzyl Alcohol

    摘要： The quantum yield of graphene quantum dots was enhanced by restriction of the rotation and vibration of surface functional groups on the edges of the graphene quantum dots via esterification with benzyl alcohol; this enhancement is crucial for the widespread application of graphene quantum dots in light-harvesting devices and optoelectronics. The obtained graphene quantum dots with highly graphene-stacked structures are understood to participate in π–π interactions with adjacent aromatic rings of the benzylic ester on the edges of the graphene quantum dots, thus impeding the nonradiative recombination process in graphene quantum dots. Furthermore, the crude graphene quantum dots were in a gel-like solid form and showed white luminescence under blue light illumination. Our results show the potential for improving the photophysical properties of nanomaterials, such as the quantum yield and band-gap energy for emission, by controlling the functional groups on the surface of graphene quantum dots through an organic modification approach.

    关键词： Optoelectronics,Esterification,Quantum yield,Benzyl alcohol,Graphene quantum dots

    更新于2025-11-19 16:46:39