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Enhancing Diamond NV Center Density in HPHT Substrate and Epitaxy Lateral Overgrowth Layer by Tungsten Pattern
摘要： The Nitrogen Vacancy (NV) center distribution in epitaxial lateral overgrowth (ELO) single crystal diamond layer grown on tungsten patterned HPHT substrate by microwave plasma chemical vapor deposition (CVD) system has been investigated. It has been found that in ELO diamond layer densities of NV0 and NV- center above the tungsten metal are enhanced. Meanwhile, in patterned high-pressure and high-temperature (HPHT) substrate the density of NV- center beneath the tungsten metal is much higher than that of NV0. The HPHT substrate doesn't contain NV centers before CVD growth, and there is almost no NV center in the region without tungsten metal after growth.
关键词： Defects,Carbon materials,Epitaxial growth,Luminescence,Crystal growth
更新于2025-09-23 15:23:52
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One-pot synthesis of visible-light-driven photocatalyst for degradation of Rhodamine B: graphene based bismuth/bismuth(III) oxybromide
摘要： A ternary photocatalyst, graphene based bismuth modified bismuth(III) oxybromide (Bi/BiOBr/G), was synthesized via a facile one-step solvothermal method using only ethylene glycol as both solvent and reducing reagent. Bi/BiOBr/G exhibits higher photocatalytic activity than bismuth(III) oxybromide (BiOBr) on degradation of Rhodamine B under visible-light illumination, and the photodegradation rate is 4.9 times that of BiOBr. The enhanced photocatalytic activity is attributed to the synergistic effect among Bismuth, graphene and BiOBr, which can effectively promote the visible-light absorption of Bi/BiOBr/G and the separation of photogenerated charge carriers. The conditions influencing the photocatalytic performance of Bi/BiOBr/G were also investigated in detail, as well as the photocatalytic mechanism of the degradation.
关键词： Nanocomposites,Semiconductors,Carbon materials,Photocatalytic activity,Visible light
更新于2025-09-23 15:23:52
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Green Hydrothermal Synthesis of Fluorescent Carbon Dots from Glucose and Taurine for Fe3+ and pH Sensing
摘要： Carbon nanodots (C-dots), as a class of heavy-metal-free fluorescent nonmaterial have drawn increasing attention due to their strong photoluminescence (PL), good biocompatibility, and low toxicity. Herein, we synthesize nontoxic fluorescent C-dots by hydrothermal treatment of the mixture of glucose and taurine, in which process the formation and the surface passivation of C-dots take place simultaneously. The influence of reaction temperature, reaction time and feed ratio of glucose to taurine on the PL property of C-dots is studied. As the C-dots exhibit sensitive pH and iron ion dependent PL property, they can be used for pH and Fe3+ sensing in solutions.
关键词： Nanoparticles,Optical materials and properties,Carbon materials
更新于2025-09-23 15:22:29
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Fabrication of new metal-free materials for the hydrogen evolution reaction on base of the acridine derivatives immobilized on carbon materials
摘要： The process of adsorption on carbon material (Vulcan XC-72 (VU)) of organic heterocyclic compounds: acridine (I) and its derivatives 9-phenylacridine (II) and N-methyl-9-phenylacridium iodide (III) was studied in detail. Quantitative data on physical adsorption were obtained for all compounds. Based on the adsorption isotherms of Langmuir, the adsorption equilibrium constants K, the parameter A∞ and ΔG0 ad were calculated. It has been shown that the adsorption of compounds I and II is a structurally dependent process that depends on the nature and size of the functional substituents in the molecule, and the adsorption of compound III has a complex mechanism and partially proceeds through the stabilization stage by the functional groups present on the surface (-COOH, -COH, -OH). With the use of quantum chemical calculations, it has been established that the process of adsorption of compounds on the surface of a carbon materials having sections with a graphite-like structure is thermodynamically unprofitable because of the high difference in the energies of the adsorbent's boundary orbitals and the substrate. Using the cyclic voltammetry method, the electrochemical properties of organic compounds immobilized on the surface of a carbon material were studied.
关键词： Electocatalysis,Acridine derivatives,Immobilization,Adsorption,Carbon materials,Hydrogen evolution reaction
更新于2025-09-23 15:22:29
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In situ derived Ni2P/Ni encapsulated in carbon/g-C3N4 hybrids from metal–organic frameworks/g-C3N4 for efficient photocatalytic hydrogen evolution
摘要： Tightly coupling multiple cocatalysts into semiconductors for efficient charge separation is a promising way to enhance photocatalytic H2 production. In this work, Ni2P/Ni nanoparticles (NPs) encapsulated in carbon/g-C3N4 hybrids derived from in situ pyrolysis and phosphidation of Ni-based metal-organic frameworks/g-C3N4 (Ni-MOF/g-C3N4) precursor were used as photocatalysts for H2-evolution under visible-light irradiation. The highest H2-evolution rate over optimized Ni2P/Ni@C/g-C3N4-550 was 18.04 mmol g?1 h?1 with 1.0 mmol L?1 of Eosin Y (EY)-sensitization (compared to 0.21 mmol g?1 h?1 without EY-sensitization), 13 times higher than that of pristine g-C3N4 (1.33 mmol g?1 h?1). The apparent quantum efficiency at 420 nm was 58.1%. This enhanced photocatalytic activity can be attributed to an efficient and rapid separation of the photo-generated charges from excited EY and g-C3N4 to Ni2P/Ni with carbon as an electron transport bridge, intimate contact of each components, staggered band alignment among g-C3N4, Ni and Ni2P, as well as accelerated proton reduction reaction by Ni2P/Ni NPs. This work provides new insights into the construction of MOFs-derived cocatalyst for photocatalytic H2 production.
关键词： H2 evolution,g-C3N4,Ni-MOF-derived,carbon materials,Ni2P/Ni
更新于2025-09-23 15:22:29
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Near-ultraviolet Raman and micro-Raman analysis of electronic materials
摘要： Raman and micro-Raman analysis methods have been extensively investigated for the study of materials used in electronic and photonic devices. Raman studies are used to understand fundamental phonon properties, along with effects related to the crystal structure, disorder, doping, and external factors such as temperature and stress. Micro-Raman extends these investigations to the micron scale. This article reviews diverse benefits of Raman measurements when carried out using laser excitation in the near-ultraviolet wavelength range, nominally 400 to 325 nm. Micro-Raman methods in the near ultraviolet exploit the key advantage of reduced focal spot size, achievable at shorter wavelengths when using diffraction-limited optics, for mapping with high spatial resolution. There are distinct advantages common to Raman and micro-Raman spectroscopy in the near ultraviolet when compared to the widely used visible excitation. One advantage exploits the shallower optical penetration depth in select materials for probing near-surface regions or interfaces. A second advantage is related to tuning of the excitation photon energy relative to the electronic levels of a material for investigating resonance effects. Finally, the application of Raman scattering to materials which exhibit strong fluorescence requires tuning to a wavelength range away from the potentially obscuring emission. This article overviews several examples of these key advantages to study diverse applied physics problems in electronic and photonic materials. Topics covered include stress mapping in silicon and related materials, stress and thermal effects in gallium nitride and other group-III-nitride semiconductors, and carbon materials ranging from graphite and graphene to diamond grown using chemical vapor deposition. The fundamental effects of stress- and temperature-induced shifts in phonon energies and their application to study epitaxy and device-related effects are also briefly reviewed.
关键词： near-ultraviolet,stress mapping,carbon materials,chemical vapor deposition,phonon properties,Raman spectroscopy,electronic materials,micro-Raman,gallium nitride
更新于2025-09-23 15:21:01
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Preparation of graphene quantum dots with high quantum yield by a facile one-step method and applications for cell imaging
摘要： The preparation and biological applications of graphene quantum dots (GQDs) have attracted much attention. Here, a one-step hydrothermal method for synthesizing nitrogen-doped GQDs (N-GQDs) using graphene oxide (GO), ethylenediamine and hydrogen peroxide, simultaneously achieved oxidative cleavage and chemical reduction of GO. The average size of the synthesized N-GQDs was about 1.84±0.28 nm and their quantum yield of the N-GQDs reached about 0.46, which was higher than that of other GQDs synthesized by top-down methods. The cytotoxicity of these N-GQDs on Hela cells was evaluated using a cell counting Kit-8 assay. The effects of N-GQDs on different cell lines and fluorescence imaging were also observed by confocal laser scanning microscopy. The results suggested that these N-GQDs penetrated into cells by endocytosis and were promising fluorescent probes for biological imaging.
关键词： Carbon materials,Hydrothermal reaction,Luminescence,Graphene quantum dots,Bio-imaging
更新于2025-09-23 15:21:01
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Freestanding graphene oxide-polytetrafluoroethylene membranes with excellent photothermic performance for laser ignition
摘要： A new kind of laser energy convertor with highly improved photothemic performance was fabricated using a facile and versatile approach, which was composed of graphene oxide and polytetra?uoroethylene membranes. SEM, XRD and TG-DSC were performed to characterize and compare the morphology, composition and heat release of the different graphene oxide and polytetra?uoroethylene membranes. The optimized freestanding composite membrane exhibited highly improved photothermic temperature rise under the laser irradiation (from 132 (cid:1)C to 236 (cid:1)C), which was further used as the laser energy convertor for the laser ignition and largely reduced the threshold power for laser initiators (approximately 48%). These results can promote the development of superior laser energy convector and also laser initiators with low ignition energy.
关键词： Nanocomposites,Carbon materials,Thin ?lms,Nanoparticles
更新于2025-09-23 15:19:57
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Electromagnetic Wave Absorbers (Detailed Theories and Applications) || Fundamental EM‐Wave Absorber Materials
摘要： In this chapter, in order to obtain basic knowledge of carbon materials and ferrite materials, which are typical EM-wave-absorbing materials, their respective characteristics are examined, especially from the viewpoint of molecular and crystal structures. The Jaumann absorber in early stage of the EM-wave absorber was composed of overlaying the material dispersed carbonyl iron to rubber, the resistive sheet, and the dielectric plate, as described in Chapter 1. In this way, since the absorber was invented, carbon-based materials have been mainly used as EM-wave-absorbing materials. On the other hand, copper–zinc-based soft ferrite was invented in 1930 in Japan. However, the nature of this kind of soft ferrite as an EM-wave absorber was unknown for a long time. Magnetic materials typi?ed by ferrite, metallic resistors, and carbon materials used as resistive ?lms are applied to EM-wave absorbers, and they have changed little to this day.
关键词： molecular and crystal structures,EM-wave absorbers,ferrite materials,carbon materials
更新于2025-09-19 17:13:59
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Improving the Wear Life of a-C:H Film in High Vacuum by Self-Assembled Reduced Graphene Oxide Layers
摘要： As an energy-e?cient surface modi?cation method, self-assembly has been the subject of extensive research. However, its application on carbon ?lm has been rarely reported. In the present work, a novel self-assembled reduced graphene oxide (RGO) was prepared on a-C:H ?lm by a controllable self-assembly method, and the friction behavior of the RGO/a-C:H ?lm was investigated under vacuum environment. Interestingly, the RGO/a-C:H ?lm exhibited signi?cant improvement of anti-wear ability in vacuum conditions under a high applied load of 5 N. As expected, the synergy lubrication e?ect of the RGO layer and a-C:H ?lm should account for the excellent friction reduction and anti-wear ability of a RGO/a-C:H multilayer ?lm.
关键词： vacuum,wear,reduced graphene oxide,a-C:H ?lm,carbon materials,self-assembly
更新于2025-09-16 10:30:52