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
  • ac-dc difference
  • Thermal transfer standard
  • inductive voltage
  • uncertainty budget
  • pulse-driven ac Josephson voltage standard
应用领域
  • Measurement and Control Technology and Instruments
机构单位
  • National Institute of Metrology
1183 条数据
?? 中文（中国） ▾

  • Correction: Boosted visible light photodegradation activity of boron doped rGO/g-C <sub/>3</sub> N <sub/>4</sub> nanocomposites: the role of C–O–C bonds

    摘要： A series of two-component co-crystals driven by I···N interactions based on the bipyridine (BIPY) chromophore with one among three different co-former building blocks, iodopentafluorobenzene (IPFB), 1,4-diiodotetrafluorobenzene (DITFB) and 1,3,5-trifluoro-2,4,6-triiodobenzene (IFB), were prepared and analysed via infrared spectroscopy and single-crystal X-ray diffraction. By comparing the I···N distances in the co-crystal structures, we found that the higher the –F ratio in the building blocks the closer the contact of the I···N bond, enhancing the intermolecular interactions in these co-crystals as well. That is, the positive electrostatic potential on the iodine atom(s) in the co-formers was enhanced by the presence of strong electron-withdrawing groups. The distinct spectroscopic behaviours (fluorescence and Raman spectra) among the two-component BIPY co-crystal systems in response to hydrostatic pressure were also investigated. Interestingly, the fluorescence of BIPY–DITFB presented intriguing abnormal evolution from dark to bright, suggesting a new charge transfer state due to the decreased intermolecular distance and the enhanced I···N interactions. Theoretical simulations by Materials Studio also showed the shortened I···N distance and the increased angle of C–I···N, evidencing the enhanced I···N interactions. In contrast, BIPY–IFB showed only slightly enhanced fluorescence intensity at 550 nm consistent with BIPY–DITFB. Once the pressure was relieved, both the Raman and fluorescence spectra for BIPY co-crystal systems entirely self-recovered. Remarkable emission enhancement in a solid-state co-crystal has been rarely reported in previous publications and in fact, this study paves a unique way for designing and developing novel stimuli-responsive photo-functional materials.

    关键词： co-crystals,piezochromic materials,halogen bond,intermolecular charge transfer,pressure-induced emission enhancement

    更新于2025-11-14 15:14:40

  • Energy Transfer from Ce3+ to Tb3+ in Yttrium and Gadolinium Orthoborates Obtained by Hydrothermal Synthesis

    摘要： We studied the structure, IR absorption spectra, the spectral characteristics of photoluminescence and morphology of cerium- and terbium-doped orthoborates of gadolinium and yttrium obtained by hydrothermal synthesis at 200°C, as well as solid solutions of orthoborates on the basis of yttrium, gadolinium, and lutetium with composition RECe0.01Tb0.1BO3 (RE = Lu0.5Gd0.39, Lu0.5Y0.39, and Y0.5Gd0.39). The X-ray diffraction spectrum of yttrium orthoborate Y1 – x – yCexTbyBO3 is described by a hexagonal lattice with space group P63/m, which, after annealing at 970°C, transforms into a monoclinic lattice with space group C2/c. High-temperature annealing of the studied orthoborates leads to a multiple, more than two orders of magnitude, increase in the luminescence intensity of Tb3+ ions when the samples are excited in the absorption band of cerium ions. This effect is the result of a significant increase in the concentration of Ce3+ ions in the orthoborates at high temperatures. It is shown that the luminescence of terbium ions is due to energy transfer from Ce3+ to Tb3+, which proceeds with high efficiency (～85%) by the mechanism of dipole-dipole interaction between cerium and terbium.

    关键词： orthoborates,luminescence,Ce3+,hydrothermal synthesis,energy transfer,Tb3+

    更新于2025-11-14 15:14:40

  • Complementary Chromophore Decoration in NU-1000 via Solvent-Assisted Ligands Incorporation: Efficient Energy Transfer within the Metal-Organic Frameworks

    摘要： BODIPY-incorporated solvent-assisted ligand incorporation metal-organic frameworks (SALI-MOFs) were designed and synthesized using NU-1000 and carboxylic acid functionalized BODIPY moieties by the solvent-assisted ligand incorporation (SALI) approach. SALI-MOFs were characterized by various technique including powder X-ray diffraction, scanning electron microscope, N2 adsorption/desorption isotherms, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy. The SALI-MOFs were found to have cooperative light-harvesting properties and shown to possess efficient singlet oxygen (1O2) generation ability.

    关键词： Light-harvesting properties,Singlet oxygen,Metal-organic frameworks,Solvent-assisted ligands incorporation,Energy transfer,BODIPY

    更新于2025-11-14 15:14:40

  • Temperature sensitive properties of Eu2+/Eu3+ dual-emitting LaAlO3 phosphors

    摘要： In this study, Eu2+/Eu3+ coexisting perovskite LaAlO3 phosphors were synthesized by a traditional high-temperature solid-phase reaction method and investigated via X-ray diffraction data, X-ray photoelectron spectroscopy and temperature-dependent photoluminescence spectra. The Eu2+/Eu3+ coexisting LaAlO3 phosphors exhibit excellent optical temperature sensing characteristics and are potential inorganic materials for temperature detection. The measured maximal absolute temperature sensitivity reaches 0.014 K-1, and the corresponding largest relative temperature sensitivity is 1.193% K-1, which are superior to most of previous reports of that. Meanwhile, the monitored signal peaks are well separated, providing a good signal discriminability. The energy level crossover relaxation of Eu2+ and Struck-Fonger crossover process involving O2–-Eu3+ charge transfer band were used to explain the different temperature-dependent responses of Eu2+ and Eu3+. This work may give new ideas for the future research of optical thermometric materials with high sensitivity and high discriminability.

    关键词： Fluorescence intensity ratio,Charge transfer band,Thermometry phosphor,LaAlO3

    更新于2025-11-14 15:13:28

  • Particle transport mode during flash sintering of sodium bismuth titanate ceramic

    摘要： In this work, the NBT ceramics are successfully flash sintered at a direct current 30 mA/mm2 for 30 s under different initial electric field. Subsequently, the actual temperature of samples is estimated by blackbody radiation theory under different conditions. The calculation results show that the sample temperature is close to the densification temperature of NBT ceramics used in conventional method. The rapid densification mechanism is discussed by wetting of local contact particles due to the asymmetrical Joule heating. In particular, we analyzed the particle transport mode during flash sintering in terms of particle diffusion. It is believed that the transform in the particles transport mode from solid diffusion to flow mass transfer accelerated the particles diffusion rate, which ensure the particle rearrangement and achieve the local shrinkage of particles in a short period of time.

    关键词： Flow mass transfer,Flash sintering,Joule heating,Particles transport

    更新于2025-11-14 14:48:53

  • Illumination conditions in microsphere-assisted microscopy

    摘要： White-light microsphere-assisted microscopy is a full-field and label-free imaging promising technique making it possible to achieve a sub-diffraction lateral resolution. However, performance of this technique depends not only on the geometrical parameters but also on the illumination conditions of the optical system. In the present work, experimental measurements and computer simulations have been performed in air in order to determine the influence of the two diaphragm apertures of the K?hler arrangement and the spectral width of the light source on both the depth-of-focus of the microsphere and the optimisation of the imaging contrast. Furthermore, the super-resolution phenomenon is demonstrated and the cumulated optical aberrations are shown through the measurement of the optical transfer function for the different arrangements of the illumination part.

    关键词： Super-resolution microscopy,Illumination,Microsphere,Optical transfer function,Imaging depth

    更新于2025-10-24 16:39:32

  • Nd3+ as effective sensitizing and deactivating ions for the 2.87?μm lasers in Ho3+ doped LaF3 crystal

    摘要： The efficient 2.87 μm emission of Ho3+: 5I6 → 5I7 transition via Nd3+ sensitization in Nd,Ho:LaF3 crystal was obtained under 808 nm LD excitation for the first time. The lifetime of Ho3+:5I7 decreases dramatically from 26.28 ms to 6.41 ms via Nd3+ co-doping. The mechanism of sensitization and deactivation by Nd3+ was investigated compared with the Ho:LaF3 crystal. The absorption cross-section, emission cross-section, and fluorescence quantum efficiency were estimated and discussed. All the results indicate Nd,Ho:LaF3 crystal an attractive gain medium for solid-state lasers around 2.87 μm under an 808 nm LD pump.

    关键词： Spectroscopy,Energy transfer,Nd,Ho:LaF3

    更新于2025-10-22 19:40:53

  • New copolymer involving PVK and F8BT for organic solar cells applications: Design, synthesis, characterization and theoretical studies

    摘要： The new PVK-F8BT copolymer coupled to poly (9-vinylcarbazole) and poly(9,9-dioctyl?uorene-alt-benzothiadiazole) has been designed and elaborated by chemical oxidation for organic solar cells applications. Structural and photophysical properties were examined using di?erent and complementary techniques (Infrared, optical absorption, stationary and time resolved photoluminescence). The PVK-F8BT exhibited a broad absorption band covering the wavelength range from 200 nm to 700 nm covering the solar spectrum and, highlighting the charge transfer process. Moreover, the PVK-F8BT, showed a low band gap to be found to 1.9 eV and it average lifetime (2.62 ns) are longer than that of F8BT. The resulting copolymer exhibits original optical properties compared to the PVK and F8BT ones. The experimental analyses were coupled to theoretical calculations based on density functional theory and time-dependant density functional theory methods in order to better understand the structure-properties correlation. Furthermore DFT and TD-DFT calculations of the PVK-F8BT have been exploited to optimize the copolymer-based composites based on bulk heterojunction based organic photovoltaic copolymers with the 1-(3-methoxycarbonyl) propyl-1-phenyl-[6,6]–C61, as an acceptor. Thus, the band gap decreased to 1.69 eV, the power energy conversion e?ciency was about 7%. Our results have allowed us to discover a promising new photovoltaic material.

    关键词： TD-DFT,Optical properties,Solar cells,Donor-acceptor,Charge transfer

    更新于2025-10-22 19:40:53

  • Fluorescent pH Probes based on PET Quenching of Long Fluorescence Lifetime Triangulenium Dyes Martin Rosenberg, Anne Kathrine R. Junker, Thomas Just S?rensen, and Bo W. Laursen*[a]

    摘要： Azaoxatriangulenium dyes with long fluorescence lifetimes offer advantages in fluorescence lifetime imaging (FLIM), time-gated detection and polarization assays. However, the long excited state lifetimes are also expected to increase sensitivity to photoinduced electron transfer (PET) quenching, potentially increasing the on-off ratio of PET probes. We report the synthesis and investigation of the optical properties of azaoxatriangulenium salts substituted with phenol substituents for pH sensing. Two series of pH probes with the phenol hydroxy group placed in the ortho, meta, or para positions to azadioxatriangulenium (ADOTA) and diazaoxatriangulenium (DAOTA) chromophores are investigated. All the phenol substituted dyes possess pH responsive fluorescence signals in the biological relevant pH window (pH 6-9) due to efficient intramolecular PET from the phenolate form of the pendant arm. While the PET mechanism is partly suppressed in the phenol form the ADOTA derivatives, it is completely suppressed in the DAOTA derivatives. The long excited state lifetimes of the triangulenium dyes ensure efficient PET quenching leading to very high on-off ratios of the pH probes. The study clearly demonstrates effects of the position of the phenol/phenolate group relative to the chromophore on both PET quenching rates and pKa values.

    关键词： PET probes,triangulenium,pH probes,photoinduced electron transfer,Fluorescent probes

    更新于2025-10-22 19:40:53

  • Enhanced absorption of Sr3Lu2(BO3)4:Ce3+,Tb3+ phosphor with energy transfer for UV-pumped white LEDs

    摘要： A series green emission phosphors Sr3Lu2(BO3)4:Ce3+,Tb3+ (denoted as SLBO:Ce3+,Tb3+) with broad absorption band matching well with UV LED chip were synthesized by the solid–state reaction method. The phase and structure were analyzed with XRD, EDX, FT-IR measurements. The energy transfer between Ce3+ and Tb3+ in SLBO was proved by spectra and decay curves detailedly. The emission colors vary from blue to green by adjusting the ratio of Ce3+/Tb3+ doped concentration. With temperature increasing, SLBO:Ce3+,Tb3+ phosphor shows well thermal stability that emission intensity retains 70% of its initial at 25 oC even temperature rising to 150 oC. The internal and external quantum efficiency of SLBO:3%Ce3+,8%Tb3+ are 77.5% and 34.8% under 340 nm excitation, respectively. Combining the as-synthesized SLBO:Ce3+,Tb3+ and red emission phosphor CaAlSiN3:Eu2+ coated on a 365 nm UV chip, a warm white LEDs device with CRI of 83 was achieved. All the results indicate that the SLBO:Ce3+,Tb3+ phosphor has potential application in UV pumped white LEDs.

    关键词： phosphor,thermal stability,energy transfer,UV LED

    更新于2025-10-22 19:38:57