最新刊期
卷 35 ， 期 9 ， 2014
- 摘要：Nitrogen-dopped carbon nanodots are emerging stars in carbon-based nanomaterials. Herein, we introduce our works on nitrogen-dopped nanodots, which were prepared through one-step microwave synthesis route. Our works demonstrated that the optical properties of the carbon nanodots can be modulated by nitrogen dopping concentrations and surface chemical environments, and realize carbon-nanodot-based fluorescent inks, ratiometric fluorescent nanosensor and optical pumped laser. Our studies aim at exploiting the luminescent mechanism of the nitrogen-dopped carbon nanodots, revealing the influencing factors on their luminescent quantum yields and their applications in bioimaging, sensing security, information storage, lasers and so on.关键词：carbon nanodots;nitrogen dopping;fluorescent ink;fluorescent nanosensor;laser165|143|6更新时间：2020-08-12
- 摘要：The valence state of Ce in the polycrystalline Lu2SiO5:Ce(LSO:Ce) luminescent powders was characterized by X-ray absorption near edge structure (XANES) spectra. The result demonstrates that Ce3+ contents relative to Ce in the LSO:Ce powders with different Ce-doped concentration are only 18%~39%. Annealed at 1 000 ℃ for 2 h in a flowing hydrogen atmosphere, the relative Ce3+ content of LSO:0.5%Ce powder increases significantly to 83% from 39%. The emission spectra excited by vacuum ultra violet (VUV) suggest that the luminescence intensity of LSO:Ce with Ce mole fraction from 0.25% to 1% is correlated closely with Ce3+ content in the powders. The luminescence intensity of LSO:0.5%Ce increases about 40% by annealing in a flowing hydrogen atmosphere. The emission intensity is very stable at different temperatures (50~250 K) without thermal quenching effect observing.关键词：LSO：Ce;valence state;XANES;VUV spectra114|503|0更新时间：2020-08-12
- 摘要：Series of blue phosphors YVO4:xTm (x=0.001, 0.003, 0.005, 0.007, 0.01, 0.03, 0.05) were synthesized by the high temperature solid state reaction in this paper. X-ray diffraction shows that the product is a tetragonal zircon structured single phase. The result is consistent with JCPDS standard card (72-0861). The vacuum UV excitation spectrum and emission spectra of the phosphors at room temperature were also detected. The vacuum UV excitation spectrum of YVO4:xTm includes a continuous banded peak in the range of 120-350 nm, and there are two significant peaks at 155 nm and 333 nm. Excited by 155 nm, the emission spectrum of YVO4:xTm consists of two parts. The main emission spectrum at 474 nm is a sharp peak, caused by 1G4→3H6 transition of Tm3+. The weaker emission peak is at 650 nm, which is generated by 1G4→3H4 transition of Tm3+. In addition, there is a weak band emission centering around 540 nm, which presents broadband emission of VO43- ions. With the increasing of Tm3+ mole fraction (x) from 0.001 to 0.005, the emission intensity gradually increases to a maximum value. Then, as x increases continuously, the emission intensity decreases gradually, presents an obvious concentration quench. By analyzing the spectra of YVO4:xTm and its luminescent mechanism, it can be derived that YVO4:Tm3+ is a kind of blue phosphor material with high luminous efficiency and color purity under ultraviolet or vacuum ultraviolet excitation.关键词：blue emitting;YVO4：Tm3+;vacuum ultraviolet103|123|1更新时间：2020-08-12
- 摘要：Developing growth techniques to suppress phase separation is a key point to realize bandgap modulation of MgZnO from 3.3 to 7.8 eV. A graded quasi-homo buffer layer, composed of a MgO layer and a continuously Zn-increased MgZnO layer, was used to grow pure cubic MgxZn1-xO thin films on c-plane sapphire by MOCVD method. The Zn content in rocksalt MgxZn1-xO is expanded to ~0.7 and the optical bandgap of the films was decreased as low as 4.45 eV, corresponding to the long wavelength edge of solar-blind band. Parallel experiments suggested that the buffer layer played an important role as a structural template for the following growth of Mg0.3Zn0.7O epilayers and a substrate temperature range from 350 ℃ to 400 ℃ was benefit to increase solution of Zn in the RS-MgZnO films. A photoconductive UV detector based on a Mg0.3Zn0.7O film exhibits responsivity peak at 270 nm and a cutoff wavelength at 295 nm.关键词：cubic MgZnO;buffer layer;bandgap modulation114|55|0更新时间：2020-08-12
- 摘要：A single host white phosphor Ca3Y2-xSi3O12:xDy3+ excited by near UV light was synthesized by the high temperature solid-state method at 1 400 ℃. XRD analysis showed that the principal crystalline phase was Ca3Y2Si3O12 .The results of fluorescence spectroscopy indicated that Ca3Y2-xSi3O12: xDy3+ silicate phosphors could be effectively excited by near UV light of 348 nm, emitting white lig hts with two main emission peaks located at 481 nm(4F9/2→6H15/2)and 572 nm (4F9/2→6H13/2) respectively. When monitored at 481 nm, the excitation spectrum ranged from 300 to 450 nm and the main peak was located at 348 nm. The effects of the doping concentration of Dy3+ ion and the flux of H3BO3 to the emission intensity of the phosphors were studied. It is found that the optimum dopicontent of x(Dy3+) is 5% and the optimum mass fraction of the flux is 2%. The chromaticity coordinate of the phosphors change with the doping concentration and the amount of flux.When x(Dy3+) is 5% and the mass fraction of H3BO3 is 2%, the chromaticity coordinate of the phosphor is (0.290,0.330) which locates within the scope of the chromaticity coordinate of the standard white point.关键词：high temperature solid-state method;white light emitting diode;phosphors;Dy3+ doping;flux101|35|2更新时间：2020-08-12
- 摘要：The photoluminescence (PL) spectra of CdSe/ZnS (3 ML) core/shell quantum dots (QDs) and CdSe/CdS (3 ML)/ZnCdS (1 ML)/ZnS (2 ML) core/multishell QDs were measured in the temperature range from 80 to 460 K by steady-state PL spectroscopy. The temperature dependence of PL energy, linewidth, and intensity for CdSe QDs was investigated. It is found that the thermal stability of CdSe QD emissions is significantly dependent on the shell structure. The thermal activation energy of CdSe/CdS/ZnCdS/ZnS core/multishell QDs is higher than that of CdSe/ZnS core/shell QDs. Furthermore, the stability of CdSe QDs at high temperature was also examined through heating-cooling cycling experiments. The permanent loss of PL intensity for CdSe/CdS/ZnCdS/ZnS core/multishell QDs is smaller than that of CdSe/ZnS core/shell QDs.关键词：CdSe;quantum dots;nanocrystals;temperature-dependent photoluminescence spectroscopy130|378|4更新时间：2020-08-12
- 摘要：Er3+, Yb3+ doped NaYF4 phosphors were prepared by high-temperature solid state method. Structures of the samples were investigated by X-ray diffraction. The excitation and emission spectra of the phosphors were measured. The 377 nm photon jumped from 4G11/2 to 4F9/2, and the energy was transferred to 2F5/2 energy level of Yb3+. A 975 nm near-infrared photon was thus obtained. Then, the photon in 4F9/2 jumped to the ground state and emitted a 670 nm red photon. Furthermore, the luminescence decay curves of 541 nm emission excited by 377 nm were measured, and the quantum efficiencies were calculated. The maximum quantum efficiency was 126.35%. By monitoring the 975 nm emission, the energy transfer from 4F7/2(485 nm) and 2H11/2(519 nm) of Er3+ to Yb3+ also occurred by down-conversion. This research has not been done before.关键词：down-conversion;quantum cutting;lifetime;quantum efficiency;solar cells124|224|3更新时间：2020-08-12
- 摘要：Holmium doped ytterbium gallium garnet (Ho:YbGG) polycrystal powder was synthesized by low temperature combustion method using citric acid as combustion agent. The mole fraction of Ho3+ was 2%. The Ho:YbGG polycrystal powder was determined by X-ray diffraction analysis and SEM analysis. The results show that 900 ℃ is the optimum calcination temperature. The absorption spectrum of the sample shows that the absorption peaks of Ho3+ are centered at 536 nm and 645 nm, corresponding to 5I8→5F4 (5S2) and 5I8→5F5 level transitions, respectively. The strong absorption bands of Ho3+ are centered at 940 nm and 982 nm, corresponding to 2F5/2→2F7/2 level transition. The fluorescence spectra of the samples show that the strong emission band of Ho3+ is centered at 1 989 nm, corresponding to 5I7→5I8 level transition. The upconversion spectrum of the sample was tested and the corresponding conversion mechanism was analyzed. Ho:YbGG can emit strong green and red light under 980 nm LD excitation, which are corresponding to 5F4(5S2)→5I8 and 5F5→5I8 level transitions of Ho3+.关键词：holmium doped ytterbium gallium garnet polycrystal powder;low temperature combustion method;absorption spectrum;upconversion fluorescence spectrum170|160|1更新时间：2020-08-12
- 摘要：Novel Li+-, Na+-, K+-, and Si4+-doped Ca2.96Eu0.04(PO4)2 red phosphors were synthesized using a conventional solid-state reaction route. The effects of codoping of charge compensatory ions on the phase and luminescent properties of Ca2.96Eu0.04(PO4)2 red phosphors were investigated by X-ray diffraction and photoluminescence spectra. The excitation spectra include both broad band (200-310 nm) and sharp peaks (310-500 nm). From emission spectra, it is observed that these phosphors exhibit two dominating bands situated at 593 and 616 nm, originating from the 5D0→7F1 and 5D0→7F2 transition of the Eu3+ ion, respectively. The luminescence of Ca2.96Eu0.04-(PO4)2 can be enhanced by the incorporation of Li+, Na+, K+, and Si4+. Furthermore, the charge compensation mechanism was discussed. The charge compensatory additives have little influence on the decay times and CIE of all the phosphors. The CIE chromaticity coordinates of these phosphors all locate in the red region. It implies that Ca2.96Eu0.04(PO4)2 is a good candidate as a red-emitting phosphor pumped by near-ultraviolet (NUV) InGaN chip for fabricating white light-emitting diodes (wLEDs).关键词：solid-state reaction;charge compensatory;Ca2.96Eu0.04(PO4)2;red phosphors111|125|2更新时间：2020-08-12
- 摘要：NaEu(MoO4)2-x(WO4)x solid solution microcrystallines were synthesized by hydrothermal method. The structure, morphology and photoluminescent properties of the microcrystallines were studied by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and fluorescence analysis (FA). XRD results show that NaEu(MoO4)2-x(WO4)x microcrystallines are all typical scheelite structure with tetragonal symmetry. SEM measurements reveal that the phosphors are rice-like particles. The fluorescence analysis (FA) results reveal that the characteristic emission peak of MO42- (M = Mo, W) complex ion appears from 370 to 386 nm, and blue shifts with the increasing of x. Moreover, the characteristic emission peaks located at 592 nm and 614 nm of Eu3+ all appear obviously, and the intensity gradually increases with the increasing of x.关键词：NaEu(MoO4)2-x(WO4)x solid solution microcrystallines;hydrothermal methods;red phosphors;luminescent properties114|76|1更新时间：2020-08-12
- 摘要：We regard the nanocrystalline silicon films as an ideal one-dimensional quantum limiting surface structure, and study the band structure and density of states of the different thickness silicon (111) quantum surface by the first-principles calculation. As the change of the thickness of the quantum surface well passivated by Si—H bond, the band gap mainly follow the quantum confinement effect. When the silicon (111) quantum surface contains Si—N bond, the simulated results show that the band gap is mainly determined by the quantum confinement effect in a certain range of thickness, but beyond the thickness, the band gap is determined by both the quantum confinement effect and bond structure. While maintaining a constant thickness, the greater doping concentration of the quantum surface, the more obvious the band gap narrowing effect. Similarly, the simulated result of silicon (111) quantum surface which contain Si—Yb has the same effect. It is worth noting that almost all of the simulated results show that the band structures of the quantum surface show quasi-direct band gap characteristics.关键词：silicon quantum surface;surface bond;quantum confinement effect;band gap narrowing effect105|315|0更新时间：2020-08-12
- 摘要：In order to avoid the damage of high reaction temperature to OLEDs, the low-temperature atomic layer deposition (ALD) process was introduced to deposite Al2O3 film for the encapsulation of OLEDs. However, the low temperature condition would decrease the uniformity of the film. In order to suppress the generating of vacancy, the pumping gas time(PGT) was increased during each cycle to discharge the products adequately. The micrographs, calcium test and lifetime test of OLEDs show that the film deposited at low temperature is almost the same with that deposited at high temperature, and the temperature effect to OLEDs is not negligible. The water vapor transmission rate (WVTR) of the film can reach to 8.6×10-4 g/(m2·d), so the lifetime of the device with the encapsulation layer can be increased effectively.关键词：atomic layer deposition;film uniformity;low temperature126|152|7更新时间：2020-08-12
- 摘要：The normalized spectral power distributions of the LED arrays with various substrate temperatures and 350 mA drive current were measured, the centriod wavelengths were calculated, and then the relationships between the centriod wavelength and the change in the average junction temperatures of LED arrays were analyzed. Finally, the accuracy of the new method was studied. The results show that the centriod wavelength measured with spectrometer of 1 nm step changes linearly with the variation of average junction temperature, and the linearity is much better than that of the proposed center wavelength method. Moreover, the precision of estimating the junction temperature with the centroid wavelength is much higher. Therefore, the centroid wavelength test would be an effective method to determine the average junction temperature of AlGaInP-based LED array.关键词：spectroscopy;light emitting diode array;junction temperature measurement;spectral analysis;centroid wavelength196|176|2更新时间：2020-08-12
- 摘要：In order to achieve high output power of 808 nm vertical cavity surface emitting laser (VCSEL) array, the DBR material of 808 nm VCSEL was optimized, and Al content of AlxGa1-xAs was analyzed for the influence on refractive index and absorption. Based on the above analysis, 2 × 2 VCSEL array was designed and fabricated with non-closed ring structure. The peak power of the VCSEL array was tested under waveform analysis method. The peak power is 30 W in 60 ns pulse width and 100 Hz repetition rate, and 9 W in 20 ns pulse width and 100 Hz repetition rate, respectively. The near-field and far-field of VCSEL array were also measured. The beam divergences with full-width at half maximum are 16.9° and 17.6° in the vertical and lateral directions, respectively.关键词：high peak power;808 nm;VCSEL;arrays131|145|2更新时间：2020-08-12
- 摘要：We fabricate C60-based organic field-effect transistors (OFETs) with a biomaterial (albumen) as the gate dielectrics. The devices demonstrate reasonable electrical characteristics. The effective field-effect mobility is 2.59 cm2·V-1·s-1, and the threshold voltage is 1.25 V. The enhanced performances of the OFETs are attributed to the high dielectric constant, smooth surface after the appropriate thermal treatment of the albumen dielectric. The experiments show that albumen is a promising dielectric material for OFETs.关键词：organic field effect transistors;gate dielectrics;biomaterial;albumen;C60114|76|0更新时间：2020-08-12
- 摘要：We investigated the ~2 μm lasing performance of Tm3+ doped tellurite microstructure fiber pumped by an Er3+ doped silica fiber laser operating at 1 560 nm. The microstructure fibers consisting of a solid core surrounded by six air holes were fabricated by using a rod-in-tube method. A maximum unsaturated power of 9 mW laser operating at ~1 872 nm was obtained in a Tm3+ doped 2.8 cm long microstructure fiber with the slope efficiency of ~6.53% and the threshold power of ~200 mW. The results indicate that the Tm3+ doped tellurite microstructure fiber is a promising material for the compact 2 μm fiber laser.关键词：Tm3+ doped;tellurite glasses;microstructure fiber;fiber laser121|100|1更新时间：2020-08-12
- 摘要：In Tris-HCl buffer solution (pH=7.4), the interactions of moxifloxacin, norfloxacin, ofloxacin, enrofloxacin, lomefloxacin, and ciprofloxacin with bovine serum albumin were studied, respectively. Using modified Scatchard equation, Lineweaver-Burk double reciprocal equation, double logarithmic equation, modified Stern-Volmer equation, and improved double logarithmic equation, the binding constants and binding points of drugs with bovine serum albumin were calculated, respectively. For the binding reaction of drug-protein ratio of 1:1, the calculation results are very close except modified Scatchard equation, and the improved double logarithmic equation is the most accurate.关键词：bovine serum albumin;binding constant;combination of points;comparative study147|508|2更新时间：2020-08-12
- 摘要：The experimental setup was constructed with a 300 W high stability Xenon lamp, fore condenser lens, concave grating flat-field monochromator, programmable digital micromirror device (DMD), post condenser lens and integrating sphere. The test experiments of light source spectral radiances were carried out and the measurement results of spectral radiances of light source in broad-band and narrow-band modes were obtained. The developed experimental unit of spectrally tunable light source can produce optical radiation with different spectral distributions as needed by programmable manipulations, and the operability of programmatically changing spectral distributions of light source was indicated.关键词：tunable source;spectral radiance;spectroradiometer112|73|4更新时间：2020-08-12
- 摘要：Meso-2,3-dimercaptosuccinic acid (DMSA) assembled on activated silver electrode was analyzed by in-situ electrochemical surface-enhanced Raman scattering (EC-SERS) and electro-reduction. Density functional theory calculations had been carried to obtain the molecular optimization structure and theoretical Raman spectra. The reduction peak of S-Ag derived from DMSA on activated Ag was at -0.4 V (vs. SCE). Under the same self-assembly time, a linear regression fit between the reciprocals of surface coverage and solution concentration was investigated by using linear sweep voltammetry (LSV), which indicating that DMSA monolayer adsorbed on surfactivity Ag obeys the Langmuir isothermal adsorption equation. The maximum surface coverage of DMSA on Ag electrode from LSV was 5.41×10-10 mol·cm-2, and the adsorption coefficient was 3.74×103 L·mol-1. The stabilized SERS signals of target concentrations were detected after 50 min for an adsorption equilibrium at acid condition. It was found that EC-SERS intensities became weaker, and the peaks eventually disappeared when the potential was negatively shifted. A single molecule area for DMSA adsorbed on Ag substrates was 0.389 nm2, and the effective depth of 785.18 nm laser beam irradiated to the ideal solution focusing surface was 3.461 μm. Furthermore, the performance change of silver electrode was proposed by calculating enhancement factor (EF) at different potentials. As a result of reduction/desorption behavior of DMSA at relatively negative potentials, EF of probe molecule on silver was significantly reduced and the Raman enhanced activity was lost especially the potential value was less than -0.4 V.关键词：electrochemical SERS;Langmuir isothermal adsorption;2;3-dimercaptosuccinic acid;silver electrode;enhancement factor115|194|0更新时间：2020-08-12
- 摘要：A metal-multi-insulator-metal surface plasmon waveguide was proposed, and finite-difference time-domain method was employed to research the transmission property. The dependence of thickness of insulators on effective refractive index and propagation length were investigated. The effect of angle of metal layer on the field distribution in waveguide was also analyzed. The simulation results show that the electromagnetic field is confined in high index region and coupling transmission is realized as the light wave is normally incident. The transmission characteristic of waveguide with regular hexa-gon metal is relative well as the thickness of multi-insulator is 220 nm. This waveguide is able to complete the light confinement at subwavelength scale and applied in electronics integration and sensor.关键词：surface plasmon waveguide;multi-insulator;transmission property;coupling transmission;optoelectronics integration105|212|2更新时间：2020-08-12
- 摘要：Based on improved effective index method, the coupled-mode theory and transmission matrix method, the influence of Gaussian apodizations and chirp coefficients on group delay of photonic crystal fiber Bragg gratings are demonstrated. The results indicate that the group delay first increases and then decreases when apodization coefficients increase, which means that the maximum value of group delay can be obtained at a given apodization coefficient. A good linear area of the group delay can be obtained by linear chirp gratings, and the linear area is broadened by increasing the absolute value of chirp coefficient. But linear chirp gratings don't get smaller group velocity in a particular band. Gaussian apodization is an effective way to tailor the group delay of fiber gratings, which can not only adjust the full width at half maximum but also influence the height.关键词：photonic crystal fiber grating;Gaussian apodization;chirp;slow light94|139|2更新时间：2020-08-12
- 摘要：A rapid reliability evaluation method of LED lamp was proposed based on the acceleration degradation test. In order to evaluate the service life of lamps, the accelerated degradation test(ADT)was conducted under the integrated stress of temperature-electrical, and a general procedure for an accelerated degradation test was used to analyze the useful lifetime of LED lamps under operating conditions through analyzing the lumen maintenance data collected from ADT. The reliability of a type of LED tube was evaluated implementing the approach proposed in this article. The failure criterion was defined as the 70% decrease of the emitted optical power compared with the initial level. The results show that the failure time of a LED tube under operating conditions is about 31 571 h. This designed procedure can evaluate the reliability of LED lamps quickly and effectively. It not only can save the experiment time, but also provide the foundation for evaluating reliability and managing product quality.关键词：LED;acceleration degradation test;reliability assessment;accelerated model133|433|9更新时间：2020-08-12
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