最新刊期
卷 33 ， 期 5 ， 2012
- 摘要：NaGdF4 and GdB3O6 doped with Pr3+ and/or Tb3+ were prepared and their VUV excited fluorescence properties were studied. Gd3+ plays an important role in the energy transfer process from Pr3+ to Tb3+ upon the excitation of VUV photons. No obvious energy transfer from Pr3+ to Tb3+ was observed in the absence of Gd3+; on the contrary, Pr3+ transfer most of the energy to Gd3+ after Gd3+ was added, then the energy was transferred from Gd3+ to Tb3+. So the conversion from the near ultraviolet emission of Pr3+ to the green emission of Tb3+ was realized.关键词：energy transfer;rare earth ions;vacuum ultraviolet (VUV);quantum cutting86|64|0更新时间：2020-08-12
- 摘要：The oxonitride blue-green phosphor BaSi2O2N2∶Eu2+ has been prepared by solid state reaction. The prepared BaSi2O2N2∶Eu2+ phosphors are characterized by X-ray powder diffraction (XRD), photoluminescence (PL), etc. The XRD results show that pure phase phosphors are obtained. The PL results demonstrate that BaSi2O2N2∶Eu2+ shows high efficient emission with peak at around 492 nm. The best emission can be obtained with the Eu2+ mole fraction of 4%. The phosphors are encapsulated on the ultraviolet and blue chips, high blue-green luminescence is obtained in both devices, and the CIE parameters are (0.092 0,0.428 2) and (0.112 9,0.223 0), respectively.关键词：LED;phosphor;oxonitride;BaSi2N2O2∶Eu2+100|126|4更新时间：2020-08-12
- 摘要：Near-infrared (NIR) to near-ultraviolet (NUV) upconversion (UP) luminescence properties were explored under 980 nm laser diode (LD) excitation in Yb3+, Er3+ codoped calcium fluoride (CaF2∶Yb3+, Er3+) nanoparticles. The strong enhancement at 407 nm was observed. The results show that the UV enhancement is independent on both the Er3+ concentration and the excited power, while dependent on the annealed time and the particle size. The UP mechanical and thermodynamics process were also discussed.关键词：rare earth;nanoparticles;near infrared;near vultraviolet;upconversion emission104|152|1更新时间：2020-08-12
- 摘要：NaYbF4∶0.01%Tm3+,20%Eu3+ nanocrystals were synthesized by hydrothermal method. The crystalline phase, morphology, and optical properties were characterized by X-ray diffraction, scanning electron microscope and luminescent spectra. The samples are nano-rods with uniform size distribution. Their length is 500 nm and diameter is 200 nm on average. Under 980 nm near-infrared laser excitation, ultraviolet and visible upconversion luminescence of Eu3+ was obtained. In the codoped NaYbF4 nano-rods, the energy transfer from Tm3+ to Eu3+ and the bridging effect of Tm3+ ions play important roles in populating the high-energy excited states of Eu3+. Furthermore, the upconversion emissions from 3P0→7Fj(j=0,1,2) of Eu3+ were observed for the first time.关键词：Eu3+;nanomaterials;ultraviolet;upconversion;luminescence133|106|1更新时间：2020-08-12
- 摘要：High orientated undoped ZnO thin films were prepared on c-Al2O3 substrates by pulsed laser deposition (PLD) method and using ZnO ceramic target as resource material. The photoluminescence (PL) origin of the ZnO thin films was discussed in detailed. PL spectrum of ZnO thin films is dominated by donor-bound exciton (D0X)emission at low temperatures while the free exciton transition (FX) gradually dominates the spectrum at higher temperatures. It notes that one emission band A at around 3.309 eV (T=10 K) can be clearly observed with increase in temperature up to room temperature. The mechanism of this emission band was investigated by the temperature dependence of PL spectra. The results can be attributed to the transition of conduction band electrons to acceptors (e,A0), in which the acceptor binding energy was approximately 129 meV. However, the formation mechanism of the acceptor states need be investigated further.关键词：pulsed laser deposition;ZnO thin films;photoluminescence98|178|4更新时间：2020-08-12
- 摘要：Pr3+, Yb3+ co-doped YPO4 downconversion phosphor powders were prepared by solid state reaction. When excitation at 450 nm, the effects of different Yb3+ mole fractions (0%,1%,2%,4%,20%,30%) on the conversion efficiency are studied. Results shows that because of the difference of energy transfer efficiency between Pr3+ and Yb3+, the samples with various Yb3+ doping concentrations have different fluorescence intensity. It is also found that the energy transfer process of the downconversion luminescence in samples is Pr3+:3P0→Yb3+:2F5/2+2F5/2. From photoluminescence spectra measurement, the optimal doping mole fraction of Yb3+ is 2%. The results indicate that Pr3+, Yb3+ co-doped YPO4 downconversion phosphor is a kind of potential material which may be used to improve the solar cell efficency.关键词：downconversion;rare earth;YPO4;solar cells199|64|2更新时间：2020-08-12
- 摘要：Under the effects of hydrostatic pressure and screening on the infinite GaAs/AlxGa1-xAs and GaN/AlxGa1-xN quantum wells, the binding energies of the impurity are calculated by the variational method in the two systems. The impurity binding energies as functions of the well width and pressure are given. The result indicates that the binding energy increases with pressure, but decreases with well width. We also discussed the binding energies of impurity with and without the screening effects. It is found that the screening effect became stronger as pressure increases, and then decreases the binding energy of impurity significantly.关键词：quantum well;pressure;screening;binding energy70|115|0更新时间：2020-08-12
- 摘要：The phosphor Ca4LaNbMo4O20∶Pr3+ has been prepared by the solid-state method. The photoluminescence (PL) properties have been investigated. The XRD patterns are similar to that of CaMoO4 structure. The excitation spectrum of Ca4LaNbMo4O20 exhibits a broad absorption band at 257 nm, which is attributed to the charge transfer states (CTS) of MoO42- and NbO43- complexes. The excitation spectrum of Ca4LaNbMo4O20∶Pr3+ shows an absorption band centered at 287 nm, which is attributed to the 4f→4f5d transition of Pr3+. The excitation spectrum of Ca4LaNbMo4O20∶Pr3+ also shows two weak shoulder absorption bands at about 266 and 320 nm, which are originated the charge transfer states (CTS) of MoO42- and NbO43- complexes and the intervalence charge transfer (IVCT) transition of Pr-metal, respectively. The 4f-4f transitions of Pr3+ are also observed in the region of 420~520 nm. As a result, it can efficiently convert the blue pump light of the Ⅲ-N semiconductor LED into visible wavelength bands. The photoluminescence spectrum of Ca4LaNbMo4O20∶Pr3+ excited with 452 nm shows the green and red emissions originated of the 3P0→3H4 (490 nm) and 1D2→3H4 (607 nm) transitions of Pr3+ ions, respectively. At excited with an ultraviolet wavelength of 287 nm, the emission spectrum of Ca4LaNbMo4O20∶Pr3+ exhibits the broad emission band centered at 490 nm and several sharp emission peaks at 490,536,561,607 nm. The broad band is belonging to the overlap of the host emission and the 4f5d→4f transition of Pr3+ ions. The sharp emission peaks are attributed to the 3P0→3H4,3P1→3H5,3P0→3H5 and 1D2→3H4 transitions of Pr3+ ions. It is speculated that the energy transfer occurs from the MoO42- and NbO43- complexes to Pr3+ ions. However, the efficiency of energy transfer is very weak.关键词：Ca4LaNbMo4O20∶Pr3+;photoluminescence;energy transfer90|49|1更新时间：2020-08-12
- 摘要：Aluminium nitride and chromium nitride were synthesized by high temperature solid state method with aluminium, chromium and high purity nitrogen. Two types of methods were used to obtain Cr3+-doped AlN: one is to nitride mixtures of aluminium and chromium, the other is to heat aluminium nitride and chromium nitride at 1 400 ℃ for 3 h under nitrogen. X-ray diffraction analyzer was used to measure the crystal structure of obtained samples. The excitation and emission spectra of the samples were measured by spectrometer. The obtained data showed that the excitation and emission spectra of Cr3+∶AlN obtained by two methods are similar, two broad excited bands, peak at 400 nm and 500 nm, and the emission peak at 696 nm, while the intensity of the latter was higher than that of the former due to higher annealing temperature. According to the excitation and emission spectra of Cr3+∶AlN, Dq/B and the energy levels of Cr3+ion in AlN were given. The obtained data showed that the emission of Cr3+at 696 nm came from the first excited state 2E, which is similar to that of Cr3+ in Al2O3 host.关键词：AlN;emission;Cr3+ ion;energy level110|434|0更新时间：2020-08-12
- 摘要：The growth rate and surface structure of AlGaAs sample were investigated by employing the optical in-situ monitoring technique. In situ monitoring of optical time resolved normalized reflectance (NR) and reflectance anisotropy (RA) in growth process of multilayer AlxGa1-xAs sample was carried out. Oscillation characteristics of NR curve was analyzed. Converged value of NR and RA curve changed monotonously with Al composition at the monitoring optical energy of 1.9 eV. The growth rate was gained from fitting the NR transient. And the deviation of calculated growth rate was lower than 0.02 nm/s compared to the SEM measurement results. From the analysis of time resolved RA curve, surface reconstruction caused by the growth temperature was observed during the epi-growth of GaAs layers.关键词：normalized reflectance;reflectance anisotropy spectroscopy;in-situ monitoring;MOCVD111|193|0更新时间：2020-08-12
- 摘要：As-doped p-ZnO films were grown by photo-assisted metal-organic chemical vapor deposition (PA-MOCVD) system on n-SiC(6H) substrate and the p-ZnO/n-SiC heterojunction device was fabricated. The structural and optical properties of the As-doped ZnO film have been studied by X-ray diffraction (XRD) and photoluminescence (PL) measurements. A typical p-n junction rectification behavior was acquired with a turn-on voltage of 5.0 V and a reverse breakdown voltage of about －13 V. Under forward bias, two obvious emission peaks at ultraviolet (UV) and visible regions were detected. By comparing with the PL spectra of ZnO and SiC, the origin of the UV and visible emission peaks was confirmed from the radiative recombination of ZnO side.关键词：As-doping;p-ZnO/n-SiC;EL;MOCVD97|132|1更新时间：2020-08-12
- 摘要：The effect of AlN interlayer on strain states and its effect on optical properties of a-AlGaN epilayers grown by using metal organic chemical vapor deposition (MOCVD) method are investigated. The strain is characterized by the frequency shift based on Raman spectroscopy measurement. The results show that residual strain in a-AlGaN grown on the AlN interlayer is relaxed due to AlN interlayer act as a stable and compliant substrate induced weakening of mechanical strength. Accordingly, the near band edge emission (NBE) peak shows red shift in room temperature photoluminescence measurement. In addition, the introduction of AlN interlayer lead to the red shift of NBE photo-luminescence peaks, which can be contribute to the strain determined by Raman spectra.关键词：a-plane AlGaN;AlN interlayer;strain;raman spectra;PL116|89|1更新时间：2020-08-12
- 摘要：The effect of the output power on difference passivation facet in 980 nm graded index waveguide structure InGaAs/AlGaAs laser diodes was studied. The output power of the 980 nm laser diodes with no facet passivation, Si passivation, and ZnSe passivation at the front and the back facet were compared. The test results show that output power of the ZnSe passivation method is 11% higher than Si passivation method, and is 42% higher than no facet passivation. The laser diode of no facet passivation is failure at the current is 4.1 A, the Si passivation is 5.1 A, ZnSe passivation is 5.6 A. The reasons of failure for difference passivation were analyzed. In conclusion, the method of ZnSe passivation facet can increase the output power of semiconductor lasers.关键词：laser diode;facet;passivation154|193|2更新时间：2020-08-12
- 摘要：Polarization characteristics of 980 nm large-aperture top-emitting vertical-cavity surface-emitting lasers (VCSEL) with rectangular post were investigated for achieving high-power polarized laser. The experimental results showed that, for the rectangular-shaped VCSEL with 400 μm×80 μm output aperture, both H-polarization (horizontal) and V-polarization (vertical) coexisted in the entire range of operation current, and H-polarization always dominated over V-polarization. Blue-shift of H-polarization light occurred with respect to V-polarization. The experimental results for power and spectrum polarization are consistent with the theoretical calculation. It was proved that the polarization direction of large-aperture VCSEL can be preferably stabilized by the rectangular structure. The horizontal and vertical beam divergences were 6.9° and 10.2° in the rectangular-shaped VCSEL, respectively.关键词：vertical-cavity surface-emitting lasers (VCSEL);polarization;rectangle;blue-shift;large-aperture104|194|0更新时间：2020-08-12
- 摘要：Two typical types of substrate materials, i.e., ceramic substrates without insulating layer and metal substrate with insulating layer were studied for the thermal management of COB package. Their chip-to-substrate thermal resistances were simulated and calculated by finite element method. Temperature distribution in two substrates was obtained by infrared thermography, which confirmed the adopted finite element method is feasible in our experiment. Based on these studies, the thermal management of COB package was optimized by finite element simulation. The results show that the ceramic substrate has a lower chip-to-substrate thermal resistance (only half of that of the metal substrate), which indicate that it is more suitable for the heat dissipation in high-power LED package.关键词：COB package;finite element analysis;thermal simulation131|262|6更新时间：2020-08-12
- 摘要：The poly(3-hexylthiophene): -phenyl C61-butyric acid methyl ester (P3HT ∶PCBM) bulk-heterojunction polymer solar cells fabricated with doctor-blade coating were studied. It is found that the active layer thickness increases with increasing the coating speed or lowing substrate temperature, which is attributed to the changes of solution viscosity and surface tension. Moreover, the P3HT ∶PCBM active layer produced by doctor-blade coating demonstrates fine donor-acceptor nanoscale phase separation favoring enhancing exciton dissociation and charge collection. A 4.2% P3HT ∶PCBM solar cell was fabricated with doctor-blade coating technique.关键词：doctor-blade coating;polymer photovoltaic cells;energy transfer efficiency142|353|2更新时间：2020-08-12
- 摘要：The color purity of organic light-emitting devices is restricted mostly by the intrinsic character of emitting material, but optical cavity can improve the color purity via changing the structure of devices. In this paper, we demonstrated that highly saturated homo-chromaticity light can be obtained by adjusting the thickness of organic layers. Organic top-emitting electroluminescent devices were fabricated in this method, the structure of the device was Ag/m-MTDATA/NPB/DPVBi/Alq3/(LiF/Al/Ag),and direct blue emission with Commission Internationale de L’Eclairage chromaticity coordinates of (0.14,0.07) was obtained.关键词：optical microcavity;blue light;top-emitting;color purity126|239|1更新时间：2020-08-12
- 摘要：ZnO nanowire arrays with controlled diameter, density and orientation were prepared on the ZnO film coated substrates via hydrothermal method. The ZnO film were fabricated by atomic layer deposition (ALD) method and annealed at different temperatures. The annealing temperature has strong influences on the grain size, crystalline structure and defect property of the ZnO film. The diameter, density and orientation of ZnO nanowires depended on the features of the ZnO film. Field-emission scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL) were applied to analyze the ZnO film and ZnO nanowire arrays. The as-prepared vertical aligned ZnO nanowires are highly suitable for use in nanodevices, such as light-emitting diodes and solar cells.关键词：ZnO;hydrothermal method;nanowire array;diameter;density117|210|1更新时间：2020-08-12
- 摘要：The interaction of mecobalamin and bovine serum albumin (BSA) was studied by fluorescence spectroscopy, ultraviolet absorption spectroscopy and resonance light scattering spectroscopy. The results showed that in pH 7.40 Tris-HCl buffer solution, both the fluorescence and resonance light scattering intensity were quenched when increasing the mecobalamin concentration. According to Stern-Volmer curve, the fluorescence quenching constant was calculated (Ksv=5.40×104, 6.90×104, 8.00×104 L/mol) with the interaction of mecobalamin and BSA at different temperatures (293,303,310 K). At the same time, ultraviolet absorption spectra were characterized. The experimental results indicated that the fluorescence quenching mechanism of mecobalamin with BSA was a dynamic quenching procedure. The binding constants (KA=1.68×104,4.34×104,7.90×104 L/mol), binding sites (n≈1) and the corresponding thermodynamic parameters, namely enthalpy change (ΔH), free energy change (ΔG) and entropy change (ΔS) at different temperatures were calculated (ΔH>0, ΔG<0, and ΔS>0). According to the thermodynamic parameters, during the binding process, spontaneous molecular interaction occurs in which entropy increased and free energy decreased. These indicate the hydrophobic interaction was the main sort of binding force between the reaction of mecobalamin and BSA. In addition, the effect of mecobalamin on the conformation of BSA was analyzed using synchronous fluorescence spectroscopy. The results revealed that mecoba-lamin did not change the conformation of BSA during the reaction.关键词：mecobalamin;bovine serum albumin (BSA);fluorescence spectroscopy;ultraviolet absorption spectroscopy;resonance light scattering76|177|3更新时间：2020-08-12
- 摘要：A rapid and convenient spectrophotometric method for the determination of piperlonguminine was established in the present work. The method utilized charge transfer reaction between piperlonguminine and o-nitrophenyl fluorone in pH 7.00 buffer solution. The maximum absorption wavelength of the charge transfer complex was at 515 nm and the apparent molar absorptivity was 6.571×104 L·mol-1·cm-1 with a 1 ∶1 stoichiometry. Beer’s law was obeyed in the range of 0.054 6~10.92 μg/mL of piperlonguminine with the detection limit of 0.015 3 μg/mL. The reaction mechanism was discussed preliminarily. The proposed method was applied to the biological and urine samples spiked with standard piperlonguminine solution. The recovery of the samples was within the range of 99.8%~100.9% and relative standard deviation (RSD) was 0.90%.关键词：charge transfer reaction;o-nitrophenyl fluorone;piperlonguminine;spectrophotometry102|78|2更新时间：2020-08-12
- 摘要：The interaction between benorilate (BEN) and bovine serum albumin (BSA) was investigated under physiological condition by molecular spectroscopic techniques, including fluorescence spectroscopy, UV-visible spectroscopy, synchronous fluorescence spectroscopy and three-dimensional fluorescence spectroscopy. The intrinsic fluorescence of tryptophan in BSA was significantly quenched by BEN via dynamic quenching. The hydrophobic interaction did favor the interaction of BSA with BEN. The apparent binding constants and binding sites number at the tryptophan site were 1 050 L·mol-1 and 0.88, respectively. Thermodynamic parameters such as enthalpy change (ΔH), entropy change (ΔS) and free energy change (ΔG) were also obtained. The conformation changes of BSA in the presence of BEN were proved by the evidences of synchronous fluorescence spectroscopy and three-dimensional fluorescence spectroscopy. Two site-specific fluorescence probes, dansylamide (DA) and dansyl-L-proline (DP), were employed in competitive binding experiments to monitor the BEN binding sites of BSA. The apparent binding constants at siteⅠand Ⅱ were 4 300 and 21 200 L·mol-1, respectively.关键词：benorilate;bovine serum albumin;fluorescence quenching;thermodynamic parameters;three-dimensional fluorescence spectroscopy132|154|0更新时间：2020-08-12
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