最新刊期
卷 32 ， 期 11 ， 2011
- 摘要：LaF3 Crystalline powders doped with Ho3+and Yb3+ were prepared by co-precipitation method. The samples were characterized by XRD. Single-phase LaF3∶Ho3+, Yb3+ powders with hexagon structure were obtained in our experimental process. Excitation spectra, emission spectra, and decay curves were used to characterize the samples at room temperature. The energy transfer from Ho3+ to Yb3+ was confirmed. Further it is recognized as a resonant energy transfer process. Through the process, the samples could absorb ultraviolet photons with 300~360 nm band and emit two near-infrared photons around 1 m. This result reveals the possibility of violet to near-infrared quantum cutting with a quantum efficiency larger than 100% in Ho3+/ Yb3+ co-doped fluorides, suggesting the possible application in modifying the solar spectrum to enhance the efficiency of silicon solar cells.关键词：rare earth luminescent materials;near-infrared quantum cutting;Ho3+ sensitizer;solar cells153|101|0更新时间：2020-08-12
- 摘要：Y0.8-x-yF3∶Gdx3+, Yb0.23+,Tmy3+ nanocrystals were synthesized through a hydrothermal method. The upconversion(UC) emission properties under a 980 nm continuous wave semiconductor laser diode excitation were studied. The experimental results suggested that the violet and ultraviolet(UV) UC emission enhancement were observed in Y0.595F3∶Gd0.2003+,Yb0.2003+,Tm0.0053+ nanocrystal,as well as the UC emissions of Gd3+ of 6D9/2,6IJ,6P5/2,and 6P7/2 states to the ground state 8S7/2 were shown,too. The luminescent kinetic analysis implied that,under 980 nm excitation,Yb3+ can transfer energy to populate the 3P2 level of Tm3+,make UV,violet,and blue UC emissions obtained,further,the 6IJ multiplets of Gd3+ were populated through the energy transfer process 3P2→3H6(Tm3+):8S7/2→6IJ(Gd3+). At the same time,the energy transfer processes occurred between Gd3+ and Yb3+ or Tm3+ based on the energy matching conditions, leading to the above mentioned UV UC emissions of Gd3+.关键词：rare earth;fluoride;nanocrystal;up-conversion emission104|91|0更新时间：2020-08-12
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The Effect of Doping Sr2+ on Enhancement of Red Emission of Y2.78-xSrxGd0.1Al5O12∶0.06Ce3+ Phosphors
摘要：Y2.78-xSrxGd0.1Al5O12∶0.06Ce3+ phosphors were synthesized by co-precipitation method. The crystalline structure and Spectra properties of Y2.78-xSrxGd0.1Al5O12∶0.06Ce3+ phosphors were investigated by X-ray diffraction(XRD) and fluorescence spectrophotometer. The color temperatures of the white LEDs fabricated with blue chip and as-prepared phosphors were studied by HSP-6000 optical spectrum analyzer. It is found that the mole fraction of Sr2+ has obvious influences on the emission wavelength and intensity of as-prepared phosphors. The emission wavelengths of as-prepared phosphors display red-shift at first and then blue-shift appear with the molar of Sr2+ increasing. The emission intensity hardly decreases with Sr2+ mole fraction when it is below 0.05. And then the intensity decreases slowly with the mole fraction of Sr2+ increasing from 0.05 to 0.1, but decreases sharply when the mole fraction of Sr2+ is above 0.1. With the increase of mole fraction of Sr2+, the color temperatures of white light decrease at first, and then increase owing to the interaction of emission wavelength and intensity. When the mole fraction of Sr2+ exceeds 0.2, the impure phase-A appears which has negative effects on the luminescence property of as-prepared phosphors.关键词：Y2.78-xSrxGd0.1Al5O12∶0.06Ce3+phosphors;red-shift;co-precipitation method118|108|3更新时间：2020-08-12 - 摘要：The different YAG∶Ce3+ precursors were prepared via normal and ultrasonic co-precipitation method by forward-titration and reverse-titration technique. The phosphor synthesized by sintering precursor was characterized by XRD, SEM, laser diffraction particle size analyzer and fluorescence spectrophotometer. The results showed that, the samples were all pure phase yttrium aluminum garnet structure. The YAG∶Ce3+ phosphor prepared through reverse-titration technique had higher luminous intensity than through forward-titration technique. And in both techniques, phosphor prepared by ultrasonic co-precipitation method had a more uniform grain size, a narrower particle size distribution and a higher luminous intensity compared to normal co-precipitation condition.关键词：YAG∶Ce3+ phosphor;ultrasonic co-precipitation;forward-titration;reverse-titration117|114|0更新时间：2020-08-12
- 摘要：A novel phosphor Na4Ca3(AlO2)10∶Eu2+ was prepared by solid state reaction method in a thermal-carbon reducing atmosphere. The photoluminescence(PL) properties were investigated in this paper. The excitation spectrum of Na4Ca3(AlO2)10∶Eu2+ showed two absorption bands centered at 262 nm and 320 nm respectively. The photoluminescence spectrum of Na4Ca3(AlO2)10∶Eu2+ exhibited a single emission peak centered at 441 nm, which could be attributed to 5d-4f transition of Eu2+. The excitation spectrum of Na4Ca3-(AlO2)10∶Mn2+ showed absorption peak at about 440 nm monitoring at 542 nm, which shows spectral overlap between emission spectrum of Na4Ca3(AlO2)10∶Eu2+. Co-doped Mn2+ with Eu2+, the photoluminescence spectra of Na4Ca3(AlO2)10∶Eu2+,Mn2+ were observed two peaks centered at 441 nm and 542 nm correspon-ding to the 5d-4f transition of Eu2+ and the d-d transition of Mn2+, respectively. With increasing the concentration of Mn2+, the emission intensity of 5d-4f transition of Eu2+ at 441 nm was significantly decreased, whereas the d-d transition of Mn2+ at 542 nm was found to increase. The decay lifetime for Eu2+ was found to decrease with increasing Mn2+ dopant content, which was strong evidence for the energy transfer from Eu2+ to Mn2+. We were also interested in investigating the energy transfer efficiency ηT of Eu2+→Mn2+. With increasing Mn2+ dopant content, the energy transfer efficiency ηT was found to increase gradually. According to the Dexter's energy transfer formula of multipolar interaction, it was demonstrated that the energy transfer from Eu2+ to Mn2+ was due to the electric quadripole-quadripole interaction of the resonance transfer. According to the CIE chromaticity coordinates of Na4Ca3(AlO2)10∶Eu2+,xMn2+, it was clearly observed that the CIE chromaticity coordinates with the increase of Mn content shifted from blue region to white region.关键词：Na4Ca3(AlO2)10∶Eu2+;Mn2+;energy transfer;decay time127|176|0更新时间：2020-08-12
- 摘要：The title compound, 3-(3,5-dichlorobenzylideneamino)benzoic acid was obtained by the condensation of 3-aminobenzoic acid and 3,5-dichlorosalicylaldehyde, and the structure of it was determined by 1H NMR, IR, and high-resolution mass spectra. We have studied its fluorescence performance and thermal stability. The UV and fluorescence spectrums reveal that the title compound possesses favorable properties of photochromism and thermochromism in DMF solution. The analysis also shows that there is a linear relationship between its absorbance and time or temperature, which further demonstrate its photo-and thermochromic properties.关键词：Schiff bases;photochromism;thermochromism136|151|0更新时间：2020-08-12
- 摘要：In order to reduce thermal loss due to spectral mismatch of the solar cell absorption,the quantum cutting with Tb3+-Er3+ couples as spectral converters is experimentally observed. One high energy ultraviolet photon(7F6→5L1 of Tb3+) is quantumly cut into two lower energy photons:one is in near-infrared(4I9/2→4I15 of Er3+) and the other in blue region(5D4→7F6 of Tb3+), both of which can be efficiently absorbed by solar cells. A quantum efficiency, ηQE of up to 188% is calculated which is close to the theoretical limit of 200%. The energy mismatch in the energy transfer from Tb3+(5L1→5D4)to Er3+(4I9/2→4I15/2) is 237 cm-1, less than a phonon energy of 400 cm-1 in NaYF4, making the energy transfer nearly resonant. The energy migration among Tb3+ donors is treated approximately by the diffusion model and the initial process of energy transfer among the Tb3+-Er3+ couples is found to be dipole-dipole interactions.关键词：Tb3+-Er3+ couples;spectral converters;quantum cutting;quantum efficiency100|72|1更新时间：2020-08-12
- 摘要：A type of spirofluorene, DCSF, was successfully synthesized through a series of organic reactions, and determined by 1H NMR、13C NMR、MS、FT-IR. Optoelectric properties were researched by UV-Vis absorption spectra and fluorescence spectra. The photoluminescence quantum yield was measured by the relative comparison method, using quinine sulfate in 0.05 mol/L H2SO4 as standard, which was measured to be 0.391.The energy gap of the HOMO energy and LUMO energy was calculated through cyclic voltammeter measurement, which was estimated to be 3.32 eV.关键词：spirofluorene;blue light-emitting materials;photoluminescence quantum yield;optoelectric properties128|332|0更新时间：2020-08-12
- 摘要：MgAl2O4∶xMn2+ phosphors with various Mn2+ mole fraction x has been synthesized by high temperature solid-state reaction method. Upon blue excitation at 450 nm, the green emission band at 520 nm of Mn2+ reaches the maximal intensity at x = 10%. Our study indicates that there is no considerable concentration quenching for x higher than 10%. The decrease of luminescence for x＞10% is due to more defects generated by Mn2+ introduction. The defects compete with Mn2+ for excitation absorption and also re-absorb luminescence of Mn2+. The temperature induced luminescence enhancement has been observed. The result is well explained in connect with the defects acting as traps basing on diffuse reflection spectra at different temperatures.关键词：concentration quenching;thermal quenching;MgAl2O4;blue excitation;energy conversion137|86|0更新时间：2020-08-12
- 摘要：Gd2-xEux(MoO4)3 red phosphors are synthesized by using co-precipitation method. X-ray diffraction (XRD), scanning electron microscopy (SEM) and fluorescence spectrum are used to characterize the structure and luminescent property of the samples. The luminescent properties of Gd2-xEux(MoO4)3 with various concentration of Eu3+ are investigated in detail. The results show that three dominant bands locate at 394, 465, 534 nm. The emission spectra exhibit the most intense emission at 589 nm and 613 nm, especially the later which is corresponding to the 5D0→7F2 transition of the Eu3+. With the increase of the concentration of Eu3+, the luminescent intensity of the phosphors is gradually increased. When x=0.6 (i.e. Gd1.4Eu0.6-(MoO4)3), the luminescent intensity of the red phosphor is the strongest.关键词：Gd2-xEux(MoO4)3 phosphor;co-precipitation method;luminescence117|155|2更新时间：2020-08-12
- 摘要：With the increase of LD application in the field of laser processing, the efficiency of the fiber coupled modular based on diode laser arrays is rather low, which can not meet the need of low costing for laser processing, so it is very important to develop a higher efficiency modular of fiber coupled diode lasers. In this paper, we achieved a higher efficiency fiber coupled module based on 8 single emitter diode lasers providing more than 32.4 W output power from a 200 microns fiber core with an numerical aperture(NA) of 0.22 at 808 nm. Power of each LD can reach to 5 Watts at operation current. More than 83% coupling efficiency of the modular has been realized. This high power LD module can be used in laser plastics processing and laser meclical treatment fields.关键词：single emitter diode laser;high efficiency;fiber coupling;beam combination126|399|14更新时间：2020-08-12
- 摘要：Green InGaN/GaN multiple quantum well(MQW) LEDs employing InGaN/GaN superlattice(SL) structure were studied. The distribution of indium within the MQWs is changed by inserting the InGaN/GaN SL. Meanwhile, the average indium content of MQW does not change. Two InGaN-related peaks that were clearly found in the electroluminescence(EL) and photoluminescence(PL) spectrum, which are assigned to In-rich quantum dots(QD) and the InGaN matrix, respectively. It is suggested that the carrier drifts from the InGaN matrix to the In-rich QD. It could be concluded that employing SL structures is an effective way to adjust the wavelength of InGaN/GaN MQW without introducing new defects in the MQWs.关键词：InGaN/GaN multi-quantum wells;superlattices;electroluminescence;photoluminescence124|392|1更新时间：2020-08-12
- 摘要：The optical properties of a 2D liquid crystal-metal photonic crystal waveguide is analyzed with the FDTD method. A 2D square lattice metal photonic crystal waveguide lies between two electrodes filled with liquid crystal. By introducing different voltages to the electrodes, the orientation of the liquid crystal can be induced thus to change the refractive index of the liquid crystal, which varies the band structure of the photonic crystal. Numerical results show that the optical properties of the metal photonic crystal waveguide can be modulated by the voltage adjustment. This photonic crystal waveguide can be used in making optical switches and other optical devices.关键词：2D photonic crystal waveguide;finite difference time domain (FDTD);metal;liquid crystal127|193|2更新时间：2020-08-12
- 摘要：Ultra-thin hydrogenated amorphous germanium films, with various thickness from 160 nm to 5 nm were grown by plasma enhanced chemical vapor deposition technique. The film structure was characterized by Raman spectroscopy, which exhibited a broad band centered around 280 cm-1 indicating their amorphous nature. The film thickness and optical properties were evaluated by ellipsometer spectroscopy. The measured thickness was well consistent with the pre-designed value and the optical band gap was about 1 eV which slightly increased with the decrease of film thickness. The temperature dependent conductivity of the films was measured. The electronic transport was believed to occur in the extended-states and the corresponding activation energy is about 0.3~0.4 eV. The light emission in infrared region from the films can be detected at low temperature. The sample for 160 nm had a broad luminescence band which can be divided into two sub-bands centered at 0.78 eV and 0.67 eV, respectively. By decreasing the films thickness less than 10 nm, the luminescence band beaome narrower and only a band at 0.8 eV was observed. It may be due to the relatively more hydrogen in the ultrathin films, which passivated the defect states and suppressed the defect-related luminescence. The non-radiative activation energy increased in ultrathin films suggesting the improved efficiency.关键词：amorphous germanium;electric conductivity;optical band gap;photoluminescence119|218|2更新时间：2020-08-12
- 摘要：Heat dissipation of high-power LED is the main bottleneck for its application. In order to better solve the heat dissipation problem, a new cold spray technology is applied to deposit thin copper coating which can make the soldering of LED head with heat sink possible, and this can significantly extend the durability of high-power LED lamp when comparing with current high-power LED lamp using crimped connection with thermal interface material, also can decrease the thermal contact resistance. Better heat dissipation performance of high-power LED has been verified by CAE software simulation and experiments. And with the increase of input power for LED lamps, the temperature difference of the LED chip between soldering and crimping structure also increases, the cooling effect of soldering is more significant. However,at present the thermal conductivity of the copper layer by cold spray is only 160 W/(m·K), which has a great gap with the conventional copper's thermal conductivity 398 W/(m·K), so the cold spray process needs to be further improved.关键词：Cold spray;high-power LED;heat dissipation126|590|4更新时间：2020-08-12
- 摘要：Significant enhanced performance of organic solar cells with F16CuPc as the anode buffer layer was demonstrated. On the one hand, the adopted F16CuPc anode buffer layer leads to the oriented growth of the CuPc molecules, resulting in the increased crystallinity and hence the hole mobility of the CuPc film. On the other hand, a dipole layer can be formed in the F16CuPc/CuPc interface, which can improve the hole extraction efficiency from CuPc to ITO. Owing to these tow effects, the charge carriers collection efficiency was raised, while the series resistance and the photogenerated charge carrier recombination probability were decreased. Consequently, the short-circuit current and the fill factor were increased. Meanwhile, the built-in potential of the devices was also increased by the introduction of F16CuPc, leading to an increased open-circuit voltage.关键词：anode buffer layer;CuPc;F16CuPc;crystallinity122|126|0更新时间：2020-08-12
- 摘要：A highly efficient red-emitting phosphorescent polymer light-emitting diode (Ph-PLED) with a new iridium complex of bis(2-benzo thiophen-2-yl-5-trifluoromethyl-pyridinato-N,C3) iridium(Ⅲ) (acetylacetonate) using poly (n-vinylcarbazole) (PVK) as host material was demonstrated. The PLED offers a maximum external quantum efficiency of 4.5% with an emission peak of 648 nm. The CIE coordinates are (0.71,0.29) and independent from driving current density, indicating an efficient reduction of self-quenching effect at high doping concentrations.关键词：PLEDs;red electrophosphorescence;OLEDs142|96|1更新时间：2020-08-12
- 摘要：The optical and electroluminescent(EL) properties of organic light emitting devices(OLED) with a coupled microcavity(CMC) structure were investigated. CMC is a kind of complicated microcavity. The modeled optical and luminescent properties of the CMC is simplified by treating the passive cavity as a bottom mirror, and consistent with the measured results. The EL spectral radiance of the CMC in the normal direction was enhanced by a factor of 3.6 at peak of 502 nm, 5.6 at peak of 550 nm, and 0.5 at the whole spectrum region comparing with the normal OLED driving at the same current density. The highest current efficiency and luminance of 7.0 cd/A and 22 660 cd/m2 for the CMC were obtained in the normal direction, comparing with those of 4.2 cd/A and 13 600 cd/m2 for the noncavity OLED.关键词：OLED;coupled microcavity;electroluminescence129|162|3更新时间：2020-08-12
- 摘要：The fluorescence spectra overlap of normal serum and hypetriglyceridemia serum will result in low recognition rate. The paper reports a recognition method of hypertriglyceridemia serum using fluorescence spectroscopic analysis based on principal component analysis and probabilistic neural networks. Firstly, fluorescence spectra of normal serum and hypertriglyceridemia serum were measured with the excitation wavelengths of 260, 370, 580 nm. And the sample's initial feature vector was defined according to fluorescence intensities. Secondly, principal component analysis was used to extract the initial feature vector and establish new sample's feature vector according to the cumulate reliability (>95%). Finally, the four-layer probabilistic neural network was founded for serum samples' recognition. Study designed seven groups of experimental scheme by choosing different fluorescence spectrum for recognition effect comparison. The result showed that recognition rates of the normal serum and hypertriglyceridemia serum were 100% and 95% respectively using fluorescence spectra with the excitation wavelengths of 260 nm and 370 nm. The feasibility and effect of the recognition scheme were demonstrated. The study provides an important guidance for developing the recognition technique of hypertriglyceridemia serum using fluorescence spectroscopic analysis based on probabilistic neural networks.关键词：triglyceride;fluorescence spectroscopy;probabilistic neural networks;principal component analysis114|132|1更新时间：2020-08-12
- 摘要：The interaction of an anti-cancer drug camptothecin with salmon sperm DNA was studied by spectroscopic techniques. DNA induced slight hypochromic and bathochromic effects on the UV-Vis absorption spectra of camptothecin, but strong fluorescence quenching of camptothecin, which suggest the formation of ground-state camptothecin-DNA complex. The binding constant and number of binding site were calculated and the main interaction force was determined. The effect of salt, phosphate and negatively charged quencher KI on camptothecin-DNA interaction was investigated and the interaction of camptothecin with double-stranded DNA and single-stranded DNA was compared. The melting temperature of camptothecin-DNA complex was 60 ℃, which is 18 ℃ lower than that of pure DNA. All the results indicate that groove binding mode is the main interaction mode between camptothecin and DNA.关键词：camptothecin;drug-DNA interaction;fluorescence quenching109|286|3更新时间：2020-08-12
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