最新刊期
卷 38 ， 期 1 ， 2017
- 摘要：Different emission wavelengths of Pr3+ ion, from the ultraviolet to the infrared, may result from the effects of non-4f states in phosphors. Such non-4f states generally refer to the Pr3+ 4f5d state, exciton-like state or charge-transfer state. Here, we present a brief review on Pr3+ luminescence by the means of emission spectral measurement in several representative phosphors. Several interesting spectral phenomena are reported and reviewed, including the effects of impurity-trapped exciton state and charge-transfer state on the luminescence quenching in the Pr3+-activated phosphors. We expect this review is beneficial to the readers to better understand their experimental findings, and to inspire them to design new and improved phosphor systems.关键词：Pr3+;1S0 emission;1D2 emission;impurity-trapped exciton;charge-transfer state;infrared206|142|1更新时间：2020-08-12
- 摘要：Near-spherical and well crystallized YVO4:Yb3+,Er3+ nanoparticles with tetragonal zircon structure were prepared by co-precipitation method. The average particle size is 80 nm. Under 1 550 and 980 nm excitation, the observed emissions of the particles are similar and locate near 513-573 nm and 634-706 nm corresponding to 2H11/2/4S3/2→4I15/2 and 4F9/2→4I15/2 transitions of Er3+ ions, respectively. By controlling the excitation wavelength, color-tunable and high-purity green and red up-conversion luminescence(UCL) from the same component nanoparticles can be obtained. Under the excitation of 980 nm, the intensity ratio value of green and red emission reaches 29.5. However, when the excitation source is replaced by 1 550 nm diode laser, a bright red emission with high color purity is observed. Here, the maximum value of the intensity ratio of red and green emission is 37.97. Furthermore, the different UCL transition mechanisms of the phosphor excited by 980 nm and 1 550 nm are discussed in detail by means of Er3+ energy model.关键词：up-conversion luminescence;YVO4 nanoparticles;color-tunable;high color purity116|138|5更新时间：2020-08-12
- 摘要：A series phosphors of NaY1-x(MoO4)2:xEu3+ were prepared by a solid-state reaction, and their crystal structure, microstructure and luminescence properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and fluorescence spectrophotometer. The phosphors possess scheelite tetragonal crystal structure with a space group I41/a, the particle size is between 75-260 nm, and the samples show intense peak at 615 nm under the excitation of 466 nm. The decay curves of NaY1-x(MoO4)2:xEu3+, luminescent mechanism and the luminescence branch ratio (R/O) were also studied. The result shows that the concentration of the Eu3+ have small influence on the lifetime of the samples, and the lifetime is about 0.38-0.39 ms, and the R/O ratio decreases with the increase of the Eu3+, so that the symmetry of the samples increases. With the concentration increase of the doped Eu3+, the sample doesn't show concentration quenching clearly, while the phosphor shows thermal quenching obviously through the studied on the temperature stability. All these results suggest that the obtained powder phosphor has potential application in the field of light-emitting diode.关键词：concentration quenching;thermal quenching;luminescent mechanism;NaY (MoO4)2;R/O104|104|2更新时间：2020-08-12
- 摘要：In order to develop a series of fluorescent gel which can be used in pure water, a terbium complex Tb(ACAC)3·2H2O was successfully synthesized using TbCl3·6H2O and acetylacetone as the raw materials, and its structure was characterized by FT-IR. Then, the fluorescence gel was prepared by doping the terbium complex Tb(ACAC)3·2H2O into the PVA matrix with different mass fraction and under the action of cross-linking agent boric acid. The structure, luminescent properties and thermal properties of PVA fluorescent gel were conducted by FT-IR, fluorescence spectrum, DSC and TGA. The results of FT-IR show that the terbium complex has been successfully introduced into PVA gel system. In addition, the PVA fluorescence gels with terbium complex all have good fluorescence properties. Especially, the emission intensity at 545 nm of PVA fluorescent gel is higher than the precursor Tb(ACAC)3·2H2O, is 2.15 times for 3%, 3.27 times for 5%, and 5.65 times for 7%, respectively. These results reveal that the Tb-complex can be effectively sensitized by PVA matrix in this system. In addition, the DSC and TGA results indicate that the introduction of terbium complex has little decrease for the thermal stability of PVA fluorescence gel.关键词：terbium complex;PVA;fluorescence gel;luminescent properties113|445|0更新时间：2020-08-12
- 摘要：By using sol-gel method, Zn and Cu co-doped TiO2:SiO2 gel was prepared and coated on glass substrates by spin coating method. Under the same experimental conditions, the effects of the different doped proportion of Zn and Cu, calcined temperature and time on the structure, morphology and property of Zn and Cu co-doped TiO2:SiO2 films were discussed. By using XRD, FESEM, FTIR etc., the films were characterized and the photocatalytic degradation performances on methyl orange were researched. XRD patterns demonstrate that the films are anatase structure and have high crystallization. SEM images show that the film surface has no crack and its particles have small size. UV-Vis absorption spectra indicate that the absorbance of the film is very high in the visible and ultraviolet region. The degradation experiments under UV light illustrate that the photocatalysis degradation efficiency of the film on methyl orange increases greatly compare with pure TiO2 film. The degradation rate reaches the highest for the film with the molar ratio of n(Ti):n(Si):n(Zn):n(Cu)=3:2:1.5:4 calcined at 600℃ for 2 h.关键词：sol-gel;TiO2:SiO2;co-doped;photocatalysis;thin film115|67|3更新时间：2020-08-12
- 摘要：The flame fusion process was put forward to prepare the Yb2+/Yb3+ co-doped silica glass, and the conversion process between Yb3+ and Yb2+ ions was controlled by increasing the auxiliary heating device. The absorption and emission characteristics of the Yb2+/Yb3+ co-doped silica glass prepared with different conditions were studied. Because of 4f14→4f135d1 energy transition of Yb2+ ions, Yb2+/Yb3+ co-doped silica glass prepared with auxiliary heating has stronger absorption intensity and more absorption peak, and the tail of the absorption spectrum extends to the longer wavelength. At the same time, the typical absorption characteristics of Yb3+ ions can also be observed. The emission peak of Yb2+/Yb3+ co-doped silica glass prepared with auxiliary heating locates around 530 nm. The CIE coordinate (0.332 2, 0.476 7) of Yb2+/Yb3+ co-doped silica glass lies within the band of white-light illumination. The results indicate that Yb2+/Yb3+ co-doped silica glass can act as suitable material for white phosphors.关键词：flame fusion process;Yb2+/Yb3+co-doped silica glass;absorption characteristics;emission characteristics;white light source91|51|0更新时间：2020-08-12
- 摘要：Novel Tb3+ or Ce3+ doped and Tb3+/Ce3+ codoped Gd-Ba-silicate scintillating glasses were synthesized by melt-quenching method. The luminescence properties were studied by transmission spectra, photoluminescence excitation and emission spectra, X-ray excited luminescence spectra and luminescence decay curves. The results show that Tb3+ doped scintillating glasses exhibit bright green emission at about 544 nm and Ce3+ doped scintillating glasses have a strong purplish-blue light under ultraviolet excitation. For Tb3+/Ce3+ codoped scintillating glasses, Ce3+ ions can strongly sensitize the luminescence of Tb3+ ions under both UV and X-ray excitation, which is caused by the energy transfer process from Ce3+ to Tb3+ ions. The optimal doping mole fraction of Ce2O3 in Tb3+/Ce3+ codoped scintillating glasses was 0.2%. In this case, the evaluated energy transfer efficiency from Ce3+ to Tb3+ is about 45.7%. Under X-ray excitation, not only the intensity of 544 nm emission in Tb3+/Ce3+ codoped scintillating glasses with 0.2% of Ce2O3 was 4.2 times than that of 500 nm emission in the commercial Bi4Ge3O12(BGO) crystals, but also the integral scintillation efficiency was about 55.6% of the BGO crystals. It is beneficial for reducing radiative dose to obtain high-resolution medical X-ray imaging.关键词：scintillating glass;Ce3+ doped;Tb3+ doped;energy transfer138|106|3更新时间：2020-08-12
- 摘要：In order to realize the characterization of smaller beam spot in the research of associated particle, a kind of modular fluorescence target by using YAG:Ce3+ was designed, and a kind of real-time monitor and measurement approach was presented. By using this approach, the maximum diameter of the beam spot reaches 4 mm. After engraving into array form by laser in the replaceable fluorescence target surface, the monitor and measurement accuracy of the beam spot size is millimeter level, even is sub millimeter level. After bombarding by high energy ion beam for a long time, YAG:Ce3+ can keep on shining without performance degradation, which means YAG:Ce3+ has good radiation-resistant performance.关键词：associated particle neutron tube;small beam spot;YAG:Ce3+ phosphor;fluorescence target;radiation-resistance113|537|0更新时间：2020-08-12
- 摘要：The transparent Ga2O3-GeO2-Na2O glasses doped with Tm3+/Er3+/Yb3+ were prepared by melting quenching method. The effects of Tm2O3 contents on the visible and infrared spectra of the samples under 808 and 980 nm excitation were compared. The mechanisms of energy transfer between Tm3+, Er3+ and Yb3+ ions were analyzed combining with the energy level of rare earth ions. The results show that the obvious blue (473 nm), red (655 nm), green (521 and 544 nm) emission can be observed in Tm3+/Er3+/Yb3+-codoped sample. I1.8/I1.53(intensity ratio of Tm3+:1 800 nm and Er3+:1 530 nm) are enhanced and the red and green upconversion emission intensities under the excitation of 808 nm are adjusted due to the efficient energy transfer between Er3+ and Tm3+ with the increase of Tm3+ concentration. Correspondently, the emission intensity of 473, 521 and 655 nm show a trend of firstly increasing and then decreasing, and achieve the maximum value when the mole fraction of Tm2O3 is up to 0.3%. The upconversion red, green and blue emission intensity under 980 nm excitation is higher than that of 808 nm because of the sensitizing effect of Yb3+ to Er3+ and Tm3+.关键词：Ga2O3-GeO2-Na2O glass;Tm3+/Yb3+/Er3+;spectroscopic properties;energy transfer99|47|1更新时间：2020-08-12
- 摘要：The optical and electrical properties of 270/290/330 nm AlGaN-based deep ultraviolet (UV) light-emitting diodes (LEDs) with different Al content in quantum wells and barriers were investigated systematically. Based on the experimental and numerical study, It is observed that the UV LEDs with longer wavelength and lower Al composition in AlGaN multiple quantum wells (MQWs) possess less dislocation density, higher light output power and internal quantum efficiency. The large ideality factors calculated from I-V curves and simulated energy band profiles indicate that the current in the deep UV LEDs with high Al content is dominated by tunneling mechanism, which is attribute to the resulting potential drop in the active region caused by large polarization field in AlGaN MQWs.关键词：AlGaN;deep ultraviolet;light-emitting diodes (LEDs);numerical simulation107|96|1更新时间：2020-08-12
- 摘要：By measuring the photocurrent, we directly observed the relationship between the degree of carrier leakage and the temperature in InGaN multiple quantum wells. When LED's working temperature rises from room temperature to 360 K, the photocurrent increases under the same light intensity. The increase of the sample's photocurrent means larger amount of carrier leakage when the temperature rises. At the same time, it is found that the carriers leak more in a lower density, and the increase of photocurrent is related to the emission photon energy. The model of quantum well-quantum dot can explain the phenomena observed in the experiment, such as the rise of temperature shows little influence on carrier leakage when the excitation light wavelength is relatively short, and causes more carrier leakage when the emission light wavelength is longer. Also, this model can well explain that the carriers leak more in a lower density and leak less in a higher density when the temperature rises. The experiment results suggest that the carrier leakage is the dominant mechanism for T-droop effect when the temperature rises from 300 to 360 K.关键词：InGaN/GaN MQWs;light-emitting diodes;carrier leakage;quantum efficiency131|273|2更新时间：2020-08-12
- 摘要：This paper reports pentacene field effect transistors (OFETs) with a gate insulator made of compound Ta2O5-PMMA where PMMA (poly (methyl methacrylate)) is spin-coated onto the top of evaporated layer of Ta2O5. A comparison with devices with only Ta2O5 is presented. The latter not only shows a high surface roughness but also exhibits very low field-effect mobility. These drawbacks can be overcome by depositing a PMMA layer on Ta2O5. The influence of PMMA thickness in the range 20-60 nm is presented. The results show that when the thickness of PMMA is approximately 40 nm, the electrical performance of OFETs is optimal. Compared with conventional OFETs, the field-effect mobility increases from 4.2×10-2 to 0.31 cm2/(V·s), and the on/off current ratio increases from 2.9×102 to 2.9×105 when the gate voltage increases to -20 V.关键词：Ta2O5-PMMA;insulator;OFETs;mobility;on/off current ratio93|86|0更新时间：2020-08-12
- 摘要：The organic light-emitting display is quite sensitive to vapor and oxygen, which would react with organic functional layer and electrode material after permeating through the OLED device, therefore influencing the working life and stability of the device. This research will combine chloride desiccant and cheaper cationic filmogen to produce a kind of desiccant film, which would have better film-forming property and moisture absorption performance. After 240 h, the brightness of devices with desiccant film is 103.5%, 83.3% and 119.8% of the average, the efficiency of devices is 130.7%, 65.6% and 126.0% of the average, respectively. Compared with the traditional desiccants, it seems that the encapsulation with the desiccant film is a simple and efficient way to improve the performance of OLED and delay its degradation.关键词：organic light-emitting diode (OLED);desiccant film;encapsulation196|159|6更新时间：2020-08-12
- 摘要：In view of carrier injection unbalance problem of the quantum dot light emitting diode (QLED), the injection rate of holes and electrons in the quantum dots (QDs) layer was studied. QLED with structure of ITO/PEDOT:PSS/Poly-TPD/QDs/Alq3 was fabricated. The experiment results show that all the devices exhibit red light and the turn-on voltage rises as the Alq3 thickness increases from 25 nm to 45 nm. When the Alq3 thickness is 30 nm, the current efficiency of the device is high and the injection rate of holes and electrons in the QDs layer reaches a relative balance. Then, the luminescence properties of the devices were further studied through imbedding an electron blocking layer TPD into the QDs/Alq3 interface. When the TPD thickness is 1 nm, the device still exhibits red light, and green light begins to appear when the TPD thickness is 3 nm and 5 nm. The experiment results show that a thinner thickness and lower LUMO should be chosen for the electron blocking layer.关键词：quantum dot light emitting diode;thickness;energy level;current density;luminance;current efficiency127|190|3更新时间：2020-08-12
- 摘要：The quantum-dots (QDs) light guide plate (LGP) was prepared with red quantum dots (R-QDs), green quantum dots (G-QDs) and ink on the surface of PMMA by screen printing. The red and green light emitted from R-QDs and G-QDs which were excited by the side blue LED. The white light was achieved by adjusting the proportion of the QDs in the mixture and optimizing the ratio of R-QDs and G-QDs. The morphology was characterized by OLYMPUS microscope. The LGP optical properties were investigated by F-4600 fluorescence spectrophotometer and SRC-200M spectrum color luminance meter. The results showed that white light could be achieved when the QDs was 7% in the mixture and the ratio of R-QDs/G-QDs was 1:12, which showed the CIE 1931 color coordinates of (0.330 8, 0.327 1), CCT of 5 588 K, brightness of 4 136 cd/m2, and a color gamut of 122.4% NTSC.关键词：quantum dots;white light;screen printing;CCT;brightness;color gamut129|156|2更新时间：2020-08-12
- 摘要：Aiming at the heat dissipation problem of the high power remote phosphor white LED, the heat dissipation method of the package structure was studied. Based on the structure of the phosphor type white LED package and its characteristics of heat dissipation, a thermal managing method of the package was put forward, which both thermally insulated the chip and the phosphor layer and created a independent thermal dissipation path for the phosphor layer. The simulation results show that the redesigned package reduces the chip temperature by 0.55℃ and the phosphor layer temperature by 10.7℃ under the same boundary condition, indicating that the new design can reduce the phosphor layer temperature without increasing the radius dimension of the package. The effect of the thermal isolation groove on the chip base can be ignored. To achieve the optimal chip and phosphor layer temperatures distribution, the thickness of the insulation layer between the chip and the phosphor should be optimized. The new method makes the thermal management problems of the chip and the phosphor layer independent to each other, which avoids the mutual heating problems of the two, and also increases the optical design freedom of the lamp.关键词：LED lamp;phosphor;thermal design;package132|102|8更新时间：2020-08-12
- 摘要：In order to study the properties of gas breakdown while plasma occurs, the threshold value was calculated according to the model of field strength threshold under the lower atmospheric pressure. Six kinds of common discharge gases including helium, neon, argon, krypton, xenon, and mercury vapor were taken into account. Moreover, the related change rule was analyzed and described with the incident frequency, electron temperature, gas pressure, and gas temperature considered. The results show that the gas breakdown threshold is affected by the four factors mentioned above. On the one hand, it decreases while the gas pressure increases. On the other hand, it increases with the gas temperature, electron temperature, and incident frequency increasing. The effects of the gas pressure and incident frequency play more of a role than that of gas temperature and electron temperature. The value of breakdown threshold changes about 100 V/m due to the influence of gas pressure. Similarly, it changes 50 V/m to 300 V/m, and 20 V/m to 30 V/m with the effects of incident frequency and gas or electron temperature thought about. What's more, the change rule is found to be similar for all kinds of charge gases when the effects of gas pressure, gas temperature, and electron temperature are thought over. But it varies while the incident frequency is considered. In addition, xenon has the smallest threshold value while helium having the largest one among the gases studied.关键词：gas breakdown;breakdown threshold;plasma;EMP defense110|439|4更新时间：2020-08-12
- 摘要：This paper presents a soil near-infrared spectroscopy prediction model based on sparse representation and radial basis function neural. The model first makes the soil near-infrared large spectroscopy data to be sparse, then the model uses radial basis function neural network with sparse representation coefficients as input and the measured soil composition value by chemical methods as output to establish effective nonlinear predictive model of soil organic matter, available phosphorus and potassium respectively. The results show that the model is feasible to predict soil organic matter content, but the model needs to be further optimized on the soil phosphorus or potassium effective prediction.关键词：near-infrared spectroscopy;deep sparse learning;neural network model209|200|9更新时间：2020-08-12
- 摘要：With crystal giucose as raw material, the carbon quantum dots were synthesized through one-step hydrothermal method. The surface of the carbon quantum dot was amino modificated using ethylenediamine. Pyrogallic acid can cause the fluorescence quenching effect of the amino-functional carbon quantum dots more obvious, hereby, a simple and efficient method to measure the pyrogallic acid was established. Different influencing factors were studied including pH buffer system, reaction time, reation temperature and so on. The results show that F0/F of the system has linear relationship with the concentration of the pyrogallic acid in Britton-Robinson buffer solution with pH=11.20 and the reaction time of 20 min at room temperature. The linear range is 4.0×10-6-9.0×10-5 mol·L-1, the correlation coefficient r is 0.997 4, and the detection limit is 3.5×10-6 mol·L-1, respectively. The method is simple and applicable to the determination of pyrogallic acid in water samples with satisfactory results.关键词：amino-functional carbon quantum dots;pyrogallic acid;fluorescence quenching124|313|2更新时间：2020-08-12
- 摘要：A label-free fluorescence method based on the fluorescence property of graphene quantum dots (GQDs) was developed for sensitive and selective detection of ascorbic acid (AA). The initial strong blue fluorescence of the GQDs in aqueous solution was effectively quenched upon addition of AA. The quenching mechanism may involve transfer of electrons from AA to GQDs via the redox reaction of AA and GQDs in weak acid solution. The quenching efficiency was linearly proportional to the concentration of AA within the range of 5.0×10-6-7.5×10-5 mol/L with a low detection limit down to 1.0×10-6 mol/L. The proposed sensing system is simple and low-cost with facile experimental operations, and has a high selectivity for AA over a number of possible interfering species. Additionally, this method was successfully applied to the determination of AA in biological samples with satisfactory recoveries (95.2%-115.3%).关键词：graphene quantum dots;fluorescence probe;label-free method;ascorbic acid130|171|1更新时间：2020-08-12
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