最新刊期
卷 36 ， 期 12 ， 2015
- 摘要：ALn(MoO4)2:3%Er3+ (A=Na, K; Ln=La, Y) phosphors were prepared via a high temperature solid state reaction, the crystal structure of the obtained phosphors was characterized by XRD technique. The results of photoluminescence spectra indicated that the phosphors could be effectively excited by 380 and 274 nm and evoked downconverion emissions. Temperature quenching behavior was observed in the phosphors under 380 nm excitation. The influence of host on the characteristic temperature of fluorescence emission was studied, and it was found that the host greatly affected the characteristic temperature and that KLa(MoO4)2:3%Er3+ phosphor presented a good luminescence temperature stability. The fluorescence intensity ratio (FIR) was applied to study the temperature sensing property. The host dependence of absolute sensitivity of temperature sensing was investigated and NaY(MoO4)2:3%Er3+ phosphor was confirmed to have higher absolute sensitivity than the others.关键词：ALn(MoO4)2:Er3+;fluorescence temperature quenching;temperature sensing;fluorescence intensity ratio (FIR)130|140|2更新时间：2020-08-12
- 摘要：Localized surface plasmon resonance enhanced n-ZnO/i-ZnO/MgO/p-GaN heterostructure light-emitting diodes (LEDs) with different sliver nanoparticles (Ag NPs) density were fabricated using molecular-beam epitaxy technique. It is found that the introduction of Ag NPs with suitable density is favorable for the effective resonant coupling between excitons in ZnO and the localized surface plasmons of Ag NPs, and thereby significantly improves the electroluminescence (EL) performance of the device. Note that the enhancement ratio increases firstly with the Ag NPs density and then decreases, and the variation is believed to be resulted from balance between the enhancement caused by the resonant coupling between the excitons in ZnO and the localized surface plasmons of Ag NPs and the extinction of the emitted photons by the Ag NPs.关键词：localized surface plasmon resonance;light-emitting diodes;sliver nanoparticles;electroluminescence131|120|4更新时间：2020-08-12
- 摘要：High crystal quality and (002) orientation preferred ZnO microrods were grown by the method of chemical vapor deposition (CVD). The optical properties of ZnO microrod on graphene substrate were investigated. The photoluminescence (PL) spectra revealed that the luminous intensity of ZnO microrod on graphene substrate was enhanced as twice as that without graphene substrate. The distribution of light field in ZnO microrod was also restricted by graphene. These are all caused by grapheme surface plasmon. In the case of ZnO microrod on the graphene substrate, E2(L) and E2(H) Raman intensity decreased dramatically by comparing with which of the ZnO microrod without graphene substrate. This further indicates that there is stronger light-matter interaction at the interface. Hence, the lattice vibration of ZnO microrod was restricted by the graphene.关键词：ZnO microrods;single layer grapheme;photoluminescence;Raman123|211|1更新时间：2020-08-12
- 摘要：Based on the all-quantum theory, the system which includes two double-level atoms interacting with two single-mode cavity fields separately was studied. With making the Markoff and the rotating-wave approximations, using quantum master equation and the numerical simulation, we investigated the influence of the cavity dissipation coefficient and the cavity-cavity coupling coefficient on the mean photon number distribution under the unsteady situation. In the meantime, we discussed how the Mandel's Q parameter and the second-order coherence were changing, and then analyzed the quantum effects of the system. Besides that, we analyzed the spectra of the atoms and the cavities. The results show that the system quantum properties become more obvious by reducing the cavity dissipation coefficient and increasing the coupling coefficient between cavities. The system spectra present Mollow three peak structure, and the atomic emission spectrum intensity is greater than the cavity field spectrum intensity. When the atomic transition frequency and the cavity transition frequency is near resonance, the Mollow peak is the highest of the three peaks. In addition, the spectrum intensity of the atomic middle peak increases with the increasing of the atom-cavity coupling coefficient, and the spectrum intensity of the cavity middle peak is quite opposite.关键词：quantum master equation;double coupling two-level system;sub-Poisson distribution;anti-bunching effect;spontaneous emission spectrum131|71|0更新时间：2020-08-12
- 摘要：Using gadopentetic acid monomeglumine (GdPM) as precursor to provide simultaneously the carbon source and gadolinium (3+) source, gadolinium-doped carbon quantum dots (Gd3+/CQDs-MH) with uniformly small size were obtained at a mild condition by microwave hydrothermal method which can realize a molecular level mixing. When GdPM was pyrolyzed under 250 ℃ for 45 min, Gd3+/CQDs-MH with high quantum yield (QY) and longitudinal relaxation rate (r1) were obtained. The contradiction between quantum yield and the relaxation properties has been well balanced, which is very difficult to avoid using traditional heating method. The prepared Gd3+/CQDs-MH with an average diameter of about 1.0 nm show little cell toxicity and exhibit a high photoluminescence quantum yield of 11.0%, as well as a high r1 value of 4 545.3 mmol-1·L·s-1 ([Gd3+]=0.01 mmol·L-1) with the doping mass fraction of gadolinium (3+) of 16.9%. Therefore, the Gd3+/CQDs-MH show big possibility for application in magnetic resonance/fluorescence bimodal molecular imaging.关键词：carbon quantum dots;gadolinium ions;magnetic resonance;fluorescence;molecular imaging probe156|138|0更新时间：2020-08-12
- 摘要：Uniform NaYF4:Yb3+,Er3+@NaYF4:x%Yb3+ (x=0, 20, 40, 60) nanoparticles were synthesized through thermolysis in oleic acid and 1-octadecene. The upconversion luminescence of these core/shell nanostructures was explored at different temperatures (90-450 K). The results demonstrate that the emission at 525 nm(2H11/2 →4I15/2) of core/inert-shell nanoparticles exhibites a different growth from that of core/active-shell nanoparticles. The upconversion emissions of Yb3+-doped-active-shell nanoparticles are more easily affected by phonons than those nanoparticles coated with inert layer. Yb3+ ions in the shell paly an important role of bridging the iner and outer factors to influence upconversion emission.关键词：upconversion;temperature dependence;energy state population;rare earth154|200|0更新时间：2020-08-12
- 摘要：Ir(ppy)2(acac) with different purity levels were obtained by adopting various thermal gradient vacuum sublimation conditions, and were used as phosphorescence dopants in OLEDs with a structure of ITO:MoO3/CBP/CBP:Ir(ppy)2(acac)/TPBi/LiF/Al, where CBP and TPBi were the abbreviations of 4,4'-N,N'-dicarbazole-biphenyl and 1,3,5-tris(N-phenylbenzimidazole-2-yl) benzene, respectively. The electroluminescent performances of Ir(ppy)2(acac) were evaluated and the effect of purity levels was explored. The results indicate that sublimation improves electroluminescent stability of the device, and a higher purity level endows the device with greater electroluminescent efficiency even at a low doping concentration.关键词：phosphorescent iridium complex;purity;electroluminescent performance;OLED;effect115|137|2更新时间：2020-08-12
- 摘要：Na2TiF6:Mn4+ red phosphors with different Mn4+ doping mole fraction were synthesized by the co-precipitation method. Structure, morphology, photoluminescence excitation and emission spectra as well as decay curve of Na2TiF6:Mn4+ phosphors were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR) and fluorescence spectrometer. As-prepared Na2TiF6:Mn4+ phosphors have hexagonal structures. Under 460 nm excitation, intense red emissions corresponding to 2Eg-4A2 transitions of Mn4+ are observed. The optimum doping mole fraction of Mn4+ is 4.77% and the quantum efficiency is 74% for this phosphor. The chromaticity coordinates of the Na2TiF6:Mn4+ phosphors are (0.681, 0.317). Decay curve of 2Eg state for as-prepared Na2TiF6:Mn4+ sample fits the second order exponential behavior, and the average lifetime is 3.148 ms.关键词：Na2TiF6:Mn4+;red phosphor;white LEDs;co-precipitation197|256|5更新时间：2020-08-12
- 摘要：Poly[(9,9-bis(3'-propanoate)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PF8COOH) was synthesized by Suzuki coupling, and carboxylated polyfluorene/titanium dioxide (TiO2) hybrid materials were prepared through sol-gel method. The polymer and its hybrid materials were characterized by 1H NMR, gel permeation chromatography (GPC), ultraviolet-visible spectroscopy (UV-Vis), X-ray diffraction (XRD), and photoluminescence spectra. The fluorescence quenching behavior of the hybrid materials was investigated. The results indicate that the number-average molecular weight of PF8COOH is 19 600, the UV-Vis absorption and the photoluminescence spectra of PF8COOH show a red shift relative to poly(9,9-dioctylfluorene)(PF8). PF8COOH/TiO2 hybrid materials are prepared through sol-gel method. TiO2 mainly has rutile crystal structure in the hybrid materials. Fluorescence quenching phenomenon can be obviously observed in the hybrid materials, and the greater TiO2 content is, the more obvious the fluorescence quenching phenomenon in the hybrid materials is. Moreover, the interaction between polyfluorene and TiO2 can be enhanced as carboxyl being introduced and electrons can transfer from polyfluorene to TiO2 more easily, thus the fluorescence quenching phenomenon of PF8COOH/TiO2 hybrid materials is more obvious than that of PF8/TiO2 hybrid materials.关键词：carboxylated polyfluorene;titanium dioxide;hybrid materials;fluorescence quenching;electron transfer118|245|0更新时间：2020-08-12
- 摘要：The phosphors Ba2SiO4:xCe3+,yMn2+(x=0-0.2, y=0-0.15) were synthesized through the solid-state reaction technique. The structure, photoluminescence properties of these phosphors were described. Under the excitation of UV light, the emission spectra of Ba2SiO4:xCe3+ show broad band around 384 nm. The emission spectra of Ba2SiO4: Mn2+ show broad band around 376 nm, and the red emission is very weak. The red emission band located at around 606 nm is strongly enhanced in Ba2SiO4:xCe3+,yMn2+, which is arised from 4T1(4G)-6A1(6S) transition of Mn2+. The results show that a part of the energy of Ce3+ ion is transferred to Mn2+ ion and sensitizes the luminescence of Mn2+ ion effectively. When the mole fractions of Ce3+ and Mn2+ are 0.2 and 0.075, the red emission around 606 nm is the strongest.关键词：phosphor;photoluminescence;energy transfer174|110|0更新时间：2020-08-12
- 摘要：Based on the red and green/blue light emitting layer, six white phosphorescent OLEDs are fabricated by using Ca/Al/Mg alloy as cathode, and the effects of different proportion of Ca/Al/Mg alloy on OLEDs are researched by changing the doping ratio of Mg. The device structures are as follows: ITO/MoO3(30 nm)/NPB(40 nm)/mCP:Firpic(8%)(40 nm)/CBP:R-4B(2%):Ir(ppy)3(14%)(5 nm)/TPBi(10 nm)/Alq3(40 nm)/Ca:Al:Mg(x%)(100 nm)(x=0, 5, 10, 15, 20, 25). The experiment results show that the cathode with Mg mass fraction of 15% has good electron injection characteristics which can effectively improve the light-emitting characteristics of the device. The maximum brightness is 1 504 cd/m2, the maximum current efficiency is 14.3 cd/A, and the color coordinates is close to (0.46, 0.42).关键词：Ca:Al:Mg alloy;cathode;electron injection115|79|0更新时间：2020-08-12
- 摘要：The sandwich films composed of aluminum doped zinc oxide (AZO)/silver (Ag)/aluminum doped zinc oxide (AZO) layers were prepared on glass substrates by RF magnetron sputtering using AZO powder target and solid Ag target at room temperature. Two groups of AZO/Ag/AZO films were deposited with Ag thickness of 12 nm and 15 nm. The optical and electrical properties of the sandwich films were investigated. The results show that the average transmittance of the films are about 80% within the visible wavelength, and the highest transmittance is 88% at 550 nm. The sheet resistances of the multilayer films are lower than 5 Ω/□. The thickness of Ag layer is the main factor to affect the optical and electrical properties of AZO/Ag/AZO films. The thickness of AZO layer has a certain effect on the optical properties of the sandwich films.关键词：TCO multilayer films;metal matrix TCO films;powder target;RF magnetron sputtering127|186|1更新时间：2020-08-12
- 摘要：The GaSb based Bragg reflection waveguide (BRW) lasers emitting at 2 μm with ultralow divergence were modeled. The dependence of far-field (FF) on the thickness of Bragg reflector and centre layer, the composition of Bragg reflector were simulated. The corresponding optical confinement factors were calculated. It was found that the increasing of the thickness of Bragg reflector and the thickness of high index material would improve the FF divergence. Thick center layer means the high OCF and FF angle, especially for the low thickness ratio between high index and low index material. Finally, the 2 μm GaSb based BRW lasers with an ultra-low vertical divergent FF angle less than 10° was optimized.关键词：mid-infrared semiconductor lasers;GaSb;Bragg reflection waveguide;low vertical divergence111|37|3更新时间：2020-08-12
- 摘要：The fence pattern that consists of volume discharges (VDs) and surface discharges (SDs) is observed by using the dielectric barrier discharge device with two water electrodes. The VDs uniformly distribute along the slit, and SDs are perpendicular to the slit and own two kinds of intensity. The short-exposed photograph is obtained by a high speed video camera. The plasma parameters of fence pattern are investigated by spectrograph. The emission spectra of the N2 second positive band(C3Πu→B3Πg)is collected, and the molecule vibrational temperature is calculated by the emission intensities. Furthermore, the width of Ar Ⅰ 696.5 nm is used to estimate the electron density. The results show that the volume discharges with strong surface discharges have higher molecule vibrational temperature and higher electron density than those with less surface discharge. Besides, along the surface discharge direction, surface discharge's molecule vibrational temperature and the electron density gradually decrease. The unequivalent distribution of the wall charges contributes to the formation of fence pattern.关键词：dielectric barrier discharge;fence pattern;molecular vibrational temperature;electron density85|142|1更新时间：2020-08-12
- 摘要：Surface morphology and molecular orientation of α-quaterthiophene (α-4T) thin films on silicon dioxide (SiO2) substrate were investigated by atomic force microscopy (AFM) and X-ray diffraction (XRD). At low substrate temperature, the large-size domain and high-order α-quaterthiophene (α-4T) thin film was obtained. The α-4T film exhibits the horizontal growth mode at low substrate temperature, but changes to the vertical growth mode above 35 ℃. By XRD analysis, it is found that the α-4T thin film adopts a monoclinic system, and the molecule c-axis is perpendicular to the substrate. The strong diffraction peaks and the high order diffraction peaks reveal that the films possess high crystallinity and order. In the electrical performance, the mobility increases with the increasing of the substrate temperature, and the mobility of α-4T device is 3.53×10-2 cm2·V-1·s-1 at 35 ℃. But the mobility of α-4T film decreases above 35 ℃. The results are in accordance with AFM analysis. The subthreshold gradient is reduced from 13.27 to 3.83 V·dec-1 by annealing at low temperature. The results imply that the interface defects are reduced and the electrical performances are greatly improved.117|26|1更新时间：2020-08-12
- 摘要：AlN films were prepared on patterned sapphire substrates (PSS) by direct-current reactive magnetron sputtering (RMS) and used as buffer layers. The crystal quality and optical properties of GaN films grown by metal-organic chemical vapor deposition (MOCVD) with AlN buffer layers were investigated. Compared with conventional low temperature GaN buffer layers, the RMS AlN buffer layers have smoother and smaller nucleation islands, which benefits the lateral growth and the coalesce of three-dimensional GaN islands. It is found that GaN-based LEDs with RMS AlN buffer layers have higher light output power, lower electric leakage and stronger electrostatic discharge(ESD) characteristic owning to the lower threading dislocation density (TDD).关键词：direct-current reactive magnetron sputtering;AlN buffer layer;GaN-based LEDs;metal-organic chemical vapor deposition128|171|0更新时间：2020-08-12
- 摘要：The interaction mechanism of trichazol (TRI) to lysozyme(LYSO) at different temperatures (298, 310, 318 K) was investigated using fluorescence spectroscopy under simulative physiological conditions. The results clearly demonstrated that TRI caused strong quenching of the fluorescence of LYSO by a static quenching mechanism. The binding constants were order of magnitude of 104 and the number of binding site in the interaction was closed to 1. The thermodynamic parameters of LYSO-TRI system were determined as follows: negative ΔH and positive ΔS, which indicated that electrostatic interaction played a major role in the binding reaction. The effect of cooperative binding of TRI was quantified by Hill's coefficient (nH) and the values of nH were slightly more than 1 in the systems, which indicated weakly positive cooperativeness in the interaction of TRI with LYSO. The binding distance (r) between TRI and LYSO was obtained based on the Förster nonradioactive resonance energy transfer and r was less than 7 nm. Furthermore, the effect of TRI on the conformation of LYSO was analyzed by using the synchronous fluorescence spectroscopy.关键词：fluorescence spectroscopy;synchronous fluorescence spectroscopy;lysozyme;trichazol;interaction mechanism136|112|3更新时间：2020-08-12
- 摘要：The surface enhanced Raman spectroscopy (SERS) method combined with the adaptive iterative re-weighted penalized least squares (air-PLS) method was used for the rapid detection of spiramycin residue in duck meat. Firstly, the OTR202 was used as SERS active substrate, and the peak 1 622 cm-1 was considered as the Raman characteristic peak for spiramycin residue in duck meat extract. Then the optimum experimental conditions were determined by using the single factor experiment. Under these conditions, the duck meat extract spiked samples, in which spiramycin concentration range was 4.0-50.0 mg/L, were analyzed, and the standard curve was established and a good linear relationship was obtained. The linear regression equation was y=26.681x+1233.5, and the coefficient of determination (R2) was 0.980 2. The detection limit was 4 mg/L, and the average recovery rate was 73.38%~105.25%. The research results show that it is feasible to realize the rapid detection of spiramycin residue in duck meat by using SERS.关键词：spiramycin;SERS;air-PLS;duck meat130|144|5更新时间：2020-08-12
- 摘要：Homemade BN/EP composites and Al2O3/EP composites were used as the adhesive layer between PCB and the heat sink of LED, respectively. The temperature distribution of LED working in the normal condition was measured by high-precision thermometers through a small hole. The effect of the adhesive layer composites on the junction temperature of LED was discussed, and was compared with the results from COMSOL simulations. A similar variation trend of junction temperature of LED was observed in both our experiment and COMSOL simulation. The junction temperature of LED raised with the increment of thickness of the adhesive layer. Besides, along with the increment of thermal conductivity of the adhesive layer composites, the junction temperature declined sharply at first, and then gradually decreased to a flat level. At last, we obtained two optimum values of the thickness and the ratio of adhesive layer composites with the best performance. When the mass fraction of BN is 60%, the thermal conductivity of BN/EP composites reaches at the highest level. In this condition, the junction temperature of LED is the lowest (75.2 ℃) and is 27.6 ℃ lower than that of using pure epoxy resin. In addition, the minimum junction temperature of the Al2O3/EP composites is 78.2 ℃ when the mass fraction of Al2O3 is 50%.关键词：adhesive layer;junction temperature;thermal conductivity;epoxy composites;temperature distribution125|95|1更新时间：2020-08-12
- 摘要：Fe3O4 magnetic nanoparticles were firstly synthesized by co-precipitation method, and Fe3O4@Ag magnetic material which has improved SERS effect was further prepared by reduction of AgNO3 using sodium citrate. Both density functional theory (DFT) and surface-enhanced Raman scattering (SERS) spectroscopy technique were used to investigate the adsorption behavior and enhancement effect of 2-thiophene carboxylic acid (2-TCA) on the Fe3O4@Ag surface. The results show that Raman spectra of the theoretical calculation and the determination are basically identical, and the more Ag atoms are introduced in theoretical calculation, the closer the measured value is to the theoretical value. The concentration and pH of the solution have great influence on the Raman enhancement effect, and the solution of 1×10-4 mol·L-1 at pH=3 can present excellent Raman signal response. The SERS effect increases initially and decreases afterwards with the increasing of concentration, which can be inferred that a lot of 2-TCA molecules are adsorbed and gathered on the Ag surface to form a local "congestion" and interfere the transmission of the excitation light, especially spectroscopic signal scattering. 2-TCA molecule morphology is changed with the increasing of pH, and the adsorption mode is influenced by the molecule morphology. The neutral C4H3SCOOH is vertically adsorbed on the Ag surface by the formation of S—Ag coordination bond. However, C4H3SCOO- anion is adsorbed on Ag surface with S—Ag coordinate bond and O—Ag covalent bond which is named as "double-bonged" side pattern. Although the adsorption of S—Ag coordinate bond is weaker than "double-bonged" side pattern, the SERS signal is stronger, because the neutral 2-TCA molecules are more beneficial to the generation of SERS signal comparing with 2-TCA- anion. The neutral 2-TCA molecules are gradually transformed into C4H3SCOO- anion with the increasing of pH, which leads to the decreasing of SERS effect gradually after pH>3.关键词：2-thiophene carboxylic acid;SERS;Fe3O4@Ag;DFT;chemical adsorption132|55|2更新时间：2020-08-12
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