最新刊期
卷 38 ， 期 9 ， 2017
- 摘要：A series of Er3+/Yb3+ co-doped phosphors with various Er3+ concentrations were synthesized via the conventional high temperature solid state method. The crystal structure of the obtained phosphor was analyzed by means of X-ray diffraction (XRD). The results show that the doping concentration do not evoke the change in crystal structure. The upconversion emission spectra for the phosphors doped with various Er3+ concentrations were measured upon 980 nm excitation under the same experimental conditions. The results show that the concentration quenching occurs at a higher concentration. The optical temperature sensing properties based on the fluorescence intensity ratio (FIR) method were discussed by analyzing intensities ratio of 2H11/2 and 4S3/2 emission with the temperature. It is observed that the sensitivity increases first and then decreases with the increase of temperature, and the sensitivity is the highest at 180℃. A physical model involving radiative/nonradiative transitions and thermal excitation of 2H11/2 and 4S3/2 emission is established, and the temperature quenching of the phenomenon is explained successfully.关键词：GdNbO4:Er3+/Yb3+;concentration quenching;temperature sensing;temperature quenching173|137|3更新时间：2020-08-12
- 摘要：Eu(DBM)3 Phen/PMMA fibers with uniform and random orientation were obtained by electrospinning method. The diameter of the fiber is about 700 nm assigned to submicron. Under ultraviolet irradiation, the submicron fluorescent fiber emits bright red fluorescence, and its excitation spectrum shows that the effective excitation wavelength is 200-400 nm. The absolute spectral power was carried out by using an integrating sphere with a CCD detector at 367 nm UVA-LED. When the power of LED pump is 535.76 μW, Eu(DBM)3 Phen/PMMA thin fiber layer with 80 μm is up to 89% in ultraviolet absorbing, and the total absolute spectral power, emission photon number and fluorescence quantum yield in the range of 350-850 nm are 36.56 μW, 11.46×1013 cps and 12.94%, respectively. The higher transition probability and emission cross-section of Eu3+ allow the fiber to absorb ultraviolet radiation effectively and convert it into visible light, therefore submicron Eu-(DBM)3 Phen/PMMA thin fiber layer has great application prospects in the improvement of solar cell conversion efficiency.关键词：Eu(DBM)3Phen/PMMA fibers;electrospinning;absolute spectral parameters;fluorescence quantum yield111|320|0更新时间：2020-08-12
- 摘要：Sr2MgSi2O7:Eu2+,Dy3+and Sr2MgSi2O7:Eu2+,Dy3+,Li+ phosphors were prepared by conventional solid state reaction method, and the influence of Li+ doping on the luminescent properties of Sr2MgSi2O7:Eu2+,Dy3+ phosphors was studied. The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence (PL), decay curves, and thermoluminescence (TL). The results indicate that the incorporation of Li+ ions has no influence on the position of the emission peak which is determined by 4f7→4f65d1 of Eu2+, while it has relationships with the intensity of the emission and the afterglow. The highest phosphorescent intensity was observed with 2.5% of Li+, and compared with the undoped sample, the phosphorescent intensity and the decay constant were increased by 1.5 and 1.6 times, respectively. By the characteristic of TL measurement, the number and the depth of trap level were analyzed. The doping of Li+ can increase the number of oxygen vacancies and increase the trap depth, so as to improve the afterglow properties of phosphor.关键词：Sr2MgSi2O7:Eu2+;Dy3+;lithium ion;luminescent properties154|138|4更新时间：2020-08-12
- 摘要：LiLuF4:Yb,Tm@LiGdF4 core-shell nanoparticles were synthesized by high temperature thermal decomposition method. Under the excitation of980 nm near infrared (NIR) laser, the luminescence intensity of the core-shell nanoparticles can be enhanced by about 15 times in contrast to the pure LiLuF4 core. It is due to the passivating role of the inert-shell for protecting Tm3+ ions in the core from nonradiative decay caused by surface defects. The intensity of the UC emission of the nanocrystals increases (at most 12.4 times) as the mole fraction of Yb3+ ions increases from 20% to 100%, owing to the improvement of near-infrared absorption and energy-transfer from Yb3+ to Tm3+. LiYbF4:2%Tm@LiGdF4 core-shell nanoparticles show a high absolute UC quantum yield of 4.0%.关键词：upconversion luminescence;core-shell nanoparticles;LiLuF4;doping concentration147|42|3更新时间：2020-08-12
- 摘要：CdS, Se, Zn powder and glass matrix were used as raw material to prepare the CdSxSe1-x quantum dots silicate glass by using co-melting method. The effect of ZnO content on the microscopic structure and luminescent properties of CdSxSe1-x quantum dots silicate glass were studied. Experimental results indicate that ZnO can significantly influence the luminescence properties of CdSxSe1-x quantum dots glass. The results of ultraviolet-visible absorption spectrum and fluorescence spectrum analysis show that the CdSxSe1-x quantum dots are in a strong confined area, which lead to a strong belt edge exciton emission phenomenon, proving that the quantum size effect of quantum dots is obvious under the excitation of 470 nm blue light. When the mole fraction of ZnO is 13%, the PL spectrum peak is the strongest, and the half width of peak is the narrowest.关键词：CdSxSe1-x quantum dots;ZnO;glass;luminous performance119|161|0更新时间：2020-08-12
- 摘要：(Zn1-x,Mgx)2GeO4:Mn2+ (0 ≤ x ≤ 0.25) green phosphors were synthesized by the conventional solid-state reaction, and the effect of Mg incorporation on photoluminescence (PL) and long-lasting phosphorescence (LLP) characteristics of Zn2GeO4:Mn2+ was systematically studied. The emission spectrum shows a broad emission band centered at 533 nm, which can be assigned to the 4T1(4G)→6A1(6S) transitions of Mn2+ ion. The emission intensity can be increased by the resonant transfer from a subbandgap state in the host to Mn2+, and the PLE spectra of (Zn1-x,Mgx)2GeO4:Mn2+ exhibit a blue shift with the increasing of Mg concentration. Thermoluminescence (TL) spectra indicate that the introduction of Mg into the host deepened the Vo traps, resulting in the enhanced phosphorescence of Mn2+. The possible mechanism of the PL and LLP was discussed based on the PL and TL results.关键词：long-lasting phosphorescence;(Zn1-x;Mgx)2GeO4:Mn2+;thermoluminescence136|90|3更新时间：2020-08-12
- 摘要：The strong luminescent amorphous silicon oxycarbide (a-SiCxOy) films with different O content were prepared by very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) at 250℃ by using the gas mixture of SiH4, CH4 and O2 as the precursor. The effect of O content on the luminescent properties and structure of SiCxOy thin films was investigated. It is found that the increase of O content results in remarkable photoluminescence (PL) with orange-red to blue shifting emission, which can be clearly observed with the naked eyes in a bright room. The PL of the a-SiCxOy film is suggested from the nanoseconds recombination lifetime. The microstructure and the chemical compositions of the films were further investigated by Raman spectra, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared absorption (FTIR) spectroscopy, respectively. Combining with the PL results and the analysis of the chemical bonds and microstructure present in the films, the main phase structure of the films and the change of the luminescent center with the O2 flow rate are the main reasons for the tunable light emission.关键词：photoluminescence;silicon oxycarbide;plasma enhance chemical vapor deposition;photoluminescence mechanism152|134|1更新时间：2020-08-12
- 摘要：Nanocrystalline-Ge (nc-Ge)/amorphous-SiNx (a-SiNx) multilayers (MLs) were fabricated by oxidizing hydrogenated amorphous-Ge(a-Ge:H)/a-SiNx multilayers. Its strong photoluminescence (PL), peak at 500 nm, was observed at room temperature. Then, the mechanism of PL was studied, which indicated that the light emission was irrelevant to quantum confinement effect. The recombination of defects related to Si or N was also excluded. It is believed the PL of nc-Ge/SiNx MLs is originated from the radiative recombination of tail states of oxidized a-SiNx matrix, and the most effective excitation energy is close to the optical band gap of matrix.关键词：nanocrystalline-Ge;photoluminescence;radiative recombination120|214|0更新时间：2020-08-12
- 摘要：A new π-conjugated organic compound containing imidazole and pyridine, namely, 6-phenyl-4-4-[4-(1H-(pyrazole) vinyl] phenyl)-2,2'-bipyridine was successfully synthesized through Wittig reaction. It was characterized by elemental analysis, IR, 1H NMR and Ms. The absorption spectra of the compound at the level of B3LYP/-31G(d)//B3LYP/6-31G were obtained. The optical properties of the compound were investigated by ultraviolet-visible (UV) absorption spectra and single photon fluorescence spectra in different solvents. The results indicate that the target compound exhibits strong blue light-emitting, which makes it well suitable for fluorescence material.关键词：organic compound;characterization;photophysical property;pyridine;blue emitting materials144|352|1更新时间：2020-08-12
- 摘要：In order to achieve the goal of the interchange between traditional white light emitting diodes (WLEDs) and plant growth lights, the fluorescent polycarbonate (PC) lampshades with different mass fraction of CaAlSiN3:Eu2+ (CASN:Eu2+) phosphor were prepared through granulation by high-temperature melting process. The lampshade samples were characterized by structural and optical analysis, showing a good stability during the preparation process. Meanwhile, the fluorescent PC lampshades were equipped with WLED T8 tubes for plant growth lights. The EL spectra, optical parameters and application of such plant growth lights were given. With the increase of CASN:Eu2+ phosphor mass fraction in PC lampshade encapsulated WLEDs, the CIE color coordinates change from (0.327 2, 0.346 7) to (0.389 5, 0.382 4), the correlated color temperature (CCT) declines from 5 757 to 3 807 K, the color rendering index raises from 70.3 to 77.6, but the luminous efficiency decreases slightly. Furthermore, the electroluminescence (EL) spectra of CaAlSiN3:Eu2+ phosphor doped PC lampshade encapsulated WLEDs match well with the absorption ones of lettuce, and the growth of lettuce is better to be promoted under irradiation by corresponding WLEDs (phosphor mass fraction:4‰), indicating that the design of combination of fluorescent PC lampshades and LED T8 tubes has a good application prospect for plant growth.关键词：CaAlSiN3:Eu2+;polycarbonate;lampshade;plant growth light;WLED134|152|1更新时间：2020-08-12
- 摘要：The correlation function of the size-bond parameter-Raman shift was formulated based on the bond order-length-strength (BOLS) correlation and core-shell model. The quantitative information of the bond length, bond energy and the effective atomic coordination number (CN) of the Ⅳ materials was obtained. It is clarified that the size-induced phonon softening arises intrinsically from the undercoordinated atoms. Developed approach empowers the Raman technique in deriving quantitative.关键词：Raman shift;bond parameters;nano size127|286|0更新时间：2020-08-12
- 摘要：InGaN based blue light emitting diodes(LED) with different thickness of undoped GaN (u-GaN) layer were grown on c-plane pattern sapphire substrates by metal-organic chemical vapor deposition (MOCVD). The structure and photoelectric properties were characterized by in-situ wafer bowing measurements, high-resolution X-ray diffraction(HRXRD) and photoluminescence (PL). Due to the different thermal expansion coefficients between the sapphire and the epitaxial film, the curvature of wafer varies constantly in the progress of temperature changing. It is found that the wafer presents concave bowing at the end of n-GaN growth directly affects the wafer status of bowing during the MQWs growth. The wafer with 3.63 μm u-GaN layer is under the biggest bowing status indicating that the stress value of n-GaN is the maximum. In the subsequent lower temperature MQWs deposition stage, the concave deformation constantly decreases, and even transforms into the convex deformation. The in-situ wafer bowing measurements results are in accordance with the PL-mapping tests. The wafer with better uniformity and consistency can be obtained by adjusting the thickness of u-GaN layer which can change the status of stress in the epitaxial structures, and finally be beneficial to reduce the processing time and the cost of the LED chips.关键词：metal-organic chemical vapor deposition;gallium nitride;stress;LED163|276|2更新时间：2020-08-12
- 摘要：The bias stability of the flexible thin-film transistors under various bending radii was investigated. The thin-film transistors with p-type low temperature poly-silicon channel layers were fabricated on polyimide substrate. The changing region of the bending radius was from 15 mm to 3 mm. For the stretch bending, the threshold voltage kept the same with the flat(Vth=-1.34 V), the mobility reduced from 45.65 cm2/(V·s) to 45.17 cm2/(V·s), and Ion/Ioff increased. For the compress bending, the transfer curve well kept the same with the flat. When the minimum bending radius was 3 mm, the device was tested under the positive and negative bias stress, and showed good stability. The experiment results indicate that the flexible LTPS-TFTs have fine performance and stability.关键词：flexible;thin-film transistors;LTPS-TFT;bending;stability129|216|2更新时间：2020-08-12
- 摘要：An electron-rich poly(n-vinylcarbazole) (PVK) was applied to dope the[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) to explore the influence of PVK on the electron transfer layer of planar heterojunction perovskite solar cells. Under the optimized PVK doping mass fraction of 4%, the power conversion efficiency (PCE) of the CH3NH3PbI3 perovskite solar cells is enhanced from (5.11±0.14)% to (9.08±0.46)%. According to the surface morphology study of the electron transport layer, PVK doping improves the coverage and quality of PCBM layer onto the rough perovskite layer, and this is beneficial for the interfacial contact of the CH3NH3PbI3, PCBM films and the top Al electrode, which results in the decrease of leakage current. Moreover steady-state PL analysis shows that the electron-rich PVK have a better passivation effect on the trap states at the perovskite surface or crystal boundaries as a material of interfacial modification of cathodes, thus can apparently decrease the charge recombination of the perovskite solar cells.关键词：perovskite solar cells;doping;nterface engineering;poly(n-vinylcarbazole;trap states155|201|1更新时间：2020-08-12
- 摘要：In order to study the performance of flexible solar cells,low-weight flexible GaInP/Ga(In)As/Ge triple-junction solar cell was fabricated by thinning process. The weight of the 40 mm×60 mm solar cell chip is 0.7 g, which is only 30% of the conventional solar cell with the thickness of 175 μm. The conversion efficiency of this kind of solar cell is 30.64%, closing to that of the normal thickness chips. The results show the feasibility of this thinning process. For both samples with different chips thickness, under different temperature, the dark I-V curves were measured and the temperature coefficients were fitted. It can be concluded that the temperature coefficient is linearly correlated to the PN junction rather than the substrate type.关键词：space solar cell;flexible solar cell;temperature coefficient141|226|2更新时间：2020-08-12
- 摘要：Photoacoustic tomography (PAT), an emerging medical imaging modality, combines the high resolution of ultrasonic imaging and high contrast of optical imaging. Current research on PAT includes two inverse problems, i.e., constructing the distribution of initial acoustic pressures according to the photo-acoustic signals generated by the tissues and estimating the optical absorption and scattering coefficients of the tissues within the imaging region based on the results of the first inversion. The latter, known as quantitative photoacoustic tomography (qPAT), is in general a nonlinear ill-posed problem. This paper summarizes current algorithms for solving the qPAT inversion. Related advantages and limits as well as perspective studies are discussed.关键词：quantitative photoacoustic tomography (qPAT);image reconstruction;inverse problem;optical absorption coefficient;diffusion coefficient;Gruneisen coefficient223|262|3更新时间：2020-08-12
- 摘要：Au@Ag core-shell bimetallic nanoparticles were prepared by chemical reduction method and successfully applied to surface-enhanced Raman scattering (SERS) analysis. The thickness of the coated Ag shell is regulated by changing the Ag/Au molar ratios in the preparation solution. The morphology of the Au@Ag nanoparticles were characterized by TEM and further confirmed by UV-Vis. TEM spectra show that Au@Ag nanoparticles have obvious core-shell structure, and the Ag shell layer becomes thicker with the increasing of Ag/Au molar ratio. UV-Vis spectra show that Au@Ag nanoparticles exhibit two plasmon resonance absorption peaks assigned to Au and Ag plasmonic absorption. When Ag/Au molar ratio increases, the Au core resonance is blue-shifted and the Ag shell resonance is red-shifted. The enhanced effects of Au@Ag nanoparticles with different Ag/Au molar ratios in SERS were investigated by using amitraz as a probe. It is found that the SERS intensity of amitraz is enhanced firstly and then becomes weaker with the increasing of Ag/Au molar ratios, The optimum SERS signal appeares when the Ag/Au molar ratio is 6:5 and the thickness of Ag shell is 6 nm. Moreover, the SERS effects of Au@Ag, Ag and Au nanparticles were further compared by using p-mercaptoaniline (4-ATP), crystal violet (CV) and amitraz as analytes. The results show that the SERS effect of Au@Ag nanoparticles is obviously stronger than that of pure Au or Ag nanoparticles.关键词：Au;Ag;Au@Ag;nanparticles;surface-enhanced Raman scattering194|43|2更新时间：2020-08-12
- 摘要：There are many brands of sesame oil, corn oil and peanut oil in the vegetable oil market. There is a big difference among the price of different brands, and the phenomenon of counterfeiting is existing. Fluorescence spectroscopy can be used to identify the real label of the oil species. Principal component analysis and parallel factor method can classify manually three species of oils, but there is a problem that the distance between classes is too small compared to the in-class distance, and it is easy to cause misclassification when the traditional clustering analysis method is used. In order to improve the distance between classes to achieve the correct clustering, the mean, standard deviation, gravity coordinates of spectral center, second-order mixed center distance, correlation coefficient, equivalent elliptical double diagonal tangent, the skewness coefficient and the kurtosis coefficient of the emission spectrum at gravity excitation wavelength are selected as statistical parameters after the comparative analysis. Compared to the traditional clustering methods, the accuracy rate of sesame oil classification increased from 92.3% to 100%, and the accuracy of corn oil classification increased from 75% to 100% and the accuracy of the peanut oil classification increased from 57.1% to 100%. Finally, partial least squares discriminant analysis is used to verify the validity of the selected method. The method used here can be used for automatic classification of vegetable oil in detection equipment, which will help regulate the market and guide people's daily consumption.关键词：spectroscopy;vegetable oil classification;statistical parameters;distance between classes114|200|3更新时间：2020-08-12
- 摘要：A nonlinear mathematical model of the relationship between the luminous flux and the color temperature of the hybrid light source is established by analyzing the hybrid dimming method of pulse width modulation (PWM) dual channel output white LED. The system uses ZigBee wireless communication module CC2530 as a dual PWM output control to SN3350 as the core of the LED constant current drive power. It achieves a duty cycle adjustable warm white and cool white two white LED color temperature and luminous flux mixed dimming control. Experiments were carried out using a high-precision, fast spectroradiometer (HAAS-2000) test system. Experimental results show that the dual PWM can achieve better control of LED color temperature and luminous flux, and the correlated color temperature of the mixed light source can be continuously adjusted in the range of 3 250 K to 15 000 K. The relative errors of theoretical calculation and system control are less than 1.70% and 8.50%, respectively, corresponding to the luminous flux and color temperature.关键词：dynamic lighting control;LED mixed dimming;nonlinear mixed dimming;pulse width modulation(PWM)133|112|2更新时间：2020-08-12
- 摘要：The binding of ceftazidime (CFD) with trypsin (TRP) was investigated by spectroscopic and molecular docking methods under different temperature conditions (298, 303 and 310 K). The results demonstrate that the interaction between CFD and TRP is taking place via static quenching with 1:1 binding ratio. The fluorescence data were treated by using the double logarithmic equation, and the binding constants Ka of the interaction of CFD-TRP systems and the number of binding sites n were obtained. The thermodynamic parameters of CFD-TRP systems under different temperatures were obtained by the thermodynamic equation. The experimental data show that the interactions between them are mainly hydrophobic interaction and hydrogen bonding interaction, which is consistent with the molecular docking results.关键词：spectrometry;molecular docking;ceftazidime;trypsin;interaction mechanism91|168|3更新时间：2020-08-12
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