最新刊期
卷 39 ， 期 10 ， 2018
- 摘要：Dy3+ doped C12A7 (C12A7:x% Dy3+) X-ray phosphors with different doping concentrations were prepared by a self-propagating combustion method in combination with a heat-treatment at high temperature. For these phosphors upon 350 nm excitation, two obvious emission peaks at 486 and 575 nm, originate from the 4F9/2→6H15/2 and 4F9/2→6H13/2 transitions of Dy3+. As the mole fraction of Dy3+ is 0.3%, the strongest intensities of the two emission peaks can be reached. For the C12A7:0.3% Dy3+ phosphor heattreated at 1 300℃ in N2 ambient for 2 h, the photostimulable luminescence intensity is enhanced and more deep traps are generated due to the decreasing encaged OH- anions compared to the unheattreated sample. It can be found that, under a moderate amount of X-ray absorbed dose(0.54 Gy), high quality X-ray imaging can be realized by using an imaging object, which is two thin wires capped with insulating layer, and using an imaging plate, which is a round tablet fabricated by pressed the heattreated C12A7:0.3%Dy3+ powders. Our results suggest that Dy3+ doped C12A7 X-ray phosphors have a potential application for the techniques related to digital static X-ray imaging.关键词：photoluminescence;phosphor;rare earth;photostimulable luminescence145|132|1更新时间：2020-08-12
- 摘要：As a new kind of fluorescent probe, quantum dots(QD) have got more and more attention especially the preparation. However, QDs synthesized in aqueous phase suffer from the low efficiency and quantum yield of oil-soluble QDs dropped significantly after the ligand exchange. In this work, we report a type of green CdSe@ZnS-based(G-NPs, 534 nm) and red CdSe@ZnS-based (R-NPs, 610 nm) nanoparticles prepared via a facile reprecipitation-encapsulation method. They possess a narrow half peak width(G-NPs~29 nm, R-NPs~31 nm), smaller particle size(45 nm). Also, we discuss critical energy transfer mechanism through the emission spectrum and the fluorescence decay. This method preserves the properties of QDs, and we used the NPs to label cancer cells(HepG2) due to their excellent optical properties. Fluorescence images of the cells clearly indicate that a good fraction of the NPs has been swallowed.关键词：CdSe@ZnS quantum dots;biological compatibility;fluorescence labeling;fluorescent lifetime;energy transfer147|195|2更新时间：2020-08-12
- 摘要：The composite of polyaniline and reduced graphene was prepared through the chemical oxidation synthesis. The structure and electromagnetic parameters of the composites were investigated by XRD and HP8722ES network analyzer. The results show that the dielectric loss of the composite material is significantly higher than polyaniline. When the content of graphene is increased in the composite, the microwave absorption property of the material becomes better. The composite material has a much higher reflection loss and wider bandwidth than pure polyaniline in the frequency range(9.5-13.4 GHz). The combination of polyaniline and reduced grapheme improves the carrier mobility of the material and enhances microwave absorption property of the material consequently.关键词：microwave absorption;grapheme;polyaniline133|170|2更新时间：2020-08-12
- 摘要：A new type of Er3+/RE3+ (RE3+=Ce3+, Tb3+)-doped GeO2-TeO2-Na2O glasses were prepared by melting quenching method. The differential scanning analysis curves, visible/near infrared transmittance, Raman spectra, absorption spectra and 1.53 μm luminescence spectra were tested. It is found that the thermal stability is enhanced and the absorption cutoff edge of the samples blue-shifted with the increase of substituted GeO2 content for TeO2. Raman analysis shows that the GeO2-TeO2-Na2O glass has a wide range of infrared transmittance. Meanwhile, the influence of rare earth ions (RE3+=Ce3+, Tb3+) on the spectral properties and energy transfer of Er3+-doped 45GeO2-45TeO2-10Na2O glass under 980 nm excitation has been studied. 1.53 μm emission intensity shows a firstly increasing and then decreasing trend, and the optimal CeO2 mole fraction is 0.1%. While co-doping Tb3+ reduces the 1.53 μm emission intensity of Er3+. It can be seen that the Er3+/Ce3+-doped 45GeO2-45TeO2-10Na2O glass might be a promising material in the field of C band fiber amplifier.关键词：GeO2-TeO2-Na2O glass;structure;Er3+/Ce3+ (Tb3+);spectroscopic properties160|131|2更新时间：2020-08-12
- 摘要：In order to study the characteristics of the non-bridging oxygen hole centers(NBOHC)defects in silica glass, Yb3+-doped silica glass was prepared using high frequency plasma technology. First of all, the preparation process of glass sample was introduced. The absorption characteristics, emission characteristics and Fourier transform infrared absorption spectra of the prepared Yb3+-doped silica glass were analyzed. The analysis results show that the prepared glass sample has the typical absorption pattern of Yb3+ ion. The absorption peak at 260 nm and 200 nm-excited emission peak at 630 nm indicate that the NBOHC defects exist in the glass sample. What's more, both the emission peak generated by different exciting wavelengths and the infrared absorption spectra indicate that there are two kinds of NBOHC, in other words, ≡Si-O↑ and ≡Si-O↑…H-O-Si≡. The energy transfer process exists between cooperative emission of Yb3+ ions pairs and NBOHC defects.关键词：rare earth doped materials;Yb3+-doped silica glass;high frequency plasma;NBOHC defects158|259|1更新时间：2020-08-12
- 摘要：A series of Eu3+ activated Ba3WO6 red phosphors were synthesized by high temperature solid state method. The structure and luminescence properties were characterized by XRD and FL, respectively. The results show that all samples have the cubic double-perovskite structure. The excitation spectrum of Eu3+ is consisted of a broad band including the Eu3+-O2- and W6+-O2- charge transfer bands and several peaks due to 4f-4f transitions of Eu3+. The emission spectrum is majorly consisted of transitions 5D0→7F1 and 5D0→7F2. By adjusting the mole ratio of BaCO3 and WO3, the peaks of XRD are red shifted and accorded with the standard, the luminescence intensity is promoted. The critical mole fraction of Eu3+ is 0.05 and the critical distance(Rc) is 1.263 4 nm. Under 314 or 394 nm excitation, the samples can emit red light(λmax=596 nm) with CIE color coordinates around (0.618, 0.342), suggesting the synthesized phosphors as promising candidate in the LED lighting and display fields.关键词：Ba3WO6:Eu3+;red phosphor;Ba2 lattice site140|95|2更新时间：2020-08-12
- 摘要：Mn2+ doped-NaYF4:Yb3+/Tm3+ upconversion fluorescence nanoparticles(NPs) were synthesized by one-step hydrothermal method under 200℃ for 8 h, and then the hydrophobic nanoparticles were transferred into water through coating amphiphilic polymer C18PMH-mPEG. Upconversion fluorescence emission spectrum of Mn2+ doped-NaYF4:Yb3+/Tm3+ NPs was measured under excitation by a near-infrared(NIR) light at 980 nm. The results of cytotoxicity test show that the water-soluble Mn2+ doped-NaYF4:Yb3+/Tm3+ NPs have good biocompatibility. Moreover, the prepared Mn2+ doped-NaYF4:Yb3+/Tm3+ NPs are used for in mice NIR imaging, which shows that it will have a certain application prospect in bioimaging.关键词：hydrothermal;Yb3+/Tm3+;upconversion;nanoparticles;bioimaging166|113|1更新时间：2020-08-12
- 摘要：N1-alkyl-1,2,3-triazoles and N2-alkyl-1,2,3-triazoles were prepared, and their photophysical properties were investigated. Both type of 1,2,3-triazoles have strong photo absorptions at near 250 nm, however only N2-alkyl-1,2,3-triazoles give fluorescence emissions. From the screen of the photophysical properties of different substituted N2-alkyl-1,2,3-triazoles at N2-or C4-sites, it is found that N2-alkyl-1,2,3-triazoles bearing rich electron benzyl group at N2-site or poor electron phenyl group in C4-site have the strong fluorescent intensity, and the quantum yields are up to 79% with 300-440 nm of fluorescent emissions and 49-70 nm of Stokes shifts. The photophysical properties of N2-alkyl-1,2,3-triazoles show their potent application in the development of fluorescent materieals.关键词：N2-alkyl-1;2;3-triazole;fluorescent intensity;quantum yield135|124|0更新时间：2020-08-12
- 摘要：Sr3LaAxV3-xO12:Eu3+ (A=Mo, W) phosphors were synthesized by a high temperature solid state method. X-ray diffraction(XRD), scanning electron microscopy(SEM), photoluminescence spectra, and lifetime were utilized to characterize the samples. Partial substitution of VO43- by MoO42- and WO42- in Sr3LaAxV3-xO12:Eu3+ (A=Mo, W) can weaken the emission of VO43-, and cause a red shift of emission position, but has little influence on the emission of Eu3+ ion. After charge compensation by adding F- in Sr3LaMoxFxV3-xO12:Eu3+, the excitation energy of VO43- can be transferred to Eu3+ ion and then enhance the emission of Eu3+ ion. A white phosphor of Sr3LaAxV3-xO12:Eu3+ (A=Mo, W) can be obtained by adjusting the emissions of the VO43- and Eu3+ ions. The enhancement mechanism of the red emission of Eu3+ by anion substitution was briefly discussed.关键词：vanadate phosphor;anion substitution;luminescence of Eu3+;white phosphor129|47|0更新时间：2020-08-12
- 摘要：One-dimensional nanomaterial SmPO4·0.5H2O was synthesized using hydrothermal method from samarium oxide and H3PO4 in the absence of a template agent. Effects of pH, reaction time and temperature, and the possible formation mechanism were invetisgated. The phase structure, microstructure and composition of the products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy(TEM, HRTEM and SAED), infrared spectroscopy (IR) and energy dispersive spectroscopy(EDS). The optical properties of the products were studied by absorption spectra. It is shown that all the products prepared by the experiment adopthexagonal crystal structure, and the morphology is a one-dimensional nanowire. Theratio of length to diameter in nanowires was significantly influenced by pH value, temperature and time of the reaction system, which have no effect on the phase structure. The optimum conditions of hydrothermal preparation are pH=5, 130℃ and 8 h, respectively. The crystallization, dispersion and uniformity of the products are best on this condition. The studies of optical properties show that there products have an absorption wide peak in the ultraviolet region of 300-350 nm. The wide peak belongs to the charge transfer band (CTB) of O2-→P5+,Sm3+. A set of absorption peaksare observed in the visible region of 350-450 nm, which belong to the f-f transition absorption between the 4f inner-layer electrons of Sm3+.According to these absorption peaks, the band gap energy(Eg) is 4.67-5.50 eV. The pH value and temperature have effects on optical properties of the products.关键词：SmPO4·0.5H2O;nanowires;hydrothermal method;optical properties197|66|0更新时间：2020-08-12
- 摘要：The light signal in the generation and propagation of plasma jet produced by the single needle electrode was studied. It is found that the length of plasma jet does not increase with the applied voltage, but relates to the distribution of energy between pulse discharges(PD) in the positive half-cycle. The first PD is produced at the needle electrode, the second PD is produced in the middle of plasma channel where the electron excitation temperature reaches its highest value. We conclude that the additional electric field generated by space charge has great influence on the generation and development of plasma jet.关键词：plasma jet;single needle electrode;electronic excitation temperature;space charge135|101|0更新时间：2020-08-12
- 摘要：To improve the properties of polymer solar cells, the effect of magnetic nanoparticles on the P3HT:PCBM films as the active layer and the properties of polymer solar cells under the external magnetic field were investigated. The Fe3O4 magnetic nanoparticles were prepared by thermal decomposition. The Fe3O4 nanoparticles of different mass fraction were added to P3HT:PCBM solution.The as-casting films by spin coating method were put into the external magnetic field and the self-assembled Fe3O4+P3HT:PCBM films were formed. Fe3O4 nanoparticles were characterized by TEM and XRD, and the surface morphology of films was investigated by polarizing microscope(POM) and atomic force microscope(AFM). The results show that Fe3O4 nanoparticles are about 10 nm in diameter, and have a certain regulating effect on building film of P3HT:PCBM. When Fe3O4 nanoparticles are added with a mass fraction 1%, the open circuit voltage(Voc) of the solar cells increases by 3.77%, the short-circuit current(Ist) increases by 24.93%, and the photoelectric conversion efficiency(PCE) increases by 7.82%.关键词：Fe3O4 nanoparticles;polymer solar cells;surface morphology;P3HT:PCBM133|73|1更新时间：2020-08-12
- 摘要：Capacitance-voltage(C-V) measurement is a useful method for studying of pn junction. In this paper, the C-V measurement was applied to analyze the influence of temperature on the type of pn junction of GaN-base LED in a temperature range from 25℃ to -195℃ according to C-2-V curve, C-3-V curve and power law index k. The experimental results showed that the change of temperature will have an effect on the structure of junction. When the temperatures are 25℃ and -50℃, respectively, there was a significant linear relationship for C-2-V, and the index k was 0.5, which indicating an abrupt junction in a temperature range from 25℃ to -50℃. When the temperature was cooled down to T=-100℃, the structural type of pn junction began to change and the index k was 0.45. When the temperature continued to decrease to T=-150℃ and -195℃, the index k became 0.30 and 0.28, corresponding to a non-abrupt and non-linear junction. The possible explanations of such phenomenon were low-temperature carrier freeze effect, and the localized space charge region produced by crystal defects and interface states. The enhancement of localized space charge region finally affected the structure of pn junction in low temperature environment.关键词：GaN-based blue light emitting diodes;pn junction;C-V measurement;power-law137|141|0更新时间：2020-08-12
- 摘要：To investigate the effect of growth temperature on epitaxial ZnO nanostructures and optimize the growth temperature conditions for controlled growth of ZnO nanostructures, ZnO epitaxial samples with different growth temperatures were designed and obtained by metal organic chemical vapor deposition (MOCVD). All the samples were characterized by surface morphology, optical, electrical and crystal quality characterizations. The experimental results show that the ZnO nanorods grown at 600℃ have the smallest transverse dimension of about 65 nm, which the optical properties are the best. Its FWHM of the diffraction peak is the smallest of 0.165° with the largest grain size of 47.6 nm. Among these samples, the sample grown at 640℃ has the relatively optimal electrical property, with the Hall mobility of 23.5 cm2/(V·s). Through the analysis of the results, it is found that the growth temperature can affect the growth mode of epitaxial ZnO and thus the morphology, optical, electrical and crystal properties of ZnO.关键词：ZnO;MOCVD;substrate temperature;nanostructures95|127|0更新时间：2020-08-12
- 摘要：ZnO films were deposited on zein by radio frequency(RF) magnetron sputtering technique. We investigated the influences of deposition parameters, such as target-to-substrate distance, Ar/O2 ratio and sputtering power on the properties of ZnO films. The results show that c-axis preferred orientation of ZnO films is obtained at small target-to-substrate distance. We also find that ZnO films deposited on zein is in a state of tensile stress, whereas the film deposited at Ar/(Ar+O2) ratio of 0.7 has the lowest tensile stress. The near-band-edge peaks of ZnO films in photoluminescence spectra show blueshifts. We speculate that the blueshifts are caused by the oxygen vacancy and the electrostatic potentials that exist at the grain boundaries. As the sputtering power increases, the deposition rate and the grain size of ZnO films increase, the near-band-edge peak of ZnO film shifts toward the theoretical value gradually.关键词：ZnO films;zein films;magnetron sputtering;X ray diffraction;photoluminescence spectrum128|131|0更新时间：2020-08-12
- 摘要：A unique ETL, composed of conventional organic materials used in OLED and ZnO nanoparticles(ZnO NPs) was adoped to improve the green-QLED device performance. The thickness of the organic ETL was adjusted to control the electron injection, therefore balance the electron/hole ratio. The device architecture of the green QLED fabricated in this work was ITO/PEDOT:PSS/TFB/QDs/ZnO NPs/TPBI:Liq/Al, in which the organic ETL was co-evaporated from TPBI and Liq. Compared with the device only having ZnO as the ETL, an additional organic ETL boosted the maximum current efficiency from 11.53 cd/A to 22.77 cd/A, without any significant impact on the turn-on voltage and the electroluminescence spectrum. We propose that the additional organic ETL has helped to suppress excess amounts of electrons being injected into the QD emissive layer, reducing the inefficient recombination (like Auger recombination) current without sacrificing much of the emission output, and eventually improved the device efficiency.关键词：quantum dots;electroluminescence;electron transport layer;organic/inorganic177|299|0更新时间：2020-08-12
- 摘要：Silicon doping in barrier has an important effect on the electric field in InGaN quantum wells and its photoelectric properties of LED devices. Electric field in multiple quantum wells with the different silicon doping concentration in barrier was calculated by 6×6 K·P method. The results show that the electric field intensity in the well/barrier interface becomes larger when the silicon doping concentration in the barrier is above 1e18 cm-3, which is mainly attributed to the accumulation of the interface charge in the quantum well. It is found that the total non radiation recombination increases and Auger recombination increases as barrier doping concentration increased, while Shockley-Read-Hall recombination decreases because of the increasing dot traps result in the formation of defect energy levels. The current-voltage curves show that the barrier doping can effectively improve the work voltage of GaN based LED because doped barrier will contribute to improve the transport characteristics of carriers. When silicon doping concentration is 1e18 cm-3, the high internal quantum efficiency is obtained, which is mainly attributed to the reduction of interface charge loss in the quantum well due to the appropriate potential barrier doping.关键词：potential barrier;quantum well;polarization electric field;photoelectric properties156|287|0更新时间：2020-08-12
- 摘要：A comparison between the surface properties of inkjet printed and spin coated PEDOT:PSS films was made in consequence of the intriguing distinction after printing emitting layer inks on them. The sizable and hill-like polymer grains were only found on the surface of the inkjet printed PEDOT:PSS film. Further investigation demonstrated the difference in morphology stems from the diverse of wetting properties. The differing effects on film properties between inkjet printing and spin coating were revealed, according to which a finer structure was constructed on inkjet printed PEDOT:PSS film.关键词：inkjet printing;organic light emitting diodes;multilayer printing;surface morphology control176|179|0更新时间：2020-08-12
- 摘要：This paper presents a calibration model, namely, improved auto encoder, which can be used to predict the grade of soil organic matter content in large scale based on near infrared spectroscopy. First, the framework of improved auto encoder model was proposed, which combined traditional auto encoder and classifier, and loss function of the model is defined. Then, the proposed improved auto encoder was applied to predict the grade of soil organic matter content based on near infrared spectroscopy. The encoder, decoder and classifier were implemented with two-layer feed-forward neural networks. Finally, a large scale soil spectral dataset was used to train the model for predicting the grade of soil organic matter content. The performance was compared with the results of principal component regression and support vector machine. The results show that the classification accuracy of soil organic matter content grades based on the proposed improved auto encoder model is 63.05%, which is better than other methods. This model can be used to predict the grades of soil organic matter content in a large scale.关键词：NIR spectroscopy;auto encoder;soil organic matter;modeling145|192|4更新时间：2020-08-12
- 摘要：Aiming at the problem of poor uniformity of the existing plant lights, a high uniformity light was designed by installing light pipes and fiber lenses on R(red), G(green), and B(blue) three-color LED chips. By adjusting the size of the light pipe and the optical fiber, the uniformity of spectra, color mixing and photosynthetic photon flux density(PPFD) reached 90%. The thermal properties character of the light source were measured further. It was found that the increase of the fiber lens favored and reduced the heat at the front of the light source, and the uniformity of the lamp was evaluated based on the light quantum illumination parameters. Besides, effective light energy utilization was proposed to characterize light source performance more scientifically. The results show that the color uniformity and PPFD uniformity can reach 90%, and the effective light energy utilization can reach 43%. The lamp is further used for freshness preservation of fresh cut roses, pulse width modulation technology(PWM) is used to achieve dynamic adjustment of the spectrum, the weight loss rate of rose fresh weight and the content change of antioxidant substances such as flavone and other substances were investigated to explore the best light conditions for fresh-cut roses. The experimental results show that the light conditions and light duration that are most conducive to freshness preservation of fresh-cut roses are R+G and 6 h/24 h.关键词：plant light source;modern agriculture;LED;optical design;freshness preservation187|234|4更新时间：2020-08-12
- 摘要：In order to obtain the image with a small amount of computation and better quality through a new compression sampling method under the existing sampling conditions. we proposed a new algorithm to achieve the goal. First, the image was projected onto the partitioned digital micro-mirror device(DMD), and the measured values of the image were obtained at low resolution. The low resolution image was reconstructed by the compressive sensing reconstruction algorithm. Then the important wavelet positions were predicted by the extended wavelet tree, and the digital micro-mirror device was used in the wavelet domain. Sampling acquired the details of the image, and finally the high-resolution image was restored by inverse wavelet transform. We compared our algorithm with TVAL3 which was the most commonly used minimization total variational algorithm in compressive sensing image reconstruction and EWT-ACS which was the recently proposed extended wavelet tree-based adaptive imaging algorithm. The results show that when the objective is image boat without noise, our algorithm is 4.36 dB and 2.87 dB higher than TVAL3 algorithm and EWT-ACS algorithm when the compressed sensing ratio is 0.75 and the total sampling ratio is 10%. We also analyzed the results of three algorithms when the image is contaminated by noise. This method greatly reduces the running time of compressive sensing reconstruction algorithm, while reducing the number of sampling, has a good anti-noise.关键词：compressed sensing;compressed sampling;wavelet tree;digital micro-mirror device138|123|1更新时间：2020-08-12
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