最新刊期
卷 36 ， 期 7 ， 2015
- 摘要：In recent years, fluorescent semiconducting polymer nanoparticles, which primarily consist of π-conjugated polymers, have been attracted considerable attention in an extensive range of applications, such as fluorescence imaging and biosensing. These π-conjugated polymer nanoparticles are called polymer dots (Pdots) when they have particle size comparable to that of the inorganic quantum dots. Pdots have many charming properties, such as large absorption cross section, high fluorescence quantum yield, very fast emission rates, excellent photostability, and so on. In this review, we briefly summarize recent findings of the photophysical properties of Pdots, the surface functionalization and biomolecular conjugation of Pdots and their applications in cellular labeling, in vivo imaging, biosensing, single-particle tracking, drug delivery and photodynamic therapy.关键词：semiconducting polymer;quantum dots;fluorescent probes;single particle tracking;biological imaging274|240|3更新时间：2020-08-12
- 摘要：The upconversion luminescence of Mn2+ doped transparent germanate glass induced by 800 nm femtosecond laser at room temperature was investigated. The excitation and emission spectra show that the excitation process stems from the 6A(6S)→4E(4G)/4A1(4G) transition while the emission originates from the 4T1(4G)→6A1(6S) transition of Mn2+. The emission spectrum excited by 409 nm monochromatic light is similar to that irradiated by 800 nm femtosecond laser. Moreover, by measuring the dependence of the fluorescence intensity on the pump power together with the absorption spectra of both the undoped and doped glass, the conversion of infrared radiation to the visible emission dominated by a two-photon absorption process is confirmed. As Mn2+ is the only emission center, a significant red-shift with the increasing of Mn2+ concentration is also observed.关键词：upconversion;luminescence;femtosecond laser;Mn2+ ;two-photon absorption120|194|6更新时间：2020-08-12
- 摘要：Surface initial growth process of GaN film in MOVPE is studied by DFT theory of quantum chemistry. By calculating the adsorption energies of GaCH3 and NH3 at main adsorption sites of GaN (0001)-Ga surface, it is found that energies of GaCH3 at four adsorption sites are similar, thus GaCH3 is easy to diffuse on the surface. The energies of NH3 at four adsorption sites are much different. The most stable adsorption site for NH3 is Top, and the large energy barrier exist for NH3 migrating from Top to other sites. Based on the energy analysis, the initial GaN surface growth mechanism is proposed for GaN (0001)-Ga surface, with NH3 and GaCH3 as growth precursor and ring structured core as final form. In the process of the ring structured core growth, the first GaN core growth need three NH3 and one GaCH3, which can be expressed as Ga(NH2)3. The second GaN core growth can use one existing N as coordination atom, so only two NH3 and one GaCH3 are needed. The two GaN core can be expressed as (NH2)2 Ga-NH-Ga (NH2)2. The third GaN core growth can use two existing N as coordination atoms, so only one NH3 and one GaCH3 are needed. The third GaN core forms a ring structure which can be expressed as Ga3(NH)3(NH2)3. The subsequent growth will repeat the process of the second and third core growth, so as to realize the continuous steps of GaN film growth.关键词：GaN;MOVPE;DFT;surface reaction151|127|2更新时间：2020-08-12
- 摘要：GdBO3:Pr3+ and GdBO3:Pr3+,Yb3+ samples were prepared by solid state reaction at high temperature. XRD patterns, excitation spectra and emission spectra in the Vis-NIR range of the obtained samples were studied in detail at room temperature. The emission of 2F5/2→2F7/2(980 nm) of Yb3+ was observed under 446 nm excitation, indicating the occurrence of the energy transfer from Pr3+ to Yb3+. The fluorescence intensities varied with different Yb3+ doping concentrations. Luminescence decay curves of Pr3+:3P0 level were recorded as a function of the Yb3+ concentrations and energy transfer efficiency was also calculated. Based on Inokuti-Hirayama model, the energy transfer type from Pr3+ to Yb3+ was derived to be electric dipole-dipole interaction.关键词：near infrared;energy transfer;rare earth ions;GdBO3171|108|5更新时间：2020-08-12
- 摘要：The field ionization process of Eu 4f76snp Rydberg states converging to the first ionization limit 4f76s 9S4 was systematically investigated. Firstly, the spectra of Rydberg states 4f76snp of Eu atom were measured using the three-step laser excitation and electric field ionization (EFI) method. Secondly, the EFI pulse(pulse width of 0.2 μs)was applied after laser excitation. Then, we continuously scan field ionization voltage to observe the EFI process,and to realize the potential of field ionization we need to understand what happens to the atoms as the pulse field rises from 0 to 3 kV. The exact location of ionization threshold can be obtained when the peak of ionization field changes. Especially, above the threshold, some structures are found due to black body radiation (BBR).关键词：Eu atom;Rydberg state;field ionization;ionization threshold122|167|0更新时间：2020-08-12
- 摘要：Three kinds of Europium complexes, Eu(Hhqc)3(TEL), Eu(Hhqc)3(TPL) and Eu-(Hhqc)3(TBL) were synthesized by the reaction of 2-hydroxyquinoline-4-carboxylic acid (H2hqc) with EuCl3·6H2O under the treatment with triethylamine (TEL), tripropylamine (TPL) and tributylamine (TBL), respectively. Three complexes were characterized by elemental analysis, thermogravimetric analysis, molar conductivity, UV spectra, fluorescence spectra, fluorescence life-time and quantum yield methods. Each complex shows five emission bands at 580, 592, 613, 654, 702 nm, which are assigned to the characteristic emission 5D0→7FJ(J=0, 1, 2, 3, 4) transitions of Eu3+. The fluorescence life-times are 2.22, 3.29, 3.31 ms, the quantum yields are 0.011, 0.019, and 0.028 for Eu(Hhqc)3(TEL), Eu(Hhqc)3(TPL) and Eu(Hhqc)3(TBL), respectively. The fluorescent intensities increase with the increasing of carbon chain length of the organic bases, indicating the organic bases are involved in the formation of europium complexes.关键词：europium complexes;organic amine;2-hydroxyquinoline-4-carboxylic acid;fluorescence life-time;quantum yield128|136|1更新时间：2020-08-12
- 摘要：In order to develop the photocatalytic activity of TiO2 under visible light as that under ultraviolet light to degrade indoor ormaldehyde pollution, a visible light response photocatalyst consisting of TiO2 and upconversion luminescence agent Er3+:YAlO3 was prepared using hydrothermal treatment method. The photocatalyst was characterized by X-ray diffractometer (XRD), UV-Vis diffuse reflectance spectrophotometer (DRS) and fluorescence spectrometer (FS).The prepared TiO2 is anatase-dominant. Er3+:YAlO3 can convert visible light to ultraviolet (UV) light to expand the absorption range of TiO2. The upconverted UV light can excite TiO2 effectively to produce active materials with strong oxidation ability. The photocatalyst was applied to degrade gaseous formaldehyde in the sealed reactor, and the effect of initial formaldehyde concentration and photocatalyst dosage on the degradation efficiency of formaldehyde were investigated. The results show that the prepared photocatalyst can efficiently degrade the formaldehyde. The apparent first order reaction rate constant for gaseous formaldehyde degradation is positively correlated with the initial formaldehyde concentration, but increases first then decreases with the increasing of photocatalyst dosage from 0.061 2 g/L to 0.234 8 g/L. When the formaldehyde concentration is 0.058 mg/m3 and the photocatalyst dosage is 0.122 4 g/L, the apparent first order reaction rate constant is the biggest of 3.65×10-3 min-1. The degradation follows Langmuir-Hinshelwood model, and the reaction rate constant is 5×10-8 mg/(L·min).关键词：upconversion luminescence agent;TiO2;visible light driven photocatalytic;formaldehyde125|158|3更新时间：2020-08-12
- 摘要：La2(MoO4)3 micro-materials with different morphologies were prepared by microemulsion reaction of sodium molybdate (Na2MoO4·2H2O) and lanthanum nitrate(La(NO3)3·6H2O) under the help of micro emulsion system. The morphology of La2(MoO4)3 samples gradually transform from oval shape to close spherical shape with the concentration of the surfactant of CTAB increasing from 0.2 mol/L to 0.4 mol/L. Under 396 nm excitation, La2(MoO4)3:Eu3+ samples calcined at 800 ℃ for 4 h emit 617 nm red light due to the forced electric dipole transition of 5D0→7F2. The emission is strongest when the mole fraction of Eu3+ is up to 20%.关键词：microemulsion;La2(MoO4)3:Eu3+;photoluminescence properties114|149|2更新时间：2020-08-12
- 摘要：Na2CO3 being used as the base and kernel, a new type of core-shell fluorescent material terbium complex was obtained by reaction of it with terbium and organic ligands acetylsalicylic acid (aspirin). The fluorescence micro images show that the composite materials emit bright green fluorescence which attribute to the emission of terbium ion. The excitation spectra shapes of the composite materials change with the varying of amount of sodium carbonate, demonstrating that the structures of terbium complexes on the surface of sodium carbonate are different. The fluorescence intensity of the composite material shows a downward trend with the increasing of the amount of sodium carbonate, and the average fluorescence lifetime shows an upward trend.关键词：sodium carbonate;terbium complexes;fluorescence;fluorescence lifetime;core-shell structure110|226|0更新时间：2020-08-12
- 摘要：Ag nanoprisms (AgNPs) were introduced in polymer solar cells to improve the light absorption and performance. By changing the size and morphology of AgNPs, different plasmonic resonance characteristics were obtained. The device with good spectral overlap between AgNPs SPRs and active layer exhibited the highest photocurrent. The influence of electromagnetic scattering by AgNPs in the polymer solar cell was further investigated by changing the thickness of PEDOT:PSS buffer layer. It is found that more local electromagnetic near-fields couple to the photoactive layer with the decreasing of the thickness of PEDOT:PSS layer. By optimizing the thickness of PEDOT:PSS buffer layer and the spectral overlap between Ag nanoprisms and active layer, the power conversion efficiency of polymer solar cells with a structure of ITO/AgNPs/PEDOT:PSS/P3HT:PCBM/LiF/Al is raised to 3.82%, which is 1.26 times than that of the control device without AgNPs layer.关键词：plasmon;Ag nanoprisms;power conversion efficiency;polymer solar cells100|243|1更新时间：2020-08-12
- 摘要：A multi-level resistive memory device based on the single-layered dense ZnO nanorod arrays was prepared. The mechanisms of current conduction and resistive switching were studied by I-V curve and bias dependence of fluorescence spectra. The dominant conduction mechanisms for the two resistance states are concluded to be Ohmic conduction and space-charge-limited-current (SCLC) conduction, respectively. It is considered that the oxygen vacancies density at the surface depletion region of nanorods is influenced by charge loss in defects of V0 and V+. The increased oxygen vacancies density under forward bias is obtained to build the conductive paths for the electron transportation, resulting in the switching from the high resistance state to the low resistance state. The high resistance state is re-obtained with the paths broken off under reverse voltage.关键词：ZnO nanorods;fluorescence spectra;oxygen vacancies;conductive paths90|97|1更新时间：2020-08-12
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- 摘要：In order to solve the problem of poor stability of high contrast gratings (HCGs) for 850 nm VCSEL, a new type of Si/SiO2 HCGs was put forward. The influence of grating parameters on HCG reflectivity of 850 nm was studied. The influence of the grating parameters, such as height, fill factor, duty, etching depth, angle, on the reflectivity of Si/SiO2 HCGs for 850 nm was simulated and analyzed by the finite element analysis software. For the 850 nm TE light incidence from SiO2 to the rectangular HCGs, it is found that only when the angle of gating is greater than 88°, can the reflectivity of HCGs be greater than 0.995, and other parameters of HCGs have a larger tolerance.关键词：gratings;high contrast gratings;highly reflectivity;finite element analysis106|125|5更新时间：2020-08-12
- 摘要：SnS thin films were grown by pulsed laser deposition on glass substrates at room temperature, and then the deposited films were rapidly annealed at 200, 300, 400, 500, 600 ℃ under flowing argon atmosphere. The effects of rapid thermal annealing(RTA) temperature on the microstructural, morphological, optical properties and electrical properties of SnS thin films were studied by X-ray diffraction(XRD), laser Raman spectrometry(Raman), atomic force microscopy(AFM), field emission scanning electron microscopy (FESEM), ultraviolet-visible-near infrared spectrophotometer (UV-Vis-NIR) and Keithley 4200-SCS semiconductor parameter analyzer. The results show that SnS thin films grow preferentially oriented in the (111) direction, and the crystalline quality of SnS thin films is the best at 400 ℃. Raman characteristic peaks of SnS appear in Raman spectra of the thin films. While the increasing of the annealing temperature, the thickness of the films gradually decrease whereas the average particle sizes of the films increase. The absorption coefficient in the visible region is in the order of 105 cm-1 at different thermal annealing temperature. The direct bandgap of the film is 1.92 eV at 400 ℃. With the increasing of the thermal annealing temperature from 300 to 500 ℃, the resistivity of the films decreases from 1.85×104 to 14.97 Ω·cm.关键词：SnS thin film;pulsed laser deposition;rapid thermal annealing;optical properties147|179|0更新时间：2020-08-12
- 摘要：Two types of white organic light-emitting devices (WOLED) containing a layered light-emitting region composed of a single blue-emitting host and different fluorescent dopants (blue and orange) were fabricated. The efficiency, lifetime, brightness, spectral voltage-dependence and white balance of devices were investigated. The results show that the performance of the devices strongly depends on the stack order of two emitting layers and the thickness of the emitting layer. It is found that the WOLED with an EML sequence of orange/blue (from anode to cathode) shows better stability than that with an EML sequence of blue/orange. It is due to the rubrene in orange emitting layer that acts as hole-trap sites and captures the passing holes and hence balances the concentration of electrons and holes. The optimized white device exhibits a favorable CIE coordinates (0.320 1, 0.345 9) which is close to the standard white light.关键词：organic electroluminescent;light-emitting layer sequence and thickness;carrier injection;carrier balance99|125|0更新时间：2020-08-12
- 摘要：Sr-F codoped SnO2 (SFTO) transparent conductive oxide films were prepared by ion-assisted electron beam deposition at a low temperature. The films show electrical resistivity of less than 3.9×10-3 Ω·cm, high average optical transmittance of 85% from 380 nm to 2 500 nm, and high work function of about 5.1 eV. The films are amorphous and have favorable surface morphology with average roughness of about 1.5 nm. The deposition temperature of SFTO film is 300 ℃, which is much lower than that of FTO products. SFTO transparent conductive amorphous thin film can be expected to be directly prepared on flexible plastic (PI, PAR or PCO) substrate, in order to obtain flexible electrodes with good performance.关键词：transparent conductive film;non-indium;SnO2;semiconductor doping123|78|1更新时间：2020-08-12
- 摘要：A novel A-D-A blue emitter containing fluorene, phenanthroimidazole and acetylene group moieties was synthesized and characterized, named as FI. Its photophysical and photochemical properties were systematically investigated. The results showed FI exhibits excellent solubility, fluorescence, thermal stability and film formation, which is a good candidate for the fabrication of solution-processable organic light-emitting diodes. A non-doped blue organic light-emitting diode based on FI as the emitter showed the maximum luminance efficiency of 1.52 cd·A-1, and the maximum power efficiency could reach 0.63 lm·W-1.关键词：fluorene derivatives;solution-processable;blue OLEDs150|175|0更新时间：2020-08-12
- 摘要：The heat generation and heat transfer mechanisms of organic light-emitting diodes (OLEDs) were investigated. Heat is generated in the carrier recombination and then dissipated by thermal radiation and convection. Based on theoretical calculations of heat transfer, we find that at the case of the luminance of 1 000 cd/m2, 15% of the input power is converted to light, while 30% and 55% of the input power are converted to heat by thermal radiation and convection, respectively. The calculated temperature rise of the device is 39.4 ℃ which fits well with the measured value of 39.3 ℃. The factors affecting the temperature of OLEDs are ambient temperature, materials and input power. The brightness of OLEDs decays at different rates for different light-emitting materials.关键词：organic light-emitting diodes;thermal radiation;thermal convection108|159|0更新时间：2020-08-12
- 摘要：The plate-fin heat sink is widely used in LED lamp for application of multi-angle illumination. According to the key structures of a LED projection lamp, the orientation effects on heat dissipation performance of plate-fin heat sink with natural convection cooling were researched under 3 driving currents and 7 inclination angles between illumination direction and gravity direction. Based on the validity and accuracy of numerical simulation verified by experimental results, the thermal mechanisms with respect to maximum excess temperature and temperature uniformity were investigated through analyzing temperature and flow data derived from numerical simulation. The obvious differences of air velocity distribution in the flow channel of fins are found among inclination angles, these differences are the main reason of sensitive orientation effect about maximum excess temperature and temperature uniformity. In addition, air velocity difference between upstream and downstream around the measuring point with maximum temperature can be used to quantitatively interpret the variation trend of temperature uniformity in different inclination angles. Furthermore, the effects of inclination angle and fin spacing on the maximum excess temperature were analyzed. The results show that the heat dissipation performance of plate-fin heat sink with optimal fin spacing has high orientation sensitivity, so the study of orientation effects on the air flow and heat transfer of plate-fin heat sinks is an indispensable task in the thermal design of LED with multi-angle illumination function.关键词：LED cooling;natural convection;plate-fin heat sink;numerical simulation;inclination angle138|139|4更新时间：2020-08-12
- 摘要：In enhanced chemiluminescence enzyme-linked immunoassay, major parameters such as detection result, efficiency of counting and S/N ratio, are related with not only photon counting devices but also statistics process of photon pulse emission in optical luminescence system. In this article, we measured the statistics characteristics of photon pulse in enhanced luminol chemiluminescence system and theoretically analyzed the design of photon counting detection device of chemiluminescence system by its statistics characteristics of its pulse emission time. The research suggests that the photon emission pulse intervals of chemiluminescence subject to Weibull distribution.关键词：enhanced chemiluminescence immunoassay;photon counting;statistical analysis131|213|3更新时间：2020-08-12
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