高分辨SPI/TOFMS的研制及VOCs分子式确定

单光子能量10.6eV的真空紫外灯可电离大部分的挥发性有机物,生成分子离子,几乎无碎片,谱图简单。本文介绍了实验室自制的真空紫外灯单光子电离反射式飞行时间质谱仪的原理、仪器结构及初步结果。测试仪器分辨率超过4000(FWHM),质量精度优于6ppm。苯的检出限可至52ppbv。将仪器用于香烟烟气和聚氯乙烯(PVC)热解产物的检测。结果表明,单光子软电离源与高分辨质谱的结合,可直接用于复杂挥发性有机物(VOCs)分子式的确定。     

SPECT reconstruction with sub‐sinogram acquisitions

Described herein are the advantages of using sub‐sinograms for single photon emission computed tomography image reconstruction. A sub‐sinogram is a sinogram acquired with an entire data acquisition protocol, but in a fraction of the total acquisition time. A total‐sinogram is the summation of all sub‐sinograms. Images can be reconstructed from the total‐sinogram or from sub‐sinograms and then be summed to produce the final image. For a linear reconstruction method such as the filtered backprojection algorithm, there is no advantage of using sub‐sinograms. However, for nonlinear methods such as the maximum likelihood (ML) expectation maximization algorithm, the use of sub‐sinograms can produce better results. The ML estimator is a random variable, and one ML reconstruction is one realization of the random variable. The ML solution is better obtained via the mean value of the random variable of the ML estimator. Sub‐sinograms can provide many realizations of the ML estimator. We show that the use of sub‐sinograms can produce better estimations for the ML solution than can the total‐sinogram and can also reduce the statistical noise within iteratively reconstructed images. © 2011 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 21, 247–252, 2011;     

Efficient flexible phosphorescent polymer light-emitting diodes based on silver nanowire-polymer composite electrode

Blue, green, and red electrophosphorescent polymer light-emitting diodes have been fabricated on silver nanowire-polymer composite electrode. The devices are 20%-50% more efficient than control devices on ITO/glass and exhibit small efficiency roll-off at high luminances. The blue PLEDs were repeatedly bent to 1.5 mm radius concave or convex with calculated strain in the emissive layer approximately 5% (tensile or compressive).     

基于FBG的多级延迟SBS结构的慢光系统研究

设计一种基于光纤布拉格光栅(FBG)的多级延迟受激布里渊散射(SBS)结构的慢光系统.实验中采用2个FBG和一段15 km标准单模光纤(SSMF),利用光栅不同的反射特性,使信号光和泵浦光可重复通过同一段光纤相互作用,在仅使用一段光纤情况下达到双级时延的效果,并且FBG对信号光同样具有一定的延迟.实验结果表明,在展宽S...     

Highly Efficient,Solution‐Processed,Single‐Layer,Electrophosphorescent Diodes and the Effect of Molecular Dipole Moment

A new family of highly soluble electrophosphorescent dopants based on a series of tris‐cyclometalated iridium(III) complexes (1–4) of 2‐(carbazol‐3‐yl)‐4/5‐R‐pyridine ligands with varying molecular dipole strengths have been synthesized. Highly efficient, solution‐processed, single‐layer, electrophosphorescent diodes utilizing these complexes have been prepared and characterized. The high triplet energy poly(9‐vinylcarbazole) PVK is used as a host polymer doped with 2‐(4‐biphenylyl)‐5‐(4‐tert‐butyl‐phenyl)‐1,3,4‐oxadiazole (PBD) for electron transport. Devices with a current efficiency of 40 cd A^?1 corresponding to an EQE of 12% can thus be achieved. The effect of the type and position of the substituent (electron‐withdrawing group (CF₃) and electron‐donating group (OMe)) on the molecular dipole moment of the complexes has been investigated. A correlation between the absorption strength of the singlet metal‐to‐ligand charge‐transfer (¹MLCT) transition and the luminance spectral red shift as a function of solvent polarity is observed. The strength of the transition dipole moments for complexes 1–4 has also been obtained from TD‐DFT computations, and is found to be consistent with the observed molecular dipole moments of these complexes. The relatively long lifetime of the excitons of the phosphorescence (microseconds) compared to the charge‐carrier scattering time (less than nanoseconds), allows the transition dipole moment to be considered as a “quasi permanent dipole”. Therefore, the carrier mobility is sufficiently affected by the long‐lived transition dipole moments of the phosphorescent molecules, which are randomly oriented in the medium. The dopant dipoles cause positional and energetic disorder because of the locally modified polarization energy. Furthermore, the electron‐withdrawing group CF₃ induces strong carrier dispersion that enhances the electron mobility. Therefore, the strong transition dipole moment in complexes 3 and 4 perturbs both electron and hole mobilities, yielding a reduction in exciton formation and an increase in the device dark current, thereby decreasing the device efficiency.     

Bipolar Tetraarylsilanes as Universal Hosts for Blue,Green, Orange,and White Electrophosphorescence with High Efficiency and Low Efficiency Roll‐Off

A series of tetraarylsilane compounds, namely p‐BISiTPA ( 1 ), m‐BISiTPA ( 2 ), p‐OXDSiTPA ( 3 ), m‐OXDSiTPA ( 4 ), are designed and synthesized by incorporating electron‐donating arylamine and electron‐accepting benzimidazole or oxadiazole into one molecule via a silicon‐bridge linkage mode. Their thermal, photophysical and electrochemical properties can be finely tuned through the different groups and linking topologies. The para‐disposition compounds 1 and 3 display higher glass transition temperatures, slightly lower HOMO levels and triplet energies than their meta‐disposition isomers 2 and 4 , respectively. The silicon‐interrupted conjugation of the electron‐donating and electron‐accepting segments gives these materials the following advantages: i) relative high triplet energies in the range of 2.69–2.73 eV; ii) HOMO/LUMO levels of the compounds mainly depend on the electron‐donating and electron‐accepting groups, respectively; iii) bipolar transporting feature as indicated by hole‐only and electron‐only devices. These advantages make these materials ideal universal hosts for multicolor phosphorescent OLEDs. 1 and 3 have been demonstrated as universal hosts for blue, green, orange and white electrophosphorescence, exhibiting high efficiencies and low efficiency roll‐off. For example, the devices hosted by 1 achieve maximum external quantum efficiencies of 16.1% for blue, 22.7% for green, 20.5% for orange, and 19.1% for white electrophosphorescence. Furthermore, the external quantum efficiencies are still as high as 14.2% for blue, 22.4% for green, 18.9% for orange, and 17.4% for white electrophosphorescence at a high luminance of 1000 cd m^?2. The two‐color, all‐phosphor white device hosted by 3 acquires a maximum current efficiency of 51.4 cd A^?1, and a maximum power efficiency of 51.9 lm W^?1. These values are among the highest for single emitting layer white PhOLEDs reported till now.     

Sensitive detection of infrared photons using a high-Q microcantilever

A new approach based on microcantilevers is presented to detect infrared photons with high sensitivity. Infrared photons are measured by monitoring the amplitude change of a vibrating microcantilever under light pressure force.The irradiating light is modulated into sinusoidal and pulsed waves,and to be in-phase and anti-phase with the cantilever driving signal.A linear relationship between the amplitude change of the cantilever and the light power distributing on the cantilever was observed.Under a vacuum of 10^-4 Pa,an infrared light power of 7.4 nW was detected with the cantilever.The in-phase and anti-phase modulation to the cantilever vibration using a pulsed light results in an enhanced response of the cantilever.