Thermal Non‐Oxidative Aromatization of Light Alkanes Catalyzed by Gallium Nitride

The thermal catalytic activity of GaN in non‐oxidative alkane dehydroaromatization has been discovered for the first time. The origin of the catalytic activity was studied experimentally and theoretically. Commercially available GaN powders with a wurtzite crystal structure showed superior stability and reactivity for converting light alkanes, including methane, propane, n‐butane, n‐hexane and cyclohexane into benzene at an elevated temperature with high selectivity. The catalyst is highly robust and can be used repeatedly without noticeable deactivation.     

视频台上光学演示实验组合装置

本文介绍可在多媒体视频展示台上完成多种光学演示实验的组合装置。     

迈克耳逊干涉仪实验中的等倾与等厚干涉

本仔细讨论了在面光源照明下用肉眼直接观察的迈克耳逊干涉仪实验中产生的干涉条纹形状，指出等倾干涉和等厚干涉的实验条件，从而帮助学生加深对这两种干涉条纹的理解和判别。     

A Bulky Pyridinyl?uorene/Triphenylamine Hybrid Used as Host Material for Heavily‐Doped Blue Electrophosphorescent Devices

In this work, a novel molecule pyridinyl?uorene/triphenylamine hybrid ( TPyFTPA ) with bulky steric hindrance effects has been synthesized successfully by substituting 9‐(pyridine‐2‐yl)‐fluoren‐9‐yl with triphenylamine (TPA) via Friedel‐Crafts reaction, which possesses good thermal stability and triplet energy (E_T) of 420°C with 5% weight loss and 2.86 eV, respectively. Moreover, the bulky steric hindrance material shows high stable morphology by heating to 200°C without finding melting phenomena and crystallization that is demonstrated by differential scanning calorimetry (DSC) curve. The bulky pyridinyl?uorene end‐capped TPA has been used as host material for blue phosphorescent organic light‐emitting diodes (PhOLEDs) with maximum external quantum efficiencies (EQEs) of 2.7%, 3.7%, and 3.5%, at the doping ratios of 10%, 30%, and 40%, respectively. The performances of TPyFTPA ‐based blue PhOLEDs own wide concentration ranging from 10% to 40%, which indicates the bulky TPyFTPA might be a potential candidate for inexpensive products with simplifying process for the applications in full‐color display and solid state lighting.     

Melting and glass transition for Ni clusters

The melting of NiN clusters (N = 29, 50-150) has been investigated by using molecular dynamics (MD) simulations with a quantum corrected Sutton-Chen (Q-SC) many-body potential. Surface melting for Ni147, direct melting for Ni79, and the glass transition for Ni29 have been found, and those melting points are equal to 540, 680, and 940 K, respectively. It shows that the melting temperatures are not only size-dependent but also a symmetrical structure effect; in the neighborhood of the clusters, the cluster with higher symmetry has a higher melting point. From the reciprocal slopes of the caloric curves, the specific heats are obtained as 4.1 kB per atom for the liquid and 3.1 kB per atom for the solid; these values are not influenced by the cluster size apart in the transition region. The calculated results also show that latent heat of fusion is the dominant effect on the melting temperatures (Tm), and the relationship between S and L is given.     

Spectroscopic properties of Er(3+)/Yb(3+) co-doped Bi(2)O(3)-B(2)O(3)-GeO(2) glasses

Er(3+)/Yb(3+) co-doped 60Bi(2)O(3)-(40 - x)B(2)O(3)-xGeO(2) (BBG; x=0, 5, 10, 15 mol%) glasses that are suitable for fiber lasers, amplifiers have been fabricated and characterized. The absorption spectra, emission spectra, and lifetime of the (4)I(13/2) level and quantum efficiency of Er(3+):(4)I(13/2) --> (4)I(15/2) transition were measured and calculated. With the substitution of GeO(2) for B(2)O(3), both Delta lambda(eff) and sigma(e) decrease from 75 to 71 nm and 9.88 to 8.12 x 10(-21) cm(2), respectively. The measured lifetime of the (4)I(13/2) level and quantum efficiency of Er(3+):(4)I(13/2) --> (4)I(15/2) transition increase from 1.18 to 1.5 ms and 36.2% to 43.2%, respectively. The emission spectra of Er(3+):(4)I(13/2) --> (4)I(15/2) transition was also analyzed using a peak-fit routine, and an equivalent four-level system was proposed to estimate the stark splitting for the (4)I(15/2) and (4)I(13/2) levels of Er(3+) in the BBG glasses. The results indicate that the (4)I(13/2) --> (4)I(15/2) emission of Er(3+) can be exhibit a considerable broadening due to a significant enhance the peak A, and D emission.     

Strong visible up-conversion emission in Tb3+, Tm3+ and Tb3+-Tm3+ co-doped tellurite glasses sensitized by Yb3+

Up-conversion luminescence characteristics under 975 nm excitation have been investigated with Tb3+/Tm3+/Yb3+ triply doped tellurite glasses. Here, green (547 nm: (5)D(4)-->(7)F(4)) and red (660 nm: (5)D(4)-->(7)F(2)) up-conversion (UC) luminescence originating from Tb3+ is observed strongly, because of the quadratic dependences of emission intensities on the excitation power. Especially, the UC luminescence was intensified violently with the energy transfer from the Tm3+ ions involves in the Tb3+ excitation. To the Tb3+/Tm3+/Yb3+ triply doped glass system, a novel up-conversion mechanism is proposed as follows: the energy of (3)G(4) level (Tm3+) was transferred to (5)D(4) (Tb(3+)) and the 477-nm UC luminescence of Tm3+ was nearly quenched.     

超导体电输运及交流磁化率双模式测量系统研制

介绍了一种基于小型制冷机的超导转变温度电输运和交流磁化率双模式单腔测量装置。该装置包括电输运法测量和交流磁化率法测量两部分,分别实现对高温超导薄膜样品的超导转变温度的测量。电输运法测量部分利用四点法测量原理对超导薄膜的电阻进行测量,获取电阻随温度变化的曲线;同时利用电流换向法消除热电势带来的测量误差,以进一步提高测量的精度。交流磁化率法测量部分利用的是电磁感应原理和超导磁效应。该部分包含有初级线圈和次级线圈,超导样品放置于两线圈之间。初级线圈用于产生交变激励磁场,次级线圈的输出信号反应了超导样品磁化率的变化,其输出信号由锁相放大器获取。测量过程中使用计算机自动记录测量数据。     

Ammonia borane as a metal free reductant for ketones and aldehydes: a mechanistic study

Without a catalyst ketones and aldehydes were reacted in THF with ammonia borane (AB) to proceed hydroboration forming alkyl borates. Mechanistic studies revealed that dissociation of ammonia from AB occurred before the hydroboration step. When methanol was used as the solvent, metal free methanolysis of AB would take place with the ketone/aldehyde being directly hydrogenated by the MeOH·BH₃ complex.     

Facile metal free regioselective transfer hydrogenation of polarized olefins with ammonia borane

Transfer hydrogenation of polarized olefins bearing strongly electron-withdrawing groups on one side of the double bond was achieved with ammonia borane under mild conditions without using a catalyst. Mechanistic studies proved the character of the direct H transfers proceeding stepwise with a unique hydroboration intermediate and hydride before proton transfer.