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151.
Xing Chen Dr. Guoyun Meng Guanming Liao Dr. Florian Rauch Dr. Jiang He Dr. Alexandra Friedrich Prof. Dr. Todd B. Marder Dr. Nan Wang Dr. Pangkuan Chen Prof. Dr. Suning Wang Dr. Xiaodong Yin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(20):6274-6282
A series of 9-borafluorene derivatives, functionalised with electron-donating groups, have been prepared. Some of these 9-borafluorene compounds exhibit strong yellowish emission in solution and in the solid state with relatively high quantum yields (up to 73.6 % for FMesB-Cz as a neat film). The results suggest that the highly twisted donor groups suppress charge transfer, but the intrinsic photophysical properties of the 9-borafluorene systems remain. The new compounds showed enhanced stability towards the atmosphere, and exhibited excellent thermal stability, revealing their potential for application in materials science. Organic light-emitting diode (OLED) devices were fabricated with two of the highly emissive compounds, and they exhibited strong yellow-greenish electroluminescence, with a maximum luminance intensity of >22 000 cd m−2. These are the first two examples of 9-borafluorene derivatives being used as light-emitting materials in OLED devices, and they have enabled us to achieve a balance between maintaining their intrinsic properties while improving their stability. 相似文献
152.
在葡萄糖水溶液中合成得到平均粒径为5 nm的α-Ni(OH)2超微纳米粒子。研究结果发现,在水溶液中葡萄糖浓度能够控制α-Ni(OH)2纳米粒子粒径的大小,我们对其中的原理进行了剖析。当没有葡萄糖存在时,合成得到的Ni(OH)2晶型为β型,且颗粒粒径尺寸分布为微米级别。另外,研究发现α-Ni(OH)2超微纳米粒子室温下对中性水溶液中Li^+具有较强的吸附性能,且这种吸附性能随粒径的减小而剧烈增大;粒径为5 nm的α-Ni(OH)2粒子对Li^+的最大吸附量为214 mg·g^-1(远大于文献报道的有关吸附剂对Li^+的吸附容量),而粒径为1μm的β-Ni(OH)2在相同条件下对Li^+的最大吸附量低于30 mg·g^-1。计算分析表明,Li^+在α-Ni(OH)2纳米粒子表面吸附满足Freundlich方程,符合层层吸附模型。 相似文献
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157.
Shuxian Liu Yanling Zhao Nan Zeng Tiantian Liu Yaming Zhang Bin Han Jianyu Li Lifu Wang Ruilin Wang Man Gong Yonggang Li Xiaohe Xiao 《Journal of Thermal Analysis and Calorimetry》2014,116(1):491-497
The anti-Escherichia coli activities of four extracts in leaves of Dracontomelon dao, a traditional folk herb in China were investigated and compared by microcalorimetry. The four extracts are PE fraction, CHCl3 fraction, EtOAc fraction, and n-BuOH fraction. The heat flow power–time (HFP–time) curves of E. coli growth in the presence of the four extracts were measured using an ampoule method. Then the nine thermal kinetic parameters were obtained from the curves. From the result of principal component analysis, it can be seen that parameters k 1, k 2, P 1, and Q p2 might be the main parameters in evaluating the anti-E. coli effects. In the presence of CHCl3 fraction, EtOAc fraction, and n-BuOH fraction, k 2, Q p2 of E. coli decreased with increasing concentrations of the extracts. The EtOAc fraction was observed to have the strongest anti-bacterial activity with half-inhibitory concentration IC50 of 98.5 μg mL?1. So, it can be concluded that EtOAc fraction can be further developed as anti-bacterial bioactive fraction of leaves of Dracontomelon dao. 相似文献
158.
Reactivity of Oxygen Radical Anions Bound to Scandia Nanoparticles in the Gas Phase: CH Bond Activation
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Li‐Hua Tian Jing‐Heng Meng Dr. Xiao‐Nan Wu Dr. Yan‐Xia Zhao Dr. Xun‐Lei Ding Prof. Dr. Sheng‐Gui He Dr. Tong‐Mei Ma 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(4):1167-1175
The activation of C?H bonds in alkanes is currently a hot research topic in chemistry. The atomic oxygen radical anion (O?.) is an important species in C?H activation. The mechanistic details of C?H activation by O?. radicals can be well understood by studying the reactions between O?. containing transition metal oxide clusters and alkanes. Here the reactivity of scandium oxide cluster anions toward n‐butane was studied by using a high‐resolution time‐of‐flight mass spectrometer coupled with a fast flow reactor. Hydrogen atom abstraction (HAA) from n‐butane by (Sc2O3)NO? (N=1–18) clusters was observed. The reactivity of (Sc2O3)NO? (N=1–18) clusters is significantly sizedependent and the highest reactivity was observed for N=4 (Sc8O13?) and 12 (Sc24O37?). Larger (Sc2O3)NO? clusters generally have higher reactivity than the smaller ones. Density functional theory calculations were performed to interpret the reactivity of (Sc2O3)NO? (N=1–5) clusters, which were found to contain the O?. radicals as the active sites. The local charge environment around the O?. radicals was demonstrated to control the experimentally observed size‐dependent reactivity. This work is among the first to report HAA reactivity of cluster anions with dimensions up to nanosize toward alkane molecules. The anionic O?. containing scandium oxide clusters are found to be more reactive than the corresponding cationic ones in the C?H bond activation. 相似文献
159.
Thermal Ethane Activation by Bare [V2O5]+ and [Nb2O5]+ Cluster Cations: on the Origin of Their Different Reactivities
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Dr. Xiao‐Nan Wu Dr. Shi‐Ya Tang Dr. Hai‐Tao Zhao Dr. Thomas Weiske Dr. Maria Schlangen Prof. Dr. Helmut Schwarz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(22):6672-6677
The gas‐phase reactivity of [V2O5]+ and [Nb2O5]+ towards ethane has been investigated by means of mass spectrometry and density functional theory (DFT) calculations. The two metal oxides give rise to the formation of quite different reaction products; for example, the direct room‐temperature conversions C2H6→C2H5OH or C2H6→CH3CHO are brought about solely by [V2O5]+. In distinct contrast, for the couple [Nb2O5]+/C2H6, one observes only single and double hydrogen‐atom abstraction from the hydrocarbon. DFT calculations reveal that different modes of attack in the initial phase of C?H bond activation together with quite different bond‐dissociation energies of the M?O bonds cause the rather varying reactivities of [V2O5]+ and [Nb2O5]+ towards ethane. The gas‐phase generation of acetaldehyde from ethane by bare [V2O5]+ may provide mechanistic insight in the related vanadium‐catalyzed large‐scale process. 相似文献
160.
采用PVT膨胀仪测试了添加不同防老剂的天然橡胶(NR)复合材料的压力-体积-温度(P-V-T)属性,通过最小二乘法拟合得到Tait方程参数,预测了体系的热膨胀系数(α)和等温压缩系数(β),结果表明,Tait状态方程可用来预测该复合材料体系的P-V-T行为,NR复合材料的α值随着压力的增大而减小,随温度变化不明显;β值随压力的增大而减小,且随着温度的升高而升高.分子模拟结果观察了体系凝聚态结构在不同温度下的变化,表明其变化原因是升温使体系自由体积增大,分子链的活动性增强,同时观察到单独加入防老剂4010NA或防老剂RD的体系α和β的值较大,说明其尺寸稳定性差,而当同时加入4010NA和RD进行防老剂并用时,体系的α和β值均较小,表明此复合材料体系不容易产生变形;通过分子动力学模拟手段计算了NR复合材料的内聚能密度(CED)随温度的变化规律,对于2种防老剂并用的体系,其CED比较大,说明分子间相互作用力较强,从而体系尺寸稳定性好,受温度和压力的影响小. 相似文献