铯原子nP_(3/2)(n=70—94)里德伯态的紫外单光子激发及量子亏损测量

基于成熟的光纤激光器、光纤放大器及高效激光频率转换技术,我们在实验中研制了一套瓦级输出的窄线宽连续波单频可调谐318.6 nm紫外激光系统,并在室温铯原子气室中实现了6S_(1/2)—nP_(3/2)(n=70—94)单光子跃迁里德伯激发.借助由铯原子6S_(1/2)(F=4)基态、6P_(3/2)(F′=5)激发态和nP_(3/2)(n=70—94)里德伯态构成的V型三能级系统,通过频率锁定于铯原子6S_(1/2)(F=4)—6P_(3/2)(F′=5)超精细跃迁的852.3 nm探测光束的吸收减弱信号获得了里德伯态的信息,并利用高精度波长计测量了铯原子nP_(3/2)(n=70—94)里德伯态的量子亏损值.经过与理论计算值的变化趋势进行对比,我们认为由于原子气室的里德伯屏蔽效应并不能完全屏蔽外部直流电场,铯原子气室内存在残余的直流电场,影响了对里德伯态的量子亏损值的实验测量.利用残余直流电场的Stark效应理论模型及其与有效主量子数n*的依赖关系,对铯原子里德伯态的量子亏损实验测量值进行了修正.修正后的铯原子nP_(3/2)(n=70—94)态量子亏损测量值为3.5591±0.0007,与理论计算值相吻合.     

Magnetospectroscopy of double HgTe/CdHgTe QWs with inverted band structure in high magnetic fields up to 30 T

Magnetoabsorption in far and mid IR ranges in double HgTe/CdHgTe quantum wells with inverted band structure has been studied in high magnetic fields up to 30 T. Numerous intraband and interband transitions have been revealed in the spectra and interpreted within axial 8 × 8 k·p model. Splitting of dominant magnetoabsorption lines resulting from optical transitions from hole-like zero-mode Landau level has been discovered and discussed in terms of a built-in electric field and collective phenomena.     

Characterization techniques of sandwich-type TiO2/QD composites for low-cost quantum dots' solar cell

There is a high impact of the solar cells on energy manufacturing. For several years the energy efficiency was limited due to base-materials' structural and technological limits. High increase of energy harvesting of solar cells has been observed since the first solar cell based on dye-sensitized colloidal TiO₂ films occurred. One of the most promising solutions are used quantum dots (QD) for light energy conversion. In this paper, we described the use of selected characterization techniques for sandwich-type TiO₂/QD composites for a low-cost quantum dots' solar cell in the point of view of mass manufacturer of solar cells and research and development laboratory. Moreover, the increasing role of Raman spectroscopy and mapping for the TiO₂/QD was presented and compared with other necessity techniques for solar cell investigations such as ellipsometry, atomic force microscopy (AFM), and secondary ion mass spectrometry (SIMS).     

CdSe quantum dots in chiral smectic C matrix: experimental evidence of smectic layer distortion by small and wide angle X-ray scattering and subsequent effect on electro-optical parameters

CdSe quantum dots (QDs) dispersed ferroelectric liquid crystal (FLC) has been subjected to small and wide-angle X-ray scattering and atomic force microscopy to understand the molecular organization in chiral smectic C (SmC*) phase. SAXS indicates that the presence of QDs causes enhancement in the smectic layer separation. The smectic order parameter for neat FLC and FLC–QDs mixtures is obtained in the range of 0.6 to 0.85. Both smectic order parameter and structural tilt are found to be lesser for FLC–QDs mixtures as compared to neat FLC. The insertion of QDs in SmC* matrix causes localized smectic layer distortion in such a way that spontaneous polarization remains almost the same but the electro-optic switching of molecules becomes faster. We have outlined the superiority of FLC–QDs mixtures for electrical energy storage and their suitability in electronic devices.     

废水中有机污染物降解机理的研究方法

我国废水排放总量较大,且废水中含有的多种有机污染物一直是人类生命健康的潜在威胁,因此对废水处理的研究必不可少,而理解废水中有机污染物的降解机理是处理各种废水的基础.本综述概述了国内外针对各种有机污染物降解机理的研究方法,主要包括实验手段和计算模拟两大类.实验手段中主要采用光谱分析技术检测有机污染物降解过程中生成的中间产物,进而推测有机污染物的降解路径.但是由于实验条件和实验方法的不同,对于同种物质的降解机理研究,不同的实验结果存在着争议.基于量子化学计算、定量构效关系模型（QSAR）、定量结构-生物降解性能关系模型（QSBR）、统计分子碎化模型（SMF）等计算模拟方法为有机污染物降解机理的研究提供了新的方法.将实验手段和计算模拟有机结合起来,可为有机污染物的降解机理研究提供参考和指导.     

A Reaction-Induced Localization of Spin Density Enables Thermal C−H Bond Activation of Methane by Pristine FeC4+

The reactivity of the cationic metal-carbon cluster FeC₄⁺ towards methane has been studied experimentally using Fourier-transform ion cyclotron resonance mass spectrometry and computationally by high-level quantum chemical calculations. At room temperature, FeC₄H⁺ is formed as the main ionic product, and the experimental findings are substantiated by labeling experiments. According to extensive quantum chemical calculations, the C−H bond activation step proceeds through a radical-based hydrogen-atom transfer (HAT) mechanism. This finding is quite unexpected because the initial spin density at the terminal carbon atom of FeC₄⁺, which serves as the hydrogen acceptor site, is low. However, in the course of forming an encounter complex, an electron from the doubly occupied sp-orbital of the terminal carbon atom of FeC₄⁺ migrates to the singly occupied π*-orbital; the latter is delocalized over the entire carbon chain. Thus, a highly localized spin density is generated in situ at the terminal carbon atom. Consequently, homolytic C−H bond activation occurs without the obligation to pay a considerable energy penalty that is usually required for HAT involving closed-shell acceptor sites. The mechanistic insights provided by this combined experimental/computational study extend the understanding of methane activation by transition-metal carbides and add a new facet to the dizzying mechanistic landscape of hydrogen-atom transfer.     

两种基于酰腙配体的镍配合物:水热合成、结构、抗癌活性与量化计算

分别以吡啶和4,4′-联吡啶为第二配体采用水热法合成了2种酰腙镍配合物[Ni(Lss)(Py)](1)和[Ni2(Lrr)2(4,4′-bipy)](2),其中H2Lss=5-硝基水杨醛缩噻吩-2-甲酰腙,H2Lrr=5-溴水杨醛缩噻吩-2-甲酰腙,并通过元素分析、红外光谱和紫外光谱等进行了表征。X射线单晶衍射分析表明1和2的晶体分别属正交晶系Pbca空间群和单斜晶系P21/c空间群。1和2对人白血病细胞HL-60具较强的抑制活性,半数抑制浓度IC50分别为0.476和3.85μg·m L-1。采用密度泛函理论(DFT)对配合物2分子的自然电荷布居和键级进行了分析。     

Highly-efficient photosensitizer based on AIEgen-decorated porphyrin for protein photocleaving

An AIEgen decorated porphyrin(TPETPyP) was easily obtained through a one-step reaction.The bulky TPE in TPETPyP greatly impeded the intermolecular π-π stacking of the porphyrin core,which significantly suppressed aggregation-caused quenching(ACQ) effect of TPETPyP in aqueous solution.The four pyridinium salts formed in TPETPyP also render the whole molecule water solubility,which eliminated its aggregation.TPETPyP exhibited ~1 O_2 quantum yield as high as 0.85 in PBS.Moreover,it also showed high binding affinity to proteins,the major biotarget of ~1 O_2.The high ~1 O_2 quantum yield plus the great binding ability of TPETPyP toward proteins makes it a highly-efficient protein photocleaving agent.Protein electrophoresis experiments demonstrated that TPETPyP can photocleave BSA upon visible light irradiation,indicating that TPETPy P can act as a promising photosensitizer(PS) in PDT.The work here will provide a facile strategy to utilize AIEgens modified traditional PSs for photodynamic therapy(PDT).