Temperature-induced chirality reversal of induced circular dichroism of premicellar aggregates of acridine orange derivatives and dodecanoyl-l-threonine in aqueous solution

Circular dichroism (CD) and absorption spectra were measured for acridine orange derivatives: 3,6-bis(dimethylamino) acridine (AO), 3,6-bis(dimethylamino)-10-methylacridinium bromide (C₁AO), and 3,6-bis(dimethylamino)-10-dodecylacridinium bromide (C₁₂AO) in aqueous dodecanoyl-l-threonine (C₁₂Thr) solutions at 30, 40, 50, and 60 °C and pH 8–9. CD spectra were not induced for AO and C₁AO in C₁₂Thr aqueous solutions. Induced circular dichroism (ICD) based on the exciton interaction was found for premicellar aggregates of C₁₂AO with C₁₂Thr, but the micellar aggregates failed to induce CD for solubilized C₁₂AO at a higher concentration than C₁₂Thr critical micelle concentration. The maximum ICD intensity was observed for 1:1.2 aggregates of C₁₂AO and C₁₂Thr. The ICD spectrum indicated positive chirality at 30 °C, but negative chirality at 50 °C. The chirality transition occurred at 40∼45 °C. The slow change in both the absorption and ICD spectra is ascribed partly to the rearrangement of dye alignment and partly to the growth of the aggregate; the system reaches final phase separation after a few days.     

原子吸收光谱仪七种元素吸收谱图的研究

原子吸收光谱分析法具有许多优越性，但其线性范围较窄。各元素的线性浓度范围，国内外仪器厂及有关专著均未给出，这给我们的分析工作带来诸多不利。为此，作者对7种元素的原子吸收谱图进行了分析研究，分别找出了7种元素在4种仪器工作条件下的浓度线性区。对减少样品前处理过程中的盲目性以及提高分析数据的准确性具有重要意义。     

Research on the prediction of absorption half-band width of some azobenzene compounds

In order to predict the absorption half-band width, the ground state and the first singlet-excited state configurations of some azobenzene compounds are calculated by B3LYP/6-311G* and CIS methods, respectively. Based on the configurations obtained above, the absorption maximum and emission maximum are calculated by TD-DFT method, the results are in good agreement with observed values. Further study shows a linear relationship between Δλ_1/2 (the observed absorption half-band width) and S (the difference between the emission maximum and absorption maximum). According to the relationship obtained, the absorption half-band width of other azobenzene derivatives in the same series could be predicted successfully.     

Luminescence properties of β-(Ga1−xInx)2O3 solid solutions

In this work, luminescence properties of β-(Ga_1−xIn_x)₂O₃ solid solutions were investigated with the purpose of making the new thermoluminophors for ultraviolet (UV) dosimetry. The doping of aliovalent cation admixture (Mg, Mo) in the β-Ga₂O₃ ceramic sample brings about the appearance of high-temperature thermoluminescence glow peaks with a maximum at 395 and 435 K. The maximum of the thermoluminophor photosensitivity shifts when the composition of solid solution changes.     

M_4S~(6 )(M=Cd,Zn)Clusters的电子结构和光谱性质的SCC-DV-X_α方法的计算研究

通过ＳＣＣ－ＤＶ－Ｘα方法对Ｍ４Ｓ６＋电子结构和光谱性质的计算研究得出Ｃｌｕｓｔｅｒｓ的第一吸收峰；同时，对Ｍ４Ｓ６＋的稳定性、电荷转移及轨道成分对ＬＵＭＯ和ＨＯＭＯ的影响进行了讨论。     

火焰原子吸收法测定钛合金中的硅

本文用火焰原子吸收光谱法测定钛合金中的硅。并研究了钛合金中基体元素钛和共存元素对硅含量测定的干扰情况，进行了校准曲线的试验。方法简单、快捷，具有良好的精密度和准确性。相对标准偏差为1．8％－3．7％，回收率为100％－102％。     

Optimisation of laser linewidth and cavity alignment in off-axis cavity-enhanced absorption spectroscopy

Laser linewidth affects baseline mode structured variations and hence measurement absorption sensitivity in off-axis cavity enhanced absorption spectroscopy with a continuous-wave tunable laser and a stable optical cavity formed by two high reflectivity mirrors. Cavity transmittances have been calculated for various laser linewidths and different optical beam re-entrant conditions for the cavity when overlapping of the optical beams occurs on the cavity mirrors after a finite number of beam round trips within the cavity. It is shown that in order to achieve maximum absorption sensitivity both a specific laser linewidth and specific arrangement of the optical cavity have to be selected and defined using the proposed approach.     

Water-mediated modulation of TiO2 decorated with graphene for photocatalytic degradation of trichloroethylene

The improvement of photocatalytic properties of TiO₂ was achieved by using water-mediated TiO₂ decorated with graphene (WTiO₂-d-graphene) composites. This work describes the photocatalytic degradation of trichloroethylene (TCE) in the presence of WTiO₂-d-graphene composites. WTiO₂-d-graphene composite photocatalysts, containing different amounts of graphene, were prepared by facile ultrasonic assisted techniques and thermal reaction. The surface properties of these WTiO₂-d-graphene composites were characterized by X-ray photoelectron spectroscopy (XPS). Peaks attributable to C–C (284.4 eV), denoted as the C_1s spectrum, and C–O bonds (288.6 eV) appeared simultaneously in the XPS spectrum. It was inferred that this was due to the presence of Ti–O–C bonds. The photocatalytic properties were determined by monitoring the degradation of TCE in the headspace of the vial at different times using gas chromatography. From the results, it was apparent that the photocatalytic activities of WTiO₂-d-graphene composites were higher than that of pure TiO_2. This can be attributed to their ability to absorb light over a wider range of wavelengths.     

离子液体[BMIM]Br与[BMIM][BF4]配比浓度对Br-离子电荷转移的调节

利用X射线吸收精细结构光谱(XAFS)及紫外吸收光谱两种方法, 分析了离子液体1-丁基-3-甲基咪唑溴盐([BMIM]Br)中逐渐掺入1-丁基-3-甲基咪唑四氟硼酸盐([BMIM][BF₄])时, Br^-阴离子与咪唑阳离子之间氢键作用及电荷偏移量的改变. 随着[BMIM][BF₄]加入量增多, Br 元素XAFS近边(XANES)显示吸收峰降低, 吸收边位置向低能端位移0.9 eV; 扩展边(EXAFS)算出径向结构显示Br 与近邻原子间平均配位数降低、平均键长增长; 紫外光谱也有明显蓝移减色效应. 这些结果都表明Br₄^-的掺入改变了Br^-与阳离子间的电荷偏移量, 负电荷更多地转移到Br^-上, 量化计算的数据同样支持该结论.     

Complex Formation of Hematoporphyrin with Cyclodextrins and 1,1′-Diheptyl-4,4′-bipyridinium Dibromide in Aqueous Solutions

At around 5×10^-6?mol?dm^-3 of hematoporphyrin (HP), an HP dimer exists as well as an HP monomer. The equilibrium constant for the dimerization of HP in pH 10.0 buffer has been evaluated to be 1.70×10⁵?mol^-1?dm³ from the HP concentration dependence of the absorption spectrum. In aqueous solution, HP forms 1:1 inclusion complexes with β-cyclodextrin (β-CD), γ-cyclodextrin (γ-CD), and heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (TM-β-CD). The fluorescence of HP is significantly enhanced by the addition of CDs. From simulations of the fluorescence intensity changes, the equilibrium constants for the formation of the CD–HP inclusion complexes have been estimated to be 200, 95.7, and 938?mol^-1?dm³ for β-CD, γ-CD, and TM-β-CD, respectively. HP forms a 1:1 complex with 1,1′-diheptyl-4,4′-bipyridinium dibromide (DHB) in aqueous solution. In contrast to the addition of CDs, the HP fluorescence is significantly quenched by the addition of DHB. The equilibrium constant for the formation of the HP–DHB complex has been evaluated to be 1.98×10⁵?mol^-1?dm³ from the fluorescence intensity change of HP. The addition of DHB to an HP solution containing β-CD induces a circular dichroism signal of negative sign, indicating the formation of a ternary inclusion complex involving β-CD, HP, and DHB. In contrast, there is no evidence for the formation of a ternary inclusion complex of HP with DHB and TM-β-CD.