Spectroscopic studies on 2,3,4,5-tetraphenylpyrylium salts with and without silver (I)-bridged structures

Two novel phenylated pyrylium compounds, silver (I)-bridged 2,3,4,5-tetraphenylpyrylium perchlorate (P1) and its silver (I)-free pyrylium ligand (P2) were prepared from 1,2,3,4-tetraphenylcyclopentadiene to examine their spectroscopic behaviors. The UV/vis absorption and fluorescent emission spectra of P1 and P2, measured in three solvents (acetonitrile, dichloromethane and toluene), reveal that the photophysical behaviors are closely related to silver (I) fragment, and strongly dependent on solvent polarity. In polar acetonitrile, P1 displays longer absorption wavelength and much lower fluorescent emission intensity than P2, although they exhibit much similarity in shape. In contrast, in nonpolar toluene, while P2 shows an apparent absorption band at 338 nm, P1 displays a tail-like line without absorption band observed. All the spectra obtained indicate a better coplanarity and a stronger intra-molecular charge transfer in P1 due to the effect of silver (I) fragment. Additionally, the 1H NMR spectra of P1 and P2, which were recorded under the same conditions, indicate that the silver (I) fragment reinforces pyrylium ring's capacity to localize the formal positive charge within the heterocyclic ring.     

Large-scale synthesis of tube-like ZnS and cable-like ZnS-ZnO arrays: Preparation through the sulfuration conversion from ZnO arrays via a simple chemical solution route

Arrayed structures are desirable for many applications, but the fabrication of many material arrays remains a significant challenge. As a prominent II-VI semiconductor, large-scale arrayed ZnS structure has not been easily fabricated. Here, we introduce a simple structure conversion route for the synthesis of novel arrayed structures, and large-scale tube-like ZnS structure arrays and cable-like ZnS-ZnO composite arrays were successfully prepared through sulfuration conversion from arrayed rod-like ZnO structure based on a hydrothermal method at low temperature. XRD, EDS, SEM, TEM and PL are used to confirm the formation of the novel arrayed structure and trace the conversion process. The results show that the conversion ratio can be conveniently tailored by the reaction time, and the PL properties of the obtained materials can be adjusted through the conversion ratio. Especially, the cable-like structure holds the PL properties of both ZnO and ZnS structures. This simple solution method can be further extended to the preparation of other semiconductor sulfide and selenide, and can amplify the application field of large-scale arrays of semiconductors.     

烯烃聚合均相催化剂研究进展

均相催化剂产生于５０年代末期，但由于活性很低而末引起重视。８０年代初，由于发现ＭＡＯ具有良好的助催化能力而使均相催化剂得到了很大发展，涌现了多种催化体系，广泛地使α－烯烃及其衍生物立体选择性聚合，开辟了配位聚合研究的新领域，本文对均相催化剂的产生，发展及现状作了综述评述。     

正交试验选择组织电极的最佳分析条件

本文用正交试验法对花椰菜组织Ｌ－抗坏血酸传感器和香蕉组织儿茶酚类化合物传感器的分析条件进行了优化，通过与单因子分析方法及４种儿茶酚类化合物之间正交试验结果的比较，说明用正交试验选择组织传感器的最佳分析条件，在少量的试验次数内，得到较多的分析实验信息，是一种较理想的试验方法。     

离线超临界流体萃取和气相色谱/质谱联用对实验室内空气中气相有机污染物的测试

通过团体吸附剂富集，再用超临界ＣＯ２脱附后用气相色谱及质谱技术对实验室内空气中气相有机污染物进行了考察。文中对采样和萃取条件进行了优化，并与热脱附所得结果做了比较。结果表明在２２ＭＰａ，８０℃时，用甲醇改性的超临界ＣＯ２进行萃取的结果优于热脱附法。该法鉴定出气相有机污染物中５２个组分，占色谱峰总面积的９９．６％。     

Flow injection analysis methods for determination of diffusion coefficients

Two flow injection analyses (FIA) methods for the determination of diffusion coefficients in a straight single tube FIA system were developed. Based on the analytical solution of the convection-diffusion equation, linear relationships of the logarithmic values of the dispersion coefficient (D) and the half-peak width (W_1/2) with the diffusion coefficient (D_m) were obtained. Experiments were designed to verify these methods. For example, for potassium hexacyanoferrate (III) a D_m value of 0.72 × 10⁵ cm² s⁻¹ was found versus a literature value of 0.76 × 10⁵ cm² s⁻¹ (error, 5%). For potassium hexacyanoferrate (II) a D_m value of 0.67 × 10⁵ cm² s⁻¹ was obtained versus a literature value of 0.63 × 10⁵ cm² s⁻¹ (error, 6%). The diffusion coefficients of some important biomedical compounds, such as dopamine, epinephrine, norepinephrine and ascorbic acid, were then determined. The values of 10⁵ D_m/cm² s⁻¹ are 0.60 ± 0.03, 0.44 ± 0.02, 0.60 ± 0.01 and 0.68 ± 0.06, respectively.     

稀土元素在LD30铝合金真空钎焊中的作用

研究了添加La和Ce的Al-Si基钎料真空钎焊LD30铝合金接头的力学性能，微观组织形貌和EDS，并与未添加稀土元素的Al-Si基钎料真空钎焊接头进行对比。结果表明，添加稀土元素的LD30铝合金真空钎焊接头抗拉强度为288MPa，达母材抗拉强度的97．6％，明显高于未添加稀土的LD30合金真空钎焊接头。其机制在于La,Ce能够明显提高Al-Si基钎料与LD30铝合金的润湿性能，改善LD30铝合金真空钎焊接头焊缝及其基体中杂质元素的分布，促进钎料和母材中各元素的均匀扩散，从而提高真空钎焊接头的力学性能。     

具有全氟丁基磺酰亚胺基侧链的聚磷腈的合成

本文合成了一种新的具有全氟丁基磺酰亚胺基侧链的聚磷腈高分子。并用¹H NMR、 ¹⁹F NMR、 IR光谱、凝胶渗透色谱以及热重分析等方法, 对其结构和性质进行了表征。     

Does core size matter in the kinetics of ligand exchanges of monolayer-protected Au clusters?

This paper compares the kinetics of exchanges of phenylethanethiolate ligands (PhC2S-) of the monolayer-protected clusters (MPCs) Au(38)(SC2Ph)(24) and Au(140)(SC2Ph)(53) with p-substituted arylthiols (p-X-PhSH), where X = NO(2), Br, CH(3), OCH(3), and OH. First-order rate constants at 293 K for exchange of the first ca. 25% of the ligands on the molecule-like Au(38)(SC2Ph)(24) MPC, measured using (1)H NMR, vary linearly with the in-coming arythiol concentration; ligand exchange is an overall second-order reaction. Remarkably, the second-order rate constants for ligand exchange on Au(38)(SC2Ph)(24) are very close to those of corresponding exchange reactions on the larger nanoparticle Au(140)(SC2Ph)(53) MPCs. These are the first results that quantitatively show that the chemical reactivity of different sized nanocrystals is almost independent of size; presumably, this is because the locus of the initial ligand exchanges is a common kind of site, thought to be the nanocrystal vertexes. The rates of later stages of exchange (beyond ca. 25%) differ for Au(38) and Au(140) cores, the latter being much slower presumably due to its larger terrace-like surface atom content. The reverse exchange reaction was studied for Au(38)(p-X-arylthiolate)(24) MPCs (X = NO(2), Br, and CH(3)), where the in-coming ligand is now phenylethanethiol. Remarkably, the rate constants of both forward and reverse exchanges display identical substituent effects, which implies a concurrent bonding of both in-coming and leaving ligands to the Au core in the rate-determining step, as in an associative mechanism. X = NO(2) gives the fastest rates, and the ratio of forward and reverse rate constants gives an equilibrium constant of K(EQ,PE) = 4.0 that is independent of X.