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41.
Bihlmeier A Gonsior M Raabe I Trapp N Krossing I 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(20):5041-5051
The unexpected but facile preparation of the silver salt of the least coordinating [(RO)3Al‐F‐Al(OR)3]? anion (R=C(CF3)3) by reaction of Ag[Al(OR)4] with one equivalent of PCl3 is described. The mechanism of the formation of Ag[(RO)3Al‐F‐Al(OR)3] is explained based on the available experimental data as well as on quantum chemical calculations with the inclusion of entropy and COSMO solvation enthalpies. The crystal structures of (RO)3Al←OC4H8, Cs+[(RO)2(Me)Al‐F‐Al(Me)(OR)2]?, Ag(CH2Cl2)3+[(RO)3Al‐F‐Al(OR)3]? and Ag(η2‐P4)2+[(RO)3Al‐F‐Al(OR)3]? are described. From the collected data it will be shown that the [(RO)3Al‐F‐Al(OR)3]? anion is the least coordinating anion currently known. With respect to the fluoride ion affinity of two parent Lewis acids Al(OR)3 of 685 kJ mol?1, the ligand affinity (441 kJ mol?1), the proton and copper decomposition reactions (?983 and ?297 kJ mol?1) as well as HOMO level and HOMO–LUMO gap and in comparison with [Sb4F21]?, [Sb(OTeF5)6]?, [Al(OR)4]? as well as [B(RF)4]? (RF=CF3 or C6F5) the [(RO)3Al‐F‐Al(OR)3]? anion is among the best weakly coordinating anions (WCAs) according to each value. In contrast to most of the other cited anions, the [(RO)3Al‐F‐Al(OR)3] anion is available by a simple preparation in conventional inorganic laboratories. The least coordinating character of this anion was employed to clarify the question of the ground state geometry of the Ag(η2‐P4)2+ cation (D2h, D2 or D2d?). In agreement with computational data and NMR spectra it could be shown that the rotation along the Ag‐(P‐P‐centroid) vector has no barrier and that the structure adopted in the solid state depends on packing effects which lead to an almost D2h symmetric Ag(η2‐P4)2+ cation (0 to 10.6° torsion) for the more symmetrical [Al(OR)4]? anion, but to a D2 symmetric Ag(η2‐P4)2+ cation with a 44° twist angle of the two AgP2 planes for the less symmetrical [(RO)3Al‐F‐Al(OR)3]? anion. This implies that silver back bonding, suggested by quantum chemical population analyses to be of importance, is only weak. 相似文献
42.
本文用反相微乳液法制备了纳米Ag2S,并用作卤化银乳剂的硫增感剂,研究了其增感效果、增感规律及可能的增感机理.反相微乳液由异辛烷、表面活性剂AOT钠盐和水形成;制得的Ag2S粒径3—5 nm;用制得颗粒增感卤化银乳剂,获得的感光性能优越于用Na2S2O3水溶液增感;增感规律的研究表明,随着乳剂中纳米Ag2S浓度的增加,模型乳剂感光度迅速提高、灰雾变化不大,并在100—200μmol/molAg左右获得最佳感光性能,进一步增加浓度则感光度呈下降趋势、灰雾升高;获得最佳感光性能所需的化学增感时间很短,约40分钟,之后感光度不再增加、灰雾上升;用漫反射光谱(DRS)作探针,跟踪记录增感时卤化银微晶表面上纳米Ag2S增感剂颗粒的演变,为新型纳米增感剂的优异增感特性提供了机理性解释. 相似文献
43.
量子点传感器测定水中微量银离子 总被引:4,自引:0,他引:4
来守军 《广东微量元素科学》2008,15(6)
选择铋试剂Ⅱ作为硫化镉(cds)量子点的修饰剂,合成了表面修饰的量子点,利用其有效官能团与银离子作用,导致修饰的量子点的荧光增强作用,建立了测定银离子的方法,开发了新型的银离子的传感器。结果表明,对水中银离子测定的线性范围为0.01~5.0μmol.L-1,相关系数为0.999 3,检测限达到1.6 nmol.L-1,对实际水样的分析获得了较满意的结果。 相似文献
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48.
Minghua Min Yuyuan Shi Haiyou Ma Hongliang Huang Jiangao Shi Xiaoxue Chen 《Journal of Macromolecular Science: Physics》2015,54(4):411-423
The effects of addition of synthesized organic-suspension silver nanoparticles on the crystallization and thermal stability of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) were studied by transmission electron microscopy (TEM), differential scanning calorimetry (DSC), wide-angle X-ray diffraction (XRD), UV-Vis absorption spectroscopy, polarized optical microscopy (POM), and thermal gravimetric analysis (TGA). The TEM images showed the average primary size of the as-synthesized silver nanoparticles, coated with a monolayer of the surfactants consisting of oleic acid and an alkylamine, was about 5 nm with narrow distribution, and that they were uniformly dispersed in n-heptane. PHBV/silver nanocomposites were prepared by melt mixing in an internal mixer and then injection molded into rectangle-shaped specimens by a labscale injection molding device. The coated silver nanoparticles showed a homogenuous dispersion in the PHBV matrix when the content of coated silver nanoparticles was about 1%. Both the DSC and POM data showed the efficient heterogeneous nucleation by the coated silver nanoparticles for facilitating PHBV crystallization. The thermal stability of the PHBV/silver nanocomposites improved with the increase in the content of the coated silver nanoparticles. 相似文献
49.
Silver nanoparticles have been prepared in a polyacrylamide (PA) matrix, as well as in the presence of a hyperbranched polyamine/polyacrylamide combined system (HB‐PA) by using a reductive technique. The stability of colloidal solution of silver nanoparticles is higher (5 months) in combined matrix compared to PA alone (4 months). The prepared silver nanoparticles were characterized by different spectroscopic and analytical techniques such as FTIR, UV‐visible, X‐ray diffraction, TEM etc. TEM and XRD studies confirmed the formation of well‐dispersed nanoparticles with an average size of 9.91 nm and 8.5 nm for PA and HB‐PA matrices, respectively. The antibacterial activity of silver nanoparticles in both the matrices was tested against Bacillus Subtilis bacteria by using the diffusion disc technique. The result shows that the antibacterial activity of the active agent, Ag(0) is a little higher in the case of HB‐PA system. The dielectric constant of the matrices decreases with an increase in frequency, but the values increase with an increase of concentration of silver nanoparticles in PA matrix. 相似文献
50.
This paper describes a simple method for the synthesis of water-soluble, silver nanoparticle-encapsulated β-cyclodextrin by phase transfer of silver nanoparticles from organic to aqueous phase using β-cyclodextrin as a capping agent. β-Cyclodextrin–silver nanoparticle inclusion complex was purified, characterised by spectroscopic and microscopic analyses and tested in vitro against Pseudomonas aeruginosa, Staphylococcus aureus, Serratia marcescens, Escherichia coli and Klebsiella pneumoniae. The silver nanoparticle-encapsulated β-cyclodextrin inclusion complex displayed considerable antimicrobial activity and stability. 相似文献