离子选择电极法测定熏蒸剂硫酰氟残留量

利用稀硫酸溶液于 60℃提取粮食中残留熏蒸剂硫酰氟 ,经氮气吹扫 ,用 5mol·L- 1氢氧化钠溶液吸收 ,使其转化为氟离子 ,用氟离子选择电极测定氟离子浓度 ,从而推算出硫酰氟的含量。该法对玉米、大米、豌豆的检出限分别为 0 .5 ,0 .8和 0 .5mg·kg- 1。方法适于粮食中硫酰氟残留量的检测     

稀土氟化物上转换荧光增强及应用

稀土氟化物上转换纳米材料具有化学稳定性高、反斯托克位移大、无光漂白、荧光寿命长、发光谱带窄和穿透深度深等优点,在荧光成像和光热疗、传感器、太阳能电池及防伪技术等领域具有广泛的应用前景,是一种极具发展潜力的荧光材料。然而该类材料在实际应用时还存在有荧光效率低、吸收截面小等亟待解决的瓶颈问题。针对以上问题,本文系统阐述了离子共掺杂、核壳结构、表面等离子耦合、光子晶体、宽频敏化和热效应等增强稀土氟化物上转换荧光的方法及其近年的研究进展。并在此基础上,总结了近年来荧光增强稀土氟化物上转换纳米材料在生物成像和光热疗、生物传感、太阳能电池及防伪技术等领域的应用研究现状。最后,分析了稀土氟化物UCNPs目前仍存在的不足,并对将来的发展方向进行了展望。     

Ferroelectric properties of nylon 11 and poly(vinylidene fluoride) blends

Both poly(vinylidene fluoride) (PVF₂) and nylon 11 are ferroelectric polymers, and have been extensively studied over the past two decades. Blend films were made from mixed powders of these two polymers, which were then melt pressed and cold drawn. The ferroelectric properties of these blend films were investigated. The remnant polarization, P_r, was found to vary with composition, and to be 60% larger than that of either component at a 50/50 (by weight) composition where P_r exhibited a maximum of about 90 mC/m². The magnitude of the coercive field, E_c, also exhibited a maximum at this composition. Both P_r and E_c are also observed to change significantly with the draw ratio. The results are discussed based on a two-phase dielectric composite model. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 3217–3225, 1999     

Flow injection analysis as a tool for enhancing oceanographic nutrient measurements—A review

Macronutrient elements (C, N and P) and micronutrient elements (Fe, Co, Cu, Zn and Mn) are widely measured in their various physico-chemical forms in open ocean, shelf sea, coastal and estuarine waters. These measurements help to elucidate the biogeochemical cycling of these elements in marine waters and highlight the ecological and socio-economic importance of the oceans. Due to the dynamic nature of marine waters in terms of chemical, biological and physical processes, it is advantageous to make these measurements in situ and in this regard flow injection analysis (FIA) provides a suitable shipboard platform. This review, therefore, discusses the role of FIA in the determination of macro- and micro-nutrient elements, with an emphasis on manifold design and detection strategies for the reliable shipboard determination of specific nutrient species. The application of various FIA manifolds to oceanographic nutrient determinations is discussed, with an emphasis on sensitivity, selectivity, high throughput analysis and suitability for underway analysis and depth profiles. Strategies for enhancing sensitivity and minimizing matrix effects, e.g. refractive index (schlieren) effects and the important role of uncertainty budgets in underpinning method validation and data quality are discussed in some detail.     

几种无定型聚芳醚砜(酮)的成环解聚及产物的开环聚合

几种线性高分子量的无定型聚芳醚砜(酮)在非质子极性溶剂二甲基乙酰胺(DMAc)和二甲基甲酰胺(DMF)中,以氟化铯(CsF)为催化剂进行解聚成环,所得环状低聚物由凝胶渗透色谱(GPC)、高效液相色谱(HPLC)和激光质谱(MALDI-TOF-MS)确认,其中酚酞聚醚砜(PES-C)和酚酞聚醚酮(PEK-C)的解聚成环率分别高达86．3％和87．9％．讨论了影响成环率的各种因素．环状产物又在阴离子引发剂联苯双酚钾的作用下进行开环聚合重新得到高分子量的线性产物．     

18F‐Labeling of Aryl‐SCF3, ‐OCF3 and ‐OCHF2 with [18F]Fluoride

We report that halogenophilic silver(I) triflate permits halogen exchange (halex) nucleophilic ¹⁸F‐fluorination of aryl‐OCHFCl, ‐OCF₂Br and ‐SCF₂Br precursors under mild conditions. This Ag^I‐mediated process allows for the first time access to a range of ¹⁸F‐labeled aryl‐OCHF₂, ‐OCF₃ and ‐SCF₃ derivatives, inclusive of [¹⁸F]riluzole. The ¹⁸F‐labeling of these medicinally important motifs expands the radiochemical space available for PET applications.     

改性聚偏氟乙烯接枝磺化聚(苯乙烯-co-丙烯酸)膜的研制

以过氧化苯甲酰(BPO)作引发剂,通过溶液接枝聚合法把苯乙烯/丙烯酸同时接枝到原硅酸钠改性的聚偏氟乙烯(PVDF)膜上,磺化后得到聚偏氟乙烯接枝磺化聚(苯乙烯-co-丙烯酸)膜(PVDF-g-P(SSA-co-AA)).研究了苯乙烯和丙烯酸的不同比例对膜的接枝反应及其相对湿度对膜电导率和含水量的影响.用傅立叶变换红外光谱(FTIR)检测原硅酸钠改性的PVDF膜经过接枝和磺化后所发生的结构变化,并用扫描电镜(SEM)观察PVDF膜接枝前后的形貌以及接枝磺化后产物PVDF-g-P(SSA-co-AA)膜的形貌及硫和硅分布.结果表明,原硅酸钠改性的PVDF膜与苯乙烯/丙烯酸同时发生接枝聚合反应,环境的相对湿度在20%～80%范围,对添加10wt%Na4SiO4的PVDF-g-P(SSA-co-AA)膜的电导率的影响基本不变,并达到0.0198S·cm-1.原硅酸钠改性的PVDF膜结构在接枝前后和磺化前后发生变化,确认磺化反应不只是在膜表面,同时渗入膜中进行.     

Anhydrous oxygen-free rare earth material preparation and characterization

The present paper addresses the preparation and characterization of anhydrous oxygen-free rare earth materials, such as terbium fluoride (TbF₃). The fluorination of terbium oxide (Tb₄O₇) by ammonium bifluoride (NH₄HF₂) to prepare anhydrous TbF₃ was reported in this work. The parameters affecting fluorination were studied, including the fluorination temperature, excess stoichiometric amount of NH₄HF₂, and time for fluorination. The temperatures of Tb₄O₇ fluorination by NH₄HF₂ determined by thermogravimetric analysis and differential thermal analysis ranged from 350°C to 500°C. The phase structure of the as-prepared products identified by the X-ray diffraction method was indexed to the orthorhombic phase of TbF₃ [space group: Pnma (no. 62)] that exhibited good accordance with the values in the standard cards JCPDS No. 37-1487 for TbF₃. Energy-dispersive X-ray spectroscopy (EDS) methods were used to analyze the elemental compositions in the as-prepared products; the fluorine (F) and terbium (Tb) elemental compositions calculated from the [TbF₃] formula are in good agreement with those calculated from the EDS pattern. The optimum parameters for fluorination were determined from the results, and anhydrous oxygen-free TbF₃ can be used to study the preparation of metallic terbium by the calcinothermic reduction method.     

Poly（vinylidene fluoride）/Clay Nanocomposites by Melt Compounding

The crystalline structures, morphologies, and mechanical properties of poly（vinylidene fluoride）/clay nanocomposites were studied using X-ray diffraction（XRD）, transmission electron microscopy（TEM）, Fourier transform infrared spectroscopy（FTIR）, polarized optical microscopy（POM）, and tensile tests. The results of XRD and TEM show that organoclays are dispersed in the poly（vinylidene fluoride）（PVDF） matrix. A clay-induced crystal transformation from α-phase to β-phase of PVFD was confirmed by XRD and FTIR. Clay layers restricted the growth of spherulite. The tensile tests indicate that the tensile modulus and yield strength as well as the elongation at break decrease when clay is loaded.     

Preparation and magnetic properties of TbF3 containing oxide fluoride glasses

New glasses containing TbF₃ have been prepared in a TbF₃-BaF₂-AlF₃-GeO₂ system. Their respective densities, refractive indexes, and glass transition temperatures are (5.42-6.07) × 10³ kg m⁻³, 1.72-1.73, and 605.1-675.2 °C. Their magnetic susceptibilities are proportional to the contents of TbF₃ in glasses obtained in this study. The values agree with the calculated values. The Curie constant of the 40TbF₃-20BaF₂-10AlF₃-20GeO₂ glass is 5.13 K emu mol⁻¹; its effective magnetic susceptibility is 9.96μ_B. The atomic percentage of Tb³⁺ in the 40TbF₃-20BaF₂-10AlF₃-20GeO₂ glass is 11%, which is comparable to that of the oxide glass, which is reported as the material for Faraday components.