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101.
Three ion-pair complexes, [RbzPy](+)[Ni(mnt)(2)](-) (mnt(2)(-) = maleonitriledithiolate; [RbzPy](+) = 4-R-benzylpyridinium; R = Br (1), Cl (2), and NO(2) (3)), with unusual magnetic properties have been synthesized and characterized. The crystal structures of 1 and 2 have been solved. The two complexes belong to the P2(1)/c space group with Z = 4 and C(20)H(11)BrN(5)NiS(4), a = 12.0744(17) A, b = 26.369(4) A, c = 7.440(3) A, and beta = 102.63(3) degrees for 1 and C(20)H(11)ClN(5)NiS(4), a = 12.105(2) A, b = 26.218(4) A, c = 7.374(2) A, and beta = 102.55(2) degrees for 2, respectively. The [Ni(mnt)(2)](-) anions in 1-3 form uniformly spaced one-dimensional (1-D) magnetic chains of s = 1/2 at room temperature. The temperature dependences of the susceptibility for 1-3 show that they undergo phase transitions. All three complexes are paramagnetic in their high-temperature (abbreviation HT) phase and diamagnetic in the low-temperature (abbreviation LT) phase because of strong dimerization along the stacking direction. The results of thermal analysis (DSC) further confirm that the phase transition for 1 and 2 is first-order but maybe second-order for 3. The phenomena observed in this study are similar to those of the 1-D radical systems. 相似文献
102.
A new highly sensitive and selective chromogenic reagent dibromo-p-methyl-carboxysulfonazo (DBMCSA) was synthesized and studied for the spectrophotometric determination of lead in detail. In 0.25 M phosphoric acid medium, which greatly increases the selectivity, lead reacts with DBMCSA to form a 1:2 blue complex, having a sensitive absorption peak at 648 nm. Under the optimal conditions, Beer's law is obeyed over the range from 0 to 0.8 μg ml−1 Pb(II) and the apparent molar absorptivity is 1.04×105 l mol−1 cm−1. The detection limit and the variation coefficient were found to be 2.14 ng ml−1 and 1.0%, respectively. It is found that, except for Ca(II) and Ba(II), all foreign ions studied do not interfere with determination. The interference caused by Ca(II) and Ba(II) can be easily eliminated by prior extraction with potassium iodide-methylisobutylketone. The method has been applied to the determination of lead in vegetables with satisfactory results. 相似文献
103.
104.
BaCe1—xRExO3—0.5x的溶胶—凝胶法合成及离子导电性 总被引:3,自引:0,他引:3
用溶胶-凝胶法合成了系列钙钛矿结构的BaCe1-xRExO3-0.5x(RE=La,Nd,Sm,Eu,Gd,Dy,Ho,Er和Y)复合氧化物,通过XRD和热分析对样品结构及生成过程进行了研究.测定了不同温度下样品的交流阻抗谱,讨论了稀土离子掺杂对BaCeO3电性质的影响.溶胶-凝胶法比固相反应法合成温度降低了600~800℃,稀土掺杂使BaCeO3离子导电率提高了10~40倍. 相似文献
105.
Yanli Zeng Lingpeng Meng Shijun Zheng Maofa Ge Dianxun Wang 《Chemical physics letters》2004,400(4-6):394-400
A cluster DFT (B3LYP) calculation study of ClN3 and BrN3 dissociation pathways catalyzed by molecular sieve is reported. A three-tetrahedral molecular sieve cluster (Al(OHSiH3)(OSiH3)(OH)2, called T3) has been chosen in this study. Triplet-state products ClN and BrN are more easily produced with T3 molecular sieve cluster. Although the potential energy surfaces with T3 molecular sieve cluster are similar with those without T3 molecular sieve cluster, the dissociation process of ClN3 and BrN3 with T3 molecular sieve cluster becomes easier, which can be attributed to smaller energy gaps from the ground state reactant to the intersystem crossing point. 相似文献
106.
表面增强拉曼光谱(SERS)技术是一种基于贵金属纳米结构基底对被检测物进行高灵敏度检测的一种方法.具有特殊纳米结构的贵金属表面受到激光的照射时,金属表面的自由电子会受到极大的振荡,当入射光频率与振荡频率相近时,则会发生表面等离子体共振现象(SPR),使金属表面的局域电场强度极大增强,入射光强度和散射光强度都得到成倍的放大,从而使吸附在贵金属纳米结构表面的分子的拉曼散射信号得到有效的增强.使用NaBH4还原-酸刻蚀模板法,制备了八面体Au/Ag复合纳米笼,其形貌规整,尺寸均匀约为600 nm,无Cu2O模板的残留,Au元素均匀负载在Ag纳米笼上,质量分数约为16.8%;Au/Ag复合纳米笼的紫外可见吸收峰相对于Ag纳米笼发生了红移,更重要的是,Au和Ag元素协同赋予了复合纳米笼超高的SERS灵敏度和重复性,Au/Ag复合纳米笼实现了对罗丹明6G的痕量检测(5×10-14 mol/L),通过时域有限差分法(FDTD)模拟证实:这主要归因于等离子共振作用产生的高电磁场强度;此外,Au元素的加入使Au/Ag复合纳米笼具有优异的抗氧化性和化学稳定性,即使在1%的H2O2溶液中浸泡3 h,仍然能够保持优异的SERS性能.八面体Au/Ag复合纳米笼有望成为一种具有应用前景的高灵敏度、高稳定性的SERS基底. 相似文献
107.
Meng Wang Weiyue Feng Junwen Shi Fang Zhang Bing Wang Motao Zhu BaiLi Yuliang Zhao Zhifang Chai 《Talanta》2007,71(5):2034-2039
A mild, efficient and convenient extraction method of using 2-mercaptoethanol contained extractant solution combined with an incubator shaker for determination of mercury species in biological samples by HPLC–ICP-MS has been developed. The effects of the concentration of 2-mercaptoethanol, the composition of the extractant solution and the shaking time on the efficiency of mercury extraction were evaluated. The optimization experiments indicated that the quantitative extraction of mercury species from biological samples could be achieved by using 0.1% (v/v) HCl, 0.1% (v/v) 2-mercapoethanol and 0.15% (m/v) KCl extractant solution in an incubator shaker for shaking overnight (about 12 h) at room temperature. The established method was validated by analysis of various biological certified reference materials, including NRCC DOLT-3 (dogfish liver), IAEA 436 (tuna fish), IAEA MA-B-3/TM (garfish filet), IAEA MA-M-2/TM (mussel tissue), GBW 08193 (bovine liver) and GBW 08572 (prawn). The analytical results of the reference materials were in good agreement with the certified or reference values of both methyl and total mercury, indicating that no distinguishable transformation between mercury species had occurred during the extraction and determination procedures. The limit of detection (LOD) for methyl (CH3Hg+) and inorganic mercury (Hg2+) by the method are both as 0.2 μg L−1. The relative standard deviation (R.S.D.s) for CH3Hg+ and Hg2+ are 3.0% and 5.8%, respectively. The advantages of the developed extraction method are that (1) it is easy to operate in HPLC–ICP-MS for mercury species determination since the extracted solution can be directly injected into the HPLC column without pH adjustment and (2) the memory effect of mercury in the ICP-MS measurement system can be reduced. 相似文献
108.
109.
Sesquiterpene esters from the fruits of Celastrus orbiculatus 总被引:1,自引:0,他引:1
Three new beta-dihydroagarofuran sesquiterpene esters, 6 alpha-acetoxy-9 beta-benzoyloxy-1 beta-cinnamoyloxy-8 beta-butanoyloxy-beta-dihydroagarofuran (1), 6 alpha-acetoxy-9 beta-benzoyloxy-1 beta-cinnamoyloxy-8 beta-(2-methylbutanoyloxy)-beta-dihydroagarofuran (2), and 6 alpha-acetoxy-1 beta,8 beta-dibenzoyloxy-9 beta-hydroxy-beta-dihydroagarofuran (6), together with three known compounds (3-5) were isolated from the fruits of Celastrus orbiculatus THUNB. Their structures were elucidated on the basis of spectroscopic methods. Compound 4 showed moderate activity in inhibiting LPS-induced nitric oxide production in murine macrophage RAW264.7 cells with an IC(50) value of 43.7 microM. 相似文献
110.
菲林B近红外分光光度法测定维生素C 总被引:2,自引:0,他引:2
在pH 3的三氯乙酸酸性介质中,菲林B可以定量地将还原型维生素C氧化成脱氢型维生素C,利用脱氢型维生素C在920 nm处有最大吸光度,测定其含量,建立了一种测定维生素C的新方法,并研究了影响反应的各种因素。该方法对维生素C的检出限为0.17 mg/L;线性范围为0.5~10 mg/L,对水果中维生素C含量测定的RSD<2.31%;回收率为99.7%~101.1%,比2,4-二硝基苯肼分光光度法测定结果的相对偏差<±1.6%。 相似文献