à 3E态CH3N自由基的稳定性

观察到了CH_3N自由基Ã ~3E←X~3A_2体系317-272 nm的荧光激发谱, 特别讨论了振动激发的Ã 态的稳定性. 报导了v_3~′=6态的色散荧光和荧光时间谱, 该态在240 Pa下的寿命大约是80 ns. 实验表明Ã ~3E 态CH_3N自由基是稳定的, 势能面至少距振动基态4800 cm~(-1)内是束缚的, 异构化或预离解作用并不重要.     

Formation and photoluminescence of silver nanoparticles stabilized by a two-armed polymer with a crown ether core

Silver nanoparticles were synthesized by the use of a two-armed polymer with a crown ether core [poly(styrene)]-dibenzo-18-crown-6-[poly(styrene)] based on the flexibility of the polymer chains and the complex effect of crown ether with Ag(+) and Ag. The size of silver nanoparticles could be tailored by controlling the initial concentrations of the polymer and Ag(+), and the molecular weight of the polymer. The emission of silver nanoparticles was blue-shifted, and the intensity of the photoluminescence of silver nanoparticles stabilized by the polymer was significantly increased due to the complex effect between the crown ether embedded in the polymer and the silver nanoparticles.     

Determination of trace amounts of iron by catalytic-adsorptive stripping voltammetry

A highly sensitive and selective voltammetric procedure is described for the determination of trace amounts of iron. The procedure is based on the adsorptive collection of an iron-thiocyanate-nitric oxide complex on a hanging mercury drop electrode. The adsorbed complex catalyzes the reduction of nitrite in solution, which gives a detection limit of 40 ppt iron (30 s accumulation). The stripping current increases linearly with iron concentration up to 80 ppb. The relative standard deviations are 4.2% and 1.6% at 0.5 ppb and 40 ppb respectively. Most of the common ions, except cobalt, do not interfere with the determination of iron. The procedure is applied to determine iron in biological samples, natural waters and analytical-grade chemicals.     

A Novel Plasticizer for the Preparation of Thermoplastic Starch

TPS was a biodegradable material based on starch. Starch was an inexpensive and natural renewable polysaccharide, which was widely investigated as the substitute of petroleum-derived plastics. Native starch commonly existed in granule structure with about…     

Voltammetric determination of trace amounts of gold(III) with a carbon paste electrode modified with chelating resin

A carbon paste electrode modified with chelating resin (ammino-isopropylmercaptan-type cross-linked chelating resins) for the voltammetric determination of gold(III) was characterized by cyclic voltammetry. The gold(III) ion is accumulated on the surface of the modified electrode only by the chelating effect of the modifier in the carbon paste, without application of a potential. After exchange of the medium the accumulated amount of gold(III) is determined by voltammetry in a blank electrolyte solution. The response depends on both the concentration of gold and the accumulation time. For a 5-min preconcentration time, a linear calibration graph was obtained in the range 3 × 10^?8-1 × 10^?6 M and the detection limit was about 1 × 10^?8 M. A combination of chemical and electrochemical renewal allows the use of a single modified electrode in multiple analytical determinations over several days. For ten preconcentration—determination—renewal cycles [2 × 10^?7 M Au(III)], the response could be reproduced with 4.7% relative standard deviation. Many parameters such as the composition of the paste and pH influence the response of the measurement. Many other metal ions have no or little effect on the determination of gold. The procedure was applied to the determination of gold in minerals, copper and anode mud, with good results.     

6291型热变形温度和维卡软化温度测试仪的校准及故障排除

介绍6291型热变形温度和维卡软化温度测试仪的温度校准和位移校准方法，对测试仪的一些常见故障，例如电源故障，主温度传感器故障，电加热系统控制单元故障及测试站的温度偏差较大等进行了分析，并给出了排除故障的方法。     

超高感彩卷乳剂微晶体电镜研究

应用物理和化学相结合的方法，将超高感彩卷分层剥离，离心沉降，水洗除胶，电镜观测各层乳剂的微晶体结构。揭示了超高感彩卷各乳剂层的结构情况，披露了超高感彩剂制造技术。     

L-谷氨酸、甘氨酸二元、三元体系中铽(Ⅲ)、钙(Ⅱ)的化学形态研究

在模拟生理条件下 (37℃ ,I=0 .1 5mol/ L Na Cl) ,用 p H电位法研究了铽 ( )、钙 ( )与 L-谷氨酸、甘氨酸二元、三元体系。确定了体系存在的物种 ,测定了体系中配合物的稳定常数。讨论了上述二元、三元体系中铽 ( )、钙 ( )的物种分布特点。     

Synthesis of diethers derived from furoin by phase transfer catalysis under microwave irradiation

A series of new diethers were obtained by alkylation of furoin under microwave irradiation (MWI) in phase transfer catalysis (PTC) conditions. The products of alkyl halides were synthesized in good yields (>75%) within a few minutes, and the products of dihalides were synthesized in fair yields (about 45%). The yields are dramatically improved compared to conventional heating under the same conditions, in spite of similar profiles of rising in temperature.     

Syntheses of (-)-TAN-2483A, (-)-massarilactone B, and the fusidilactone B ring system. Revision of the structures of and syntheses of (+/-)-Waol A (FD-211) and (+/-)-Waol B (FD-212)

The structure of waol A has been revised from 1 to 6, the vinylogue of TAN-2483A (5). Aldol reaction of hydroxybutanolides 13b,c with 2,4-hexadienal affords 12b,c, which are subjected to iodoetherification with bis(sym-collidine)IPF6 to provide 11b(c). Treatment with Et3N in CH2Cl2 completes the three-step syntheses of TAN-2483A (5) and waol A (6). Aldol reaction of hydroxybutanolide 31 with 2,4-hexadienal affords 32, which is subjected to iodoetherification to provide 34, which in turn is treated with Bu3SnCl, NaBH3CN, and oxygen to provide diol 60. Further elaboration completes the first syntheses of massarilactone B (7) and the fusidilactone B (9) ring system.