Preparation of the individual compact single-chain globular particulates of Poly(N-isopropylacrylamide)

The compact single-chain (SC) particulates of Poly(N-isopropylacrylamide) (PNIPAM), which have been formed above its lower critical solution temperature in an aqueous solution containing the surfactant of sodium n-dodecyl sulfate (SDS), were recovered from the solution by freeze-drying. Under scanning electron microscopy, the compact particulate appears as a spherical or elliptical particulate individually dispersed in SDS, which acts as a solid solvent to prevent agglomeration. The conformation of the compact SC particulates of PNIPAM dispersed in SDS had been studied by the solid-state high-resolution ¹³C NMR spectroscopy. The ¹³C spin-lattice relaxation time T ₁ of the SC sample was determined in comparison with that of the original one. It was found that the T ₁ of the methyl carbon in the isopropyl group of the SC sample was about 45% higher than that in the original multichain sample, which revealed the differences in the motion of the methyl group in the different condensed states and illuminated the characteristic conformation of the compact SC globular particulates of PNIPAM.     

双波长K系数—标准加入吸光光度法同时测定锰和锌

研究应用双波长K系数—标准加入吸光光度法同时测定锰和锌二组分混合物.试验确定了锰和锌测定中K_(Mn)与K_(Zn)的回归方程.对合成试样、人发试样测定,结果满意.     

钆铁磁－顺磁相变的正电子寿命研究

通过测量金属钆在居里点附近的正电子湮没寿命谱随温度变化的关系，发现钆的正电子湮没寿命在居里点近邻Ｔ＜ＴＣ一侧随温度有显著变化，而在此温区以外几乎不随温度变化     

汞的形态分析研究 Ⅱ.固相萃取预富集-液相色谱分离测定不同形态的有机汞

本文报道了固相萃取预富集处理样品继以液相色谱分离测定不同形态痕量有机汞的方法.二乙基二硫代氨基甲酸钠(DDTC)作络合剂及甲醇作洗脱液的预富集系统能在线富集甲基汞(MeHg)、乙基汞(EtHg)和苯基汞(PhHg).用于测定加标海水中MeHg、EtHg和PhHg,回收率分别为96.9％、102.4％和98.0％;相对标准偏差分别为3.5％、5.0％和5.0％;检测下限分别为 1.0μg/L、1.2 μg/L和 1.2 μg/L.     

活性碳分离碳－60和碳－70

活性碳用苯胺处理后，可以减少对Ｃ＿（６０）和Ｃ＿（７０）的不可逆吸附，从而增加Ｃ＿（６０）和Ｃ＿（７０）的分离收率，同时提高了Ｃ＿（７０）的纯度。     

Polymer bound glutamic acid salicylaldehyde Schiff‐base complex ­catalyst for oxidation of olefins with ­dioxygen

The polymer bound Schiff‐base ligand (PS‐SalGlu) has been prepared from polystyrene bound salicylaldehyde and glutamic acid, and its complex (PS‐SalGlu‐Co) has also been synthesized. The polymer ligand and its complex were characterized by infrared spectroscopy, small area X‐ray photoelectron spectroscopy, and inductively coupled plasma‐atomic emission spectro (ICP‐AFS). In the presence of the complex, cyclohexene can be effectively oxidized by molecular oxygen without reductant. The long‐chain linear aliphatic olefins, such as 1‐octene, 1‐decene, 1‐dodecene and 1‐tetradecene, can be directly oxidized by molecular oxygen catalyzed by PS‐SalGlu‐Co, which affords the 1,2‐epoxy alkane. Copyright © 2001 John Wiley & Sons, Ltd.     

2,4-二氧代-1,3,2-苯并二氮磷杂环己烷与■C=C■及CS_2加成反应的研究

本文研究了2,4-二氧代-1,3,2-苯并二氮磷杂环己烷的磷氢键对β-硝基苯乙烯、丙烯酸酯、丙烯腈及二硫化碳的加成反应,共合成了18个新的加成产物.发现通过选用不同的碱或控制碱的用量.可选择性的进行加成或开环反应.由X衍射证实:在加成产物的结构中,环外P-C键构象因受磷杂环船式构象影响,以邻位交叉式(A)为主.     

A novel approach to carbon hollow spheres and vessels from CCl4 at low temperatures

Carbon hollow spheres (400-600 nm) and vessels (400 nm x 3000 nm) have been synthesized from sp3-CCl4 at 190 and 230 degrees C, respectively. The HRTEM images and Raman spectra reveal the sp2 nature of the as-obtained products, indicating that the transformation from carbon sp3 to sp2 occurs in the reactions. The possible mechanism has also been proposed.     

Efficient and mild benzoin condensation reaction catalyzed by simple 1-N-alkyl-3-methylimidazolium salts

The benzoin reaction, catalyzed by simple 1-N-alkyl-3-methylimidazolium salt-based ionic liquid via carbene intermediate, to give the α-hydroxyl ketone proceeds in CH₂Cl₂ under mild conditions.     

Ab initio Valence Bond Study on AB-type Molecules,A Description for XH(X=L,Be,B,C,N,O,F) and XF(X=Li,Be,B)

Ab initio valence bond method is employed to quantitatively study the concepts of ionic resonance energy and ionicity of a chemical bond in the cases of hydrides XH(X=Li,Be,B,C,N,O,F) and fluorides XF(X=Li,Be,B),By establishing the relationship between resonance and stability,and comparing the calculated ionicities with Pauling‘s earlier estimations in the above diatomic molecules,the merits of Pauling‘s classical resonance theory were demonstrated at the ab initio level.