Effects of potassium on the reaction pathway of C3H7 species over Mo2C/Mo (1 0 0)

The adsorption and surface reactions of propyl iodide on clean and potassium-modified Mo₂C/Mo(1 0 0) surfaces have been investigated by thermal desorption spectroscopy (TPD), X-ray photoelectron spectroscopy (XPS) and high resolution electron energy loss spectroscopy (HREELS) in the 100-1200 K temperature range. This work is strongly related to the better understanding of the catalytic effect of Mo₂C in the conversion of hydrocarbons. Potassium was found to be an effective promoter: it induced the rupture of C-I bond in the adsorbed C₃H₇I even at 100 K. The extent of C-I bond scission varied approximately linearly with the concentration of K coverage at the adsorption temperature of 100 K. As revealed by HREELS and TPD measurements the primary products of the dissociation are C₃H₇ and I. The former one was stabilized by potassium and underwent dehydrogenation and hydrogenation to give propene and propane. The desorption of both compounds is reaction-limited process. A fraction of propyl groups was converted into di-σ-bonded propene, which was stable up to ∼380 K. The coupling reaction of propyl species was also facilitated by potassium and resulted in the formation of hexane and hexene with T_p ∼ 230-250 K. Hydrogen was released with T_p = 390 K, indicative of a desorption limited process. The effect of potassium was explained by the extended electron donation to adsorbed propyl iodide in one hand, and by the direct interaction between potassium and I on the other hand. This was reflected by the shift of the desorption of potassium from the coadsorbed layer at and above 1.0 ML to higher temperature, and by the coincidal T_p values (∼700 K) of potassium and iodine. The formation of KI was also supported by the appearance of a loss feature at 650 cm⁻¹ in the HREEL spectra attributed to a phonon mode of KI.     

Synthesis and Self‐Assembly of Novel s‐Tetrazine‐Based Gelator

The design, synthesis and self‐assembly of new symmetrical 3,6‐bis(4‐(3,4,5‐tris(dodecyloxy)benzoate)phenyl)‐1,2,4,5‐tetrazine were described. The novel gelator, sym‐tetrazine, was prepared by addition reaction of 4‐cyanophenol with hydrazine monohydrate followed by oxidation reaction to afford the corresponding 3,6‐bis(4‐hydroxyphenyl)‐1,2,4,5‐tetrazine which was then subjected to esterification reaction with 3,4,5‐tris(dodecyloxy)benzoic acid. The chemical structure of the sym‐tetrazine gelator was confirmed by elemental analysis, fourier‐transform infrared spectroscopy (FT‐IR), and nuclear magnetic resonance (¹H‐ and ¹³C‐NMR) spectral measurements. It was confirmed to exhibit relatively strong gelation ability to produce supramolecular assemblies in several polar alcoholic organic solvents, such as butanol, octanol, and 1,6‐dihydroxyhexane. The π‐π stacking and van der Waals mediated self‐assembly of tetrazine‐based organogelator were studied by scanning electron microscopy images of the xerogel to reveal that the obtained organogel consists of fibrillar aggregates. Investigation of FT‐IR and concentration‐dependent ¹H‐NMR spectra confirm that the intermolecular van der Waals interactions and π‐π stacking were the key driving forces for self‐assembly during gelation process of s‐tetrazine molecules.     

Chromatographic Retention of Epigallocatechin Gallate on Oligo-β-Cyclodextrin Coupled Sepharose Media Investigated Using NMR

The retention of epigallocatechin gallate (EGCG) on oligo-β-cyclodextrin (oligo-β-CD) bonded agarose chromatographic media was investigated. NMR spectroscopy in solution showed that the EGCG immerses into the β-CD cavity. The association constant calculated by NMR titration was used to estimate a retention factor which accurately reflected chromatographic behaviour. This correlation suggests that oligo-β-CD forms inclusion complexes with EGCG via the same mechanism as monomeric β-CD. Revised: 14 March and 25 April 2006     

St/BA/KH-570三元共聚物的合成及其在云母增强聚丙烯中的应用

通过原子转移自由基聚合反应，合成了苯乙烯，丙烯酸丁酯和3－甲基丙烯酰氧基丙基三甲氧基硅烷的三元共聚物，发现该共聚合体系是一“活性”／受控聚合体系，三元共聚物的结构通过红外光变和核磁共振得以确认。研究了该三元共聚物作为大分子偶联剂对云母增强聚丙烯力学性能的影响。发现三元共聚物的组成和分子量对云母增强聚丙烯的力学性能有较大影响。     

Polymeric nanoparticles prepared using salt bridges between [(dimethylamino)propyl]-octadecanamide and poly(N-isopropylacrylamide-co-methacrylic acid)

Polymeric lipid nanoparticles were prepared in 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid buffer (pH 8.0, 10 mM) by taking advantage of salt bridges formed between poly(N-isopropylacrylamide-co-methacrylic acid) (P(NIPAM-co-MAA)) and N-[3-(dimethylamino)propyl]-octadecanamide (DMAPODA). The homogeneous nanoparticles of 200–250 nm were obtained when the copolymer was included in the preparation so that the relative mass of copolymer to lipid was more than 5. However, when the relative amount of copolymer was less than 5, large agglomerates more than 10 μm were observed together with nanoparticles. The protonated amino groups of DMAPODA will attach to the ionized carboxyl groups of P(NIPAM-co-MAA), and they would act as polymeric amphiphiles. It is believed that the hydrophilic copolymer can stabilize the hydrophobic core of the lipid. The critical association concentrations were determined to be 32, 112, and 158 mg/l, when the lipid/copolymer ratios were 1:5, 1:23, and 1:50, respectively.     

丙醇-硫酸铵双水相体系萃取金(Ⅲ)-氯化物-罗丹明B

水溶性聚合物如聚乙二醇 (ＰＥＧ )、吐温(Ｔｗｅｅｎ) 80的水溶液在电解质存在下萃取分离贵金属离子已有报道[1] ;小分子的有机物如乙醇、丙醇在硫酸铵、氯化钠等电解质存在下也能分为两相形成双水相体系 ,可应用于金属离子的分离[2 ] ;该类体系也可以用于萃取分离贵金属络阴离子[3,4] 。我们发现金 (Ⅲ )与氯离子在碱性染料罗丹明Ｂ(ＲｈＢ)参与下所形成的三元缔合物 ,可被丙醇 硫酸铵双水相体系定量萃取而与大量常见贱金属分离 ,体系同时具有溶剂萃取法及溶剂浮选法的优点 :既可以分离简单贵金属络阴离子[3,4] ,又可以分离贵金属三元缔…     

二氧化硅纳米粒子表面修饰及其表征

采用溶胶-凝胶法合成粒径在50—150nm范围内的二氧化硅（SiO2）纳米粒子。用甲基丙烯酸-3-（三甲氧基硅基）丙酯（MPS）对SiO2纳米粒子表面进行修饰,使其表面接枝能参与自由基聚合反应的碳碳双键基团。用元素分析、FTIR、^13C CP／MASNMR和^29Si CP／MASNMR等手段对修饰过的SiO2纳米粒子进行表征,以确证MPS接枝在SiO2纳米粒子上。分析修饰过的SiO2纳米粒子的^29Si CP／MASNMR和FTIR谱图,还可初步推断MPS接枝在SiO2纳米粒子表面的机理：MPS首先发生水解缩合反应形成低聚物,然后通过氢键作用吸附到SiO2纳米粒子表面,最后MPS低聚物中未缩合的硅羟基与SiO2纳米粒子表面的硅羟基发生缩合反应。     

Fabrication of Electrochemical Immunosensor for Detection of Interleukin 8 Biomarker via Layer-by-layer Self-assembly Process on Cost-effective Fluorine Tin Oxide Electrode

A highly sensitive impedimetric immunosensor for the determination of interleukin 8 (IL 8) cancer biomarker was fabricated via simple fabrication process. A silane agent with isocyanate groups, 3-(triethoxysilyl)propyl isocyanate (IPTES), were utilized for binding of IL 8 antigen specific antibodies and self-assembled on the fluorine tin oxide (FTO) substrate with a standard silanization chemistry. Under optimum experimental conditions, the designed immunosensor had a wide linear detection range of 0.02–4 pg/mL, a low limit of detection of 11.9 fg/mL and a high sensitivity of 4.42 kΩ pg⁻¹ mL cm⁻². The designed biosensor displayed high reproducibility and repeatability, good selectivity against interference biomarkers.