The Photochemistry of Diazomethane the Reactions of Methylene with Toluene and P-Xylene in Liquid Phase (I)

The photochemistry of diazomethane in toluene and p-xylene solutions was investigated. The reactions of methylene with toluene gave eight products. In the diazomethane p-xylene solution, p-ethyltoluene, 1,2,4-trimethylbenzene, 1,4-dimethylcyclohepatriene-1,3,5 and three unidentified compounds were found as products of the reaction of methylene with p-xylene. The relative rates of addition and insertion reaction of methylene with toluene and p-xylene have been calculated.     

贫水电解质体系制备多孔阳极氧化铝模板的研究

在有机溶剂为主的含草酸电解质中,研究了大孔径有序度高的阳极氧化铝(AAO)的一步法电化学制备.实验证实,电解质中水含量的降低能够有效抑制铝的电氧化速率和溶解速率,使得其氧化膜孔道的生长能够稳定进行,所得到的六方孔道排列有序度明显高于纯水溶剂制备的电解质体系下的产物.考察了水含量、有机溶剂种类以及电解质浓度对AAO模板孔道形貌的影响.结果表明,有机溶剂贫水电解质体系使得电氧化电压的选取范围比水溶液电解质体系更宽,孔径连续可调,反应条件温和.该方法适合于制备均匀大孔径的AAO模板.     

Surface hydration and its effect on fluorinated SAM formation on SiO2 surfaces

Substrate hydration is demonstrated to be crucial to film quality during self-assembled (SA) film deposition of tridecafluoro-1,1,2,2,-tetrahydrooctyltrichlorosilane (FOTS) from the vapor phase. The surface hydration was studied by thermogravimetric analysis, and a model was developed to predict the conditions necessary to desorb all of the water adsorbed on a fused silica surface without significantly altering the concentration of the surface hydroxyl groups. The nature of the SA film was investigated as a function of the degree of rehydration of the dehydrated silica surface. The wettability and microstructure of the SA films were examined by water contact angle, ellipsometry, X-ray photoelectron spectroscopy, and atomic force microscopy. There is an optimum degree of substrate hydration, on the order of 1-1.2 monolayers of adsorbed water, required to produce a dense, durable and uniform FOTS film with high water repellency and a smooth surface.     

A comparative study on photo-induced electron transfer from fluorescein to anthraquinone and injection into colloidal TiO2

A dyad-anthraquinone-methyl ester of fluorescein-and its model compound-butyl ester-were synthesized. The effects of photo-induced electron transfer from fluorescein to an organic anthraquinone acceptor and injection into inorganic colloidal TiO(2) were studied respectively. It is found that the photo-induced electron transferring to an organic acceptor is much faster than injecting into inorganic colloidal particles when fluorescein was excited by visible light. While inorganic colloidal TiO(2) was excited by UV, the electron of fluorescein will inject into TiO(2).     

Specific heat and Lindemann-like parameter of metallic clusters: mono- and polyvalent metals

The Brownian-type molecular dynamics simulation is revisited and applied to study the thermal and geometric properties of four mono- and two polyvalent metallic clusters. For the thermal property, we report the specific heat at constant volume CV and study the solid-liquid-like transition by scrutinizing its characteristic. For the geometric property, we calculate the root mean square relative bond-length fluctuation delta as a function of increasing temperature. The thermal change in delta reflects the movement of atoms and hence is a relevant parameter in understanding the phase transition in clusters. The simulated results for the CV of alkali and aluminum clusters whose ground state structures exhibit icosahedral symmetry generally show one phase transition. In contrast, the tetravalent lead is quite often seen to exhibit two phase transitions, a premelting process followed by a progressive melting. In connection with the premelting scenario, it is found here that those (magic number) clusters identified to be of lesser stability (among other stable ones) according to the second energy difference are clusters showing a greater possibility of undergoing premelting process. This energy criterion applies to aluminum clusters nAl=28 and 38. To delve further into the thermal behavior of clusters, we have analyzed also the thermal variation of deltaT and attempted to correlate it with CV(T). It turns out that the premelting (if exist) and melting temperatures of the smaller size clusters (n less, similar 50) extracted from CV do not always agree quantitatively with that deduced from delta.     

Molecular and nanoscale materials and devices in electronics

Over the past several years, there have been many significant advances toward the realization of electronic computers integrated on the molecular scale and a much greater understanding of the types of materials that will be useful in molecular devices and their properties. It was demonstrated that individual molecules could serve as incomprehensibly tiny switch and wire one million times smaller than those on conventional silicon microchip. This has resulted very recently in the assembly and demonstration of tiny computer logic circuits built from such molecular scale devices. The purpose of this review is to provide a general introduction to molecular and nanoscale materials and devices in electronics.     

Surface composition and property of film prepared with aqueous dispersion of polyurethaneurea-acrylate including fluorinated block copolymer

The aqueous dispersion of polyurethaneurea-acrylate (PUA) including small amount of fluorinated block copolymers containing carboxyl groups (PATF), which can be dissolved in water, was used to make films and the surface properties of these films were examined. The experimental data show that the modified PUA film exhibits a hydrophobic surface property, although the original surface of PUA film is hydrophilic. The surface composition of the modified PUA film was measured by ATR and XPS. The results indicate that there is a concentration gradient of the fluorine groups along the lines of thickness of the modified film and towards the outmost surface layer, resulting from the migration of fluorinated blocks to the air side surface of the modified PUA film during the film formation process. However, the PUA film can not be modified effectively by adding the sodium salt of PATF, since the urethane groups in the system are easy to occupy on the surface of the film.     

水热合成CdS纳米晶体的形貌控制研究

研究了水热合成CdS纳米晶体形貌的化学控制，选择不同的络合试剂为模板,研究其对水热合成CdS纳米晶体形貌的影响.实验发现若以络合试剂乙二胺、甲胺为模板时，产品CdS晶体的形貌分别为（20～30） nm×（200～600） nm和（40～50） nm×（200～600） nm尺寸的纳米棒;而以络合试剂吡啶、 氨为模板时，产品CdS晶体的形貌分别为平均尺寸约30 nm和20 nm的纳米颗粒.用XRD、TEM、XPS、PL和Raman光谱等技术对所得CdS纳米棒进行了表征.同时对水热合成CdS纳米晶体形貌的模板控制机制进行了探讨，提出了一种水热合成CdS纳米棒的络合物结构诱导生长机理.     

Studies on the Total Synthesis of Hainanolide (VII) - Analysis of the Relative Stereochemistry of key Intermediate 2

The natural product, hainanolide 1, also under the name harringtonolide2 demonstrated antitumor and antiviral activities in preliminary test. Its structure was determined by X-ray diffraction. The total synthesis of 1 was reported recently by Mander3. A different scheme of its synthesis has been studied in our laboratory4. Here the determination of the stereochemical structure of the key intermediate 2 in the synthesis was reported. HMBC and HMQC spectra identified the skeleton and H,…     

两性离子流动相测定杂多酸中的磷酸根、氯离子和硫酸根

采用离子色谱法测定杂多酸中痕量阴离子。由于常规的淋洗液(如Na2CO3,NaOH)呈碱性,使杂多酸迅速分解生成磷酸根,致使测定结果偏高。实验通过在常规淋洗液中加入适量两性离子后,调节淋洗液的pH为中性,从而能准确测定杂多酸中磷酸根氯离子和硫酸根的含量值。经过比较分别用去离子水和流动相稀释的样品中磷酸根的测定结果,确定淋洗液的最佳条件为2.5mmol/LNa2CO3-9.0mmol/LCHES,在该条件下测定,快速、准确、灵敏,且有较好的灵敏度和重现性。