pH sensitivity of Si--C linked organic monolayers on crystalline silicon surfaces.

The electrochemical behavior of Si--C linked organic monolayers is studied in electrolyte-insulator-Si devices, under conditions normally encountered in potentiometric biosensors, to gain fundamental knowledge on the behavior of such Si electrodes under practical conditions. This is done via titration experiments, Mott-Schottky data analysis, and data fitting using a site-binding model. The results are compared with those of native SiO(2) layers and native SiO(2) layers modified with hexamethyldisilazane. All samples display pH sensitivity. The number of Si--OH groups on the alkylated samples is calculated to be less than 0.7 % of that of a pure SiO(2) insulator, which still causes a pH sensitivity of approximately 25 mV per pH unit in the pH range: 4-7. The alkylated samples hardly suffer from response changes during up- and down-going titrations, which indicates that very little oxide is additionally formed during the measurements. The pK(a) values of all samples with monolayers (4.0-4.4) are lower than that of native SiO(2) (6.0). The long-term drift (of approximately 1 mV h(-1)) is moderate. The results indicate that biosensors composed of alkylated Si substrates are feasible if a cross-sensitivity towards pH in the sensor signal is taken into account.     

An expedient preparation of Stryker's reagent

A convenient and efficient preparation of Stryker's reagent, [Ph₃PCuH]₆, under homogeneous conditions using silanes as the reducing agent is detailed. The reaction time can be reduced to 1-2 h, and high yields of Stryker's reagent can be routinely achieved. The same method has been extended to the synthesis of [Ph₃PCuD]₆ using Ph₂SiD₂.     

Studying dispersoid systems

Summary Measurements of energy transformation in mitochondria are done on a capillary differential titration calorimeter CTD2156. It is important to mention that a sediment is quickly formed by the mitochondria suspension without mixing by means of a vibrating needle. During the measurements, the vibrating needle is located inside the working volume of the chamber. The design of the calorimeter is substantiated theoretically. It provides a new mode of a reagent input in the measuring volume of the calorimetric chambers. It expands the spectrum of tasks that can be solved using this instrument. In the capillary calorimeter the calorimetric chambers unit is simple and small in size. These advantages of capillary chambers provide an opportunity to unite 20 capillary calorimetric chambers in one calorimetric block. It allows designing a multi-channel titration calorimeter. There are obvious advantages of such a calorimeter over other instruments in screening researches and in researches of objects maintaining stability only for a short time.     

催化光度法测定痕量铜的新体系研究

报道了在Ｈ２ＳＯ４介质中，溴代十六烷基吡啶和活化剂乙二胺存在下，痕量铜催化抗坏血酸还原ＣａｄｉｏｎＩ（苯基重氮氨基偶氮苯）的褪色反应，测定了反应表现活化能，探讨了反应机理，建立了选择性地测定痕量铜的新方法，线性范围为０～１．４μｇ／２５ｍＬ，方法用于人发及食品中痕量铜的测定，结果满意。     

ANISOTROPIC STRAIN EFFECT ON MORPHOLOGY AND ATOMIC STRUCTURE OF VICINAL Si(001) SURFACE

On vicinal Si(001) surfaces, dependence of growth morphology on the applied strain direction and formation of vacancy lines from Ag-induced missing dimer vacancies are studied. Both phenomena are intimately related to the anisotropic nature of the strain field which originates from the surface dimerization. Strain relief mechanism, reflecting on the surface morphology, is shown to be different in two orthogonal directions. Normal to the steps, step-pair bunching and waving lead to formation of hillocks and pits. Along the step direction, bending of step pairs forms a cusp which later develops into a deep groove. Toward the atomic scale, the formation of the vacancy lines is driven by the short-range attractive interaction between the vacancies in adjacent dimer rows and the long-range repulsive interaction between them in the same dimer row. A full form and magnitudes of the interactions are derived from the thermally-excited wandering of the vacancy lines formed by a nominal amount of Ag depositing onto the surface.     

双显色剂高灵敏协同显色反应的研究——钴(Ⅲ)-亚硝基R盐-结晶紫体系

在水溶液中钴(Ⅱ)与亚硝基R盐所形成的配合阴离子可以与有机碱阳离子(结晶紫)缔合形成中性缔合分子。在聚乙烯醇存在下,配合物可稳定存在于水溶液中。钴(Ⅲ)-亚硝基R盐-结晶紫配合物在510nm处有一最大吸收,摩尔吸光系数ε_(510)=1.47×l0~5L·mol~(-1)·cm(-1)。配合物中各组分的摩尔比为:Co:R:CV=1:3:6。反应具有较高的选择性,采用双峰双波长法测定钴可使灵敏度得到进一步提高,相应的摩尔吸光系数ε_(510-640)=4.09×10~5L·mol~(-1)·cm~(-1)。方法用于合成试样中钴的测定,结果满意。     

On the origin of quasi-racemic aplysinopsin cycloadducts, (bis)indole alkaloids isolated from scleractinian corals of the family Dendrophylliidae. Involvement of enantiodefective Diels-Alderases or asymmetric induction in artifact processes involving adventitious catalysts?

Reported here are two novel quasi-racemic (bis)indole alkaloids, cycloaplysinopsin A (5) and cycloaplysinopsin B (6), isolated from tropical Indo-Pacific (Comoros, Philippines) scleractinian corals of the family Dendrophylliidae. Although their structures suggest a Diels-Alder cycloaddition origin from aplysinopsin-type precursors, neither experiments, nor theory allowed us to clearly distinguish an enzymatic process with scarce enantioselection from the intrusion of an adventitious catalyst in the coral extracts, where the chiral environment caused a slight asymmetric induction.     

石墨炉原子吸收法直接测定高温合金中硅

研究了混合基体改进剂，灰北、原子化温度以及共存元素的干扰，采用镧和钙作混合基体改进剂后，硅的灵敏度提高，抗干扰能力增强，可以用石墨炉原子吸收直接测定高温合多中硅。方法特征量为０．２ｎｇ，检出限为２．３μｇ／ｇ，对于含硅量为４００μｇ／ｇ左右的合金样品，相对标准偏差为５％左右，回收率在９０％－１１０％之间。     

CVD法不同条件下制备的多壁碳纳米管的Fenton氧化改性

碳纳米管经焙烧和稀硝酸纯化处理后,在相同的实验条件下,采用Fenton试剂产生的·OH分别对CVD法合成的两种制备条件不同的多壁碳纳米管进行氧化改性处理。红外光谱(FT IR)表明,改性后的两种碳管结构中都引入了羟基、羰基和羧基等含氧官能团。此外,由于制备条件不同,导致它们的石墨化程度、缺陷含量和抗氧化能力等性质也不同,因此CVD法制备条件能够对碳管Fenton氧化改性结果产生重要影响。机理分析表明,这些含氧官能团可以看作是具有强亲电性和强氧化性的·OH对碳管上缺陷位置和不饱和键进行攻击的结果。     

A novel and direct synthesis of chroman derivatives using a hypervalent iodine(III) reagent

The direct aromatic carbon-oxygen bond-formation reaction was described and the novel and simple synthetic method for chroman derivatives involving aromatic cation radical intermediates was developed using the hypervalent iodine(III) reagent, phenyliodine(III) bis(trifluoroacetate) (PIFA).