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111.
Juan Manuel Benito David Rodríguez-Lucena José Luis Jiménez Blanco Carmen Ortiz Mellet José Manuel García Fernández 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):147-150
A new concept for the de novo synthesis of artificial glyconanocavities is presented. The use of alternating α,α′-trehalose building blocks and (thio)urea segments allows the efficient synthesis of a new family of cyclooligosaccharides,
namely cyclotrehalans (CTs), featuring a convex-shaped cavity with an apolar environment. CTs are designed to exhibit molecular inclusion abilities
similar to that of cyclodextrins (CDs). Contrary to CDs, CTs expose the monosaccharide β-face to the inner cavity, while the (thio)urea tethers provides some conformational adaptability. High-yielding syntheses
of a series of CTs and a preliminary evaluation of their inclusion properties are reported. 相似文献
112.
Robustness experiments are performed in analytical chemistry to assess the behaviour of an analytical procedure under conditions slightly different from those of the experimental optimum. This work presents a study of robustness applied to a previously proposed fluorescent methodology using two replicated 2(7-4) saturated fractional factorial designs. A comparison is established between three different ways to test the significance of the effects of the variables involved on the response signal. Critical discussions about the most appropriate threshold to be introduced when testing for significance of the factors and the influence of the time necessary to carry out the experiments are included. 相似文献
113.
The adsorption of hydroxyl on Pt(1 1 1) single crystal electrodes from aqueous acidic solutions is carefully reinvestigated. The effect of small additions (10−8–10−5 M) of chloride and bisulphate anions on the OH adsorption region in perchloric acid solution has been studied. Two regions can be differentiated in the voltammetric profile, that behave differently after the addition of the foreign anion. The initial broad adsorption process is unaffected until the highest concentration is attained. However, the sharper peak at higher potentials is affected even at the lower anion concentration. Since mass transport limitations allow to discard the anion adsorption as the main process giving this peak, we propose that the two processes are due to the dissociative adsorption of two different kinds of water, that are affected by the anion in a different way. From this idea, a new model, based on the Frumkin adsorption isotherm, is proposed, which gives an excellent fit of the experimental results. 相似文献
114.
Using a multireferent MBPT method (CIPSI) the electronic affinity (EA) of F, CN and HCC is computed. Results show how UMP2 gives unbalanced truncation of the MP series, while ROMP2 has the correct (balanced) behaviour. The good agreement with the experimental EA found for some compounds is accidental and associated to an error compensation. The good agreement with the experimental data found for the ROMP2 and CIPSI EAs is analysed.This paper was presented at the International Conference on The Impact of Supercomputers on Chemistry, held at the University of London, London, UK, 13–16 April 1987 相似文献
115.
四氢呋喃(THF)-Na2O-SiO2-Al2O3-H2O体系水热合成的THF-FER沸石,经酸交 换-焙烧脱THF(Ⅰ)或焙烧脱THF-酸交换(Ⅱ)的不同方式处理,均可制得低钠H- FER沸石。经XRD,^27Al与^29Si MAS NMR,低温氮吸附等表征证明,通过1273K高温 的热处理和1073K饱和水蒸气下的水热处理,H-FER沸石骨架保持高度稳定。在高温 水蒸气作用下,Si(2Al)容易从骨架上脱离,而Si(1Al)则保持相对稳定,以(Ⅱ )方法处理,制备的H-FER沸石在水热条件下易产生较多的硅差劲基缺陷。经高温 热和水热处理后,H-FER沸石孔道结构基本保持完美、开放。 相似文献
116.
A rapid and simple method, the so-called stearic acid method (SAM) was developed to prepare nanostructured TiO2/SnO2 binary oxides by combustion of stearic acid precursors. The preparative process was studied by Fourier transform infrared spectroscopy (FT-IR). During the preparative process, metal precursors were dispersed in stearic acid at molecular level. Microstructure of the samples was investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), BET specific surface area measurement and the results were compared with those obtained by conventional sol-gel method. The photocatalytic decomposition of methyl orange was used as a model system to determine the relative influences of the preparation method and the concentration of SnO2 on the photocatalytic activities. It was found that preparative methods affected the crystalline structure of TiO2/SnO2 powders and the anatase phase of TiO2 was stabilized by the addition of SnO2 in SAM. The samples prepared by SAM showed better dispersity, larger specific surface area and the TiO2/SnO2 (r=0.15, SAM) catalyst showed higher photocatalytic activity than Degussa P25. 相似文献
117.
118.
Interaction of atomic hydrogen with cluster models simulating the Rh(111) surface has been studied at the ab initio SCF level using relativistic non-empirical pseudopotentials and moderately large basis sets. From the bonding parameters, it is seen that chemisorption on the threefold open position is five times more favoured than on the threefold eclipsed one, and the bonding picture is rather different for both active sites. Since two different kinds of adsorbed hydrogen atoms should exist according to various experimental techniques, the present work adds further evidence to the existence of these two types of adsorption and reports some structural parameters which can help to a more detailed characterization in the near future. 相似文献
119.
On the basis of a detailed study of the pilocarpine-induced nickel(II) pre-wave using various polarographic techniques, an electrode process mechanism is proposed in which the formation of a catalytic complex between aquo-nickel(II) and veronalate-nickel(II) on the one hand and unprotonated pilocarpine adsorbed on the electrode surface on the other is followed by the reduction of nickel(II) in the complex and the release of the catalytic ligand. The pre-peak recorded by differential-pulse polarography in the system 1 × 10?3 M Ni(II)-1 × 10?2 M sodium veronal, nitric acid (pH 8.5) (with ionic strength maintained at 0.2 with sodium nitrate) can be used for quantitative determination of pilocarpine at concentrations in the range 2.5 × 10?7-8 × 10?6 M. 相似文献
120.
Effect of multi-walled carbon nanotubes on non-isothermal crystallization kinetics of polyamide 6 总被引:2,自引:0,他引:2
The non-isothermal crystallization behaviors of multi-walled carbon nanotubes (MWNTs)/polyamide 6 (PA6) composites were investigated by differential scanning calorimetry (DSC). Three methods, namely, Avrami, Ozawa and Mo, were carried out to analyze the non-isothermal crystallization data. The results showed that the MWNTs in PA6 acted as effective nucleation agents. However the crystallization rate of composites obtained was lower than that of the neat PA6. It is indicated that the presence of MWNTs influenced the mechanism of nucleation and the growth of PA6 crystallites. 相似文献