Preparation of nano-sized silica with solar energy conversion and storage function by immobilization of norbornadiene moieties to hyperbranched poly(amido amine)-grafted nano-sized silica

The immobilization of norbornadiene (NBD) moieties onto nano-sized silica surface by the direct condensation of the surface terminal amino groups of hyperbranched poly(amido amine) (PAMAM)-grafted silica with 3-phenyl-2,5-norbornadiene-2-carboxylic acid is examined. It is found that the immobilization of NBD moieties onto the silica successfully proceeds in the presence of N,N′-dicyclohexylcarbodiimide (DCC) as a condensing agent. The immobilized NBD moieties onto the silica surface increases with increasing amount of amino groups of hyperbranched PAMAM-grafted silica, but the percentage of amino groups used for the immobilization of NBD moieties is decreased. The immobilized NBD moieties on the silica surface are readily isomerized to quadricyclane (QD) by photo-irradiation in n-hexane. Stored thermal energy by QD-immobilized silica is released as thermal energy by heating. The stored thermal energy of QD-immobilized silica increases with progress of the photo-irradiation time and became constant, about 30 J/g-silica, after 2 h.     

Synthesis of Novel Double Network Hydrogels via Atom Transfer Radical Polymerization

Novel double network (DN) hydrogels were prepared via atom transfer radical polymerization (ATRP) of the first network using two different initiators, and followed by ultraviolet (UV) photo-initiated polymerization for the second network. The first networks of DN hydrogels were prepared by using two different initiators; one is a one-side initiator, and the other is a double-side initiator. The mechanical properties of various DN gels, such as water content and compressive strength, were studied. The network structure of the DN hydrogels was also characterized by dynamic light scattering. Thus, we demonstrated that the ATRP method is useful to control the network structure of the first network for DN gels. Extensive inhomogeneous structure of the first network was obtained by ATRP method and increased both the swelling degree and softness of DN gels.     

Preparation of poly(vinyl alcohol)–silicone based hybrid membranes for the pervaporation separation of water–acetic acid mixtures

Hybrid membranes were prepared using poly(vinyl alcohol) (PVA) and tetraethylorthosilicate (TEOS) via hydrolysis followed by condensation. The obtained membranes were characterized by Fourier transform infrared spectroscopy, wide-angle x-ray diffraction and differential scanning calorimetry. A remarkable decrease in degree of swelling was observed with increasing TEOS content in membranes and is attributed to the formation of hydrogen bonding and covalent bonds in the membrane matrix. The pervaporation performance of these membranes for the separation of water–acetic acid mixtures was investigated in terms of feed concentration and the content of TEOS used as cross-linking agent. The membrane containing 1 : 2 mass ratio of PVA and TEOS gave the highest separation selectivity of 1116 with a flux of 3.33 × 10^?2kg/m²h at 30°C for 10 mass% of water in the feed. Except for membrane M-1, the observed values of water flux are close to the values of total flux in the investigated composition range, signifying that the developed membranes are highly water selective. From the temperature dependence of diffusion and permeation values, the Arrhenius apparent activation parameters have been estimated. The resulting activation energy values obtained, showing that water permeation is lower than that of acetic acid, suggest that the membranes have higher separation efficiency. The activation energy values calculated for total permeation and water permeation are close to each other for all the membranes except membrane M-1, signifying that coupled-transport is minimal because of the higher selective nature of membranes. The negative heat of sorption values (ΔH _s) for water in all the membranes suggests a Langmuir mode of sorption.     

On group orders of rational points of elliptic curves

We consider elliptic curves without complex multiplication defined over the rationals or with complex multiplication defined over the Hilbert class field of the endomorphism ring. We examine the distribution of almost prime group orders of these curves when reduced modulo a prime ideal.     

Intramolecularity and enzyme modelling: a critique

A critical reappraisal of the concept of intramolecularity is attempted, but particulary focussed on the effective molarity (EM) criterion and the relationship of intramolecularity to enzymic reactivity. The prevalent ambiguities in the EM concept are addressed and a revised definition (EM_rev) is suggested. It is argued that there are fundamental limitations to the use of intramolecular reactions as enzyme models. Although the simplest mechanism for enzymic reactivity is based on transition state stabilisation, an alternative (although complex) possibility is based on the stabilisation of the enzyme. Possible mechanisms for the utilisation of the enzymic free energy for effecting catalysis are discussed.     

低能离子束研究N[+]-CoNi(100),Co/Cu(100)系统化学吸附键的性质

离子束技术可以研究气态下离子和分子的相互作用,近来又用于研究离子和吸附分子的相互作用.通常气体分子在单晶表面上的吸附是定向的,故这种吸附不仅可以用来研究不同方向入射的离子束与吸附分子的相互作用,从中还可以获得有关吸附分子和表面基片原子之间的键合信息及入射离子在表面的中和效应信息.本文研究了10eV 的 N~ 离子束在清洁的和吸附了 CO 分子的 Ni(100)和 Cu(100)表面上的中和效应及其与 CO 的相互作用.选择该系统的原因是:(1)基态 N_2分子对清洁的 Ni,Cu 表面是不活泼的,在室温下无化学吸附;(2)关于 CO 在 Ni(100)和 Cu(100)表面上的化学吸附特性已有了充分的了解;(3)有关气相的 N~ -CO 系统的离子-分子相互作用亦已有了较为完整的研究.所以本文研究结果便于     

配合物生成反应速率常数与配体酸离解常数之间的直线自由能关系 V. 铜(II)-2,9-二甲基邻菲罗啉与α-氨基酸和N-苯基乙二胺生成三元配合物的动力学研究

应用温度跃迁装置和断流分光光度计分别研究了铜(II)-2,9-二甲基邻菲罗啉与α-氨基酸和N-苯基乙二胺在25℃、0.1mol·dm^-^3KNO3水溶液中的生成反应动力学。实验结果表明在铜(II)-2,9-二甲基邻菲罗啉-α-氨基酸三元配合物的生成速率常数与配体α-氨基酸的酸离解常数之间存在着如下的直线自由能关系: logkf=2.84+0.53pK2。根据Eigen机理讨论了铜(II)-2,9-二甲基邻菲罗啉-N-苯基乙二胺三元配合物的生成反应动力学。     

BaGdB~9O~16中Dy^3+的发光和Ce^3+, Gd^3+驿Dy^3+的能量传递

我们研究了在紫外光(UV)激发下, Dy^3+单掺杂和Ce^3+, Dy^3+共掺杂的BaGdB~9O~16的发射光谱、激发光谱及发光强度随组成变化的规律性, 发现Ce^3+,Gd^3+均对Dy^3+的发光起敏化作用。Ce^3+吸收的能量大部分直接传递给Dy^3+, 小部分以Ce^3+→Gd^3+→(Gd^3+)~n→Dy^3+形式传递给Dy^3+。Ce^3+→Dy^3+能量传递和Dy^3+自身浓度猝灭机理分别为电偶极-电偶极和电偶极-电四级相互作用。     

锌酞菁类染料的氧化还原电位研究

金属酞菁染料对红光及近红外光有强吸收,并且具有半导体的性能。由于它具有性质稳定,合成方便等特点,这类染料在传统的染料、颜料工业中有着重要的地位;近年来在太阳能的利用,氧化还原反应的光敏化等方面引起了人们很大的注意。由于一般的金属酞菁染料的溶解度很差,常使它们的应用受到限制。为此,我们合成了一系列在环上带有各种取代基的锌酞菁染料(ZnPcR),以改善其溶解度,并对它们的氧化还原电位和分子结构与轨道能级之间的关系进行了研究。     

OBSERVATION OF ENERGY DISSIPATION PEAK IN POLYSTYRENE MELT ABOVE Tg

In this paper two different kinds of dynamic mechanical techniques(inversed torsion pendulum and energy dissipation apparatus)were used to study the dynamic behavior of atactic monodisperse polystyrene above glass transition. The plots of energy dissipation versus temperature were presented for two atactic polystyrene samples.An apparent energy dissipation peak occurred above T_g in each plot measured by the inversed torsion pendulum,and simultaneously the sample was found to flow assuredly at the moment.To exclude the influence of the flow and demonstrate there was a peak indeed above T_g,the energy dissipation apparatus was used,in which the samples were put into a cup.An obvious peak appeared, and it was in agreement with the peak observed by the inversed torsion pendulum.On basis of the results measured by the two kinds of apparatus,a conclusion is drawn that a peak occurrs above T_g,which gives a manifestation for the existence of the liquid-liquid transition.