Synthesis and characterization of novel AZO chromophore with multi hydroxyl groups

Novel organic second order nonlinear optical chromophore with 4,4′-(5-(bis(2-hydroxyethyl)amino)-1,3-phenylene)bis(oxy)dibutan-1-ol as electron donor and azo thiophene as π-electronic bridge was synthesized and characterized by ¹H NMR spectra and mass spectra. After the introduction of four hydroxyl groups to the electron donor, the solubility of chromophore Z1 in water was improved greatly (0.5 g). Else, the solubility of chromophore Z1 in common organic solvents was still very good. The thermal decomposition temperature was above 250 °C, which was high enough for its application in both the preparation of optoelectronic devices and Second harmonic generation imaging. Electro-optical films prepared by chromophore Z1 showed us the largest second-order nonlinear optical coefficient was about 85 pm/V, which was large enough for the detection of second harmonic generation signal in water solution. Else, the photochemical stability of chromophore Z1 was also studied; the advantage of chromophore with azo bond was very obvious for improving the photochemical stability of organic second order nonlinear optical chromophores.     

Langmuir-Blodgett films of ethylenedithiotetrathiafulvalene derivative containing hydroxyl groups

Langmuir-Blodgett (LB) films of an ethylenedithiotetrathiafulvalene (EDT-TTF) derivative containing hydroxyl groups, 4, 5-bis(11-hydroxyundecylthio)-4′, 5′-ethylenedithiotetrathiafulvalene were deposited without using stabilizer molecules. Doping of the film with iodine leads to oxidation of EDT-TTF moiety as evidenced by UV-vis and IR spectroscopy. X-ray diffraction studies reveal the presence of layered arrangement of the EDT-TTF derivative molecules in the LB film. Cyclic voltammetry studies indicate that the electrochemical oxidation of the EDT-TTF derivative in its LB film is irreversible. Due to the insulating nature of the alkyl chains, only the first layer of the LB film was found to be redox-active. The electrical conductivity of the 25 layer LB film was found to increase by two orders of magnitude on doping with iodine. On equilibrating the doped film in air, the conductivity gradually reduced with time and finally reached the conductivity of undoped film. This reversibility could be because of the steric hindrance induced by the two long alkyl groups. The alkyl chains help in rendering the EDT-TTF molecule amiable to LB film formation but are found to reduce the electrical conductivity of the films and also cause instability of the doped state. The hydroxyl groups at the end of the alky chain impart amphiphilic nature to the molecules and help in stabilizing the film at the air-water interface.     

新型低含量羟基有机-无机杂化材料的合成

采用二苯基二羟基硅烷分别和两种不同的硅烷偶联剂γ-甲基丙烯酰氧基丙基三甲氧基硅烷、γ-缩水甘油醚氧丙基三甲氧基硅烷作为先驱体,用无水溶胶-凝胶法合成出有机-无机杂化材料,将其旋涂在硅基片和石英玻璃片上得到杂化光学薄膜.用Fourier红外光谱仪和Raman光谱仪测试了薄膜的红外吸收光谱和Raman散射光谱,用Abbe折...     

The structure and motion of water and hydroxyl groups in hydrosodalite

Instationary ¹H nuclear magnetic resonance (n.m.r.) techniques (free induction decay, solid echo, Hahn's echo) were used to study the OH groups and water molecules in hydrosodalite in the temperature range 120–420 K. From these experiments the number of OH groups, the microdynamical behaviour of water molecules and the distribution function for the number of water molecules per cubooctahedron in dependence on the average pore filling factor could be determined.     

Type,stability, and acidity of hydroxyl groups of HNaK-erionites

The concentration and acid strength of the hydroxyl groups of a series of HNaK erionites have been investigated by means of temperature programmed activation (t.p.a.), temperature programmed desorption (t.p.d.) of ammonia, and transmission absorption i.r. spectroscopy. With an increasing degree of NH₄⁺ exchange, primarily Na⁺, at first, and, subsequently, K⁺ cations are replaced. During activation of these materials, NH₃ desorbs in a temperature interval from 540 to 900 K, leading to hydroxyl groups. However, it is impossible to decompose NH₄⁺ quantitatively without dealumination, if the degree of NH₄⁺ exchange is higher than 85%. Five types of hydroxyl groups are present, characterized by i.r. bands at approximately 3741, 3691, 3660, 3618-3608, and 3566 cm⁻¹. The assignment of these bands is discussed. Only the OH groups represented by the bands at 3660, 3618–3608, and 3566 cm⁻¹ adsorb ammonia under the conditions employed. The concentration and strength of the bridging hydroxyls (3618-3608 cm⁻¹), associated with framework Al³⁺, increase with increasing degree of ion exchange.     

Evidence for the presence of superacid nonframework hydroxyl groups in dealuminated HY zeolites

The presence of a hydroxyl i.r. band at 3610 cm⁻¹ that interacts with pyridine at desorption temperatures up to 400°C is detected in dealuminated HY zeolite and tentatively assigned to an amorphous silica—alumina phase, formed upon dealumination.     

Oxygen-containing functional groups on the oxidized surface of a carbon nanomaterial

The composition of the oxygen-containing surface functional groups produced by the oxidation of the Tekhnosorb carbon nanocomposite material is studied using chemical analysis and titrimetry. The oxygen-containing groups on the carbon surface are identified by IR spectroscopy. The oxygen content of the surface functional groups is determined as a function of oxidation conditions, and the static exchange capacity of the material is shown to correlate with its surface composition.     

Siting of AI and bridging hydroxyl groups in ZSM-5: A computer simulation study

The siting of AI and of bridging OH groups in zeolite HZSM-5 is studied by defect energy minimization adopting the classical shell model. The small energy differences between the various lattice sites suggest that there would be little deviation from a random distribution of bridging hydroxyl groups and AI over the possible framework sites in contrast to previous suggestions.     

Magnetism in Granular Systems

Previous experimental studies have shown that the magnetic dipolar interaction plays an important role in several magnetic properties of nanoparticulated systems. More recently, this type of interaction was detected in microparticles of Fe?CMn?CAl, Fe?CSi and Fe?CAl systems. In this work, we apply the M?rup?CTronc (Phys. Rev. Lett. 72:3278, 1994) model for nanoparticulated systems in order to calculate some thermodynamic properties of these systems. We first calculated the total energy of a magnetic particle as the sum of its anisotropy energy and its total dipolar magnetic interaction with the other particles. The calculation is performed in such a way that the interaction energy has the same form as the anisotropy energy. We use the total energy to calculate the magnetization, heat capacity, magnetic susceptibility, and blocking temperature in nanoparticulated systems. The application of our theory to experimental data on nanoparticulated systems and for the Fe?CAl, Fe?CSi and Fe?CMn?CAl microparticulated granular systems will be presented elsewhere.     

Magnetism in Double Perovskites

Double-perovskite compounds with general formula ABB′O₆, have attracted a lot of attention in recent years due to a variety of properties exhibited by them. In this paper, we will review our recent study on a number of double-perovskite compounds, namely La-doped Sr₂FeMoO₆, Cr-based family of compounds, Sr₂CrXO₆ (X=W, Re, Os), characterized with spectacularly high ferromagnetic transition temperatures and the magneto-capacitive compound, La₂NiMnO₆, We will discuss the signature of hybridization-driven antiferromagnetism in La-doped Sr₂FeMoO₆, while the parent compound, Sr₂FeMoO₆, is a half-metallic ferromagnet. The magnetism in the 3d–5d double perovskite Sr₂CrXO₆ (X=W, Re, Os) is found to be driven by the interplay of the hybridization-driven mechanism and the superexchange, which resulted into progressive increase of T _c as one moves from W to Re to Os at the B′ site. Our work, in the context of La₂NiMnO₆, identifies its superexchange-driven microscopic origin being responsible for the near room-temperature insulating ferromagnetic behavior.     

Vanishing stick-slip friction in few-layer graphenes: the thickness effect

We report the thickness dependence of intrinsic friction in few-layer graphenes, adopting molecular dynamics simulations. The friction force drops dramatically with decreasing number of layers and finally approaches zero with two or three layers. The results, which are robust over a wide range of temperature, shear velocity, and pressure are quantitatively explained by a theoretical model with regard to lateral stiffness, slip length, and maximum lateral force, which could provide a new conceptual framework for understanding stick-slip friction. The results reveal the crucial role of the dimensional effect in nanoscale friction, and could be helpful in the design of graphene-based nanodevices.     

含氧化叔胺侧基的水溶性酚醛树脂的制备及性能

利用双氧水将N，N-二甲胺基苯甲酸中的叔胺基团氧化，得到氧化叔胺苯甲酸（OTBA）。然后，OTBA与环氧酚醛树脂F-44进行反应，得到含有极性氧化叔胺侧基的改性酚醛树脂。该树脂易溶于水并具有热敏性，树脂在热的作用下能够分解并失去水溶性，但仍可溶于一般有机溶剂。该树脂和一种830nm红外增感染料一起使用时，树脂对红外光线敏感，并且能够通过830nm红外光曝光和中性水显影得到较为清晰的阴图型图像。     

Magnetism in dopant-free ZnO nanoplates

It is known that bulk ZnO is a nonmagnetic material. However, the electronic band structure of ZnO is severely distorted when the ZnO is in the shape of a very thin plate with its dimension along the c-axis reduced to a few nanometers while keeping the bulk scale sizes in the other two dimensions. We found that the chemically synthesized ZnO nanoplates exhibit magnetism even at room temperature. First-principles calculations show a growing asymmetry in the spin distribution within the distorted bands formed from Zn (3d) and O (2p) orbitals with the reduction of thickness of the ZnO nanoplates, which is suggested to be responsible for the observed magnetism. In contrast, reducing the dimension along the a- or b-axes of a ZnO crystal does not yield any magnetism for ZnO nanowires that grow along c-axis, suggesting that the internal electric field produced by the large {0001} polar surfaces of the nanoplates may be responsible for the distorted electronic band structures of thin ZnO nanoplates.     

Magnetism in ultracold quantum gases

Abstract

We study the static and dynamic magnetic properties of ultracold quantum gases, in particular the spinor physics of F = 1 and F = 2 Bose-Einstein condensates of ⁸⁷Rb atoms. Our data lead to the conclusion, that the F = 2 ground state of ⁸⁷Rb is polar, while we find the F = 1 ground state to be ferromagnetic. The dynamics of spinor systems is linked to an interplay between coherent mean-field interactions, losses and interactions with atoms in the thermal cloud. Within this rich parameter space we observe indications for coherent spinor dynamics and novel thermalization regimes.     

羰基、羧基和羟基表面官能团对碳纳米管电容量的影响

分别采用混酸、空气、硝酸和高锰酸钾对碳纳米管进行氧化处理,以在其表面引入官能团,进而研究了表面官能团对碳纳米管电化学性能的影响.X-射线光电子谱分析表明:混酸氧化处理引入的官能团主要为羰基和羧基;空气氧化使碳纳米管表面链接较多的羟基,但羰基和羧基的含量最少;而硝酸处理和高锰酸钾处理引入了中等数量的羰基和羧基.经四种处理方法所得碳纳米管具有相近的比表面积和孔结构.通过比较它们的比电容发现:羰基和羧基贡献了最多的准电容,尤其羰基含量与碳纳米管的电容量呈正比关系;而羟基主要增强了双层电容,并未引入明显的准法拉第容量.由于羰基和羧基比羟基具有更低的电荷传递电阻,有利于快速的法拉第反应,从而引入准电容.     

The effects of hydroxyl groups on Ca adsorption on rutile surfaces: a first-principles study

Hydroxyl groups on titanium surfaces have been believed to play an important role in absorbing Ca in solution, which is crucial in the formation of bioactive calcium phosphates both in vitro and in vivo. CASTEP, a first-principles density functional theory (DFT) code, was employed to investigate Ca adsorption on various rutile (110) surfaces in order to clarify how hydroxyl groups effect Ca adsorption. The surfaces modeled in the present study include a bare rutile (110) surface, a hydroxylated rutile (110) surface, an oxidized rutile (110) surface, and a rutile (110) surface bonded with mixed OH groups and water. The results reveal that not all OH groups favors to attract Ca adsorption and loosely bonded OH and water on a rutile surface actually combine with Ca during adsorption. An oxidized rutile surface has the highest ability to attract Ca atoms, which partially explains that alkali-treated Ti surfaces could induce hydroxyapatite formation in alkaline environments.