Synthesis and characterization of NH2-porphyrins covalently immobilized on modified-SBA-15

The immobilization of two different succinic-modified carboxy-imide-porphyrins on the surface of amino-modified SBA-15 is reported. The SBA-15 was synthesized and modified by reacting its hydroxyls groups with the OH and/or OR groups of 3-amino propyl triethoxy silane, anchoring the amino group on its surface. Separately, two different derivatives amino-porphyrins (NH₂-5-m-Etio-III-Ni²⁺ and NH₂-2βpyrrolic-m-5,10,15,20-TPP-Ni²⁺) were modified using succinic anhydride to provides these with the carboxyl group appropriate to react covalently with the amino groups previously anchored on the SBA-15; these new hybrid materials have the appropriated textural and chemical characteristics to be used in heterogeneous catalysis. The samples were characterized by XRD, N₂ adsorption isotherms, HR-TEM, TGA/DTA, FTIR, UV/VIS, ¹³C and ²⁹Si NMR-CP/MAS.     

Carbon-beryllium binding in CH2Be

Ab initio molecular orbital theory is used to study carbon-beryllium binding in the lowest singlet and triplet states of CH₂Be. When electron correlation is included, both singlet and triplet states are significantly bound relative to the ground states of CH₂ and Be fragments.     

氢原子在Be(0001)表面吸附的密度泛函理论研究

采用第一性原理的密度泛函理论研究单个氢原子和多个氢原子在Be(0001)表面吸附性质.给出了氢吸附Be(0001)薄膜表面的原子结构、吸附能、饱和度、功函数、偶极修正等特性参数.同时也讨论了相关吸附性质与氢原子覆盖度(0.06-1.33ML)的关系.计算结果表明:氢原子的吸附位置与覆盖度之间有强烈的依赖关系,覆盖度低于0.67ML时,氢原子能量上易于占据fcc或hcp的中空位置;覆盖度为0.78ML时,中空位与桥位为氢原子的最佳吸附位;覆盖度在0.89到1.00ML时,桥位是氢原子吸附能量最有利的位置;以上覆盖度中Be(0001)表面最外层铍原子的结构均没有发生明显变化.当覆盖度为1.11-1.33ML,高覆盖度下Be(0001)表面的最外层铍原子部分发生膨胀,近邻氢原子渗入到铍表面次层,氢原子易于占据在hcp和桥位.吸附结构中的氢原子比氢分子中的原子稳定.当覆盖度大1.33ML时,计算结果没有发现相对于氢分子更稳定的吸氢结构.同时从分析偶极修正和氢原子吸附垂直高度随覆盖度的变化关系判断氢覆盖度为1.33ML时,在Be(0001)表面吸附达到饱和.     

Structure and stability of Be6, Be,and Be clusters

The structure and stability of Be₆, Be, and Be clusters have been investigated at the B3LYP, B3PW91, and second‐order Møller–Plesset (MP2) levels of theory, along with the 6‐311G* basis set for neutral and cationic clusters and the 6‐311+G* basis set for anion clusters. CCSD(T)/6‐311+G* has also been used to calculate some neutral structure to find the most stable structure. Twelve Be₆, six Be, and eight Be isomers are identified. The distortion octahedron structure, pentagonal pyramids structure, and trapezoidal bipyramid structure are found to be the most stable structure on the neutral, cationic, and anionic surface, respectively. They are in agreement with the results reported previously. Natural bond orbital (NBO) analysis, molecular orbital (MO) pictures, and the nucleus independent chemical shift (NICS) values suggest aromatic of the neutral and cationic clusters and antiaromatic of the anionic cluster. The multi‐center σ bonds and delocalized π bonds play important role in the bonding of the beryllium clusters. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

~(10)BE AND THE ACCUMULATIONEVOLUTION OF LOESS

We report here a first series of ~(10)Be measurements on loess samples covering the last 750,000 years. The close correlation of the ~(10)Be data with δ~(18)O variations from deep sea cores allows for establishing a preliminary time scale. Based on this time scale accumulation rates and ~(10)Be fluxes can be calculated. The accumulation-evolution of loess is also discussed in terms of a simple qualitative model of ~(10)Be.     

Evanescent-field-induced two-photon fluorescence: excitation of macroscopic areas of planar waveguides

Two-photon excitation (TPE) of fluorescence is a powerful tool for separating a faintly emitted fluorescence signal from background excitation noise. Until now TPE has only been accomplished for very small excitation areas of a few square micrometre dimensions since they are readily available in the focal zone of high-power lasers. In this paper we demonstrate, to our knowledge for the first time, two-photon excited fluorescence with planar thin-film waveguide structures of macroscopic excitation areas of the order of square millimetres to square centimetres. Based upon our results, it can be envisaged that the new combination of planar waveguide technology with TPE will become a powerful tool for macroscopic surface-interaction studies. It can also open the way for further improving the sensitivity of biosensing platforms like genomic and proteomic microarrays based upon planar waveguides. Received: 7 November 2001 / Published online: 23 November 2001     

Temperatures in 3D optical lattices influenced by neighbouring transitions

A detailed experimental study of the steady-state temperature in a 3D optical lattice for cesium has been performed for a wide range of detunings. Specifically, we have investigated the situation with the cooling and trapping light detuned far red of a ( J _g↦J _e = J _g + 1)-transition, where the blue detuned interaction with a ( J _g↦J _e = J _g)-transition can not be neglected. We find that the temperature scales with the optical potential due to the interaction with just the ( J _g↦J _e = J _g + 1)-transition. This indicates that blue Sisyphus cooling has essentially no effect on the dynamics of the system, when there exists a neighbouring red detuned transition. Received 6 June 2000 and Received in final form 26 September 2000     

Atomic reflection from a magnetic mirror: Beyond the adiabatic approximation

We present theoretical calculations for the reflection of atoms from a magnetic surface with a sinusoidal magnetization. A fully quantum mechanical treatment is possible because the problem may be reduced to an effective one-dimensional one. Results of numerical wave-packet calculations are presented and compared with an analytical model in which the atoms separate into different internal state components which follow classical paths in different potentials. Received 21 October 1999 and Received in final form 18 January 2000