Synthesis,X‐ray characterization and density functional theory studies of N6‐benzyl‐N6‐methyladenine–M(II) complexes (M = Zn,Cd): The prominent role of π–π, C–H···π and anion–π interactions

We report the synthesis and X‐ray characterization of the N⁶‐benzyl‐N⁶‐methyladenine ligand (L) and three metal complexes, namely [Zn(HL)Cl₃]·H₂O ( 1 ), [Cd(HL)₂Cl₄] ( 2 ) and [H₂L]₂[Cd₃(μ‐L)₂(μ‐Cl)₄Cl₆]·3H₂O ( 3 ). Complex 1 consists of the 7H‐adenine tautomer protonated at N3 and coordinated to a tetrahedral Zn(II) metal centre through N9. The octahedral Cd(II) in complex 2 is N⁹‐coordinated to two N⁶‐benzyl‐N⁶‐methyladeninium ligands (7H‐tautomer protonated at N3) that occupy apical positions and four chlorido ligands form the basal plane. Compound 3 corresponds to a trinuclear Cd(II) complex, where the central Cd atom is six‐coordinated to two bridging μ‐L and four bridging μ‐Cl ligands. The other two Cd atoms are six‐coordinated to three terminal chlorido ligands, to two bridging μ‐Cl ligands and to the bridging μ‐L through N3. Essentially, the coordination patterns, degree of protonation and tautomeric forms of the nucleobase dominate the solid‐state architectures of 1 – 3 . Additionally, the hydrogen‐bonding interactions produced by the endocyclic N atoms and NH groups stabilize high‐dimensional‐order supramolecular assemblies. Moreover, energetically strong anion–π and lone pair (lp)–π interactions are important in constructing the final solid‐state architectures in 1 – 3 . We have studied the non‐covalent interactions energetically using density functional theory calculations and rationalized the interactions using molecular electrostatic potential surfaces and Bader's theory of atoms in molecules. We have particularly analysed cooperative lp–π and anion–π interactions in 1 and π⁺–π⁺ interactions in 3 .     

Magnetically separable CoFe2O4/CoxFey/activated carbon composites for Cd(II) removal from wastewater

CoFe₂O₄ and Co_x Fe_y were anchored into activated carbon (AC) to synthesize CoFe₂O₄/Co_x Fe_y /AC composites using the sol–gel method for Cd(II) adsorption from wastewater. The results indicated that CoFe₂O₄ and Co_x Fe_y nanoparticles existed in the pores of AC. The magnetic properties of CoFe₂O₄/Co_x Fe_y /AC indicated it could be separated and retrieved easily using an external magnet after Cd(II) adsorption. The effects of solution pH, temperature and initial Cd(II) concentration on the Cd(II) adsorption of AC and CoFe₂O₄/Co_x Fe_y /AC were investigated. The standard free energy, enthalpy change and entropy change were evaluated. The kinetic parameters of Langmuir and Freundlich isothermal equation were analyzed, and the Freundlich kinetic model was feasible for describing the Cd(II) adsorption process of CoFe₂O₄/Co_x Fe_y /AC composites.     

Fermionic representation of a symmetrically frustrated SU(3) model: Application to the Haldane-gap antiferromagnets

The one-dimensional spin 1 bilinear-biquadratic model is re-expressed in a symmetrically frustrated SU(3) model, which facilitates us to introduce a fermionic representation and related bond-operator mean-field theory. By analyzing the gap and the static spin susceptibility, we shows that this treatment can easily capture the commensurate and incommensurate Haldane gap phases.     

密闭高压消解–ICP–AES测定进口铜精矿中铅、镉、汞、砷

采用密闭高压消解法对样品进行消解,用电感耦合等离子体发射光谱法(ICP–AES)测定进口铜精矿中的铅、镉、砷、汞有害元素。铅、镉、砷、汞的工作曲线分别在0~10,0~1,0~4,0~0.6μg/mL范围内线性良好,线性相关系数大于0.999。各元素加标回收率均为91.0%~104.7%,相对标准偏差均小于3%(n=7)。将密闭高压消解法与电热板加热法和微波消解法进行了比对分析,结果显示,密闭高压消解–ICP–AES法适合用于铜精矿样品的消解与测定。     

Ba2Cd(B3O6)2: A Congruent‐Melting Compound with Isolated B3O6 Units

The single crystals of Ba₂Cd(B₃O₆)₂ were grown by the spontaneous crystallization method for the first time. They crystallize in the centrosymmetric trigonal space group R$\bar{3}$ with a = 7.143(3) Å, c = 17.405(16) Å, and Z = 3. The structure is characterized by isolated B₃O₆ units, and the Ba²⁺ and Cd²⁺ cations connect with B₃O₆ rings to form three dimensional structure. The TG/DSC and XRD results reveal that Ba₂Cd(B₃O₆)₂ melts congruently. First‐principles electronic structure calculation performed with the density functional theory (DFT) method shows that the calculated bandgaps are 4.66 eV, which is in good agreement with the UV/Vis/NIR experimental value 4.59 eV. The calculation shows that the Ba₂Cd(B₃O₆)₂ crystal has a large birefringence (Δn = 0.0875–0.0569 from 270 nm to 2600 nm), which demonstrates that Ba₂Cd(B₃O₆)₂ is a potential birefringence crystal.     

General Route to Synthesize Monodisperse Oxide (Hydroxide) Nanoparticles

Mono-dispersed oxide and hydroxide nanoparticles have been synthesized through the solvothermal process in alcohol-water mixtures. The products were characterized by powder x-ray diffraction (XRD) and scanning electron microscopy (SEM). Plate-like nanoparticles are obtained for Bi₂O_2.33, Fe₂O₃, and Cd(OH)₂, and spherical nanoparticles are obtained for SnO₂. The growth mechanism for the mono-dispersed nanoparticles has been preliminarily discussed.     

Stochastic resonance in a bistable system with time-delayed feedback and non-Gaussian noise

The phenomenon of stochastic resonance in a bistable system with time-delayed feedback driven by non-Gaussian noise is investigated. Combining the small time delay approximation, the path-integral approach and the unified colored noise approximation, a general approximate Fokker–Planck equation of a stochastic system is obtained. The effects of the parameter q indicating the departure from the Gaussian noise, the delay time τ  , and the correlation time τ₀${\tau }_0$ of the non-Gaussian noise on the quasi-steady-state probability distribution function (SPD) and the signal-to-noise ratio (SNR) are discussed. It is found that the number of peaks in SPD and the reentrant transition between one peak and two peaks and then to one peak again in the curve of SNR depends on the parameter q, the delay time τ  , and the noise correlation time τ₀${\tau }_0$.     

Clathrate formation and dissociation in vapor/water/ice/hydrate systems in SBA-15, sol-gel and CPG porous media, as probed by NMR relaxation, novel protocol NMR cryoporometry, neutron scattering and ab initio quantum-mechanical molecular dynamics simulation

The Gibbs-Thomson effect modifies the pressure and temperature at which clathrates occur, hence altering the depth at which they occur in the seabed. Nuclear magnetic resonance (NMR) measurements as a function of temperature are being conducted for water/ice/hydrate systems in a range of pore geometries, including templated SBA-15 silicas, controlled pore glasses and sol-gel silicas. Rotator-phase plastic ice is shown to be present in confined geometry, and bulk tetrahydrofuran hydrate is also shown to probably have a rotator phase. A novel NMR cryoporometry protocol, which probes both melting and freezing events while avoiding the usual problem of supercooling for the freezing event, has been developed. This enables a detailed probing of the system for a given pore size and geometry and the exploration of differences between hydrate formation and dissociation processes inside pores. These process differences have an important effect on the environment, as they impact on the ability of a marine hydrate system to re-form once warmed above a critical temperature. Ab initio quantum-mechanical molecular dynamics calculations are also being employed to probe the dynamics of liquids in pores at nanometric dimensions.     

三维分等级花状Cd0.8Zn0.2S的结构调控及其光催化CO2还原

近年来,光催化CO2还原被视为一种既能解决能源短缺又能减少温室气体,改善人类生存环境的绿色新型技术.然而,由于CO2气体的相对稳定性,构建高催化活性和高选择性的催化体系仍然面临着巨大挑战.锌硫镉固溶体作为一种廉价的固溶类材料,具有吸光范围适宜、化学性质稳定以及能带结构可调控等特点,在光催化还原CO2的方面表现出巨大的潜力.本文发展了一种简单的原位自组装法合成三维分等级花状结构的Cd0.8Zn0.2S,主要包括Cd^2+和Zn^2+离子在含硫氛围下自组装成核状前体,然后以柠檬酸钠作为形貌诱导剂进一步组装生长,同时控制Cd2+/Zn2+摩尔比和反应时间以实现三维分等级花状Cd0.8Zn0.2S的合成.结果表明,三维分等级花状结构的Cd0.8Zn0.2S在光催化还原CO2的过程中表现出优异的催化活性和稳定性.其中,在光照3 h后,CO产量达到41.4μmol g^?1,大约是相同光照条件下Cd0.8Zn0.2S纳米颗粒的三倍(14.7μmol g^?1).此外,三维分等级花状结构的Cd0.8Zn0.2S在光催化过程中展现出对光催化产物CO的较高选择性(89.9%),其中在没有任何牺牲剂或共催化剂作用下的TON为39.6.太赫兹时域光谱(THz-TDS)表明,这种三维分等级花状结构的Cd0.8Zn0.2S相较于Cd0.8Zn0.2S纳米颗粒更有利于对光的吸收,从而提高对光的有效利用率.原位漫反射傅立叶变化红外光谱表征分析揭示了三维分等级花状结构的Cd0.8Zn0.2S在光催化过程中表面吸附物质以及光催化还原中间体的存在及转化.通过实验数据和理论机理预测表明,该种三维分等级花状结构的Cd0.8Zn0.2S具有较高的电流密度和较好的载流子传输能力.基于这种三维的花状结构,使得Cd0.8Zn0.2S具有较大的比表面积和吸附位点,进一步提升体系的CO2吸附性能和光生电子的转移效率,从而有效提高光催化CO2还原的活性.