Synthesis of thiol-functionalized MCM-41 mesoporous silicas and its application in Cu(II), Pb(II), Ag(I), and Cr(III) removal

Thiol-functionalized MCM-41 mesoporous silicas were synthesized via evaporation-induced self-assembly. The mesoporous silicas obtained were characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption analysis, Fourier transform infrared spectroscopy (FTIR), elemental analysis (EA), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The products were used as adsorbents to remove heavy metal ions from water. The mesoporous silicas (adsorbent A) with high pore diameter (centered at 5.27 nm) exhibited the largest adsorption capacity, with a BET surface area of 421.9 m² g^?1 and pore volume of 0.556 cm³ g^?1. Different anions influenced the adsorption of Cu(II) in the order NO₃ ^? < OAc^? < SO₄ ^2? < CO₃ ^2? < Cit^? < Cl^?. Analysis of adsorption isotherms showed that Cu²⁺, Pb²⁺, Ag⁺, and Cr³⁺ adsorption fit the Redlich–Peterson nonlinear model. The mesoporous silicas synthesized in the work can be used as adsorbents to remove heavy metal ions from water effectively. The removal rate was high, and the adsorbent could be regenerated by acid treatment without changing its properties.     

Infrared Studies on the Complexes of Zn(II), Cd(II), Hg(II), Pb(II), Cu(I) and Ag(I) with 5-Benzylthio-1,2,4.-triazole

Zn(II), Cd(II), Hg(II), Pb(II), Cu(I) and Ag(I) complexes of 5-benzylthio-1,2,4-triazole (BTT) have been prepared and characterised on the basis of analytical and IR data. Hg(II), Cd(II), Zn(II), and Pb(II) complexes are assigned tetrahedral structure with polymeric intermolecular linkages through S and N atoms while Ag(I) and Cu(I) are proposed to have polymeric linear structure     

Theoretical oscillator strengths for some transitions in Si(II), Ge(II), Sn(II) and Pb(II) spectra

Calculations are reported of non-relativistic and relativistic oscillator strengths for the principal, sharp and diffuse series as well as some lifetimes in the spectra of singly-ionized silicon, germanium, tin and lead. The radial integrals were computed by employing the wave functions obtained from a semiempirical approach which included exchange effects (the semiempirical X$\text{α}$ method). Good agreement was obtained with available experimental and theoretical data. A comparison between non-relativistic and relativistic oscillator strengths confirms the importance of the spin-orbit interaction of the optical electron, as well as other relativistic effects for the oscillator strengths, even for the spectra of moderately heavy ions. Some systematic trends in the calculated oscillator strengths and line-strength ratios were investigated along the spectral series, as well as along the sequence of homologous ions.     

光度法研究聚乙二醇-硫酸铵-邻苯三酚红体系中铋(Ⅲ), 铁(Ⅲ), 铜(Ⅱ), 镍(Ⅱ), 钴(Ⅱ), 铅(Ⅱ)的萃取分离

本文研究了在聚乙二醇(PEG)-硫酸铵[(NH_4)_2SO_4]-邻苯三酚红(PR)体系中Bi(Ⅲ),Fe(Ⅲ),Cu(Ⅱ),Ni(Ⅱ),Co(Ⅱ),Pb(Ⅱ)的萃取行为。实验结果表明,Bi(Ⅲ)在pH3.5～6.5及Fe(Ⅲ)在pH4.0～7.0范围内可以被PEG相几乎完全萃取,而Cu(Ⅱ),Co(Ⅱ)在pH1.0～7.0,Pb(Ⅱ)在pH2.0～7.0,Ni(Ⅱ)在pH1.0～4.5则不被萃取。从而实现了将Bi(Ⅲ)(pH3.5),Fe(Ⅲ)(pH5.0)与Cu(Ⅱ),Co(Ⅱ),Pb(Ⅱ),Ni(Ⅱ)混合离子的定量分离。同时探讨了PEG相的萃取机理。     

Growth of metallic nanowires on anisotropic Si substrates: Pb on vicinal Si(0 0 1), Si(7 5 5), Si(5 3 3), and Si(1 1 0)

The spontaneous formation of mesoscopic Pb-wires, on 4° off-cut Si(0 0 1) vicinal surface, Si(7 5 5), Si(5 3 3), and Si(1 1 0) substrates was studied by low-energy electron microscopy. Before the deposition of Pb the substrates were modified by predeposition of a submonolayer amount of Au followed by annealing. The Au-induced reconstruction creates quasi-one-dimensional facets and superstructures. Their width ranged from several hundred nm in the case of the vicinal Si(0 0 1) down to atomic scale size, for the Si(1 1 0) surface. The best-developed arrays of parallel aligned mesoscopic wires were obtained during the deposition of Pb on substrates cooled slightly below room temperature. Wires with length to width ratio reaching 130 were produced on the Si(7 5 5) and the Si(5 3 3) substrates. The width of these nanowires was uniform over the whole substrate and was about 60 nm. The driving forces for the formation of the mesoscopic wires are the anisotropic strain due to the large misfit between the Pb and the Si lattice and one-dimensional diffusion of Pb.     

Potentiodynamic desorption spectra of metallic monolayers of Cu,Bi, Pb,Tl, and Sb adsorbed at (111), (100), and (110) planes of gold electrodes

The formation of metallic adsorption layers was studied in solutions of Cu²⁺, Bi³⁺, Pb²⁺, Tl⁺ and Sb³⁺ at (111), (100) and (110) planes of gold single crystal electrodes. Potentiodynamic desorption spectra were recorded with a sweep rate of 20 mV s^?1 for all systems. Characteristic peak structures were obtained which depend strongly on the nature of the adsorbate as well as on the substrate orientation. The half width of the peaks indicates attraction and repulsion respectively for various systems. In most systems more than one peak was observed. This is explained by the formation of various ordered structures. At low coverages peak charge data obtained by integration of current/time curves yield surface concentrations which fit those of ordered structures well, e.g. c(2×2) on (100) or $\text{p(}\text{3}\text{×}\text{3}\text{)}$ R 30° on (111). The adsorption behaviour of the (110) plane is similar in all systems because atomic chains seem to be generally stable. Near the equilibrium potential of the correspondent metal electrode, ?_r = 0, a “mono-molecular” adsorption layer was found for Cu²⁺, Pb²⁺ and Bi³⁺. In the case of the small copper atom, a 1:1 adsorption was found for all planes. Larger atoms like bismuth and lead form epitactic layers at low coverages; at high coverages they form close-packed monolayers with surface concentrations independent of the substrate structure but decreasing with increasing adsorbate radius. The coulometric data for antimony and thallium are not so conclusive. Measurements with various sweep rates show that the adsorption reaction is a slow potential dependent process in various systems. The underpotential/work function correlation of Kolb, Gerischer and Przasnyski is discussed with respect to these experiments. It follows that this concept developed for polycrystalline electrodes is qualitatively valid for (110), but not clearly so for (100) and (111).     

Axialvector tetraquark candidates for Z_c(3900), Z_c(4020),Z_c(4430), and Z_c(4600)

We construct the axialvector and tensor current operators to systematically investigate the ground and first radially excited tetraquark states with quantum numbers J~(PC)= 1~(+-)using the QCD sum rules. We observe one axialvector tetraquark candidate for Z_c(3900) and Z_c(4430), two axialvector tetraquark candidates for the Z_c(4020), and three axialvector tetraquark candidates for Z_c(4600).     

A study of the reactions208Pb(d,d)208Pb and208Pb(d,p)209Pb at energies above and below the Coulomb barrier

The reactions²⁰⁸Pb(d, d)²⁰⁸Pb and²⁰⁸Pb(d, p)²⁰⁹Pb have been studied in the energy region from below to above the Coulomb barrier. An optical-model analysis of the elastic scattering results has been performed to obtain parameters for a DWBA analysis. Distorted wave calculations for the direct transitions leading to single-particle states in²⁰⁹Pb have been used to extract spectroscopic factors. Only two deuteron potential sets give a good account of the stripping data throughout the energy region studied.     

Surface phonons on Pb(111)

We present an ab initio study of the lattice dynamics of the Pb(111) surface. The calculations were carried out within the density-functional theory using a linear response approach in the mixed-basis pseudopotential representation. We observe a rich spectrum of surface localized modes, and make a detailed assignment to measured modes in a recent helium-atom scattering experiment. We find that the inclusion of spin–orbit coupling considerably softens the phonon spectrum of the surface, thereby improving the agreement with experiment significantly.     

The 208Pb(α, 3He)209Pb reaction at 58 MeV

The ²⁰⁸Pb(α, ³He)²⁰⁹Pb reaction at 58 MeV has been used to search for high-spin states in ²⁰⁹Pb. Only three levels are excited with appreciable intensity: the ground state $\text{(2}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)}$ and levels at $\text{0.781 (}\text{li}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}\text{)}\text{and}\text{1.426}\text{MeV}\text{(}\text{lj}{}_{\mathrm{<mtext>15</mtext><mtext>2</mtext>}}\text{)}$. The angular distributions for these levels have been measured and analyzed using standard DWBA calculations to obtain spectroscopic strengths. The ²⁰⁸Pb(α, α) elastic scattering was measured and optical parameters deduced from the data. A normalization value N = 50 yields spectroscopic values which are close to the values measured in the (d, p) reaction. The (α, ³He) reaction should easily pick out any appreciable components of the $\text{j}{}_{\mathrm{<mtext>15</mtext><mtext>2</mtext>}}$ shell model state, which weak-coupling calculations predict should be fragmented. However only three weak transitions previously seen in a (d, p) experiment are observed.     

The PbPb collision

The reaction ²⁰⁸Pb on ²⁰⁸Pb was studied at bombarding energies of 7.0 and 7.57 MeV/u. One-particle inclusive measurements using a large-area position-sensitive ionisation chamber delivered the kinetic energy, charge and scattering angle of the reaction products. A precise calibration of the stopping power for very heavy ions in the detector gas was performed. The measured Wilczynski diagrams show, for increasing loss of kinetic energy, an increase of the mean scattering angle. It is attributed to the dominance of the repulsive Coulomb forces with respect to the attractive nuclear forces. The element distribution for the ²⁰⁸Pb on ²³⁸U reaction at 7.5 MeV/u was also measured and compared to the PbPb and UU reactions. Fission probabilities are derived as a function of charge and total kinetic energy loss. The most striking result is seen in the σ_z² versus TKEL correlation: the average rate of energy loss per nucleon exchange is abnormally large. It is shown that this behaviour is associated with the double magic closed shell character of the colliding nuclei. Nuclear structure information is extracted through a simple parametrisation.     

Two-Step Oxidation of Pb（111） Surfaces

We report on a two-step method for oxidation of Pb（111） surfaces, which consists of low temperature （90K） adsorption of 02 and subsequent annealing to room temperature. In situ scanning tunnelling microscopy observation reveals that oxidation of Pb（111） can occur effectively by this method, while direct room temperature adsorption results in no oxidation. Temperature-dependent adsorption behaviour suggests the existence of a precursor state for 02 adsorption on Pb（111） surfaces and can explain the oxidation-resistance of clean Pb（111） surface at room temperature.