Coverage dependence of neopentane trapping dynamics on Pt(111)

Adsorption probabilities for neopentane on Pt(111) were measured directly using supersonic molecular-beam techniques at coverages ranging from zero to monolayer saturation, incident translational energies between 18 and 110 kJ mol⁻¹ and incident angles between 0° and 60° at a surface temperature of 105 K. The adsorption probability was found to increase with coverage up to near monolayer saturation at all incident translational energies and incident angles. The coverage dependence of the adsorption probability predicted by a modified Kisliuk model with enhanced trapping into the second layer exhibits good quantitative agreement with the experimental values. The angular dependence of the adsorption probability decreases with increasing coverage, suggesting that the effective corrugation of the gas–surface interaction potential increases with the adsorbate coverage. The initial adsorption probability into the second layer onto the covered surface decreases from 0.95 to 0.75 with increasing energy over the energy range studied, and exhibits total energy scaling. A comparison with second-layer trapping data of simpler molecules onto covered Pt(111) indicates that the structural complexity of adsorbed neopentane molecules facilitates collisional energy transfer during adsorption.     

Separation of polypeptide antibiotics by reversed-phase high-performance liquid chromatography

Summary The influence of different reversed-phase packings and the addition of acidic modifiers to the mobile phase was observed on the separation of basic and neutral polypeptide antibiotics by gradient elution. A dependence of pore size, coverage, reaction type and endcapping of the packings was not observed. Nevertheless, not all reversed-phase packings were suitable for the separation of polypeptides, especially of basic molecules. The addition of phosphoric or perchloric acid to the mobile phase prevented adsorption of the basic polypeptide antibiotics on the stationary phase.     

Thermodynamics of vapour adsorption on heterogeneous microporous adsorbents

Fundamental thermodynamic functions have been derived for equations of adsorption isotherms including structural heterogeneity connected with micropore dimensions. Good agreement has been achieved between values of the differential molar enthalpy of adsorption and values of the isosteric adsorption heats obtained experimentally.     

Adsorption and biotransformation of 17β-estradiol in biological activated carbon adsorbers

As the first systematic study dealing with the adsorption of estrogens by granular activated carbon (GAC), the removal behavior of 17β-estradiol (E2) and its biotransformation product of estrone (E1) in fixed GAC columns was examined using four biological activated carbon (BAC) columns (BAC-1～BAC-4) generated by coating four GAC columns with detached microorganisms from the riverbed sediment of a representative drinking river water source containing lower content of natural organic matter (NOM). For comparison, parallel adsorption experiments were also performed using another four GAC columns (GAC-1～ GAC-4) packed by strictly following the configurations of four BAC columns. Adsorption experimental results obtained by intermittently spiking E2 over a total running period about 350 days into the river water mixed with or without a peaty water containing higher content of NOM showed that E2 was readily removed by adsorption and the combined adsorption/biodegradation. The vertical profiles of E2 and E1, which have great significance for better understanding and optimization of the adsorption process for removal of human estrogens, were also obtained.     

Thermodynamics of Surface Tension: Application to Electrolyte Solutions

In this contribution to the special issue of the Journal of Statistical Physics dedicated to Michael Fisher on his 70th birthday, I shall review two thermodynamically distinct routes for obtaining the interfacial tension of liquid-vapor interfaces in mixtures. A specific application to the calculation of excess surface tension of aqueous electrolyte solutions will be presented.     

DFT study of the water/MgO(1 0 0) interface in acidic and basic media

Periodic-DFT has been used to study the acid-base properties of MgO(1 0 0) layers interconnected with an ice filling. The insertion of HCl by substitution of one water molecule shows that all the protons are adsorbed on the surface oxygen atoms forming hydroxyl groups; the Cl⁻ ions are weakly bound to surface cations, generating a monolayer with the adsorbed water molecules. For the insertion of NaOH also by substitution of one water molecule, it is found that OH⁻ ions remain in solution close to the Na⁺ ions, forming ion pairs or chains. Depending on the number of water molecules present, the sodium ions are bi-, tri- or tetra-coordinated. Finally, some aspects concerning corrosion have been highlighted.     

Ab initio calculations and dynamical properties of the Se:InP(1 1 0) and Te:InP(1 1 0)

We present results of ab initio theoretical investigations of the structural and dynamical properties of the Se:InP(1 1 0) and Te:InP(1 1 0) surfaces, by employing the plane wave pseudopotential method, the local density approximation of the density functional theory, and a linear response scheme. For both adsorbates we have used the so-called exchange geometry (the chalcogen atoms replacing P in the top two atomic layers). A detailed discussion is provided of the relaxed surface geometry and phonon dispersion curves along two principal symmetry directions. It is found that the adsorption of Se (or Te) atoms on InP(1 1 0) leads to phonon modes in the acoustic-optical gap region for bulk InP. The characteristic atomic displacement patterns of selected phonon modes on these surfaces have been compared and contrasted with those on the clean InP(1 1 0) surface.     

Needles and clusters of zinc porphyrin molecules on mica

Molecular monolayers of zinc porphyrins deposited from a liquid solution on mica substrates have been characterised using atomic force microscopy (AFM). At room temperature, needle-shaped single layer porphyrin islands are formed due to an anisotropic growth rate. The average island size depends on the concentration of the porphyrin solution, but the length to width aspect ratio is rather independent of the island size. Annealing the porphyrin monolayers to 450 K leads to the reduction of the size of the monolayer islands in two different ways depending on the heating rate. With slow heating rate, the island size was found to shrink by losing molecules from the edge of the island. With high heating rate, nanoscale molecular clusters were found to form.     

牛红细胞铜锌超氧化物歧化酶（BESOD）在汞电极表面吸附行为的研究

牛红细胞铜锌超氧化物歧化酶（ＢＥＳＯＤ）在汞电极表面吸附行为的研究钱雯，孟庆国，罗勤慧，沈孟长（南京大学配位化学研究所，配位化学国家重点实验室南京，２１００９３）关键词铜锌超氧化物歧化酶，吸附，循环伏安，双阶跃计时电量超氧化物歧化酶是超氧离子（·Ｏ）...     

纤维素基磁性聚偕胺肟树脂的研究：树脂对氯钯酸的吸附行为

H2PdCl4在纤维素基磁性聚偕胺肟树脂上的吸附是一个复杂的过程。在生成AO－H2pDcL4络合物时伴随着外加酸的竞争吸附、物理吸附和氧化还原作用等副反应。物理扩散和化学吸附均非吸附速度的控制阶段，表现为快的吸附速度，接触5分钟时，讨论了吸附机理。