Ag Transition Metal Research Articles

Induced π–complexation properties of smectites impregnated by Ni, Cu and Ag transition metals: The highly efficient styrene uptake

Two natural smectite minerals (montmorillonite and beidellite) differing in structural charge location were impregnated with varying amounts of transition metals: Ni(II), Cu(I) or Ag(I). The modification aimed to increase the affinity of the minerals towards styrene vapors. The structure, texture, chemical composition and surface chemistry of the materials were studied by XRD, FTIR, Raman, N2 adsorption/desorption, XRF and XPS. The experiments examined the influence of the starting smectite and the type of introduced metal on styrene adsorption efficiency. The styrene uptake mechanisms were investigated through solid state analysis and supported by DFT calculations. The study demonstrated that the small content of introduced metals (<2% wt.) substantially increased styrene uptake (∼200–350% wt.) surpassing values reported for surfactant-intercalated smectites (∼40–80% wt.) and activated carbons (∼30% wt.). This enhancement was attributed to the π-complexation between dispersed d-block metals and π-electron-rich styrene molecules, subsequently leading to polystyrene formation. The DFT calculations were consistent with experimental findings, indicating a higher affinity of the raw beidellite towards styrene than the raw montmorillonite connected to the charge location. Moreover, the observed trends in calculated adsorption energies and lengths of weak hydrogen bonds allowed to explain a significant adsorption increase observed for the Ni- and Cu-impregnated montmorillonite-based materials.

Synthesis and thermoluminescence characterization of lithium tetraborate (Li2B4O7) doped with copper and silver metals

In this paper, dosimetric phosphor; lithium tetraborate (Li2B4O7) which has been synthesized and doped with Cu, Ag transition metals using two different synthesis methods (solution-assisted method and microwave-assisted method) and thermoluminescence characteristics of synthesized lithium tetraborate are analyzed. Synthesized Li2B4O7: Cu and Li2B4O7: Cu, Ag phosphors were characterized with X-ray Diffraction, Transmission Electron Microscopy, Scanning Electron Microscopy, and Differential Thermal Analysis to determine structural and morphological properties. Thermoluminescence (TL) properties of the lithium tetraborate samples, doped with varied amounts of copper in the range 0.02 wt% - 0.1 wt% and constant amount of silver (0.04 wt%) was added as co-dopant, were studied. TL results demonstrate that 0.08% Cu and 0.04% Ag doped lithium tetraborate synthesized with solution-assisted method has the highest dosimetric sensitivity. Kinetic parameters (trap depth and order of kinetic) of this sample were calculated using peak shape, variable heating rate and computer glow curve deconvolution methods.

First-principles calculations on sulfur interacting with ternary Pd–Ag-transition metal alloy membrane alloys

Pd-alloy membranes are promising for use in fossil-fueled power plants with integrated carbon capture, but for some applications this requires resistance to performance degradation in the presence of sulfur containing gases like H2S. By use of atomistic modeling based on density functional theory, the role of transition metals (TMs) in ternary Pd–Ag–TM alloys was in the current article used to identify new Pd-alloys with potentially less performance degradation in contact with H2S. A number of slab models were created, giving a wide and representative span of compositions of the two upper atomic layers of the Pd-alloys. All TMs in the 4th, 5th and 6th rows of the periodic table were included, as well as some of the poor metals. By comparing energies of pure alloy slabs, the tendency of different TMs to segregate to the surface in vacuum was quantified; this turned out to depend only weakly on the presence of silver. In order for the TM to be of any benefit for the surface properties of the membrane, the segregation energy towards the bulk should not be too large. The free energy of different compositions was then calculated for two systems: a clean surface in a gas mixture of H2 containing a fraction of 20×10–6 H2S, and a slab with adsorbed sulfur in pure H2 atmosphere. This was used to calculate a typical release temperature for sulfur from the surface and a maximal H2S concentration before the membrane surface can be expected to be blocked by adsorbed S. When using a tentative threshold for the segregation energy (0.2eV) and the release temperature (600°C), we arrived at the following list of potential TM additives to sulfur-resistant Pd–Ag membranes: Cu, Zn, Ga, Cd, In, Sn, Pt, Au, Hg, Tl, Pb, and Bi.

Linear free energy relationships from collision-activated dissociation spectra: the electrospray mass spectra of transition metal macrocyclic complexes

Linear free energy relationships (LFER) from collision-activated dissociations (CADs) have been uncovered from electrospray mass spectra of dinucleating macrocyclic ligands involving Cu and Ag transition metal ions. In particular, the electrospray mass spectral method for the determination of stability constants has been explored. The LFERs are interpreted in terms of two collision models, both of which underlie a broader class of investigations.