Modification of the Electrolyte/Electrode Interface for the Template-free Electrochemical Synthesis of Metal Nanowires from Ionic Liquids.

In electrochemistry, the electrode/electrolyte interface (EEI) governs the charge/mass-transfer processes and controls the nucleation/growth phenomena. The EEI in ionic liquids (ILs) can be controlled by changing the cation/anion of the IL, salt concentration, electrode potential, and temperature. Here, we show that adding a dopant salt leads to the deposition of nanowires. To illustrate, zinc nanowires were electrodeposited from ZnCl2/1-butyl-1-methylpyrrolidinium trifluoromethylsulfonate in the presence of GaCl3 as a dopant salt. The choice of Zn salt and its ratio to GaCl3 were found to be crucial for Zn nanowires formation. AFM studies revealed that the solvation structure of Au(111)/IL changes significantly in the presence of GaCl3 and ZnCl2. Chronoamperometry showed changes in the nucleation/growth process, consequently leading to the formation of nanowires. A similar approach was adopted to synthesize Sn nanowires. Thus, modification of the EEI by adding a dopant to ILs can be a viable method to obtain nanowires.

Crystallization dynamics and interface stability of strontium titanate thin films on silicon.

Different physical vapor deposition methods have been used to fabricate strontium titanate thin films. Within the binary phase diagram of SrO and TiO2 the stoichiometry ranges from Ti rich to Sr rich, respectively. The crystallization of these amorphous SrTiO3 layers is investigated by in situ grazing-incidence X-ray diffraction using synchrotron radiation. The crystallization dynamics and evolution of the lattice constants as well as crystallite sizes of the SrTiO3 layers were determined for temperatures up to 1223 K under atmospheric conditions applying different heating rates. At approximately 473 K, crystallization of perovskite-type SrTiO3 is initiated for Sr-rich electron beam evaporated layers, whereas Sr-depleted sputter-deposited thin films crystallize at 739 K. During annealing, a significant diffusion of Si from the substrate into the SrTiO3 layers occurs in the case of Sr-rich composition. This leads to the formation of secondary silicate phases which are observed by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy.

Silver nanoparticles/montmorillonite composites prepared using nitrating reagent at water and glycerol.

Three procedures (P) were applied to prepare silver nanoparticles on natural Ca-montmorillonite (MT). The intercalation of the montmorillonite with silver nitrate in aqueous solution (P1), the intercalation of the montmorillonite with silver nitrate in glycerol (P2) and the successive combination of both P1 and P2 methods resulted to P3 method. X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and Fourier Transform Infrared (FTIR) spectroscopy and the molecular modeling were employed to characterize silver nanoparticles and montmorillonite nanocomposite. The P1 produced MT-1 composite with 2.3 wt% Ag and the partially collapsed layered structure. Nanoparticles of silver larger than 20 nm with a lot of planar defects were randomly distributed on the MT-1 surface; nanoparticles smaller than 20 nm were oriented to the montmorillonite substrate. The MT-2 composite from P2 contained only 1 wt% of Ag. The molecular simulation model of MT-2 showed the interlayer space with the exchangeable cations and metallic silver atoms arrangement within the glycerol bilayer. The P3 produced composite MT-3 that contained 2.4 wt% Ag. The nanoparticles > 20 nm size had a well-defined geometry, very small nanoparticles were amorphous. The modeled structure showed the exchangeable cations, Ag+ and Ag0 located close to the silicate layers and monolayer of glycerol molecules in the interlayer space.