Synthesis and properties of NiSn colloids using different metal ratios by CLD

Bimetallic colloidal dispersions of Ni–Sn were prepared by simultaneous co-condensation with organic solvents at 77 K using the chemical liquid deposition (CLD) method. The atoms in a 1:1, 2:1, 3:1, 1:2 and 1:3 ratios were produced by resistive heating and were reacted with 2-propanol, 2-methoxyethanol, ethanol and acetone to produce colloids. The bimetallic films and solids were obtained by evaporation under vacuum at room temperature. The colloids and solids were characterized by several studies, including the stability at room temperature, electrophoresis, ultraviolet-visible spectrophotometry, transmission electron microscopy (TEM), electron diffraction, conductivity, nergy dispersive X-ray analysis, electrophoretic measurements, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and magnetic properties. TEM studies show a size distribution between 6 and 14 nm, depending of the solvent and Ni:Sn ratio. We can observe a high stability for the colloidal dispersion with different solvents (>2 weeks); this is due mainly to the solvation capacity and polarity of the organic molecules. Electrophoretic measurements revealed that the particles are weakly positively charged with a greater Ni percentage. Electron diffraction analysis for the metallic colloids shows the presence of bimetallic compounds as NiSn, Ni₃Sn, Ni₃Sn₄ and tin oxides. XPS analysis was used for the study of the Ni–Sn solid composition, where it was determined that the Ni atoms could be as Ni⁰ and Ni²⁺. The bond energy difference in both species were 0.8 eV; on the other side, Sn atoms showed two peaks, the first associated with Sn⁰ atoms and the second attributed to oxidized species like SnO_x. The conductivity studies showed that when the metal is changed, the electric conductivity properties change too and are associated with the particle size increasing.