A novel investigation of tin-doped ferrihydrite nanoparticles

Tin-doped ferrihydrite was synthesized and characterized with powder X-ray diffraction and ⁵⁷Fe and ¹¹⁹Sn Mössbauer spectroscopy to obtain diagnostic and structural information. Samples were prepared with doping concentrations (molar percentages) of 0, 10, 25, 40, 50, 60, 75, and 90% tin. As Sn concentration increases, the 110 reflection plane of ferrihydrite shifts to higher d-values, while the 300 plane d-values increase, reach a maximum and then sharply drop. The δ (isomer shift) and Δ (quadrupole splitting) values for ⁵⁷Fe Mössbauer spectra increase, while the Γ (line width) values stay constant. In ¹¹⁹Sn Mössbauer spectra, δ values decrease with increasing tin substitution while Δ and Γ values increase. After 50% Sn has been substituted, the ferrihydrite becomes oversaturated with surface tin and a secondary tin structure is proposed to develop.