Iron addition induced tunable band gap and tetravalent Fe ion in hydrothermally prepared SnO2 nanocrystals: Application in photocatalysis

• High iron solubility within SnO2 host was reached using the hydrothermal method.
• The experimental results reveals the substitution of Sn4+ by iron ions.
• The presence of Fe4+ ions in Fe-doped SnO2 was detected through Mössbauer spectroscopy.
• A shoulder attributed to the d–d transition 6A1g(G) → 4T2g(G) of the Fe3+ ion was detected in the absorbance spectra.
• The Fe addition enhances the SnO2 photocatalytic efficiency.

Highly iron-doped tin dioxide nanoparticles (Sn1−xFexO2 NPs), with x varying from 0 to 0.2, were prepared by simple hydrothermal method. X-ray diffraction (XRD) patterns indicate that Sn1−xFexO2 NPs crystallize in the tetragonal rutile-like structure. High-resolution transmission electron microscopy (HRTEM) observations did not show any modification of the SnO2 lattice parameters with Fe addition. Mössbauer spectroscopy indicated Sn4+ substitution by Fe3+ and Fe4+ ions. It was found that iron addition induced high tunable band gap of SnO2 NPs. Photoluminescence (PL) spectra evidenced an improvement of SnO2 crystallinity after Fe introduction. All the results are consistent with the fact that Fe is strongly soluble in SnO2 host. Finally, the photocatalytic efficiency of Sn1-xFexO2 NPs was examined for the degradation of rhodamine B in aqueous solution under visible light irradiation. We show that Fe4+ and Fe3+ ions play a key role in the improvement of the photocatalytic efficiency.

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