Optical properties and photocatalytic activates of Sn doped Sb2O3/Sb2O5 nanostructured thin films for treatment of wastewater containing organic pollutants

This study investigated the influence of Sn doping ratios (0, 10, and 25 wt.%) on the morphological, structural, optical, and photocatalytic properties of Sb 2 O 3 /Sb 2 O 5 nanostructured thin films. EDX confirmed that the estimated Sn atomic percentages matched the precursor ratios. XRD analysis revealed that both undoped and 10 wt.% Sn doped films exhibited mixed crystallographic phases of orthorhombic Sb 2 O 3 and cubic Sb 2 O 5 , though Sn doping lowered peak intensities. At 25 wt.% Sn doping, an additional orthorhombic SnO 2 phase appeared. Morphologically, undoped films consisted of smooth nano-sheets, which reduced and agglomerated into rounded nano-grains upon Sn doping. Optically, Sn doping decreased transmittance and increased reflectance. The optical band gaps narrowed from 3.95 eV (undoped) to 3.86 eV and 3.76 eV for 10 wt.% and 25 wt.% Sn doping, respectively. Furthermore, refractive indices increased substantially, and emission peaks showed notable intensity quenching with slight shifts to lower wavelengths. Photocatalytically, the 10 wt.% Sn-doped film achieved a 58.8% degradation efficiency against methylene blue (MB) after 300 min of UV illumination. Trapping experiments indicated that superoxide radicals (O 2 -● ), hydroxyl radicals (OH ● ), and photogenerated holes (h + ) drove the degradation, with O 2 -● being the dominant active species. Importantly, the 10 wt.% Sn-doped film demonstrated excellent reusability and stability over three consecutive cycles, making it a highly promising photocatalyst for degrading organic pollutants.