Se rods decorated with SnO₂ nanoparticles have been synthesized via a facile hydrothermal approach to bridge the gap between ultraviolet-only and visible-only photocatalysis and to enhance reactive oxygen species generation under visible illumination. Structural and morphological analyses using X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy have confirmed the coexistence of cassiterite SnO₂ particles intimately interfaced with trigonal selenium rods. Diffuse-reflectance spectroscopy revealed a long absorption tail extending into the 400–550 nm range. Under 450 nm sample illumination, the composite produced singlet oxygen in higher yields than either bare SnO₂ or Se, as evidenced by the indocyanine green assay. The system alone does not produce free radicals, as shown by the terephthalic acid test; however, the addition of rhodamine B acts as an effective sensitizer, enabling hydroxyl radical generation. Photodegradation tests using rhodamine B have shown that the SnO₂–Se system outperforms both its single components, Se and SnO₂, as a catalyst. The synergistic interplay underscores the potential of SnO₂–Se heterostructures in photochemical applications under visible light.

SnO2–Se heterostructures have been synthesized via a facile hydrothermal approach to bridge the gap between ultraviolet‐only and visible‐only photocatalysis, and to enhance reactive oxygen species generation under visible illumination. Structural and morphological analyses using X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy have confirmed the coexistence of cassiterite SnO2 particles intimately interfaced with trigonal selenium rods. Diffuse-reflectance spectroscopy revealed a long absorption tail extending into the 400–550 nm range. Under 450 nm sample illumination, the composite produced singlet oxygen in higher yields than either bare SnO2 or Se, as evidenced by the indocyanine green assay. The system does not produce free radicals, as demonstrated by the terephthalic acid test; however, the addition of rhodamine B works as an effective sensitizer to generate hydroxyl radicals. Photodegradation tests using rhodamine B have shown that the SnO2-Se heterostructure outperforms both its single components, Se and SnO2, as a catalyst. The synergistic interplay underscores the potential of SnO2–Se heterostructures in photochemical applications under visible light.