Enhanced visible light photocatalytic activity of Cu-doped SnO2 quantum dots by solution combustion synthesis

Copper (Cu)-doped tin oxide (SnO2) quantum dots (QDs) were prepared using energy-efficient solution combustion synthesis. The synthesized nanoparticles were characterized by XRD, TEM, XPS, UV-Vis DRS, and FT-IR. The X-ray diffraction (XRD) pattern shows that the QDs have tetragonal rutile-like structure. HR-TEM shows modification in the growth inhibition of the SnO2 lattice parameters with Cu doping. When increasing the Cu concentration, the optical band gap energy of SnO2 decreases. X-ray photoelectron spectroscopy (XPS) reveals the presence of copper and tin as Cu2+ and Sn4+, respectively. Fourier transform infrared (FT-IR) spectroscopy confirmed the fundamental vibrational modes of SnO2. The photocatalytic degradation of methyl orange dye was measured under visible light irradiation using the QDs as catalysts. The QDs with 0.03 mol % Cu doping showed the highest photocatalytic performance with 99% degradation of the dye under visible light within 180 min, which means they could be used to treat polluted water.