Synthesis of Nd3+-doped α-γ bismuth oxide homojunction nanoparticles: a smart multifunctional solar photocatalyst

Multifunctional Nd³⁺-doped α-γ bismuth oxide (Bi₂O₃) homojunction nanoparticles were successfully synthesized through metamorphosis from the α-β Bi₂O₃ homojunction via a low temperature solvothermal method. The structural and optical properties were thoroughly characterized by different methods. NIR reflectance spectroscopy revealed that 2 wt% Nd³⁺-doped Bi₂O₃ exhibited about 90% NIR reflectance. The CIE-L*a*b* 1976 colour analysis showed a b* value of 50.72, surpassing that of the commercially available yellow pigment Zircon Yellow, which has a b* value of 43.3. The transformation from α-β to α-γ Bi₂O₃ was controlled by dopant concentration, with the band gap decreasing as the Nd³⁺ content increases. The synthesized materials demonstrated efficient photocatalytic activity, degrading model pollutant methylene blue and the antibiotic ceftriaxone sodium under sunlight. This was investigated using UV-visible spectroscopy and LC-MS. The α-γ Bi₂O₃ homojunction presents a promising new direction for eco-friendly cool yellow pigments that degrade organic pollutants under sunlight showing upconversion luminescence and antibacterial activity.