Degradation in the presence of visible light is essential for successfully removing dyes from industrial wastewater, which is pivotal for environmental and ecological safety. In recent years, photocatalysis has emerged as a prominent technology for wastewater treatment. This study aimed to improve the photocatalytic efficiency of synthesized TiO2 quantum dots (QDs) under visible light by barium (Ba) doping. For this, different weight ratios (2% and 4%) of Ba-doped TiO2 QDs were synthesized under ambient conditions via a simple and modified chemical co-precipitation approach. The QD crystal structure, functional groups, optical features, charge-carrier recombination, morphological properties, interlayer spacing, and presence of dopants were analyzed. The results showed that for 4% Ba-doped TiO2, the effective photocatalytic activity in the degradation process of methylene blue (MB) dye was 99.5% in an alkaline medium. Density functional theory analysis further corroborated that the band gap energy was reduced when Ba was doped into the TiO2 lattice, implying a considerable redshift of the absorption edge due to in-gap states near the valence band.
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