Direct Z-Scheme AgBr/β-MnO₂ Photocatalysts for Highly Efficient Photocatalytic and Anticancer Activity

The preparation of visible light-responsive efficient photocatalysts for removing organic contaminants from water and killing cancer cells has gotten a lot of attention due to the growing global concern. In this study, we have successfully fabricated an efficient AgBr/β-MnO₂ nanocomposite via a facile deposition and precipitation method at room temperature. Techniques such as XRD, SEM-EDS, TEM, DRS, PL, EIS, ESR, and FTIR were used to determine the crystalline, structural, morphological, optical, and other properties. The SEM and TEM analyses reveal that AgBr NPs are decorated on the surface of β-MnO₂, which possesses rods with a sphere-like structure for AgBr/β-MnO₂. The EDX analysis confirms the existence of Mn, O, Ag, and Br elements in the nanocomposites without an extra peak, indicating that the synthesized samples are highly pure. The high photocatalytic performance of AgBr/β-MnO₂ could be attributed to the formation of Ag NPs and the construction of the Z-scheme heterojunction between AgBr and β-MnO₂. This may enhance fast light absorption and efficient photogenerated (e-/h+) pairs, as indicated by EIS and photoluminescence measurements, which in turn achieved high activity for the decomposition of MB (97%, in 12 min), RhB (98.9%, in 9 min), and paracetamol (80%, in 180 min), respectively. The kinetic model study proposed that the first-order model showed a better fit than the zero- and second-order for the photocatalytic decolorization of RhB dye. XRD analysis of 0.2 AgBr/β-MnO₂ before and after recycling confirms the high stability of the catalyst. HPLC results showed that no detectable by-products are produced through the decomposition of paracetamol. Interestingly, 0.2 AgBr/β-MnO₂ nanocomposites showed visible light-induced anticancer activity against A549 cancer cell lines. The mechanistic degradation pathway has been proposed using the involvement of active species like superoxide radicals (^-•O₂) and photoinduced holes (h⁺). The proposed work focuses on synthesizing effective photocatalysts in a less hazardous environment with superior biological activity.