Fabrication of MoS2/Bi2S3 heterostructure for photocatalytic degradation of Metronidazole and Cefalexin and antibacterial applications under NIR light: experimental and theoretical approach

In this research, molybdenum disulfide (MoS2) and bismuth trisulfide (Bi2S3) particles were synthesized. Bi2S3 was loaded on MoS2 nanosheet and was characterized by several techniques. Degradation of metronidazole (MTZ) and Cefalexin (CFX) were investigated via MoS2, Bi2S3, and MoS2/Bi2S3 particles under near-infrared (NIR) light irradiation. The evaluations of electronic structures and molecular geometries of MoS2 monolayer, MoS2/MTZ, and MoS2/CFX complexes were implemented using the DFT method. According to the electronic density of states (DOS) graphs results, when the MTZ and CFX interact with the monolayer surface, the energy gap (E-g) decreases compared to the MoS2 nanosheet. In other words, the electronic features of the MoS2 monolayer were altered after interaction with MTZ and CFX, where a reduction in the E-g value was evaluated (from 1.973 eV in the bare MoS2 to 0.010 and 1.936 eV in states MTZ and CFX complexes, an alteration of 99.49 and 1.875%, respectively. It can be concluded that the band gap significantly changes when the MTZ interacts with the monolayer surface. The maximum removal efficiencies of MTZ and CFX in 40 min and at pH 7 were obtained by MoS2/Bi2S3 photocatalyst, 91.54 and 73.18%, respectively. The results showed that the particles of Bi2S3, MoS2, and MoS2/Bi2S3 under NIR light irradiation have antibacterial properties, and the highest antibacterial property is related to the MoS2/Bi2S3 particles.{graphical abstract}