Fabrication of MoS 2 /Bi 2 S 3 heterostructure for photocatalytic degradation of Metronidazole and Cefalexin and antibacterial applications under NIR light: experimental and theoretical approach

In this research, molybdenum disulfide (MoS 2 ) and bismuth trisulfide (Bi 2 S 3 ) particles were synthesized. Bi 2 S 3 was loaded on MoS 2 nanosheet and was characterized by several techniques. Degradation of metronidazole (MTZ) and Cefalexin (CFX) were investigated via MoS 2 , Bi 2 S 3 , and MoS 2 /Bi 2 S 3 particles under near-infrared (NIR) light irradiation. The evaluations of electronic structures and molecular geometries of MoS 2 monolayer, MoS 2 /MTZ, and MoS 2 /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 MoS 2 nanosheet. In other words, the electronic features of the MoS 2 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 MoS 2 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 MoS 2 /Bi 2 S 3 photocatalyst, 91.54 and 73.18%, respectively. The results showed that the particles of Bi 2 S 3 , MoS 2 , and MoS 2 /Bi 2 S 3 under NIR light irradiation have antibacterial properties, and the highest antibacterial property is related to the MoS 2 /Bi 2 S 3 particles. Graphical abstract