Phase-Dependent 1T/2H-MoS₂Nanosheets for Effective Photothermal Killing of Bacteria

The crystal phase of a nanomaterial can affect its biochemical properties and, as a result, greatly influence its application performance. Transition metal dichalcogenides (TMDs), a group of nanomaterials with the ability to crystallize into distinct crystal phases, show distinct electronic structures which are believed to be material-dependent. Molybdenum disulfide (MoS2) can crystallize into distinct crystal phases of 1T and 2H, and in each of these phases, MoS2 shows completely different and distinct biochemical properties. Although several biochemical properties of MoS2 have been extensively reported, particularly its role as a potent antibacterial agent, exactly how the different crystal phases of MoS2 nanosheets (NSs) influence the nanomaterial's biochemical performance in the near-infrared (NIR)-I window still remains unknown. Herein, we show through detailed experiments and density functional theory (DFT) simulation of the NIR-based electronic structure-activity relationship of 1T- and 2H-MoS2 NSs exactly how these two distinct phases influence the antibacterial performance at each crystal phase and the different factors involved in this process. We also show how the coordination modes, atomic arrangements, and water adsorption energies of these two crystal phases greatly impact the nanomaterial's distinct phase properties. 1T-MoS2 NSs are metallic phases with a lower band gap and surface water adsorption energy, while 2H-MoS2 NSs are semiconducting phases; as a result, 1T-MoS2 NSs show superior absorbance in the NIR-I window and hence display a higher photothermal performance and excellent antibacterial effects compared to the semiconducting 2H-MoS2 NSs. Our work shows the factors responsible for the distinct antibacterial behaviors of MoS2 NSs in the two crystal phases. We believe that these findings can be employed in the tunable, effective, and stable nanofabrication of MoS2 NSs as either photothermal agents for cancer cell ablation or as antimicrobial agents.