Oxygen-Driven Stabilization and Electrostatic Asymmetry in Janus Mo- and W‑Based Transition Metal Dichalcogenide Nanotriangular Quantum Dots.

Janus transition-metal dichalcogenide nanotriangular quantum dots provide a unique platform for engineering internal electrostatic asymmetry at the nanoscale. In this manuscript, we present a systematic investigation of pristine, nonoxygen Janus, and oxygen-containing Janus Mo- and W-based nanotriangles, in which size, edge geometry, and the chemical composition of the chalcogens govern their stability, curvature, and electrostatic response. The oxygen-containing counterparts are the most stable, followed by the nonoxygen Janus and finally, the pristine nanotriangles. Edge configuration is favored due to reinforced metal-oxygen bonding, as confirmed by ab initio molecular dynamics, which showed stability up to room temperature. The electrostatic potential analysis revealed pronounced potential gradients and spatially separated charge accumulation in oxygen-containing systems, with enhanced curvature and internal polarization. The nonoxygen-containing Janus nanotriangles also produce curvature, but less pronounced because of the smaller electronegativity difference. These effects are systematically stronger in W-based nanotriangles. Oxygen incorporation, edge geometry, and chalcogen identity serve as key descriptors governing the stability and internal electrostatic fields of Janus transition-metal dichalcogenide nanotriangles. The results presented here establish the foundation for a rational design of quantum dots useful in photocatalysis applications.