Onion-Structured Spherical MoS2 Nanoparticles Induced by Laser Ablation in Water and Liquid Droplets’ Radial Solidification/Oriented Growth Mechanism

Spherical MoS 2 nanoparticles are fabricated by laser ablation of MoS 2 target in water. The obtained nanoparticles are mostly nearly perfectly spherical in shape with smooth surface, and tens to hundreds of nanometers in diameters. Such spherical MoS 2 nanoparticles are built by concentrically curved {002} planes and show onion-like structure. Further examination has revealed that there exist shrinkage cavities (or voids) in the central part of the MoS 2 nanoparticles or small pores dispersed in the particles and a few tadpole-like long-tailed nanoparticles in the products, indicating the marks of melting and molten liquid droplets’ solidification during laser ablation. A model is thus presented based on laser-induced MoS 2 liquid droplets’ generation and inward {002}-oriented growth via radial solidification, which reveals the growth mechanism of the spherical MoS 2 nanoparticles with onion-like structure. Interestingly, such onion-like structured spherical MoS 2 nanoparticles have exhibited much higher surface-enhanced Raman scattering (SERS) effect than the MoS 2 nanoplates prepared by conventional methods. This work not only presents the route to the spherical MoS 2 nanoparticles with onion-like structure but also reveals the formation process for the MoS 2 nanoparticles in laser ablation in water.