One-step selective formation of silver nanoparticles on atomic layered MoS₂ by laser-induced defect engineering and photoreduction

Two dimensional (2D) materials decorated with noble metal nanoparticles (NPs) have attracted wide attention due to their appealing chemical and physical properties. Herein, we have developed a novel approach to controllable and selective decoration of silver NPs on atomic layered molybdenum disulfide (MoS₂) by using one-step laser-induced defect engineering and photoreduction. By employing a focused micro-power laser beam, silver NPs can be rapidly (in seconds) anchored onto the irradiated area of MoS₂ flakes, forming 0D/2D AgNPs@MoS₂ heterostructures. The mechanism for silver growth on MoS₂ flakes was based on laser-induced defect creation in a silver ion environment and silver nucleation on laser-excited MoS₂ flake surfaces, as evidenced by a combination of techniques including Raman spectroscopy, atomic force microscopy and second-harmonic generation. We also found that the morphology and the growth rate of silver NPs are highly dependent on the layer thickness of MoS₂ and the laser irradiation power; while the size and number density of silver NPs could be precisely controlled by varying the irradiation time as well as the silver ion concentration. Finally, AgNPs@MoS₂ heterostructure micro-patterns have been successfully demonstrated via a programmed low-power laser scan, which shows great potential to be used as an efficient surface enhanced Raman scattering platform for chemical sensing.