MoS₂ core-shell nanoparticles prepared through liquid-phase ablation and light exfoliation of femtosecond laser for chemical sensing

Molybdenum disulfide (MoS₂)-based nanostructures are highly desirable for applications such as chemical and biological sensing, photo/electrochemical catalysis, and energy storage due to their unique physical and chemical properties. In this work, MoS₂ core-shell nanoparticles were first prepared through the liquid-phase processing of bulk MoS₂ by a femtosecond laser. The core of prepared nanoparticles was incompletely and weakly crystalline MoS₂; the shell of prepared nanoparticles was highly crystalline MoS₂, which wrapped around the core layer by layer. The femtosecond laser simultaneously achieved liquid-phase ablation and light exfoliation. The formation mechanism of the core-shell nanoparticles is to prepare the nanonuclei first by laser liquid-phase ablation and then the nanosheets by light exfoliation; the nanosheets will wrap the nanonuclei layer by layer through van der Waals forces to form core-shell nanoparticles. The MoS₂ core-shell nanoparticles, because of Mo−S bond breakage and recombination, have high chemical activity for chemical catalysis. Afterward, the nanoparticles were used as a reducing agent to directly prepare three-dimensional (3D) Au-MoS₂ micro/nanostructures, which were applied as surface-enhanced Raman spectroscopy (SERS) substrates to explore chemical sensing activity. The ultrahigh enhancement factor (1.06×10¹¹), ultralow detection limit (10⁻¹³ M), and good SERS adaptability demonstrate highly sensitive SERS activity, great ability of ultralow concentration detection, and ability to detect diverse analytes, respectively. This work reveals the tremendous potential of 3D Au-MoS₂ composite structures as excellent SERS substrates for chemical and biological sensing.