Enhancing charge transfer with foreign molecules through femtosecond laser induced MoS2 defect sites for photoluminescence control and SERS enhancement

Abstract

Defect/active site control is crucial for tuning the chemical, optical, and electronic properties of MoS₂, which can adjust the performance of MoS₂ in application areas such as electronics, optics, catalysis, and molecular sensing. This study presents an effective method of inducing defect/active sites, including micro/nanofractured structures and S atomic vacancies, on monolayer MoS₂ flakes by using femtosecond laser pulses, through which physical–chemical adsorption and charge transfer between foreign molecules (O₂ or R6G molecules) and MoS₂ are enhanced. The enhanced charge transfer between foreign molecules (O₂ or R6G) and femtosecond laser-treated MoS₂ can enhance the electronic doping effect between them, hence resulting in a photoluminescence photon energy shift (reaching 0.05 eV) of MoS₂ and Raman enhancement (reaching 6.4 times) on MoS₂ flakes for R6G molecule detection. Finally, photoluminescence control and micropatterns on MoS₂ and surface-enhanced-Raman-scattering (SERS) enhancement of MoS₂ for organic molecule detection are achieved. The proposed method, which can control the photoluminescence properties and arbitrary micropatterns on MoS₂ and enhance its chemicobiological sensing performance for organic/biological molecules, has advantages of simplicity, maskless processing, strong controllability, high precision, and high flexibility, highlighting the superior ability of femtosecond laser pulses to achieve the property control and functionalization of two-dimensional materials.