A plasmonic hetero-structure using charge transfer effect improved LSPR for enhanced up-conversion luminescence

Abstract

Local surface plasmon resonance (LSPR) offers exciting prospects for optical signal amplification. In this study, we designed a composite hetero-structure of Au and defective MoS₂ (Au/D-MoS₂) for a charge transfer type LSPR modulator. D-MoS₂ produces strong defect plasma absorption in the visible and near-infrared optical regions and injects a large number of its generated electrons into the composite Au nanoparticles via surface charge transfer under near-infrared laser excitation, enabling strong plasmon resonance in the Au nanoparticles. As a result, the NaYF₄:Yb–Er nanoparticles are effectively modulated in their luminescence intensity by the dual coupling enhancement effect of the MoS₂ nanoparticles plasmon resonant excitation field and the Au nanoparticles plasmon resonant emission field under near-infrared excitation. Due to the strong LSPR induced electric field, a maximum enhancement factor of 15-fold in the luminescence intensity is achieved. This intelligent approach enables efficient modulation of NaYF₄:Yb–Er in terms of both excitation and emission field enhancement, opening a new avenue to enhance the intensity of up-conversion luminescence.