Enhancing upconversion luminescence of Er3+ ions In NaYF4:Yb3+/Er3+/Au@Ag composite nanostructures

Enhancing upconversion luminescence in rare-earth materials through the plasmonic effects of precious metals has emerged as a highly effective strategy. In this study, we explore three distinct self-assembly techniques to fabricate alloy nano-film substrates using silver-coated gold (Au@Ag) core-shell nanoparticles, each with unique structural attributes. To enhance the upconversion luminescence of Er³⁺ ions, we combine these substrates with NaYF₄:Yb³⁺/Er³⁺ nanoparticles, creating NaYF₄:Yb³⁺/Er³⁺/Au@Ag composite nanostructures. The upconversion emission of Er³⁺ ions is observably boosted when directly combined with Au@Ag nano-films of various structures under a 980 nm laser excitation. Surprisingly, incorporating a NaYF₄ inert shell as an isolating layer results in a remarkable 13.7-fold enhancement of upconversion luminescence in the NaYF₄:Yb³⁺/Er³⁺@NaYF₄/Au@Ag composite structure relative to isolated NaYF₄: Yb³⁺/Er³⁺ nanoparticles. The enhancement mechanism was carefully discussed based on spectral characteristics and luminous lifetime. It was found that the enhanced upconversion emission of nanoparticles on differently structured substrates is primarily driven by excitation enhancement. The composite rare-earth and metal nanoparticle structures fabricated in this investigation not only effectively enhance material spectral properties effectively but also streamline the process by employing an inert NaYF₄ shell as an isolation layer. This novel approach offers a promising avenue for developing efficient luminescent material systems.