Au/NaYF4?:?Yb,Er Binary Superparticles: Synthesis and Optical Properties

Colloidal superparticles (SPs) are nanoparticle (NP) assemblies in the form of colloidal particles. Assembling nanoscopic objects into mesoscopic or macroscopic composite architectures allows for the bottom-up fabrication of functional nanomaterials. In this study, a method for single-step self-assembly synthesis of Au/NaYF₄ : Yb,Er SPs was developed using oil-in-water (O/W) microemulsions to simultaneously encapsulate gold nanoparticles (AuNPs) and NaYF₄ : Yb,Er upconversion nanoparticles (UCNPs) via evaporation at room temperature. The synthesized Au/NaYF₄ : Yb,Er SPs possess good dispersibility and stability. When the number of AuNPs added is increased, the SPs exhibit decreased upconversion luminescence, which can be ascribed to the Förster resonance energy transfer (FRET) from the NaYF₄ : Yb,Er UCNPs to the AuNPs. Time-resolved measurements of the green emission further confirm the existence of a new decay route corresponding to the FRET process. Our research provides a facile and versatile strategy for the synthesis of novel multifunctional nanocomposites with tunable upconversion luminescence properties, which can be of great significance in biological applications.