A Metal Induced Color Tuning of Upconversion Nanoparticles for Multi-Level Security application

Abstract

We modulated color of rare-earth-doped upconverting nanocrystals (UCNs) via noble metal nanoparticle growth. UCNs convert continuous-wave near infrared light (NIR) to visible range luminescence through an anti-Stoke emission process. The luminescence color of the UCNs is altered by modifying the relative fraction of the lanthanide dopants. Here, we synthesized noble metal nanoparticles in the polymeric 3D structure. Surface plasmon resonance (SPR) band of metal nanoparticle eliminates particular wavelength and permits luminescence color change emitted from UCNs. By controlling metal nanoparticles morphology, we generated various surface plasmon resonance band which triggers both of optical color transition under the visible light and luminescent color transition under the infrared light. This dual-color transition system opens a new horizon for multi-level security application.