Controlling Red Color–Based Multicolor Upconversion through Selective Photon Blocking

Abstract Photon upconversion multiplexing has attracted increasing interest in recent years; however, realizing the red color–based multicolor‐tunable output in upconversion nanoparticles (UCNPs) at a fixed composition remains a huge challenge. Here, a novel and versatile approach to fine‐control upconversion luminescence (UCL) colors from UCNPs through selectively confining specific excitation energy by the photon blocking effect is reported. Four types of dual‐color switchable UCNPs capable of emitting red‐blue and red‐green emissions are successfully designed following this strategy, and their UCL performance shows a multiwavelength (808/980/1550 nm) excitable feature that is well sustained in a wide range of excitation power density. The use of the photon blocking effect further enables the dynamically switchable red‐green‐blue UCL with 808/980 nm excitations. These findings provide a general method to achieve multicolor‐tunable UCL at a single nanoparticle level. Moreover, the UCNPs with red‐based multicolor emissions in this work enriches the upconversion system and should have potential applications in display, anti‐counterfeiting, and bioimaging.