Design, preparation and application of orthogonal excitation-emission upconversion nanomaterials br

Rare earth-doped upconversion luminescence nanomaterials have received considerable attentionfrom researchers due to their great potential for applications in many fields such as information security, bio-medicine, optical fiber communication, digital displays, and energy. The recently-developed upconversion lu-minescence nanoparticles with orthogonal excitation-emission properties have attracted especially strong re-search interest because their distinct luminescence outputs can be dynamically modulated by switching theexcitation conditions. The orthogonal luminescence properties further endow such nanocrystals with a set ofnew features and functionalities, which largely expands their potential applications. This review summarizesthe progress in the development of orthogonal upconversion luminescence of rare earth ions, and provides asystematic discussion on design principles and construction strategies of orthogonal excitation-emission sys-tems based on core-shell structures, as well as introduces their recent advances in various fields of applica-tions including data storage, security anti-counterfeiting, digital displays, sensing, bioimaging and therapy.Furthermore, the prospective opportunities and challenges in the future research of orthogonal luminescencesystems are also provided.