Fig. 3From: Enhance the Er3+ Upconversion Luminescence by Constructing NaGdF4:Er3+@NaGdF4:Er3+ Active-Core/Active-Shell NanocrystalsUpconversion emission spectra of a NaGdF4:12%Er3+ core NPs, NaGdF4:12%Er3+@NaGdF4 active-core/inert-shell NPs, and NaGdF4:12%Er3+@NaGdF4:10%Er3+ active-core/active-shell NPs. b The NaGdF4:12%Er3+@NaGdF4:x%Er3+ (x = 9, 9.5, 10, 10.5, and 11) active-core/active-shell NPs under 1540-nm excitationBack to article page