Fig. 5From: Enhance the Er3+ Upconversion Luminescence by Constructing NaGdF4:Er3+@NaGdF4:Er3+ Active-Core/Active-Shell NanocrystalsThe effect of core–shell composition on a the intensity ratio between the green and the red emissions and b bandwidth values with the full width at half maximum of 540 and 660 nmBack to article page