Self-assembly of nanoparticles into ordered patterns is a novel approach to build up new consolidated materials with desired collective physical properties.
Dual-mode excitation β-NaGdF4:Yb/Er@β-NaGdF4:Yb/Nd core–shell nanoparticles with NIR-II emission and 5 nm cores were synthesized using an ultra-low single dose of NaF.