Mesoscale regulation of β-NaYF4: Yb/Er with desired size and morphology via introducing Li+/K+ into the hydrothermal environment

Controllable sysnthsis NaYF4:Yb3+/Er3+ via mesoscale regulation through introducing Li+/K+ into the hydrothermal system has been developed. The crystal evolution process of β-NaYF4:Yb3+/Er3+ is investigated based on the reaction parameters. The mesoscale growing process include four stages: (1) nucleation; (2) aggregation; (3) orientation growth; (4) ripening. Through introducing Li+/K+ into the hydrothermal environment, super-small β- NaYF4:Yb3+/Er3+ upconversion nanoparticles can be obtained.