Controlled growth along circumferential edge and upconverting luminescence of β-NaYF4: 20%Yb3+, 1%Er3+ microcrystals

Rational control over the uniform morphology and size of hexagonal NaYF4 has been achieved via a facile hydrothermal route. The evolution of particle morphology from peg-top-like to hexagonal microprisms with protruding centers and the long tubelike morphology with concave wedge and finally to solely microrods been demonstrated by increasing the F−/Ln3+ molar ratio, all other parameters being equal. Rationally controlling the shape of hexagonal NaYF4 is of great importance due to their strongly shape-dependent optical properties. Moreover, the systematic study on the photoluminescence of 20%Yb3+, 1%Er3+-doped β-NaYF4 with different shapes shows that the upconversion (UC) properties of these products are strongly dependent on the combined roles of morphologies, crystallinity, and particle sizes. In particular, the microrods evince a better PL signal as compared with others.