Fabrication, formation mechanism and optical properties of novel single-crystal Er3+ doped NaYbF4 micro-tubes

A novel Er3+ doped NaYbF4 hexagonal-prismatic micro-tubular structure with single crystalline nature was synthesized by a facile hydrothermal method. The typical morphologies and structure were investigated by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) which revealed that the as-prepared samples presented a tubular structure with open ends and uniform size. Based on TEM analysis of the samples prepared at different hydrothermal treatment times, the formation mechanism of the NaYbF4 hexagonal-prismatic micro-tube was concluded to be that the nano-sized clusters nucleated first and then self-assembly aggregated into thin sheets and finally rolled into NaYbF4 hexagonal-prismatic micro-tubes. Intense red upconversion luminescence was observed by the naked eye under 980 nm excitation, which indicated that the novel NaYbF4 micro-tubular structure is a potential host material for photoluminescence. Due to the unique luminescence, these NaYbF4 hexagonal-prismatic micro-tubes may be promising for further fundamental research and find applications in color displays and solid-state lasers.