Lanthanide-doped up-converting nanoparticles (Ln-UCNPs) provide the opportunity for a number of photonic applications – for example, the fabrication of colour panel displays and technology related to the generation of white light. White light achieved by an adequate balance of red, green and blue (RGB) up-converted light from Ln-UCNPs offers an alternative to other white light systems such as GaN LEDs, white OLEDs or ultrasmall CdSe nanocrystals.

To improve the up-conversion efficiency of hydrothermal Yb, Ln-GdVO4 (Ln=Tm, Ho, Er) UCNPs, the team focused its attention on minimizing quenching effects from defects and adsorbed species at the surface of the material. Raw samples were processed in a number of different ways that included or combined annealing at 600 °C for 5 h, coating with a silica layer of controlled thickness and a further annealing step.

Following treatment, the intensity of visible light emitted by the up-converting NPs was significantly improved compared with raw hydrothermal nanocrystals.

In the study, strong tunable colour and bright visible light consisting of red-green, blue and green emissions from Ho3+, Tm3+ and Er3+, respectively, was generated by adjusting the Yb-Ln composition of the silica-coated nanocrystals.

More information can be found in the journal Nanotechnology.