Nov 29, 2012
Up-converting nanoparticles deliver strong tunable colour and bright visible light
Researchers at the Instituto de Ciencia de Materiales de Madrid ICMM-CSIC in Spain have shown how strong tunable colour and bright visible light can be generated by the up-conversion of near-infrared (∼980 nm) diode laser excitation in 5 nm silica-coated co-doped Yb, Ln-GdVO4 (Ln=Tm, Ho, Er) nanocrystals.
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.
About the author
The study was performed by members of the Photonic Materials Department based at the Instituto de Ciencia de Materiales de Madrid ICMM – an Institute of the Spanish Research Council CSIC. Rocío Calderón is currently a PhD student. She is supported by the Spanish Ministry of Economy and Competitiveness, and supervised by Concepción Cascales. C Cascales and Carlos Zaldo are research professors at ICMM. All three are working in the development of the project “New infrared ultrafast and high power lasers; Developments in materials, cavities and nanoprobes”, 2012–2014, which is also funded by the above Spanish Ministry.