Temperature probing and emission color tuning by morphology and size control of upconverting β-NaYbGdF:Tm:Ho nanoparticles.

The chemical composition, shape and size of upconverting nanoparticles are known to have a great influence on their spectroscopic properties, such as the emission color and the emission intensity variation as a function of temperature. This work shows the color tuning and the thermal sensitivity of NaYbGdF:Tm:Ho nanoparticles synthesized by two different approaches of the same synthetic method showing the influence of size and morphology, 250 nm hexagonal-plated and 30 nm spheroidal nanoparticles, on the visible upconversion color under NIR irradiation. According to the 1931-CIE diagram, the hexagonal-shaped nanoparticles show white light emission and the spheroidal ones generate red light emission under 980 nm excitation.