Upconversion NaYF 4 :Yb:Er nanoparticles co-doped with Gd 3+ and Nd 3+ for thermometry on the nanoscale

In the present work, the upconversion luminescence properties of oleic acid capped NaYF 4 :Gd 3+ :Yb 3+ :Er 3+ upconversion nanoparticles (UCNP) with pure β crystal phase and Nd 3+ ions as an additional sensitizer were studied in the temperature range of 288 K < T < 328 K. The results of this study showed that the complex interplay of different mechanisms and effects, causing the special temperature behavior of the UCNP can be developed into thermometry on the nanoscale, e.g. to be applied in biological systems on a cellular level. The performance was improved by the use of Nd 3+ as an additional dopant utilizing the cascade sensitization mechanism in tri-doped UCNP.