Enhancing the upconversion luminescence and photothermal conversion properties of ∼800nm excitable core/shell nanoparticles by dye molecule sensitization.

Upconversion nanoparticles capable of strongly absorbing photons in a wide spectral range are highly desired for practical applications. In this work, IR-806 dye was used to increase the light absorptivity of Nd/Yb/Er tri-doped core/shell nanoparticles and then to enhance their upconversion luminescence under ∼800nm excitation. The IR-806 dye exhibited more efficient energy transfer to Nd ions than to Yb ions for subsequent upconversion emission due to the increased spectral overlap between the dye emission and Nd absorption. The influence of the Nd concentration in the shell and the dye/nanoparticle ratio on the dye-sensitization effect was also investigated. A maximum 28-fold overall enhancement in the emission intensity was achieved for NaYF:Yb/Er@NaYF:Yb/Nd core/shell nanoparticles using dye sensitization. The dye-sensitized NaYF:Yb/Er@NaYF:Yb/Nd core/shell nanoparticles also exhibited increased photothermal conversion capabilities and excellent temperature sensing properties, enabling their potential application in photothermal nanoheaters with real-time temperature monitoring under 808nm single beam excitation.