Multifunctional NaYF₄:Yb³⁺,Er³⁺@SiO₂@Au heterogeneous nanocomposites for upconversion luminescence, temperature sensing and photothermal conversion

NaYF₄:Yb³⁺,Er³⁺@SiO₂@Au heterogeneous nanostructures, with the ability of integrating upconversion luminescence (UCL) and photothermal therapy as well as real-time temperature monitoring, have been successfully prepared. The UCL intensities of NaYF₄:Yb³⁺,Er³⁺ nanocrystals showed an obvious reduction after gold nanoparticle attachment and gold shell coating, but it was found that they were independent of the SiO₂ spacer layer thicknesses. The presence of gold nanostructures can significantly improve the photothermal conversion properties of NaYF₄:Yb³⁺,Er³⁺ nanocrystals with an increased temperature up to 39 °C, while retaining their temperature sensing properties, manifesting their great potential as diagnostic and therapeutic tools for use in biomedical fields.