Construction of Au@NaYF4:Yb3+, Er3+/Ho3+ bifunctional hybrid nanocomposites with upconversion luminescence and photothermal properties

Bifunctional hybrid nanocomposites based on upconversion luminescence and photothermal properties have a wide range of application, especially biomedical diagnosis and therapy. Herein, the hybrid nanocomposites were prepared via combining NaYF4:Yb3+, Er3+/Ho3+ nanocrystals as shell layer materials and Au nanoparticles as the cores. The as-prepared nanocomposites can simultaneously take advantage of both the upconversion luminescence of NaYF4:Yb3+, Er3+/Ho3+ nanocrystals and the photothermal transduction property of Au nanoparticles. The structure, morphology and composition of the nanocomposites were confirmed by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). In addition, the upconversion luminescence and photothermal transduction were evaluated. We observed an overlap between the absorption band of Au nanoparticles and the upconversion emission peaks of the Er3+/Ho3+ ions, and the luminescence resonance energy transfer (LRET) was studied and demonstrated. Under 980 nm laser irradiation, upconversion luminescence and efficient photothermal transduction of the hybrid nanocomposites were found. Moreover, the bifunctional nanocomposites also have shown excellent biocompatibility.