808 nm triggered multifunctional UCNPs@PDA nanocomposites for temperature sensing and photothermal conversion

Multifunctional nanoparticles with marvelous temperature sensing and photothermal conversion are preferable in photothermal therapeutic applications. Herein, nanocomposites of NaYF 4 :Er 3+ /Yb 3+ @NaYF 4 :Nd 3+ /Yb 3+ core–shell upconversion nanoparticles (UCNPs) modified by polydopamine (PDA) were designed to achieve temperature sensing and efficiency of photothermal conversion. It has been found that under the irradiation of 808 nm laser, temperature sensing can be realized on the basis of the fluorescence intensity ratio of Er 3+ green light emission. In addition, the photothermal conversion ability of the UCNPs modified by PDA is greatly improved. Moreover, Nd 3+ as activator endows UNCPs excited by 808 nm, which can avoid overheating due to the absorption of the excitation band (980 nm) in water. Therefore, the multifunctional nanoparticles are expected to become an effective drug for cancer therapy in the future and this research will stimulate interest in designing multifunctional nanoparticles that are biocompatible, especially for in vivo tumor diagnosis.