Temperature self-monitoring photothermal nano-particles of Er3+/Yb3+ Co-doped zircon-tetragonal BiVO4

Abstract Self-monitored photo-thermal therapy (PTT) still faces huge challenge in cancer treatment, which aims to realize the real-time temperature reading during the course of optical heating. Exploiting new-type photo-thermal therapeutic agent (PTA) with thermometric function is considered to be one of effective methods to fulfill self-monitored PTT. In this work, spindle-like zircon-tetragonal (z-t) phase BiVO4:Yb3+/Er3+ up-conversion (UC) nano-particles as self-monitored PTAs were prepared through the combination of co-precipitation and hydrothermal method. Under 980 nm laser diode excitation, real-time thermometry was accomplished by monitoring thermo-responsive emission intensity ratio of Er3+ (2H11/2/4S3/2 → 4I15/2) transitions. Meanwhile, the photo-thermal conversion effect associated with UC process was trigged via the non-radiative transition channels. Considering the balance between UC emission intensity and heat generation, the optimal sample composition was determined as BiVO4:20%Yb3+/3%Er3+. Their maximum absolute sensitivity (Sa) reached 0.0125 K-1 at 460 K as the thermometer and the ability of photo-thermal conversion up to 3.32 K cm2/W as PTAs. Their potential applications in controlled subcutaneous photo-thermal treatment were estimated through ex vivo experiments. Results provided a new choice for nano-materials to realize real-time temperature feedback in the single host material (z-t BiVO4) during the course of PTT.