Synchronous enhancement of upconversion and NIR-IIb photoluminescence of rare-earth nanoprobes for theranostics

This study develops a multifunctional molecular optical nanoprobe (SiO2@Gd2O3: Yb3+/Er3+/Li+@Ce6/MC540) with a unique core-satellite form. The rare-earth doped nanodots with good crystallinity are uniformly embedded on the surface of a hydrophilic silica core, and the nanoprobe can emit near-infrared-IIb (NIR-IIb) luminescence for imaging as well as visible light that perfectly matches the absorption bands of two included photosensitizers under 980 nm irradiation. The optimal NIR-IIb emission and upconversion efficiency are attainable via regulating the doping ratios of Yb3+, Er3+ and Li+ ions. The relevant energy transfer mechanism was addressed theoretically that underpins rare-earth photoluminescence where energy back-transfer and cross relaxation processes play pivotal roles. The nanoprobe can achieve an excellent dual-drive photodynamic treatment performance, verified by singlet oxygen detections and live-dead cells imaging assays, with a synergistic effect. And a brightest NIR-IIb imaging was attained in tumoral site of mouse. The nanoprobe has a high potential to serve as a new type of optical theranostic agent for tumor.