Meijuan Liu,Hao Lin,Haoxuan Sun,Haonan Zhao,Chaofa Liang,Yulin Gong,Dekang Xu,Shusheng Pan,Liang Li
So far, existing research on upconversion nanomaterials has concentrated on tuning luminescence properties through the design of core-shell structure and the strategic incorporation of dopant ions, enabling modulation in emission color, intensity, and excitation response. Among them, most of the studies have focused on multilayer (four or more layers) core-shell structures. However, such systems often face challenges related to complex preparation processes and inefficiencies. In this work, we aimed to simplify the system by employing NaErF 4 :Nd,Yb,Ce@NaYF 4 :Yb@NaYF 4 core-shell-shell nanoparticles and optimizing the doping combination of rare-earth ions for luminescence intensity control. Compared to traditional four-layer designs, this study provides the following significant advantages: (1) ultraviolet-blue upconversion emissions can be achieved without the incorporation of commonly used Tm 3+ ions, overcoming the concentration quenching problem associated with Tm 3+ , and (2) the luminescence tuning in response to dual-wavelength (980 and 1532 nm) is achieved by a three-layer core-shell structure, significantly reducing system design complexity, fabrication challenges, and improving production efficiency. By validating its fluorescence emission performance, these nanoparticles exhibit unique potential application in photodynamic therapy and real-time fluorescence monitoring.
Jing Zuo,Langping Tu,Qiqing Li,Yansong Feng,Ivo Que,Youlin Zhang,Xiaomin Liu,Bin Xue,Luis J. Cruz,Yulei Chang,Hong Zhang,Xianggui Kong
Photoswitchable materials are important in broad applications. Recently appeared inorganic photoswitchable upconversion nanoparticles (PUCNPs) become a competitive candidate to surmount the widespread issue of the organic counterparts —photobleaching. However, current PUCNPs follow solely Yb3+/Nd3+ cosensitizing mode, which results in complex multilayer doping patterns and imperfectness of switching in UV–blue region. In this work, we have adopted a new strategy to construct Nd3+ free PUCNPs—NaErF4@NaYF4@NaYbF4:0.5%Tm@NaYF4. These PUCNPs demonstrate the superior property of photoswitching. A prominent UV–blue emission from Tm3+ is turned on upon 980 nm excitation, which can be completely turned off by 800 nm light. The quasi-monochromatic red upconversion emission upon 800 nm excitation—a distinct feature of undoping NaErF4 upconversion system—endows the PUCNPs with promising image-guided photoinduced “off–on” therapy in biomedicine. As a proof-of-concept we have demonstrated the imaging-guided photodynamic therapy (PDT) of cancer, where 800 nm excitation turns off the UV–blue emission and leaves the emission at 660 nm for imaging. Once the tumor site is targeted, excitation switching to 980 nm results in UV–blue emission and the red emission. The former is used to induce PDT, whereas the latter is to monitor the therapeutic process. Our study implies that this upconversion photoswitching material is suitable for real-time imaging and image-guided therapy under temporal and spatial control.
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