Ternary\nHeteronanocrystals with Dual-Heterojunction\nfor Boosting Near-Infrared-Triggered Photo-Chemodynamic Therapy

Strongly\ncoupled interfaces in the epitaxial growth heteronanocrystals\n(HNCs) provide advanced functionalities regarding interface connection,\nelectron transfer, and carrier separation. However, the majority of\ncurrent nanocomposites primarily focus on a single heterojunction\ninvolving only two subunits, which hinders the achievement of optimized\nsynergy energy transfer among more than two components. Herein, ternary\nNaGdF<sub>4</sub>:Yb,Tm-TiO<sub>2</sub>:F-Fe<sub>3</sub>O<sub>4</sub> HNCs with dual-heterojunction were synthesized based on the crystal\nplane epitaxial growth strategy for boosting near-infrared (NIR)-triggered\nphoto-chemodynamic therapy (PCDT). Fluorine is doped into TiO<sub>2</sub> (TiO<sub>2</sub>:F), which not only enhances the exposure\nof the (001) facet of TiO<sub>2</sub> for Fe<sub>3</sub>O<sub>4</sub> subunit growth but also promotes the growth of the NaGdF<sub>4</sub>:Yb,Tm upconversion nanocrystal (UCNC) subunit, enabling an epitaxial\ncombination of all three components. Upon NIR irradiation, the UCNC\nsubunit transfers the light energy of the absorbed NIR light to the\nTiO<sub>2</sub>:F subunit, thereby facilitating the generation of\nelectron–hole pairs within TiO<sub>2</sub>:F. Due to different\nwork functions between TiO<sub>2</sub>:F and Fe<sub>3</sub>O<sub>4</sub> in the ternary HNCs, electrons tend to transfer from TiO<sub>2</sub>:F into Fe<sub>3</sub>O<sub>4</sub>, resulting in a reduction of\ninactive Fe<sup>3+</sup> into active Fe<sup>2+</sup> and further enhancing\nthe Fenton-catalysis performance. Simultaneously, the efficient separation\nof electrons and holes improves the photocatalytic oxidation property\ninduced by TiO<sub>2</sub>:F. Based on ternary UCNC-TiO<sub>2</sub>:F-Fe<sub>3</sub>O<sub>4</sub> HNCs boosting Fenton catalysis and\nphotocatalysis at the single particle level, as a proof of concept,\nwe propose a NIR light-triggered PCDT (NIR-PCDT) synergistically enhanced\ntumor treatment strategy. In vitro and in vivo experiments demonstrate\nthat this NIR-PCDT agent exhibits a pronounced ability to generate\nreactive oxygen species, effectively inducing apoptosis in tumor cells.