Abstract: | Biocompatible single‐component theranostic nanoagents instinctly affording multiple imaging modalities with satisfying therapeutic functions are highly desirable for anticancer treatments. Although cobalt‐based phosphides are well‐recognized as competent electrocatalysts, their potentials for biomedical applications remain unexplored. In this work, cobalt phosphide nanoparticles (CoP NPs) are developed to be a powerful theranostic agent for multimodal imaging and anticancer photothermal therapy. The uniform CoP NPs in a size of ≈21 nm are synthesized via a facile thermal decomposition method, followed by surface modification. The resultant CoP NPs exhibit excellent compatibility and stability in water as well as various physiological solutions. Supported by the good biocompatibility, strong near‐infrared absorption, and high photothermal conversion property, significant photothermal effect of the NPs is demonstrated, realizing efficient hyperthermia ablation on cancer cells. Importantly, the CoP NPs have shown considerable capabilities on high‐contrast in vitro and in vivo triple‐modal imaging, including infrared thermal (IRT), photoacoustic (PA), and T2‐weighted magnetic resonance (MR) imaging. This work has unraveled the promising potentials of CoP‐based nanoagent for precise diagnosis and efficient therapy. |