Rational Design of Branched Au–Fe3O4 Janus Nanoparticles for Simultaneous Trimodal Imaging and Photothermal Therapy of Cancer Cells

We report a facile and simple hydrogen reduction method to fabricate PEGylated branched gold (Au)–iron oxide (Fe3O4) Janus nanoparticles (JNPs). Note that the hydrogen induces the formation of Fe3O4 during the synthesis process. Due to the strong absorption in the near‐infrared range, branched Au–Fe3O4 JNPs showed a significant photothermal effect with a 40 % calculated photothermal transduction efficiency under a laser irradiation of 808 nm in vitro. Owing to their excellent optical and magnetic properties, branched Au–Fe3O4 JNPs were demonstrated to be advantageous agents for triple‐modal magnetic resonance imaging (MRI)/photoacoustic imaging (PAI)/computed tomography (CT) in vitro. Therefore, the synthetic approach could be extended to prepare Au–metallic oxide JNPs for specific applications.