Multimodal Ultra-Small Cofe-Wox Nanohybrids Synthesized by a Scaled-Up Continuous Flow Process

Ultra-small (2-3 nm) CoFe-WO x nanohybrids with a tiny CoFe core and a mixed metal oxides shell (CoWO 4 -Fe 2 WO 6 -WO 3 ) were continuously synthesized by a scaled-up microfluidic set-up. The competition between the nucleation of metal atoms from metal ions reduction and the gellation of the forming polyhydroxy-metal ion sols on the formed metal atom clusters finally constructs this kind of homogeneous dispersed nanohybrids, with a relatively uniform size (2.3 ± 0.4 nm). Their multi-mode imaging functions were evaluated with the characterization of their magnetic and optical properties and the response to X-ray radiation. They can be optically detected via dark-field microscope and can be imaged through X-ray computed tomography. They can also be used as magnetic resonance imaging contrast agents with excellent T2-weighted spin-echo imaging effects. Most amazing, hybridization between metal cores and metal-oxide shells was for the first time able to achieve two strong absorption peaks at the long band of near infrared radiation, one at 1450 nm and another at 1980 nm. Additionally, individual CoFe-WO x particles can be firstly observed under dark-field microscopy, showing uniform blue-green color. Overall, CoFe-WO x nanohybrids have unique magnetic and optical properties and multimode imaging capabilities based on their microstructure and composition. These findings provide effective alternatives for nanoprobes that can be used for visible/infrared/MRI/CT imaging, as well as pre-drugs for photothermal/photodynamic and magnetothermal/magneto-dynamic therapies.