Femtosecond laser generation of bimetallic oxide nanoparticles with potential X-ray absorbing and magnetic functionalities for medical imaging applications

Bimetallic nanoparticles have gained vivid attention due to their unique and synergistic properties. They can be used in fields such as solar cells, optics, sensing, as well as medicine. The generation of bimetallic nanoparticles, containing oxide phases of both magnetic and X-ray attenuating metals for bioimaging applications has been challenging with traditional chemical synthesis methods. An alternative is the generation of nanoparticles from binary oxide ceramics by laser ablation in liquid. However, the applicability of this technique for production of hybrid nanoparticles consisting of magnetic and X-ray absorbing elements has not been demonstrated yet. In this work, novel ceramics composed of bimetallic oxide phases of iron-tantalum, iron-tungsten, and ironbismuth were produced by a reaction-sintering method. The bulk samples were characterized with scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffractometry. Nanoparticles were produced in aqueous and ethanol solutions by employing a femtosecond laser and characterized with transmission electron microscopy, selected area electron diffraction, and energy dispersive X-ray spectroscopy. The results demonstrated that the production of binary oxide bulk ceramics and their subsequent laser ablation in liquids leads to the successful generation of bimetallic oxide nanoparticles, without a core-shell morphology. In addition, it was found that the ablation threshold fluence of bulk samples as well as the crystallinity of the synthesized nanoparticles is governed by both the nature of the metallic oxide ceramics and the employed liquid. The results pave the way for a single step generation of well-defined bimetallic nanoparticles by laser ablation that could potentially exhibit X-ray and magnetic absorption properties suitable for multimodal imaging applications.This research has been partially funded by the Spanish Ministerio de Ciencia e Innovacion through the research project MAT2015-67354R (MINECO-FEDER). Funding through a Marie Sklodowska-Curie Individual Fellowships (MSCA-IF 2014, 656908-NIMBLIS-ESR) of the Horizon 2020 program, and the Project PI-0030-2017 of the Junta de Andalucia in the framework of the integrated territorial initiative 20142020 for research and innovation in biomedicine and health sciences in the province of Cadiz is also greatly appreciated. The authors acknowledge support for scanning electron microscopy by Dr. Stephan Puchegger and the faculty center for nanostructure research at the University of Vienna