Electrospinning fabrication and characterization of magnetic-upconversion fluorescent bifunctional core–shell nanofibers

Novel magnetic-upconversion fluorescent bifunctional core–shell nanofibers have been successfully fabricated by coaxial electrospinning technology. NaYF4:Yb3+,Er3+ and Fe3O4 nanoparticles (Nps) were incorporated into polyvinylpyrrolidone (PVP) and electrospun into core–shell nanofibers with Fe3O4/PVP as core and NaYF4:Yb3+,Er3+/PVP as the shell. The morphology and properties of the final products were investigated in detail by X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometer, and fluorescence spectroscopy. The core contained magnetic Nps was ca. 100 nm in diameter, and the shell scattered with NaYF4:Yb3+, Er3+ Nps was ca. 80 nm in thickness. Fluorescence emission peaks of Er3+ in the [Fe3O4/PVP]@[NaYF4:Yb3+,Er3+/PVP] core–shell nanofibers were observed. Compared with Fe3O4/NaYF4:Yb3+,Er3+/PVP composite nanofibers, the luminescent intensity of the [Fe3O4/PVP]@[NaYF4:Yb3+,Er3+/PVP] core–shell nanofibers was much higher, because the Fe3O4 Nps were only distributed in the core of the core–shell nanofibers, thus the manufactured core–shell nanofibers possessed excellent magnetic properties. The new type magnetic-upconversion fluorescent bifunctional [Fe3O4/PVP]@[NaYF4:Yb3+,Er3+/PVP] core–shell nanofibers have many potential applications in display device, nanorobots, protein determination, and target delivery of drug owing to their excellent magnetism and fluorescence. A novel magnetic-upconversion fluorescent bifunctional core-shell nanofibers are fabricated by coaxial electrospinning technique. Because the Fe3O4 nanoparticles are only distributed in the core of the core-shell nanofibers, they barely decrease the fluorescent emission intensity of the core-shell nanofibers, and strong upconversion fluorescent of the magnetic-upconversion coaxial nanofibers can be achieved.