Wire-in-tube nanofiber as one side to construct specific-shaped Janus nanofiber with improved upconversion luminescence and tunable magnetism

It is an important strategy to rationally design and construct specific-shaped microscopic nanostructures for developing poly-functional nanomaterials for different advanced applications. In this work, a novel technique combining a parallel electrospinning with a subsequent bi-crucible fluorination is advanced and utilized to facilely synthesize a brand-new peculiar one-dimensional (1D) wire-in-tube nanofiber//nanofiber shaped Janus nanofiber (WJNF) to refrain from usual complicated preparation procedures. Partition of four independent domains in the peculiar-structured Janus nanofiber is microscopically realized. The Janus nanofiber with four microscopic partitions can be applied to assemble various functions to avoid adverse mutual impacts among functions to realize multi-functionalization of the materials. As a case study, [YF 3 :Yb 3+ , Er 3+ @SiO 2 ]//CoFe 2 O 4 WJNFs with synchronous excellent upconversion luminescence and tunable magnetism are designed and constructed by the above technique. One side of the WJNF is composed of YF 3 :Yb 3+ , Er 3+ @SiO 2 wire-in-tube nanofiber with YF 3 :Yb 3+ , Er 3+ nanofiber as core layer and SiO 2 as shell layer, and the other side is composed of CoFe 2 O 4 magnetic nanofiber. YF 3 :Yb 3+ , Er 3+ green upconversion luminescent nanofiber is completely separated from CoFe 2 O 4 to fully avoid the weakening of luminescent intensity caused by the direct contact between luminescent and magnetic substances, and thus the luminescent intensity of [YF 3 :Yb 3+ , Er 3+ @SiO 2 ]//CoFe 2 O 4 WJNFs is apparently enhanced. Up-conversion luminescent intensity and magnetism of the WJNFs are modulated by tuning the contents of CoFe 2 O 4 . With the increase of CoFe 2 O 4 content, the saturation magnetization of the WJNFs increases from 3.91 to 12.90 emu·g −1 , revealing the tunable magnetism of the product. The formation mechanism of WJNFs is advanced, and a corresponding facile construction technique is established to shun complicated process, which provides theoretical guidance and technical support for the design and preparation of other poly-functional nanomaterials.