Electrospun magnetic-electrically conductive-fluorescent polyfunctional Janus nanofiber@fiber typed microfibers and array

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Specially-designed and manufactured microstructures as constitutional units play vital roles in modulating the characteristics and functions of multifunctional materials. In this study, [CoFe2O4/polyvinylpyrrolidone (PVP)]//[polyaniline (PANI)/PVP] Janus nanofiber@[Tb(acac)3bpy/PVP] fiber typed (denoted as [(M//E)@F]) microfiber and array are designed and synthesized by a modified electrospinning device for the first time. Magnetism, electrical conduction and fluorescence are microscopically assembled into a Janus nanofiber@fiber typed microfiber, thus obtaining excellent magnetic-electrically conductive-fluorescent trifunctionality. In addition, the array displays insulation-fluorescence on its surface and magnetic-electrical conduction in interior. The [(M//E)@F] microfiber contains the core layer (CL) of (CoFe2O4/PVP)//(PANI/PVP) Janus nanofiber with magnetic-electrically conductive bifunctionality and shell layer (SL) of Tb(acac)3bpy/PVP fiber with fluorescent functionality, and all the [(M//E)@F] microfibers are aligned in the same direction to form the array. Compared with the corresponding conventional coaxial microfiber with two independent partitions, the Janus nanofiber replaces the microfiber in the CL to form the special structure [(M//E)@F] microfiber, so that the [(M//E)@F] microfiber achieves three independent partitions on the microscopic level. The obtained microstructure can achieve the complete separation of CoFe2O4 nanoparticles (NPs), PANI and rare earth complexes, and PANI has continuity in the matrix, guaranteeing intense fluorescence and high conduction. Due to the special Janus structure, the CL conducts electricity along the lengthwise direction of the Janus nanofiber and is insulated perpendicular to the lengthwise direction (viz. widthwise direction) of the Janus nanofiber, so the CL has aeolotropic conductivity. In view of this unique performance, we advance a new concept, namely “microcosmic aeolotropic electroconductivity”, which indicates that for a single constitutional unit, its interior has a key feature of aeolotropic conductivity. [(M//E)@F] microfibers array (designated as [(M//E)@F]-MFA) is obtained by using [(M//E)@F] microfiber as the constitutional unit to align directionally, and its fluorescence intensity is 11 times higher than that of the counterpart conventional composite microfibers array. In addition, the saturation magnetization of [(M//E)@F]-MFA can be adjusted from 2.16 to 27.41 emu·g−1 by varying the amount of CoFe2O4 NPs. The microcosmic aeolotropic electroconductivity can be modified by changing the contents of PANI in [(M//E)@F]-MFA. A new technique for constructing Janus nanofiber@fiber typed microfiber and array is established, which provides a pathway to construct other multifunctional micro/nanomaterials.