Surfactant-driven direct synthesis of a hierarchical hollow MgO nanofiber–nanoparticle composite by electrospinning

A hierarchical structure comprising decorated faceted nanoparticles (NPs) on hollow nanofibers (NFs) combines the advantages of large surface areas of NPs and anisotropic properties of hollow NFs. Such particular combinations are desirable for applications in batteries, dye-sensitized solar cells (DSSCs) and catalysis. Herein we report a facile surfactant-driven unprecedented fabrication of hollow MgO nanofibers (NFs) decorated with faceted MgO nanoparticles (NPs) via an electrospinning-thermal treatment process. The MgO NF/NP composite was achieved in one step by adding a cationic surfactant, cetyl trimethyl ammonium bromide (CTAB), to a solution containing a polymer and an MgO precursor followed by electrospinning and calcination of the electrospun fibers in air. Tuning of the MgO NP size and faceting of the NPs on the fiber surface was achieved by increasing the concentration of CTAB in the solution used for electrospinning. In particular, increasing concentration and order of CTAB addition to the spinning solution influences the MgO NPs decoration and coverage on the nanofibers, indicating the possibility that a well-defined choice of NP density can be achieved. The faceted particles show cube-, octahedron- and rod-like morphology depending on the growth rate of the 〈100〉 and 〈111〉 directions. Furthermore, by employing a mixed solvent (methanol + DMF) strategy, we were able to reduce the size distribution and control the shape of the faceted NPs only to octahedra. Moreover a tentative mechanism for the formation of hollow MgO NFs and faceted NPs using TGA and FTIR analysis has also been proposed. This new approach of surfactant driven electrospinning of a NP decorated NF composite will have a strong impact on various applications as it is simple, effective and straightforward.