Fe₃O₄ Nanowire Arrays on Flexible Polypropylene Substrates for UV and Magnetic Sensing

The in situ growth of one-dimensional magnetite (Fe3O4) nanowire (NW) arrays with deterministic and tunable control over their orientation and morphology on a wide range of flexible and low heat resistance substrates is still a challenge. Herein, a facile method of controlling the orientation of Fe3O4 NW arrays on a polypropylene (PP) nonwoven fabric surface (PP-g-PAO/Fe3O4) through simultaneous radiation induced graft polymerization and coprecipitation processes was realized. We demonstrated a control over the orientation and geometric properties of coprecipitated Fe3O4 NWs via complex iron ion using amidoxime groups, which not only endow the material with high durability but also lead to the oriented growth of Fe3O4 NWs. The results showed that Fe3O4 NWs were only grown on the surface of the PP nonwoven fabric (length:diameter ratio ≈ 10), whereas the Fe3O4 produced in the solution exhibited a spherical structure under identical conditions. The PP-g-PAO/Fe3O4 composite presented a good saturated magnetization, superparamagnetic property, outstanding service life and recyclability, and exhibited two extraordinary sensing capabilities, i.e., UV and magnetic. This strategy can be viewed as the first example of in situ coordination induced growth of Fe3O4 NW arrays on the surface of a flexible substrate under mild conditions, and nanosensors based on PP-g-PAO/Fe3O4 hold tremendous prospects for multiparametric sensing platforms.