Photonic nanostructures of nanodiscs with multiple magneto-optical properties†
Smart optical materials (SOM) that allow the tuning of multiple optical properties are of emerging interest for diverse applications in sensing, display and anti-counterfeiting. However, the existing studies are restricted to colloidal assemblies of one-dimensional building blocks, including nanorods and nanoellipsoids, hindering the further development of this system. Here we demonstrate the modulation of multiple optical properties by a single stimulus in crystalline colloidal arrays of two-dimensional magnetic nanodiscs. Small-angle X-ray scattering (SAXS) studies reveal that the magnetic field could align the nanodiscs along the field direction and induce the phase transition from a randomly oriented polycrystalline structure to a uniformly aligned polycrystalline structure along the direction of the magnetic field. Based on the magnetic orientation control, an external magnetic field can tune the photonic band gap and birefringence of the nanodisc assembly. This study not only brings new insight into the assembly and orientational control of two-dimensional magnetic colloids, but also expands the family of this novel type of SOM.