Intrinsic Design and Modulated Circular Dichroism of Inorganic Nanowire/Hydrogel Composite

Controlling the handedness and absorptive characteristics of chiral materials is essential for exploring new advances in the field of chiral sensors and catalysts. The deliberate architecture of the building blocks and their self-assembly process are critical factors for fabricating chirally active structures from achiral nanoscale components. Herein, the fabrication of multicomponent gel structures comprising magnetoplasmonic core-shell Au@FexOy nanowires embedded in a macroscopic titania nanocrystal network is demonstrated, which shows broadband absorption covering the ultraviolet-visible light spectrum while maintaining excellent porosity in the aerogel state. The effect of externally applied helical magnetic field is exploited to induce self-assembly of the magnetoplasmonic nanowires into chirally active superstructures. Furthermore, a second vector of symmetry is observed when the chiral hydrogel unit is rotated up to 45 degrees around the z-axis perpendicular to the light path, in which the measured circular dichroism intensity is modulated up to +/- 102% compared to those at 0(degrees). This study serves as a concept of designing optically active chiral 3D superstructures, applicable to optical filters, sensing devices, and chiral photocatalysts.

Automated summary

This study demonstrates the fabrication of chiral active structures from achiral nanoscale components by controlling the handedness and absorptive characteristics of chiral materials. The self-assembly of magnetoplasmonic nanowires into chiral active superstructures is achieved through the effect of an externally applied magnetic field. This concept can be applied to the design of optically active chiral 3D superstructures for optical filters, sensing devices, and chiral photocatalysts.