Chiral Nanostructured CuO Films with Multiple Optical Activities

Chiral semiconductor nanomaterials with optical activity have intrigued magnificent attention due to their potential technological applications, but so far there have been no reports of chiral optically active CuO nanofilms. In this work, a facile chemical method to deposit chiral CuO nanoflowers on an activated quartz substrate is demonstrated. Three levels of chirality in CuO nanofilms are demostrated by structural analysis: tertiary helically arranged nanopetals assembled from secondary helically stacking nanoplates. Primary twisting chiral nanostructure of the nanoplate is believed to exist after careful examination on circular dichroism optical responses given by the CuO nanofilms. Originated from hierarchical chiralites, the CuO films exhibit both the electron transition absorption-based optical activity at the characteristic absorption bands and reflection-based optical activity arising from the long-range periodic structure at the circular Bragg resonance.