A hierarchically structured Ni(OH)2 monolayer hollow-sphere array and its tunable optical properties over a large region

The fabrication of a hierarchically structured Ni(OH)(2) monolayer hollow-sphere array with the shell composed of building blocks of nanoflakelets is demonstrated based on a colloidal monolayer and electrochemical deposition. The morphology can be easily controlled by the colloidal monolayer and deposition parameters. Importantly, such monolayer hollow-sphere array shows a morphology- and size-dependent tunable optical transmission stop band. This stop band can be easily tuned from 455-1855 nm by changing the size of the hollow spheres between 1000 and 4500 nm, and also fine-adjusted by changing the deposition time. The array exhibits a nearly incident-angle-independent position of the stop band that 3D photonic crystals do not possess. This structure may have potential applications in optical devices, photonic crystals, and sensors for gas detection.