Page 47

COMPUTER , ELECTRICAL AN D MATH EMATICAL SCIEN CE AN D EN GIN EER IN G DIVIS IO N

100 nm

The shimmering colors seen on the wings of some beetles arise from a physical structure on the micro and nanoscale that has evolved to scatter light for a colorful appearance. The beetle species Cyphochilus in particular has wing structures that make them the whitest known insect. The researchers used the Cyphochilus wings to develop a perfect light absorber based on the inversion principle. A structure that inverses the properties of white beetles will be black and absorb light. This structural variation of the beetle structure consists of a gold nanorod to which a gold nanosphere is attached. The nanorods behave like tiny antennas that pick up light at all colors from the environment. As the light passes through the rod, it gets trapped in the nanosphere, where it bounces back and forth until the light is completely absorbed. The absorption capacity of the structures is about 26 percent higher than that of carbon nanotubes, the strongest light absorber identified. The high light absorption has applications for energy harvesting, explained Andrea Fratalocchi of the Computer,

Electrical and Mathematical Science and Engineering Division, who led the collaborative research team along with Yu Han of the Physical Science and Engineering Division.

“Hydrogen can be a game-changing technology with a system that is totally clean, abundant and renewable, and that can be used on demand and stored in large amounts.” “We are already employing these structures in the context of water desalination and they showed world record efficiency performances,” he said. They can also be used as catalyzers for chemical reactions or for the production of biofuel from sunlight. The structure can also emit light under specific conditions. If excited at one particular color — such as green — that

green light condenses and the structures emit red light in a very narrow region of the energy spectrum. This region corresponds to the minimum energy wavelength where light can spread out across the material. The main advantage of the structures is their extremely high light absorption. Fratalocchi pointed to the possibility of their structures being used for hydrogen production, as hydrogen is a versatile and efficient energy storage material. “One of the greatest current energy challenges is that it cannot be stored in large quantities which means we need to produce vast quantities of energy even if we do not consume it all,” explained Fratalocchi. “Hydrogen can be a game-changing technology with a system that is totally clean, abundant and renewable, and that can be used on demand and stored in large amounts.” 1. Huang, J., Liu, C., Zhu, Y., Masala, S., Alarousu, E., Han, Y. & Fratalocchi, A. Harnessing structural darkness in the visible and infrared wavelengths for a new source of light. Nature Nanotechnology doi:10.1038/nnano.2015.228 (2015).

I S S U E O N E 45

KAUST

The wings of Cyphochilus, the whitest known insect, provide the conceptual framework to develop the blackest material in the world.

KAUST Discovery - Issue 1  

From curiosity to innovation

KAUST Discovery - Issue 1  

From curiosity to innovation

Advertisement