Why do things appear black or white? They appear black because they absorb all the colours of sunlight and reflect none while they appear white because they don’t absorb any of the wavelengths of the visible spectrum and scatter all. Did you know that a material made from carbon nanotubes holds the world record for blackness? This material when layered approximately to a thickness of one mm absorbs 99.8 percent of light!

But recently it has come to the notice that a nano-material made of gold and consisting of miniscule hammer-like shapes has succeeded in achieving nearly as much blackness. And what’s more… it was also discovered that with a small addition it can even reflect any colour that one wants to. Inspired by beetles, whose beautiful thin shells reflect all wavelengths of light and thus make them appear whiter than any artificial material, Andrea Fratalocchi at King Abdullah University of Science and Technology in Saudi Arabia; thought of discovering the phenomena that was just reverse of this beetle effect. In this quest, he designed a theoretical system involving a tiny concave shell attached to an infinitely long tube designed to guide waves. If it was practically possible to build such structure light when entered the shell and travelled along the tube would never be seen again. Fratalocchi then approximated this design with gold nanorods and using plasmonics (materials that bend light along different paths). At a thickness of a hundredth of a millimetre, he found that the material absorbed 98.43 percent of light. This is a very high level of absorption and implies that this material could be painted onto other surfaces to turn light into heat.

Yuri Kivshar from Australian National University in Canberra opines that gold being an excellent conductor would transfer heat more efficiently than carbon nanotubes. Moving further in the experiment, when a simple dye was added to this material, its behaviour changed almost drastically. So what it really did was: rather than absorbing light and emitting it as heat the material converted everything in the visible and infra red spectrum into the colour of the dye.

Based on the ongoing research Fratalocchi opines that if a greater amount of sunlight were focussed onto this material such that it surpassed the threshold energy it would be possible to capture a large portion of the sun spectrum and transfer it on a single colour this in turn, would certainly improve the efficiency of photovoltaic cells which are known to work best with some particular frequencies of sunlight.

Hope this chameleon brings about a good change in the field of solar power!

Author:Technology Blog

Author:Technology Blog