Published on October 29th, 2015 | By: April Gocha, PhD0
Scared of the dark? Nanotechnology adds color to the blackest blacksPublished on October 29th, 2015 | By: April Gocha, PhD
Credit: Scabeater; Flickr CC BY-NC-ND 2.0
I am scared of the dark.
There’s just something about the lack of light to make everything eerie. It’s like the black night makes anything possible—normal objects develop into unfamiliar shapes, shadows creep across the ground, and rustling in the bushes suddenly signals someone or something lurking behind, plotting your demise.
But rather than an irrational fear, being scared of the dark is actually an evolutionary advantage—a holdover from the days when we humans were preyed upon by creatures further up the food chain, scientists speculate.
So whether you watch scary movies or brave a haunted house this Halloween, know that your fright is alright.
But to help demystify the dark, let’s bring science into the mix. So what is the dark?
Remember back to art class—black is the absence of color. It’s okay if you need a refresher here, because the American Chemical Society’s Reactions video series has just the thing.
Watch this quick video for a color crash course and to hear all about how nanotechnology is developing the blackest black.
Credit: Reactions; YouTube
While carbon nanotubes of the world’s blackest blacks are incredibly effective at trapping light, they can’t be tweaked to emit any color in the rainbow—but gold nanorods can.
Researchers at King Abdullah University of Science and Technology in Saudi Arabia are developing their own über black material, although this one’s not competing for a superlative achievement.
Their gold nanomaterial, which nonetheless rivals some of the blackest blacks, can reflect any color of choice with a simple addition of dye.
“Fratalocchi wondered if the effect could be reversed,” according to the article. “He designed a theoretical system that involved a tiny concave shell, attached to an infinitely long tube designed to guide waves. If you could build such a structure, light would enter the shell and then travel along the tube, never to be seen again.”
Fratalocchi and colleagues used that theory to design a nanomaterial composed of gold nanorods with accompanying attached nanospheres of just 30 nm in diameter, according to the paper’s abstract.
A coating of the material just a hundredth of a millimeter thick absorbs 98.43% of light. And because it contains gold, it can transfer that collected light as heat more efficiently than carbon nanotubes.
Beyond its blackness, what’s incredible is that the material can be fine-tuned to emit light of a single color—monochromatic emission—simply by adding dye of that color into the nanomaterial.
“This is achieved through the dynamics of light condensation in which all absorbed electromagnetic energy spontaneously generates single-color energy pulses,” the paper’s abstract explains.
The New Scientist article extrapolates the potential of such a shape-shifting black material. “If a lot of sunlight were focused onto the material so that it exceeded a threshold energy, ‘you should be able to capture a large portion of the sun spectrum and transfer it on a single colour’, says Fratalocchi. This could improve the efficiency of photovoltaic cells, which work best with particular frequencies of light, he says. ‘We have ongoing research in this direction.’”
The article, published in Nature Nanotechnology, is “Harnessing structural darkness in the visible and infrared wavelengths for a new source of light” (DOI: 10.1038/nnano.2015.228).
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