Posted in chemistry, engineering, physics

Carving colors into gold nanoparticles

From the MIT Technology Review Physics ArXiv blog. Apparently it has been traditionally hard to get metals to offer up anything other than their natural color; you could only create different colored metals by mixing different metals with it, for example…

But now there’s another way thanks to some interesting work by Jianfa Zhang at the University of Southampton and a few pals. Their idea is to carve a different type of repeating pattern on to the surface of a metal.

These patterns are smaller than the wavelength of visible light. Instead of causing the light to interfere, they work by changing the properties of the sea of electrons in the metal–in particular its resonant frequency. This alters the frequency of light it absorbs and reflects.

This is the same technique that researchers have been using for some time to build invisibility cloaks . The idea is that by carefully building repeating patterns of subwavelength structures, researchers can tailor the way a “metamaterial” can steer light.

But instead of creating 3D structures that steer light as it passes through the material, Zhang and Co. carve the relevant structures onto the surface to control the way light is absorbed and reflected.

Visit the ArXiv blog for more details…

All I keep thinking is I’m glad there are lasers now that can do that for you; doing it the old-fashioned way would be waaaay too tedious for even the most skilled metal craftsman.



Beth Kelley is a writer and researcher with an overall interest in how people engage with and are impacted by their environments and vice versa. This has manifested itself in many ways, by looking at creativity, playful spaces and environmental enrichment, sustainability, design research, and integrative and collaborative models of learning such as through play and hands-on learning.