Darkest manmade substance

The darkest manmade substance is a black material made of gold nanoparticles and called "dark chamaleon dimers", which absorbs more than 99% of visible light, over the whole visible range. This means that material absorbs 99% of all rays of light with different colours, from the violet to the red, i.e., with wavelengths between 400 nm and 800 nm, reaching a maximum absorption of 99.2% for light with a wavelength of 497 nm (corresponding to a blue colour). The material also absorbs more than 98% of infrared light, i.e., rays of light not visible to the human eye, with wavelengths between 800 nm and 1200 nm. The material is made of gold nanoparticles of different shapes, joined together; more specifically, a nanosphere with a diameter of about 50 nm is attached to a nanorod about 100 nm long. The particular combination of nanorods and nanosphere gives the material this exceptional absorbance properties. The nanoparticles can be dispersed in water solutions and also deposited in the form of a thin coating. The material was made by scientists from KAUST (King Abdullah University of Science and Technology, Saudi Arabia), in a joint collaboration between Prof. Yu Han and Prof. Andrea Fratalocchi.

An ideal material that absorbs 100% of light is referred to as “black body”; to date, "dark chamaleon dimers" comes closest to being a perfect black body. Nanoparticles are particles with dimensions of nanometres (nm), where 1 nm is equal to 10–9 m, i.e. one billionth of a metre, or about 100,000 times smaller than a human hair.

This material is darker and more absorbent than the previous darkest material, Vantablack (made of carbon nanotubes), as Vantablack absorbs 99.96% at a 663 nm only if the light source is exactly perpendicular to the material; if the light source has an incident angle other than 0 o, the absorbance is lower of a few percent.

This material is thinner than Vantablack; in fact, Vantablack is 0.5–1 mm thick, while this is about 100 times thinner, at just 10 micron thick. This means that less material is needed to have such high absorption. When the same quantity of material is employed, the carbon nanotubes composing Vantablack absorb between 70%–85% in the visible and infrared wavelengths, while this material absorbs > 98%.