Raphael ThysSynthetic gold (not the new type), made in a laboratory, is pretty much the same as the natural version. Alchemist-hp/Wikimedia Commons; CC BY-SA 3.0
Gold is amazingly weird. For one thing, it's now thought that much of it came from aftermaths of the collisions of two super-dense neutron stars. Some of this atomic gold, sprayed across the cosmos, managed to coalesce under gravity, get trapped in a newly-formed Earth, undergo a suite of geological processes, and ultimately pop up at the surface.
Its considerably epic cosmic journey is certainly something to marvel at, as is the fact that it's useful for so many things besides jewelry. Now, as spotted by New Scientist, we’ve made a new form of gold that’s golder than ever before, and it's bonkers.
There’s no other element quite like gold, and it’s all down to its electrons. ZMEScience has a great explainer in this regard; although there’s plenty of detail to dive into, the long and short of it is that gold absorbs a lot of the lower wavelengths of visible light, i.e. the blues.
That means we’re left with the remaining hues, which form a gold color. Other elements don’t do this, with the exception of caesium, for similar wavelength-eating reasons.
The second key point is that gold is a Noble metal, meaning it’s inert: boringly resistant to corrosion and oxidation. It’ll remain golden over the millennia, unlike plenty of other important metals – copper, say – which quickly corrodes as the days go by.
So how could we possibly make gold even more golden, then? Making gold in a laboratory has been done before, but to accomplish this particular task, we’d have to fiddle with its chemical properties to make it even less reactive to the world around it than it already is, all without altering its wavelength-absorbing properties.
Tricky stuff. Fortunately, back in 2015, the seeds of success were planted.
Back then, a team, led by the Centre for Nano and Soft Matter Sciences in Bangalore, India, did some witchcraft. They chucked some gold chloride into a furnace and heated them at 220°C (428°F) for half an hour alongside the cacophonous tetraoctylammonium bromide. This produced elemental gold that formed microscopic, bumpy, elongated lumps.
These microcrystals may not sound like much, but this new study by much of the same team has poked them around a bit, and they’ve found that they pack quite the visual punch. In order to find this out, though, they had to bombard it with some pretty nasty stuff.
In a paper entitled “Nobler than the Noblest”, they explain that there are in fact some things that gold can be chemically attacked by. Normal, solid gold can be annihilated, so to speak, by a combination of nitric and hydrochloric acid named “aqua regia”, for example.
Mercury, perhaps an equally curious and bizarre metal, normally reacts quite dramatically with gold too. If you want to get rid of your gold, these options are pretty good bets. This elongated, microscopic, crystal form of gold, however, put up quite the fight.
Unless hyperconcentrated aqua regia was used, they survived, and – as reported in the Angewandte Chemie paper – the gold had “practically no interaction” with the mercury. That means that this gold type, forged in a lab, is furiously resistant to chemical changes, more than conventional gold.
The team suspect that the weird shape of their gold means that the electrons are arranged oddly, in “unconventional crystal lattices”, which makes them more resistant to external chemicals.
So there you have it: Humanity has created a gold more golden than that shaped by the geological forces of our entire planet. Or, as the team put it, their “unconventional gold is undoubtedly nobler” than the real deal. In your stupid face, nature!