It’s chemistry video feature hour again.

Here’s a neat paper, from the Journal of the American Chemical Society and also reported in their magazine Chemical and Engineering News, including a really good video for you to click through to gaze in wonderment at.

If you can’t wait that long to find out what happens, let me help… The vid shows a sample of an innocuous looking powder, sitting in a dish. Then a UV light is shone on it, at which point a spatula appears from stage left, and starts smooshing the powder up. But wait! What is that I see happening? Why, there are some bright green streaks forming under the spatula’s point. It is very exciting.

Chemists at Hokkaido University, in Sapporo, made what appears to be a fairly simple gold-containing molecule, and found that when they scratched it, under UV light, it underwent a change and shone brightly – a phenomenon called mechanochromic luminescence. And hey presto, once a bit of solvent was added, the effect was cancelled out. This is because the molecule changes its arrangement when it’s scratched, and the interactions between molecules change so that the electronic state is altered – causing the UV-responsive yellow scratchy glow. Cool.