[honie]

The title is not misleading, and the golden layer formed is metallic water and not any of the metals used -- where electrons are delocalised/shared between water molecules. They have strong evidence that the layer is indeed metallic water and not something else:

> Experiments at a synchrotron in Berlin confirmed that the gold reflections produced the signatures expected of metallic water.

In my opinion, the ingenious part of the experiment is the following part, and I'm glad that they were lucky enough to find the right conditions:

> The key to avoiding an explosion, Jungwirth says, was to find a window of time in which the diffusion of electrons was faster than the reaction between the water and the metals.

Edit: added "in my opinion".

[verytrivial]

Ah, interesting thanks!

[honie]

I forgot to say that what you said is perfectly reasonable and not too different form my initial reaction. This is indeed very weird (but cool) science. :)

[gus_massa]

I agree. The original explanation is a good guess but it's not what is happening in the OP.

There is experiment to detect some sugars, that is somewhat similar to this alternative explanation (and unrelated to the experiment in the OP). More details in:

https://en.wikipedia.org/wiki/Tollens%27_reagent

Random quick video: https://www.youtube.com/watch?v=21PHoxlukME

NileRed video with more technical details: https://www.youtube.com/watch?v=nGmxHLHyUPc