I would not expect the effects to be in the same ballpark. Bleaching is very harsh, to the point where I wouldn't want to put my hand in a jug of bleach. I could imagine holding my hand up to a strong light. Sure, it might get too hot or too uncomfortable eventually, but at least in my mind, I would expect it to be lesser (so long as we don't talk about a literal deathray lamp).

If you follow the links to the supplementary info it gives you intensity level, for example "The prepared dish was placed in a blue LED irradiation device and irradiated at 1.25 W/cm2 for 3 h."

As a reference, noon sunlight is very roughly 1000 W/m^2 or 0.1 W/cm^2, so this is pretty intense and I suspect would not be eye safe.

See https://pubs.acs.org/doi/suppl/10.1021/acssuschemeng.5c03907....

The abstract at https://pubs.acs.org/doi/10.1021/acssuschemeng.5c03907 mentions a power of 1.25 W/cm2

It's news to me that the sun is blue!

Jokes aside, I suppose it's novel in the sense that it can be achieved with artificial _blue_ light.

My understanding was that it was various forms of UV from the sun that caused "bleaching", whereas the paper points out that it is not UV in this case, and in fact, the UV can cause additional staining.

EDIT: Edited for grammar.

I am a common "poo-pooer" of bad submissions on here, and comments not in good faith

But this paper taught me something I had no idea about as a 33 year old. Also in the comment chain someone mentioned/brought up using peroxide/sunlight to clear up old yellowed plastics which is....monumental to some of my projects :)

Ultraviolet light is ionizing. Things oxidize and often whiten in sun because the UV light (the part of the UV spectrum as you go below ~315nm) ionizes and causes chemical reactions, in most cases by splitting O2 which is then charged O atoms that want to react with things.

445nm light isn't ionizing at any brightness, and shouldn't be catalyzing oxidation. Didn't look at it in detail but what is their claim on mechanism?

Don’t buy anything. Use the sun, for the moment it’s free.

https://news.ycombinator.com/item?id=45209124 mentions that simply putting the stained cloth under the sun works.

You can buy blue led strips just about everywhere.

Buy some diy flashlight kit. There's an entire community of people that build flashlights for fun and hence a ecosystem of parts.

Then put in the strongest 455mm wavelength diode you can find off Digikey that fits the kit parts.