Thursday, December 18, 2014

Some Unusual, Non-UV Photochemistry

Recent articles have highlighted a couple of unusual photochemical phenomena in living animals. While your thoughts might be that the photochemistry is UV-induced, neither one does in fact depend on UV radiation.

The first was a report from a few weeks ago (Original article ($) - C & E News coverage (open access)) regarding humans that can see near-infrared (NIR) light. The researchers found that what was occurring was 2-photon absorption, a phenomenon I've discussed before (1 and 2), where 2 NIR photons, each with half the energy needed to cause a photochemical reaction, both activate the same molecule at the same time (or more accurately, within an acceptable time window). I'm not sure of the practical applications of this and I don't think I'm enabled to see NIR (I've been deep in mines with any lights on and the blackness is incredible. I never had any hints of NIR coming off my companions), but this is still pretty intriguing. I'm sure the military is already looking into applications.

Meanwhile back in the realm of the visible light, such light is usually thought of as being pretty innocuous, at least at the fluxes we experience in our normal lives. But it turns out that certain insects are susceptible to damage by blue light (open access article). These include fruitflies, mosquitoes and flour beetles. And this is not the result of exposing the critters to some souped-up light bulb that burns out 100x the normal amount of visible light. No, this was run with with fluxes that are the equivalent to those found outside the researchers lab in Japan.

Further, the researchers found that the wavelengths for maximum lethality varied with species. Maybe this is surprising for biological systems (or maybe not), but I've made the point repeatedly on this blog and in presentations that polymer degradation rates are wavelength dependent and show a peak at a unique wavelength. So this is yet another case of us duplicating nature (even if we didn't know it at the time).

I can't help but think that this might be a good part of the reason mosquitoes are never active in bright light, preferring to come out and attack in the deep woods during the day or anywhere else at night. I don't think the kill rate with blue light is fast enough to make this discovery into an effective alternative to DEET, but I know of one local organization with a $17 millions budget that should look into this for dealing with the critters here in the Twin Cities.

Previous Years

December 18, 2013 - Nitrile Gloves Are Not The Universal Glove!

December 18, 2009 - Some subtle, subtle surfaces


Anonymous said...

I'd hope that you weren't able to see NIR coming off of your friends in the coal mine, because they'd have to be about 2500C for you to do so...

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