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nmaleki

You can buy UVC LEDs (255nm) for fairly cheap now. $20 or less

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Yes, however the safety-profile is quite the opposite to 222nm.

https://www.larsonelectronics.com/news/1763

https://uvmedico.com/far-uvc-light

that wavelength penetrates the skin. you need to be around 222nm for human safety

uviquity has prototypes of a 220nm solid state chip they’ll commercialize next year (we’re an investor). a single far-uvc photon will destroy the covid virus.

https://uviquity.com/

Cool technology, thanks for posting.

The current state of the art UVC (short wave, e.g. 255nm) LEDs have very low efficiency, compared to UVA (long wave, e.g. 365nm). How efficient are these 220nm solid state chips?

Do they emit other frequencies, or are they monochromatic?

The uviquity 220 nm SHG chips are super cool--they're perfectly monochromatic (though maybe with some blue light leakage) and I hear from their tech lead that they expect to get up to 10% WPE. I think that approach is definitely going to be relevant much sooner than far-UVC LEDs, but they're still early days, it's going to be a long road. Krypton-chloride excimer lamps are more or less the only game in town for commercial far-UV, at least for now.

Full report here if you want more solid state far UV info: https://www.convergentresearch.org/resources/convergent/soli...

This is Far-UVC (typically 222 nm). Regular UVC can cause eye damage.

And skin damage

Evolution has us covered.

https://pmc.ncbi.nlm.nih.gov/articles/PMC3010660/

Do you know a good source for finding the latest, most efficient LEDs for DIY projects?

Nichia is pretty top of mind for me as a solid supplier of 265-280 nm LEDs https://led-ld.nichia.co.jp/en/product/uv_top.html. Decently high output, decent lifetime (especially the longer wavelengths). There's also CrystalIS https://www.cisuvc.com/klaran-for-disinfection/ But there's tons

This review paper is from 2019, but it includes a good summary of basically everyone who's relevant to the field https://www.nature.com/articles/s41566-019-0359-9 The author used to keep an updated figure on his website but sadly it seems to be down, or have moved

SilannaUV has 230nm, 235nm and 250nm wavelengths, as far as I know the only supplier that does so https://silannauv.com/

I would be pretty careful with all of these wavelengths though. None of them are truly monochromatic far-UV. Use eye/skin protection when messing with them.

This is an affordable 255nm UVC flashlight (buy filter separately due to US patent bs):

https://convoylight.com/products/gray-c8-uvc-255nm-uvb-310nm

Pretty sure that's a UVB flashlight. There's absolutely no way that anyone is selling 255nm UVC that outputs much of anything for more than a few hours for $45.

A good 280nm chip is ~$100 (https://www.ledsupply.com/leds/uv-c-280nm-nichia-ncsu334a-le...), and it gets exponentially harder to produce shorter wavelengths the further down the spectrum you go. 270nm and 265nm chips are getting there, but 255nm is mostly a research area right now.

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