UV LED's for sterilization???

[PhotonWrangler]

Another fluorescent mineral collector here! Yes, the vast majority of them need a shortwave UV source to make them glow. My favorite is franklinite/willemite. I have a couple of small pieces of this and it looks just amazing under UVC.

Those shortwave UV leds look interesting. Maybe we can get a group buy together.

 

[slebans]

Single-chip UVC LED from Crystal IS Achieves 65mW cw at 260nm
http://www.ledinside.com/news/2013/3/uvc_led_crystal_is_20130325

"By employing die thinning and encapsulation techniques, we were able to increase the photon extraction efficiency to over 15%," says founder & chief technology officer Leo Schowalter. Furthermore, improved thermal management and a high characteristic temperature resulted in low thermal roll-off up to 300mA injection current with output power of 67mW, an external quantum efficiency (EQE) of 4.9%, and a wall plug efficiency (WPE) of 2.5% for a single-chip UVC LED emitting at 271nm. "By fabricating our LEDs on our home-grown aluminium nitride substrates, we continue to set the pace of what is possible for the combination of highest efficiencies and longest lifetimes in the 250–280nm wavelength range, far surpassing diodes fabricated on sapphire," Schowalter adds.

 

[Mattaus]

I looked into UV LEDs for water sterilization a few weeks ago and came to the conclusion that they were just too expensive ($260+ for a single LED!) for my purposes. If a group by can get that price down considerably I'd be very interested in a few...

- Matt

 

[yumbrad]

There have been some interesting results that show, for some bacteria at least, that the 365/385 nm region (which have cheap available LEDs) is sufficient to sterilize given sufficient power and time of exposure. Links:

http://link.springer.com/chapter/10.1007/978-3-540-36841-0_323#page-1
http://www.bioelectromagnetics.org/bems2010/supp_data/P-A-140.pdf

I'm gonna give it a try with a smattering of 361, 375, and 385 nm LEDs, since it's a fairly cheap experiment (and a lot easier to integrate into my little system than a fluorescent tube). I wonder if the efficacy of the 385nm is simply due to the FWHM bleeding down into the actual effective range...

 

[slebans]

There have been some interesting results that show, for some bacteria at least, that the 365/385 nm region (which have cheap available LEDs) is sufficient to sterilize given sufficient power and time of exposure. Links:

http://link.springer.com/chapter/10.1007/978-3-540-36841-0_323#page-1
http://www.bioelectromagnetics.org/bems2010/supp_data/P-A-140.pdf
...

Thanks for the interesting links. Makes you want to move that lamp containing a CFL bulb just a tad further away!
;-)

 

[Mattaus]

So with sufficient time 385nm UV-A LEDs can do the job. Given the low power of these ELDs (15mW I read in one paper) even at a typical Vf of 6V, you're talking about very little current which should allow a UV flashlight to last quite some time...I might do a bit more reading.

 

[RetiredFireCaptain]

I have been looking for UV-C leds to use in my vehicle's air conditioner. with the low power consumption and germicidal effects it would make for a healthier atmosphere in my car. I had a germicidal light installed in my home AC unit and it made a noticeable difference.

 

[PhotonWrangler]

I have been looking for UV-C leds to use in my vehicle's air conditioner. with the low power consumption and germicidal effects it would make for a healthier atmosphere in my car. I had a germicidal light installed in my home AC unit and it made a noticeable difference.

Interesting. Do you happen to know if the UVC lamp is of the newer, low-ozone envelope design? The newer ones have a surface treatment on the glass that allows germicidal wavelengths to pass through while blocking the primary ozone-producing wavelength of 185nm.

 

[RetiredFireCaptain]

Interesting. Do you happen to know if the UVC lamp is of the newer, low-ozone envelope design? The newer ones have a surface treatment on the glass that allows germicidal wavelengths to pass through while blocking the primary ozone-producing wavelength of 185nm.

TO be honest I do not know much about the ozone aspect of the LED's. There is so little info on UV LED's that I have had a difficult time learning. The one we had in our home was florescent and tied to the blower motor with a relay. It worked well and as proof before the light was in place the AC would kick in and you would get a wiff of mildew. After the light there was no smell of mildew. That is par for the course in South Florida.

 

[slebans]

Interesting. Do you happen to know if the UVC lamp is of the newer, low-ozone envelope design? The newer ones have a surface treatment on the glass that allows germicidal wavelengths to pass through while blocking the primary ozone-producing wavelength of 185nm.

For the past 6 years I have used UV in both my Water and Air handling equipment. I have not heard of this Ozone issue before today. Thanks for the heads up. Hopefully I can find compatible bulbs for the housings.

 

[RetiredFireCaptain]

So does anyone know of a reasonably priced LED in the UV -c range that is available for the general public to purchase? Especially one that is not so fragile?
When I was a young paramedic working part time in the hospital, A maintenance man installed an 8' UV tube in the desk above the triage area. Two of my coworkers sat at the triage area for 12 hours when they finally realized what was going on. They were out sick for nearly a week with severe burns and I there was great concern about retinal burns. The light was in a desk partition that was less than three feet from them.

 

[Anders Hoveland]

I'm not sure how practical it would be, but frequency doubling optics are also a possibility. The frequency doubling optics in a green laser pointer has a relatively high efficiency of 25%. This could allow normal vissible frequency LED chips to be used, with the advantage of longer life, possibly even lower cost for higher power outputs.

Typically sterilization requires higher frequency UV (short wave), and I am not aware of any LED chips that can acheive sterilization frequencies.

So with sufficient time 385nm UV-A LEDs can do the job.

I doubt it. It would certainly not be a reliable way to sterilize equipment. This wavelength is not much shorter than vissible violet light (405nm).
One could also say that "with sufficient time" blue LEDs could be used to kill bacteria.
http://www.gizmag.com/blue-light-kills-bacteria/26026/

 

[Lontong]

so the conclusion is we are still waiting on 260 Nm cheap led

 

[Mattaus]

Pretty much. They do exist, but they are very expensive ($300+ each) and even then they won't sell direct to the public.

Sent from my Galaxy Nexus using Tapatalk 2

 

[KDM]

TO be honest I do not know much about the ozone aspect of the LED's. There is so little info on UV LED's that I have had a difficult time learning. The one we had in our home was florescent and tied to the blower motor with a relay. It worked well and as proof before the light was in place the AC would kick in and you would get a wiff of mildew. After the light there was no smell of mildew. That is par for the course in South Florida.

That smell is called the "Dirty sock syndrome". Heat activates the smell of mold/mildew spores. It also happens with heat pumps in the winter when the unit goes through a defrost cycle. The evaporator coil becomes damp during defrost because the unit is actually in cooling mode. Once defrost mode terminates and heat is applied to the coil it causes the odor. In your case the heat is building up in the off cycle. Once it cools back down no more smell. The UV light is killing the mold/mildew growing on the coil.

 

[Anders Hoveland]

I did find this:

Recent research has shown that commercially available UVA LEDs (365 nm) are already effective disinfection and sterilization devices.
(Mori, M.; Hamamoto, A.; Takahashi, A.; Nakano, M.; Wakikawa, N.; Tachibana, S.; Ikehara, T.; Nakaya, Y. et al. (2007). "Development of a new water sterilization device with a 365 nm UV-LED". Medical & Biological Engineering & Computing 45 (12): 1237–1241.)

Still, I think shorter wavelengths are more effective at sterilization (and more damaging to human tissue oo: )

 

[PhotonWrangler]

I did find this:

Recent research has shown that commercially available UVA LEDs (365 nm) are already effective disinfection and sterilization devices.
(Mori, M.; Hamamoto, A.; Takahashi, A.; Nakano, M.; Wakikawa, N.; Tachibana, S.; Ikehara, T.; Nakaya, Y. et al. (2007). "Development of a new water sterilization device with a 365 nm UV-LED". Medical & Biological Engineering & Computing 45 (12): 1237–1241.)

Still, I think shorter wavelengths are more effective at sterilization (and more damaging to human tissue oo: )

I didn't think that longwave UV (365nm) was capable of breaking down molecular bonds like shortware UV can, but then I'm not a phd.

 

[slebans]

I didn't think that longwave UV (365nm) was capable of breaking down molecular bonds like shortware UV can, but then I'm not a phd.

The issue is one of time. In comparison to shorter UV wavelengths, the longer UV wavelengths take too much time to achieve similiar levels of disinfection. For the majority of air and water disinfection processes - there simply is not enough time to accomodate the longer UV wavelengths.

I read up on this issue several months ago but I cannot remember if the longer UV wavelengths - even given sufficient time - can achieve the same levels of disinfection across all of the commonly targeted bacterial and viral organisms.

 

[Anders Hoveland]

I didn't think that longwave UV (365nm) was capable of breaking down molecular bonds like shortware UV can, but then I'm not a phd.

It is not, but there are some bonds that 365nm can break apparently. Having a bit of chemistry background, once one gets into blue/violet regions of the visible spectrum, the light is energetic enough to start effecting some chemical changes, at least with some of the more sensitive chemicals, particularly pigment molecules. But you are right, 365nm is not energetic enough to directly damage DNA.

 

[RetiredFireCaptain]

BUMP! Anyone have a fresh insight on this thread?