UV LED's for sterilization???

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phreeflow

Newly Enlightened
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Jan 8, 2008
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Hi All,

Thought I'd revisit the great folks here at CPF in hopes that you some of you geniuses (seriously) could help me answer this question.

I've seen people use Ultraviolet lights to sterilize various things such as water. So....I'm wondering if I could use UV Led's to accomplish the same thing.

What I'm confused about is what part of the Ultraviolet lights makes it able to sterilize things? Is it the wavelength, spectrum, frequency, color, etc, etc.

Please enlighten me!!
Thanks all!!!
 
phreeflow said:
Hi All,
What I'm confused about is what part of the Ultraviolet lights makes it able to sterilize things? Is it the wavelength, spectrum, frequency, color, etc, etc.
Click to expand...

The color of light is directly related to its wavelength. Or to its frequency. (These two are directly related to each other and are based on the speed of light through a vacuum). Raising the frequency shortens the wavelength, and lowering the frequency increases the wavelength. Typically, though, we discuss the wavelength of a particular light, rather than the frequency.

254nm UV has (in the UVC range) is particularly effective in sterilization, because it breaks up the DNA in microorganisms. It has a quantum energy of 4.9 electron volts per photon.

254nm LED's are somewhat rare, though, and usually mercury vapor lamps are used to make germicidal lamps.
 
DNA has the property that it absorbs light around 260 nm very well. This means that if you provide enough light at 260 nm then the DNA will suck up too much energy and eventually break. The genetic information in bacteria and viruses is then destroyed and the bug dies.

UV-Disinfection therefore depends on the frequency (the closer to 260 nm the better), the intensity (lots of light) and the fact that the bugs need to be exposed to the light (clear water is perfect).

All I know is that right now there is quite some research done to actually develop LED based UV disinfection.
 
The Steripens use a flourescent tube.

UV LED sterilization isn't economically feasible yet because the LED's that operate in the correct nm range are very expensive.
 
If you want to tinker, you can buy a little 4 watt germicidal tube that fits in a those battery operated fluorescent lamps.

The light produces some ozone and can break down/yellow some plastics (hold a piece of polyethylene over it and notice the odor) and make certain minerals glow. Hold your hand over it for a second and smell. You notice the burnt smell from the radiation breaking down the oils on your skin. The radiation from the light is ionizing so can be considered dangerous. Protect your eyes using a filter. Clear plexi will work. Clear glass lets wavelengths above 310nm through so is not completely safe.
 
MattK said:
The Steripens use a flourescent tube.

UV LED sterilization isn't economically feasible yet because the LED's that operate in the correct nm range are very expensive.
Click to expand...

Interesting.. I seem to remember digikey carrying tiny UV tubes at one point. I was tempted to do an EPROM eraser with one, but never bothered with it.
 
Kestrel said:
My deepest and sincerest apologies, but I just couldn't resist:

Yes. ;)
Click to expand...

:sigh: Yeah, yeah...whateva...I never said I knew anything about this stuff. I'm a NOOB :naughty:. Go ahead and take your best shots :poke:and get it off your chest.

However, I do have a specific application I'd like to experiment with and I need your help.

When you say expensive, just how much are these 260nm UV LED's and where can I get them? If I'm understanding you all correctly, as long as the light source puts out enough light at around 260nm, then it should be able to disinfect organics...am I right?

If that's the case, could I just paint/coat these LED's with something to get it to output only 260nm? Thanks again fellas...:twothumbs
 
Phreeflow,

LEDs produce light of a specific range of wavelengths based on the substrates used and the transition energy therein. Essentially then, a red LED produces red light, it isn't like a light bulb being filtered. White LEDs and some less commonly coloured ones do use a phosphor coating to absorb the coloured light produced by the LED and radiate at a different wavelength (colour); the problem with this being efficiency, the output after the phosphor is less than before. In addition, producing a higher energy light (shorter wavelength, high frequency, more UV) from a lower energy one (i.e. frequency multiplying, albeit in fractions) would mean that the output would be very low.

It isn't really possible to do what you are after with any ease, the best option would be to look at the cost of the correct diodes. I think the Nichia ones in the region of 260nm are quite good, I have one at 265nm (from memory) but they output is reasonably low and the cost was high (around £10).

In air, the main germicidal element from UVc is formation of ozone; it is a free radical and serves to denature proteins quite viciously, hence killing organics.

It wouldn't, however, surprise me if they have made 260:280nm LED based specs for analysis of DNA/RNA ratios though.

Andrew
 
cdosrun said:
LEDs produce light of a specific range of wavelengths based on the substrates used and the transition energy therein. Essentially then, a red LED produces red light, it isn't like a light bulb being filtered. White LEDs and some less commonly coloured ones do use a phosphor coating to absorb the coloured light produced by the LED and radiate at a different wavelength (colour); the problem with this being efficiency, the output after the phosphor is less than before.
Click to expand...

Thanks for the great info Andrew. The light that I'm after doesn't necessarily need to be high output. It will only be about a cup or so of liquid that I'd like to disinfect so I'm hoping that maybe 1 or 2 leds would work in such a small volume.

You brought up an interesting point that I was considering. Would it be possible to coat the LED's with some sort of paint or put the LED behind some sort of lense to get the right wavelength??? Even if the output dropped, couldn't I then just use multiple LED's to get the sterilization?

Thanks
 
drmaxx said:
DNA has the property that it absorbs light around 260 nm very well. This means that if you provide enough light at 260 nm then the DNA will suck up too much energy and eventually break. The genetic information in bacteria and viruses is then destroyed and the bug dies.

UV-Disinfection therefore depends on the frequency (the closer to 260 nm the better), the intensity (lots of light) and the fact that the bugs need to be exposed to the light (clear water is perfect).

All I know is that right now there is quite some research done to actually develop LED based UV disinfection.
Click to expand...


I looked around and found a company producing UV LEDS in the 390-405nm range. Are these too far off from 260nm to be effective in sterilization.

thanks again!
 
Yes. You need to find them in the 260nm range - I think Nichia is your best bet but they're scary expensive if you can even find a source to sell you small quantities.
 
+1. Even those 365-385 UV nm money/crime scene detectors miss the mark by a country mile; not even close.
Steripen only work for virus and bateria. So, it WILL take care of Giardia (back packer's diarrhea, since it is a bacteria). They will NOT neutralize things like: household chemicals, pesticides, petroleum spills, heavy metals. What I am afraid of is that during a natural disaster, someone will take one of those money detector things, zap a cup of contaminated water for a minute, and figure it is now safe to drink. NOT. Not only is the wavelength totally wrong, it won't take care of all those nasty chemicals :sick2: even if it were of the correct wavelength.
 
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Hi all,

I just got off the phone with SSC, Nichia, and Cree.

Apparently, Cree has decided not to make anymore UV dies from what I am hearing. They've pushed it back for one year but it doesn't seem likely that they'll be carrying that product anymore (but don't quote me on it). In any case, they were 390-405nm.

Nichia still has 365-385nm but no longer carries anything in the 260nm range. BTW: I couldn't believe the prices. This led, #NCSU034AT-E costs over $200! While NSSU100a is more reasonable at around $1-$2.

SSC doesn't even deal with these at all. One of their branches Seoul Opto Devices may carry them but it's not worth a call to Korea.

Bottomline: Like Jerry said above, don't drink water "sterilised" by one of these LED's...totally wrong frequency. UV LED's at shorter wavelengths are as MATTK put it, way too expensive to be economically feasible for sterilisation.

Thanks to all for the education and input!! This has got be one of the best forums!:rock:
 
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