Ultraviolet, germicidal.

[Externet]

There is solid factual claims for ultraviolet light to be germicidal, and industry devices providing such,

at around ~250 nm wavelenght.

 

Would the usually fluorescent tubes usually used for this have the same action if the light source is instead, LEDs ? (at the same wavelength)

If the emmissive power of LEDs is inferior; would longer application time compensate to yield same results ?

[CharonY]

Yes, as long as intensity, exposure time and wavelength are in the right order of magnitude it will work. How it is achieved is of secondary nature.

[Moontanman]

There is solid factual claims for ultraviolet light to be germicidal, and industry devices providing such,

at around ~250 nm wavelenght.

 

Would the usually fluorescent tubes usually used for this have the same action if the light source is instead, LEDs ? (at the same wavelength)

If the emmissive power of LEDs is inferior; would longer application time compensate to yield same results ?

 

 

Do you know of LEDs that radiate at 2537 angstroms? (germicidal light is as close to 2537 as possible) I have designed several UV sterilizers, built several as well... LEDs are an interesting possibility...

[swansont]

 

 

(germicidal light is as close to 2537 as possible)

 

Why?

 

I suspect that it's simply that this is simply what the lamps emit, because they use mercury, and it works. Not that there's something special about being near 254 nm, or that a shorter wavelength would be less effective.

[CharonY]

I have LEDs in that wavelength for imaging purposes but they probably would not be suitable for your application. There are manufacturers out there (found just by googling), but I have no idea how expensive they would be.

Typically they are a bit longer (270-280 nm) but that would not make a whole lot of difference for germicidal purposes.

 

crossposted

Edited February 12, 2016 by CharonY

[Externet]

 

 

Do you know of LEDs that radiate at 2537 angstroms? (germicidal light is as close to 2537 as possible) I have designed several UV sterilizers, built several as well... LEDs are an interesting possibility...

A while ago a search found several vendors/manufacturers of claimed germicidal ultraviolet LEDs. Most of them at high prices, and did not save much data. But at that exact wavelength do not recall.

Like ----> http://www.qphotonics.com/UVTOP-LEDs/

 

Others are

----> http://www.leduvlights.com/

----> http://www.hexatechinc.com/uv-c-led.html

----> https://leddev.wordpress.com/2007/11/29/finally-germicidal-uv-leds-for-the-rest-of-us/

Cheaper? ----> http://th-led.en.alibaba.com/product/610391032-214075392/260NM_Germicidal_UV_Led.html#!

----> http://th-led.en.alibaba.com/product/612438487-214075783/265nm_Germicidal_UVC_LEDs.html#!

 

From CharonY response, LEDs should yield same results as traditional UVc sources.

 

Am after long strips to permanently leave installed inside along airconditioning ducts to make environments less prone to mold buildup. As previously found prices high, I opened a thread wondering if combining cheap 650nm and 400nm LEDs could yield some 250nm light.

( http://www.scienceforums.net/topic/93463-frequency-additionsubstraction-by-mixing-for-light/ )

 

Swansont opinion of other near wavelengths being also effective, will probably go in hand of which germ is killed better by which wavelength.

Edited February 12, 2016 by Externet

[Arete]

I just visited the local water treatment plant (phage discovery!) and found that they've switched from chlorinating effluent from the plant, to sterilizing using UV.

[Moontanman]

 

Why?

 

I suspect that it's simply that this is simply what the lamps emit, because they use mercury, and it works. Not that there's something special about being near 254 nm, or that a shorter wavelength would be less effective.

 

 

Actually there is some truth to what you say, UV light is absorbed by various proteins at different wavelengths 2357 being a trade off between penetration of cells and clear water. Too short and it is stopped by water not to mention the glass envelope of the bulb, too long and it stops being effect at denaturing proteins, length of exposure is also relevant.

 

https://en.wikipedia.org/wiki/Ultraviolet_germicidal_irradiation

 

 

 

UV light is electromagnetic radiation with wavelengths shorter than visible light. UV can be separated into various ranges, with short-wavelength UV (UVC) considered "germicidal UV". At certain wavelengths, UV is mutagenic to bacteria, viruses and other microorganisms. Particularly at wavelengths around 250 nm–260 nm,^[7] UV breaks molecular bonds within microorganismal DNA, producing thymine dimers that can kill or disable the organisms. It is a process similar to the effect of longer wavelengths (UVB) producing sunburn in humans. Microorganisms have less protection from UV and cannot survive prolonged exposure to it.

[CharonY]

The assumptions of a maximum around 260 nm is based on the adsorption maximum for purified DNA in liquid. The actual germicidal effect varies quite a bit. For coliphages were more sensitive to about 214 nm, Bacillus spores closer to 265 and Staphylococcus somewhere around 270.

 

In most cases anything between 200-280 is considered germicidal for practical purposes, though.

[swansont]

Actually there is some truth to what you say, UV light is absorbed by various proteins at different wavelengths 2357 being a trade off between penetration of cells and clear water. Too short and it is stopped by water not to mention the glass envelope of the bulb, too long and it stops being effect at denaturing proteins, length of exposure is also relevant.

 

https://en.wikipedia.org/wiki/Ultraviolet_germicidal_irradiation

 

IOW there's nothing about this specific wavelength that one should strive for.

[CharonY]

I think it is only because 253.7 nm happens to be one of the strongest emission lines of mercury-vapor lamps. It has little do with the application itself.

Incidentally much of the older experiments were conducted with what happened to be easily available in the lab...

Edited February 12, 2016 by CharonY

[Externet]

So there is no hope that these 4 cent cheap ~400nm emitters be somewhat germicidal And if somewhat, who knows which germ among thousands will be affected.

 

----> http://www.ebay.com/itm/5m-600leds-120LEDS-M-3528-UV-Ultraviolet-395nm-No-Waterproof-LED-Strip-black-PCB/141665925394?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D35314%26meid%3Df1a639cdd9934c3190b3b1adbfa6a275%26pid%3D100005%26rk%3D1%26rkt%3D6%26sd%3D131333499089

[Moontanman]

IOW there's nothing about this specific wavelength that one should strive for.

 

 

To be honest I do not know, I do know that it was stated to me when i was designing UV sterilizers that this was the idea wavelength. I do know that allowing the water to touch the bulb lessens efficiency of the lamp by shifting the spectrum toward longer wavelengths, It cools the lamp off too much so we used quartz sleeves to isolate the bulbs from the cooling effects of the water or what ever fluid you are using, also much shorter and the wavelengths do not penetrate deeply into the water.

 

Trade offs in many directions..

So there is no hope that these 4 cent cheap ~400nm emitters be somewhat germicidal And if somewhat, who knows which germ among thousands will be affected.

 

----> http://www.ebay.com/itm/5m-600leds-120LEDS-M-3528-UV-Ultraviolet-395nm-No-Waterproof-LED-Strip-black-PCB/141665925394?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D35314%26meid%3Df1a639cdd9934c3190b3b1adbfa6a275%26pid%3D100005%26rk%3D1%26rkt%3D6%26sd%3D131333499089

 

 

Considering those wavelengths are used to promote coral growth, probably not..

My idea was to use teflon tubing to wrap the bulb in a coil to increase both bulb efficiency and contact time... It was a double coil, I had intended to apply for a patent, I still have the original drawings, I was injured in a boat wreck and was out of commision for about 18 months and lost the thread of my idea for several years and never followed up...

Edited February 13, 2016 by Moontanman

[CharonY]

I think in most lab water systems an UV lamp is surrounded by water behind a quartz sleeve. But I think I have heard of coiled FEP tubing surrounding a bulb.

[John Cuthber]

Here's an odd thing to post.

If you google

"French knitting" "uv reactor"

you will find it brings up an ISO stadard for measuring formaldehyde.

A coil tends to spring apart too much.

[Moontanman]

I think in most lab water systems an UV lamp is surrounded by water behind a quartz sleeve. But I think I have heard of coiled FEP tubing surrounding a bulb.

 

 

That was my original idea!