405nm violet as use for a camping water disinfectant

[wittymoniker]

From a uv disinfectant solution website:

"It appears that 405 nm light can achieve inactivation of many bacteria; however, the fluences required for 1-log inactivation are very high (60 to 120 J/cm2)."
... for what they are calling 4-log inactivation, which is supposedly where 3-4 log bacteriologically inactivated water is certainly not going to make you sick:
"Using a 405 nm LED, the corresponding fluence was over 5,000 J/cm2."
My question for this topic as stated in the title is, at what rate does the water flow through this pipe or UV filter before, at a 5kW/cm^2 region, the water was disinfected? This high wattage makes me feel like the water is running through a pipe and it is just a large ray of light being sent through the middle of the pipe.

I am asking this because while I wait for my 1.6w 405nm laser, I wonder if, since the beam could be as small an area as a few square mm, then we can muliply the power by up to 50 or so when it comes to the square centimeter, equating in my ballpark of even up to 50J/cm^2 but in a tight tight spot, where the power density can zap through the bacteria while the beam moves and soon enough the whole cup is disinfected. That If the laser dot geometry is tight to one twentieth a square cm or less, and read as 1.6W it would be 1.6*20 J/cm^2 while going through water. I just now realise could have very powerful topical antibacterial activity that may even be useful in a wound or for sealing such a wound in emergencies., and then give the laser an extra few minutes for 1L of water while you 'stir it' with the laser, and what: voila, the water is disinfected?

Realistically I would expect it to be somewhere around 5-10W/cm^2 and no more so perhaps over no more than 2-3 minutes a cup of water can be cleaned to log4, if the cited article at the top was using water at some normal psi in a pipe that is running water to a sink while it uses a lamp inside the pipe.

I don't think anyone should try this for drinking right now but I made a post to see if anyone could make a test with a microscope or other method to see if their laser can reliably disinfect pond water at 405nm. I will be doing research with my college to see if our commercial 1+W 405nm lasers can do this; but it may take time.

For now, I will let you guys discuss. Feel free to move this into the laser science forum or duplicate it, mods.

I should be back within a couple weeks with my research, not to be taken as absolute whatsoever but might help us draw a conclusion.

 

[gazer101]

405nm is not quite energetic enough to directly destroy the DNA inside bacteria unless at a very high power density. But at that point the heat itself would probably do a better job of killing said germs... just go for 273nm, the FDA has already confirmed it to be effective

 

[kecked]

405 isn’t going to cut it 266 ish is needed and you have another two issues. The glass you use must pass the uv and two any sediment in the water will block the uv from getting through and I guess three you have no real idea it worked. Boil it. and don’t forget pollution so at least carbon filter it.

 

[wittymoniker]

I am not worried about bacterial DNA. THe DNA will die soon after inactivating because 405nm light does a lot of photochemistry which will equate to lightly microwaving the bacteria over time.


The article I posted said that while this UV is 1/100th the power of 280-260nm, it is much safer to use and if you have 1.6W of it in a small <1cm^2 beam you are going to be able to disinfect water before the end of the duty cycle. Assuming you have glass and water which is optically clear and sediment-free to begin with. I see no reason why it wouldn't work quickly when UV is used in pipes where water is always moving through. It clearly gave these quotes for short exposures.

 

[bostjan]

1. I'm not sure why so many people call 405 nm ultraviolet. Ultraviolet is defined as 10 nm to 400 nm. 405 nm is outside of the ultraviolet range. It's just plain old violet.

2. You could, in theory, disinfect with any wavelength of light if it was intense enough. 5 kJ/cm² does not sound like a lot to me, though. But it's been about 7-8 years since the paper everyone quotes for this was published. I wonder why this hasn't moved anything forward. Being able to disinfect surfaces at such a low cost and high convenience seems like it'd be something that would have got way more attention than it did.

3. If it kills both prokaryotic and eukaryotic cells, then I don't think it could be used in surgery. Maybe on skin, if 405 nm doesn't penetrate the epidermal layer, but even that seems risky, since there are a lot of unknown long-term hazards. At any rate, though, using it to disinfect a wound seems dangerous and impractical.

4. For water disinfection - this would need quite a bit more testing, so don't go drinking water out of your toilet bowl just yet! Remember that there is a pretty wide gray area in between "this shows promise" and "this is a proven method." We're barely at the "this shows promise" point. Maybe culture some e. coli in an aqueous solution and expose it to different periods of 405 nm light in a glass test cell, then place drops from each test cell into a petri dish and see if the e. coli reproduces or not. If it does, then the light didn't work on the e. coli. If you are careful enough, you could culture some other bacteria, and some different fungi. Then, once you have solid information from repeated tests, try it with some real samples. Wild bacteria and wild fungi and even wild protists are quite different from the ones we culture in the lab. Maybe the wild strains have some genetic disposition that allows them to tolerate higher levels of 405 nm light.

5. We know sunlight also has disinfecting properties. Leaving stuff outside in the sun, though, is not a good way to make it safe to consume, otherwise, we could drink any old water we come across outside and it would be safe. 405 nm light easily makes it's way to the earth's surface from the sun. I'm a little skeptical that this will work in real life to the point where it's applicable and practical, but the only way to know for sure is through scientific experimentation.

 

[wittymoniker]

okay yeah you caught me being too lasy to type it as -near-uv thanks @bostjan thanks for the post i will test it out tho and tell you how effective that really is, like i said it will completely alter the chemistry of the organic parts of the water

and if you didnt know they use 405nm in hospital disinfecting lamps rn

 

[Sowee7]

okay yeah you caught me being too lasy to type it as -near-uv thanks @bostjan thanks for the post i will test it out tho and tell you how effective that really is, like i said it will completely alter the chemistry of the organic parts of the water

and if you didnt know they use 405nm in hospital disinfecting lamps rn

ive only heard that they use 254nm lamps? where did you get that from?

 

[wittymoniker]

they sell 405nm disinfectant lamps and they proved it kills coronavirus so they were using them in hospitals

 

[wittymoniker]

ive seen them for sale and browsed past a few articles that were on like pubmed

 

[bostjan]

Sorry, I can't help but nit-pick: near UV, like near IR, refers to electromagnetic radiation just barely outside of the visible part of the spectrum, so 405 nm is still just plain old violet, not UV-C, not near UV, nothing like that. Near UV refers to wavelengths greater than 300 but less than 400 nm.

Perhaps I, personally, have some sort of defect in my lenses, because I have several light sources with peak emission in the 350-385 nm range, and they all appear bright but blurry to me. Even if I focus on the light source, the light appears out of focus. I suppose "normal" people have something in their lenses that blocks that light. 405 nm laser light, to me, doesn't have much of this effect.

I've been in plenty of hospitals. Certainly not enough to provide you with statistical data of any sort, but, anecdotally, I've never heard of any hospitals using 405 nm light to disinfect. And the only products I see advertised to disinfect at 405 nm are sketchy products from China. I'm not trying to discount the paper you posted, because I believe these are two independent ideas. Anyway, maybe I'm wrong and there are tons of hospitals disinfecting their PPE or whatever with 405 nm lasers, but it's something that, as a practice, is completely unknown to me as a career physicist who has worked in hospitals and clean rooms for decades. I've seen lots of equipment that uses 220-270 nm light to disinfect, though.

But, like I said, I'm incredibly interested in this. If you do your own project, I would love to see the results!

 

[djcmount]

Following. Also skeptical about 405nm being very useful at disinfecting compared to wavelengths below 400.

 

[mrsinbad]

FWIW, what I found:

"UVB has a mid-range wavelength measuring 280 nm to 320 nm and works with many of the photo initiators in use today. Like UVA, it is used for curing coatings, adhesives and inks but is also highly utilized for UV applications involving:

• Disinfection
• Sterilization"

 

[bostjan]

FWIW, what I found:

"UVB has a mid-range wavelength measuring 280 nm to 320 nm and works with many of the photo initiators in use today. Like UVA, it is used for curing coatings, adhesives and inks but is also highly utilized for UV applications involving:

• Disinfection
• Sterilization"

I don't think anyone is arguing whether or not you can develop an application of proper UVB to sanitize. It's pretty widely proven and already in practice.

The gray area here comes from the fact that the light in question here is 405 nm, which is 27% longer in wavelength than the top of the range you cited. There's also a big question about how much light intensity would be required in practice.

To put into perspective, if I had a television remote control that used a signal LED with a wavelength of 940-980 nm, would a 740 nm laser do the trick? I think the proper answer is no, because it's 27% beyond the edge of the range. You could rig something impractical to make it somehow work, certainly, but I don't think that makes the simple answer ever be "yes."

 

[kecked]

The energy gap is wrong to damage the dna EFFICIENTLY. Can it yes with power but why would you. Do it right and use iodine tablets And a filter. The other thing is even very small amounts of suspended solids will drastically drop the distance the light penetrates above the threshold needed and your contact time goes up tremendously. Eventually the input energy will be similar to just boiling it for a few minutes. This can be done but it’s not simple. Filter the water, pass through carbon to grab organics that will absorb the light, then irradiate it, and then add stabilizer like iodine or bleach to store. In the end you might as well filter/RO the water, iodine it or boil it. One day there will be cheap efficient 260-270nm leds. Until then I suggest you start traditional. There are kits you can buy with a water bladder to store and tablets. Was like 50.00. I got one when the war started. I should get the straws too. It’s a portable all in one that lets you drink right from a stream.

i just looked back at the thread. 5kJ/cm2. It takes 313kj to boil 1kg of water…..
1000 cubic cm so 313kj/1000cm3=.3kj/cm3. Take a slice so 30j/cm2. So it takes ALOT more energy to use uv than to just boil it. yes not exactly comparable for tons of reasons but it’s a ballpark. I seem to remember 4.14j/gram to convert from liquid to gas.

what could be a cool project instead is a solar still.

 

[The LED (& Laser) Museum]

Funny; I've always thought that 405nm was WAY too long in wavelength to inactivate most pathogens.

 

[WizardG]

Units people. Units. A joule is equal to one watt second. 5kJ/cm2 is 5000 watt seconds of energy per cm2.

Let's call your 1.6 watt laser 2 watts to make the math easy. 2 watts for 2500 seconds........... Yes, it'll work, but it will be in no way, shape, or form practical. The wavelength just doesn't have the energy/photon to do what you want to do in any reasonable amount of time.

The only luck I've had using 405nm light against pathogens has been using a defocused 200mW 405 to kill my toenail fungus.