Long wave UV Leds

[large_ghostman]

The longer wave or black light UV leds, does anyone know how much they degrade and over what kind of time scale? I am looking to use one to count FGP type proteins via a unit designed to pass a fluid through a special window.

What i cant find out is if there is much change in wavelengh if the led is on for say 10 seconds at a time, or if it changes after 6 months of use.

 

[crutschow]

Black UV is a short wavelength below visible. IR is long.
But your question is likely best answered by the LED's manufacturer.

 

[gophert]

Black UV is a short wavelength below visible. IR is long.
But your question is likely best answered by the LED's manufacturer.

He didn't mention IR.

Longer UV is ok to handle without protective glasses for short periods (like Black lights in a disco) or excitation of fluorescent dyes for black light posters). 375-400nm.
Shorter UV does create issues (254 nm and below).

Little Ghostman
The UV LEDs are simply white LEDs without the "phosphors" on the lens. Phosphors, in this case, are a brew of fluorescent pigments that emit a broad range of colors when excited with UV to make white light.

The UV LEDs are Inorganic and suffer very little breakdown over reasonable periods of time you mention.

 

[large_ghostman]

254 m is what we use to sterilize and some chromotography plates have a dye that will fluoresce at that wave length, we use a geologist dual tube lamp for this, you are spot on with what i meant, I was distinguishing between the shorter UV and the safer longer UV wavlenghs used, though for some reason I had 450nm in my head! but that likely me getting it mixed up. The type of FGP being used has to use the longer UV or the organism is killed off, the longer wavelengh is just enough to excite the protein and fluoresce, the plasmids for coding the FGP are inserted manually into the bacteria, population growth is then estimated using reflected UV in a special chamber.

We did use quatz curvettes but now have funny little plastic chambers with a window in them on the main tri port take off lines. The led packet says 420nm! Which i know is wrong!! So must be 400nm, these are a rough test before we buy the high quality Leds.

So from what your saying we simply use a known blank to 'zero' the reading each time we do a run, that seems like a reasonable idea then. My concern was them drifting off while being used, i have a UV/Vis spectrometer thats getting on, the white Deuterium bulb does drift over time and costs alot to replace, again though these are intended to be zeroed for each sample, the UV leds sound like its only needed each run and not each sample, that will save alot of time.

The shorter wave UV gives you 'arc eye' if you look at it long enough, ive had it a couple of times and its really painful!

 

[JonSea]

There was a story about a nightclub somewhere - maybe Korea - that inadvertly installed the shorter wavelength UV tubes. Many people suffered eye damage.

 

[unclejed613]

There was a story about a nightclub somewhere - maybe Korea - that inadvertly installed the shorter wavelength UV tubes. Many people suffered eye damage.

nobody asked why the place smelled like ozone when they were on? my grandparents had a UV tube lamp that was used for tanning. i was playing with it one day, and my grandfather was in the other room and smelled the ozone. i had found an old clock with luminescent markings on the dial, and holding it up to a regular light bulb wasn't working to activate the paint. i put it in front of the UV lamp for about 10 seconds, ant you could see the luminescence of the paint with the room lights on. my grandfather came in and said "don't look at the bulb when that's on, you're supposed to use goggles when it's running"... that one was a broad spectrum lamp, it's visible spectrum was bluish. it was a quartz tube (like a straight xenon flash lamp, only bigger), and i think the gas was mercury vapor, so it likely was emitting both long and short UV.

i found a picture online of one of these, digital cameras sure do strange things with UV light (this pic makes it look green)...

 

[gophert]

254 m is what we use to sterilize and some chromotography plates have a dye that will fluoresce at that wave length, we use a geologist dual tube lamp for this, you are spot on with what i meant, I was distinguishing between the shorter UV and the safer longer UV wavlenghs used, though for some reason I had 450nm in my head! but that likely me getting it mixed up. The type of FGP being used has to use the longer UV or the organism is killed off, the longer wavelengh is just enough to excite the protein and fluoresce, the plasmids for coding the FGP are inserted manually into the bacteria, population growth is then estimated using reflected UV in a special chamber.

We did use quatz curvettes but now have funny little plastic chambers with a window in them on the main tri port take off lines. The led packet says 420nm! Which i know is wrong!! So must be 400nm, these are a rough test before we buy the high quality Leds.

So from what your saying we simply use a known blank to 'zero' the reading each time we do a run, that seems like a reasonable idea then. My concern was them drifting off while being used, i have a UV/Vis spectrometer thats getting on, the white Deuterium bulb does drift over time and costs alot to replace, again though these are intended to be zeroed for each sample, the UV leds sound like its only needed each run and not each sample, that will save alot of time.

The shorter wave UV gives you 'arc eye' if you look at it long enough, ive had it a couple of times and its really painful!

I cannot confirm that an LED will be more stable than an D-lamp but you'll also have o confirm that the power supply is stable over time as well. By the way, warming up the old Spec-20 spectrophotometer was critical to stabilize the lamp intensity.

 

[large_ghostman]

I cannot confirm that an LED will be more stable than an D-lamp but you'll also have o confirm that the power supply is stable over time as well. By the way, warming up the old Spec-20 spectrophotometer was critical to stabilize the lamp intensity.

Lucky the results have a good margin, i was more worried about not having enough power and therefore not seeing many glow. The nutrient we use causes harm if used in excess.

 

[kubeek]

The longer wave or black light UV leds, does anyone know how much they degrade and over what kind of time scale? I am looking to use one to count FGP type proteins via a unit designed to pass a fluid through a special window. What i cant find out is if there is much change in wavelengh if the led is on for say 10 seconds at a time, or if it changes after 6 months of use.

I doubt the wavelength will drift due to ageing, but the luminous output will. How much? That is either for you to test and measure if it is important, or better to ask the manufacturer of the particular diode you are using.

However the exact wavelength will change with the temperature of the die, so the first few second will most likely be different than longer on-time results when the temperature gradients stabilize. I think the temperature dependence should be the same like laser diodes have, so it should not be hard to get a ballpark figure out of google.

 

[large_ghostman]

I doubt the wavelength will drift due to ageing, but the luminous output will. How much? That is either for you to test and measure if it is important, or better to ask the manufacturer of the particular diode you are using.

However the exact wavelength will change with the temperature of the die, so the first few second will most likely be different than longer on-time results when the temperature gradients stabilize. I think the temperature dependence should be the same like laser diodes have, so it should not be hard to get a ballpark figure out of google.

I am likely to use a Chinese special so datasheet unlikely, however the luminous output change is easy to cater for, all i need to do is calibrate it for each use, just push plain water in and take a reading. That will give me the baseline each time.

I am not too sure how useful it will be in a full scale unit, but the lab scale test ones are fairly low capacity, so i avoid taking samples from the reactor without good reason. It maybe one of the others working on this has a better idea, although its based on the system that got built, this one is going to be heavily modified. I asked the question thinking ahead a bit, but i have a different problem with the initial stage at the moment.

Really must take that stir motor apart and get an idea what voltage it runs at!! Also i need something like a really small 5V pump that takes airline (aquarium) sized silicon tubing. Ebay has some 12V ones but 5V would be better if I can find one.

 

[schmitt trigger]

Like all LEDs, longevity and reduced drift can be improved by operating the LED well below its maximum ratings. Both from the current and ambient temperature.

 

[large_ghostman]

Current is 5ma, thickness of the cell it is used on is only 4mm from one side to the other on the small ones and 55mm on the larger type

 

[The Electrician]

Get one of these and run it at substantially less than rated power: https://www.mpja.com/Ultraviolet-LED-10W-365nM/productinfo/32614+OP/

 

[unclejed613]

i used to have a collection of lasers from defunct blu-ray players. while technically not UV (405nm), they do cause fluorescence in materials that fluoresce under UV-A light. Samsung optic assemblies were often very easy to extract the laser from, as they are glued on the outside of the optic assembly with 2 "dots" of epoxy. the forward voltage is about 4V, but i wasn't concerned about the voltage much, as i always drove them with a constant current source set at 35mA. the emission pattern of a blu-ray laser is fan shaped (narrow along one axis, wide on the other) which is determined by the shape of the laser crystal. while LEDs emit from the top surface of the crystal, lasers emit from one of the sides of the crystal. since failures in blu-ray players are rarely caused by a failure of the laser itself, it's likely that a "dead" blu-ray player still has a functioning laser in it.