Wanted - UV-C LED and/or Laser Diode - Page 1
Forum section: electronics / general

author: inuyasha10121
author_rank: Newbie
timestamp: December 16, 2015, 12:17:10 am
content: Hello there,I'm looking to see if anyone knows a reliable source for some Deep UV LEDs or Laser diodes. We have noticed an interesting phenomenon with a small molecules fluorescence characteristics, and want to study it using NMR. Unfortunately, this means that we need to excite the sample while it is still inside the NMR, and since NMRs use very strong magnets we can't really use a UV-Vis instrument source up close (We've considered running a fiber optic cable from the NMR to a source far away, but the following design seems easier). We've decided that it'd probably be best to mount a LED or laser diode to the tube, run some wires out, and excite the sample that way, or suspend a laser diode above the sample entry port and shoot the laser into the NMR through a hole in the top of the sample tube (Which is going to be a joy to align). We need a reliable source for some laser diodes (preferably) or LEDs that emit at 260nm, 275nm, and 280nm. These can be separate diodes, we don't necessarily need a tunable source that goes across that full range. If anyone could help us out, I'd really appreciate it.-Jon E.

author: thesgoat
author_rank: Contributor
timestamp: December 16, 2015, 12:26:49 am
content: http://www.nikkiso.com/technology/application.html

author: PedroDaGr8
author_rank: Super Contributor
timestamp: December 16, 2015, 01:11:30 am
content: Quote from: inuyasha10121 on December 16, 2015, 12:17:10 amI think you should abandon the LED in the tube idea. First off, how are you going to account for the spinning of the tube? In a standard NMR the tube is spinning at around 20-30Hz. This spinning is essential for clean easily readable spectrum. In a solid state NMR it is spinning at kHz speeds. I will assume you are doing standard NMR. Additionally, there is NO way you can have wires inside the NMR chamber. The magnetic flux will be OFF THE CHARTS. If the LED is inside the radio tube I imagine not only will your Z-shim go to shit, the induced current in the wire will likely be high enough to kill the LED. That is assuming that your tube doesn't go off balance and wreck the radio tube.

author: inuyasha10121
author_rank: Newbie
timestamp: December 16, 2015, 02:43:46 am
content: Yea, we aren't planning on spinning the sample because of the issues the wire would cause. We are going to be doing 19F-NMR, which usually gives some really good reporting, and spinning isn't required. When we do Protein 19F-NMR we don't spin the samples because bubbling typically occurs, and we manage to get pretty good results. Thank you for pointing out the induced current issue though, I completely spaced on it. The main concern I actually had with putting the LED in was that if there was any fluorine used in the manufacturing of the LED, or if we decided that we wanted to do C-F coupling experiments, the LED would screw up the spectrum results, so I'm really leaning towards mounting a lased diode above the sample inlet and shooting it down into the sample. As far as a potential fix to the current issue, do you think that using something like a LED-throwie setup would mitigate the issue? Theoretically, all the field lines should be parallel to the sample tube, so if the setup was aligned above the tube where the wires went in the same direction, and everything was inside the channel right above the sample rotor. I would expect that it would lessen the induced magnetic field generated. There would still be the issue of Z-shimming the system, but I might be able to get around that by pre-shimming the system, then attaching the LED. Not sure if that would work though, I still think the laser system would be the way to go.I'll run a quick experiment tomorrow with a junk LED and some lengths of wire to see if the LED pops when I move it closer to the magnet, or slide it down the sample inlet as if a sample were being loaded.

author: sleemanj
author_rank: Super Contributor
timestamp: December 16, 2015, 05:10:38 am
content: I have purchased high UV (390-400nm) 1W from this Taobao vendor before, they also sell these deep UV ones down to 260nmhttp://world.taobao.com/item/41232920060.htm?fromSite=main&spm=a312a.7700824.w4002-1152497255.110.zwO9zGI can't speak for the actual wavelength of what I got when I bought the high UV ones except that they were UV, they were in antistatic bags, labelled appropriately, and they did the job I needed.

author: PedroDaGr8
author_rank: Super Contributor
timestamp: December 16, 2015, 06:27:02 pm
content: Quote from: inuyasha10121 on December 16, 2015, 02:43:46 amSounds like an interesting project, after the banging my head I was doing yesterday fighting the damn NMR hardware I would welcome something interesting.I still believe a laser diode would be your BEST option, that being said, it is a lot more expensive. Alignment shouldn't be too much of an issue. At worst, you can use compatible fiber optics to bring the UV from the laser down into the tube.As for LEDs, I have looked in this range before (looking for 260nm and 280nm UV LEDs for creating a column detector). They are NOT cheap; if money is an issue, you might be able to convince them to send you some free samples since it sounds like you are at an academic institution.A few companies that make them:http://www.s-et.com/products.htmlhttp://www.hexatechinc.com/uv-c-led.htmlPlus a few others. I used some UV LEDs from Bivar in the past but I don't think they go down to UVC ranges.If you want to pulse your samples Horiba makes a pulsing system:http://www.horiba.com/fileadmin/uploads/Scientific/Documents/Fluorescence/NanoLED_Spec_Sheet.pdf

author: PedroDaGr8
author_rank: Super Contributor
timestamp: December 16, 2015, 06:42:00 pm
content: Quote from: sleemanj on December 16, 2015, 05:10:38 amLuckily, being he is apparently a chemist (or molecular biologist) he will likely have access to a mluorimeter. Turn the PMT voltatge WAY down and drop the LED in there and he can a good read on exact output spectrum.

author: Marco
author_rank: Super Contributor
timestamp: December 16, 2015, 07:14:21 pm
content: You don't happen to have a frequency doubled tunable dye laser available? I don't see how alignment really is much of an issue, although whoever is responsible for it might not like you attaching a reflector to the ceiling above his precious NMR machine.

author: kony
author_rank: Regular Contributor
timestamp: December 16, 2015, 08:39:06 pm
content: http://www.roithner-laser.at/Specialty LEDs, photodiodes, lasers, some of them can be purchuased even in bare die form. Recommended.Bewarned trough that output powers at such low wavelengths tends to be really phatetic.As for aligment issues - quarz fiber and ball lens for coupling might be reasonable. If specific profile is required in measurement cavity, fiber can be ground to act as lens.