Raman spectroscopy

[Loveall]

Question, in the post above capturing fluorescence (link below). Does the broad peak at 1900cm-1 shift from a 532nm laser tell us anything? Is it consistent with what would expect from DMT fluorescence? Could I use that to grossly check for psilocybin, etc?

I guess what I'm asking is there a database for broad fluorescent peaks for our favorite molecules? Thank you.

Raman spectroscopy - Collaborative Research Project - Welcome to the DMT-Nexus

 

[benzyme]

unfortunately, I don’t think anything can be extrapolated from a fluorescence peak. Some fully-integrated commercial systems
use algorithms to compensate for flourescence bands.

how did you get scattered bands? everything I scan with the probe shows up as 532nm, even with the notch filter. :?

 

[Loveall]

Not sure. I spent some time focusing the optical tube system as simulated in the ray tracer program. Maybe that helps, if out of focus the Raman signal may be weak?

I'd be happy to lend you the assembled optical tube and it's cuvette for troubleshooting purposes. You'd just need to screw in the SMA optical cable. Let me know if you want to check it out.

 

[benzyme]

no need, but that’s very kind of you. appreciate it.
but you just reminded me to get a cuvette holder, just bought it.

I loaded up all the parts, cables, stand, and laptop into a backpack given to me by my company
during Lab Week. So convenient. My coworker jokingly said I could set up at festivals.

 

[downwardsfromzero]

Food for thought from this video:
[youtube]

 

[downwardsfromzero]

Stumbled across this document, don't know if it's been referenced here already:

Forensic Science International, Volume 273, April 2017, Pages 113-123
Identification of new psychoactive substances (NPS) using handheld Raman spectroscopy employing both 785 and 1064 nm laser sources

Redirecting

Edit: linked to from this article, which interestingly mentions "synthetic prophetic libraries".

How's the project going?

 

[Loveall]

Stumbled across this document, don't know if it's been referenced here already:

Forensic Science International, Volume 273, April 2017, Pages 113-123
Identification of new psychoactive substances (NPS) using handheld Raman spectroscopy employing both 785 and 1064 nm laser sources

Redirecting

Edit: linked to from this article, which interestingly mentions "synthetic prophetic libraries".

How's the project going?

Thanks for the link.

The optical tube is giving strong clean signals for bulk toluene. Seems like the focusing and light collection with 2x light passes strategy worked with a simple and convenient self-aligned optical tube setup which we simulated first. The equations to understand the system and mirror angle setup checked out.

However, we need to update they system to longer wavelength as 532nm source laser causes large fluorescence for our favorite molecules as Benz predicted. For that we need a new optical laser filter and longpass edge filter, and I'm struggling to find a good longpass edge filter that is economical. Would be very helpful if someone could find a good one for a laser Raman system and post the link here.

Looking for something like this, https://www.ebay.com/itm/Optical-Fi...For-667-Laser-Clean-up-Sputtered/311901684396. Unfortunately seller is on vacation now.

I also got some Ag powder from China. Gonna see if that enhances Raman enough to get a measurable Raman structure in the flourescent spectra. That's a long shot, but gonna try it soon.

 

[downwardsfromzero]

I also got some Ag powder from China

What grade (mesh size, or sub-micron range) of powder did you get?

I guess you're aiming for something along the lines of what's described here: https://doi.org/10.1002/jrs.1250220904 - i.e. Surface‐enhanced Raman scattering (SERS).

Would be very helpful if someone could find a good one for a laser Raman system and post the link here.

I found this link, but maybe it's the same seller as your above link?

https://www.ebay.de/itm/312234986248

Details zu Optisch Filter 670EFLP 12.5 mm Rot und Ir Übertragung Emission von 665 Diode

Preis: EUR 21,22

It seems these things are sold for vehicle emissions testing, but since you've been looking into this more seriously than I have you've surely noticed that already.

 

[Loveall]

Yes, same vendor for the optics. Looks like he is back from vacation now - your post is very timely, thanks!

I got these 50nm AgNP (Silver Nano Particles). This is based on the attached paper (also attached a plot from the paper, green line is experimental fit to the SERS data, black like is theoretical).

Thanks for all your feedback and help downwardsfromzero.

PS: The link to the research you posted seems to have an extra comma at the end.

 

[downwardsfromzero]

extra comma

From the forum link auto-detect - and my sloppy typing!
Corrected.

I'll be having a look at how those Ag nanoparticles are made. This would be something to play with.

 

[no_thing]

Greetings,

I'm late to the party, but I wanted to suggest another option for the spectrometer. If you can live with 340-850nm, a Hamamatsu micro-spectrometer (available on a breakout from groupgets or seeed) runs around $400, and has good examples for calibration and processing using an Arduino for control/interfacing. It looks like you already have nicely functioning setups, but it might be easier for future builds to not have to worry about the optics on the sensing side.

Assuming a normal noise distribution, one would use the standard technique of averaging over some large number of samples to improve the S/N.

If you need data further into the UV, an unfolded Czerny-Turner configuration may work better than the crossed setup you're using due to lower stray light levels.

This is an extremely impressive project, and I'm following it with interest.

 

[Loveall]

Thanks for the input. On my side I still need to buy the filters and laser to go to the lower energy that (hopefully) avoids the fuorescence of our favorite molecules. It was pretty neat to at least get a toluene Raman spectrum with benz's help. Fun times.