Solid Powder Cuvette Question

[BowenZheng]

Hi there,

I fixed my calibration setup and was successful with the liquid sample cuvette. Now, I'm moving onto a solid powder stage and had a few questions:

1.) I currently have silicon dioxide powder on hand, and was wondering if this was a reliable website to compare my spectrum to (https://ramanlife.com/library/silicon-dioxide/) or is this (https://sdbs.db.aist.go.jp/) the gold standard since I see you refer to it often. I couldn't find any other spectrums that would corroborate with the one given in the first site and the second site only has the IR spectrum, not Raman, so I can't use that one.

2.) Would you recommend packing the powder really tight rather than having it be loose with some clumps forming? I would think the former would be better to reduce scattering and improve the signal. I have a hydraulic press and die that I can use if that's a better sample preparation.

Best,
Bowen

[Luc]

I did not know about the link you gave. There are other online spectral database but they aren't free; reason for which I tend to stick to SDBS.

About the powder, I recommend you press it but not necessarily with an hydraulic press. I just use the back of a drill bit to get something flat.

It's not always mandatory, sometimes it works without. But in some occasions the signal isn't good with fluffy powders for some reasons (maybe there is some preferred direction outside the reception cone)

[BowenZheng]

Hi Luc,

I have another question surrounding my solid powder setup. I chose to mount my Raman spectrometer vertically instead of using the optical components.

IMG20241124185029 (1).jpg (4.38 MiB) Viewed 632 times

I got a good result for the Paracetamol sample

IMG20241125201906.jpg (9.15 MiB) Viewed 632 times

Though the resolution isn't quite as good since the peaks that are closer to each other are 'absorbed' to form a thicker peak.

Anyways, I tried doing a similar thing for silicon dioxide powder

IMG20241113213808.jpg (11.6 MiB) Viewed 632 times

But the quality isn't as good and it's shifted by a lot on the x-axis, so I was wondering if I am confused what specifically makes these 2 powders give spectrums that vary in accuracy.

[BowenZheng]

By the way, this the Raman spectrum for silicon dioxide for comparison

Screenshot 2024-11-28 at 2.54.56 PM.png (472.18 KiB) Viewed 632 times

[Luc]

I'm surprised about the low resolution of the paracetamol peaks despite you're using the higher quality laser.

If you take a spectrum of isopropanol do you get a sharp peak? If not it could mean that the laser is not operating at its best operating point (temperature and current)