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Author: Subject: DIY Spectrometry Questions

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[*] posted on 20-8-2023 at 21:31
DIY Spectrometry Questions

I am interested in whether or not spectrophotometric reaction kinetics monitoring can be done using DIY methods. I have seen videos on Youtube and posts on this site about home-built spectrometers, and am wondering if such devices would be suitable for the task. So, here are my questions:

1. I recently read an article that claims that it is possible to use a smartphone camera to discern changes in the RGB values associated with the color of a card-reader's LED and from that, perform cryptanalysis to determine the encryption key used. This got me thinking: Suppose there is a reaction happening in a vessel the product of which has a visible color. Would it be possible to prepare some solutions of the product at different concentrations, use a smartphone to take pictures of the samples, find the RGB values associated with various concentrations of the product, and use that information to either determine the concentration of a substance in an unknown sample or determine the rate of a reaction taking place? While this approach seems like it would be useless for, say, determining the emission spectrum of a fluorescent light, I want to know if it can be useful for monitoring reaction kinetics.

2. A video I saw shows the construction of a spectrometer using some wood, a CD, and a webcam. Regarding this setup, I have several questions:

a. How sensitive is it to changes in incoming light intensity? Would a 1% change in absorbance at a given wavelength be detectable?
b. What is the "refresh rate" on such a setup? ie. once there is a change in incoming light intensity, how long would it take for the display to update?
c. Does the camera have to be angled at 30 degrees?

3. Are there any other DIY spectrometry apparatuses? If so, how would they compare to a "Proper" spectrophotometer used in a research lab?

[Edited on 21-8-2023 by Falvin]
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National Hazard

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[*] posted on 21-8-2023 at 06:29

The answer is yes to your first question. Yes, the setup could be useful for reaction kinetics measurements.
Regarding the third question the answer is most probably yes. There are probably amateur, home-made spectrophotometers out there. Actually, constructing one with modern electronics is not that hard at all if you know electronics and like to tinker with microcontrollers and some analog electronics (front-end for the photodiode/led/phototransistor sensor). I bought some such devices for USD 1-5 a few years ago but in the end I bought a small, portable digital spectrophotometer for say USD 50... It is a second hand one but working so no need to reinwent the wheel... ;)
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[*] posted on 9-10-2023 at 07:12

I'm also in the process of designing a spectrometer with a friend. You might wanna check out this component ( really that whole website, it has a lot of neat things people do group buys on.) The Hamamatsu C12880MA MEMS micro-spectrometer has a Spectral Response of 340 to 850 nm and Resolution of 15 nm in 288 pixels. If you're doing time series integration, each 512 channel pixel has a 4μs readout time giving you a total readout time of 2.048 ms (4 μs/ch x 512 ch = 2.048 ms). The wavelength reproducibility is ±0.1 nm to ±0.8 nm. That being said there are much cheaper ways using calibrated cmos censors from a phone or camera. I'd also look into FTIR and NMR. The YouTube channel Applied Science recently did a diy NMR setup.

[Edited on 9-10-2023 by abiogenesis]
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