A Infrared spectrophotometer DIY

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Building a DIY infrared spectrophotometer for organic compound analysis is feasible but presents challenges, particularly in signal reception and monochromator design. The optimal wavelength range for analysis is between 2.5 µm and 25 µm, with suggestions to explore thermocouples, thermopiles, or pyroelectric detectors for sensing. A simpler FTIR design with fewer moving parts is recommended, and using a high-resolution bar scanner can enhance detection capabilities. However, creating a comprehensive database for spectrum peak identification remains a significant hurdle, as commercial options are costly. Overall, while DIY spectrophotometry is possible, it requires careful consideration of components and data management.
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Hello everyone gathered here, I am passionate about chemistry and practical physics but the analysis of organic compounds is beyond my wallet and myself. So I want to build a spectrometer for functional group analysis and compound fingerprinting. The most commonly used range was from 2,5um to 24-25um (Wavenumber 4000 to 400 cm–1) And now the biggest problem will be receiving the signal and splitting the signal to be as monochromatic as possible.That's why I would like to ask how and what to make/buy monochrator. And what sensor would be best, thermocouple or something else
 
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Back in the day when I worked on CO2 lasers (@ 10um), thermopiles, thermistors, etc. were the only practical sensor. IDK, maybe there's something more exotic than just measuring heat now, but it won't be a normal semiconductor junction, especially at 25um.

Check out pyroelectric detectors too. IIRC, they weren't great for average power. OTOH we were at 100's of watts, so YMMV. 25um is still a problem, I think.

Ask Google about deep IR detectors, they'll know more than us, I think.
 
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While it may not work for far infrared a "bar scanner", 1 pixel wide, are DIY. By beam spreading lens and/or mirrors, or just increased distance from the diffraction grating to the bar scanner (reduced intensity) will increase the resolution. It should do near IR okay, and maybe get into the mid IR, depending on brand of bar scanner. Get 2000 dpi bar scanner. Or more, not a 300 dpi or even a 600. Used is cheaper for your first model. Find instructions on several websites/pages. I did. Get a 1 foot bar scanner, not a 1 inch. A discarded page scanner can be disassembled for it's bar scanner. The instructions to make an Arduino to read the bar scanner is online as well.

I think your greatest problem will be creating the database. There are some free ones but they are incomplete. The commercial spectrum peak identification databases are expensive, when I priced them 5 years ago, at over 2,000 USD. At that price, might as well buy the device that comes with the software and database.
 

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