I'm currently working with a Lambda 1050 spectrophotometer, my research group has a powder (which I'll call powder 1) sample that they would like to measure the band gap.
Perkin Elmer has an article on the subject called "Simple Method of Measuring the Band Gap Energy Value" in which they used an integrating sphere and got the BG value by just applying the strongest cut-off value on the graph into a simple equation.
We have been doing analysis of aqueous solutions of methylene blue ( which was in powder form prior to dissolution) and we have the same kinds of graphic spectrum showed in the article (Absorbance x Wavelength), they are very consistent and show the known peak of MB at 664 nm even for concentrations as low as 1,5 mg/L.
Now I'm wondering.. if I dissolve the powder 1 in water or any other solvent (since the lambda 1050 has the sample holder for the solvent alone, from which it deduces data to generate the graph), would I be able to determine the band gap value from the Absorbance x Wavelength graph that is generated?
or is the idea flawed at some prior point?
The absorption spectra of dry powder and its fine sol are almost the same (a minor differences occur due to the solvatation effects and scattering). If you manage to get a stable sol of your powder, you can easily determine its band gap based on the absorption spectra of the solution. The Perkin Elmer’s method is simple, but better use common graphical calculation (tangent line to Tauc plots), it's more correct. For example, see branch
https://www.researchgate.net/post/How_to_calculate_band_gapEg_of_Uv-vis_spectroscopy_from_absorbance_vs_wavelength
Best regards.
UPD: The big particles may cast a significant scattering in the sol, interfering the result. It needs some skill to select a significant site of the curve for tangent line (see enclosed).
The absorption spectra of dry powder and its fine sol are almost the same (a minor differences occur due to the solvatation effects and scattering). If you manage to get a stable sol of your powder, you can easily determine its band gap based on the absorption spectra of the solution. The Perkin Elmer’s method is simple, but better use common graphical calculation (tangent line to Tauc plots), it's more correct. For example, see branch
https://www.researchgate.net/post/How_to_calculate_band_gapEg_of_Uv-vis_spectroscopy_from_absorbance_vs_wavelength
Best regards.
UPD: The big particles may cast a significant scattering in the sol, interfering the result. It needs some skill to select a significant site of the curve for tangent line (see enclosed).
Thank you Dr. Shcherbakov, the information and link you provided will be very useful.
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