Hi,
I usually estimate the band gap by Tauc plot from UV-vis absorption spectra of nanoparticles dispersed in methanol. However, I have noticed that as I dilute the dispersion, the Band Gap values change a lot, for instance more diluted dispersion take to lower band gaps. I have some cases where this variation is the range from 1.8 to 3.3 eV, which makes things hugely unreliable.
So, my question is: Is there any standard procedure, regarding concentration, or maximum absorbance value recommended, for obtaining the UV-vis absorption spectra before input the data on Tauc plot?
Notice that I am familiar to Tauc plots and how the extrapolation of tangent line can provide either the direct or indirect Band Gap. So, my question is not about how to use the Tauc plot itself, but how to obtain a reliable UV-vis absorption spectrum before you prompt the data in the Tauc plot.
Usually I estimated the Eg without the usage of solutions: just right on the dried powdered solid nanoparticles. I've never heard about such methods. Could you send me several articles where the methods similar to yours are described.
Absolutely agree with Michael Nazarkovsky. It will be very interesting to see some papers. I always use Tauc plot for thin films. I wonder how do you account for scattering in your case.
Why do you disperse it in methanol? why don't you try and take UV/Vis absorption on your solid nanoparticles? I normally use directly my powders for this characterization and the relevant Tauc plot measurements. It would be great if you could cite some references here that correspond to this measurement.
Good luck!
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