Actually I want to know the value of exponent (n) in Tauc relation for Au nanoparticles (among n values 1/2, 2, 3/2 and 3 corresponding to the allowed direct, allowed indirect, forbidden direct and forbidden indirect transitions, respectively).
No, I did not knew about that. I never calculated band gap, and I have not a good idea about band gap. Recently, in some paper I saw the formula of calculation of band gap for silver nanopartilces and then I search the same for gold nanoparticles but did not get any results.
Thanks for the information.
However, I remember that soimeone insisted that he experimentally have found bandgap in gold nanoparticles with n=1/2 and Eg about 3 eV. It looks suspicious, but in some sense the partial bandgap may exist. On the background of continual absorption between overlapped valence and conduction bands additional strong subband may exist, and it will be seen as a step on the Tauc plot
Aleksandr wrote > he have found bandgap in gold ...
Probably he is wrong. The absorption edge of gold nanoparticles in the visible region is governed by the surface plasmon resonance, which is not considered in Tauc's theory. Application of the Tauc's plot to metal nanoparticles is meaningless. You can plot your data, but you cannot find any physical quantities such as bandgap energy.
Hiro, it was not I who observed bandgap in AuNPs. I don't remember the reference, but they have found narrow region in Tauc plot where relation used by Tauc is correct with n=1/2 and Eg=3 eV. In my measurement made today, oppositely, this is not seen.
HI, Aleksandr.
"Hiro, it was not I who observed bandgap in AuNPs."
I am sorry for my confusion.
> In my measurement made today, oppositely, this is not seen.
Even though your data of Au NPs are well fitted by Tauc plot, you cannot say that the Au NPs have a bandgap.
I mean that in my today's data no signs of bandgap are seen, and I did not even tried Tauc plot for them. I see plasmonic resonance at 530 nm and sometimes additional resonances
tauc plot is used to calculate optical band gap for semiconducting materials only it does not hold for good conductor like gold.
For bulk gold surely, but for NPs? And for very small NPs?
From temperature dependence of conductivity, one can make out whether gold nano particles of prepared size is semiconductor or metal. If metal, no need to worry about band gap.If semiconductor, then only Tauc plot will be useful.
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