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Article Synthesis and Characterization of Polyvinyl alcohol /Polyani...

Optical band gap of the PANI, PPY and PPY–PANI composite films deposited on substrate, were calculated from the intercept on energy axis obtained by extrapolating the linear portion of the Tauc plot of (ahn)2 vs. photon energy (hn).

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DOI: 10.1039/c6ra07103a

DOI 10.1007/s10904-016-0439-y

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Dear Liaqat Ali,

The PANI band gap denotes the energy between HOMO and LUMO and can be determined from the absorption coefficient according to:

α(ν)hν = B (hv− Eg)m

where,

hν is the energy of the incidence photon,

h is the Planck constant,

Eg is the optical band gap energy,

B is a constant (disorder parameter) dependent on composition and independent to photon energy.

m is the power coefficient with the value that is determined by the type of possible electronic transitions, i.e., 1/2, 3/2, 2 or 1/3 for direct allowed, direct forbidden, indirect allowed and indirect forbidden respectively.

The direct allowed band gap of PANI nanoparticles can be evaluated from the plot of (α(ν)hν)2 versus energy (hν) and by extrapolation of the linear portions of curves to the energy axis for (α(ν)hν)2 = 0.

You can also go through following research articles:

01. http://downloads.hindawi.com/journals/ijps/2013/307525.pdf

02. https://pdfs.semanticscholar.org/a65d/5bd9ec5e54ac969c904c96b4db892dac05cc.pdf

03. https://pubs.rsc.org/en/content/articlelanding/2016/ra/c6ra07103a

I hope I have answered your question.

With Best Wishes,

Samir G. Pandya