I have synthesized Co3O4 nanorods, nanoparticles i have obtained two direct bandgaps according to my study ,many researchers have reported the reason as "because of two oxidation states and degeneracy in valence states Co3O4 has two direct bandgaps." can you please help me to understand this property better?
Thanks in advance!!
Dear Pavithra Murugesh
The following article evaluates the effects of two oxidation states of the catalyst on the bandgap. It might help you:
https://www.mdpi.com/2227-9717/8/9/1032/pdf
Hi Pavithra Murugesh
UV–vis diffuse reflectance spectroscopy is used to portray the optical absorption and also energy bandgap of a synthesized material. To find out the bandgap one of the well-known methods is Tauc's method. The conduction band (CB) and valence band (VB) edges were used to recognize the variation in band gap for synthesized samples. The following equation has been used to determine the CB and VB values. Ecb = X - Ec - 0.5Eg, where ECB is the CB edge potential; X is the electronegativity of the semiconductor, which is the geometric mean of the electronegativity of the constituent atoms, Ec is the energy of free electrons on the hydrogen scale (4.5 eV); and Eg is the bandgap energy of the semiconductor. The EVB value was obtained using the following equation Evb = X - Ec + 0.5Eg. If the charge (oxidation state) has an influence on the electronegativity then the VB and CB difference will also get influenced leading to a change in bandgap values. I can suggest from my side.
To get more information on these equations you may check doi.org/10.1016/j.jes.2019.09.004
doi.org/10.1016/j.apcatb.2017.03.055
Regards
you may get some info in
http://collaborations.fz-juelich.de/ikp/cgswhp/cgswhp12/program/files_batumi/14-08-2012/Parallel_Session_5/1_Kazimierz.Conder_Batumi.pdf
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