Could you clarify what type of spectra is this (Absorption? reflection? Raman?, UV-Visible?), ?   What are the coordinates units?  It is hard to answer your questions without sufficient information. 

Could you clarify what type of spectra is this (Absorption? reflection? Raman?, UV-Visible?), ?   What are the coordinates units?  It is hard to answer your questions without sufficient information. 

I am so sorry. Its UV-Vis absorbance spectra of iron oxide nanoparticles dispersed in water. 

Dear Aadhinath,

i think that the absorbance wavelength is about 205 nm. so for get band gap use from relation: bandgap=(hc/lambda) that lambda is absorbance wavelength .

All the best,

Abbas

Thanks Abbas for your input. Some paper refer maximum wavelength has to be taken for calculation and some paper refer to take cut off wavelength for calculation. So I am confused..

Dear Aadhinath,

my skill is semiconductor nanoparticles and wavelength related to maximum peak is for band gap calculation.what is your meaning  about cut off wavelength?

Dear Aadhinath,

please see PV for more information.

Here you can find good explanation and band gap calculator,

http://www.instanano.com/characterization/theoretical/uv-vis-spectroscopy-band-gap-calculation/

you can use Kubelka Munk method,

there is some details on my paper:

Article Hydrothermal-assisted sol–gel synthesis of Cd-doped TiO2 nan...

In my opinion the best way is just follow the following link:

https://www.youtube.com/watch?v=KIfaVTfHMZc