I have synthesized Cu2O nanoparticles & it's size determined from XRD data as 38 nm. I have analysed uv visible absorption spectroscopy, and from uv absorption data I found out bandgap by plotting Tauc's Plot. But the bandgap I got is 2.1 ev. Cu2O has bulk bandgap of 2.2 ev and when it comes to nanomaterial the band increases. But in my case the bandgap of nano Cu2O is even less than the bulk bandgap. What can be reason of this? Where did I go wrong? Please tell.
Hi Unniyarcha K.K
This is a very interesting observation. You may check the bandgap value by measuring the valance band (VB) and conduction band (CB) energy values of the synthesized material using the Mott-Schottky plot. This plot may help you to explain this behavior.
For the Mott-Schottky plot you may look at this article: Article Synthesis of mesoporous Fe/Al/La trimetallic oxide for photo...
I can suggest this from the best of my knowledge.
Waiting for the other answer from the RG experts.
Best of luck.
Regards
It is possible that the size you measured from XRD data is not accurate or that you did not account for the shape of the nanoparticles when calculating the bandgap. Additionally, there may be other factors impacting the measured band gap such as surface defects, or an incorrect Tauc plot formula. You can try repeating the measurements to see if there are any differences or try other methods such as scanning photocurrent microscopy or X-ray photoelectron spectroscopy
Subtract the instrumental broadening from the XRD peak width, then calculate the particle size. If the particle size exceeds certain limit then it behaves like a bulk material. If possible synthesis small Cu2O nanoparticles or reduce the Cu2O particle size (ball milling) and check the UV-Vis spectra.
Dear Unniyarcha K.K.!
First: 40 nm particles are big enough to have the bulk value of the band gap.
Second: did you check the accuracy of the band gap calculation from your
experimental data? I would say that 2.2 and 2.1 don`t differ in terms of the
experiment accuracy.
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