The characteristic wavelength of ZnO is supposed to be ~380 nm. However, in this article1, the peak has been blue-shifted to 214 nm. This is quite similar to my sample where the peak is at 200 nm. In the article it is said that:
the blue shift may be due to the transition of electrons from the inner shell of copper to the outermost shell as time passes. It is possible that, due to aggregation and agglomeration, particle size increases and material settled down on the bottom of the container causing decrease in absorbance.
Could someone explain what this means?
Also, I did a UV-dr on the sample and it gives me a peak at 380 nm.
1: Structural and Optical Characterization of ZnO Nanoparticles Synthesized by Microemulsion Route. International Letters of Chemistry, Physics and Astronomy 2013, 14, 26-36.