I have prepared a aqueous nanosol of sub 10 nm copper particles. I have analysed it in UV-Vis Spectrophotometer. I have got different curves (different peaks) for same suspension of different concentration. Even when I repeated with the same sample, the peak had shifted slightly. Can you please explain me all these phenomenon and also the reasons for these bathochromic, hypsochromic, hyperchromic and hypochromic shifts ingeneral and also in my cases? Thanks in advance. I have attached my obtained curves.
I am not sure I am understanding your numbering system, but it looks like the highest concentration samples are showing strong scattering, probably from aggregation of the NPs. The fact that your baseline is rising with increasing concentration is a sign to me that you have some serious artifacts/ issues with the system such as scatter.
Additionally, spectrophotometers become increasingly sensitive to stray light as the absorbance increases. I was always taught to keep the absorbance below 1.0 to reduce this issue, though more sophisticated spectrometers do have better light exclusion and can accurately measure higher absorbances.
Agree with Louise above. Stray light artifacts manifest itself very significantly at absorptions of 2 or more. Even with sophisticated spectrophotometers, at an A=2.0 only 1% of the incident radiation is transmitted thru the sample. Interesting to note that the ~600nm peak does not shift, Instead of diluting the sample (which may induce a different equilibrium of species) have you tried using cells with a shorter path length (PL). Since the absorption is proportional to the PL cells with very small PL (e.g. 1mm or less) can enable profiles of highly absorbing solutions.
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