What was your signal-to-noise ratio, which is correctly defined as the fitted height at zero divided by the root-mean-square fluctuation in the measured data around the fitted curve? Did you try several measurements on the same sample to see if the apeparance was repeatable, or if the appearance was due to statistical fluctuations in the spectrum?

Please post your result and explain how it was obtained. What DLS algorithm was used? What were you measuring? Any sample 'preparation'? Cannot provide a detailed specific reply without more information.

On the whole, it can be said that the particle size distribution in suspension is not uniform. In this case, several measurements are recommended.

Million thanks for all your contributions.