I recently used a Malvern Zetasizer on samples of Au nanoparticles in order to determine the size of the particles (we are looking for significant shifts in particle size between samples, and as such do not need perfect precision). Here is a screenshot of one of the intensity histograms the machine produced, and the Z-average that it gave is written in the text box below:
As can be clearly seen, the bars of the histogram are at an x value much larger than that of the z-average mean. This is the case for almost all of the samples we took. Why is this? What does it mean about the distribution of sizes in our sample?
Thank you for your time.