Comparative study of particle size and shape. (A) 2-D histogram of nanoparticle diameter correlated to 2-D circularity from TEM data. A circularity of 1 indicates a spherical particle, and 0.4 indicates a rod-shaped particle. More dense regions appear purple and represent larger populations. (a) Ag, (b) AgPEG, (c) Ag-Au and (d) AgCr nanoparticles. (B) Results of Kruskal-Wallis hypothesis testing on 3-D particle sphericity from combined AFM and TEM data.