a concentrating effect from the evaporation of the solvent. As
a control, reactions with varying starting concentrations were
performed in trioctylphosphine solution in a flask. At concentrations
similar to those used in the growth of the nanoprisms on
substrates (0.11 M), in the absence of any concentrating effect
from solvent evaporation, nanocrystal growth stops as hexagonal
plates with diameters slightly less than those of the substrate
grown structures (Supporting Info Figure S1). When additional
precursor material was injected to the reaction solution at a later
time, the final aspect ratio of the hexagonal plates was higher,
further confirming the need for additional precursor material to
continue the growth along the top and bottom crystal faces.