Fig. 4. Scanning electron microscopy images of AuNSs synthesized by (a) 160 mM HEPES buffer and (b) 300 mM HEPES buffer showing the three-dimensional morphology of the MGNs. Transmission electron microscopy (TEM) images of AuNSs synthesized with varying HEPES concentrations: (c) 30, (d) 100, (e) 160, and (f) 300 mM. High-resolution TEM images of AuNSs with d-spacing indicating (g) the {111} facet in the AuNS core and crystal plane twinning and (h) growth along the 〈111〉 direction for the AuNS protrusion. The scale bar is 2 nm in both (g) and (h); reprinted with permission from ref. 48. Copyright © 2014 American Chemical Society.