Transmission electron microscopy images. STEM Z-contrast (a, b, c) and HRTEM (d, e, f, g) images of the GNPs from the reaction of HAuCl4 and Na2S2O3. Top row shows Au particles synthesized by mixing 5 mL 1.71 mM HAuCl4 with (a) 2.2 mL 3.0 mM Na2S2O3 yielding a 750-nm NIR Peak, (b) 1.4 mL 3.0 mM Na2S2O3 yielding a 950-nm NIR absorption, and (c) 4.0 mL 3.0 mM Na2S2O3, which has no NIR peak and only one SPR band at 530 nm. (d, e, f, g) High-resolution TEM images of the typical species of the GNPs in the products: (d) cuboctahedron, (e) pentagon, (f) truncated triangle plate, and (g) colloidal gold particles.
Zhang et al. Nanoscale Research Letters 2012 7:337 doi:10.1186/1556-276X-7-337