Fig. 10. (a) Calculated normalized extinction CD, ε extin,CD/N NP, for optimized Au-NP helices with pitch = 25 nm. Other parameters: NP radius (a NP) = 5 nm and helix radius (R 0) = 12 nm. (b) Calculated normalized extinction CD at two selected wavelengths λ = 525 and λ = 555 nm. The selected wavelengths correspond to the extreme points of the CD spectra. (c) Calculated normalized extinction CD for 6-NP-per-turn helices with a variable pitch and a constant helical radius R 0 = 8.5 nm; number of NPs (N NP) = 13; and a NP = 2.5 nm. (d–f) Calculated normalized extinction CD for 6-NP-per-turn helices with various defects: a model of a perfect helix (d), the helix with one missing NP (e), and the helices with two missing NPs (f). The parameters are pitch = 19.2 nm, N NP = 10, a NP = 2.5 nm, and R 0 = 8.5 nm. Adapted with permission from ref. 119. Copyright 2011 American Chemical Society.
