Figure 9: Optical extinction spectra of solutions of AuNRs with an aspect ratio of 3 prepared by adding (a) 40 μL of 1 mM sodium citrate and (b) 0.5 mL of 40 mM CTAB 5 min after the addition of 60 μL of 1 mM sodium citrate. The times in (a) and (b) are the time intervals after the addition of sodium citrate and CTAB, respectively. The unchanged spectra in (b) with time indicate the end of growth of end-to-end-connected AuNRs. Reproduced with permission from [32]. Copyright 2008 American Chemical Society.