Raman signal in the range of 1106 to 1943 cm -1 was collected and integrated over 3 s and 30 s for SERS and Raman, respectively. For SERS measurements, six spectra were obtained for each sample, and the background signal was subtracted for each individual measurement prior to calculation of average and standard deviation. The enhancement factors (EFs) were obtained using the method described in Van Duyne et al. , where EF is defined as (ISERS/IRaman)•(CRaman/CSERS). IRaman is the Raman Intensity of 0.1 M CV (CRaman) on bare glass at 1620 cm -1 and ISERS is the Raman Intensity of 1 µM CV (CSERS) on the AuNR assemblies.