Fig. 2. (a) SERS spectrum of dye 14 (10 μM) analyzed with HGNs (SPR recorded at 720 nm) and KCl (30 mM). The spectrum has been background corrected. (b) SERS particle dilution study for dye 14 with HGNs and KCl over the concentration range 1.93 nM to 6 pM. The limit of detection was calculated to be 1.5 ± 0.1 pM. Peak height at 1590 cm–1 was analysed by subtracting background ‘HGN only’ signal from each data point. Error bars represent one standard deviation resulting from 3 replicate samples and 5 scans of each. 1280 nm laser excitation was used for both (a) and (b) and an exposure time of 3 s for (a) and 7 s for (b) were employed in this analysis.
