Fig. 3.

(a) Normalized average absorbance spectrum for gold spikes fabricated with 480s ED time. The plot is the average of 25 spectra collected on different substrate positions on different samples. (b) Absorption spectra resulting from the exposure of gold nanospikes to aqueous solutions with different refractive indexes: water (W) and water/glycerol (G) mixtures with varying concentrations 10 to 50% w/w. The black arrow highlights the red shift in the resonance peak due to the increase in the refractive index of the solution. (c) The refractive index sensitivity of the gold nanospike substrate is calculated by linear regression from LSPR peak shifts recorded for water and glycerol mixtures shown in (b).