Fig. 4. (A) SERS spectra of citrate-capped AuNPs in the presence of 20 mM of the various halides. (B) The UV-vis spectrum of the AuNSs, their photograph and a TEM micrograph. (C) SERS spectra of the HEPES-capped AuNSs with various concentrations of Br−. The Br− peak is below 200 cm−1 and only its tail showed up. The two highlighted SO3 peaks are from HEPES. (D) Effect of pre-incubation time of AuNP/buffer reflecting the adsorption kinetics of the buffers. The 13 nm AuNPs were incubated with a buffer first for designated times before reacting with NaCl for 1 min and UV-vis measurement.
