Fig. 5

SERS discrimination of single nucleobases in single oligonucleotides. a SERS time series extracted from 1400 spectra produced by adsorbing 5′-CCC CCC CCC A-3′ oligonucleotide submonolayer on the gold nanourchins (9C1A–AuNUs) and trapping them in the nanohole. The two color bars represent the signal-to-baseline intensity of the Raman modes in different time spans, respectively. The white dotted lines and black arrows indicate b the mixed SERS spectra of both A and C, and c the single-A spectra, at specific times. The black dotted lines in (b, c) indicate the frequency positions of the Raman peaks unique to A and C, respectively^31,32.