Fig. 4

BiASERS analysis of single-molecule SERS of individual nucleobases. a SERS time series of the gold nanourchins with submonolayers of equal moles of cytosine (C) and isotope-edited cytosine (C_iso) molecules adsorbed on their surface (C_isoC–AuNUs) trapped in gold nanoholes. b Representative single-molecule spectra (colored curves) and multi-molecule spectrum (black curve) of C_isoC–AuNU, respectively. c BiASERS distribution of C_iso and C out of about 1030 spectra. d SERS time series of the gold nanourchins with submonolayers of equal moles of adenine (A) and guanine (G) molecules adsorbed on their surface (AG–AuNUs) trapped in a nanohole. e Typical SERS spectra of single-molecule spectra (colored curves) and multi-molecule spectrum (black curve) of AG–AuNU. f BiASERS distribution of A and G out of about 1200 spectra. g SERS time series of the gold nanourchins with submonolayers of equal moles of C and thymine (T) molecules adsorbed on their surface (CT–AuNUs) trapped in a nanohole. h Typical SERS spectra of single-molecule spectra (colored curves) and multi-molecule spectrum (black curve) of CT–AuNU. i BiASERS distribution of C and T from about 1500 collected spectra. All color bars represent the signal-to-baseline intensity of the SERS peaks. The dotted lines indicate SERS peak positions of multilayer nucleobases (black for A or G, red for C or T) adsorbed on silver nanoparticles without bias, respectively, as reported in ref. ³¹.