Fig. 2

Characterization of the synthesized CDNA SERS tags. a-b Representative TEM images of AuNPs (a) and CDNA (b) (scale bars : 100 nm; scale bar in magnified image: 20 nm); c Zeta potentials of AuNPs, AuNPs-La, AuNPs-Labc and CDNA; d UV–vis spectra of AuNPs, AuNPs-La, AuNPs-Labc and CDNA; e SERS spectra of AuNPs + MB, AuNPs-La + MB, AuNPs-Lab + MB and CDNA; f The Raman intensity and color of CDNA after storage at 4 °C for 1, 5, 10, 15, 20 and 30 days