Extended Data Fig. 6: dCERS of different analytes and using different colloids.
From: Digital colloid-enhanced Raman spectroscopy by single-molecule counting
The relationship between RPV and analyte concentrations of (a) crystal violet (CV), (b) 4-NBT, (c) cysteine, (d) A12, (e) hemoglobin, (f) D-glucose, (g) Nile blue (NB), (h) paraquat and (i) thiram measured using Hya-Ag colloids plotted in a linear-linear scale. The calibration curves of (j) cysteine, (k) NB, (l) paraquat and (m) thiram measured using Hya-Ag colloids. The cysteine shows a much lower efficiency than 4-NBT likely owing to a smaller molecular cross section assuming that both have a high affinity to Hya-Ag colloids via covalent binding. (n) The calibration curves of CV using Hya-Ag colloids (blue), citrate-Ag colloids (red) and citrate-Au colloids (black). Though the three different types of colloids have comparable surface potential and concentration, citrate-Au colloids exhibit a much lower efficiency than the other two Ag colloids due to a poorer plasmonic effect. Additionally, the efficiency of citrate-Ag colloids is slightly lower than Hya-Ag colloids probably because of a layer of citrate residues which may cause steric hindrance to impede CV from getting close to the metallic surface to some extent even though the size of citrate-Ag colloids is larger than Hya-Ag colloids. For the calibration curves, the error bars indicate the standard deviations calculated with 3 independent measurements. Fitting formula: \(\log RPV=k\log M+b\).