Rapid and sensitive detection of uranyl ion with citrate stabilized silver nanoparticles by surfaced-enhanced Raman scattering technique

Figure S1. The SEM image of AgNPs dispersed on Si. /Figure S2. The UV-vis spectra of silver colloid samples A to D. The 8 mL colloids were condensed 4 times through centrifugation by adding: A) 2 mL of 0.02 wt% trisodium citrate aqueous solution, B) 2 mL of 0.01 wt% trisodium citrate, C) 2 mL of water, and D) 2 mL of water after twice centrifugation, respectively./Figure S3. The Raman spectrum of 0.01 M uranyl citrate on Si. The 970 cm-1 is attributed to the band of Si. /Figure S4. Calibration plot of uranyl concentration with SERS intensity, which shows poor liner relationship between them./Figure S5. The selectivity of the proposed strategy for UO22+ in the presence of competitive metal ions: (A) 5 μM of UO22+; (B) 5 μM of UO22+ containing 100 μM of Na+; (C) 5 μM of UO22+ containing 100 μM of Na+ and Ca2+; (D) 5 μM of UO22+ containing 100 μM of Na+, Ca2+ and Cu2+.