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. 2013 Jun 6;3(3):20120098. doi: 10.1098/rsfs.2012.0098

Figure 2.

Figure 2.

Characterization of the plasmonic optical properties and stability (non-aggregation) of single Au NPs suspended in egg water (20 pM) at 28.5°C over 120 h. (A,B) Dark-field optical images of the Au NPs that had been suspended in egg water for: (A) 0 and (B) 120 h, showing single plasmonic green, orange and red NPs. (C) Histograms of colour distributions of the single Au NPs in (A,B) measured by DFOMS show: (a) (70 ± 4)% of plasmonic green, (23 ± 5)% of orange and (7 ± 2)% of red NPs; and (b) (72 ± 5)% of plasmonic green, (22 ± 6)% of orange and (5 ± 1)% of red NPs. (D) The number of single Au NPs imaged by DFOMS (similar to those zoom-in images in A,B) is 264 ± 10, 261 ± 9, 250 ± 6, 249 ± 8, 257 ± 13, and 261 ± 7 NPs per image at 0, 24, 48, 72, 96, and 120 h, respectively, indicating that the number of NPs remains unchanged over time, and that the NPs are stable in egg water over 120 h. (E) Representative LSPR spectra of single plasmonic green, orange and red Au NPs show λmax (FWHM) at: (a) 554 (105); (b) 619 (97); (c) 683 (82) nm. The scale bars in (A,B) are 2 μm, which show the distances between individual NPs, but not their sizes because of the optical diffraction limit.