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. Author manuscript; available in PMC: 2012 May 28.
Published in final edited form as: Adv Mater. 2011 Sep 26;23(42):4880–4885. doi: 10.1002/adma.201102636

Figure 3.

Figure 3

Separation of 12 and 24 nm CTAB covered AuNPs in the PVP viscosity gradient. A) Photographs showing 1) structure of the viscosity gradient, 2) two AuNPs fractions, corresponding to 12 nm (top fraction) and 24 nm (bottom fraction) NPs, formed after 40 min centrifuge at 9660 g in the PVP viscosity gradient that has 0.1 M predissolved CTAB, and 3) aggregation of CTAB covered AuNPs in PVP viscosity gradient that has no predissolved CTAB, taken after 10 min centrifuge at 9660 g. B) Photographs showing the colors of the as-prepared pure CTAB covered AuNPs: 1) 12 nm and 2) 24 nm. C) Optical absorption spectra of the as-prepared pure CTAB-AuNPs in Figure 3B and the viscosity gradient separated AuNPs in the fractions in Figure 3A-2. D,E) TEM images of the two AuNPs fractions in Figure 3A-2, showing the size uniformity and free of aggregation after separation in the PVP viscosity gradient.