Figure 3.

(A) Photographs of the pH-triggered reversible phase transfer of 13-nm AuNP-MUA between water and CHCl₃ layers, by switching the pH. The left side vial contains well-dispersed AuNP-MUA in the aqueous phase (top layer) at basic pH, and the right side vial contains AuNP-MUA transferred into the CHCl₃ phase (bottom) layer after adding HCl and vigorous shaking; (B) Plot showing pH-triggered reversible phase transfer of 13 nm AuNP-MUA between the water and organic phase, by monitoring the AuNP-MUA LSPR peak intensity at 525 nm wavelength in aqueous phase; and (C) absorbance of AuNP-MUA in aqueous phase at 525 nm (left scale) versus the pH and percentage transfer of AuNP-MUA from an aqueous to a CHCl₃ layer as a function of pH. The percentage of transfer was calculated by taking the absorbance of the AuNP-MUA (in aqueous medium) at pH 11.0 as 0%. The red color solid curve represents sigmoidal fitting of the experimental data.