Ultraviolet-Visible (UV-visible absorption) absorption spectra were obtained using a Varian Cary 50 bio-UV-visible absorption spectrophotometer. Centrifugation was performed on a Spectrafuge 24D. The transmission electron microscope (TEM) images were captured using JEOL FX 2000 TEM at 200 kV. The histogram of AuNP size distribution was determined from the TEM images using ImageJ® software. Dynamic light scattering (DLS) and Zeta potential experiments were conducted on a Malvern Zetasizer nano.