Fig. 4.

(A) Photographic images of AuNP conjugates of varying sizes subjected to NaCl stability test. Stable conjugates remain pink, while the AuNP labels with insufficient surface coverage agglomerates and turns violet or colorless. (B) Schematic representation showing the possible orientation of IgG on the AuNP surface. (C) Absorbance spectra of AuNP labels for varying sizes obtained using USB 4000 spectrometer. A broader full-width half maxima of the citrate-capped AuNPs indicates a 30-40% wider size distribution in comparison to 40 nm AuNP.