Fig. 4.

The trend of shift in SPR band, $\mathrm{\Delta }\stackrel{\circledR }{{\lambda }_{\mathit{peak}}}$, as a function of operation number, n, where pH ~7 at n = 1, pH ~10 for odd n (red tick marks), and pH ~3 for even n (blue tick marks) for SARS-CoV-2 Omicron spike protein coated gold colloid for d = 10, 15, 20, 30, 40, 50, 60, 80, and 100 nm. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)