The defining role of pH in the green synthesis of plasmonic gold nanoparticles using Citrus limon extract

The effect of pH on the growth pathways and final morphology of the plasmonic gold nanoparticles (AuNPs) synthesized using natural Citrus limon extract was in the spotlight. In acidic medium (pH 2.5–5), the growth of AuNPs is fast and involves an intermediate aggregation stage, whereas pH 7–9 results in much slower nucleation-growth route. The synthesis at pH 5 was shown to be the most appropriate for preparation of 8-nm gold nanospheres with narrow size distribution and amazingly bright surface plasmon resonance. The reported findings contribute to better understanding of the processes in “green” AuNP synthesis using C. limon extract and can promote its implementation in sustainable industry. Pronounced plasmonic properties and eco-friendly precursors of the AuNPs make them an essential material for biological tagging and cell visualization.