While ascorbic acid (AA) has been the ubiquitous choice as a mild reductant in the aqueous synthesis of noble metal nanoparticles (NPs), its role beyond the reducing powers has been mostly overlooked. Despite the fact that reduction kinetics of metal salt precursors are most susceptible to modifications by reducing agents, it has frequently been relegated to concentration and pH variations for AA, without delving into the more complex chemistry associated with the latter. The mechanism behind AA-mediated reduction is often stymied by an oversimplified presentation in literature wherein the diprotic acid is assumed to undergo consecutive oxidations via a radical intermediate to form dehydroascorbic acid (DHA). In reality, these assumptions may not accurately describe the aqueous behaviour of AA in a wide array of synthetically relevant conditions.<br/>We show that facile degradation of ascorbic acid has considerable impacts on the formation and properties of aqueous silver NPs and discuss implications for the use of ascorbic acid in NP synthesis. Briefly, experimental evidence shows that the alkaline degradation of AA at no point converges to yield DHA, which follows an independent degradation pathway altogether. While DHA at different stages of degradation consistently results in the formation of spherical/quasi-spherical Ag NPs, it is interesting to note that AA aged for &gt; 12h gives rise to anisotropic plate-like morphology, furthering the hypothesis that a different degradation pathway is followed for both. The role of various plausible degradation products has been additionally studied to inform AA’s assumed behaviour in NP synthesis. These findings have profound implications for the understanding of AA in NP systems, and the mechanisms behind its role as a reductant and surfactant.

Exploring the complex chemistry and degradation of ascorbic acid in aqueous nanoparticle synthesis

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