“Burst Nucleation” vs Autocatalytic, “Burst” Growth in Near-Monodisperse Particle-Formation Reactions

Abstract

In their highly cited 1950 paper (LaMer, V. K.; Dinegar, R. H. Theory, Production and Mechanism of Formation of Monodispersed Hydrosols. J. Am. Chem. Soc. 1950, 72, 4847–4854), LaMer and Dinegar postulated a model of “instantaneous/burst nucleation” and “diffusion-controlled growth” as a way to produce what at the time were believed to be monodisperse particles, narrow particle-size distributions (PSDs) that today are termed near-monodisperse PSDs. Two recent reviews cited in the main text have analyzed the literature citing the LaMer model since 1950 but failed to find any compelling evidence for the LaMer model in the 1953 references citing that classic 1950 paper. However, several questions remain, questions that are addressed in this Perspective: (i) What evidence seemed to compel researchers to argue for “instantaneous/burst” nucleation? (ii) How big were the (S)n sol particles early researchers were observing? What were those early workers actually monitoring? (iii) Is it possible that autocatalytic, “burst” growth is what was more generally if not exclusively being observed? That is, is it possible that a number of workers intuitively citing the 1950 diagram in the past 70 years may have been on the right track at least intuitively, even if not mechanistically, when citing a “burst” feature in their reaction? (iv) Is there an established, minimum particle-formation mechanism that can give step-function-like particle-formation curves exhibiting explosive “burst” growth and, therefore, may have been easily mistaken for “burst” nucleation? (v) In the absence of evidence for burst nucleation, how then can one explain the formation of relatively narrow, near-monodisperse particles from self-assembly syntheses? Overall, the present Perspective strives to summarize the experimental support for “burst nucleation” versus autocatalytic, “burst growth” in particle-formation reactions.