Digestive Ripening at Nanoscale and Its Application in the Preparation of Monodisperse Nanomaterials

Abstract

Recently, a digestive ripening process at nanoscale has been widely used to prepare monodisperse nanoparticles (NPs), especially for sub-10 nm small NPs, with significant advantages such as the very narrow size distribution of the obtained nanoparticles, the versatile applications for various nanoparticles and the simple operation process. However, no Chinese references are reported on digestive ripening process till now, which may limit the cognition and utility of digestive ripening method for some domestic scientists. Thus, this review starts from the discovery of the phenomenon and the proposal of mechanism for digestive ripening at nanoscale, to the analysis of influence factors including the precursor in the precipitation reaction, the digestive ripening reagent, heating treatment temperature and processing time, solvent media and so on. Then, theoretical hypothesis and the derived results are introduced based on the charged surface, the curvature effect, the interaction between NP surface and attached ligand layer, the diffusion effect and the competing reaction balance in the digestive ripening process. Subsequently, the important applications of digestive ripening method in the preparation of monodisperse nanomaterials of metal NPs, alloy NPs, quantum dots of metal oxide and metal chalcogenide, and other NPs are discussed, the obtained small metal or alloy NPs show a perfect sphere shape and a very narrow size distribution (relative standard deviation less than ±5%). Finally, the broad perspectives are proposed in the NP assembly for optical, electric and magnetic nanodevices, and the heterogeneous catalysis of monodisperse metal, alloy and semiconducotr NPs via the digestive ripening method.

In Situ Kinetic Observations on Crystal Nucleation and Growth

“…In Table , the classical and nonclassical growth mechanisms including monomer attachment, coalescence, Ostwald ripening, oriented attachment, intraparticle growth, digestive ripening, and mixed pathways have been observed in the growth of metal systems. Compared to metal systems, the nonclassical intraparticle growth and digestive ripening mechanisms of metal compounds are still missing in the in situ investigations, although the mechanisms have been widely used for the fabrication of metal oxide or metal chalcogenide nanomaterials . For the crystallization of ice, the classical mechanism and nonclassical coalescence growth mechanisms have been confirmed by the in situ observations, while for the colloids and proteins, classical monomer attachment could be the main growth pathway.…”

Monodisperse Ag, Au Nanoparticles via Solvated Metal Atom Dispersion and Digestive Ripening in Ionic Liquid

“…Digestive ripening (DR), a postsynthetic protocol, transforms a colloid consisting of polydisperse metal nanoparticles into a colloid composed of nearly monodisperse metal nanoparticles. − It is a kinetically controlled thermodynamic process. , In conjunction with the solvated metal atom dispersion (SMAD), digestive ripening has been proven to be an extremely useful synthetic tool for a wide variety of nanomaterials under relatively mild conditions in solution media. − In an earlier work, during digestive ripening, the capping agent, typically an organic ligand with a functional group at one end and a long alkyl tail at the other, facilitates the system toward an equilibrium size of lowest free energy, which is characteristic of a particular metal-capping agent combination under a set of experimental reaction conditions. An equilibrium-sized nanoparticles system is achieved via two steps: (a) digestion of larger nanoparticles which proceeds either through a breakdown process in which nonspherical particles transform into spherical particles or dissolution of small clusters from the surface of nanoparticles and (b) ripening step in which either the dissolved small clusters precipitate as nuclei and transform into equilibrium-sized particles by rapidly growing with one another, or they get redeposited over existing nuclei and ultimately attain the optimum size. − …”