Digestive ripening: a synthetic method par excellence for core–shell, alloy, and composite nanostructured materials

Abstract

The solvated metal atom dispersion (SMAD) method has been used for the synthesis of colloids of metal nanoparticles. It is a top-down approach involving condensation of metal atoms in low temperature solvent matrices in a SMAD reactor maintained at 77 K. Warming of the matrix results in a slurry of metal atoms that interact with one another to form particles that grow in size. The organic solvent solvates the particles and acts as a weak capping agent to halt/slow down the growth process to a certain extent. This as-prepared colloid consists of metal nanoparticles that are quite polydisperse. In a process termed as digestive ripening, addition of a capping agent to the as-prepared colloid which is polydisperse renders it highly monodisperse either under ambient or thermal conditions. In this, as yet not well-understood process, smaller particles grow and the larger ones diminish in size until the system attains uniformity in size and a dynamic equilibrium is established. Using the SMAD method in combination with digestive ripening process, highly monodisperse metal, core-shell, alloy, and composite nanoparticles have been synthesized. This article is a review of our contributions together with some literature reports on this methodology to realize various nanostructured materials.

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

“…The decrease in the full width at half-maximum (fwhm) (Figure S2) of the UV−vis spectral band further supports that focusing of a particular size within a narrow size distribution was attained (see Figure 2a−j) as evidenced by the TEM micrographs of aliquots drawn at different time intervals. We demonstrated previously 24 that the mechanism of digestive ripening involves surface etching of large particles yielding seeds termed as "dot particles"; herein, we noted the dot particles in the TEM micrograph (Figure S3) of the sample drawn at 10 and 60 min intervals. Further stirring of the reaction mixture resulted in the growth (Figure 2i) of these particles into larger particles with a broader size distribution (Figure 2j), which could be attributed to the Ostwald ripening process.…”

Monodisperse Colloidal Metal Nanoparticles to Core–Shell Structures and Alloy Nanosystems via Digestive Ripening in Conjunction with Solvated Metal Atom Dispersion: A Mechanistic Study

“…To realize controlled synthesis of these materials, it is essential to manipulate the kinetics of growth of shell on the core particles. In this context, digestive ripening process offers possibility to optimize several reaction parameters to obtain defined heterostructures. , The process of digestive ripening involves interexchange of atoms between different particles through surface etching assisted by surface active ligands . Several bimetallic nanostructures, like Ag@Pd, Au@Pd, Cu@ZnO, Mg–Cu, Cu–Zn, etc., have been reported by our group using the digestive ripening approach. − However, the factors that affect the core–shell structure formation by this versatile method remain undetermined.…”

“…In this context, digestive ripening process offers possibility to optimize several reaction parameters to obtain defined heterostructures. 25,26 The process of digestive ripening involves interexchange of atoms between different particles through surface etching assisted by surface active ligands. 27 Several bimetallic nanostructures, like Ag@Pd, Au@Pd, Cu@ ZnO, Mg−Cu, Cu−Zn, etc., have been reported by our group using the digestive ripening approach.…”

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

“…Jagirdar 等 [119,120] 利用消化熟化法合成了 Cu 和 Zn 等金属单分散纳米粒子, 然后经过共消化熟化得到了 Cu@ZnO 的核壳结构; Yang 等 [121] 把溶剂热法合成的多 分散 FeS 2 纳米晶(7.4±1.4 nm)经过消化熟化后获得了 FeS 2 纳米晶单分散体系(5.5±0.3 nm); Viswanatha 等 [33] 研究发现, 在油酸和油胺存在下, 经 200 ℃热处理得到 大尺寸的 FeCoS 2 纳米片, 然后再升温到 300 ℃, 可以 转变为 9 nm 的高度单分散的球状纳米晶.…”