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

Abstract

Co-digestive ripening of two distinct metal nanoparticles is an exceptional method for the colloidal synthesis of core−shell heterostructures. In this report, a detailed investigation of the underlying mechanism by which surfactant molecule assisted interatomic transfer between two metal nanoparticles occurs has been described using gold/ silver as a model system. Core−shell nanoparticles with gold in the core and silver in the shell in the size regime of 6.9 ± 1.8 nm were obtained by conducting the codigestive ripening of polydispersed particles of Au− pentanone and Ag−pentanone colloids in the presence of hexadecylamine as a capping agent used in the molar ratio of 1:30 with respect to metal. The progress of the formation of core−shell nanoparticles has been monitored using UV−visible spectroscopy and transmission electron microscopy. Detailed analysis of the nature of Au@Ag core−shell nanoparticles has been done with the help of HAADF-STEM technique, point-EDS analysis, elemental line scanning technique, and X-ray photoelectron spectroscopy. Variation of experimental conditions such as concentration of capping agent, molar ratio of Au and Ag, and temperature in the codigestive ripening process led to the realization that core−shell nanoparticles with thicker shell of silver can be obtained under certain reaction conditions. Alteration of the reaction conditions was also noted to affect the final Au@Ag nanoparticles with respect to average particle size and polydispersity. The as-prepared Au@Ag nanoparticles could be transformed to Au−Ag nanoalloys on being exposed to ultraviolet radiation of 254 nm. We have also attempted to elucidate the factors which dictate the formation of core−shell nanoparticles by comparing with the findings of theoretical studies from the literature with our experimental results.

XPS study of silver and copper nanoparticles demonstrated selective anticancer, proapoptotic, and antibacterial properties

“…Therefore, the use of environmentally acceptable “green” technologies for the production of biologically active metal nanoparticles will significantly reduce or eliminate the negative impact on the environment, caused by classical synthetic methods. An effective approach for the preparation of Ag NPs and Cu NPs is MVS, which is applied for production of mono‐ and bimetallic biologically active nanoparticles and allows avoiding or significantly reducing contamination introduced into biomedical materials under the conditions of chemical synthesis 15–19 . The MVS is considered as environmentally safe, green chemistry technique because it does not utilize hazardous reagents like stabilizing or reducing agents that are toxic to living organisms and/or pollute the environment.…”

Bimetallic Gold-Silver Nanoparticles Supported on Zeolitic Imidazolate Framework-8 as Highly Active Heterogenous Catalysts for Selective Oxidation of Benzyl Alcohol into Benzaldehyde

“…However, the selectivity of ester was only 10.8% over the catalyst of Au–Pd/Fe–Gr. Due to the high price and limited resources of Au metal, a variety of catalyst preparation strategies have been developed to maximize Au utilization [11,12]. For example, core-shell structured catalysts with Au shells are considered to be promising alternatives to improve Au metal dispersion.…”

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

“…Jagirdar 等 [108] 将合成的多分散金和银纳米粒子进行 共消化熟化, 通过改变配体浓度、两种金属的物质的量 比和热处理温度等实验条件, 制备了外壳厚度可调的 Au@Ag 纳米核壳结构, 并发现这种核壳结构经过紫外 线照射后形成均质纳米合金. Parkin 等 [109] 报道了一步法 制备 Au@Ag 和 Ag@Au 核壳型合金纳米粒子, 且内核 和外壳均可以使用不同成分的 Au-Ag 合金代替.…”