Synthesis and Concentration of Organosols of Silver Nanoparticles Stabilized by AOT: Emulsion Versus Microemulsion

Abstract

In this work, we tried to combine the advantages of microemulsion and emulsion synthesis to obtain stable concentrated organosols of Ag nanoparticles, promising liquid-phase materials. Starting reagents were successively introduced into a micellar solution of sodium bis-(2-ethylhexyl)­sulfosuccinate (AOT) in n-decane in the dynamic reverse emulsion mode. During the contact of the phases, Ag+ passes into micelles and Na+ passes into emulsion microdroplets through the cation exchange AOTNaOrg + AgNO3 Aq = AOTAgOrg + NaNO3 Aq. High concentrations of NaNO3 and hydrazine in the microdroplets favor an osmotic outflow of water from the micelles, which reduces their polar cavities to ∼2 nm. As a result, silver ions are contained in the micelles, and the reducing agent is present mostly in emulsion microdroplets. The reagents interact in the polar cavities of micelles to form ∼7 nm Ag nanoparticles. The produced nanoparticles are positively charged, which permitted their electrophoretic concentration to obtain liquid concentrates (up to 30% Ag) and a solid Ag–AOT composite (up to 75% Ag). Their treatment at 250 °C leads to the formation of conductive films (180 mOhm per square). The developed technique makes it possible to increase the productivity of the process by ∼30 times and opens up new avenues of practical application for the well-studied microemulsion synthesis.

Defect-assisted synthesis of magneto-plasmonic silver-spinel ferrite heterostructures in a flower-like architecture

“…It is also important to observe that all the peaks are symmetric. This behavior could be ascribed to the presence of planar defects that may cause a partial transition from fcc to hcp silver structure [39][40][41] . The theory for stacking faults interpretation was firstly developed by Warren 42 , who described as the intrinsic (α'), extrinsic (α"), and twin faults (β) may affect the line profile, in terms of shift, broadening, and asymmetry ( Fig.…”

Understanding Metallic Nanoparticles Stabilization in Water by Imidazolium Salts: A Complete Physicochemical Study

“…Inorganic media or biphasic systems, such as the polyol method, cyclodextrins, block copolymers and/or reverse micelles are generally used . Synthesis methods are used that develop a sustainable technology, environmentally friendly, which uses biological material such as bacteria, fungi, plants, and their extracts as agents for reducing and stabilizing Ag‐NPs . In this sense, imidazole‐derived compounds, such as imidazolium salts and ionic liquids (ILs), have shown excellent results when used as stabilizing agents in a range of M‐NPs .…”

“…The stabilizers commonly used for the generation of Ag‐NPs in aqueous medium are sodium citrate, ascorbic acid and hexadecyltrimethylammonium bromide (CTAB), among others . Inorganic media or biphasic systems, such as the polyol method, cyclodextrins, block copolymers and/or reverse micelles are generally used . Synthesis methods are used that develop a sustainable technology, environmentally friendly, which uses biological material such as bacteria, fungi, plants, and their extracts as agents for reducing and stabilizing Ag‐NPs .…”

The effect of single CNTs/GNPs and complexes on promoting the interfacial catalytic activity of lipase in conventional emulsions

“…Compared with microemulsions, conventional W/O and oil‐in‐water (O/W) emulsions also offer interfaces between oil and water and usually consist of large droplets of approximately 0.1 to 100 μm in size . The content of the aqueous phase in emulsions can reach to 90 vol%, resulting in a better loading capacity of lipase. Moreover, conventional W/O and O/W emulsions are easy to prepare, with a lower requirement of emulsifier (surfactant) and no need for co‐surfactants.…”