This paper describes a general method to drastically improve the dispersity of oleic acid stabilized nanoparticles in aqueous solutions. We use oleic acid stabilized monodisperse nanoparticles of iron oxides and silver as model systems, and have modified the surface properties of these nanoparticles through the formation of an inclusion complex between surface-bound surfactant molecules and α-cyclodextrin (α-CD). After the modification, the nanoparticles of both iron oxide and Ag can transfer from hydrophobic solvents, such as hexane, to α-CD aqueous phase. The efficiency of the phase transfer to the aqueous solutions depends on the initial α-CD concentration. The α-CD/oleic acid complex stabilized nanoparticles can be stable for long periods of time in aqueous phase under ambient atmospheric conditions. Transmission electron microscopy (TEM), ultraviolet−visible (UV−vis) spectroscopy, Fourier transform-infrared (FT-IR) spectroscopy, and colorimetric methods have been used in the characterization of these nanoparticles.

This paper describes the synthesis of silver nanoparticles in a continuous flow tubular microreactor using silver pentafluoropropionate as a single-phase reactant precursor. This precursor can be thermally reduced in isoamyl ether to form silver nanoparticles in the presence of trioctylamine. The reaction is suitable for continuous flow reactors because of the moderate temperature for the formation of silver nanoparticles. The produced silver nanoparticles can have a narrow size distribution. Temperature profiles of the reactant fluids are obtained to understand the formation of silver nanoparticles in the microreactor.

We describe a direct synthetic method for preparing narrowly dispersed silver nanoparticles without using size-selection processes by thermal reduction of silver trifluoroacetate in isoamyl ether in the presence of oleic acid. This direct synthesis is versatile, easy to control synthetically, and able to make Ag nanoparticles with diameters in the range of 7-11 nm with narrow size distribution. The diameter of these nanoparticles can be tuned by varying the oleic acid to silver trifluoroacetate molar ratio. Ostwald ripening can also be used to make Ag nanoparticles with different sizes. The particles were characterized by transmission electron microscopy, selected area electron diffraction, ultraviolet-visible spectroscopy, and powder X-ray diffraction.