Hydrodynamic Diameter of Silver Nanoparticles in Solutions of Nonionic Surfactants
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ICAL CHEMISTRY OF SURFACE PHENOMENA
Hydrodynamic Diameter of Silver Nanoparticles in Solutions of Nonionic Surfactants P. S. Popovetskiya,* and A. N. Kolodina a Nikolaev
Institute of Inorganic Chemistry, Russian Academy of Sciences, Siberian Branch, Novosibirsk, 630090 Russia *e-mail: [email protected] Received December 12, 2019; revised March 13, 2020; accepted March 17, 2020
Abstract—Physicochemical characteristics of silver nanoparticles with known sizes are studied, depending on the concentration of nonionic surfactants and the concentration of the metal. Surfactants are used that form micelles of different sizes and different intensities of light scattering. It is shown that the surface tension and adhesion properties of solutions of nonionic surfactants are determined by the solvent in ranges of concentration lower than 1 mol/L. An approach based on spectrophotometry and viscosimetry is proposed that allows determination of the most likely reasons for discrepancies in the hydrodynamic diameter of nanoparticles in solutions of nonionic surfactants and the actual diameter of the nanoparticles. Keywords: nanoparticles, adsorption layer, reverse micelles, dynamic light scattering, surface tension, adhesive properties, microviscosity DOI: 10.1134/S0036024420100246
INTRODUCTION Nanoparticles are one of the most popular objects of today’s scientific research. The areas of their possible application are extremely wide, extending from electronics [1, 2] to medicine [3, 4]. For practical purposes, a high level of an object’s monodispersion rather than the size of the nanoobjects themselves is often more important, since predictable and reproducible properties can be achieved only with a narrow size distribution of particles [5, 6]. When the aim is to obtain nanoparticles with a high level of monodispersity, wet chemistry comes to the fore, i.e., the synthesis of nanoparticles in a liquid medium (organic or otherwise) using stabilizers, particularly molecules of surfactants [7]. This is known as the bottom-up technique (i.e., from atoms or molecules to nanoparticles). In such an approach, surfactant micelles used as nanoreactors display close aggregation numbers and almost the same size, due to which nanoparticles based on them are also similar in size [8, 9]. One of the most important parameters of nanoparticles in liquid media that affect (among other things) their stability, is the value of hydrodynamic diameter, which determined by both the size of the nanoparticle itself (usually found by microscopic techniques), and the thickness of its adsorption layer (which can be found by comparing data from electron microscopy and dynamic light scattering) [10, 11]. The thickness of the adsorption layer directly determines the resistance of nanoparticles with respect to agglomeration; the thicker the adsorption layer of nanoparticles, the
more difficult it is for the nanoparticles to reach a distance great enough to form stable aggregates. However, correctly determining the hydrodynamic diameter of nanoparticles agai
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