Tuning High Aqueous Phase Uptake in Nonionic Water-in-Oil Microemulsions for the Synthesis of Mn–Zn Ferrite Nanoparticles: Phase Behavior, Characterization, and Nanoparticle Synthesis

Abstract

In this work, the formation of water-in-oil (w/o) microemulsions with high aqueous phase uptake in a nonionic surfactant system is investigated as potential media for the synthesis of Mn-Zn ferrite nanoparticles. A comprehensive study based on the phase behavior of systems containing precursor salts, on one hand, and precipitating agent, on the other hand, was carried out to identify key regions on (a) pseudoternary phase diagrams at constant temperature (50 °C), and (b) pseudobinary phase diagrams at constant surfactant (S):oil(O) weight ratio (S:O) as a function of temperature. The internal structure and dynamics of microemulsions were studied systematically by conductivity and self-diffusion coefficient determinations (FT PGSE (1)H NMR). It was found that nonpercolated w/o microemulsions could be obtained by appropriate tuning of composition variables and temperature, with aqueous phase concentrations as high as 36 wt % for precursor salts and 25 wt % for precipitating agent systems. Three compositions with three different dynamic behaviors (nonpercolated and percolated w/o, as well as bicontinuous microemulsions) were selected for the synthesis of Mn-Zn ferrites, resulting in nanoparticles with different characteristics. Spinel structure and superparamagnetic behavior were obtained. This study sets firm basis for a systematic study of Mn-Zn ferrite nanoparticle synthesis via different scenarios of microemulsion dynamics, which will contribute to a better understanding on the relationship of the characteristics of the obtained materials with the properties of the reaction media.

New Trends on the Synthesis of Inorganic Nanoparticles Using Microemulsions as Confined Reaction Media

“…Recently, Stubenrauch et al (Magno et al, 2009) and Sanchez-Dominguez et al (Aubery et al, 2011) have reported systematic studies on the effects of addition of reactants to nonionic microemulsion systems. It was shown (Magno et al, 2009) that, depending on the aqueous nature of nonionic microemulsion systems, and the salting-in or salting-out effect of the additives, both increase or decrease on the water solubilization could be obtained.…”

“…In the studies by our group on the effects of addition of precursor salts and precipitating agent to the non-ionic microemulsion system aqueous solution / Synperonic® 13/6.5 / isooctane (Aubery et al, 2011), several factors were taken into account: phase behavior (pseudoternary phase diagrams at constant temperature), dynamicity (presence or absence of percolation in W/O structures, or formation of bicontinuous microemulsions), and droplet size (DLS). It was possible to obtain w/o microemulsions at a wide range of overlapping compositions for both precursor salts and precipitating agent.…”

“…In the work carried out by our group concerning a nonionic system (Aubery et al, 2011), large microemulsion regions were obtained when the reactants were incorporated, as mentioned in Section 2.3. Thanks to this high aqueous phase uptake and the overlap of microemulsion regions for both precursor salts and precipitating agent, synthesis of Mn-Zn ferrite nanoparticles could be carried out using a wide range of compositions.…”

Synthesis and characterization of manganese–zinc ferrite obtained by thermal decomposition from organic precursors

“…These characteristics have enabled the use of nanosized magnetic materials in biomedicine (e.g., as bioseparators), drug delivery systems, medical diagnostics, and cancer thermotherapy [5][6][7]. Due to the new applications of ferrites ways of synthesizing them, other than the ceramic method, such as the sol-gel [8,9], the precipitation [10,11], the mechanochemical [12,13], the hydrothermal [14,15], the combustion [16][17][18][19][20], and the microemulsion methods [21,22], are being widely investigated. The unquestionable advantages of the above methods are: the mixing together of the reagents at the molecular level, energy efficiency, the fact that only one process stage is required, and the absence of secondary pollution or material loss.…”

Synthesis of Nanostructured Catalytic Materials from Microemulsions

“…These very different processes are associated to a great range of catalytic materials. The microemulsion method, based on water-in-oil, oil-in-water and bicontinuous ME, has shown to be suitable for the preparation of all these different types of materials [12][13][14][15][16][17][18][19][20][21][22].Even though a few valuable efforts were previously done to understand the formation of nanomaterials in ME systems [23][24][25], comprehensive research in this area is still needed to clarify this process, in order to reach a better control of nanoparticle characteristics and to understand why the formed nanoparticles present specific catalytic properties compared to the materials with the same composition but prepared by traditional methods. Especially advanced analytical tools for deep…”