![]() In literature, different theories are documented illustrating the spontaneous formation of microemulsion such as interfacial, solubilization and thermodynamic theories, etc., out of which few main theories are described below. Ternary phase diagram representing three components of the microemulsion. On the other hand, in O/W microemulsion, the size of droplets can be tailored up to 1–100 nm by varying the concentration of the dispersed phase and the surfactants.įigure 1 shows the ternary phase diagram, the three edges of which represents the components of a microemulsion, namely, oil, water, surfactant (and a co-surfactant, referred as a pseudocomponent is added). The reverse micelles obtained are of spherical shape, monodispersed that can easily control the size of the aqueous core up to 5–10 nm. The W/O microemulsion is generally termed as “reverse micelles” in which water swollen micelles are dispersed into the oil phase, and polar head groups of the surfactant are attracted by the aqueous phase, whereas the hydrocarbon chain is attracted by the oil phase. In general, the surfactants having HLB of 3–6 promote the formation of W/O microemulsions whereas with HLB of 8–18 facilitate the formation of O/W microemulsions. Depending on the hydrophilic-lipophilic balance (HLB) value of the surfactant and the oil/water ratio, the formed microstructure can exist in oil-in-water (O/W), water-in-oil (W/O), hexagonal, reverse hexagonal, or a mixture of (O/W and W/O) called bicontinuous/lamellar phase. The formed interfacial layer leads to different microstructures ranging from oil-swollen direct micelles dispersed in water (O/W microemulsion) over a bicontinuous “sponge” to water-swollen inverse micelles dispersed in oil (W/O microemulsion) phase. On a microscopic level, the emulsifier molecules form an interfacial film, which separates the polar and the nonpolar domains. Microemulsions can be considered akin to micellar solutions that solubilize the oil domain into the nonpolar surfactant tail region to give stable microstructure.īasically, a microemulsion comprises of three components, namely a polar phase (water), a nonpolar phase (oil) and an emulsifier. coined the term called “microemulsion.” A microemulsion is a macroscopically homogeneous system and possesses spherical droplets of the size <50 nm that do not require the higher input of energy and shear reaction conditions, in contrast to conventional emulsions, which are cloudy, kinetically stable and thermodynamically unstable systems. However, it was the year 1959, when Shulman et al. The formation of microemulsion was first described by Hoar and Shulman in 1943, after observing a spontaneous and well-defined transformation of an opaque emulsion to a transparent solution upon addition of medium chain alcohol (co-surfactant). ![]() Microemulsions are thermodynamically stable, optically isotropic and spontaneously formed colloidal dispersed system of two immiscible liquids (such as oil and water), which are stabilized by the interfacial film of a surfactant (and co-surfactant). Based on the high surface area, good crystallinity, controllable particle size, outstanding catalytic, and magnetic properties, the exploitation of nanoparticles as efficient catalysts and drug delivery modules has also been highlighted. The present chapter provides an overview of microemulsions as efficient nanotemplates, with a detailed account of plausible nanomaterials, i.e., metallic nanoparticles, quantum dots, polymeric nanoparticles, mesoporous silica nanoparticles, solid lipid nanoparticles, nanostructured lipid carriers, etc. In microemulsions, the spontaneous formation of domains of nanometric dimensions significantly facilitates their exploitation as potential nanoreactors for the production of stable nanoparticles (due to their cost-effectiveness and ease of preparation). A microemulsion is an optically isotropic and thermodynamically stable colloidal dispersion, which possess spherical droplets (either of W/O or O/W) of the size <50 nm. Template efficacy of microemulsions in generating nanoparticles has garnered considerable attention in the world of colloidal science.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |