Emulsion and Gel
Emulsion and Gel:
Emulsions represent colloidal solutions in which both the dispersed phase and the dispersion medium exist in liquid form. However, the key characteristic is that the two liquids are immiscible, as miscible liquids would instead form a true solution. Emulsions can be categorized into two types:
(a) Oil-in-water emulsion: In this type, the dispersed phase is oil, and the dispersion medium is water. An example is milk, where liquid fats are dispersed in water. Vanishing cream is another illustration.
(b) Water-in-oil emulsion: Here, the dispersed phase is water, and the dispersion medium is oil. Examples include butter, cod liver oil, and cold creams.
Since the liquids in emulsions, such as oil and water, tend to separate over time due to their immiscibility, an emulsifying agent or emulsifier is introduced to stabilize the emulsion. Commonly used emulsifiers include soap. The process of preparing an emulsion in the presence of an emulsifier is referred to as emulsification.
What is the mechanism behind the functioning of an emulsifier? The prevailing understanding is that an emulsifier becomes concentrated at the interface where oil and water meet, essentially the surface where these two substances come into contact. In this capacity, it serves as a binding agent, facilitating the cohesion between oil and water.
Applications of Emulsions:
Emulsions play a crucial role in our daily lives, with diverse applications highlighted below:
(1) The efficacy of soap and synthetic detergents in cleansing actions for tasks like washing clothes and bathing relies on the creation of oil-in-water emulsions.
(2) Milk, a quintessential part of our diet, represents an emulsion of fat in water, with milk cream, and butter also classified as emulsions.
(3) Emulsions find extensive use in cosmetic products such as cold creams, vanishing creams, and body lotions.
(4) Certain medicinal substances, like cod liver oil, are administered in emulsion form to facilitate enhanced and faster absorption. Additionally, some ointments adopt an emulsion structure.
(5) The digestive process of fats in the intestine is facilitated by emulsification.
(6) In the extraction of sulfide ores through the froth flotation process, emulsions play a vital role. The finely powdered ore undergoes treatment with an oil emulsion, and through vigorous agitation with compressed air, the ore particles are brought to the surface and subsequently removed.
Gels represent a category of colloids wherein the dispersed phase is a liquid, and the dispersion medium is a solid. Common examples include cheese, jelly, and boot polish. Many widely utilized gels are hydrophilic colloidal solutions that, under specific conditions, transform into elastic semi-solid masses. For instance, a 5% aqueous solution of gelatin forms a jelly block upon cooling. Gels may undergo syneresis, shrinking over time as they release some of the held liquid. There are two main categories of gels: elastic and non-elastic. Elastic gels are reversible, returning to their original form when rehydrated after partial dehydration. Non-elastic gels, on the other hand, are not reversible. Gels, such as silica, cheese, jelly, boot polish, and curd, find diverse applications. Solidified alcohol fuel, a gel of alcohol in calcium acetate is another example.
Moving on to nanomaterials, they have recently gained significant attention due to their potential applications in various fields like medicine, electronics, and industries. Nanomaterials encompass metals, ceramics, polymeric materials, and composite materials. A material with particles ranging in size from 1 nm to 100 nm in at least one direction is classified as a nanomaterial. One nanometer is 10–9m, an extremely small size equivalent to three to five atoms lined up in a row.
Nanomaterials, though produced and used for centuries, have recently seen a surge in interest. The ruby red color of certain types of glass results from nanoparticles of gold, while the lustrous appearance of some medieval pottery is attributed to nanoparticles of metals in the glaze. Nanomaterials can be categorized into fullerenes and inorganic nanomaterials.
(i) Fullerenes are a type of carbon allotrope characterized by hollow carbon spheres composed of a significant number of carbon atoms chemically bonded, such as C60.
(ii) Inorganic nanoparticles, composed of metals, semiconductors, or oxides, exhibit distinctive electrical, mechanical, optical, or chemical properties.
Properties:
Nanomaterials exhibit a wide range of properties, contributing to their vast potential for diverse applications. The following highlights some of the notable features and uses:
(i) Nanomaterials find applications in the production of miniature batteries, superabsorbents, extremely small electronic devices, automotive components, and packaging films.
(ii) The advent of nanocapsules and nanodevices opens up new avenues for drug delivery, gene therapy, and medical diagnostics.
(iii) Nanocomposites are created by blending a small quantity of nanomaterial with polymers. For instance, incorporating as little as 2% by volume of silicate nanoparticles into a polyimide resin can increase its strength by 100%. This addition not only enhances mechanical properties but also improves thermal stability.
(iv) Nanomaterials generally possess high plasticity.
(v) Nanoparticles made of transition element oxides, owing to their large surface area, exhibit catalytic properties.
(vi) Magnetic nanoparticles display superparamagnetism, leading to the discovery of a new category of permanent magnetic materials.
