ABSTRACT
Colorants are classified as either pigments or dyes depending on the medium they are involved. Pigments are divided into four broad classes: white, color, inert, and functional pigments. White (hiding) pigments are the ones that contribute light-scattering properties to coatings. As for dyes, they are soluble in the medium they involved during application, losing their crystal or particulate structure in the process contrary to pigments. Basic dyes are cationic dyes which are highly soluble in polar solvents such as alcohols, glycols, and water. A simple microwave-assisted route for producing gold, silver, and Au-Ag structures in the form of stable nano-suspensions as ceramic colorant has been published. Nano-pigments are employed in various disciplines. They are used in cosmetic applications due to absorption of UV characteristic of some nanopigments. Another application is nano-pigment screen employed in cathodic ray tube TVs. As the particle diameters of pigments are reduced, especially below 10 nm, the physical properties of the materials change, causing various complications.
