Structure and Properties of Dyes and Pigments

Abstract

Colour is one of the elements of nature that makes human life more aesthetic and fascinating in the world. Plants, animals, and minerals have been used as primary sources for colourants, dyes or pigments since ancient times. In our daily life, we know about many substances which have specific colours. These are the substances which are used as colourants i.e.; colour imparting species. Both dyes and pigments are coloured as they absorb only some wavelength of visible light. Their structures have Aryl rings that have delocalized electron systems. These structures are said to be responsible for the absorption of electromagnetic radiation that has varying wavelengths, based upon the energy of the electron clouds. Dyes are coloured organic compounds that are used to impart colour to various substrates, including paper, leather, fur, hair, drugs, cosmetics, waxes, greases, plastics and textile materials. A Dye is a coloured compound due to the presence of chromophore and its fixed property to the acid or basic groups such as OH, SO3H, NH2, NR2, etc. The polar auxochrome makes the dye water-soluble and binds the dye to the fabric by interaction with the oppositely charged groups of the fabric structure. Pigments are organic and inorganic compounds which are practically insoluble in medium in which they are incorporated. Dyes and pigments are the most important colourants used to add colour or to change the colour of something. They are widely used in the textile, pharmaceutical, food, cosmetics, plastics, paint, ink, photographic and paper industries. This chapter is devoted to the structure and properties of dyes and pigments.

Playing with Isostructurality from Binary Cocrystals to Ternary Cocrystal Solvates of Quercetin: Tuning Colors of Pigment

“…10−12 To our knowledge, organic pigments are very important to society and are widely used in the production of fabrics, cosmetics, food products, photovoltaic materials, and plastic coloring. 13 With the current rapid-increasing demand for pigments tailored for specific applications, the ability to design new organic pigment materials with desirable optical properties is needed. The optical properties of organic pigments depend not only on the molecular structures but also on the corresponding crystal packing patterns.…”

“…Cocrystals can offer an alternative but efficient approach for improving physicochemical characteristics of a target compound, such as solubility, bioavailability, stability, density, elasticity, plasticity, and melting point. , Meanwhile, cocrystals are also known as the paradise of material research for exploring novel phenomena and functionalities containing white light emission, room-temperature phosphorescence, ferroelectricity, etc. Therefore, molecular cocrystals have attracted considerable interest and found their potential application in various fields (e.g., pharmaceutical, chemical, electronic, military industries). , In contrast, few studies on the field of pigment cocrystals have been reported in the literature so far. − To our knowledge, organic pigments are very important to society and are widely used in the production of fabrics, cosmetics, food products, photovoltaic materials, and plastic coloring . With the current rapid-increasing demand for pigments tailored for specific applications, the ability to design new organic pigment materials with desirable optical properties is needed.…”

Study of Isotherm and Kinetics for Remediation of Congo Red Using Nanocomposite Bead

“…Dyes are the chemical substances that impart colour to textiles, leather, paper, or any other materials and this colouring is not generally altered by washing or when exposed to sunlight, heat, or any other factors. 1 Until the 1850s, dyes were originally derived from natural sources such as plants, trees, fungi, vegetables, insects, etc. Moreover, barks, leaves, or roots of selected trees or plants were widely used as a source of natural dyes.…”

“…Moreover, barks, leaves, or roots of selected trees or plants were widely used as a source of natural dyes. 1 A great problem for older fabric dyes was their poor colour fastness. These dyes are washed out easily from fabric.…”

“…These dyes are washed out easily from fabric. 1 So, the development of proper mordant was a great challenge to researchers. After the discovery of mauve, the first synthetic dye, researchers have paid more attention to synthesize more and more synthetic dyes due to their use in industries.…”