Abstract: Azo dyes represent a significant class of synthetic organic dyes produced and used on a large scale in the textile industry due to their wide range of colors, ease of synthesis, and versatility. These dyes are characterized by the presence of one or more azo (-N=N-) groups. This azo bond connects aromatic rings and is responsible for the vivid coloration of azo dyes. The vibrant colors and high stability of these dyes have made them highly popular in the textile industry and in diverse fields such as the food industry, materials science, analytical chemistry, and biomedicine, where they are used as colorants, sensors, indicators, and functional materials, as discussed further. In this paper, we discuss both traditional and eco-friendly routes for the synthesis of azo dyes. Traditional synthesis mainly involves diazotization and coupling reactions, whereas eco-friendly approaches include the use of polyethylene glycol (PEG), nanoparticles, and other miscellaneous techniques such as ultrasound and photocatalytic methods, allowing a wide range of structural modifications. Additionally, various synthetic routes for azo dyes are reviewed. For structural confirmation, different analytical techniques such as UV-Vis spectroscopy, FTIR, NMR, and mass spectroscopy are employed.
Upadhyaya et al. (2026) studied this question.