Polymethine dyes are a class of organic compounds that contain a chain of carbon atoms with alternating double bonds. These dyes are characterized by their intense color, high light absorption, and fluorescence properties. They are commonly used in a variety of applications, such as in the textile industry, medical imaging, and as markers in biological research. Polymethine dyes are also being investigated for their potential use in photothermal therapy for cancer treatment and as contrast agents in imaging techniques. Their unique chemical structure and properties make them versatile and valuable compounds in the field of materials science and biochemistry.