Purpurin 18 is primarily used in the field of photodynamic therapy (PDT) due to its strong photosensitizing properties. It is employed as a photosensitizer to target and destroy cancer cells when activated by specific wavelengths of light. This compound is also utilized in research for developing advanced imaging techniques, as it can help visualize cellular structures and processes with high precision. Additionally, Purpurin 18 is studied for its potential in environmental applications, such as the degradation of pollutants under light exposure. Its ability to generate reactive oxygen species makes it valuable in both medical and environmental contexts.