Simple crystallization approach for enhancing function of plant-based madder dye and performance of dyed fabric.

In the present study, the natural madder dye was investigated to the simultaneous extraction and dyeing of cotton (natural fiber) and nylon (synthetic fiber). The optimum dye extraction conditions were found to be 80 °C, 60 min, and 1:6 with ethyl alcohol after madder had been fermenting for 24 hours with water as solvent. Interestingly, crystallization can be done to separate crystal mollugin from dyed solution. And then, dyed fabrics exhibited improved color strength and ultraviolet protection factor. Meanwhile, the mollugin showed a strong fluorescence emission with maximum emission band at 464 nm with 372 nm excitation in the solid state, which may provide potential molecular system for bio-based optoelectronics and chemical sensors.