The irreversible photochromic pigment is available as white powder at the room temperature. It is generally well soluble in organic solvent but insoluble in water. The irreversible photochromic products show their colours when exposed to UV but not visible light. Thus, the colour appears and intensifies slowly and gradually and the colour intensity increases with the UV exposure time. Unlike the reversible photochromic products, its colour will not revert to their original colours when the UV is dimmed or blocked. The potential application includes to indicate the status of UV sterilisation, and to reveal the dosage of UV-light exposure.
- Donna Chen
