ZnS Photonic Nanocrystals Dip-Coated on PDA-Coated Aluminum Sheets for Color-Based Temperature Sensing

Temperature detection is crucial for public safety as well as knowledgeable security monitoring and fire sensing systems. Thus, enabling visual warnings for various temperatures is highly significant. Herein, secondary color-changing photonic crystal (PC) coatings were fabricated on the metal substrates based on polydopamine degradation and the crystal structure transformation of ZnS nanoparticles when heated across different temperature ranges. The PC coatings exhibit their first color change within 97 s at 300 °C and a second color change after 700 °C (276 s). This color change enables both automated warning responses via computer algorithms and visual detection by the naked eye, achieving effective visual sensing. The PC coatings can be directly applied to the monitoring surfaces for temperature sensing. When integrated with existing surveillance cameras, no additional equipment is required.