Colorimetric Sensor Identifies Airborne Threats

To recent developments in photonic structures, some structural colors can be reversibly changed in response to external stimuli. Based on a lesson from natural photonic structure, specific examples of photonic crystal‐based structural coloring schemes show unprecedented possibilities in colorimetric sensor applications, such as temperature, pH, ion species, solvents, water vapor, humidity, pressure, and biomolecule detection.

Since a combination of introduced design methods for colorimetric detection, inspired by photonic structures, depends on highly ordered structures and periodically arranged refractive indices, concomitant co‐assembling of multiple materials and micro/nano building blocks to achieve uniform colors at a large scale constrains their rapid/convenient fabrication.

Researchers present a productive approach to colorimetric sensor design to fuse the advantages of strong resonant photonic structures and dynamically responsive materials. As a reliable dynamic reactant, they employed M‐13 bacteriophages with the capability to generate identical copies of themselves through bacterial host cell infection. Using a highly lossy resonant promoter (HLRP) as the substrate, the spin‐coated M‐13 virus layer exhibits strong resonance even with ultrathin thickness variations, resulting in colorimetric behavior with enhanced chromaticity.

In the design process, researchers optimize the resonance characteristics according to the substrate’s complex refractive index to maximize the coating layer’s resonance. Furthermore, rigorous coupled-wave analysis (RCWA) is performed, considering various material combinations to demonstrate a colorimetric palette of wide chromatic selectivity with a dynamic variation.

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