Ammonia-sensitive photonic structures fabricated in Nafion membranes by laser ablation

Here we report the fabrication and characterization of photonic structures in Nafion membranes sensitive to ammonia in the 0.19%-12.5% concentration range. The photonic structures were recorded by laser ablation of silver nanoparticles synthesized in situ by diffusion. The particles showed an average diameter of 17 nm with a narrow size distribution. After ablation, the nanoparticles generated a diffracting structure giving colorful reflections at defined peak wavelengths. The reflectivity at these wavelengths was directly proportional to concentration after ammonia exposure. The concentration range that can be measured with these membranes encompasses the fatal limit of exposure and the lower flammable limit of gaseous ammonia. Interrogation by reflection spectroscopy makes them suitable for remote sensing and real-time monitoring of gases.