Angle-Sensitive Photonic Crystals for Simultaneous Detection and Photocatalytic Degradation of Hazardous Diazo Compounds

Congo Red (CR) and Amido Black 10B (AB-10B) are anionic diazo dyes, which are metabolized to produce a bioaccumulative and persistent carcinogen, benzidine. In this regard, an angle sensitive sensor composed of photonic crystal supported photocatalyst was fabricated for the simultaneous detection and photocatalytic degradation of diazo dyes from aqueous solutions. Reflectance spectroscopy was used in the detection of CR and AB-10B, which was based on the emergence of the incident angle dependent reflection peaks from the TiO2 coated two-dimensional photonic crystal (2D-PhC) surfaces and their subsequent quenching due to the presence of dye molecules whose absorbance peak intensity overlapped the reflection peak intensity of TiO2 at the respective angle. Interestingly, ultraviolet (UV) mediated photocatalytic degradation of CR and AB-10B was achieved using the same TiO2 coated 2D-PhC surfaces. 2D-PhC underneath the TiO2 layer was able to confine and localize the light on the TiO2 coated 2D-PhC surface, which enhanced the light absorption by dye molecules on the TiO2 surface and the photocatalytic efficiency in the degradation of CR and AB-10B. Finally, this proof-of-concept study demonstrated the fabrication of copolymer film based photonic crystal supported photocatalytic device, which can be used for developing miniaturized sensors competent in on-field detection and degradation of pollutants.