Porous Anodic Aluminum Oxide Bragg Stacks as Chemical Sensors

Porous anodic aluminum oxide (AAO) Bragg stacks were fabricated by a modified two-step anodization, and the optical transmittance spectra of AAO Bragg stacks soaking in varied analytes (air, series of alcohols and alkanes) were collected. The results show that both the wavelength and the intensity of the reflected light are sensitive to the analyte's refractive index and infiltration; e.g., for any two adjacent analytes in a series of alcohols or alkanes, the difference of transmittance in dip is greater than 3%. This phenomenon enables us to fabricate chemical and biological sensors and in situ monitor the organic chemical reaction just by analyzing the intensity of the reflected light without a spectrophotometer.