Highly Sensitive and Selective VOC Vapor Optical Fiber Sensor Using Hierarchical Nanostructures of Butterfly Wing Scales

Volatile organic compound (VOC) is one of the most widely spread and hazardous environmental pollutants. In this work, a VOC vapor optical fiber sensor is proposed and demonstrated based on the multilayer interference and diffraction of Morpho Didius butterfly wing scales. The sensing wing is fabricated and sheathed on the end of the optical fiber probe with a sleeve, while the sensing element could be easily renewed by replacing the sleeve part. It is found that the reflectance spectrum of the butterfly wings changes with varied VOC vapors. By tracing the spectral changes, the categories and concentrations of VOC vapors are investigated experimentally, while the differential reflectance spectrum ΔR is introduced to magnify the subtle differences of the original spectrum. Here, the dichloromethane, acetone, and ethanol vapors are tested, and the maximum sensitivity of the sensor is measured as 3.303E-5%/ppm, 7.762E-5%/ppm, and 2.881E-4%/ppm, respectively. The principal components analysis method is employed to further analyze the ΔR spectrum, and the concentration of varied VOC vapors could be discriminated and identified according to the distribution of the projected points. Considering its advantages including low-cost, easy fabrication, good repeatability, high sensitivity, and selectivity, this wing-based vapor optical fiber sensor has great application potential in the field of air monitoring.