Copper Complex-Coated Nanopatterned Fiber-Tip Guided Mode Resonance Device for Selective Detection of Ethylene

Abstract

Ethylene (C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ) has many commercial usage and in agriculture it plays a key role in climacteric fruit ripening. This paper reports on a copper complex-coated nanostructures patterned on the cleaved facet of an optical fiber to realize a high-performance ethylene gas sensor. The novelty of this paper lies in fiber-optic based sensitive and selective monitoring of gaseous ethylene with excellent performance. A periodic array of polymer nanoposts are formed at the fiber tip and coated with titanium dioxide to serve as a guided mode resonant (GMR) device. A direct method of selectivity is developed for recognizing ethylene, by applying a copper (I) complex coating atop the GMR fiber-tip. The nanopatterned fiber-tip GMR sensor exhibits resonance sensitivity to variations in refractive index at the surface. For repeated use, a simple and cost-effective controllable heater is also integrated at the fiber tip to achieve a complete desorption of the analyte molecules from the sensor surface. This is a first-of-its-kind heater-integrated fiber optic sensor utilizing guided mode resonance and coated with a copper (I) complex coating, that is demonstrated for tracking the ethylene-promoted ripening and senescence of banana. The proposed sensor provides a maximum sensitivity of 60 pm/ppm to ethylene gas with a limit of detection of ~4.7 ppm. Compared to our earlier non-specific fiber-tip gas sensor, we improved the limit of detection for ethylene by 170-fold and sensitivity by 60-fold.