Molecularly imprinted electropolymerization on a metal-coated optical fiber for gas sensing applications

A conductive molecularly imprinted polymer is synthesized around the cylindrical surface of a gold coated optical fiber following an electropolymerization process. The metal film is used as a working electrode during the procedure in order to make the polymer grow on top of it. In addition, the fiber core is previously photo-inscribed with a tilted fiber Bragg grating to benefit from its surrounding refractive index sensitivity. Light coupled to the fiber cladding by the grating planes excites a plasmon wave on the gold surface, enhancing its refractometric properties. The deposition is monitored in real-time by tracking the wavelength shift of the surface plasmon resonance signature, to ensure a good polymer thickness. As a result, light is scattered when the target molecule attaches to the cavities present in the polymer. While the initial device had an operating range limited to liquid solutions, the polymer-coated sensor is able to work into gaseous atmospheres, so the performance of the final sensor is tested by detecting formaldehyde in gaseous state. The molecular imprinting technique provides the selectivity to this certain molecule, while the sensor response exhibits a linear behavior and a limit of detection of a few parts per million. (C) 2017 Elsevier B.V. All rights reserved.