An ammonia sensor based on Lossy Mode Resonances on a tapered optical fibre coated with porphyrin-incorporated titanium dioxide

• Published in: Sensors and actuators. B, Chemical Vol. 242; pp. 645 - 652
• Main Authors: Tiwari, Divya, Mullaney, Kevin, Korposh, Serhiy, James, Stephen W., Lee, Seung-Woo, Tatam, Ralph P.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01-04-2017; Elsevier Science Ltd
• Subjects: Ammonia; Ammonia sensing; Biosensors; Coating; Core loss; Fibers; Lossy Mode Resonances; Optical fibres; Optical properties; Refractivity; Response time; Titanium; Titanium dioxide; Titanium oxide powders; Ammonia sensing; Lossy Mode Resonances; Optical fibres
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2016.11.092

•Generation of Lossy Mode Resonances (LMRs) by the deposition of a nanoscale coating of titanium dioxide, incorporating a porphyrin as a functional compound, onto tapered optical fibres.•Study of the evolution of the LMRs with increasing coating thickness on adiabatic and nonadiabatic optical fibre tapers.•Demonstration of a sensor based upon the interaction of the porphyrin incorporated into the coating with ammonia.•Limit of detection of 0.1ppm.
The development of a highly sensitive ammonia sensor is described. The sensor is formed by deposition of a nanoscale coating of titanium dioxide, containing a porphyrin as a functional material, onto a tapered optical fibre. The titanium dioxide coating allows coupling of light from the fundamental core mode to a lossy mode supported by the coating, thus creating a Lossy Mode Resonance (LMR) in the transmission spectrum. A change in the refractive index of the coating caused by the interaction of the porphyrin with ammonia causes a change in the centre wavelength of the LMR, allowing concentrations of ammonia in water as low as 0.1ppm to be detected, with a response time of less than 30s.