Optical fibre sensors coated with carbon nanotubes,tin dioxide,and nanoporous polymers for cryogenic detection of hydrogen

Abstract

Recently, preliminary measurements carried out by using optical fibre sensors coated with Langmuir–Blodgett (LB) multilayers of closed-end (CeSWCNTs) and opened-end single-walled carbon nanotubes (OeSWCNTs) demonstrated their capability of detecting hydrogen at cryogenic temperatures. In this paper, a comparative study between different sensitive materials for the cryogenic H₂ detection is presented. To achieve this aim, tin dioxide (SnO₂) particle layers and syndiotactic polystyrene (sPS) thin films have also been used as sensitive fibre coatings and their performances have been compared to the ones obtained with the SWCNTs-based overlays. Their integration with optical fibres has been carried out by using the electrostatic spray pyrolysis (ESP) and the dip-coating techniques, which allow thin films at micro and nano scale to be obtained and the sensitive coatings features to be tailored by properly changing the deposition parameters. A time division multiplexing (TDM) approach has been employed in order to simultaneously perform the interrogation of all the fabricated sensors. The results obtained from the experimental measurements demonstrate the capability of the proposed configuration to sense very low concentrations of hydrogen (< 4 per cent) at the very low temperatures of 113 K. CeSWCNTs-based sensors, especially, have demonstrated to be the most interesting materials to be used for the detection of cryogenic hydrogen, with good sensitivity, fast response times, and good recovery features.