Ultrasensitive and fast single wavelength plasmonic hydrogen sensing with anisotropic nanostructured Pd films

• Published in: Sensors and actuators. B, Chemical Chemical, 2018-11, Vol.273, p.527-535
• Main Authors: Watkins, William L., Borensztein, Yves
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Anisotropy; Beta phase; Carrier density; Carrier gases; Chemical elements; Chemical Sciences; Condensed Matter; Effective medium theory; Evolution; Glass substrates; Hydrogen; Hydrogen sensor; Incident light; Localized surface plasmon resonance; Materials Science; Nanoparticles; Nanostructure; Nanostructured materials; Palladium nanostructure; Physics; Plasmonic sensor; Reflectance; Reflectance anisotropy spectroscopy; Thin films
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2018.06.013

•Ultra-sensitive H2 sensor based on a Pd-based differential plasmonic technique, down to 10 ppm H2 in Ar.•Detection time below a second to half a minute, depending on the H2 concentration.•One spot fabrication of palladium sensors made of an anisotropic nanoporous film.•Single wavelength measurements without use of a monochromator. Anisotropic nanostructured porous Pd films are fabricated using oblique angle deposition in vacuum on a glass substrate. They display a dichroic response, due to localised surface plasmon resonances (LSPR) within the nanoparticles forming the film, dependent on the incident light polarisation. Ultrasensitive hydrogen sensing is reached by using these films in conjunction with a differential optical technique derived from the reflectance anisotropy spectroscopy. The evolution of the samples’ optical responses is monitored during the formation of Pd hydride in both the dilute α-phase and the dense β-phase, whilst the samples are exposed to different concentration of H2 in Ar (from 100% H2 to a few ppm). The measurements are performed at a single wavelength in the visible range and at 22 °C. The results show that a quantitative measurement of the hydrogen concentration in a carrier gas can be measured throughout the concentration range. The limit of detection is 10 ppm and the time for detecting the presence of H2 in the carrying gas is below one second at concentration down to 0.25% of H2 in Ar. Furthermore, the optical anisotropy of the samples and its evolution with exposure to H2 are correctly reproduced with an effective medium theory.