What
Researchers at King’s College London have developed an inexpensive, ultrasensitive, and all-optical hydrogen sensor based on a novel plasmonic metamaterial.
Why
Hydrogen can be used in a wide array of industrial applications: for example, in the petrochemical and chemical industries, but also as fuel in vehicular transportation. It is expected that green hydrogen will be a major player in the next clean energy revolution.
However, with the increased use of hydrogen comes increased danger: fires and protentional detonation can occur at concentrations as low as 4% in air.
Benefits
The all-optical hydrogen sensor developed by researchers at King’s ensures increased safety over current electric sensors. No electrical connections are present in the sensing area, eliminating spark ignition risks.
Furthermore, contrary to common electric sensors, the hydrogen sensor developed at King’s is not poisoned by CO/CO2 and can be reset for multiple use.
The sensor can work at room temperature (no special heating is required).
The sensor can readily detect concentrations as low as 0.1% (well within the noise limits of the sensor), with improved sensitivity available upon further sample optimization.
The response time to 2% hydrogen gas is under 30 seconds with high signal to noise ratio.
The sensor requires minimal micromachining to be built and can be fabricated at low costs, with a scalable fabrication process. Multiple sensors can be built from a single wafer.
Furthermore, the sensor can be fabricated on a flexible substrate and can be mounted on pipes and the like for facilitating leak detection.
Finally, the maximum size required for the sensor can be the same as a laser spot size (approx. 1 mm), without the need of any special optics other than a delivery fibre to be operated.
Opportunity
A working prototype of the hydrogen sensor has been developed (see video at link below).
The technology is protected by a pending European patent application and a pending US patent application and is available for licensing.
King’s is currently seeking suitable commercial partners for further development and commercialisation.
The Science
The hydrogen sensor comprises an array of nanostructure elements, such as nanorods, which can be fabricated using scalable, self-assembled electrochemical processes.
The nanostructure elements are made of a plasmonic material, e.g. gold, and a hydrogen-sensitive materials, e.g. palladium.
In a prototype developed at King’s, gold nanorods are coated with a thin film of palladium.
Thanks to this configuration, the sensor takes advantage of an engineered optical response, based on the interaction between adjacent nanostructures. Specifically, on interrogation by incident radiation in the optical region, the electromagnetic field associated with one nanostructure element spatially overlaps the one of adjacent nanostructure elements, and the sensor acts as a plasmonic optical metamaterial. When the sensor is exposed to hydrogen, not only do the optical properties of each nanostructure change, but also the interaction between them - a combination which leads to superior sensitivity.
Figure 1: (a) Schematic view of a Hydrogen sensor based on a Hydrogen sensitive metamaterial made of Gold nanorods are coated with a thin film of Palladium. (b) CCD images of the reflection from the Hydrogen sensor when exposed to Hydrogen (H2 ON) and Nitrogen (H2 OFF) – the image area is designated by the dashed circle. (c) and (d) Spectra showing the change in transmission reflection respectively, on exposure to Hydrogen.
Demonstrative Video
https://media.kcl.ac.uk/media/Optical+Hydrogen+Sensor+based+on+Metamaterial/1_xsewpomd
Patent Status
EP 2 997 351 A1, pending European patent application; and US 14/890,372, pending US patent application.
Further Information
Nasir, et al., 2014. “Hydrogen Detected by the Naked Eye: Optical Hydrogen Gas Sensors Based on Core/Shell Plasmonic Nanorod Metamaterials”. Advanced Materials 26, 3532–3537. doi:10.1002/adma.201305958