“When hydrogen gas comes in contact with air, it becomes a bomb.” says Prof. Navakanta Bhat from the Centre for Nano Science and Engineering, and Department of Electrical Communication Engineering at the Indian Institute of Science (IISc). Hydrogen gas sensors have made it possible to detect leaks and maintain high levels of safety. Prof. Bhat and his group of scientists at IISc have succeeded in designing the best hydrogen gas sensor known till date.
The sensor consists of a novel design: embedding a thin metal rod inside a semiconductor shell. An extremely thin rod made of the metal platinum, measuring just 10 nanometres in thickness (1 nanometre is about the thickness of a human hair) is buried inside an equally thin 20 nanometre Platinum oxide shell, which looks like a cylinder. The entire core-shell structure is suspended in air on top of a silicon wafer. Hydrogen gas reacts with oxygen adsorbed (stuck) on top of sensor surface, and results in electrical current -- to generate an alert.
This novel sensor has the potential to render the current ones obsolete. Its sensitivity is around 100 times greater than that of the conventional ones. This means it can sense hydrogen leaks even when the quantity of hydrogen present is one-hundredth the amount required for other sensors to detect a leak.
Present sensors need a heater and function at a temperature of around 150˚C. This sensor can be deployed at room temperature – the power required to run it is almost negligible. Moreover, the present sensors require battery replacements every six months; this new sensor can run on a single battery for a 100 years!
“It doesn’t even need a battery. It can harvest ambient energy like solar energy or even just the wind.” says Prof. Bhat.
The sensor designed by Prof. Bhat’s group is over a thousand times faster than the ones currently used. It can generate an alert within a second while the conventional ones take 15 minutes. The sensors currently in use are placed very close to the site to detect leaks. These super sensitive sensors can even be located a few meters away from the site. This drastically reduces the number of sensors which need to be deployed on each site. The combination of these desirable features could make the new sensor at least 50 times more cost effective.
The research team faced many challenges while designing this novel sensor. A thinner device is more sensitive, but if it becomes too thin, it is prone to breakage. They produced over 300 samples within a few months to zero in on the perfect design. Moreover, the design of this sensor can be extended to sense low levels of other gases, by using different material combinations for metal core and semiconductor shell. A graduate student at Prof. Bhat’s lab is currently working on devices that could detect hydrogen sulphide, a colourless and highly poisonous gas. They expect similar results in terms of the response.
About the authors
Prof Navakanta Bhat is at the Centre for Nano Science and Engineering and Department of Electrical Communication Engineering, Indian Institute of Science, Bangalore. Palash Kr. Basu, Sangeeth Kallatt and Erumpukuthickal Anumol are research scholars with him. The work was carried out at the Centre for Nano Science and Engineering (CeNSE) facility at the Indian Institute of Science, Bangalore.
About the study
It appeared in the Journal of Applied Physics earlier this month.