doi:10.1038/nindia.2015.89 Published online 7 July 2015
Scientists in Bangalore have designed an ultra-sensitive, energy-efficient sensor that can detect hydrogen leaks1. The sensor, which works at room temperature unlike current sensors that function at 150 degrees Celsius, could have applications in the process industry and the space sector, where the gas is widely used.
The sensor consumes about 1000 times less power, and is 100 times more sensitive than its market cousins, its developers at the Indian Institute of Science (IISc) say. It generates an instant alert and works on a battery that can last almost a life time unlike conventional ones that take 15 minutes to generate an alarm and need battery replacements every six months.
Based on a nanostructured combo of platinum and its oxide, the sensor has a hair-thin platinum rod (1 nanometre, one-billionth of a metre) embedded inside a 20-nm platinum oxide semiconductor shell. This shell with the platinum rod inside lies suspended atop a silicon wafer on which oxygen is adsorbed.
Platinum oxide offers two attractions – it is a metal catalyst for redox reactions (in which one substance gets reduced and the second oxidised); and it is a p-type semiconductor. The design exploits the in-built electric field differences between the metal and the metal oxide junction to modulate conductivity.
Navankanta Bhat, from IISc’s Centre for Nano Science and Engineering, whose team designed the sensor along with IISc’s Department of Electrical Communication Engineering, says any leaked hydrogen gas reacts with the oxygen on sensor surface, generating an electrical current and an alert.
Similar metal-metal oxide combo sensors available in the market also work on the principle of surface conductivity modulation caused by redox reactions. But the reaction needs to be typically activated at high temperature, which requires a microheater to be integrated with the sensor, whose power consumption can be to the tune of 100 milliwatts.
By doing away with the heater, the new sensor saves power by about 1000 times, Bhat told Nature India.
The low power requirement also means that the sensor's battery lasts longer and be powered by solar energy. Bhat says the sensor may even replace the battery with solar energy. The scientists are now testing if the design concept can be extended to detect leaks of other gases such as hydrogen sulphide.
1. Basu, P. K. et al. Suspended core-shell Pt-PtOx nanostructure for ultrasensitive hydrogen gas sensor. J. Appl. Phys. 117, 224501 (2015) doi: 10.1063/1.4922240