Ultra-thin graphene sensor to detect air pollution in homes

Scientists, including one of Indian-origin, have developed a graphene-based sensor and switch that can detect air pollution inside our homes with very low power consumption.
The sensor detects individual carbon dioxide (CO2) molecules and volatile organic compound (VOC) gas molecules found in building and interior materials, furniture and even household goods, which adversely affect our living in modern houses with good insulation.
These harmful chemical gases have low concentrations of ppb (parts per billion) levels and are extremely difficult to detect with current environmental sensor technology, which can only detect concentrations of parts per million (ppm).
In recent years, there has been an increase in health problems due to air pollution in personal living spaces, known as sick building syndrome (SBS), along with other conditions such as sick car and sick school syndromes.

Researchers including, Assistant Professor Manoharan Muruganathan of Japan Advanced Institute of Science and Technology (JAIST), developed the sensor to detect individual CO2 molecules adsorbed (the bond of molecules from a gas to a surface) onto the suspended graphene (single atomic sheet of carbon atoms arranged in a honeycomb-like hexagonal crystal lattice structure) one by one by applying an electric field across the structure.
By monitoring the electrical resistance of the graphene beam, the adsorption and desorption (whereby a substance is released from or through a surface) processes of individual CO2 molecules onto the graphene were detected as 'quantised' changes in resistance (step-wise increase or decrease in resistance).

In the study a small volume of CO2 gas (equivalent to a concentration of approximately 30 ppb) was released and the detection time was only a few minutes.

"In contrast to the commercially available environmental monitoring tools, this extreme sensing technology enables us to realise significant miniaturisation, resulting in weight and cost reduction in addition to the remarkable improvement in the detection limit from the ppm levels to the ppb levels," said Professor Hiroshi Mizuta, from the University of Southampton and JAIST, who led the study along with Muruganathan.
The researchers have also recently developed graphene-based switches using a uniquely thin film.

The switches, which require remarkably low voltages (below three volts), can be used to power electronic components on demand, greatly improving the battery lifetime of personal electronic devices.
The researchers now aim to bring the two technologies together to create ultra-low-power environmental sensor systems that can detect single molecules.
The study was published in the journal Science Advances.