The Latest Ultra-sensitive Gas Sensors

By using Graphene doped with Boron, scientists have developed ultra-sensitive gas sensors that could one day be able to detect the presence of one molecule of gas in a thousand trillion molecules of air.

Various gases, such as those produced by explosives, are specifically difficult to detect – you need extra-sensitive sensors. However, scientists are considering Graphene as being the new material for creating a stream of electronic devices, including sensitive gas detectors. Graphene has high conductivity and is useful as a gas detector as a one-atom thick, two-dimensional material.

In the Pennsylvania State University, a team of international researchers has created an amalgam from Graphene and Boron. This amalgam has the property to detect particular gases down to the level of mere parts per billion. The team is confident of ultimately making detectors sensitive enough to detect exceedingly tiny amounts of gas in the order of parts per quadrillion.

Scientists have paired Boron atoms with Graphene and created a heteroatom structure. Here, non-carbon atoms bond with carbon atoms to form part of a molecular ring. The structure acts as a sensitive sensor to detect exceptionally low concentrations of gas molecules. It can detect parts per million of Ammonia and parts per billion of Nitrogen Oxide. According to the scientists, this is equal to an ammonia detection rate of 105 times and Nitrogen Oxide sensitivity of 27 times more than what the untreated Graphene can detect.

Mauricio Terrones, a professor of physics, chemistry and materials science at the Pennsylvania State University, says they have been pursuing the project for the past four years. Although they had doped Graphene with atoms of Nitrogen earlier, doping with Boron proved much more challenging. However, once they sorted out that difficulty, they were able to synthesize the boron graphene, collaborations with experts in the US and other countries in the world confirmed their research and the properties of the material.

Graphene is essentially Carbon, while Boron is an element sitting right next to Carbon on the periodic table. That means they have similar atomic structures and therefore, should combine relatively well. However, compounds of Boron are not stable with exposed to air – they break down rapidly – making it difficult to combine the two elements when using normal Graphene production methods.

Researchers overcame this by using a special technique called chemical vapor deposition assisted with a bubbler. This method isolates the atmospheric boron when incorporating the element with the Graphene. The process produces sheets of Boron-doped Graphene of size equal to one-square centimeter.

They then transferred the sheets to the Honda Research Institute USA in Columbia, OH. Here, they compared the performance of the sheets with the performance of known highly sensitive gas sensors. Scientists at the Novoselov lab at the University of Manchester, UK examined the electron transport function of the sensors. Simultaneously, contributing researchers in Belgium and the US established the meld of Boron atoms within the Graphite lattice and studied the influence of their interaction and influence with Nitrogen Oxide or Ammonia.

According to Dr. Avetik Harutyunyan, the Chief Scientist and project leader at the Honda Research Institute USA Inc., this multidisciplinary research offers new avenues for further exploring ultrasensitive gas sensors.