Data show an increase in the number of food recalls in the U.S. during 2004 to 2013, with recalls due to undeclared allergens nearly doubling in the decade. In the U.K., bacterial contamination has been a major cause of food and beverage recalls since 2012: Salmonella was responsible for 14% of these instances.

A new graphene-based sensor improves food safety by simultaneously detecting multiple substances, including dangerous bacteria and other pathogens. The optical and electronic properties of graphene make it attractive for sensors that use electromagnetic waves known as plasmons that propagate along the surface of a conducting material in response to light exposure. A substance is detected by (a) Schematic of the array of graphene nanostructure. (b) Top view of the unit of the graphene structures. Source: Bing-Gang Xiao, China Jiliang University (a) Schematic of the array of graphene nanostructure. (b) Top view of the unit of the graphene structures. Source: Bing-Gang Xiao, China Jiliang University measuring how the refractive index of the sensor changes when a substance of interest is close to the graphene's surface.

To engineer a graphene sensor that works with the infrared wavelengths necessary to detect bacteria and biomolecules, researchers used theoretical calculations and simulations to design an array of nanoscale graphene disks that each contain an off-center hole. The sensor includes ion-gel and silicon layers that can be used to apply a voltage to tune the graphene's properties for detection of various substances.

Interaction between the disks and their holes results in the plasmon hybridization effect, which increases device sensitivity and creates different wavelength peaks that can each be used to detect the presence of different substances simultaneously. Simulations conducted with mid-infrared wavelengths showed that the new sensor platform is more sensitive to substances present in gases, liquids or solids than using discs without holes.

The tunable system could also improve detection of gases and chemicals for a wide range of other applications.

The research team from China Jiliang University, Zhejiang University of Technology and Technical University of Denmark published their study findings in Optical Materials Express.

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