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Tunable Graphene Nanostructures for Plasmon-Enhanced Infrared Spectroscopy

Final Report Summary - GRYPHON (Tunable Graphene Nanostructures for Plasmon-Enhanced Infrared Spectroscopy)

Chemical and biological sensors are now ubiquitous in medicine, biology, material science, chemistry and a multitude of other disciplines. In particular, sensors based on infrared spectroscopy have enabled tremendous progress in these fields by providing chemical information in a completely label-free and non-destructive manner. Gryphon project has demonstrated the potential of graphene, the recently discovered two-dimensional material, to implement novel infrared biosensors with new functionalities and superior performance.

The project has fabricated and measured the first infrared graphene biosensor, which is able to detect and sense protein molecules by enhancing their vibrational signals. This has been achieved by combining theoretical and experimental approaches. The different techniques used in the project include electromagnetic simulation, nanofabrication of graphene plasmonic nano-structures, infrared spectroscopic measurements and biological experiments.

The experiments carried out in our graphene biosensor were compared against state-of-the-art metal-based technology and provided the following conclusions. The infrared signals detected by graphene are several times stronger than those in metallic sensors. The reason for this enhancement is the extreme confinement of optical fields due to the unique properties of graphene plasmons. These results show that graphene can enable optical biosensors with higher sensitivity that previous technology. Additionally, the spectral response of the graphene biosensor was dynamically and reversibly tuned, which contrasts with the fixed response of metallic optical sensors. Tunability allowed graphene to scan the infrared spectrum, individually amplify different vibrational bands and extend the spectral range of operation of the sensor. The experiments demonstrate that graphene provides optical biosensors with an new degree of freedom and a higher versatility. Such flexibility will allow a single graphene sensor to detect and analyze a broader range of chemical and biological compounds.

The biosensor was fabricated using graphene grown by chemical vapor deposition, which is the technique of choice for low-cost large-scale production of graphene and the most promising fabrication process for commercial applications. This project has demonstrated that the current level of graphene quality is sufficient to surpass the performance of current technology. Furthermore, as the quality of graphene improves thanks to technological development, graphene infrared biosensors will reach even higher sensitivity and spectral selectivity.

The findings of this project open a new path towards higher performance infrared sensors with novel sensing capabilities. This new technology can find application in those scientific areas and industrial sectors where chemical or biological analysis is needed. Clearly, it is an enabling tool for research in biology, material science or chemistry. In addition to these and as graphene biosensor reaches sufficient maturity, it will impact a broad range of industrial sectors such clinics and diagnostics, food safety, forensics or environmental monitoring.