Ultrasensing in the nearfield: polariton enhanced molecular fingerprinting

• Applicant: Dr. Bernd Kästner
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 529998081

In analytical methods there is a strong demand for improvement for higher sensitivity, selectivity, and cheaper methods to serve society better. Such developments need to start with a better understanding of basic processes, fundamental technical changes, or exploiting new materials. The UltraSNOM project will develop and investigate a new nanophotonic chemical analysis modality to reach ultra-high detection sensitivity. We will integrate an emerging, AFM-based chemical fingerprinting spectromicroscopy technique, scattering-type Scanning Near-field Optical Microscopy (sSNOM), with graphene devices. In our experiments, the AFM tip of the sSNOM instrument will couple the light in the near-field into the graphene devices, also containing a minute amount of analyte. Thus, the spatial resolution of our technique will reach up to twenty nanometre lateral resolution, which translates to extremely small amounts of probed volumes. Through coupling between the plasmon polaritons of graphene and the analyte's molecular vibrations, we will be able to achieve ultrahigh detection sensitivity. Our experiments will spread from the terahertz to the far-infrared, which are relevant in chemical fingerprinting, at two synchrotron beamlines in Germany and France as laboratory-based light sources cannot provide high enough intensity light. To achieve the best possible coupling and detection, we will model, characterize and optimize the AFM tips and employ thermoelectric detection in the terahertz where other types of detectors are missing. Compressed sensing will enhance the signal-to- noise ratio of the measurements as less time will be necessary to accumulate a single spectrum.

• DFG Programme: Research Grants
• International Connection: France
• Cooperation Partner: Dr. Ferenc Borondics