Ultrasensitive metasurface-based sensors for fingerprint spectra extraction of L-glutamate at ultra-low concentration

Terahertz-infrared (THz-infrared) absorption spectroscopy comprises distinctive spectroscopic data that serves as a potent method for the detection and analysis of biomolecules, owing to its capability to capture unique fingerprint spectral patterns associated with different structural substances. Nonetheless, the extraction of molecular characterization data with utmost sensitivity for substances present in low concentrations remains a formidable task that necessitates resolution, especially for the micro detection of neurotransmitters such as L-glutamate intricately linked to neurological disorders. Here, we construct Fano resonant modes with strong near-field by breaking the symmetry of the metallic split ring in the meta-atom, benefiting the susceptible substance detection. By scaling the structural parameters, a metasurface-based sensor working at the range of 1.15 to 2.69 THz was fabricated, which consisted of 15 metasurfaces operating at different resonance frequencies. And in agreement with results obtained by typical transmission absorption spectroscopy analysis of 0.1 mg tablets, the molecular fingerprint information of L-glutamate has been experimentally identified by comparing the resonance intensity changes with/without covering 5μg of L-glutamate, implying an increased detection sensitivity to 1/20. the proposed metasurface-based sensors with broadband Fano resonances are deemed to provide a new paradigm for enabling low-concentration, easy-to-use, and label-free biomolecule research and promise to drive the development of integrated non-destructive testing medical devices.