Electrostatic enhanced terahertz metamaterial biosensing via gold nanoparticles integrated with biomolecules.

Terahertz spectroscopy has drawn great interest for the detection and characterization of biological matter, but its limited sensitivity to biomolecules with weak changes in dielectric properties with varying concentration has hinders potential bio-sensing applications. Here, a novel terahertz sensor was developed for enhancing the ability to detect biomolecules based on two electromagnetically induced transparency (EIT) metamaterials coupled with gold nanoparticles (AuNPs) integrated with biomolecules. The electrostatic interaction between AuNPs and positively charged biomolecules generates localized field enhancement at the biomolecule-metamaterial interface, resulting in a threefold increase in sensitivity for positively charged histidine that exhibit weak dielectric property changes with varying concentration. As a contrast, glucose shows a weaker effect due to its electrostatically neutral nature. Experimental studies reveal that by evaluating the modulation depth (MD) and modulation enhancement (ME) factors of the transmission peak for histidine and glucose in the presence of AuNPs, we achieve and enhance intuitive detection and discrimination of these biomolecules. Additionally, a two-EIT metamaterial with a 1 × 2 pixel array enables multiparameter imaging, visualizing the concentration and spatial distribution of biomolecules. Our results not only significantly improve the response sensitivity of biomolecules with weak dielectric properties in the terahertz domain, but also provide a new idea for developing high-sensitivity functionalized terahertz biosensors and advancing multi-biomolecular analysis and imaging techniques.