A multifunctional Si3N4 nanobrick metasurface for sensing

Abstract

A metasurface composed of Si₃N₄ with a lower refractive index can result in more electromagnetic energy leaking into the surrounding environment compared with other dielectric materials, which is beneficial for sensing applications. However, the research on Si₃N₄ metasurfaces in the sensing field remains relatively scarce to date. We focus on two different sensing applications to highlight the potential versatility of Si₃N₄ nanobrick metasurfaces. On the one hand, exploiting colors corresponding to reflection spectra, colorimetric sensors in different refractive index surroundings are addressed with distinguishable color changes by naked eyes, and a sensitivity of about 104 nm per RIU at a resonance wavelength of 541 nm is obtained. On the other hand, the potential for carcinoembryonic antigen (CEA) detection is demonstrated by abnormal spectral blueshifts after specific binding of functionalized gold nanoparticles onto the Si₃N₄ nanobrick surface in the presence of CEA. These results open the path to the application of Si₃N₄ nanobrick arrays as multifunctional metasurfaces for colorimetric sensors, displays, anti-counterfeiting, and biosensors.