Microcystin Sensing Based On All-Dielectric Nano-antenna

With the miniaturization and high integration of various devices,nano-antennas have attracted growing attention,among which dielectric nano-antennas are specially studied owing to their ability to support both electric and magnetic resonant modes,and low loss characteristics.Nowadays,the rapid development of dielectric nano-antennas leads to the emergence of numerous new applications in the fields of thermal radiation,biosensors,and so on.The Huygens’ metasurface principle and the coupled-mode theory are crucial guidelines for the structural design of dielectric nano-antennas.In biosensing,the designed dielectric nano-antennas should have high sensitivity and high quality-factor.Microcystin comes from cyanobacterial blooms,and it can seriously damage human organs when its content in drinking water exceeds a certain level.Therefore,efficient detecting methods are crucial to control water pollution.Compared with traditional methods,detecting with all-dielectric nano-antennas are more efficient,convenient,rapid,and highly sensitive.This paper focuses on the the detection of Microcystin using all-dielectric nano-antennas.The Huygens’ metasurface principle and coupled-mode theory are used to design the all-dielectric nano-antennas.The resonant characteristics of all-dielectric nano-antennas are analyzed by FDTD simulation software.The nano-antenna structures are prepared by lithography processing and the transmission spectra are measured by a homemade setup.The surface of silicon-based nano-antennas was modified by chemical coupling method to couple microcystin LR.Using glucose solutions to simulate refractive index of the background,the refractive index sensitivities of various dielectric nano-antennas are obtained.For silicon-based disc nano-antennas,the refractive index sensitivity of the magnetic resonance,which is 222 nm/RIU in experiment,is higher than that of the electric resonance.The minimum measurable concentration of microcystin by the silicon-based disc nano-antenna is 0.02 μg/L.Among the three structures with high quality factors(the rod-ring structure,the elliptical structure,and the square-hole structure),the elliptical structure has the experimentally best overall performance with refractive index sensitivity up to 788 nm/RIU,performance index FOM of 99.8,and measurable microcystin limit concentration of 0.002 μg/L,which is an order of magnitude improvement compared with the disc structure and two orders of magnitude improvement compared with the Surface Plasmon Resonance biosensor(0.2 μg/L).The advantages of all-dielectric nano-antennas,such as low loss,easy preparation,high sensitivity,and label-free detection,make them have great potential in biosensing.