Hybrid plasmonic-photonic nano sensor with zeptogram sensitivity
Résumé
Thanks to their small sensing volume, nanosensors based on localized surface plasmon resonances (LSPR) allow the detection of minute amounts of analytes, down to the single molecule limit. However, the detected analytes are often large molecules, such as proteins. The detection of small molecules remains largely unexplored. Here, we use a hybrid photonic-plasmonic nanosensor to detect a small target molecule (pyridine). The sensor’s design is based on a dielectric photonic microstructure acting as an antenna, which efficiently funnels light towards a plasmonic transducer and enhance the detection efficiency. This sensor exhibits a limit of detection as small as 10−14 mol.L−1. Using a calibration procedure based on electrodynamical numerical simulations, we compute the number of detected molecules. This yields a limit of detection in mass of 4 zeptograms (1 zg = 10−21 g), a record value for plasmonic molecular sensors. Our system can hence be seen as an optical molecular weighing scale, enabling room temperature detection of mass at the zeptogram scale.