An Ultra-Sensitive Plasmonic Sensor for Detection Contamination in Water

Adi Salomon, Department Of Chemistry, Institute Of Nanotechnology And Advanced Materials (bina), Bar-ilan University, Ramat-Gan, Israel (adi.salomon@biu.ac.il)
Elad Segal, Department Of Chemistry, Institute Of Nanotechnology And Advanced Materials (bina), Bar-ilan University, Ramat-Gan , Israel
Emir Haleva, Department Of Chemistry, Institute Of Nanotechnology And Advanced Materials (bina), Bar-ilan University, Ramat-Gan , Israel

Owing to the increasing demand for sensor optimization, along with significant advances in nanotechnology, we present a one-micron scale label-free optical sensor, based on a plasmonic structure for detecting a minute amount of highly toxic pesticides. The detection is achieved by surface-enhanced Raman scattering; our plasmonic device is designed systematically to overlap energetically with the Raman laser in order to maximize the signal enhancement. Furthermore, the studied device differs from conventional plasmonic systems because the electromagnetic field is confined to a flat surface between triangular nano-cavital features with a specific orientation, providing an area for deposition of molecules. An enhancement factor of ~10⁶ allows for detection of trace amounts of alachlor or/and metlachlor, down to 0.4 parts-per-billion and to differentiate between them. Consequently, our device could potentially serve as a general, low-cost analyte sensing detector. The plasmonic sensors were characterized by linear transmission measurements, cathodo-luminescence, and surface-enhanced Raman spectroscopy.