PESTICIDE SENSING BY PLASMONIC NANO CAVITIES AT THE SUB-MICRON SCALE

Elad Segal, Chemistry/nanotechnology, Bar-Ilan University, Ramat-Gan, Israel (elad.segal87@gmail.com)

Despite the advance in design and fabrication of plasmonic sensors, there are still many difficulties due to physical limitations which result in instrumental malfunctions. Recently, we showed that fabrication of nano-cavital features (~1 µm²) on a flat metallic surface can be utilized to achieve strong and localized fields. ^[1-2] These strong fields can be confined to nanometric area, and their plasmon frequency can be controlled by light polarization, geometrical orientation, etc. These findings counter-intuitively show that there is no need for either sharp tips or small nano-gaps between the features for “hot-spot” generation. We introduce newly-developed tunable plasmonic devices. The devices are easily fabricated using highly accurate focused ion beam (FIB) to mill nano-plasmonic structures with different geometries. Their performance as Raman enhancers is tested using an analyte called alachlor - a pesticide which has a significant impact on human and eco population worldwide (also in Israel). Alachlor is used in immense volumes as an herbicide for crops as: corn, soybeans, potatoes, etc. Alachlor is not only considered as an irritant (skin/eyes), but it can also harm the liver, kidneys, spleen, and even found to be carcinogenic. Using methods as: optical and electronical microscopy, Raman spectroscopy and cathode-luminescence, we explain and demonstrate how to tune these nano-sensors as Raman enhancers. We show that even a sub nM level of analyte (<0.4 ppb for alachlor) can be detected. ^[3]

 

[1] E. Segal, A. Weissman, D. Gachet, and A. Salomon, Nanoscale, 2016, 8, 15296.

[2] A. Weissman, M. Galanty, E. Segal, O. Shavit, and A. Salomon, Adv. Opt. Mat., 2017, 5, 1700297.

[3] E.Segal, E.Haleva, and A. Salomon, submitted, 2017.