High-Performance Biosensor by using Au Nanoparticles and Grating for Sensing Waterborne Bacteria in Drinking Water

Water is an urgent human need; however, many people have difficulties gaining access to the safe and clean drink water. A large number of individuals around the world lose their lives due to waterborne bacterial infections. One of the most innovative techniques to solve this problem is known as biomolecular detection method. This can be followed through monitoring subtle changes in the refraction indices, where it is based on implementation of chemical and biological sensors. In the present study, based on synthesis of gold nanoparticles (Au-NPs) on a grating structure a nanoscale optical sensor is proposed. The proposed structure operates as a refractive index (RI) sensor for real-time and label-free detection of waterborne bacteria. Afterwards, we proceed with a cleverly designed RI biosensor optimized for waterborne diseases caused by Escherichia coli (E. coli) pathogen. This bacterial pathogen of various concentrations would be detectable by the proposed biosensor. Using of Au-NPs in arrayed form as a plasmonic material yields multiple advantages as: i) it provides a wide range of medical diagnostics and environmental monitoring applications, and ii) the spectrum can be fine-tuned by controlling Au-NP array. Hence, the present study would lead to the development of plasmonic sensor with a sensitivity of as high as ۴۶۷.۱ nm/RIU (refractive index unit), in near-infrared region. In fact, the proposed structure is capable of detecting a single bacterium contamination and determining the concentration level of bacterial spectrum in drinking water, as well.