Dual-function plasmonic sensor based on brass alloy for simultaneous detection of salinity and crude oil...

To our knowledge, this paper presents a novel plasmonic lab-on-chip (LoC) sensor with one input port and two output ports, allowing simultaneous detection of two distinct samples while preventing any cross-contamination. Finite element method (FEM) simulations were used to analyze the sensor's performance, resulting in a high sensitivity of 1780nm per refractive index unit (RIU). The sensor also achieved a figure of merit (FOM) of 65.7 within the NIR (Near-Infrared) wavelength region, with a detection limit (DL) of 5.617 × 10^-7 RIU. The metal-insulator-metal (MIM) structure of the sensor was evaluated and optimized with three different brass alloy compositions as the sensing surface. An optimal alloy composition of 70% copper and 30% zinc achieved a notable transmission coefficient (TC) of approximately -25 dB, surpassing standard optical performance while also enhancing analyte interaction through nanoscale light confinement. The MIM-based LoC sensor enables precise and accurate measurements of subtle changes in RI, making it ideal for portable, real-world applications in resource-limited environments. This sensor holds significant potential for seawater monitoring, efficiently detecting both crude oil contamination and salinity levels with minimal sample volume, contributing to improved environmental monitoring capabilities.