Fiber-optic Mach–Zehnder interferometer based on α-Fe2O3@MoS2 functionalization for Cd2+ trace detection

The detection of ultra-low Cd2+ concentration is of great significance to protect human health and maintain the stability of the ecological environment. Therefore, an MZI fiber optic sensor based on α-Fe2O3@MoS2 nanocomposite functionalization is proposed. Firstly, the optimal parameters of the sensor are explored, that is, the optimal lengths of no-core optical fiber (NCF) and few mode optical fiber (FMF) are analyzed by simulation. Secondly, the functional group functionalization method is used to tightly bond the α-Fe2O3@MoS2 nanocomposites with the fiber surface. Finally, experiments verify that the designed fiber sensor can achieve ultra-low trace detection of Cd2+. The results show that in the range of 0–100 μM, the maximum detection sensitivity of Cd2+ is 475.19 nm/μM, and the minimum detection concentration is 0.001 μM (about 0.18ppb). At the same time, the sensor also has good performance in terms of selectivity, stability and responsiveness, and has potential application potential in the detection of Cd2+ in water environment.