Li+ concentration detection based on Li/Al-LDHs modified optical microfiber coupler

The detection of ultra-low concentrations of lithium ions (Li + ) is of paramount importance for protecting human health and preserving the ecological environment. This paper proposes a fiber-optic sensor based on lithium/aluminum layered double hydroxides (Li/Al-LDHs) modified optical microfiber coupler (OMC). Firstly, the optimal diameter of the OMC is determined through simulation analysis to optimize the sensor parameters. Secondly, functional group functionalization is employed to facilitate a robust binding of the Li/Al-LDHs to the surface of the optical fiber. Lastly, the efficacy of the sensor in detecting low concentrations of Li + was validated through experimental means. The results demonstrated that the sensor exhibited a maximum detection sensitivity of 334.222 nm/μM and a limit of detection (LOD) of 1.272 nM within the range of 1–10 nM, exhibiting good linearity (R 2  = 0.986). Furthermore, the sensor displayed excellent stability, selectivity and response time, indicating its potential for application in the detection of Li + concentration in aqueous environments.