Annular micro-nano optic fiber sensor based on α-Fe2O3@SiO2@CS imprinting for Cu(II) ion detection

• Combined with simulation analysis, an Annular micro-nano fiber coupler sensing unit was designed and fabricated. • A highly sensitive optic fiber sensor based on FSC-IIP was designed and implemented in this study for the detection of Cu 2+ . • The sensor has the advantages of strong selectivity , manufacturing difficulty, good stability and repeatability, especially selectivity, and the performance is more than 70 times higher than the other metal ions . Sensors for the rapid and easy detection of copper ions (Cu 2+ ) are crucial in drinking water and healthcare. However, this research is still challenging, such as more complicated sample pretreatment and longer detection time. In this paper, a highly sensitive optic fiber sensor for trace detection of Cu 2+ in aqueous solution is proposed. Based on the principle of intermodal interference, the coating method of surface functionalization of functional groups is adopted, and the single-mode fiber (SMF) is bent to form an annular structure to enhance the interference, and the cone pulling machine is used to perform cone pulling treatment before coating a uniform layer of α-Fe 2 O 3 @SiO 2 @CS nanocomposite imprinted material. The amino and hydroxyl groups have specific recognition functions for Cu 2+ and can chelate with Cu 2+ , thus changing the refractive index of the material, which in turn makes the interference spectrum shifted. Furthermore, Cu 2+ is chosen as the template ion to make ion-imprinted materials, and the trace detection of Cu 2+ . The results showed that the interference spectrum was red-shifted with the increase of Cu 2+ concentration in the range of 0–1 μM with a concentration dependence coefficient of 3.35 nm/log·μM, and the maximum detection sensitivity of Cu 2+ reached 1232.52 nm/μM with a good linearity of 0.994. The selectivity of Cu 2+ was more than 70 times that of other ions. In addition, the sensor has the advantages of fast response time, high stability, good reproducibility, simple fabrication and low cost.