Surface Plasmon Resonance Fiber Sensor for Trace Ferric Ion Detection With Temperature Compensation

The ecological environment had encountered severe pollution in recent decades, and the trace metal ions (TMIs) particularly showed high threat to human health, where the ferric ion (Fe3+) is one of the most common TMIs. In this article, a surface plasmon resonance (SPR) fiber sensor was utilized to achieve the detection of trace amount of Fe3+, which owes to the specific reaction between Ag film and Fe3+. The change in Fe3+ level could lead to the increase of the refractive index (RI) on the Ag film surface, and such variation would be monitored by the change in resonance wavelength, and a sensitivity of 2.32 nm/lgM was achieved in the range of 8 pM-80 mM with a detection limit (LOD) of 7.917 pM. Another detection channel was also designed for the compensation of temperature interference, which used polydimethylsiloxane (PDMS) to elevate the sensitivity toward temperature change. By combining these two channels together, the trace Fe3+ SPR fiber sensor was tested in simultaneous Fe3+ level and temperature change, and the accurate Fe3+ concentration could be acquired after the temperature compensation. The proposed sensor also indicates high stability, fast response, and ion selectivity, which shows the potential for future environmental monitoring.