Ion-imprinted-polymer coated fiber-optic SPR sensor for detection of trace Cr3+ in water

A fiber-optic surface plasmon resonance (SPR) sensor based on the trivalent chromium-ion imprinted polymer (Cr3+-IIP) was proposed and fabricated. A small core-diameter fiber (SCF) with a length of 1 cm is spliced between two multimode fibers (MMFs) to form the MMF-SCF-MMF sensing structure. A 67-nm thick Ag film was evaporated on the outside surface of the SCF, and then Cr3+-IIP and nonionic imprinted polymer materials were respectively coated on the surface of the Ag film and then the fiber-optic SPR sensor was obtained. The results show that with the increase of Cr3+ concentration in the range of 0–1.1 µM, the SPR peak indicates redshift with 80.5 nm. The sensitivity and linearity of the sensor are 71.7 nm/µM and 0.994, respectively. The limit of detection of the sensor is about 0.041 μM (2.145 ppb). The fiber-optic SPR sensor is expected to be applied to the detection of trace Cr3+ ions in water.