Long period fiber grating sensor coated with MXene (Ti3C2TX) functionalized by poly-levodopa for rapid detection of Cu2+

Abstract

An optical sensor based on long period fiber grating (LPFG) modified by MXene-polymer composites was proposed to detect Cu2+. Ti3C2Tx is prepared by etching aluminum with hydrofluoric acid (HF) from the Ti3AlC2. MXene-based materials demonstrate the potential to adsorb multi-pollutants, but the adsorption performance is limited. Mussel-inspired poly-levodopa (PDOPA) modified Ti3C2Tx, with a simple and eco-friendly reaction process, has been proven to enhance the adsorption capacity for Cu2+. The resonance spectrum of LPFG is sensitive to changes of refractive index (RI) aroused by Cu2+ adsorption on the sensing film. Thus, the Cu2+ sensing performance of the LPFG sensor coated with Ti3C2Tx and PDOPA-Ti3C2TX was separately investigated. The best sensitivity of the PDOPA-Ti3C2TX-LPFG was measured to be 3.48 × 10−4 nm/ppb (0–103 ppb) and the detection limit was determined to be 10.34 ppb (0.162 μM), which was obviously better than the results of 1.80 × 10−4 nm/ppb and 25 ppb (0.393 μM) with only Ti3C2Tx coated. Moreover, the stability and reusability of the sensor were also evaluated. This sensor provides a new approach for metal ions detection in the water environment.