Nb2CTx MXene-tilted fiber Bragg grating optofluidic system based on photothermal spectroscopy for pesticide detection.

An optofluidic system based on photothermal spectroscopy is proposed, which combines molecular photothermal effect with Nb2CTx MXene-tilted fiber Bragg grating (TFBG) for the detection of organophosphorus pesticides (OPs) with temperature compensated. Under the irradiation of excitation light, the photothermal effect of OPs produces a detectable change in the refractive index of the sample, and the concentration of chlorpyrifos can be quantified using TFBG. The Nb2CTx MXene coated TFBG allow more molecules to be absorbed on the surface of TFBG, which enhances the interaction between light and matter, and improves the sensitivity of detection. The temperature compensation is performed by referring to the core mode of TFBG, thereby eliminating the influence of ambient temperature on the photothermal detection. The experimental results show that the sensitivity reaches 1.8 pm/ppm with a limit of detection (LOD) of 0.35 ppm, and the obtained temperature compensation coefficient is 4.84 ppm/°C. This photothermal biosensor has the advantages of low LOD, temperature compensation and real-time online monitoring, making it a good candidate in medicine, chemistry and environmental monitoring.