Plasmonic optical fiber gratings based on few-layer Ta₂C MXenes for refractive index sensing

Tilted fiber Bragg grating (TFBG) is a widespread approach for developing refractive index (RI) sensors. The unique optoelectronic properties exhibited by MXene are expected to enhance the performance of TFBG-SPR sensors. In this study, a Ta₂C coating appropriate for sensing was obtained by optimizing the photo-deposition time, which addressed the challenge of preparing large areas of MXene. The uniform coating of the few-layer Ta₂C increases the wavelength sensitivity and FOM of the sensor to 229.5 nm/RIU and 2228.15 respectively. This significant enhancement was attributed to an ordered MXene phase of the grown Ta₂C. The energy band theory verified the metallic nature of the Ta₂C and the amplification effect on the RI response. Finite element analysis demonstrated that the stronger absorption band of Ta₂C facilitated the generation of surface plasmon polariton. Based on the above benefits, the sensor detected melamine in milk with a detection limit of 7.9 × 10^-9M. The TFBG/Au/Ta₂C sensor is a promising approach for biochemical analysis and trace detection.