Tailoring MXene-Heterometal-Doped MOF Composites via One-Step Room-Temperature Synthesis for Enhanced Electrochemical Detection of <scp>L</scp>-Tryptophan

L-Tryptophan (l-Trp) is an essential amino acid that is critical to human health and biosynthetic processes. Hence, developing a simple and sensitive l-Trp sensor is of great importance. In this study, a Ce-doped MOF-199/Ti₃C₂T_X MXene nanocomposite was developed to detect l-Trp. Density functional theory (DFT) calculation suggested that the doping of Ce can effectively enhance the electronic structure of MOF-199 and improve its adsorption capacity for l-Trp. Additionally, the integration of Ce-doped MOF-199 with Ti₃C₂T_X MXene substantially improves the conductivity of MOFs, resulting in enhanced electrocatalytic activity of the nanocomposite material. The sensor exhibits a wide linear range (0.5-156.5 μM), low limit of detection (0.18 μM), and excellent selectivity. Further, the sensor possesses excellent reproducibility, repeatability, and long-term stability. It has been successfully used to detect l-Trp in milk with excellent recoveries (99.66-104.40%).