In situ synthesis of nickel-substituted zeolitic metal-organic framework on Ti3C2 MXene for enhanced electrocatalytic sensing of L-tryptophan

Herein, in situ synthesis of a nickel-substituted zeolitic metal-organic framework, Ni-ZIF-8, (referred to NZM) on Ti₃C₂ MXene enhanced the functionalities for the electrocatalyst sensing of L-tryptophan (L-Trp). The exceptional electrical conductivity of the Ti₃C₂ MXene complements the high porosity of NZM, resulting in synergistic effects that improve charge transport and stability. The dual functionality of NZM/Ti₃C₂ enhanced their high electrical conductivity through delamination and improved accessibility of the electrolyte to the surface of the active materials. Furthermore, the incorporation of Ni²⁺ and coordination of 2-methylimidazole (2-MeIM) as a nitrogen source with enhanced electronegativity improved the interaction between the NZM and the L-Trp molecules. The proposed electrode exhibited remarkable sensitivity and selectivity for the analysis of L-Trp, providing a broad dynamic range (5 nM-200 μM) and a low detection limit of 0.1 nM. In addition, the prepared sensor was successfully used to monitor L-Trp in a complex milk matrix.