Interfacial engineering of MXene-PDA/WS₂ nanocomposite heterostructures for ultrasensitive SERS detection of 4-Nitroaniline.

The excessive release about 4-nitroaniline (4-NA), an extremely dangerous substance widely used in the manufacturing of plastics, rubbers, medicines, fuel additives, explosives, pesticides, and dyestuffs, poses significant environmental risks due to its mutagenic, carcinogenic, and teratogenic effects. Therefore, monitoring and detecting 4-nitroaniline (4-NA) in environmental matrices is critical to mitigate its hazardous effects. The evolution of highly sensitive platforms for surface-enhanced Raman scattering (SERS) is pivotal to advancing next-generation molecular detection technologies. Herein, we report a robust MXene-PDA/WS₂ heterostructured nanocomposite engineered via in situ polydopamine (PDA) coating of MXene, followed by electrostatic assembly of WS₂ nanosheets. This hierarchical 2D2D network, orchestrated by PDA-driven interlayer adhesion and cross-linked interfaces, provides a unique bonding and interface-engineering framework that yields remarkable SERS signal amplification. The optimized MXene-PDA/WS₂ nanocomposite exhibits a SERS intensity approximately six fold higher than that of individual MXene, PDA, or WS₂ components. This enhancement arises from synergistic electromagnetic and chemical mechanisms, wherein the complementary energy-level alignment among MXene, PDA, and WS₂ facilitates efficient interfacial charge transfer, stabilizes 4-nitroaniline (4-NA) molecules, and promotes their adsorption and confinement within plasmonically active regions. The sensor demonstrates an impressive enhancement factor of 2.28 × 106, enabling an ultralow detection limit of 1.0 × 10-9 M across a dynamic range of 10-1-10-9 M. Furthermore, the PDA interlayer in the composite significantly improves MXene's oxidative stability, ensuring outstanding reproducibility of RSD 6.75% and long-term practical applicability. This work introduces a versatile SERS platform with superior sensitivity, molecular selectivity, and durability, offering a promising route toward high-performance analytical devices for environmental monitoring and molecular diagnostics.