Ultrasensitive SERS detection of trace malachite green using noble-metal-free EuFeO₃/ZnO@Ti₃C₂T _x MXene...

Malachite green (MG), an illegally used aquaculture dye with carcinogenic and mutagenic effects, remains a persistent contaminant in aquatic environments and food chains, necessitating the development of highly sensitive and reliable analytical platforms for trace-level monitoring. In this study, a hierarchical EuFeO₃/ZnO@Ti₃C₂T _x MXene heterostructure was successfully engineered as a noble-metal-free surface-enhanced Raman scattering (SERS) substrate for ultrasensitive MG detection in aquaculture water. The hierarchical assembly of EuFeO₃ and ZnO on conductive Ti₃C₂T _x MXene generated electronically coupled heterointerfaces that facilitated rapid charge transfer and efficient carrier transport. Structural and spectroscopic analyses confirmed the successful formation of the ternary architecture with intimate interfacial integration, enhanced visible-light absorption, enlarged surface accessibility, and significantly suppressed charge-carrier recombination compared with pristine and binary systems. Consequently, the EuFeO₃/ZnO@Ti₃C₂T _x substrate delivered markedly amplified Raman responses, achieving ultrasensitive MG detection at concentrations as low as 10^-9 M with an enhancement factor of 7.31 × 10⁶. The substrate further demonstrated excellent linearity, reproducibility, and stable analytical performance in complex aquaculture water matrices, achieving recoveries ranging from 82.7% to 111.8% with relative standard deviations below 13.8%. Mechanistic investigations revealed that the enhanced SERS activity was predominantly governed by chemical enhancement arising from interfacial charge-transfer interactions between the heterostructure and MG molecules, while the conductive MXene scaffold accelerated electron transport and strengthened analyte-substrate coupling. This work not only demonstrates an effective strategy for constructing MXene-based semiconductor heterostructures with enhanced charge-transfer characteristics, but also provides a promising noble-metal-free SERS platform for practical food safety monitoring and environmental contaminant detection.