Adsorption-driven SERS enhancement by Ti₃C₂T_x quantum dot-AuNP assembled interfaces for sensitive detection of Sudan...

Sudan dyes, as illegally added food colorants, pose significant risks to human health due to their potential toxicity and carcinogenicity. Conventional chromatographic and mass spectrometric methods for Sudan dye detection typically require labor-intensive sample pretreatment and involve substantial time and economic costs. Surface-enhanced Raman scattering (SERS) has emerged as a rapid and sensitive analytical technique; however, its application to lipophilic analytes remains challenging because of the limited affinity between hydrophobic targets and SERS-active substrates, hindering effective signal enhancement. Therefore, developing adsorption-enhanced SERS substrates for efficient enrichment and sensitive detection of hydrophobic dyes is of great significance for food safety monitoring.

In this study, a high-performance SERS platform based on Ti₃C₂T_x quantum dot (MQD)-AuNP assembled interfaces was developed, with preparation conditions carefully optimized to ensure stable performance. Adsorption performance was evaluated using multiple isotherm and kinetic models, demonstrating an ultrahigh adsorption capacity >4000 mg/g). The MQD/AuNPs substrate exhibited ∼14-fold enhancement in SERS intensity compared to AuNPs alone, with excellent signal uniformity (mapping RSD <15%) and reproducibility (RSD <20%). The platform also showed a broad linear response range and stable signal output across repeated measurements. Using 1595 cm^-1 as the characteristic peak, the method achieved a detection limit of 10 μg/kg and a quantification limit of 100 μg/kg. In chili powder, recoveries ranged from 95.2 to 120.5%, confirming reliable quantitative performance. Compared with conventional chromatographic methods and reported SERS approaches, this platform maintains comparable sensitivity while significantly improving detection efficiency.

This work establishes an adsorption-driven SERS enhancement strategy by integrating high-capacity MQDs with plasmonic nanostructures. The synergistic combination of analyte enrichment and signal amplification enables rapid and sensitive detection without increasing analytical cost. This platform provides a practical and efficient approach for on-site screening of lipophilic contaminants in complex food systems.