Comparative evaluation of synergistically functionalized CNT-Ag plasmonic hybrids for sensitive and stable SERS...

Developing sensitive and reliable SERS substrates requires precise control over nanoparticle distribution, interfacial interactions, and plasmonic coupling. In this study, chemically functionalized carbon nanotubes (CNTs), including oxidized CNTs (fCNT) and amino-functionalized CNTs (aCNT), were integrated with Ag nanoparticle arrays to construct CNT@Ag hybrid SERS platforms. The CNT networks form a porous and interconnected architecture that integrates with Ag nanoparticles, enabling controlled nanoparticle anchoring and preserving plasmonic activity. The results demonstrate that CNTs act as active co-enhancing components rather than passive coatings, regulating nanoparticle distribution, promoting interparticle coupling, and enhancing analyte adsorption. Particularly, fCNT@Ag exhibits significantly improved SERS performance compared to aCNT@Ag, attributed to stronger electrostatic interactions, higher nanoparticle anchoring density, and increased hotspot formation. The fCNT@Ag substrate achieves a low detection limit of 1.9 × 10^-8 M and an enhancement factor of 2.0 × 10⁵, while maintaining excellent long-term stability with >95% signal retention after 75 days. These findings demonstrate that surface functionalization plays a critical role in tuning plasmonic-carbon interactions and provide a rational strategy for designing stable, reproducible, and high-performance CNT-based hybrid SERS substrates for trace molecular detection.