Synergistic electromagnetic and chemical enhancements in Al/C₃N₄/Ag@C for Raman-based chlortetracycline sensing

Because of their persistence, bioactivity, and resistance potential, antibiotic residues seriously threaten ecology and human health. Among these pollutants, the frequently used veterinary antibiotic chlortetracycline regularly accumulates in aquatic systems and causes significant hazards by promoting microbial resistance and ecological disturbance. For effective monitoring and mitigation of such risks, a variety of analytical techniques have been developed for identifying trace pollutants within environmental matrices. Surface-enhanced Raman scattering (SERS), among these analytical techniques, stands out for its highly sensitive capability to detect trace substances in the environment.

We successfully constructed a two-dimensional Al/C₃N₄/Ag@C nanocomposite substrate exhibiting remarkable performance in the SERS detection of chlortetracycline. By means of a successive layering technique, ultrathin graphitic carbon nitride (g-C₃N₄) and uniformly distributed carbon-coated silver nanoparticles (Ag@C) were deposited onto chemically etched aluminum sheets. The resulting Al/C₃N₄/Ag@C composite significantly enhanced Raman signals by uniquely combining electromagnetic and chemical enhancement mechanisms. Outperforming conventional and recently reported substrates, this composite achieved a detection limit of 6.91 × 10^-12 M for the standard probe molecule Rhodamine 6G and a remarkable 1.11 × 10^-14 M were obtained for chlortetracycline. The uniform structure, excellent repeatability, and high stability of the hybrid substrate were validated through comprehensive characterization, including electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and finite-difference time-domain simulation. Furthermore, the fabrication process is highly reproducible and easily scalable for practical environmental monitoring applications.

This work presents a robust and scalable SERS substrate, Al/C₃N₄/Ag@C, which exhibits extraordinary sensitivity and stability for the detection of antibiotics in environment. Its novel combination of chemical and electromagnetic enhancements not only overcomes common challenges related to nanoparticle oxidation and signal instability but also provides consistent ultra-trace level monitoring of chlortetracycline in water bodies. Thus, it substantially improves useful antibiotic monitoring methods and presents great prospects for environmental protection and public health safeguarding.