Surface-enhanced Raman scattering enhancement using a hybrid gold nanoparticles@carbon nanodot substrate for herbicide detection†

The widespread distribution of herbicides in the environment poses a significant risk to human health and wildlife. Surface-enhanced Raman scattering (SERS) has emerged as a powerful technique for detecting and analyzing herbicides. However, developing a low-cost, highly sensitive, reproducible, stable, and Raman-active nanostructured substrate for herbicide detection remains a particular challenge. In this research, a nanohybrid substrate consisting of gold nanoparticles@carbon nanodots (AuNPs@CNDs) was synthesized by reducing HAuCl₄ in the presence of CNDs at 100 °C. The optical, chemical, and physical properties of CNDs, AuNPs, and the hybrid AuNPs@CND substrates were thoroughly investigated using various techniques including UV-vis spectrometry, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and CytoViva darkfield and hyperspectral imaging. The SERS effect of the substrates was evaluated using rhodamine 6G (Rh6G), a Raman-active probe, and two groups of herbicides containing mesotrione or S-metolachlor. The results demonstrated a significant signal amplification in the SERS spectra of Rh6G and herbicide molecule detection using the AuNPs@CND substrate compared to bare CNDs and AuNPs alone. This suggests that the nanohybrid AuNPs@CND SERS substrate holds promise for the detection of herbicides and other organic compounds in environmental applications.