Core-satellite nanocomposites via PEI-induced self-assembly for enhanced SERS sensing of thiram and ciprofloxacin

Developing sensitive, reliable, and robust surface-enhanced Raman spectroscopy (SERS) substrates relies heavily on fabricating a substantial number of hot spots. In this study, we present a straightforward method for creating Ag@PEI/Ag core-satellite nanocomposites. Large Ag nanospheres serve as the cores, and smaller Ag nanoparticles are electrostatically assembled around them through the introduction of polyethyleneimine (PEI). This assembly process generates numerous hot spots not only between two Ag satellites but also between the inner Ag core and Ag satellites, thanks to the sub-nm PEI interlayer. The nanocomposites exhibit great potential for SERS analysis, enabling effective sensing of various organic pollutants, such as thiram and ciprofloxacin, using a portable Raman spectrometer. Notably, these nanocomposites obtain an exceptional detection limit of as low as 10−8 M for them, which falls below the safety level set by the United States Environmental Protection Agency. Additionally, the substrates demonstrate excellent uniformity, reproducibility and storing stability. Consequently, the Ag@PEI/Ag core-satellite nanocomposites hold great promise as efficient SERS platforms for reliable and highly sensitive monitoring of food safety and environmental analysis.