Synthesis of Cu-Ag core-shell nanoparticles as highly active surface-enhanced Raman scattering substrates for sensitive detection of caffeic acid

Core-shell nano-metal structures as SERS probes have drawn attention and have been applied to detecting analytes at low concentrations. Here, we have developed a novel SERS probe composed of Cu-Ag for the quantitative, rapid and ultrasensitive detection of caffeic acid. The surface of Cu-Ag was modified with 4-mercaptophenylboronic acid (4-MPBA) to allow the probe to detect caffeic acid, wherein 4-MPBA specifically binds to caffeic acid by an esterification reaction. The results obtained in this work show that the SERS performance of the 4-MPBA substrate is better than that of the Cu-Ag substrate. To determine the binding of caffeic acid to 4-MPBA, the B-OH stretching vibration at 1170 cm(-1) was selected as the representative signal. It was found that there is a linear relationship between the intensity of the peak at 1170 cm(-1) and the concentration of caffeic acid.