Surface-enhanced Raman scattering on a zigzag microfluidic chip: towards high-sensitivity detection of As(III)ions

In this study, a microfluidic platform was combined with surface-enhanced Raman scattering (SERS) to implement the rapid quantitative detection of As(III) ions in a continuous flow. Silver nanoparticles (AgNPs) were used as the SERS enhancement substrate, and glutathione (GSH) with 4-mercaptopyridine (4-MPY) was conjugated on the surface of the AgNPs. When As(III) ions encountered GSH/4-MPY functionalized AgNPs, the original monodispersed probes would aggregate because As(III) ions had a strong affinity to the GSH. As a result, Raman signals of 4-MPY adsorbed on the surface of the AgNPs were improved and the As(III) ions could be detected. Due to the advantages of microfluidics technology combined with SERS detection, the highly sensitive and reproducible analysis of As(III) ions was realized in several minutes. The proposed method allowed the quantitative analysis of As(III) ions with a linear range (3 to 200 ppb), and the limit of detection (LOD) of the As(III) ions was determined to be 0.67 ppb. The real water sample was also analyzed to confirm the practicability of the method and the consumption of several microliters of the sample was found to be environmentally friendly. This method also showed great potential in applying SERS combined with a lab-on-a-chip technique in the area of environmental monitoring with a high sensitivity and in an environmentally friendly way.