Self-assembled silver nanoparticle films at an air–liquid interface and their applications in SERS and electrochemistry

In this paper, we present a novel technique to prepare silver nanoparticle films by controlling the self-assembly of nanoparticles at an air–liquid interface. In an ethanol–water phase, silver nanoparticles were prepared by reduction of AgNO3 aqueous solution with NaBH4 in the presence of cinnamic acid. It was found that the silver nanoparticles in this process could be trapped at the air–liquid interface to form 2-dimensional nanoparticle films. The morphology of nanoparticle films could be controlled by systematic variation of the experimental parameters. It is worth noting that the nanoparticle films could serve as the active substrates for surface-enhanced Raman scattering (SERS). 4-Aminothiophenol (4-ATP) molecule was used as a test probe to investigate the SERS sensitivity of different nanoparticle films. The results indicated that the nanoparticle films showed excellent Raman enhancement effect. Furthermore, the nanoparticle films prepared by our strategy were found to be efficient electrocatalysts for anodic oxidation of formaldehyde in alkaline medium.