Correlation Reflectance Spectroscopy of Heterogeneous Silver Nanoparticles Films upon Compression at the Air/Water Interface
Résumé
Alkanethiol passivated silver nanoparticles were spread at an air/water interface to form a single monolayer film. The surface pressure isotherms and the UV-visible absorbance spectra of the film were recorded as a function of compression, whereas the dynamic behaviour was investigated by reflectance correlation spectroscopy. The film is shown to be inhomogeneous, formed by domains of particles separated by large areas of low particle density. Two distinct motions were observed: Brownian diffusion of the domains and their translational flow due to convection. From the characteristic diffusion time of the domains, and using a Stokes-Einstein analysis, the domain size is etermined as a function of surface compression. The domains start to form and grow once a fixed average article density is reached. Above this density threshold, the attractive van der Waals forces between the particles are dominating compared with the repulsion forces due to the alkanethiol chains.