On the structure and formation of self-assembled lattices of gold nanoparticles

The structure and ordering of nanoparticles of gold functionalized with n-a lkyl thiol molecules are studied both experimentally and theoretically. Sam ples where produced using n = 6 to n = 16 alkyl thiol molecules. High Resol ution Electron Microscopy coupled with image processing was used to study t he gold particle structure. The details of the particle structure are discu ssed. We found that when the gold surface is saturated with thiol molecules there is some tendency to produce molecules with a disulphide structure. W e also show that ordered arrays of particles can be produced using Langmuir -Blodgett techniques. The crystal structure of the films produced is studie d and found to be 3D hcp. We also report that thiol covered gold particles with a size of similar to 5 nm present a rounded shape suggesting that thio l molecules might induce an isotropic surface energy. It is found in the th eoretical calculations that a strong bond between gold and sulphur is requi red to stabilize the complex metal-n-alkyl thiol. It is predicted that othe rwise a heavily distorted nanocore will be formed. This is contrary to the observed structure of the particles.