Ordered Au Nanoparticle Array on Au(111) through Coverage Control of Precursor Metal–Organic Chains (original) (raw)

2016, The Journal of Physical Chemistry C

Metal−organic overlayer structures formed by 1,4phenylene-diisocyanide (PDI) and Au adatoms on Au(111) in UHV, their stability in air, and the tip-induced Au nanoparticle formation on PDI−Au(111) surfaces in air were investigated using scanning tunneling microscopy (STM) and vibrational spectroscopy. This study reveals that the distribution of Au nanoparticles created during tip-induced release of Au atoms from molecule-Au adatom complexes shows strong dependence on the PDI coverage. Ordered Au nanoparticle arrays form in the medium-coverage regime, while more disordered distributions are observed at low and saturation coverages. The different distributions of Au nanoparticles are a direct consequence of the coverage-dependent assembly of (PDI−Au) n chains, their different stability in air, and a templating effect of the Au(111) surface, which is most pronounced for medium coverage, where phases of densely packed (PDI−Au) n chains and disordered PDI−Au assemblies are confined, respectively, to the fcc and hcp regions of the (22 × √3) surface reconstruction of Au(111). The Au nanoparticles nucleate preferentially in the disordered or defective regions of the PDI−Au precursor overlayer, and their formation requires ambient air and high negative tip-bias, suggesting an electrochemical initiation of Au release from the molecule−Au adatom complexes.