Nitrosoarene Dimerization on Two- and Three-dimensional Gold Surfaces

In the present study, we investigated nitrosoarene dimerization on an Au(111) and on the surface of gold nanoparticles (AuNPs). High-resolution STM images revealed that 8-thiocyanatoocty1-4-nitrosobenzoate (NCS(CH2)(8)OOCC6H4NO) forms well-ordered monolayer on an Au(111) surface displaying hexagonal 3 root 3 x 3 root 3 structure. AFM data indicated that this compound also dimerize on an Au(111) surface thus forming bilayers. On contrary, adsorption of 6-(4-nitrosophenoxy)hexane-l-thiol (HS(CH2)(6)OC6H4NO) on an Au(111) leads only to poorly organized.monolayer. Furthermore, it was found that nitrosoarene derivatives 8-thiocyanatooctyl-4-nitrosobenzoate (NCS(CH2)(8)OOCC6H4NO) and 3-thiocyanatopropyl-4-nitrosobenzoate (NCS(CH2)(3)OOCC6H4NO) are present as dimers on the surface of AuNPs. There is no appreciable quantity of dimeric species with free thiocyanate termini indicating interlinkage of AuNPs through azodioxide bonds. Besides the characteristic surface plasmon band, UV-vis spectra showed an additional red-shifted band that might have origin in aggregation of AuNPs. This was further supported by TEM revealing the appearence of larger aggregates in addition to smaller AuNPs.