Structures and Dynamic Formation Processes of Porphyrin Adlayers on Iodine-Modified Au(111) in Solution:  In Situ STM Study

Abstract

The structures and dynamic formation processes of adlayers of 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)-21H,23H-porphine (TMPyP) on both bare Au(111) and iodine-modified Au(111) in perchloric acid have been investigated in detail by using in situ scanning tunneling microscopy (STM). Highly-ordered TMPyP arrays formed on iodine-modified Au(111), whereas disordered adlayers were consistently found on bare Au(111) surface. High-resolution STM images revealed the characteristic internal shape and orientation of each TMPyP molecule in ordered adlayers. Time-dependent in situ STM allowed direct observation of the dynamics of the self-ordering processes. Before the most stable adlayer was established in a relatively small domain, several structural changes were found to occur, including the formation of a one-dimensional ordered chain at an early stage and several phase transitions in the ordered adlayers. Once the most stable adlayer was formed as a nucleus in a domain, two-dimensional growth of the domain extended over the entire area of the terraces with the final packing arrangement.

The Effect of Polarity on Coadsorbed Molecular Nanostructures of Substituted Phthalocyanine and Thiol Molecules

“…Similar results were obtained by Itaya et al on the investigation of 5,10,15,20,-tetrakis-(N-methylpyridinium-4-yl) -21 H, 23 H-porphine tetrakis-(p-tolyenesulfonate) (TMPyP) on an iodine-modified Au (111) surface using ECSTM in a perchloric acid solution. [23,24] After the sample was annealed at 70 8C for 3 h, the STM results showed that arrangement II dominated the adlayer. Although domain I still existed, its percentage deceased remarkably, which indicated that the energy of arrangement II was lower than that of arrangement I, and that domain II was thus more stable.…”

Determination of surface coverage for tetraphenylporphyrin monolayers using ultraviolet visible absorption and x‐ray photoelectron spectroscopies

“…7 Using UV/Vis with a surface roughness factor of 1.4, they calculated a density of 6.6 ð 10 13 molecules cm 2 for the parallel (ZnP4S) case and 17 ð 10 13 molecules cm 2 for the perpendicular (ZnP1S) case (Table 1). An STM image of a highly ordered adlayer of 5,10,15,20-tetrakis-(N-methylpyridinium-4-yl)-21H, 23H-porphyrin tetrakis-(ptoluenesulfonate) (TMPyP) on an iodine-coated gold surface in electrolyte solution was recorded by Kunitake et al 12,21 This side-by-side TMPyP arrangement has a surface concentration of 3.7 ð 10 13 molecules cm 2 (Table 1). 12 All of the parallel densities are within a factor of 3, whereas there is an order of magnitude spread for the perpendicular densities of porphyrin surface concentrations.…”

Recent Progresses of Electrochemical Surface Science ∼Importance of Surface Imaging with Atomic Scale∼

“…67 In this study, we found for the first time that TMPyP forms highly ordered molecular arrays via self-ordering on an iodine-modified Au(111) electrode in 0.1M HClO 4 . 67 In a high-resolution image, the flat-lying TMPyP molecule is visible as a square with four bright spots.…”

“…67 In this study, we found for the first time that TMPyP forms highly ordered molecular arrays via self-ordering on an iodine-modified Au(111) electrode in 0.1M HClO 4 . 67 In a high-resolution image, the flat-lying TMPyP molecule is visible as a square with four bright spots. The center-to-center distance between the bright spots, measured diagonally, was 1.3 nm, which is nearly equal to the distance between two pyridinium units, measured diagonally.…”

“…67 Although the TMPyP molecules adsorbed directly on the Au(111) surface could be observed by STM, the adsorbed molecules did not form ordered adlayers. Disordered adlayers formed on a bare Au(111) surface suggested that strong interactions, including chemical bonds between the gold substrate and the organic molecules, prevented self-ordering processes from occurring; therefore, surface diffusion of the adsorbed molecules must be involved.…”