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Porphyrins on mica: Atomic force microscopy imaging in organic solvents
- Honda, Hirotaka, Sasahara, Akira, Onishi, Hiroshi
- Colloids and surfaces 2019 v.561 pp. 194-200
- adsorption, atomic force microscopy, cobalt, colloids, hexanols, image analysis, ligands, liquids, mica, porphyrins, solvents
- Adsorption of 5,10,15,20-tetraphenyl-21H,23H-porphyrin cobalt (CoTPP) on mica immersed in organic solvents of 1-hexanol, 1-chlorohexane, and 1-phenyloctane was examined. Flat-lying CoTPP molecules were recognized in topographic images observed by atomic force microscopy. The topographic height of individual porphyrins fluctuated by 0.2 nm in a time scale of 10 s. The height fluctuation was ascribed to two states with and without a solvent molecule trapped in the axial ligand position of the CoTPP. In imaging in phenyloctane, adsorbed CoTPPs were removed by adding 1-hexylamine to the imaging solution. Hexylamine ligands would have occupied the axial position of CoTPP to hinder adsorption. In addition, two-dimensional distribution of force pushing the tip was observed in hexanol to show a layered liquid structure parallel to the mica surface.