Solvent-Induced Structural Transitions of a 1,3,5-Tris(10-ethoxycarbonyldecyloxy)benzene Assembly Revealed by Scanning Tunneling Microscopy

The effect of solvent on a two-dimensional (2D) self-assembly of 1,3,5-tris(10-ethoxycarbonyldecyloxy)benzene (TECDB) has been systematically investigated by scanning tunneling microscopy. Through careful investigation of the solvent effect on molecular self-assembly, the solution concentration is also found to be a factor in assembly formation and transition. The same self-assembled structure is obtained using 1-phenyloctane, 1-octanol, n-tridecane, and n-tetradecane as a solvent under high solution concentrations. When the solution concentration decreases, a structural transition of the TECDB adlayer in 1-phenyloctane can be seen and n-tetradecane molecules coadsorb with TECDB molecules, forming two kinds of patterns. Furthermore, the affect of mixed solvents on the TECDB adlayer is also investigated. No self-assembled monolayer of TECDB is observed in 1,2,4-trichlorobenzene. After all samples are placed in ambient conditions over 24 h, a denser-packed structure appears, which corresponds to the result using chloroform as the solvent. The results demonstrate that the solvent plays an important role as not only a simple dispersant but also a counterpart in forming the 2D molecular self-assembly and provides an efficient approach for the fabrication and control of the TECDB molecular nanostructure by changing the solvent and solution concentration.