Tetraphenylethylene (TPE) and its derivatives (H
4TCPE and H
4ETTC) have great potential in such applications as biological and chemical sensors [
87-
89] and optoelectronic materials [
90-
94]. The H
4TCPE molecules formed well-aligned lamellar structures at the HA/HOPG interface, co-assembled with HA
via hydrogen bonds (
Fig. 5a). Due to the spatial characteristics of the propeller structure, all of the phenyl groups of the H
4TCPE molecule remain perpendicular to the HOPG surface and interact with the substrate
via edge-to-face
π-
πinteraction. While H
4ETTC molecules are observed as bigger X-shaped molecules and self-assemble into quadrilateral structures (
Fig. 5c). To further investigate the self-assembly behaviors of H
4TCPE and H
4ETTC, three kinds of pyridine derivatives (DPE, PEBP-C4 and PEBP-C8) are introduced into their self-assembled structures separately. After diluting the solution of DPE, there is non-transformation of the H
4TCPE structure. This can be attributed to the high hydrogen bond density and the lack of spatial chemical structure. H
4ETTC/DPE can co-assemble into two lamellar structures at different proportion of DPE molecules in the system. At a saturated concentration of DPE, H
4ETTC and DPE self-assemble into a closely packed lamellar structure (
Fig. 5e). By increasing the content of DPE twice, a loosely packed lamellar structure is constructed (
Fig. 5g). DPE molecules assemble into dimers and O-H···O interactions between H
4ETTC molecules are completely broken. DFT results that with the addition of different contents of DPE, the loosely packed structure of H4ETTC/DPE is much more stable than the closely packed structure. With the introduction of PEBP-C4 solution, only a few H
4TCPE and PEBP-C4 can co-assemble (
Fig. 5i, marked by red rectangles), The H
4TCPE molecules are arranged in a row and distributed between the PEBP-C4 molecules. H
4ETTC/PEBP-C4 assembled structures are shown in
Fig. 5k. In the well-ordered lamellar acid-pyridine-acid-pyridine structures, PEBP-C4 molecules interact with the HA solution molecules through O-H···N hydrogen bonds, and these HA molecules are linked to the H
4ETTC molecule through the O-H···O interaction. Similar to the H
4TCPE assembly to PEBP-C4, only a few co-assembled structures (
Fig. 5m, labeled by red rectangles) are co-adsorbed after introducing PEBP-C8. In H
4TCPE/PEBP-C8 system, all of the phenyl groups of H
4TCPE remain perpendicular to the substrate, two of which are linked to the HA and PEBP-C8 molecules by O-H···O and O-H···N hydrogen bonds, respectively. The H
4ETTC network structure is converted to two types of acids-pyridine-acid-pyridine structures by introducing PEBP-C8 solution. These two types of structures are classified by the orientations of PEBP-C8 molecules (
Fig. 5o structures '1' and '2'). Since the self-assembly of symmetric TPE molecules could be regulated by pyridine derivatives, spatial symmetry of molecules subserves the fabrication of controllable functional structures well [
95].