Interfaces liquid/HOPG

The solutions were prepared in 1-octanol or 1-phenyloctane and a drop was placed on a freshly cleaved HOPG surface. A ML of tran5-bis-cyanoethylthio-bis-octadecylthio-TTF in 1-octanol spontaneously physisorbs at the liquid/HOPG interface as revealed by scanning tunnelling microscopy (Fig. 4.13(a, c)). 

Depending on the interdigitation directions of the alkoxy chains, supramolecular chirality of a porous structure is generated on surfaces. Based on the interdigitation pattern we tentatively call (+)-type at the dimer level, a chiral Cg-symmetric hex-amer in which the inner alkyl chains run in a counterclockwise direction is formed. (See Figure 6.3 in Section 6.5.2.) Conversely, (-)-type interdigitation results in a Cg-hexamer of clockwise chirality. Experimentally, the domains of chiral networks co-exist in equal numbers for the achiral DBA-OCn molecules. However, by simple modification of the alkoxy chain, we were able to create homochiral porous networks at the liquid-HOPG interface."... 

Fig. 20 a Structure of a cyclic a-conjugated oligothiophene macrocycle 38 at the liquid-HOPG interface, b STM image (15 x 12 nm ) of the ordering and 2D crystal of 38 adsorbed on graphite, c Calculated minimimi-energy conformation of an individual macrocycle. (Reproduced with permission from Ref. [112])... 

Scheme 7.4 Schematic representation for molecular recognition by [12](2.2.2)DBAs 2am-ao at the liquid/HOPG interface.

A popular substrate for solid-liquid interface studies is hopg. Cleaving the crystal perpendicular to the c-axis leads to the well-defined honeycomb-structured basal plane (Fig. 3). 

The use of HOPG substrates permits the formation of superstructures of alkylated thiophenes at the liquid-graphite interface by self-assembly, due to the absence of strong covalent interactions between the molecules and the substrate [33]. The choice of the relatively inert HOPG substrate is also beneficial because coniamination from the ambient atmosphere is limited and to investigate the correlation between the 2D and 3D structures of the molecules. 

Early STM experiments at the solid-liquid interface on a,oi)-dihexylsexithiophene (1) and non-regioselectively as well as regioselectively substituted 2,5-didodecylsexithiophene (2a-b) demonstrated that these molecules physisorb from a 1,2,4-thrichlorobenzene solution onto HOPG to form highly ordered monolayers [34], in which the alkyl chains and the molecular backbone orient parallel to the graphite surface. 

HOPG. (c) STM image of a 1 10 mixture of HBC-AQ and DMA at the liquid-solid interface, (d) I-V curves measured through the HBC cores before (open triangles) and after (solid circles) the formation of AQ-DMA charge-transfer complexes. Inset shifted and normalized data (see text), (e) A schematic of the resultant prototype CFET. (Reproduced with permission from Ref. 60. American Physical Society, 2004.)... 

Strong van der Waals interactions bettveen the HOPG substrate and graphitic discs as well as alkyl chains induce ordered monolayer or bilayers at the solid/liquid interface. 

Other electronic components can be attached onto the HBC core and the self-assembled side-by-side monolayers provide opportunities to fabricate single molecular devices at the solid/liquid interface. The covalently tethered HBC and pyrene units co-assemble to form stable nano-phase-separated arrays [96]. A significantly different packing of the adlayer of the HBC-pyrene dyad 87 on the basal plane of the HOPG surface has been obtained, as shown in Fig. 3.26. This STM current... 

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