Spatially Controlled Noncovalent Functionalization of 2D Materials Based on Molecular Architecture

Abstract

Polymerizable amphiphiles can be assembled into lying-down phases on 2D materials such as graphite and graphene to create chemically orthogonal surface patterns at 5-10 nm scales, locally modulating functionality of the 2D basal plane. Functionalization can be carried out through Langmuir-Schaefer conversion, in which a subset of molecules is transferred out of a standing phase film on water onto the 2D substrate. Here, we leverage differences in molecular structure to spatially control transfer at both nanoscopic and microscopic scales. We compare transfer properties of five different single- and dual-chain amphiphiles, demonstrating that those with strong lateral interactions (e.g., hydrogen-bonding networks) exhibit the lowest transfer efficiencies. Since molecular structures also influence microscopic domain morphologies in Langmuir films, we show that it is possible to transfer such microscale patterns, taking advantage of variations in the local transfer rates based on the structural heterogeneity in Langmuir films. Nanoscale domain morphologies also vary in ways that are consistent with predicted relative transfer and diffusion rates. These results suggest strategies to tailor noncovalent functionalization of 2D substrates through controlled LS transfer.

Oleylamine Impurities Regulate Temperature-Dependent Hierarchical Assembly of Ultranarrow Gold Nanowires on Biotemplated Interfaces

“…Striped phases of functional alkanes ( e.g. , phospholipids) assemble on materials such as HOPG via drop-casting from organic solvent , or through Langmuir–Schaefer conversion ,, (see Experimental Methods). In striped phases, alkyl chains assemble parallel to the substrate, ,− stabilized by a combination of alkyl−π interactions and lateral interactions between alkyl chains within the layer.…”

“…Striped phospholipid surfaces 40−42 on highly ordered pyrolytic graphite (HOPG, Figure 2) provide a useful templating mechanism for controlling assembly of OLAmcapped AuNWs, 39 of particular relevance to examining thermal impacts of trans and saturated chains in OLAm blends. Striped phases of functional alkanes (e.g., phospholipids) assemble on materials such as HOPG via drop-casting from organic solvent 43,44 or through Langmuir−Schaefer conversion 41,45,46 (see Experimental Methods). In striped phases, alkyl chains assemble parallel to the substrate, 43,47−49 stabilized by a combination of alkyl−π interactions and lateral interactions between alkyl chains within the layer.…”

1-nm-Wide Hydrated Dipole Arrays Regulate AuNW Assembly on Striped Monolayers in Nonpolar Solvent

“…Diynes including 10,12-pentacosadiynoic acid (10,12-PCD-COOH) assemble into lying-down lamellar phases with paired headgroups on highly oriented pyrolytic graphite (HOPG) and graphene, creating 1-nm-wide stripes of headgroups with pitches (typically 5-8 nm) prescribed by alkyl chain length. [26][27][28][29][30][31][32] Photopolymerization of the diyne produces an ene-yne polymer backbone, which has been extensively examined in the context of molecular electronics, 27,28,33 but also stabilizes the monolayer against solvent exchange. 10, [34][35][36][37][38] Recently, we found that in striped monolayers of diyne phospholipids (e.g., 1,2bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphoethanolamine [diyne PE]; Figure 1A), the terminal ammonium functional group protrudes slightly from the surface, forming a ''sitting'' geometry (Figure 1B).…”

Probing functional self-assembled molecular architectures with solution/solid scanning tunnelling microscopy

“…For electronic modification, long, linear molecules may offer a more promising route than small aromatics for solutionprocessed electronic modification layers; they have already been shown to be good candidates for chemical functionalization of 2D materials, 124,125 and descriptions of electronic modifications are emerging. 126 For example, the alkane n-hexatriacontane (HTC, C 36 H 74 ) crystallizes into well-defined films on graphene, and the presence of a HTC film on a graphene filed effect transistor (FET) improved hole mobility from 17 000 cm 2 V À1 s À1 (without HTC) to 38 000 cm 2 V À1 s À1 , an effect attributed to a reduction in charge density inhomogeneity arising from local lifting of the graphene by the HTC film.…”