Implementing Functionality in Molecular Self-Assembled Monolayers

Abstract

The planar heterocyclic molecules 1,6,7,12-tetraazaperylene on a Ag(111) metal substrate show different charging characteristics depending on their local environment: next to vacancies in self-assembled islands, molecules can be charged by local electric fields, whereas their charge state is fixed otherwise. This enables the activation of selected molecules inside islands by vacancy creation from scanning-probe-based manipulation. This concept allows for combining the precise mutual atomic-scale alignment of molecules by self-assembly, on one hand, and the implementation of specific functionality into otherwise homogeneous monolayers, on the other. Activated molecules in the direct neighborhood influence each other in their charging characteristics, suggesting their use as molecular quantum cellular automata. Surprisingly, only very few interacting molecules exhibit a rich spectroscopic signature, which offers the prospect of implementing complex functionality in such structures in the future.

Synthesis and Local Probe Gating of a Monolayer Metal‐Organic Framework

“…As shown in Figures 4d–j, the elliptical rings observed in the LDOS maps at different bias voltages represent the onset of charging as the tip is moved toward the charging site. Notably, in the previous experiments, both the charging peaks [ 39–41,46,49 ] and dips [ 42,47,48 ] have been found at negative bias. The presence of a peak or dip in the d I /d V spectrum depends on whether the LDOS at the tip position increases or decreases due to the charging event, which might also depend on the local adsorption registry between the MOF and the underlying graphene substrate.…”

“…Interestingly, the STS measured on the center of the DCA molecule (black curve in Figure 2b) shows two sharp dips around −0.6 and −1.2 V; the STS on top of the Cu atom (green curve in Figure 2b) shows a small dip around −0.6 V and a sharp peak around −1.2 V; the end of the long axis of the DCA molecule (blue curve in Figure 2b) shows a sharp peak around −0.6 V and a tiny dip around −1.2 V. The peaks/dips at these two bias values are attributed to the typical charging features, where the charge state of the molecule under the tip changes due to the tip-induced local electric field. [38][39][40][41][42][43][44][45][46][47][48][49][50] We will discuss the details of these charging features in Figure 4. The spectra of the MOF on the step edge of the underlying Ir(111) substrate (Figure S12, Supporting Information) is consistent with the one on the flat area (Figure 2), indicating that the electronic properties of the MOF are effectively decoupled from the metal substrate by the graphene layer.…”

“…Charging behavior has been studied in detail in the case of single molecules or self-assembled molecular monolayers on coinage metal surfaces such as Au(111) [42] and Ag(111) [47,48] and more frequently found when the molecule is decoupled from the substrate by an ultra-thin film such as Al 2 O 3 , [38][39][40][41] graphene [46,49] and hexagonal boron nitride. [43][44][45]50] It can be explained by considering the tip-molecule-substrate system as a doublebarrier tunnel junction (DBTJ) as illustrated in Figure 4a,b.…”

Autonomous robotic nanofabrication with reinforcement learning

“…This task is an example of a subtractive manufacturing process that starts from a self-assembled molecular structure. We note that subtractive manufacturing has been identified as key to nanoscale fabrication (21,22).…”

Pyrazinacenes exhibit on-surface oxidation-state-dependent conformational and self-assembly behaviours

“…for synthetic and materials chemistry [1][2][3] and for the ability to modulate oxidation states and organic/inorganic dye structures among many other properties. An increasingly important challenge is to control site-specific redox functionality and physicochemical properties of molecules within supramolecular architectures 4,5 , especially at surfaces and interfaces [6][7][8][9][10] where access to such functionality and the corresponding applications would be facilitated even at the molecule level 11,12 . Biochemical systems have evolved towards exceptional levels of control over the supramolecular and metal coordination mechanisms governing chemical reactions 13 .…”