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November 2008 - present
November 2003 - present
Publications
Publications (128)
Nanoporous supramolecular networks physisorbed on solid surfaces have been extensively used to immobilize a variety of guest molecules. Host-guest chemistry in such two-dimensional (2D) porous networks is a rapidly expanding field due to potential applications in separation technology, catalysis and nanoscale patterning. Diverse structural topologi...
A dominant theme within the research on two-dimensional chirality is the sergeant–soldiers principle, wherein a small fraction of chiral molecules (sergeants) is used to skew the handedness of achiral molecules (soldiers) to generate a homochiral surface. Here, we have combined the sergeant–soldiers principle with temperature-dependent molecular se...
Dynamically switchable supramolecular systems offer exciting possibilities in building smart surfaces, the structure and thus the function of which can be controlled by using external stimuli. Here we demonstrate an elegant approach where the guest binding ability of a supramolecular surface can be controlled by inducing structural transitions in i...
The ‘graphene rush’ that started almost a decade ago is far from over. The dazzling properties of graphene have long warranted a number of applications in various domains of science and technology. Harnessing the exceptional properties of graphene for practical applications however has proved to be a massive task. Apart from the challenges associat...
Two-dimensional (2D) crystallization on solid surfaces is governed by a subtle balance of supramolecular and interfacial interactions. However, these subtle interactions often make the prediction of supramolecular structure from the molecular structure impossible. As a consequence, surface-based 2D crystallization has often been studied on a case-b...
The on-surface synthesis of two-dimensional (2D) polymers from monomers represents a useful strategy for designing lattice, orbital and spin symmetries. Like other 2D materials, the ordered stacking of 2D polymers into bilayers may allow developing unique optoelectronic, charge transport and magnetic properties not found in the individual layers. H...
Single layered metal–organic coordination networks (MOCNs) are gaining attention thanks to their unique electronic and magnetic properties. The presence of coordinatively unsaturated metal sites within their structures provides additional binding locations for substrates in catalytic processes. Consequently, MOCNs fabricated on solid surfaces are e...
Gentle annealing and photopolymerization under inert atmospheres strongly enhance the quality of polydiacetylene monolayers. These simple measures not only triple the average polymerization degree, but also alter the preferred photoexcitation...
(Micro)spectroscopy often generates various output signals due to intrinsic inhomogeneity of material arrangement at low dimensions or machinery drift, albeit the bulk composition and experimental parameters remain constant. In fact, such diversity can be harnessed to measure material’s purity, unveiling various concealed features via statistical i...
Chemical patterning of 2D materials is relevant in several different domains of science and technology with exciting possibilities in electronics, catalysis, sensing, and photonics. Despite intense efforts, spatially controlled, (multifunctional) covalent chemical patterning of graphene and related 2D materials is not straightforward. In my talk, I...
Strong and oriented electric fields are known to influence structure as well as reactivity. The strong electric field (EF) between the tip of a scanning tunneling microscope (STM) and graphite has been used to modulate two-dimensional (2D) polymerization of aryl boronic acids where switching the polarity of the substrate bias enabled reversible tra...
The development and integration of cyclophanes into future functional materials require a detailed understanding of the physicochemical principles that underlie their properties, phase behavior, and in particular the relationship between structure and function. Here, electrochemically switchable crystallization of a ferrocene‐bearing 3D Janus tecto...
The reduction of carbon dioxide (CO2) using porphyrin‐containing 2D covalent organic frameworks (2D‐COFs) catalysts is widely explored nowadays. While these framework materials are normally fabricated as powders followed by their uncontrolled surface heterogenization or directly grown as thin films (thickness >200 nm), very little is known about th...
Immobilization of stimulus‐responsive systems on solid surfaces is beneficial for controlled signal transmission and adaptive behavior while allowing the characterization of the functional interface with high sensitivity and high spatial resolution. Positioning of the stimuli‐responsive units with nanometer‐scale precision across the adaptive surfa...
Here, we report on the synthesis of discrete oligomers of alkyl‐bridged naphthalenediimides (NDIs) and study their molecular nanostructures both in bulk, in solution, and at the liquid‐solid interface. Via an iterative synthesis method, multiple NDI cores were bridged with short and saturated alkyl‐diamines (C3 and C12) or long and unsaturated alky...
In recent years, there has been significant focus on investigating and controlling chiral self‐assembly, specifically in the context of enantiomeric separation. This study explores the self‐assembly behavior of 4‐dodecyl‐3,6‐di(2‐pyridyl)pyridazine (DPP−C12) at the interface between heptanoic acid (HA) and highly oriented pyrolytic graphite (HOPG)...
We report on the fast reaction kinetics of an imine based 2D polymer (2DP) formed from a single monomer carrying both aldehyde and amine groups. Our results point towards a direct monomer-to-crystalline polymer transition without an amorphous intermediate.
Chemical patterning surfaces is relevant in several different domains of science and technology with exciting possibilities in electronics, catalysis, sensing, and photonics. Here, we present a novel strategy for chemical patterning of graphite using a combination of covalent and non-covalent approaches. Building on our previous work, where self-as...
Invited for the cover of this issue is the group of Manuel Souto and co‐workers at the University of Aveiro and CICECO‐Aveiro Institute of Materials. The image depicts the direct C−H arylation of dithiophene‐tetrathiafulvalene (DT‐TTF) and the self‐assembly of DT‐TTF‐tetrabenzoic acid studied by using scanning tunnelling microscopy. Read the full t...
Tetrathiafulvalene is among the best known building blocks in molecular electronics due to its outstanding electron‐donating and redox properties. Among its derivatives, dithiophene‐tetrathiafulvalene (DT‐TTF) has attracted considerable interest in organic electronics, owing to its high field‐effect mobility. Herein, we report the direct C−H arylat...
Two wide‐band gap U‐shaped polycyclic aromatic hydrocarbons with/without boron and nitrogen (BN‐) doping (BN‐1 and C‐1) were synthesized to tune the electronic features to suit the performance requirements for organic field‐effect transistor memory (OFET‐NVM). The chemical structures were characterized by scanning tunneling microscopy and single‐cr...
The covalent functionalization of carbon surfaces with nanometer-scale precision is of interest because of its potential in a range of applications. We herein report the controlled grafting of graphite surfaces using electrochemically generated aryl radicals templated by self-assembled molecular networks (SAMNs) of bisalkylurea derivatives. A bisal...
Two wide-bandgap U-shaped polycyclic aromatic hydrocarbons with/without boron and nitrogen (BN-) doping (BN-1 and C-1) were synthesized to tune the electronic features to suit the performance requirements for organic field-effect transistor memory (OFET-NVM). The chemical structures were characterized by scanning tunneling microscopy and single-cry...
A series of zigzag‐edged polycyclic aromatic hydrocarbons (PAHs) (Z1‐Z3) were synthesized from 2,12‐dibromo‐7,14‐diphenyl‐benzo[m]tetraphene (9) as a versatile building block. Their structures were unambiguously confirmed by laser desorption/ionization time‐of‐flight mass spectrometry, ¹H NMR, Raman, and Fourier‐transformed infrared (FTIR) spectros...
Self-assembled molecular networks (SAMNs) are formed by the spontaneous assembly of molecules on surfaces. On conductive atomically flat surfaces, and also at the liquid-solid interface, scanning tunneling microscopy (STM) can follow their growth dynamics. Desorption and adsorption dynamics are difficult to probe through the liquid-solid interface....
Grain boundaries in polycrystals have a prominent impact on the properties of a material, therefore stimulating the research on grain boundary engineering. Structure determination of grain boundaries of molecule‐based polycrystals with submolecular resolution remains elusive. Reducing the complexity to monolayers has the potential to simplify grain...
Two-dimensional (2D) chirality has been actively studied in view of numerous applications of chiral surfaces such as in chiral resolutions and enantioselective catalysis. Here, we report on the expression and amplification of chirality in hybrid 2D metallosupramolecular networks formed by a nucleobase derivative. Self-assembly of a guanine derivati...
Tetrathiafulvalene is among the most well-known building block in molecular electronics due to its outstanding electron-donating and redox properties. Among its derivatives, dithiophene-tetrathiafulvalene (DT-TTF) received a lot of interest for organic electronics due to its high charge mobility. Herein we report the direct C-H arylation of DT-TTF...
Graphene, a single layer of carbon atoms in a two-dimensional (2D) hexagonal lattice, showcases key properties suitable for electrode materials such as high specific surface area, good electrical and thermal conductivities. ¹ Ionic liquids (ILs) are a class of molten salts that are entirely composed of ions. These liquids possess exceptional proper...
This chapter provides a survey of the progress made in the construction of complex multicomponent supramolecular architectures on solid surfaces. The discussion is focussed on the self-assembly of organic building blocks physisorbed on solid surfaces such as graphite and gold and characterised using scanning tunnelling microscopy (STM). The fundame...
Nanoscopic lateral confinement created on a graphite surface enabled the study of embryonic stages of molecular self-assembly on solid surfaces using scanning tunneling microscopy performed at the solution/solid interface.
The production of graphene with controlled properties and structure is one of the most challenging aspects for a chemist. Covalent functionalization is one of the common approaches to obtain well-defined and robust modification of carbon materials. Different protocols have been proposed for carrying out this functionalization step. However, aryl di...
The fabrication of highly ordered nanostructured surfaces is desirable in supramolecular chemistry and envisaged to bolster advances in heterogeneous catalysis and microelectronic applications. Here, we report on a novel set of alkylated double N,N′-bis(n-alkyl)-naphthalenediimides (NDIs) for the functionalization of highly oriented pyrolytic graph...
Self-assembled molecular networks (SAMNs) on surfaces evoke a lot of interest, both from a fundamental as well as application point of view. When formed at the liquid-solid interface, precise control over different polymorphs can be achieved by simply adjusting the concentration of molecular building blocks in solution. Significant influence of sol...
Graphene nanoribbons (GNRs), quasi-one-dimensional strips of graphene, exhibit a nonzero bandgap due to quantum confinement and edge effects. In the past decade, different types of GNRs with atomically precise structures have been synthesized by a bottom-up approach and have attracted attention as a novel class of semiconducting materials for appli...
The presence of an opportune impurity can change the on-surface assembly behavior via preferential adsorption and nucleation.
Hydrogen bonding is an indispensable tenet in the fabrication of surface-confined physisorbed supramolecular networks. On-surface supramolecular chemistry is dominated by aromatic carboxylic acids, which allow implementation of highly directional and robust design elements in the form of hydrogen bonds. In this article, we investigate the influence...
The chemistry of carbon surfaces has regained traction in recent years in view of its applicability towards covalent modification of a variety of (2D) materials. A general requisite is the formation of a dense and well-defined monolayer of aryl groups covalently bound to the surface. Given the use of reactive chemistries however, it is often not ea...
Structural polymorphism is ubiquitous in physisorbed self-assembled monolayers formed at the solution–solid interface. One of the ways to influence network formation at this interface is to physically decouple the self-assembled monolayer from the underlying substrate thereby removing the influence of the substrate lattice, if any. Here we show a s...
Reported here is a molecular dipole that self‐assembles into highly ordered patterns at the liquid‐solid interface, and it can be switched at room temperature between a bright and a dark state at the single‐molecule level. Using a scanning tunneling microscope (STM) under suitable bias conditions, binary information can be written at a density of u...
Covalent functionalization of graphene is highly sought after, not only in view of the potential applications of the chemically modified material, but also because it brings fundamental insight into the chemistry of graphene. Thus, strategies that yield chemically modified graphene with densely grafted films of aryl groups via simple experimental p...
Molecular flip‐flop: By pulsing the tip voltage in a scanning tunneling microscope, individual molecules in a monolayer of a polyaromatic salt can be switched reversibly from a bright (0) to a dark (1) state, at room temperature and outside of a vacuum. The information density of this single‐molecule binary memory can reach up to 41 terabits per cm...
The self-assembly of an asymmetric perylene diimide (PDI) with a dove-tailed side chain is investigated after thermal annealing at various temperatures in solid-state. After annealing at low temperatures PDI dimers are formed through hydrogen bonding between the imide and carbonyl groups, together with π–stacking interactions leading to a helical p...
Halogen bonds, which provide an intermolecular interaction with moderate strength and high directionality, have emerged as a promising tool in the repertoire of non‐covalent interactions. In this review, we provide a survey of the literature where halogen bonding was used for the fabrication of supramolecular networks on solid surfaces. The definit...
Synthetic two-dimensional polymers (2DPs) obtained from well-defined monomers via bottom-up fabrication strategies are promising materials that can extend the realm of inorganic 2D materials. The on-surface synthesis of such 2DPs is particularly popular, however the pathway complexity in the growth of such films formed on solid surfaces is poorly u...
Atomically thin sheets of materials, the so-called two-dimensional (2D) materials arrived on the scene in early 2000s with the successful isolation of graphene as freestanding monolayer films. Graphene, a single atom thick sheet of sp ² -hybridized carbon bonded in a honeycomb lattice, has exceptional electronic, optical, mechanical and thermal pro...
Graphene-based two-dimensional (2D) materials are promising candidates for a number of different energy applications. A particularly interesting one is in next generation supercapacitors, where graphene is being explored as an electrode material in combination with room temperature ionic liquids (ILs) as electrolytes. Because the amount of energy t...
Halogen bonding has emerged as a promising tool in two-dimensional (2D) crystal engineering. Since halogen bonds are similar to hydrogen bonds in a number of aspects, the existing knowledge of hydrogen bonded systems can be applied to halogenated systems. Here we evaluate the applicability of a retrosynthetic approach based on topological similarit...
Two unprecedented porphyrin fused nanographene molecules 1 and 2 have been synthesized by Scholl reaction of tailor‐made precursors based on benzo[m]tetraphene‐substituted porphyrins. The chemical structures were validated by a combination of high‐resolution matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (HR MALDI‐TOF...
Two unprecedented porphyrin fused nanographene molecules 1 and 2 have been synthesized by Scholl reaction of tailor‐made precursors based on benzo[m]tetraphene‐substituted porphyrins. The chemical structures were validated by a combination of high‐resolution matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (HR MALDI‐TOF...
Strong electric fields are known to influence the properties of molecules as well as materials. Here we show that by changing the orientation of an externally applied electric field, one can locally control the mixing behavior of two molecules physisorbed on a solid surface. Whether the starting two-component network evolves into an ordered two-dim...
The performance of organic nanostructures is closely related to the organization of the functional molecules. Frequently, molecular chirality plays a central role in the way molecules assemble at the supramolecular level. Herein we report the hierarchical self-assembly of benzo-fused tetrathia[7]helicenes on solid surfaces, from a single surface-bo...
Ionic self-assembly of charged molecular building blocks relies on the interplay between long-range electrostatic forces and short-range, often cooperative, supramolecular interactions, yet has been seldom studied in two dimensions at the solid–liquid interface. Here, we demonstrate anion-driven switching of two-dimensional (2D) crystal structure a...
The application of supramolecular chemistry on solid surfaces represents an exciting field of research that continues to develop in new and unexpected directions. This review highlights recent advances in the field which range from the fundamental aspects of the thermodynamics of self-assembly through to the development of new materials with potent...
Recent advances in bottom-up synthesis of atomically defined graphene nanoribbons (GNRs) with various microstructures and properties have demonstrated their promise in electronic and optoelectronic devices. Here we synthesize N = 9 armchair graphene nanoribbons (9-AGNRs) with a low optical bandgap of ~1.0 eV and extended absorption into the infrare...
We report on the design and fabrication of a four-component supramolecular network using the 'core-shell' approach. Each 'core' component templates the formation of an outer 'shell' leading to formation of three concentric 'shells' around the central guest. The 'shells' are formed only in presence of guests thus demonstrating remarkable selectivity...
One current key challenge in graphene research is to tune its charge carrier concentration, i.e., p- and n-type doping of graphene. An attractive approach in this respect is offered by controlled doping via well-ordered self-assembled networks physisorbed on the graphene surface. We report on tunable n-type doping of graphene using self-assembled n...
The degree of order of poly(3-alkylthiophene)s on atomically flat surfaces is strongly influenced by interchain interactions. Regularly ordered, disordered and amorphous microstructures are observed for achiral, homochiral and meso poly(3-alkylthiophene)s, respectively, as revealed by scanning tunneling microscopy.
Two-dimensional supramolecular chirality is often achieved by confining molecules against a solid surface. The sergeants-soldiers principle is a popular strategy to fabricate chiral surfaces using predominantly achiral molecules. In this method, achiral molecules (the soldiers) are forced to assemble in a chiral fashion by mixing them with a small...
A multistep synthesis of hexa-peri-hexabenzocoronene (HBC) with four additional K-regions was developed through a precursor based on two benzotetraphene units bridged with p-phenylene, featuring pre-installed zigzag moieties. Characterization by laser desorption/ionization time-of-flight mass spectrometry, Raman and IR spectroscopy, and scanning tu...
Molecular self-assembly at the solid–liquid interface is highly developed, yet still faces several challenges, in particular related to reaching into the third dimension. Here, we demonstrate the spontaneous and reversible transition between two- and three-dimensional self-assembly of a charged polyaromatic molecule at the solid–liquid interface un...
A series of novel toroidal cyclo-2,9-tris-1,10-phenanthroline macrocycles with an unusual hexaaza cavity are reported. Nickel-mediated Yamamoto aryl-aryl coupling was found to be a versatile tool for the cyclotrimerization of functionalized 1,10-phenathroline precursors. Due to the now improved processability, both liquid-crystalline behavior in th...
Formation of multiple polymorphs during two-dimensional (2D) crystallization of organic molecules is more of a routine occurrence than rarity. Although such diverse crystalline structures provide exciting possibilities for studying crystal engineering in 2D, predicting the occurrence of polymorphs for a given building block is often non-trivial. Mo...
Multicomponent network formation by using a shape-persistent macrocycle (MC6) at the interface between an organic liquid and Au(111) surface is demonstrated. MC6 serves as a versatile building block that can be coadsorbed with a variety of organic molecules based on different types of noncovalent interactions at the liquid–solid interface. Scanning...
Structurally defined, long (>100 nm), and low-band-gap (∼1.2 eV) graphene nanoribbons (GNRs) were synthesized through a bottom-up approach, enabling GNRs with a broad absorption spanning into the near-infrared (NIR) region. The chemical identity of GNRs was validated by IR, Raman, solid-state NMR, and UV-vis-NIR absorption spectroscopy. Atomic forc...
We demonstrate the spontaneous and reversible transition between the two- and three-dimensional self-assembly of a supramolecular system at the solid–liquid interface under electrochemical conditions, using in situ scanning tunneling microscopy. By tuning the interfacial potential, we can selectively organize our target molecules in an open porous...
Wir zeigen mithilfe der Rastertunnelmikroskopie den spontanen und reversiblen Übergang zwischen zwei- und dreidimensionaler Selbstorganisation eines supramolekularen Systems an der Grenzflche zwischen Flüssigkeit und Metalloberflche unter elektrochemischer Kontrolle. Durch Abstimmen des Grenzflchenpotentials können wir unsere Zielmoleküle selektiv...
Using in situ electrochemical scanning tunnelling microscopy (EC-STM), we demonstrate fully reversible tuning of molecular tiling between self-assembled structures with supramolecular motifs containing 2, 3, 4, 6 or 7 tectons. The structures can be explained by electrocompression of the cationic adlayer at the solid-liquid interface.
Controlling crystal polymorphism constitutes a formidable challenge in contemporary chemistry. Two-dimensional (2D) crystals often provide model systems to decipher the complications in 3D crystals. In this contribution, we explore a unique way of governing 2D polymorphism at the organic liquid-solid interface. We demonstrate that a directional sol...
Nanostructured molecular thin films adsorbed on solid surfaces form the basis of numerous applications. Long-range order within adsorbed molecules is very often a desirable property for such systems. In this contribution, we report a simple and efficient method to fabricate well-aligned thin films of organic molecules over a few millimeter squares....
The properties of graphene nanoribbons (GNRs) make them good candidates for next-generation electronic materials. Whereas 'top-down' methods, such as the lithographical patterning of graphene and the unzipping of carbon nanotubes, give mixtures of different GNRs, structurally well-defined GNRs can be made using a 'bottom-up' organic synthesis appro...
Functionalization and modification of graphene at the nanometer scale is desirable for many applications. Supramolecular assembly offers an attractive approach in this regard, as many organic molecules form well-defined patterns on surfaces such as graphite via physisorption. Here we show that ordered porous supramolecular networks with different p...
Ligand-protected gold nanoparticles exhibit large local curvatures, features rapidly varying over small scales, and chemical heterogeneity. Their imaging by Scanning Tunneling Microscopy (STM) can, in principle, provide direct information on the architecture of their ligand shell, yet STM images require laborious analysis and are challenging to be...
Self-assembled physisorbed monolayers consist of regular two-dimensional arrays of molecules. Two-dimensional self-assembly of organic and metal-organic building blocks is a widely used strategy for nanoscale functionalization of surfaces. These supramolecular nanostructures are typically sustained by weak non-covalent forces such as van der Waals,...
Ligand-protected gold nanoparticles exhibit large local curvatures, features rapidly varying over small scales, and chemical heterogeneity. Their imaging by Scanning Tunneling Microscopy (STM) can, in principle, provide direct information on the architecture of their ligand shell, yet STM images require laborious analysis and are challenging to be...
In this work, we provide evidence for multiple non-planar adsorption geometries of a novel pyrenocyanine derivative at the liquid-solid interface under ambient conditions. When adsorbed at the organic liquid-solid interface, lead pyrenocyanine forms well-ordered monolayers that exhibit peculiar non-periodic contrast variation. The different contras...
Gold nanoparticles protected by a binary mixture of thiolate molecules have a ligand shell that can spontaneously separate into nanoscale domains. Complex morphologies arise in such ligand shells, including striped, patchy, and Janus domains. Characterization of these morphologies remains a challenge. Scanning tunneling microscopy (STM) imaging has...
Longest planar rylene dyes hexarylene diimide (HDI) and octarylene diimide (ODI), with extended conjugated cores (2.8 and 3.7 nm in length) have been prepared by a facile syntheses. Both HDI and ODI exhibit broad and intense NIR absorption. Scanning tunneling microscopy (STM) study reveals that HDI forms ordered herringbone bilayer or multilayers w...
Long and planar: Facile syntheses of soluble hexarylene diimides (HDI) and octarylene diimides (ODI) are described. They are stable in both solution and the solid state, and exhibit broad and intense NIR absorption. Scanning tunneling microscopy (STM) reveals that HDI, after deposition from solution, forms a unique herringbone bilayer or stable mul...
We report the synthesis, characterization, and self-assembly of a new gemini-type amphiphilic hexathienocoronene (HTCGemini), which owes its amphiphilicity to two hydrophobic dodecyl chains on one side of the HTC core and two hydrophilic triethylene glycol (TEG) chains on the other. Bearing a “softer” aromatic HTC core than the conventional hexa-pe...
