Steven De Feyter

KU Leuven | ku leuven · Department of Chemistry

The human immunodeficiency virus (HIV) infects non-dividing cells and its genome must be compacted to enter the cell nucleus. Here, we show that the viral enzyme integrase (IN) compacts HIV DNA mimetics in vitro . Under physiological conditions, IN-compacted genomes are consistent in size with those found for pre-integration complexes in infected c...

The human immunodeficiency virus (HIV) infects non-dividing cells and its genome must be compacted to enter the cell nucleus. Here, we show that the viral enzyme integrase (IN) compacts HIV DNA mimetics in vitro . Under physiological conditions, IN-compacted genomes are consistent in size with those found for pre-integration complexes in infected c...

(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...

The understanding of supramolecular chirality in self‐assembled molecular networks (SAMNs) on surfaces generates a lot of interest because of its relation to the production of chiral sensors, reactors, and catalysts. We herein report the adsorption of a prochiral solvent molecule in porous SAMNs formed by a chiral dehydrobenzo[12]annulene (cDBA) de...

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...

Unraveling the structure and dynamics of the formation of covalent and non-covalent organic-based 2D crystalline materials is key to controlling the quality of these materials, such as the defect density and their size. Understanding these characteristics is important for controlling their properties. This contribution highlights our efforts in usi...

Molecular islands of various shapes and sizes composed of a few tens of molecules only are formed at the liquid-solid interface, at room temperature, by an alkoxylated dehydrobenzo[12]annulene (DBA) derivative....

At elevated temperatures, the prototypical organic solvents used to study the self‐assembly of supramolecular monolayers at liquid–solid interfaces alter a graphite substrate by intercalation. As a consequence, less strongly bound supramolecular monolayers become thermodynamically unstable, as probed by scanning tunneling microscopy. Complementary...

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 human immunodeficiency virus (HIV) infects non-dividing cells and its genome must be compacted to enter the cell nucleus. Here, we show that the viral enzyme integrase (IN) compacts HIV DNA mimetics in vitro . Under physiological conditions, IN-compacted genomes are consistent in size with those found for pre-integration complexes in infected c...

In this work we investigate the behaviour of molecules at the nanoscale using scanning tunnelling microscopy in order to explore the origin of the cooperativity in the formation of self-assembled molecular networks (SAMNs) at the liquid/solid interface. By studying concentration dependence of alkoxylated dimethylbenzene, a molecular analogue to 5-a...

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...

The molecular functionalization of MoS2 has attracted a lot of attention due to its potential to afford fine-tuned hybrid materials that benefit from the power of synthetic chemistry and molecular design. Here, we report on the on-surface reaction of maleimides on bulk and molecular beam epitaxy grown single-layer MoS2, both in ambient conditions a...

To control the synthesis of designer catalysts on graphitic materials up to the nanometer scale, methods should be provided that combine both nanoscale characterization and bulk scale experiments. This work...

Self-assembly on surfaces often produces chiral networks, even when starting from achiral building blocks. However, when achiral molecules are used to produce chiral networks, two possible enantiomorphs are created with equal probability, rendering therefore the overall surface achiral. This outcome can be changed by finding a way to promote the pr...

In this work, we investigate the temperature effect on the formation of self-assembled molecular networks (SAMNs) at the liquid/solid interface, focusing on an alkylated achiral glycine derivative at the 1-phenyloctane/HOPG interface. Using STM with an in situ heating stage, we comprehensively examine the concentration-temperature phase space for 2...

After the isolation of graphene monolayer graphene 2D materials have garnered great attention for their theoretically predicted exceptional properties. Covalent functionalization strategies are used to further finetune and improve these properties, which allow to integrate these materials into a wide range of applications. However, these strategies...

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...

Coke formation is the prime cause of catalyst deactivation, where undesired carbon wastes block the catalyst surface and hinder further reaction in a broad gamut of industrial chemical processes. Yet, the origins of coke formation and their distribution across the catalyst remain elusive, obstructing the design of coke‐resistant catalysts. Here, we...

We herein report the construction of homochiral, hierarchical self-assembled molecular networks (SAMNs) at the liquid/graphite interface using a single molecular building block, a chiral dehydrobenzo[12]annulene (cDBA) derivative with three chiral alkoxy and three hydroxy groups positioned in an alternating manner on the DBA core. The cDBA molecule...

MXenes are electrically conductive 2D transition metal carbides/nitrides obtained by the etching of nanolaminated MAX phase compounds, followed by exfoliation to single‐ or few‐layered nanosheets. The mainstream chemical etching processes have evolved from pure hydrofluoric acid (HF) etching into the innovative “minimally intensive layer delaminati...

Boosted by the emerging need for highly integrated gas sensors in the internet of things (IoT) ecosystems, electronic noses (e‐noses) are gaining interest for the detection of specific molecules over a background of interfering gases. The sensing of nitrogen dioxide is particularly relevant for applications in environmental monitoring and precision...

Graphene nanoribbons (GNRs), a quasi‐one‐dimensional form of graphene, have gained tremendous attention due to their potential for next‐generation nanoelectronic devices. The chemical unzipping of carbon nanotubes is one of the attractive fabrication methods to obtain single‐layered GNRs (sGNRs) with simple and large‐scale production. The authors r...

Multilayered growth is often observed upon electrografting aryl diazonium derivatives on graphitic substrates due to the reactive nature of aryl radicals. The mechanism of the multilayer formation has been investigated either by measuring the thickness of the grafted layer, the charge transfer, or via simulations. Spectroscopy and in particular mic...

Precise synthesis of graphene nanoribbons (GNRs) is of great interest to chemists and materials scientists because of their unique opto-electronic properties and potential applications in carbon-based nanoelectronics and spintronics. In addition to the tunable edge structure and width, introducing curvature in GNRs is a powerful structural feature...

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.

Synergically combining their respective ultrahigh charge mobility and strong light absorption, graphene (Gr)/semiconductor heterostructures are promising building blocks for efficient optoelectronics, particularly photodetectors. Charge transfer (CT) across the heterostructure interface crucially determines device efficiency and functionality. Here...

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...

The black perovskite phase of CsPbI3 is promising for optoelectronic applications; however, it is unstable under ambient conditions, transforming within minutes into an optically inactive yellow phase, a fact that has so far prevented its widespread adoption. Here we use coarse photolithography to embed a PbI2-based interfacial microstructure into...

Ultralow energy (ULE) ion implantation is being increasingly applied to the modification of 2D materials, in particular, for substitutional doping and intercalation of graphene. Implantation-induced defects, whether desired or not, have a strong impact on the properties of graphene. Significant research has been devoted to vacancy-related defects h...

Control over the functionalization of graphenic materials is key to enable their full application in electronic and optical technologies. Covalent functionalization strategies have been proposed as an approach to tailor the interfaces’ structure and properties. However, to date, none of the proposed methods allow for a covalent functionalization wi...

Herein we report the impact of covalent modification (grafting), inducing lateral nanoconfinement conditions, on the self-assembly of a quinonoid zwitterion derivative into self-assembled molecular networks at the liquid/solid interface. At low concentrations where the compound does not show self-assembly behaviour on bare highly oriented pyrolytic...

The adsorption and self-assembly of several thiacarbocyanine dyes on hexagonal boron nitride (hBN) was investigated by combining steady-state spectroscopy and atomic force microscopy. The adsorption isotherms indicate that at saturation the density of the cationic TDC (5,5-dichloro-3-3′-diethyl-9-ethyl-thiacarbocyanine) molecules on hBN is similar...

We herein present the periodic covalent functionalization of graphite surfaces, creating a range of patterns of different symmetries and pitches at the nanoscale. Self-assembled molecular networks (SAMNs) of rhombic-shaped bis(dehydrobenzo[12]annulene) (bisDBA) derivatives having alkyl chain substituents of different lengths were used as templates...

Adsorptive separation is a promising lower-energy alternative for traditional industrial separation processes. While carbon-based materials have a long history in adsorptive removal of organic contaminants from solution or gas mixtures, separation using an adsorption/desorption protocol is rarely considered. The main drawbacks are the limited contr...

In the first part, we will focus on the principles of self-assembled molecular network formation at the liquid-solid interface on surfaces such as graphite, MoS 2 , and graphene. Then we will discuss how lateral confinement, induced by covalent functionalization of graphite and graphene, affects self-assembly. Several strategies will be demonstrate...

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...

A green multicomponent synthesis of previously unreported octahydropyrimido[4,5-g]quinazoline-5,6-diones was developed from simple building blocks. These highly symmetrical compounds show strong propensity to self-assembled molecular network (SAMN) formation on highly oriented...

Patterned covalent functionalization of graphitic surfaces (GSs) is of interest in the development of devices and nanocomposite materials. In contrast to the strategies using external templates or control for realizing patterned covalent functionalization of GSs, here, we present a self‐templated strategy by exploiting the synergistic effects of ch...

We show that particle roughness leads to changes in the number, shape and resulting capillary force of liquid bridges in capillary suspensions. We created fluorescently labeled, raspberry-like particles with varying roughness by electrostatically adsorbing silica nanoparticles with sizes between 40 nm and 250 nm on silica microparticles. Rougher pa...

Covalent functionalization of graphene (CFG) has shown attractive advantages in tuning the electronic, mechanical, optical, and thermal properties of graphene. However, facile, large‐scale, controllable, and highly efficient CFG remains challenging and often involves highly reactive and volatile compounds, requiring complex control of the reaction...

The quality of crystalline two-dimensional (2D) polymers1–6 is intimately related to the elusive polymerization and crystallization processes. Understanding the mechanism of such processes at the (sub)molecular level is crucial to improve predictive synthesis and to tailor material properties for applications in catalysis7–10 and (opto)electronics1...

We show that particle roughness leads to changes in the number, shape and resulting capillary force of liquid bridges in capillary suspensions. We created fluorescently labeled, raspberry-like particles with varying roughness by electrostatically adsorbing silica nanoparticles with sizes between 40 nm and 250 nm on silica microparticles. Rougher pa...

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...

Gas sensors are essential in several fields and, in general, features such as high sensitivity, quick response, and fast recovery are required, along with low power consumption and low cost. Graphene is considered a promising material for gas sensing applications, its functionalization often being a requisite. In the present study, we developed com...