Publications by authors named "Roberto Lazzaroni"

107 Publications

Detection and Stabilization of a Previously Unknown Two-Dimensional (Pseudo)polymorph using Lateral Nanoconfinement.

J Am Chem Soc 2021 Jul 20. Epub 2021 Jul 20.

Division of Molecular Imaging and Photonics, Department of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium.

We report on the detection and stabilization of a previously unknown two-dimensional (2D) pseudopolymorph of an alkoxy isophthalic acid using lateral nanoconfinement. The self-assembled molecular networks formed by the isophthalic acid derivative were studied at the interface between covalently modified graphite and an organic solvent. When self-assembled on graphite with moderate surface coverage of covalently bound aryl groups, a previously unknown metastable pseudopolymorph was detected. This pseudopolymorph, which was presumably "trapped" in between the surface bound aryl groups, underwent a time-dependent phase transition to the stable polymorph typically observed on pristine graphite. The stabilization of the pseudopolymorph was then achieved by using an alternative nanoconfinement strategy, where the domains of the pseudopolymorph could be formed and stabilized by restricting the self-assembly in nanometer-sized shallow compartments produced by STM-based nanolithography carried out on a graphite surface with a high density of covalently bound aryl groups. These experimental results are supported by molecular mechanics and molecular dynamics simulations, which not only provide important insight into the relative stabilities of the different structures, but also shed light onto the mechanism of the formation and stabilization of the pseudopolymorph under nanoscopic lateral confinement.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jacs.1c04445DOI Listing
July 2021

Molecular dopant determines the structure of a physisorbed self-assembled molecular network.

Chem Commun (Camb) 2021 Feb;57(12):1454-1457

Division of Molecular Imaging and Photonics, Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium.

A small percentage of an impurity was shown, via scanning tunneling microscopy, to drastically change the on-surface self-assembly behavior of an aromatic tetracarboxylic acid, by initiating the nucleation and growth of a different polymorph. Molecular modelling simulations were used to shed further light onto the dopant-controlled assembly behaviour.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/d0cc07338eDOI Listing
February 2021

Monosaccharides Dehydration Assisted by Formation of Borate Esters of α-Hydroxyacids in Choline Chloride-Based Low Melting Mixtures.

Front Chem 2020 7;8:569. Epub 2020 Jul 7.

Laboratory of Biomass and Green Technologies, University of Liege-Gembloux Agro-Bio Tech, Gembloux, Belgium.

The synthesis of 5-hydroxymethylfurfural (5-HMF) and 2-furfural (2-F) by hexoses and pentoses dehydration is considered as a promising path to produce materials from renewable resources. Low-transition-temperature mixtures (LTTMs) enable selective (>80%) dehydration of ketoses to furanic derivatives at moderate temperature (<100°C). However, aldoses dehydration generally requires higher temperatures and an isomerization catalyst. Chromium trichloride has been reported as one of the most efficient catalyst but its kinetic inertness could limit its performances below 100°C. Consequently, we investigate herein boric acid catalysis of aldoses dehydration in LTTMs based on choline halides and organic acids at 90°C. The limited activity of boric acid regarding furanic compounds synthesis (e.g., 5% 5-HMF yield and 23% glucose conversion after 1 h at 90°C with maleic acid) can be enhanced through tetrahydroxyborate esters (THBE) formation with α-hydroxyacids (e.g., 19% 5-HMF yield and 61% glucose conversion after 1 h at 90°C). THBE formation is however associated with HO generation favoring the appearance of side products (humins). We demonstrate that boric acid catalysis is not straightforward and that the use of THBE under moderate acidity should be further investigated to limit humins formation and promote furanic derivatives synthesis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fchem.2020.00569DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7358950PMC
July 2020

Elastic conducting polymer composites in thermoelectric modules.

Nat Commun 2020 Mar 18;11(1):1424. Epub 2020 Mar 18.

Laboratory of Organic Electronics, Department of Science and Technology, Linköping University, 601 74, Norrköping, Sweden.

The rapid growth of wearables has created a demand for lightweight, elastic and conformal energy harvesting and storage devices. The conducting polymer poly(3,4-ethylenedioxythiophene) has shown great promise for thermoelectric generators, however, the thick layers of pristine poly(3,4-ethylenedioxythiophene) required for effective energy harvesting are too hard and brittle for seamless integration into wearables. Poly(3,4-ethylenedioxythiophene)-elastomer composites have been developed to improve its mechanical properties, although so far without simultaneously achieving softness, high electrical conductivity, and stretchability. Here we report an aqueously processed poly(3,4-ethylenedioxythiophene)-polyurethane-ionic liquid composite, which combines high conductivity (>140 S cm) with superior stretchability (>600%), elasticity, and low Young's modulus (<7 MPa). The outstanding performance of this organic nanocomposite is the result of favorable percolation networks on the nano- and micro-scale and the plasticizing effect of the ionic liquid. The elastic thermoelectric material is implemented in the first reported intrinsically stretchable organic thermoelectric module.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-020-15135-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7080746PMC
March 2020

In Depth Analysis of Photovoltaic Performance of Chlorophyll Derivative-Based "All Solid-State" Dye-Sensitized Solar Cells.

Molecules 2020 Jan 3;25(1). Epub 2020 Jan 3.

ICGM, Univ. Montpellier, CNRS, ENSCM, CC1701, Place Eugène Bataillon, 34095 Montpellier, France.

Chlorophyll derivatives were integrated in "all solid-state" dye sensitized solar cells (DSSCs) with a mesoporous TiO electrode and 2',2',7,7'-tetrakis[,-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene as the hole-transport material. Despite modest power conversion efficiencies (PCEs) between 0.26% and 0.55% achieved for these chlorin dyes, a systematic investigation was carried out in order to elucidate their main limitations. To provide a comprehensive understanding of the parameters (structure, nature of the anchoring group, adsorption …) and their relationship with the PCEs, density functional theory (DFT) calculations, optical and photovoltaic studies and electron paramagnetic resonance analysis exploiting the 4-carboxy-TEMPO spin probe were combined. The recombination kinetics, the frontier molecular orbitals of these DSSCs and the adsorption efficiency onto the TiO surface were found to be the key parameters that govern their photovoltaic response.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/molecules25010198DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6983229PMC
January 2020

Templating Porphyrin Anisotropy via Magnetically Aligned Carbon Nanotubes.

Chempluschem 2019 Sep 22;84(9):1270-1278. Epub 2019 Feb 22.

School of Chemistry, Cardiff University Park Place Main Building, CF10 3AT, United Kingdom.

The preparation and characterisation of a novel three-dimensional organic material consisting of porphyrin arrays on carbon nanotubes embedded in an organogel is reported. Firstly, the porphyrin array was prepared through metal-ligand coordination of a ditopic ligand (1,2-bis(4-pyridyl)ethane) and two bis-Zn(II) porphyrins, linked through a pyrene core, and was studied through UV-Vis, NMR and diffusion spectroscopies. Secondly, the porphyrin supramolecular architecture was adsorbed on pristine carbon nanotubes, greatly improving the dispersibility of the latter in organic solvents. The hybrid material was characterised by means of UV-Vis spectroscopy, microscopic techniques and thermogravimetric analysis. Finally, by exploiting the anisotropic magnetic susceptibility of carbon nanotubes, the hybrid material was aligned under a magnetic field, the organisation of which could be maintained by in situ gelation. The resultant hybrid organogel exhibited notable optical anisotropy, suggesting an anisotropic arrangement of the porphyrin-CNTs architectures in the macroscopic material.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/cplu.201800623DOI Listing
September 2019

Organogel Formation Rationalized by Hansen Solubility Parameters: Shift of the Gelation Sphere with the Gelator Structure.

Langmuir 2019 Jun 29;35(24):7970-7977. Epub 2019 May 29.

Sorbonne Université, CNRS, Institut Parisien de Chimie Moléculaire (IPCM), Equipe Chimie des Polymères , F-75005 Paris , France.

To rationalize how the gelation ability of a low molecular weight gelator is influenced by its molecular structure, we performed extensive solubility tests of a group of thiazole-based gelators and made use of Hansen solubility parameter formalism. We observe that the increase of a linear alkyl chain in these gelators promotes an increase of the radius of the gelation sphere as well as a gradual shift of its center to lower values of the polar (δ) and hydrogen bonding (δ) components. The molecular packing within the fibers and the crystal habit were determined by a combination of X-ray diffraction and molecular modeling. We attribute the gradual and linear shift of the gelation sphere to the fact that all of the studied gelators share the same molecular packing, so that an increasing length of the alkyl chain reduces the proportion of polar groups at the surface, resulting in a gradual increase in the contact between apolar parts of the fiber and the solvent.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.langmuir.9b00966DOI Listing
June 2019

Hybrid Interface in Sepiolite Rubber Nanocomposites: Role of Self-Assembled Nanostructure in Controlling Dissipative Phenomena.

Nanomaterials (Basel) 2019 Mar 27;9(4). Epub 2019 Mar 27.

Department of Materials Science, INSTM, University of Milano-Bicocca, Via R. Cozzi, 55, 20125 Milano, Italy.

Sepiolite (Sep)⁻styrene butadiene rubber (SBR) nanocomposites were prepared by using nano-sized sepiolite (NS-SepS9) fibers, obtained by applying a controlled surface acid treatment, also in the presence of a silane coupling agent (NS-SilSepS9). Sep/SBR nanocomposites were used as a model to study the influence of the modified sepiolite filler on the formation of immobilized rubber at the clay-rubber interface and the role of a self-assembled nanostructure in tuning the mechanical properties. A detailed investigation at the macro and nanoscale of such self-assembled structures was performed in terms of the organization and networking of Sep fibers in the rubber matrix, the nature of both the filler⁻filler and filler⁻rubber interactions, and the impact of these features on the reduced dissipative phenomena. An integrated multi-technique approach, based on dynamic measurements, nuclear magnetic resonance analysis, and morphological investigation, assessed that the macroscopic mechanical properties of clay nanocomposites can be remarkably enhanced by self-assembled filler structures, whose formation can be favored by manipulating the chemistry at the hybrid interfaces between the clay particles and the polymers.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/nano9040486DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6523625PMC
March 2019

Graphene Meets Ionic Liquids: Fermi Level Engineering via Electrostatic Forces.

ACS Nano 2019 Mar 12;13(3):3512-3521. Epub 2019 Mar 12.

Division of Molecular Imaging and Photonics, Department of Chemistry , KU Leuven , Celestijnenlaan, 200F , B-3001 Leuven , Belgium.

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 that can be stored in such supercapacitors critically depends on the electrode-electrolyte interface, there is considerable interest in understanding the structure and properties of the graphene/IL interface. Here, we report the changes in the properties of graphene upon adsorption of a homologous series of alkyl imidazolium tetrafluoroborate ILs using a combination of experimental and theoretical tools. Raman spectroscopy reveals that these ILs cause n-type doping of graphene, and the magnitude of doping increases with increasing cation chain length despite the expected decrease in the density of surface-adsorbed ions. Molecular modeling simulations show that doping originates from the changes in the electrostatic potential at the graphene/IL interface. The findings described here represent an important step in developing a comprehensive understanding of the graphene/IL interface.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsnano.8b09768DOI Listing
March 2019

A scanning probe microscopy study of nanostructured TiO/poly(3-hexylthiophene) hybrid heterojunctions for photovoltaic applications.

Beilstein J Nanotechnol 2018 1;9:2087-2096. Epub 2018 Aug 1.

Laboratory for Chemistry of Novel Materials - Center for Innovation and Research in Materials and Polymers - CIRMAP, University of Mons, Mons, Belgium.

The nanoscale morphology of photoactive hybrid heterojunctions plays a key role in the performances of hybrid solar cells. In this work, the heterojunctions consist of a nanocolumnar TiO surface covalently grafted with a monolayer of poly(3-hexylthiophene) (P3HT) functionalized with carboxylic groups (-COOH). Through a joint analysis of the photovoltaic properties at the nanoscale by photoconductive-AFM (PC-AFM) and surface photovoltage imaging, we investigated the physical mechanisms taking place locally during the photovoltaic process and the correlation to the nanoscale morphology. A down-shift of the vacuum level of the TiO surface upon grafting was measured by Kelvin probe force microscopy (KPFM), evidencing the formation of a dipole at the TiO/P3HT-COOH interface. Upon in situ illumination, a positive photovoltage was observed as a result of the accumulation of photogenerated holes in the P3HT layer. A positive photocurrent was recorded in PC-AFM measurements, whose spatial mapping was interpreted consistently with the corresponding KPFM analysis, offering a correlated analysis of interest from both a theoretical and material design perspective.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3762/bjnano.9.197DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6122299PMC
August 2018

Do Carbon Nanotubes Improve the Thermomechanical Properties of Benzoxazine Thermosets?

ACS Appl Mater Interfaces 2018 Aug 30;10(31):26669-26677. Epub 2018 Jul 30.

Materia Nova R&D Center , Avenue Copernic 1, Parc Initialis , 7000 Mons , Belgium.

Fillers are widely used to improve the thermomechanical response of polymer matrices, yet often in an unpredictable manner because the relationships between the mechanical properties of the composite material and the primary (chemical) structure of its molecular components have remained elusive so far. Here, we report on a combined theoretical and experimental study of the structural and thermomechanical properties of carbon nanotube (CNT)-reinforced polybenzoxazine resins, as prepared from two monomers that only differ by the presence of two ethyl side groups. Remarkably, while addition of CNT is found to have no impact on the glass-transition temperature ( T) of the ethyl-decorated resin, the corresponding ethyl-free composite features a surge by ∼47 °C (50 °C) in T, from molecular dynamics simulations (dynamic mechanical analysis measurements), as compared to the neat resin. Through a detailed theoretical analysis, we propose a microscopic picture for the differences in the thermomechanical properties of the resins, which sheds light on the relative importance of network topology, cross-link and hydrogen-bond density, chain mobility, and free volume.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsami.8b08473DOI Listing
August 2018

Hierarchical self-assembly of enantiopure and racemic helicenes at the liquid/solid interface: from 2D to 3D.

Nanoscale 2017 Nov;9(45):18075-18080

Department of Chemistry, Division of Molecular Imaging and Photonics, KU Leuven-University of Leuven, Celestijnenlaan 200-F, 3001 Leuven, Belgium.

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-bound molecule to well-defined microstructures, using a combination of various characterization techniques assisted by molecular modeling simulations. Similarities as well as discrepancies are revealed between homochiral and heterochiral aggregations by monitoring the hierarchical nucleation of helicenes on surfaces, where the impact of enantiopurity, concentration and adsorbate-substrate interaction on molecular organization are disclosed.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c7nr06700cDOI Listing
November 2017

Influence of the nature of the anchoring group on electron injection processes at dye-titania interfaces.

Phys Chem Chem Phys 2017 Nov;19(43):29389-29401

Laboratoire de Chimie Analytique Appliquée, Matériaux et Environnement (LC2AME), Faculté des Sciences, Université Mohammed Premier, B. P. Box 4808, 60046 Oujda, Morocco.

We report (time-dependent) density functional theory calculations characterizing the changes in the electronic and optical properties of oligothiophene dyes when grafted on a titania surface via a carboxylic acid or catechol moiety as anchoring group, in relation to their use in dye-sensitized solar cells. The broadening of the LUMO level of the compounds upon adsorption has been extracted from the computed electronic structures and used to estimate electron injection times into the conduction band of the oxide. The strongly coupled carboxylic-containing dyes lead to faster electron injection times compared to catechol-substituted dyes. This difference is ascribed to the electron-donating character of the catechol moiety that polarizes the dye LUMO away from the [email protected] interface. The absorption spectra simulated at the TD-DFT level indicate that the grafted carboxylic-thiophene dyes undergo an indirect injection mechanism (type I) in which an intramolecular excitation is created before the charge is transferred to titania. In contrast, catechol dyes with a short conjugation length for the thiophene backbone are type II sensitizers exhibiting a direct injection mechanism leading to a direct photoexcitation from the dye HOMO to the titania conduction band. A mixed character prevails for the injection in the case of catechol dyes containing a longer oligothiophene chain.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c7cp05638aDOI Listing
November 2017

Mechanochemical Synthesis of PEDOT:PSS Hydrogels for Aqueous Formulation of Li-Ion Battery Electrodes.

ACS Appl Mater Interfaces 2017 Oct 26;9(40):34865-34874. Epub 2017 Sep 26.

NEXT ENERGY·EWE-Forschungszentrum für Energietechnologie e.V. , Carl von Ossietzky University Oldenburg, 26129 Oldenburg, Germany.

Water-soluble binders can enable greener and cost-effective Li-ion battery manufacturing by eliminating the standard fluorine-based formulations and associated organic solvents. The issue with water-based dispersions, however, remains the difficulty in stabilizing them, requiring additional processing complexity. Herein, we show that mechanochemical conversion of a regular poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) water-based dispersion produces a hydrogel that meets all the requirements as binder for lithium-ion battery electrode manufacture. We particularly highlight the suitable slurry rheology, improved adhesion, intrinsic electrical conductivity, large potential stability window and limited corrosion of metal current collectors and active electrode materials, compared to standard binder or regular PEDOT:PSS solution-based processing. When incorporating the active materials, conductive carbon and additives with PEDOT:PSS, the mechanochemical processing induces simultaneous binder gelation and fine mixing of the components. The formed slurries are stable, show no phase segregation when stored for months, and produce highly uniform thin (25 μm) to very thick (500 μm) films in a single coating step, with no material segregation even upon slow drying. In conjunction with PEDOT:PSS hydrogels, technologically relevant materials including silicon, tin, and graphite negative electrodes as well as LiCoO, LiMnO, LiFePO, and carbon-sulfur positive electrodes show superior cycling stability and power-rate performances compared to standard binder formulation, while significantly simplifying the aqueous-based electrode assembly.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsami.7b08937DOI Listing
October 2017

Transfer of chiral information from a chiral solvent to a two-dimensional network.

Faraday Discuss 2017 10;204:215-231

Division of Molecular Imaging and Photonics, Department of Chemistry, KU Leuven-University of Leuven, Celestijnenlaan 200F, B 3001, Leuven, Belgium.

Chiral induction in self-assembled monolayers has garnered considerable attention in the recent past, not only due to its importance in chiral resolution and enantioselective heterogeneous catalysis but also because of its relevance to the origin of homochirality in life. Here, we demonstrate the emergence of homochirality in a supramolecular low-density network formed by achiral molecules at the interface of a chiral solvent and an atomically-flat achiral substrate. We focus on the impact of structure and functionality of the adsorbate and the chiral solvent on the chiral induction efficiency in self-assembled physisorbed monolayers, as revealed by scanning tunneling microscopy. Different induction mechanisms are proposed and evaluated, with the assistance of advanced molecular modeling simulations.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c7fd00103gDOI Listing
October 2017

Chiral supramolecular organization and cooperativity in DNA-templated assemblies of Zn-chromophore complexes.

Chem Commun (Camb) 2016 Nov;52(96):13873-13876

Laboratory for Chemistry of Novel Materials, Center for Innovation in Materials and Polymers, University of Mons - UMONS, 20 Place du Parc, B-7000 Mons, Belgium.

Templated cooperative binding induced assembly of chromophores is achieved via interactions between Zn-complexes and the DNA phosphodiester backbone. The chromophores are organized in left-handed (M)-helices via double-zipper assembly with the DNA templates.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c6cc07414fDOI Listing
November 2016

Tuning the structure of 1,3,5-benzene tricarboxamide self-assemblies through stereochemistry.

Chem Commun (Camb) 2016 Nov;52(91):13369-13372

Sorbonne Universités, UPMC Univ Paris 06, CNRS, Institut Parisien de Chimie Moléculaire, 4 Place Jussieu, F-75005 Paris, France.

A heterochiral 1,3,5-benzene tricarboxamide (BTA) monomer, derived from valine dodecyl ester, forms long rods in cyclohexane whilst its homochiral analogue assembles into dimers only at the same concentration. This highly original assembly behaviour is related to the destabilization of the dimeric structure containing the two heterochiral monomers as corroborated by a combined experimental and computational study.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c6cc07325eDOI Listing
November 2016

Tuning the nature and stability of self-assemblies formed by ester benzene 1,3,5-tricarboxamides: the crucial role played by the substituents.

Soft Matter 2016 Sep;12(37):7824-7838

Sorbonne Universités, UPMC Univ Paris 06, CNRS, Institut Parisien de Chimie Moléculaire, Equipe Chimie des Polymeres, 4 Place Jussieu, F-75005 Paris, France.

As the benzene 1,3,5-tricarboxamide (BTA) moiety is commonly used as the central assembling unit for the construction of functionalized supramolecular architectures, strategies to tailor the nature and stability of BTA assemblies are needed. The assembly properties of a library of structurally simple BTAs derived from amino dodecyl esters (ester BTAs, 13 members) have been studied, either in the bulk or in cyclohexane solutions, by means of a series of analytical methods (NMR, DSC, POM, FT-IR, UV-Vis, CD, ITC, high-sensitivity DSC, SANS). Two types of hydrogen-bonded species have been identified and characterized: the expected amide-bonded helical rods (or stacks) that are structurally similar to those formed by BTAs with simple alkyl side chains (alkyl BTAs), and ester-bonded dimers in which the BTAs are connected by means of hydrogen bonds linking the amide N-H and the ester C[double bond, length as m-dash]O. MM/MD calculations coupled with simulations of CD spectra allow for the precise determination of the molecular arrangement and of the hydrogen bond pattern of these dimers. Our study points out the crucial influence of the substituent attached on the amino-ester α-carbon on the relative stability of the rod-like versus dimeric assemblies. By varying this substituent, one can precisely tune the nature of the dominant hydrogen-bonded species (stacks or dimers) in the neat compounds and in cyclohexane over a wide range of temperatures and concentrations. In the neat BTAs, stacks are stable up to 213 °C and dimers above 180 °C whilst in cyclohexane stacks form at c* > 3 × 10 M at 20 °C and dimers are stable up to 80 °C at 7 × 10 M. Ester BTAs that assemble into stacks form a liquid-crystalline phase and yield gels or viscous solutions in cyclohexane, demonstrating the importance of controlling the structure of these assemblies. Our systematic study of these structurally similar ester BTAs also allows for a better understanding of how a single atom or moiety can impact the nature and stability of BTA aggregates, which is of importance for the future development of functionalized BTA supramolecular polymers.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c6sm01601dDOI Listing
September 2016

Light-enhanced liquid-phase exfoliation and current photoswitching in graphene-azobenzene composites.

Nat Commun 2016 Apr 7;7:11090. Epub 2016 Apr 7.

Nanochemistry Laboratory, ISIS &icFRC, Université de Strasbourg &CNRS, 8 allée Gaspard Monge, 67000 Strasbourg, France.

Multifunctional materials can be engineered by combining multiple chemical components, each conferring a well-defined function to the ensemble. Graphene is at the centre of an ever-growing research effort due to its combination of unique properties. Here we show that the large conformational change associated with the trans-cis photochemical isomerization of alkyl-substituted azobenzenes can be used to improve the efficiency of liquid-phase exfoliation of graphite, with the photochromic molecules acting as dispersion-stabilizing agents. We also demonstrate reversible photo-modulated current in two-terminal devices based on graphene-azobenzene composites. We assign this tuneable electrical characteristics to the intercalation of the azobenzene between adjacent graphene layers and the resulting increase in the interlayer distance on (photo)switching from the linear trans-form to the bulky cis-form of the photochromes. These findings pave the way to the development of new optically controlled memories for light-assisted programming and high-sensitive photosensors.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/ncomms11090DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4829665PMC
April 2016

Expanding the light absorption of poly(3-hexylthiophene) by end-functionalization with π-extended porphyrins.

Chem Commun (Camb) 2016 Jan;52(1):171-4

Institut Charles Gerhardt, Université de Montpellier, Place Eugène Bataillon, 34095 Montpellier Cedex 05, France.

Poly(3-hexylthiophene)s end-functionalized with π-extended porphyrins have been synthesized in a one-pot procedure. The polymers show a broad absorption profile extending to 700 nm and a fibrillar microstructure, which can be tuned through judicious selection of the porphyrin molar ratio.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c5cc06290jDOI Listing
January 2016

Perylene Derivatives As Useful SERRS Reporters, Including Multiplexing Analysis.

ACS Appl Mater Interfaces 2015 Dec 7;7(51):28042-8. Epub 2015 Aug 7.

Center of Excellence for Nanostructured Materials, Dipartimento di Scienze Chimiche e Farmaceutiche, INSTM unit of Trieste, University of Trieste , Piazzale Europa 1, 34127 Trieste, Italy.

Five perylene bisimide (PBI) derivatives were designed and synthesized, on the basis of quantum-chemical calculations. The influence of halogen substituents on the shape and energy of the frontier orbitals and the Raman spectra were calculated, in the prospect use in surface-enhanced resonance Raman scattering (SERRS) studies. The corresponding experiments confirmed a very strong SERRS response in the presence of pristine (i.e., uncoated) gold nanoparticles. These spectra can be used for multiplexing measurements, namely measurements in which, by using a single laser excitation, one can recognize the simultaneous presence of several analytes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsami.5b03586DOI Listing
December 2015

Self-assembly and hybridization mechanisms of DNA with cationic polythiophene.

Soft Matter 2015 Aug 16;11(32):6460-71. Epub 2015 Jul 16.

Laboratory for Chemistry of Novel Materials, Center for Innovation in Materials and Polymers, University of Mons - UMONS, 20 Place du Parc, B-7000 Mons, Belgium.

The combination of DNA and π-conjugated polyelectrolytes (CPEs) represents a promising approach to develop DNA hybridization biosensors, with potential applications for instance in the detection of DNA lesions and single-nucleotide polymorphisms. Here we exploit the remarkable optical properties of a cationic poly[3-(6'-(trimethylphosphonium)hexyl)thiophene-2,5-diyl] (CPT) to decipher the self-assembly of DNA and CPT. The ssDNA/CPT complexes have chiroptical signatures in the CPT absorption region that are strongly dependent on the DNA sequence, which we relate to differences in supramolecular interactions between the thiophene monomers and the various nucleobases. By studying DNA-DNA hybridization and melting processes on preformed ssDNA/CPT complexes, we observe sequence-dependent mechanisms that can yield DNA-condensed aggregates. Heating-cooling cycles show that non-equilibrium mixtures can form, noticeably depending on the working sequence of the hybridization experiment. These results are of high importance for the use of π-conjugated polyelectrolytes in DNA hybridization biosensors and in polyplexes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c5sm01484kDOI Listing
August 2015

Synthesis of TiO2-poly(3-hexylthiophene) hybrid particles through surface-initiated Kumada catalyst-transfer polycondensation.

Langmuir 2014 Sep 18;30(38):11340-7. Epub 2014 Sep 18.

Laboratory of Polymeric and Composite Materials, Center of Innovation and Research in Materials and Polymers (CIRMAP), University of Mons UMONS , Place du Parc 20, 7000 Mons, Belgium.

TiO2/conjugated polymers are promising materials in solar energy conversion where efficient photoinduced charge transfers are required. Here, a "grafting-from" approach for the synthesis of TiO2 nanoparticles supported with conjugated polymer brushes is presented. Poly(3-hexylthiophene) (P3HT), a benchmark material for organic electronics, was selectively grown from TiO2 nanoparticles by surface-initiated Kumada catalyst-transfer polycondensation. The grafting of the polymer onto the surface of the TiO2 nanoparticles by this method was demonstrated by (1)H and (13)C solid-state NMR, X-ray photoelectron spectrometry, thermogravimetric analysis, transmission electron microscopy, and UV-visible spectroscopy. Sedimentation tests in tetrahydrofuran revealed improved dispersion stability for the [email protected] hybrid material. Films were produced by solvent casting, and the quality of the dispersion of the modified TiO2 nanoparticles was evaluated by atomic force microscopy. The dispersion of the P3HT-coated TiO2 NPs in the P3HT matrix was found to be homogeneous, and the fibrillar structure of the P3HT matrix was maintained which is favorable for charge transport. Fluorescence quenching measurements on these hybrid materials in CHCl3 indicated improved photoinduced electron-transfer efficiency. All in all, better physicochemical properties for P3HT/TiO2 hybrid material were reached via the surface-initiated "grafted-from" approach compared to the "grafting-onto" approach.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/la502944gDOI Listing
September 2014

Affecting surface chirality via multicomponent adsorption of chiral and achiral molecules.

Chem Commun (Camb) 2014 Oct;50(80):11903-6

Division of Molecular Imaging and Photonics, Department of Chemistry, KU Leuven, Celestijnenlaan 200 F, B-3001 Leuven, Belgium.

Here we report on the apparent reduction in surface chirality upon co-assembling a chiral and achiral molecule into a physisorbed self-assembled monolayer at the liquid/solid interface as revealed by scanning tunneling microscopy (STM). Chiral OPV with achiral thymine gives rise to surface-confined supramolecular diastereomers.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c4cc04393fDOI Listing
October 2014

Ammonium betaines: efficient ionic nucleophilic catalysts for the ring-opening polymerization of L-lactide and cyclic carbonates.

Chem Commun (Camb) 2014 Sep;50(70):10098-101

Center of Innovation and Research in Materials and Polymers (CIRMAP), Laboratory of Polymeric and Composite Materials, University of Mons (UMONS), Place du Parc, 23, 7000 Mons, Belgium.

The ionic nucleophilic character of ammonium betaine catalysts allows for controlling the ROP of L-LA for DP as high as 750 with very narrow dispersity values (≤1.18). Compared to ionic nucleophilic and hydrogen-bonding based catalysts for ROP, meta-betaine combines the positive aspects of both processes in terms of kinetics and selectivity. The versatility of ammonium betaines was evidenced by varying the nature of the initiating alcohol and monomer used.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c4cc03347gDOI Listing
September 2014

25th anniversary article: high-mobility hole and electron transport conjugated polymers: how structure defines function.

Adv Mater 2014 Apr 5;26(14):2119-36. Epub 2014 Mar 5.

Laboratory for Chemistry of Novel Materials, University of Mons-UMONS, Place du Parc 20, B-7000, Mons, Belgium.

The structural organization of three different families of semicrystalline π-conjugated polymers is reported (poly(3-hexylthiophene) (P3HT), poly[2,6-(4,4-bis-alkyl-4H-cyclopenta-[2,1-b;3,4-b0]-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)](cyclopentadithiophene-benzothiadiazole) (CDT-BTZ) and poly(N,N"-bis-2-octyldodecylnaphtalene-1,4,5,8-bis-dicarboximide-2,6-diyl-alt-5,5-2,2-bithiophene (P(NDI2OD-T2))). These have triggered significant interest for their remarkable charge-transport properties. By performing molecular mechanics/dynamics simulations with carefully re-parameterized force fields, it is illustrated in particular how the supramolecular organization of these conjugated polymers is driven by an interplay between the length and nature of the conjugated monomer unit and the packing of their alkyl side chains, and to what extent it impacts the charge-carrier mobility, as monitored by quantum-chemical calculations of the intermolecular hopping transfer integrals. This Progress Report is concluded by providing generic guidelines for the design of materials with enhanced degrees of supramolecular organization.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/adma.201305809DOI Listing
April 2014

8-HaloBODIPYs and their 8-(C, N, O, S) substituted analogues: solvent dependent UV-vis spectroscopy, variable temperature NMR, crystal structure determination, and quantum chemical calculations.

J Phys Chem A 2014 Mar 19;118(9):1576-94. Epub 2014 Feb 19.

Department of Chemistry, Katholieke Universiteit Leuven , Celestijnenlaan 200f - bus 02404, 3001 Leuven, Belgium.

The UV-vis electronic absorption and fluorescence emission properties of 8-halogenated (Cl, Br, I) difluoroboron dipyrrin (or 8-haloBODIPY) dyes and their 8-(C, N, O, S) substituted analogues are reported. The nature of the meso-substituent has a significant influence on the spectral band positions, the fluorescence quantum yields, and lifetimes. As a function of the solvent, the spectral maxima of all the investigated dyes are located within a limited wavelength range. The spectra of 8-haloBODIPYs display the narrow absorption and fluorescence emission bands and the generally quite small Stokes shifts characteristic of classic difluoroboron dipyrrins. Conversely, fluorophores with 8-phenylamino (7), 8-benzylamino (8), 8-methoxy (9), and 8-phenoxy (10) groups emit in the blue range of the visible spectrum and generally have larger Stokes shifts than common BODIPYs, whereas 8-(2-phenylethynyl)BODIPY (6) has red-shifted spectra compared to ordinary BODIPY dyes. Fluorescence lifetimes for 6, 8, and 10 have been measured for a large set of solvents and the solvent effect on their absorption and emission maxima has been analyzed using the generalized Catalán solvent scales. Restricted rotation about the C8-N bond in 7 and 8 has been observed via temperature dependent (1)H NMR spectroscopy, whereas for 10 the rotation about the C8-O bond is not hindered. The crystal structure of 8 demonstrates that the short C8-N bond has a significant double character and that this N atom exhibits a trigonal planar geometry. The crystal structure of 10 shows a short C8-O bond and an intramolecular C-H···π interaction. Quantum-chemical calculations have been performed to assess the effect of the meso-substituent on the spectroscopic properties.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jp412132yDOI Listing
March 2014

New carboxysilane-coated iron oxide nanoparticles for nonspecific cell labelling.

Contrast Media Mol Imaging 2013 Nov-Dec;8(6):466-74

UMONS, Department of General, Organic and Biomedical Chemistry, NMR and Molecular Imaging Laboratory, B-7000, Mons, Belgium.

Magnetic resonance imaging (MRI) offers the possibility of tracking cells labelled with a contrast agent and evaluating the progress of cell therapies. This requires efficient cell labelling with contrast agents. A basic incubation of cells with iron oxide nanoparticles (NPs) is a common method. This study reports the synthesis at the gram scale of iron oxide nanoparticles as MRI T₂ contrast agents for cell labelling. These NPs are based on small iron oxide cores coated with a thin polysiloxane shell presenting carboxylic acid functions. The iron oxide cores produced have been characterized by transmission electron microscopy, X-ray diffraction, ζ-potential, infrared, photon correlation spectroscopy, atomic force microscopy, magnetometry and relaxometric measurements. These measurements confirmed the expected surface modification by carboxysilane. Carboxylic groups created electrostatic repulsion between NPs when they are deprotonated. Therefore, highly concentrated aqueous solutions of carboxysilane coated iron oxide NPs can be obtained, up to 70% (w/w). These NPs could be used for cell labelling owing to their aggregation and re-dispersion properties. NPs precipitated in Dulbecco's modified Eagle medium induced a rapid association with 3 T6 fibroblast cells and could easily be re-dispersed in phosphate buffer saline solution to obtain properly labelled cells.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/cmmi.1552DOI Listing
August 2014

Modification of the adhesive properties of silicone-based coatings by block copolymers.

Langmuir 2014 Jan 20;30(1):358-68. Epub 2013 Dec 20.

Laboratory for Chemistry of Novel Materials, Center of Innovation and Research in Materials and Polymers (CIRMAP), Research Institute for Materials Science and Engineering, University of Mons (UMONS) , 20 Place du Parc, 7000 Mons, Belgium.

The improvement of the (bio)adhesive properties of elastomeric polydimethylsiloxane (PDMS) coatings is reported. This is achieved by a surface modification consisting of the incorporation of block copolymers containing a PDMS block and a poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) block in a PDMS matrix, followed by matrix cross-linking and immersion of the obtained materials in water. Contact angle measurements (CA), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) showed the presence of the PDMAEMA block at the surface, drastic morphology changes, and improved adhesion properties after immersion in water. Finally, underwater bioadhesion tests show that mussels adhere only to block copolymer-filled coatings and after immersion in water, i.e., when the PDMAEMA blocks have been brought to the coating surface. These observations highlight the significant role of hydrophilic groups in the surface modification of silicone coatings.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/la403995qDOI Listing
January 2014

Functional layers for Zn(II) ion detection: from molecular design to optical fiber sensors.

J Phys Chem B 2014 Jan 20;118(1):309-14. Epub 2013 Dec 20.

Max Planck Institute for Polymer Research , Ackermannweg 10, D-55128 Mainz, Germany.

We report on the synthesis of a novel perylene monoimide derivative that shows high response and selectivity for zinc ion detection. The complexation of Zn(2+) by the dye is followed by FD-MS, (1)H NMR, UV-vis spectroscopy, and isothermal titration calorimetry. Quantum chemical calculations are performed to gain further insight into the electronic processes responsible for the spectroscopic changes observed upon complexation. Finally, the perylene dye is incorporated in a sol-gel silica layer coated on optical fibers that are then used for Zn(2+) detection in aqueous solution.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jp407460cDOI Listing
January 2014