Light assisted synthesis of poly-para-phenylene on Ag(001)
V. Langlais, K. Schneider and H. Tang
Journal of Physics : Condensed Matter, 2022, 34, 055001
A detailed study of poly-para-phenylene (PPP) obtained by light-assisted on-surface-synthesis (OSS) on Ag(100) was carried out by scanning tunneling microscopy and spectroscopy together with density functional theory calculations. The use of light in combination with heat allows to lower by 50 K annealing temperature the each stage of the Ullmann coupling. Debromination of the 4,4’’ dibromo-p-terphenyl precursors was thus realized at 300 K, the formation of the first oligomers from the organometallic intermediate by silver bridging atom release at 423 K and PPP by complete elimination of the silver at 473 K. This approach to lower the reaction temperature permits to enhance the Ag(100) surface reactivity to become comparable to that of Cu(111). The underlying mechanism of light effect was proposed to occur via surface mediated excitation, with the creation of photoexcited electrons known as hot electrons correlated with surface plasmon excitation. This original pathway combining both light and heat provides an additional parameter to control OSS by separating the precursor activation stage from the diffusion.
Coordination of Ethylamine on Small Silver Clusters : Structural and Topological (ELF, QTAIM) Analyses
Corinne Lacaze-Dufaure, Yann Bulteau, Nathalie Tarrat, David Loffreda, Pierre Fau, Katia Fajerwerg, Myrtil L. Kahn, Franck Rabilloud, Christine Lepetit
Inorg. Chem. 2022
Amine ligands are expected to drive the organization of metallic centers as well as the chemical reactivity of silver clusters early growing during the very first steps of the synthesis of silver nanoparticles via an organometallic route. Density functional theory (DFT) computational studies have been performed to characterize the structure, the atomic charge distribution, and the planar two-dimensional (2D)/three-dimensional (3D) relative stability of small-size silver clusters (Agn, 2 ≤ n ≤ 7), with or without an ethylamine (EA) ligand coordinated to the Ag clusters. The transition from 2D to 3D structures is shifted from n = 7 to 6 in the presence of one EA coordinating ligand, and it is explained from the analysis of the Ag–N and Ag–Ag bond energies. For fully EA saturated silver clusters (Agn–EAn), the effect on the 2D/3D transition is even more pronounced with a shift between n = 4 and 5. Subsequent electron localization function (ELF) and quantum theory of atoms in molecules (QTAIM) topological analyses allow for the fine characterization of the dative Ag–N and metallic Ag–Ag bonds, both in nature and in strength. Electron transfer from ethylamine to the coordinated silver atoms induces an increase of the polarization of the metallic core.
Adsorption of single metallic atoms on self-assembled molecular domain of terephthalic acid
H. Tang, C. Durand and R. Coratger
Surfaces and Interfaces, 2021, 25, 101170
Cobalt and gold atoms have been deposited on self-assembled molecular domains of terephthalic acid and are studied using low temperature scanning tunneling microscopy and DFT calculations. These two types of atoms present different adsorption properties as well as peculiar electronic structures. Co atoms are firmly adsorbed on the molecules while Au is highly dependent of the presence of diffusing hydrogen atoms. These latter can also favour the possible desorption of the adatoms or change their adsorption site depending on the presence of defective molecules. The results open the way to new investigations concerning the use of single atoms or molecules for chemistry at the subnanometer scale.
Integration of the Rhombohedral BiSb(0001) Topological Insulator on a Cubic GaAs(001) Substrate
D. SADEK, D.S. DHUNGANA, R. CORATGER, C. DURAND, A. PROIETTI, Q. GRAVELIER, B. REIG, E. DARAN, P.F. FAZZINI, F. CRISTIANO, A. ARNOULT, S.R. PLISSARD
ACS Applied Materials and Interfaces 7 (2021) 3061
Bismuth–antimony alloy (Bi1 – xSbx) is the first reported 3D topological insulator (TI). Among many TIs reported to date, it remains the most promising for spintronic applications thanks to its large conductivity, its colossal spin Hall angle, and the possibility to build low-current spin-orbit-torque magnetoresistive random access memories. Nevertheless, the 2D integration of TIs on industrial standards is lacking. In this work, we report the integration of high-quality rhombohedral BiSb(0001) topological insulators on a cubic GaAs(001) substrate. We demonstrate a clear epitaxial relationship at the interface, a fully relaxed TI layer, and the growth of a rhombohedral matrix on top of the cubic substrate. The antimony composition of the Bi1 – xSbx layer is perfectly controlled and covers almost the whole TI window. For optimized growth conditions, the sample generates a semiconductor band structure at room temperature in the bulk and exhibits metallic surface states at 77 K.
Plasmonic-Induced Luminescence of MoSe2 Monolayers in a Scanning Tunneling Microscope
R. PECHOU, S. JIA, J. RIGOR, O. GUILLERMET, G. SEINE, J. LOU, N. LARGE, A. MLAYAH, R. CORATGER
ACS Photonics, 7 (2020) 3061
We report on a scanning tunneling microscopy-induced luminescence in MoSe2 monolayers supported by uniform and nanopatterned gold substrates. Luminescence intensity mappings, recorded with a nanometric spatial resolution, and spectroscopy measurements were performed and analyzed in terms of photon emission processes taking place within the tip–surface gap region, which supports strongly localized optical and electronic states. We found that, excited by tunneling electrons, the light emission is due to the radiative recombination of free excitons confined within the MoSe2 monolayer. Light emission is observed at positive and negative bias voltages with very different emission rates. The results are interpreted in terms of charge carrier injection in the MoSe2 layer. Additionally, electrodynamic simulations also stress that resonance between the emitted radiation and the surface plasmons formed in the tip–surface gap region plays a critical role in the emission process. When the MoSe2 layer lays on a nanopatterned gold substrate, its luminescence intensity, induced by the tunneling electrons, is enhanced by nearly an order of magnitude. Such an effect is observed here for the first time in scanning tunneling microscopy experiments. The luminescence enhancement is attributed to the surface plasmon properties of the nanopatterned gold substrate, which spectrally match the excitonic transition of the MoSe2 layer. We show that this surface-enhanced scanning tunneling microscope-induced light emission (SESTM-LE) effect is very useful for investigating the photon emission from localized emitters (e.g., quantum wells, quantum dots, molecules) with a subnanometer spatial resolution.
Control of the deprotonation of Terephthalic Acid assemblies on Ag(111) studied by DFT calculations and low temperature scanning tunneling microscopy
J. HEINZ, C. DURAND, H. TANG, R. CORATGER
Phys. Chem. Chem. Phys, 22 (2020) 3173.
This paper deals with the investigations of terephthalic acid (TPA) molecules deposited on a low reactive Ag(111) surface and studied using scanning tunneling microscopy (STM) at low temperature and DFT calculations. These investigations show that two deprotonation states energetically equivalent can be produced at the single molecule level. On self-assemblies, the mobility of H atoms at 77 K favours the motion of created defects in the layer. STM observations and DFT calculations show that the most stable structures are obtained when only one hydrogen atom is removed from an O–H⋯O bond and when these deprotonated molecules are located in adjacent TPA rows.
8-Hydroxyquinoline (8Hq) complexes on Al(111) : atomic scale structure, energetics and charge distribution
Yann Bulteau, Nathalie Tarrat, Nadine Pébère and Corinne Lacaze-Dufaure
New J. Chem. 2020, 44, 15209-15222
8-Hydroxyquinoline (8Hq) is known to efficiently inhibit the corrosion of aluminium by forming metal–organic layers (8Hq forms complexes with aluminium atoms). In the present work, the atomic scale structure and the energetics of 8-hydroxyquinoline complexes (Alq3) adsorbed on an aluminium surface are investigated by dispersion-corrected DFT computations. Two scenarios are considered : (i) an Alq3 complex, previously formed in vacuum, is deposited on a flat Al(111) surface or (ii) three deprotonated 8Hq molecules (q) directly adsorb on a defective Al(111) surface presenting Al adatoms (Al–Al(111)). For the Alq3 formation in vacuum, each addition of a q molecule on the Al atom stabilises the system, the oxidation state of the Al atom evolving from AlI in Alq to AlIII in Alq2 and Alq3. The subsequent deposition of Alq3 on Al(111) leads to a strong bonding between the q molecules of the complex and the Al(111) surface, with a significant electron transfer occurring from the surface to the complexes (0.73 to 1.57 e). The formation on the metal surface of Alq3 complexes via the adsorption of q molecules on an Al adatom leads to more stable structures than the ones obtained from direct adsorption of Alq3 on Al(111). For the most stable adsorption conformation, the three q molecules are bonded to the Al adatom but only two are bonded to the aluminium surface. In that case, the total electron transfer from the Al–Al(111) surface to the q molecules is 4.40 e and the electron transfer from the Al(111) surface to the Alq3-like species is 2.04 e. The structure, energetics and charge distribution data demonstrate an iono-covalent bonding between the q molecules and the Al atoms, in the complex as well as on the aluminium surface.
Performances of the Lamb Model to Describe the Vibrations of Gold Quantum-Sized Clusters
Quentin Martinet, Alice Berthelot, Adrien Girard, Baira Donoeva, Clothilde Comby-Zerbino, Elodie Romeo, Franck Bertorelle, Marte van der Linden, Nathalie Tarrat, Nicolas Combe and Jérémie Margueritat
J. Phys. Chem. C 2020, 124, 35, 19324–19332
Lamb modes describe the vibrations of an object as a whole from the stellar scale to the nanometer one. Lamb description has been built from the linear elasticity theory and considers a homogeneous elastic sphere. Our work tries to determine the minimum scale where this description remains valid by studying the vibration of quantum-sized gold clusters (Au6, Au9, and Au25) stabilized by organic molecules. First, our work shows that experimental frequencies of small-functionalized gold clusters obtained by low-frequency Raman spectroscopy can be interpreted with density functional theory calculations. Moreover, the Lamb model broadly succeeds in predicting these Raman acoustic modes only if a correction considering the mass of the surrounding ligands is added. Ligands affect vibrational modes of the core by their mass but also by their covalent bond with the core. The unexpected consequence of this electronic stabilization by the ligands is the sustainability of the Lamb description for clusters as small as six atoms. Finally, the limit of the Lamb model can be reached out at low temperature where the vibration mode spectrum presents a substructuration that the Lamb description, developed for a homogeneous sphere, is unable to predict.
Methoxy radical adsorption on gold nanoparticles : a comparison with methanethiol and methylamine radicals
Xavier Fenouillet, Magali Benoit, Nathalie Tarrat
Adsorption 2020, 26, 579–586
The adsorption of a methoxy radical (OCH3) on the low-energy flat gold surfaces Au(111), Au(100) and Au(110) and on surface defects (adatoms) was compared with those of methanethiol (SCH3) and methylamine (NHCH3) radicals. Using dispersion-corrected DFT, we showed that the adsorption energy of OCH3 on gold is significantly lower than that of SCH3 but not very far from that of NHCH3. Whatever the molecule, we found that the adsorption energy is of the same order on Au(110) and Au(100), and smaller on Au(111) and that the charge transfer goes from the surface to the molecule. The charge transferred to SCH3 is very small, while that transferred to NHCH3 is slightly larger, but still three times smaller than in the case of OCH3. Concerning the competition between adsorption sites, we observed that undercoordinated atoms are not systematically more favoured than flat surfaces.
Polymorphism in carbohydrate self-assembly at surfaces : STM imaging and theoretical modelling of trehalose on Cu(100)
Sabine Abb, Nathalie Tarrat, Juan Cortés, Bohdan Andriyevsky, Ludger Harnau, J. Christian Schön, Stephan Rauschenbach and Klaus Kern
RSC Adv. 2019, 9, 35813-35819
Saccharides, also commonly known as carbohydrates, are ubiquitous biomolecules, but little is known about their interaction with surfaces. Soft-landing electrospray ion beam deposition in conjunction with high-resolution imaging by scanning tunneling microscopy now provides access to the molecular details of the surface assembly of this important class of bio-molecules. Among carbohydrates, the disaccharide trehalose is outstanding as it enables strong anhydrobiotic effects in biosystems. This ability is closely related to the observed polymorphism. In this work, we explore the self-assembly of trehalose on the Cu(100) surface. Molecular imaging reveals the details of the assembly properties in this reduced symmetry environment. Already at room temperature, we observe a variety of self-assembled motifs, in contrast to other disaccharides like e.g. sucrose. Using a multistage modeling approach, we rationalize the conformation of trehalose on the copper surface as well as the intermolecular interactions and the self-assembly behavior.
Carbohydrate self‐assembly at surfaces : STM imaging of sucrose conformation and ordering on Cu(100)
Sabine Abb, Nathalie Tarrat, Juan Cortés, Bohdan Andriyevsky, Ludger Harnau, J. Christian Schön, Stephan Rauschenbach and Klaus Kern
Angewandte Chemie Int. Ed. 2019, 58, 8336
Saccharides are ubiquitous biomolecules but little is known about their interaction with and assembly on surfaces. Combining preparative mass spectrometry with scanning tunneling microscopy, we have been able to address the conformation and self‐assembly of the disaccharide sucrose on the Cu(100) surface with subunit‐level imaging. By combining a multi‐stage modelling approach and experimental data, we can rationalize the conformation on the surface as well as the interactions between the sucrose molecules, yielding models of the observed self‐assembled patterns on the surface.
Interaction between perylene-derivated molecules observed by low temperature scanning tunneling microscopy
L. VERNISSE, O. GUILLERMET, A. GOURDON, R. CORATGER
Derivative perylene molecules deposited on Ag(111) and on NaCl(001) ultrathin layers have been investigated using low temperature STM and NC-AFM. When the metallic substrate is held at ambient temperature during evaporation, the molecules form characteristic trimers on the Ag(111) surface and interact through their polar groups. Close to the steps, the molecules form linear structures and seems to stand side by side. On the other hand, after deposition on a substrate cooled at liquid helium temperature, single molecules are observed both on metal and on NaCl. On the ultrathin insulator layers, the STM images present characteristic contrasts related to the molecular orbitals which favors the localization of aldehyde groups. In this case, the lateral molecular interactions may induce the formation of small assemblies in which the electronic levels are slightly shifted. A possible interpretation of this phenomenon is to take into account polar interactions and charge transfer between neighboring molecules.
On the role of intermolecular interactions in stabilizing AuNP@Ampicillin nano-antibiotics
Xavier Fenouillet, Magali Benoit and Nathalie Tarrat
The fight against antibiotic resistance has become a major public health issue in recent years. In this context, nano-antibiotics composed of gold nanoparticles with antibiotics grafted on their surface often exhibit outstanding properties, sometimes even bypassing bacterial resistance mechanisms. Among these nano-antibiotics, gold nanoparticles/ampicillin hybrid systems (AuNPs@Ampicillin) are very effective. However, despite their very promising antibacterial properties, very little information concerning their atomic-scale structure is reported in the literature. In the present paper, the structure and energetics of AuNPs@Ampicillin nano-antibiotics have been investigated using first-principles numerical simulations through the study of the ampicillin adsorption on the three low Miller index facets Au(111), Au(100) and Au(110) of the AuNPs as a function of both the antibiotics coverage and its protonation state. Intermolecular interactions were found to be very stabilizing for coverages compatible with experimental data. An optimal coverage zone has been determined, in which the combination of a favorable gold surface-antibiotics interaction and of stabilizing intermolecular interactions can lead to an overall stabilization of the nano-antibiotics. As regards the mechanism of action of the nano-antibiotics, this study has confirmed that the active site of the free antibiotic is exposed to the solvent when the antibiotic is grafted onto the gold nanoparticle.
Adsorption of Terarylenes on Ag(111) and NaCl(001)/Ag(111) : A Scanning Tunneling Microscopy and Density Functional Theory Study
J. P. DELA CRUZ CALUPITAN, O. GALANGUAU, O. GUILLERMET, M. YENGUI, J. ETCHEVERRIA, X. BOUJU, T. NAKASHIMA, G. RAPENNE, R. CORATGER, T. KAWAI
Photoswitching materials are building blocks of next generation optoelectronic devices which may require molecule deposition on a solid substrate. However, molecule properties change upon adsorption due to surface-molecule interactions and symmetry considerations. Scanning tunneling microscopy (STM) and density functional theory (DFT) offer techniques to address interactions of functional molecules down to the single-molecular level on solid substrates. In this paper, we present a combined STM and DFT study of a tert-butyl functionalized terarylene molecule on Ag(111) and NaCl(001)/Ag(111) at ∼5 K. tert-Butyl groups aided in identifying three conformations of the compound upon adsorption on the surface. DFT calculations showed that two of these conformations refer to different adsorption geometries of the trans conformation in the gas phase. The other was assigned to the nonreactive cis conformation. For the first time, this conformation was isolated and imaged at the single-molecular level. Calculations further showed that aside from the electronic structure of the molecule, methyl groups sticking out of the surface are the origin of bright spots observed on the STM. On NaCl(001)/Ag(111), only the trans conformation was found and the mapping of occupied and unoccupied states of terarylenes was accomplished for the first time.