A5082581896- Catalytic Processes in Materials Science
- Electronic and Structural Properties of Oxides
- Molecular Junctions and Nanostructures
- Advanced Photocatalysis Techniques
- Copper-based nanomaterials and applications
- Electron and X-Ray Spectroscopy Techniques
- ZnO doping and properties
- Quantum Dots Synthesis And Properties
- Catalysis and Oxidation Reactions
- Surface and Thin Film Phenomena
- Semiconductor materials and devices
- Chalcogenide Semiconductor Thin Films
- Advanced Materials Characterization Techniques
- TiO2 Photocatalysis and Solar Cells
- Gas Sensing Nanomaterials and Sensors
- Advanced Chemical Physics Studies
- Semiconductor materials and interfaces
- Organic Electronics and Photovoltaics
- nanoparticles nucleation surface interactions
- X-ray Diffraction in Crystallography
- Nanocluster Synthesis and Applications
- Intermetallics and Advanced Alloy Properties
- Force Microscopy Techniques and Applications
- Surface Chemistry and Catalysis
- Nanomaterials for catalytic reactions
Centre National de la Recherche Scientifique
2016-2025
Sorbonne Université
2016-2025
Institut des NanoSciences de Paris
2016-2025
Sorbonne Paris Cité
2018-2020
UPMC Health System
2017
Délégation Paris 6
2017
London Centre for Nanotechnology
2006-2013
University College London
2007-2013
Trinity College Dublin
2003-2013
Université Paris Cité
2009-2013
Oxygen vacancies on metal oxide surfaces have long been thought to play a key role in the surface chemistry. Such processes directly visualized case of model photocatalyst TiO 2 (110) reactions with water and molecular oxygen. These assumed be neutral calculations properties. However, by comparing experimental simulated scanning tunneling microscopy images spectra, we show that oxygen act as trapping centers are negatively charged. We demonstrate charging defect significantly affects...
The origin of the catalytic activity gold nanoparticles remains debated despite extensive studies. This in operando work investigates relationship between and size/shape supported on TiO2(110) during CO oxidation. were synthesized by vapor deposition ultrahigh vacuum. Their geometry was monitored presence O2, Ar, or a mixture O2 + Ar grazing incidence small-angle X-ray scattering simultaneously with activity. occurrence oxidation induces sintering directly correlated to reaction rate. is...
Surface x-ray diffraction has been employed to elucidate the surface structure of $(011)\ensuremath{-}(2\ifmmode\times\else\texttimes\fi{}1)$ termination rutile ${\mathrm{TiO}}_{2}$. The data are inconsistent with previously proposed structures. Instead, an entirely unanticipated geometry emerges from determination, which is terminated by zigzag rows twofold coordinated oxygen atoms asymmetrically bonded fivefold titanium atoms. energetic stability this demonstrated ab initio total energy...
Elucidating the structure of interface between natural (reduced) anatase TiO2 (101) and water is an essential step toward understanding associated photoassisted splitting mechanism. Here we present surface X-ray diffraction results for room temperature with ultrathin bulk water, which explain by reference to density functional theory calculations. We find that both interfaces contain a 25:75 mixture molecular H2O terminal OH bound titanium atoms along bridging species in contact layer. This...
Surface x-ray diffraction has been used to determine the quantitative structure of (101) termination anatase $\mathrm{Ti}{\mathrm{O}}_{2}$. The atomic displacements from bulk-terminated are significantly different those previously calculated with density functional theory (DFT) methods discrepancies for Ti in $[10\overline{1}]$ direction up $0.3\phantom{\rule{0.16em}{0ex}}\AA{}$. DFT calculations carried out as part current paper provide a much better agreement through improved accuracy and...
In gold nanoparticle colloids produced by the pulsed laser ablation in liquid method, surface oxidation can be controlled adjusting bromide coverage when synthesized halide saline solutions.
Photoelectron spectroscopy and scanning tunneling microscopy have been used to investigate how the oxidation state of Ce in CeO2−x(111) ultrathin films is influenced by presence Pd nanoparticles. induces an increase concentration Ce3+ cations, which interpreted as charge transfer from on basis DFT+U calculations. Charge Ce4+ found be energetically favorable even for individual adatoms. These results implications our understanding redox behavior ceria-based model catalyst systems.
Surface x-ray diffraction has been employed to elucidate the surface structure of $\mathrm{Ti}{\mathrm{O}}_{2}(110)(1\ifmmode\times\else\texttimes\fi{}1)$. The atomic coordinates emerging from this study are in excellent agreement with those derived other recent quantitative determinations surface. Most importantly, debate over relaxation bridging oxygen resolved. In a previous study, it was concluded that atom relaxes toward bulk by...
The surface work function (WF) and substrate temperature dependence of the NaCl thin-film growth on Ag(001) have been studied by noncontact atomic force microscopy Kelvin probe microscopy. In sub-monolayer range, film is composed large crystalline islands, which decrease in density increase size with increasing during deposition. Each island a base 2 monolayers (ML) thick (for T > 343 K), collects impinging molecules that form ad-islands top. (KPFM) measurements show reduction silver WF no...
Electron bombardment from a filament as well voltage pulses scanning tunnelling microscope tip have been employed to modify the surface of TiO2(110). Individual H atoms are selectively desorbed with electrical +3 V tip, whilst leaving oxygen vacancies intact. This allows us distinguish between and hydroxyl groups, which similar appearance in microscopy images. then vacancy-promoted dissociation water O2 be followed microscope. Electrical +5 +10 induce local TiO2(110)1 × 2 reconstructions...
Low-energy electron-diffraction and surface x-ray diffraction data acquired from ${\text{TiO}}_{2}(110)(1\ifmmode\times\else\texttimes\fi{}1)$ are reanalyzed to confirm the integrity of previously reported optimized geometries. This work is performed in response ab initio density-functional theory calculations that suggest atomic displacements determined low-energy measurements may be compromised by limited number atom positions. Performing structural optimizations as a function depth into...
Nanocrystals are often described as interesting materials for the design of low-cost optoelectronic devices, especially in infrared range. However, driving reaching absorption generally contain heavy metals (Pb and Hg) with a high toxicity. An alternative strategy to achieve transition is use doped semiconductors presenting intraband or plasmonic short-, mid-, long-wave infrared. This may offer more flexibility regarding range possible candidate materials. In particular, significant progress...
Soft X-ray photoelectron spectroscopy (SXPS) and absorption near-edge structure (XANES) have been combined with low-energy electron diffraction (LEED) to examine the growth of titanium dioxide thin films on Ni(110). Depending initial coverage, formation two different is observed, a quasi-hexagonal phase film rutile (110) rods. Spectroscopy (SXPS XANES) results indicate that all consist fully oxidized titanium. Furthermore, reactivity higher coverage phase, consisting partly TiO2(110), was...
HgTe nanocrystals are currently the most promising colloidal material for infrared detection, combining broadly tunable absorption and photoconductive properties. Current syntheses lead to a limited amount of rely on highly toxic water-soluble form Hg. Here, we explore possibility using Hg thiolate as source demonstrate that latter can be formed in situ from liquid The developed protocol allows large masses (7 g) concentrated (100 g/L) syntheses, which is step forward transfer this toward...
We have used scanning tunneling microscopy (STM), noncontact atomic force (NC-AFM), low energy electron diffraction (LEED), and ab initio calculations to study adsorbates resulting from exposure of rutile TiO2(110)1 × 1 methyl phosphonic acid (CH3P═O(OH)2). At exposures, appear on the 5-fold coordinated Ti (Ti5c) rows. As coverage approaches 0.5 ML, STM images show an ordered 2 overlayer consistent with LEED. propose that is deprotonated phosphonate bridging across two adjacent Ti5c atoms in...
Here, we show that the stoichiometry and, consequently, chemical activity toward hydroxylation of MgO(100) films grown by reactive deposition on Ag(100) strongly depend O2 partial pressure during film growth. Oxygen-deficient undergo dramatic relative oxygen uptake either exposure to a water vapor or aging in vacuum for sufficiently long time. Conversely, stoichiometric monolayer MgO islands, photoemission analysis O 1s level and scanning tunneling microscopy images are consistent with...
We present a study of the growth and reactivity ultra-thin films TiO 2 grown on W(100).Three approaches to film are investigated, each resulting in that show order low-energy diffraction (LEED) low level non-stoichiometry X-ray photoelectron spectroscopy (XPS).H O is used as probe films, with changes Ti 2p 1s core levels being monitored by XPS.Evidence for dissociation H (110) surface adduced.These results discussed reference related studies native (110).
Intraband and plasmonic transitions have appeared over the last years as an interesting tool to achieve optical absorption in mid-infrared. Tuning doping magnitude has become a major challenge not only tune spectrum but also properties such dark current or time response. Here, we investigate case of self-doped HgSe colloidal quantum dots (CQDs). At present, tuning relies on band bending induced by dipole design at nanoparticle surface. With surface gating approach, it is difficult conciliate...
Surface stress and energy are basic quantities in the Gibbsian formulation of thermodynamic description surfaces which is central formation long-term behavior materials at nanoscale. However, their size dependence a puzzling issue. It even unclear whether they decrease or increase with decreasing particle size. In addition, for given metal, estimates often span over an order magnitude, far apart from bulk data, which, absence any explicit size-dependence rule, escapes understanding. Here, we...
Surface X-ray diffraction has been employed to quantitatively determine the geometric structure of an X-ray-induced superhydrophilic rutile-TiO2(110)(1 × 1) surface. A scatterer, assumed be oxygen, is found at a distance 1.90 ± 0.02 Å above five-fold-coordinated surface Ti atom, indicating hydroxylation. Two more oxygen atoms, situated further from substrate, are also included achieve optimal agreement between experimental and simulated data. It concluded that these latter scatterers water...