A5051281537- Quantum Dots Synthesis And Properties
- Perovskite Materials and Applications
- ZnO doping and properties
- Advanced Chemical Physics Studies
- Electron and X-Ray Spectroscopy Techniques
- Chalcogenide Semiconductor Thin Films
- X-ray Spectroscopy and Fluorescence Analysis
- Solid-state spectroscopy and crystallography
- Molecular Junctions and Nanostructures
- Iron oxide chemistry and applications
- Photochemistry and Electron Transfer Studies
- Heavy Metal Exposure and Toxicity
- Catalytic C–H Functionalization Methods
- Ga2O3 and related materials
- CO2 Reduction Techniques and Catalysts
- Magnetic and transport properties of perovskites and related materials
- Gold and Silver Nanoparticles Synthesis and Applications
- Luminescence Properties of Advanced Materials
- Radical Photochemical Reactions
- Photoreceptor and optogenetics research
- Integrated Circuits and Semiconductor Failure Analysis
- Mercury impact and mitigation studies
- Advanced Electron Microscopy Techniques and Applications
- Transition Metal Oxide Nanomaterials
- Advanced Memory and Neural Computing
Helmholtz-Zentrum Berlin für Materialien und Energie
2021-2024
École Polytechnique Fédérale de Lausanne
2014-2024
Micron (United States)
2024
University of Illinois Urbana-Champaign
2021
MSPCA-Angell
1991
Consulintel (Spain)
1991
The measurement of chirality and its temporal evolution are crucial for the understanding a large range biological functions chemical reactions.Steady-state circular dichroism (CD) is standard analytical tool measuring in chemistry biology.Nevertheless, push into ultrafast time domain deep-ultraviolet has remained challenge, with only some isolated reports subnanosecond CD.Here, we present broadband time-resolved CD spectrometer deep ultraviolet (UV) spectral femtosecond resolution.The setup...
We report on an element-selective study of the fate charge carriers in photoexcited inorganic CsPbBr3 and CsPb(ClBr)3 perovskite nanocrystals toluene solutions using time-resolved X-ray absorption spectroscopy with 80 ps time resolution. Probing Br K-edge, Pb L3-edge, Cs L2-edge, we find that holes valence band are localized at atoms, forming small polarons, while electrons appear as delocalized conduction band. No signature either electronic or structural changes is observed L2-edge. The...
The development of next-generation perovskite-based optoelectronic devices relies critically on the understanding interaction between charge carriers and polar lattice in out-of-equilibrium conditions. While it has become increasingly evident for CsPbBr3 perovskites that Pb–Br framework flexibility plays a key role their light-activated functionality, corresponding local structural rearrangement not yet been unambiguously identified. In this work, we demonstrate photoinduced changes system...
Disentangling electronic and thermal effects in photoexcited perovskite materials is crucial for photovoltaic optoelectronic applications but remains a challenge due to their intertwined nature both the time energy domains. In this study, we employed temperature-dependent variable-angle spectroscopic ellipsometry, density functional theory calculations, broadband transient absorption spectroscopy spanning visible mid-to-deep-ultraviolet (UV) ranges on MAPbBr
Photoassisted catalysis using Ni complexes is an emerging field for cross-coupling reactions in organic synthesis. However, the mechanism by which light enables and enhances reactivity of these often remains elusive. Although optical techniques have been widely used to study ground excited states photocatalysts, they lack specificity interrogate electronic structural changes at specific atoms. Herein, we report metal-specific studies transient L- K-edge X-ray absorption spectroscopy a...
Ferrocene is one of the most common electron donors, and mapping its ligand-field excited states critical to designing donor-acceptor (D-A) molecules with long-lived charge transfer states. Although
Ultrafast interfacial electron transfer in sensitized solar cells has mostly been probed by visible-to-terahertz radiation, which is sensitive to the free carriers conduction band of semiconductor substrate. Here, we demonstrate use deep-ultraviolet continuum pulses probe transfer, detecting a specific excitonic transition both N719-sensitized anatase TiO2 and wurtzite ZnO nanoparticles. Our results are compared those obtained on bare nanoparticles upon above-gap excitation. We show that...
Anatase TiO2 (a-TiO2) exhibits a strong X-ray absorption linear dichroism with the incidence angle in pre-edge, XANES and EXAFS at titanium K-edge. In pre-edge region behaviour of A1-A3 B peaks, originating from 1s-3d transitions, is due to $p$-orbital polarization $p-d$ orbital mixing. An unambiguous assignment peak transitions made monoelectronic approximation support ab initio finite difference method calculations spherical tensor analysis quantitative agreement experiment. It found that...
The structure and defect concentration of colloidal solutions ZnO nanoparticles, synthesized by a sol–gel procedure (SG-NP), as well commercially available nanoparticles (SA-NP) are investigated UV–vis absorption spectroscopy, transmission electron microscopy (TEM), X-ray spectroscopy (XAS) diffraction (XRD). XRD patterns, in agreement with the TEM images, reveal that SG-NPs more ellipsoidal than SA-NPs. XAS presence both zinc oxygen vacancies. latter is independent NP size. This not case...
Summary Three hundred forty-seven cases of lead poisoning in small companion animals were reviewed. The yearly prevalence and overall incidence rates examined for the 10 years before after enactment strict federal regulations pertaining to content paint products. Biographical data, clinical signs, laboratory results analyzed 6 types affected (ie, dogs, cats, birds, rabbits, a chinchilla, raccoon). Clinical findings these then compared with other studies intoxication.
The evolution of charge carriers in photoexcited room temperature ZnO nanoparticles solution is investigated using ultrafast ultraviolet photoluminescence spectroscopy, Zn K-edge absorption and ab initio molecular dynamics (MD) simulations. excited at 4.66 eV, well above the band edge, shows that electron cooling conduction exciton formation occur <500 fs, excellent agreement with theoretical predictions. x-ray measurements, obtained upon excitation close to edge 3.49 are sensitive...
Ferrocene is one of the most common electron donors, and mapping its ligand-field excited states critical to designing donor-acceptor (D-A) molecules with long-lived charge transfer states. Although 3(d-d) are commonly invoked in photophysics ferrocene complexes, mention high-spin 5(d-d) state scarce. Here, we provide clear evidence formation a bimetallic D-A molecule, ferrocenyl cobaltocenium hexafluorophosphate ([FcCc]PF6). Femtosecond optical transient absorption (OTA) spectroscopy...
We review our recent results on the implementation of picosecond (ps) X-ray absorption spectroscopy to probe electronic and geometric structure centres formed by photoexcitation solar materials such as TiO2 polymorphs inorganic Cs-based perovskites. The show electron localization at Ti defects in anatase rutile small hole polaron formation valence band CsPbBr3, all within 80 ps. This method is promising for study ultrafast time scales processes, especially with advent Swiss Free Electron...
X-ray absorption linear dichroism of rutile TiO 2 at the Ti K -edge provides information about electronic states involved in pre-edge transitions. Here, with high energy resolution is analyzed combination ab initio finite difference method calculations and spherical tensor analysis. It an assignment three peaks beyond octahedral crystal field splitting approximation estimates spatial extension corresponding final states. then discussed for first time (XAS) pentacoordinated titanium atoms due...
We report on ultrafast transient absorption (TA) studies of surface plasmon-excited ∼25 nm-diameter Au nanoparticles in solution, monitoring the response plasmon resonance visible region (1.7–3.0 eV) and that inter- intraband transitions deep UV (3.4–4.5 eV). The former reflects lattice heating by electron–phonon energy transfer, while latter monitors charge carriers, is, excess holes electrons, respectively, below above Fermi level. Although steady-state spectrum is featureless, TA spectra...
Three hundred forty-seven cases of lead poisoning in small animals, diagnosed after 1976, were reviewed. The types treatments used and their outcomes analyzed. Changes blood concentrations following various treatments, as well the sources exposure, also geographic origins traced, demographic factors studied to determine possible correlates that might explain regional distribution cases.
Understanding the electronic structure and dynamics of semiconducting nanomaterials at atomic level is crucial for realization optimization devices in solar energy, catalysis, optoelectronic applications. We report here on use ultrafast X-ray linear dichroism spectroscopy to monitor carrier epitaxial ZnO nanorods after band gap photoexcitation. By rigorously subtracting out thermal contributions conducting ab initio calculations, we reveal an overall depletion absorption cross sections...
Ferrocene is one of the most common electron donors, and mapping its ligand-field excited states critical to designing donor-acceptor (D-A) molecules with long-lived charge transfer states. Although 3(d-d) are commonly invoked in photophysics ferrocene complexes, mention high-spin 5(d-d) state scarce. Here, we provide clear evidence formation a bimetallic D-A molecule, ferrocenyl cobaltocenium hexafluorophosphate ([FcCc]PF6). Femtosecond optical transient absorption (OTA) spectroscopy...
Ultrafast X-ray spectroscopy has been revolutionized in recent years due to the advent of fourth-generation facilities. In solid-state materials, core excitons determine energy and line shape absorption features core-level spectroscopies such as spectroscopy. The screening is an inherent many-body process that can reveal insight into charge-transfer excitations electronic correlations. Under non-equilibrium conditions after photoexcitation, however, core-exciton still not fully understood....
We describe the facilities for ultraviolet studies in femtosecond to nanosecond time domain. These consist of: i) a set-up deep-ultraviolet spectroscopy 260–380 nm range both pump and probe pulses transient absorption/reflectivity or two-dimensional studies; ii) ultrafast fluorescence measurements with detection down 300 nm. The capabilities of these set-ups are demonstrated by examples on molecular systems, biosystems, nanoparticles solid materials.
The development of next generation perovskite-based optoelectronic devices relies critically on the understanding interaction between charge carriers and polar lattice in out-of-equilibrium conditions. While it has become increasingly evident for CsPbBr3 perovskites that Pb-Br framework flexibility plays a key role their light-activated functionality, corresponding local structural rearrangement not yet been unambiguously identified. In this work, we demonstrate photoinduced changes system...
Understanding the electronic structure and dynamics of semiconducting nanomaterials at atomic level is crucial for realization optimization devices in solar energy, catalysis, optoelectronic applications. We report here on use ultrafast X-ray linear dichroism spectroscopy to unravel carrier epitaxial ZnO nanorods after band-gap photoexcitation. By rigorously subtracting out thermal contributions conducting ab initio calculations, we reveal an overall depletion absorption cross sections...
Photo-assisted catalysis using Ni complexes is an emerging field for cross-coupling reactions in organic synthesis. However, the mechanism by which light enables and enhances reactivity of these often remains elusive. Although optical techniques have been widely used to study ground excited states photocatalysts, they lack specificity interrogate electronic structural changes at specific atoms. Herein we report metal-specific studies static transient L- K-edge X-ray absorption spectroscopy a...