Publications by Malte Oppermann

Asymmetric conformation of the high-spin state of iron(II)-tris(2,2-bipyridine): Time-resolved x-ray absorption and ultraviolet circular dichroism

We analyze the structures of the low-spin (LS) ground state and the high-spin (HS) lowest excited state of the iron-(II)-tris bipyridine complex ([Fe(bpy)3]2+) using density functional theory PBE methods, modeling the solvent interactions with conductor-li ...

2024

Disentangling Thermal from Electronic Contributions in the Spectral Response of Photoexcited Perovskite Materials

Majed Chergui, Thomas Charles Henry Rossi, Lijie Wang, Malte Oppermann

Disentangling electronic and thermal effects in photoexcited perovskite materials is crucial for photovoltaic and optoelectronic applications but remains a challenge due to their intertwined nature in both the time and energy domains. In this study, we emp ...

Amer Chemical Soc2024

Early bird or night owl? Controlling the ultrafast photodynamics of triphenylamine substituted 2,2′:6′,2′′-terpyridine

Majed Chergui, Etienne Christophe Socie, Malte Oppermann, Oliviero Cannelli

Controlling the ultrafast photodynamics of metal-free organic molecules has great potential for technological applications. In this work, we use solvent polarity and viscosity as "external knobs" to govern the photodynamics of an electron-donating derivati ...

Royal Soc Chemistry2024

Element- and enantiomer-selective visualization of molecular motion in real-time

Majed Chergui, Malte Oppermann, Jérémy Raymond Jean Maurice Rouxel

Ultrafast optical-domain spectroscopies allow to monitor in real time the motion of nuclei in molecules. Achieving element-selectivity had to await the advent of time resolved X-ray spectroscopy, which is now commonly carried at X-ray free electron lasers. ...

Nature Portfolio2023

Giant two-photon absorption of anatase TiO2 in Au/TiO2 core-shell nanoparticles

Majed Chergui, Lijie Wang, Malte Oppermann

We report on deep-to-near-UV transient absorption spectra of core-shell Au/SiO2 and Au/TiO2 nanoparticles (NPs) excited at the surface plasmon resonance of the Au core, and of UV-excited bare anatase TiO2 NPs. The bleaching of the first excitonic transitio ...

CHINESE LASER PRESS2023

Data for "Ultrafast deep-ultraviolet study of photoexcited aqueous Ferrioxalate"

Majed Chergui, Malte Oppermann, Michele Puppin, Christoph Bostedt, Hui-Yuan Chen

Data repository for the following publication: A. Duque-Prata*, H.-Y. Chen*, L. Müller, M. Oppermann, M. Puppin, C. Serpa, C. Bostedt and M. Chergui, “Ultrafast deep-ultraviolet study of photoexcited aqueous Ferrioxalate”, submitted to ChemPhotoCh ...

Zenodo2023

Exciton decay mechanism in DNA single strands: back-electron transfer and ultrafast base motions

Majed Chergui, Malte Oppermann, Benjamin Bauer, Rahul Sharma

The photochemistry of DNA systems is characterized by the ultraviolet (UV) absorption of pi-stacked nucleobases, resulting in exciton states delocalized over several bases. As their relaxation sensitively depends on local stacking conformations, disentangl ...

ROYAL SOC CHEMISTRY2022

Hard X-ray helical dichroism of disordered molecular media

Majed Chergui, Jérôme Lacour, Christian David, Giulia Fulvia Mancini, Malte Oppermann, Dominik Kinschel, Oliviero Cannelli, Camila Bacellar Cases Da Silveira

Chirality is a structural property of molecules lacking mirror symmetry that has strong implications in diverse fields, ranging from life sciences to materials science. Chirality-sensitive spectroscopic methods, such as circular dichroism, exhibit weak sig ...

Nature Publishing Group2022

Chiral control of spin-crossover dynamics in Fe (II) complexes

Majed Chergui, Jérôme Lacour, Malte Oppermann

Iron-based spin-crossover complexes hold tremendous promise as multifunctional switches in molecular devices. However, real-world technological applications require the excited high-spin state to be kinetically stable-a feature that has been achieved only ...

NATURE PORTFOLIO2022

Slow Charge Carrier Relaxation in Gold Nanoparticles

Majed Chergui, Lars-Hendrik Mewes, Thomas Charles Henry Rossi, Lijie Wang, Malte Oppermann, Benjamin Bauer, Davood Zare

We report on ultrafast transient absorption (TA) studies of surface plasmon-excited similar to 25 nm-diameter Au nanoparticles in solution, monitoring the response of the surface plasmon resonance in the visible region (1.7-3.0 eV) and that of the inter- a ...

AMER CHEMICAL SOC2020

Exciton dynamics in DNA oligomers studied by broadband deep-UV transient absorption spectroscopy

Majed Chergui, Malte Oppermann, Benjamin Bauer

We report broadband transient absorption measurements of adenine strands in the deep-UV (250-370 nm). By varying the strand length we resolve the interplay between inter-base stacking and exciton formation and dynamics in DNA oligomers. ...

E D P SCIENCES2019

Cooling dynamics of electrons in MAPbBr(3) probed in the deep-UV

Majed Chergui, Peter Chen, Thomas Charles Henry Rossi, Lijie Wang, Malte Oppermann, Yu-Hsien Chiang

Transient absorption in the Visible and in the deep-UV is performed on MAPbBr(3) thin films with 3.1 eV pump excitation. The UV probe can access higher order transitions in the material exploring different high-symmetry points of the Brillouin zone. Uncorr ...

E D P SCIENCES2019

Ultrafast broadband circular dichroism in the deep ultraviolet

Majed Chergui, Jérôme Lacour, Thomas Charles Henry Rossi, Malte Oppermann, Benjamin Bauer

The measurement of chirality and its temporal evolution are crucial for the understanding of a large range of biological functions and chemical reactions. Steady-state circular dichroism (CD) is a standard analytical tool for measuring chirality in chemist ...

OPTICAL SOC AMER2019

Broad-Band Ultraviolet CD Spectroscopy of Ultrafast Peptide Backbone Conformational Dynamics

Majed Chergui, Malte Oppermann, Benjamin Bauer

The far-UV spectral window widely used for the conformational analysis of biomolecules is not easily covered with broad-band lasers. This has made it difficult to use circular dichroism (CD) spectroscopy to directly follow fast structure changes. By combin ...

AMER CHEMICAL SOC2019

Phonon-Driven Selective Modulation of Exciton Oscillator Strengths in Anatase TiO2Nanoparticles

Majed Chergui, Gerald Auböck, Thomas Charles Henry Rossi, Tania Palmieri, Edoardo Baldini, Enrico Pomarico, Malte Oppermann

The way nuclear motion affects electronic responses has become a very hot topic in materials science. Coherent acoustic phonons can dynamically modify optical, magnetic, and mechanical properties at ultrasonic frequencies, with promising applications as se ...

American Chemical Society (ACS)2018

The LOUVRE Laboratory: State-of-the-Art Ultrafast Ultraviolet Spectroscopies for Molecular and Materials Science

Majed Chergui, Frank van Mourik, Natalia Nagornova, Lars-Hendrik Mewes, Thomas Charles Henry Rossi, Tania Palmieri, Edoardo Baldini, Malte Oppermann, Benjamin Bauer, Aurelio Oriana

We describe the facilities for ultraviolet studies in the femtosecond to nanosecond time domain. These facilities consist of: i) a set-up for deep-ultraviolet spectroscopy in the 260–380 nm range in both pump and probe pulses for transient absorption/refle ...

2017

Design and implementation of an optimal laser pulse front tilting scheme for ultrafast electron diffraction in reflection geometry with high temporal resolution

Fabrizio Carbone, Giulia Fulvia Mancini, Francesco Pennacchio, Rajeswari Jayaraman, Malte Oppermann, Giovanni Maria Vanacore

Ultrafast electron diffraction is a powerful technique to investigate out-of-equilibrium atomic dynamics in solids with high temporal resolution. When diffraction is performed in reflection geometry, the main limitation is the mismatch in group velocity be ...

Amer Inst Physics2017

Interfacial Electron Injection Probed by a Substrate-Specific Excitonic Signature

Majed Chergui, Gerald Auböck, Thomas Charles Henry Rossi, Tania Palmieri, Edoardo Baldini, Enrico Pomarico, Malte Oppermann

Ultrafast interfacial electron transfer in sensitized solar cells has mostly been probed by visible-to-terahertz radiation, which is sensitive to the free carriers in the conduction band of the semiconductor substrate. Here, we demonstrate the use of deep- ...

2017