Publications de Olivier Christian Bräm

Ultrafast Broadband Fluorescence Up-conversion Study of the Electronic Relaxation of Metalloporphyrins

Majed Chergui, Olivier Christian Bräm, Andrea Cannizzo

We present a systematic study of the ultrafast fluorescence with broadband detection and similar to 110 fs resolution of 5,10,15,20-tetraphenylporphin (TPP) and 2,3,7,8,12,13,17,18-oc-taethylporphin (OEP), with open 3d-shell metals. We also revisit the cas ...

AMER CHEMICAL SOC2019

Dual Luminescence, Interligand Decay, and Nonradiative Electronic Relaxation of Cyclometalated Iridium Complexes in Solution

Majed Chergui, Olivier Christian Bräm, Andrea Cannizzo, Mahsa Silatani, Enrico Pomarico

Femtosecond broadband photoluminescence studies are presented for Ir(ppy)(3) (Ir1), Ir(ppy)(2)(pic) (Ir2), Ir(ppy)(2)(bpy)(PF6) (Ir3), Ir(ppz)(3) (Ir4), and Ir(ppz)(2)dipy (Ir5) (where ppy = 2-phenylpyridine, pic = picolinate, bpy = 2,2'-bipyridine, ppz = ...

American Chemical Society2016

A cascade through spin states in the ultrafast haem relaxation of met-myoglobin

Majed Chergui, Olivier Christian Bräm, Frank van Mourik, Cristina Consani, Gerald Auböck

We report on a study of the early relaxation processes of met-Myoglobin in aqueous solution, using a combination of ultrafast broadband fluorescence detection and transient absorption with a broad UV-visible continuum probe at different pump energies. Reco ...

American Institute of Physics2014

Ultrafast Relaxation Dynamics of Osmium-Polypyridine Complexes in Solution

Mohammad Khaja Nazeeruddin, Majed Chergui, Olivier Christian Bräm, Andrea Cannizzo

We present steady-state absorption and emission spectroscopy and femtosecond broadband photoluminescence up-conversion spectroscopy studies of the electronic relaxation of Os(dmbp)(3) (Os1) and Os(bpy)(2)(dpp) (Os2) in ethanol, where dmbp is 4,4'-dimethyl- ...

American Chemical Society2013

Ultrafast Solvent-Assisted Electronic Level Crossing in 1-Naphthol

Majed Chergui, Olivier Christian Bräm, Mirabelle Prémont-Schwarz

Wiley-Blackwell2013

Solvent Induced Luminescence Quenching: Static and Time-Resolved X-Ray Absorption Spectroscopy of a Copper(I) Phenanthroline Complex

Majed Chergui, Olivier Christian Bräm, Ursula Röthlisberger, Ivano Tavernelli, Frederico Alves Lima, Marco Eli Reinhard, Mercedes Hannelore Rittmann-Frank, Thomas James Penfold, Lotta Susanne Karlsson, Jochen Rittmann, Gloria Capano

We present a static and picosecond X-ray absorption study at the Cu K-edge of bis(2,9-dimethyl-1,10-phenanthroline)copper(I) (Cu(dmp)(2); dmp = 2,9-dimethyl-1,10-phenanthroline) dissolved in acetonitrile and dichloromethane. The steady-state photolumi ...

Amer Chemical Soc2013

Real-time observation of the charge transfer to solvent dynamics

Majed Chergui, Olivier Christian Bräm, Andrea Cannizzo

Intermolecular electron-transfer reactions have a crucial role in biology, solution chemistry and electrochemistry. The first step of such reactions is the expulsion of the electron to the solvent, whose mechanism is determined by the structure and dynamic ...

Nature Publishing Group2013

Ultraviolet transient absorption, transient grating and photon echo studies of aqueous tryptophan

Majed Chergui, Olivier Christian Bräm, Andrea Cannizzo, Ahmad Ajdar Zadeh Oskouei, Cristina Consani

We compare UV transient grating (TG) experiments of aqueous tryptophan with transient absorption (TA) and fluorescence up-conversion measurements. The TG and TA signals show a bi-exponential rise with sub-ps and ps time constants, which are consistent with ...

Elsevier2013

Polychromatic femtosecond fluorescence studies of metal-polypyridine complexes in solution

Majed Chergui, Olivier Christian Bräm, Andrea Cannizzo, Ahmed Maher Fahmy El-Zohry

Femtosecond-resolved broadband fluorescence studies are reported for M(bpy)(3) (M = Fe, Ru), RuN3 and RuN719 complexes in solution. We investigated the pump wavelength dependence of the fluorescence of aqueous Fe(bpy)(3) and the solvent and li ...

2012

Energy transfer and relaxation mechanisms in Cytochrome c

Majed Chergui, Olivier Christian Bräm, Frank van Mourik, Andrea Cannizzo, Cristina Consani

Using broadband UV-vis femtosecond transient absorption and fluorescence up-conversion, we investigate the interaction between the haem moiety of ferric and ferrous Horse heart Cytochrome c and its single Tryptophan (Trp) residue and the energy dissipation ...

Elsevier2012

Ultrafast fluorescence studies of dye sensitized solar cells

Majed Chergui, Olivier Christian Bräm, Andrea Cannizzo

Time-resolved fluorescence spectra from the RuN719 dye exhibit very short lifetimes (

2012

A femtosecond fluorescence study of vibrational relaxation and cooling dynamics of UV dyes

Majed Chergui, Olivier Christian Bräm, Andrea Cannizzo, Thomas James Penfold

We present a femtosecond broad-band fluorescence up-conversion study of the vibrational relaxation dynamics of two UV chromophores, 2,5-diphenyloxazole (PPO) and para-terphenyl (pTP), pumped with a large excess of vibrational energy (>2000 cm(-1)). The ban ...

2012

Ultrafast Excited-State Dynamics of Rhenium(I) Photosensitizers [Re(Cl)(CO)(3)(N,N)] and [Re(imidazole)(CO)(3)(N,N)](+): Diimine Effects

Majed Chergui, Olivier Christian Bräm, Amal El Nahhas, Andrea Cannizzo, Cristina Consani

Femto- to picosecond excited-state dynamics of the complexes Re(L)(CO)(3)(N,N) (N,N = bpy, phen, 4,7-dimethyl-phen (dmp); L = Cl, n = 0; L = imidazole, n = 1+) were investigated using fluorescence up-conversion, transient absorption in the 650-285 nm ...

2011

Ultrafast Visible and Ultraviolet Fluorescence Studies of Molecular and Biological Sytems in Solution

Olivier Christian Bräm

A wide variety of physical and chemical processes at the molecular level, as charge or energy transfer, solvation, electronic as well as vibrational relaxation, is at the origin of the biological functionality of proteins. The work reported in this thesis ...

EPFL2011

Femtosecond UV Studies of the Electronic Relaxation Processes in Cytochrome c

Majed Chergui, Olivier Christian Bräm, Andrea Cannizzo, Cristina Consani

We report on an experimental study with UV and visible ultrafast time-gated emission and transient absorption of the early photodynamics of horse heart Cytochrome c in both ferric and ferrous redox states. A clear separation in time and energy of tryptopha ...

2011

Ultrafast (Bio)physical and (Bio)chemical Dynamics

Majed Chergui, Olivier Christian Bräm, Frank van Mourik, Amal El Nahhas, Andrea Cannizzo, Ahmad Ajdar Zadeh Oskouei, Renske Marjan van der Veen, Cristina Consani, Gerald Auböck

We give an overview of our recent work on ultrafast dynamics of chemical (organic dyes, metal-complexes, colloidal quantum dots), and biological (retinal and haem proteins) systems in the liquid phase, studied with a variety of ultrafast optical techniques ...

2011

Coherent ultrafast torsional motion and isomerization of a biomimetic dipolar photoswitch

Stefan Haacke, Majed Chergui, Olivier Christian Bräm, Andrea Cannizzo

Femtosecond fluorescence up-conversion, UV-Vis and IR transient absorption spectroscopy are used to study the photo-isomerization dynamics of a new type of zwitterionic photoswitch based on a N-alkylated indanylidene pyrroline Schiff base framework (ZW-NAI ...

Royal Society of Chemistry2010

Broadband femtosecond fluorescence up-conversion and photon echo experiments in the UV

Majed Chergui, Olivier Christian Bräm, Frank van Mourik, Andrea Cannizzo, Ahmad Ajdar Zadeh Oskouei

The fs-time-resolved study of a small UV dye in different solvents with fluorescence up-conversion and photon-echo techniques in the UV range provides new insight in cooling relaxation and solvation dynamics of non-polar molecules in polar solvents. ...

Springer-Verlag New York, Ms Ingrid Cunningham, 175 Fifth Ave, New York, Ny 10010 Usa2009

Photon echo peak shift experiments in the UV: p-terphenyl in different solvents

Majed Chergui, Olivier Christian Bräm, Frank van Mourik, Andrea Cannizzo, Ahmad Ajdar Zadeh Oskouei

We present a new photon echo set-up operating in the UV range and our 1st results of photon echo peak shift (PEPS) expts. of a small non-polar dye mol., p-terphenyl (pTP), in 3 different solvents: EtOH, MeOH, and 2-propanol. The expts. show the feasibility ...

2008

Ultrafast UV photon echo peak shift and fluorescence up conversion studies of non-polar solvation dynamics

Majed Chergui, Olivier Christian Bräm, Frank van Mourik, Andrea Cannizzo, Ahmad Ajdar Zadeh Oskouei

The authors present photon echo peak shift and femtosecond fluorescence up-conversion studies of nonpolar solvation dynamics of a simple nonpolar dye p-terphenyl in EtOH and cyclohexane, using excitation in the UV range at 290 nm. The UV fluorescence up-co ...

2008