0000000000266351
AUTHOR
Frédéric Laquai
showing 21 related works from this author
Effect of Charge Transfer in Magnetic-Plasmonic Au@MOx (M = Mn, Fe) Heterodimers on the Kinetics of Nanocrystal Formation
2015
Heteronanoparticles represent a new class of nanomaterials exhibiting multifunctional and collective properties, which could find applications in medical imaging and therapy, catalysis, photovoltaics, and electronics. This present work demonstrates the intrinsic heteroepitaxial linkage in heterodimer nanoparticles to enable interaction of the individual components across their interface. It revealed distinct differences between Au@MnO and Au@Fe3O4 regarding the synthetic procedure and growth kinetics, as well as the properties to be altered by the variation of the electronic structure of the metal oxides. The chemically related metal oxides differ concerning their band gap; while MnO is a M…
Porphyrin amino acids-amide coupling, redox and photophysical properties of bis(porphyrin) amides.
2013
New trans-AB2C meso-substituted porphyrin amino acid esters with meso-substituents of tunable electron withdrawing power (B = mesityl, 4-C6H4F, 4-C6H4CF3, C6F5) were prepared as free amines 3a-3d, as N-acetylated derivatives Ac-3a-Ac-3d and corresponding zinc(II) complexes Zn-Ac-3a-Zn-Ac-3d. Several amide-linked bis(porphyrins) with a tunable electron density at each porphyrin site were obtained from the amino porphyrin precursors by condensation reactions (4a-4d) and mono- and bis(zinc(II)) complexes Zn(2)-4d and Zn(1)Zn(2)-4d were prepared. The electronic interaction between individual porphyrin units in bis(porphyrins) 4 is probed by electrochemical experiments (CV, EPR), electronic abso…
A Heteroleptic Push-Pull Substituted Iron(II) Bis(tridentate) Complex with Low-Energy Charge-Transfer States
2014
A heteroleptic iron(II) complex [Fe(dcpp)(ddpd)](2+) with a strongly electron-withdrawing ligand (dcpp, 2,6-bis(2-carboxypyridyl)pyridine) and a strongly electron-donating tridentate tripyridine ligand (ddpd, N,N'-dimethyl-N,N'-dipyridine-2-yl-pyridine-2,6-diamine) is reported. Both ligands form six-membered chelate rings with the iron center, inducing a strong ligand field. This results in a high-energy, high-spin state ((5) T2 , (t2g )(4) (eg *)(2) ) and a low-spin ground state ((1) A1 , (t2g )(6) (eg *)(0) ). The intermediate triplet spin state ((3) T1 , (t2g )(5) (eg *)(1) ) is suggested to be between these states on the basis of the rapid dynamics after photoexcitation. The low-energy …
Aminoferrocene and Ferrocene Amino Acid as Electron Donors in Modular Porphyrin–Ferrocene and Porphyrin–Ferrocene–Porphyrin Conjugates
2014
New amide-linked porphyrin–ferrocene conjugates [M(PAr)–Fc] were prepared from aminoferrocene and a carboxy-substituted meso-tetraaryl-porphyrin [M = 2H, Zn; Ar = mesityl (Mes), C6F5: 3a, 3e, Zn-3a, Zn-3e]. A further porphyrin building block was attached to the second cyclopentadienyl ring of the ferrocene moiety to give the metallopeptides M(PMes)–Fc–M(PAr) (M = 2H, Zn; Ar = C6H5, 4-C6H4F: 6b, 6c, Zn-6b, Zn-6c). The effects of the Ar substituents, the porphyrin central atom M and the presence of the second porphyrin at the ferrocene hinge on the excited-state dynamics was studied by optical absorption spectroscopy, electrochemistry, steady-state emission, time-resolved fluorescence measure…
Plasmon-enhanced photocurrent in quasi-solid-state dye-sensitized solar cells by the inclusion of gold/silica core–shell nanoparticles in a TiO2 phot…
2013
Direct evidence of the effects of the localized surface plasmon resonance (LSPR) of gold nanoparticles (Au NPs) in TiO2 photoanodes on the performance enhancement in quasi-solid-state dye-sensitized solar cells (DSCs) is reported by comparing gold/silica core–shell nanoparticles (Au@SiO2 NPs) and hollow silica nanoparticles with the same shell size of the core–shell nanoparticles. The Au nanoparticles were shelled by a thin SiO2 layer to produce the core–shell structure, and the SiO2 hollow spheres were made by dissolving the Au cores of the gold/silica core–shell nanoparticles. Therefore, the size and morphology of the SiO2 hollow spheres were the same as the Au@SiO2 NPs. The energy conver…
Inorganic Janus particles for biomedical applications.
2014
Based on recent developments regarding the synthesis and design of Janus nanoparticles, they have attracted increased scientific interest due to their outstanding properties. There are several combinations of multicomponent hetero-nanostructures including either purely organic or inorganic, as well as composite organic–inorganic compounds. Janus particles are interconnected by solid state interfaces and, therefore, are distinguished by two physically or chemically distinct surfaces. They may be, for instance, hydrophilic on one side and hydrophobic on the other, thus, creating giant amphiphiles revealing the endeavor of self-assembly. Novel optical, electronic, magnetic, and superficial pro…
Synthesis of Functional Block Copolymers Carrying One Poly(p-phenylenevinylene) and One Nonconjugated Block in a Facile One-Pot Procedure
2016
Block copolymers composed of a MEH–PPV block and a nonconjugated functional block (molecular weights between 5 and 90 kg/mol) were synthesized in a facile one-pot procedure via ROMP. This one-pot procedure permits the synthesis of numerous block copolymers with little effort. Amphiphilic block copolymers were obtained via incorporation of oxanorbornene carrying a PEG side chain as well as via postpolymerization modification of a reactive ester carrying norbornene derivative with methoxypoly(ethylene glycol)amine. These amphiphilic block copolymers can be self-assembled into micelles exhibiting different sizes (60–95 nm), morphologies (micelles or fused, caterpillar-like micelles), and optic…
Tuning Reductive and Oxidative Photoinduced Electron Transfer in Amide‐Linked Anthraquinone–Porphyrin–Ferrocene Architectures
2014
Porphyrin amino acids 3a–3h with meso substituents Ar of tunable electron-donating power (Ar = 4-C6H4OnBu, 4-C6H4OMe, 4-C6H4Me, Mes, C6H5, 4-C6H4F, 4-C6H4CF3, C6F5) have been linked at the N terminus to anthraquinone Q as electron acceptor through amide bonds to give Q-PAr dyads 4a–4h. These were conjugated to ferrocene Fc at the C terminus as electron donor to give the acceptor-chromophore-donor Q-PAr-Fc triads 6a–6h. To further modify the energies of the electronically excited and charge-separated states, the triads 6a–6h were metallated with zinc(II) to give the corresponding Q-(Zn)PAr-Fc triads Zn-6a–Zn-6h. The Q-PAr1 dyad (Ar1 = C6H5) was further extended with a second porphyrin PAr2 (…
Ferroelastic Fingerprints in Methylammonium Lead Iodide Perovskite
2016
Methylammonium lead iodide (MAPbI3) perovskite shows an outstanding performance in photovoltaic devices. However, certain material properties, especially the possible ferroic behavior, remain unclear. We observed distinct nanoscale periodic domains in the piezoresponse of MAPbI3(Cl) grains. The structure and the orientation of these striped domains indicate ferroelasticity as their origin. By correlating vertical and lateral piezoresponse force microscopy experiments performed at different sample orientations with X-ray diffraction, the preferred domain orientation is suggested to be the a1–a2-phase. The observation of these ferroelastic fingerprints appears to strongly depend on the film t…
Multifunctional two-photon active silica-coated Au@MnO Janus particles for selective dual functionalization and imaging.
2014
Monodisperse multifunctional and nontoxic Au@MnO Janus particles with different sizes and morphologies were prepared by a seed-mediated nucleation and growth technique with precise control over domain sizes, surface functionalization, and dye labeling. The metal oxide domain could be coated selectively with a thin silica layer, leaving the metal domain untouched. In particular, size and morphology of the individual (metal and metal oxide) domains could be controlled by adjustment of the synthetic parameters. The SiO2 coating of the oxide domain allows biomolecule conjugation (e.g., antibodies, proteins) in a single step for converting the photoluminescent and superparamagnetic Janus nanopar…
Excited State Tuning of Bis(tridentate) Ruthenium(II) Polypyridine Chromophores by Push-Pull Effects and Bite Angle Optimization: A Comprehensive Exp…
2013
The synergy of push-pull substitution and enlarged ligand bite angles has been used in functionalized heteroleptic bis(tridentate) polypyridine complexes of ruthenium(II) to shift the (1) MLCT absorption and the (3) MLCT emission to lower energy, enhance the emission quantum yield, and to prolong the (3) MLCT excited-state lifetime. In these complexes, that is, [Ru(ddpd)(EtOOC-tpy)][PF6 ]2 , [Ru(ddpd-NH2 )(EtOOC-tpy)][PF6 ]2 , [Ru(ddpd){(MeOOC)3 -tpy}][PF6 ]2 , and [Ru(ddpd-NH2 ){(EtOOC)3 -tpy}][PF6 ]2 the combination of the electron-accepting 2,2';6',2''-terpyridine (tpy) ligand equipped with one or three COOR substituents with the electron-donating N,N'-dimethyl-N,N'-dipyridin-2-ylpyridin…
Strong donor–acceptor couplings in a special pair-antenna model
2010
A special pair model composed of two cofacial zinc porphyrins (acceptor) linked to a free base (donor) acts as an energy transfer dyad. Despite the absence of conjugation, ππ*/charge transfer excited states and ultrafast energy transfer (∼5 ps) are noted.
Excitation Energy Transfer in Organic Materials: From Fundamentals to Optoelectronic Devices
2009
In this review, we discuss investigations of electronic excitation energy transfer in conjugated organic materials at the bulk and single molecule level and applications of energy transfer in fluorescent and phosphorescent organic light emitting devices. A brief overview of common descriptions of energy transfer mechanisms is given followed by a discussion of some basic photophysics of conjugated materials including the generation of excited states and their subsequent decay through various channels. In particular, various examples of bimolecular excited state annihilation processes are presented. Energy transfer studies at the single molecule level provide a new tool to study electronic co…
CCDC 930312: Experimental Crystal Structure Determination
2013
Related Article: Aaron Breivogel, Michael Meister, Christoph Förster, Frédéric Laquai, Katja Heinze|2013|Chem.-Eur.J.|19|13745|doi:10.1002/chem.201302231
CCDC 1016554: Experimental Crystal Structure Determination
2014
Related Article: Andreas K. C. Mengel, Christoph Förster, Aaron Breivogel, Katharina Mack, Julian R. Ochsmann, Frédéric Laquai, Vadim Ksenofontov, Katja Heinze|2015|Chem.-Eur.J.|21|704|doi:10.1002/chem.201404955
CCDC 930313: Experimental Crystal Structure Determination
2013
Related Article: Aaron Breivogel, Michael Meister, Christoph Förster, Frédéric Laquai, Katja Heinze|2013|Chem.-Eur.J.|19|13745|doi:10.1002/chem.201302231
CCDC 1016552: Experimental Crystal Structure Determination
2014
Related Article: Andreas K. C. Mengel, Christoph Förster, Aaron Breivogel, Katharina Mack, Julian R. Ochsmann, Frédéric Laquai, Vadim Ksenofontov, Katja Heinze|2015|Chem.-Eur.J.|21|704|doi:10.1002/chem.201404955
CCDC 930311: Experimental Crystal Structure Determination
2013
Related Article: Aaron Breivogel, Michael Meister, Christoph Förster, Frédéric Laquai, Katja Heinze|2013|Chem.-Eur.J.|19|13745|doi:10.1002/chem.201302231
CCDC 930310: Experimental Crystal Structure Determination
2013
Related Article: Aaron Breivogel, Michael Meister, Christoph Förster, Frédéric Laquai, Katja Heinze|2013|Chem.-Eur.J.|19|13745|doi:10.1002/chem.201302231
CCDC 1016553: Experimental Crystal Structure Determination
2014
Related Article: Andreas K. C. Mengel, Christoph Förster, Aaron Breivogel, Katharina Mack, Julian R. Ochsmann, Frédéric Laquai, Vadim Ksenofontov, Katja Heinze|2015|Chem.-Eur.J.|21|704|doi:10.1002/chem.201404955
CCDC 1016551: Experimental Crystal Structure Determination
2014
Related Article: Andreas K. C. Mengel, Christoph Förster, Aaron Breivogel, Katharina Mack, Julian R. Ochsmann, Frédéric Laquai, Vadim Ksenofontov, Katja Heinze|2015|Chem.-Eur.J.|21|704|doi:10.1002/chem.201404955