Latest Publications

DOI: 10.1021/acsami.9b18034

American Chemical Society

The family of organic-inorganic hybrid perovskite (OIHPs) materials is one of the most promising for very high efficiency photovoltaic solar cells application. In the present work, the effect of a series of self-assembled monolayers placed at the TiO2-perovskite junction, on the functioning of triple cation perovskite solar cells has been investigated. We show that employing 4-chlorobenzoic acid leads to the marked boosting of the solar cells performances. The starting pristine cell had a 20.3% power conversion efficiency (PCE) and the chemical engineering permitted to reach a PCE up to 21.35%. Our experimental study completed by density functional theory (DFT) calculations and modelling show that this improvement is due to the reduction of interfacial states, to the improvement of the quality of the OIHP material and to the structural continuity between TiO2 and the OIHP. Especially, we demonstrate that the interfacial chemical inter...

DOI: 10.1021/acsomega.9b02819

American Chemical Society

Here, we have studied, with a combined experimental and computational approach, the effect of the crystal environment and aggregation on the electronic properties of Pigment Red 179, which affect both its color and optical energy gap. Spectra acquired in the near-infrared and visible range of energies suggest that this molecule is indeed a “cool” dye, which can be employed as a red pigment that provides effective color coverage to different substrates without contributing to their heating during light irradiation. Spectra acquired on different polymer mixtures at different pigment concentrations (i.e., 2.5–10 wt %) suggest that absorption features depend on chromophoric arrangements promoted by the strong intermolecular π–π interactions. Calculations, performed at the time-dependent density functional theory level, allowed to both attribute the nature of the electronic transitions causing the observed spectra involved and understand...

DOI: 10.1021/acs.jpcc.9b06805

The Journal of Physical Chemistry C 2019

We present a theoretical investigation of the reactivity of both a pristine CeO2 surface and a small Ag cluster adsorbed on a CeO2 surface towards H2, using a periodic spin-polarized hybrid density functional theory approach. The dissociation of H2 and subsequent formation of H2O have been considered in order to highlight the role of the metal structure and its underlying metal oxide support as a potential candidate as a catalyst to the above-mentioned reactions. Structural, energetic, electronic and vibrational properties of all species involved in the different reaction paths considered have been fully characterized. The cluster-oxide surface interface has been found to involve the reduction of up to 3 Ce4+ to Ce3+, by direct electron transfer from the cluster to the oxide. When comparing the reducibility of the Ag-CeO2 and clean CeO2 systems, O vacancy formation has been found to be hindered along the perimeter of...

DOI: 10.1016/j.bmc.2019.05.011

Bioorganic & Medicinal Chemistry

The use of Photodynamic Therapy (PDT) for the treatment of several kinds of cancer as well as bacterial, fungal or viral infections has received increasing attention during the last decade. However, the currently clinically approved photosensitizers (PSs) have several drawbacks, including photobleaching, slow clearance from the organism and poor water solubility. To overcome these shortcomings, much effort has been made in the development of new types of PSs, such as Ru(II) polypyridyl complexes. Nevertheless, most studied Ru(II) polypyridyl complexes have a low absorbance in the spectral therapeutic window. In this work, we show that, by carefully selecting substituents on the polypyridyl complex, it is possible to prepare a complex absorbing at much higher wavelength. Specifically, we report on the synthesis and in-depth experimental and theoretical characterisation of a Ru(II) polypyridyl complex (complex 3) combining a s...

DOI: 10.1002/cptc.201900117

ChemPhotoChem

A tolane‐based molecule, the 4‐fluorophenyl 4‐((4‐(octyloxy)phenyl)ethynyl)‐benzoate (FOEB), was recently reported to show Crystallisation‐Induced Emission (CIE) and Aggregation‐Caused Quenching (ACQ) [Tong et al., J. Phys. Chem. C, 2015, 119, 21875]. In this work, we rely on a combination of tailored computational methods based on molecular dynamics, (TD‐)DFT and QM/QM’ calculations, to investigate the structural and optical properties of FOEB in solution, crystal and aggregate. First, the computation of the Huang‐Rhys factors and the reorganization energies can rationalize the modulation of the emission efficiency observed when changing the solvent polarity. The moderate fluorescence quenching observed in solution is due to the photophysical energy dissipation caused by low‐frequency vibrational modes involving the lateral groups along with motions out of the plane of the molecule. In crystalline environment, due to the packing arrangment, ther...

DOI: 10.1021/acs.jpcc.9b01047 

The Journal of Physical Chemistry

Oxide-carbonate composite electrolytes are complex materials whose peculiar conductivity performances are yet to be fully understood. Stability issues however arise when the carbonate is combined to an oxide such as TiO2, preventing practical fuel cell application of TiO2-based composites. To investigate the origin of such instability, a combined experimental and Density Functional Theory based approach is here presented and applied to the LiKCO3-TiO2 composite, focusing on energetic, electronic and vibrational properties. The origin of the instability of this composite could be traced back to the intrinsic reducible nature of TiO2, with inserted Li being almost fully oxidized and stabilized by reduced Ti atoms at the oxide surface, thus facilitating LixTiO2 phases formation and accumulation close to the interface between the oxide and the carbonate. This demonstrates that although the interface formation is critical for en...

DOI:10.1002/anie.201902456

Angewandte Chemie

Oxide-carbonate composite electrolytes are complex materials whose peculiar conductivity performances are yet to be fully understood. Stability issues however arise when the carbonate is combined to an oxide such as TiO2, preventing practical fuel cell application of TiO2-based composites. To investigate the origin of such instability, a combined experimental and Density Functional Theory based approach is here presented and applied to the LiKCO3-TiO2 composite, focusing on energetic, electronic and vibrational properties. The origin of the instability of this composite could be traced back to the intrinsic reducible nature of TiO2, with inserted Li being almost fully oxidized and stabilized by reduced Ti atoms at the oxide surface, thus facilitating LixTiO2 phases formation and accumulation close to the interface between the oxide and the carbonate. This demonstrates that although the interface formation is critical for enhanced conductivity...

DOI: 10.1039/C8CP07100D

Physical Chemistry Chemical Physics 2019

The excited state dynamics of constrained photochromic benzodithienylethenes were addressed by considering the bridging with polyether chains (from x = 4 to 6 units) at the ortho and meta positions of the aryl group, named DTE-ox and DTE-mx, via time-resolved absorption spectroscopy supported with (TD)-DFT calculations. The photochromic parameters and geometrical structures of these series are discussed. A novel photocyclization pathway via a triplet state, evidenced recently (Hamdi et al., Phys. Chem. Chem. Phys., 2016, 18, 28091–28100), is largely dependent on the length and the position of the polyether chain. For the first time, by comparing the two series, we revealed, for the DTE-ox series, an interconversion not only in the ground state but also between the triplet states of the anti-parallel and parallel open form conformers.

Synthesis

DOI:  10.1055/s-0037-1611673

A copper-catalysed hydroamination reaction of N-allenylsulfonamides with amines has been developed through a rational approach based on mechanistic studies. The reaction is promoted by a simple copper(I) catalyst and proceeds at room temperature with complete regioselectivity and excellent stereoselectivity towards linear (E)- N-(3-aminoprop-1-enyl)sulfonamides. Density Functional Theory (DFT) studies allow interpreting the key role of unsaturated substituents on nitrogen as ancillary coordinating moieties for the copper catalyst.

Journal of Computational Chemistry

DOI: 10.1002/jcc.25800

The ability to locate minima on electronic excited states (ESs) potential energy surfaces (PESs) both in the case of bright and dark states is crucial for a full understanding of photochemical reactions. This task has become a standard practice for small- to medium-sized organic chromophores thanks to the constant developments in the field of computational photochemistry. However, this remains a very challenging effort when it comes to the optimization of ESs of transition metal co

mplexes (TMCs), not only due to the presence of several electronic excited states close in energy, but also due to the complex nature of the excited states involved. In this article, we present a simple yet powerful method to follow an excited state of interest during a structural optimization in the case of TMC, based on the use of a compact hole-particle representation of the electronic transition, namely the natural transition orbitals (NTOs). State t...

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