| 1. |
|
|
| 2. |
|
|
| 3. |
- Chaignon, Frederique, et al.
(author)
-
Photoinduced electron transfer in ruthenium(II) trisbipyridine complexes connected to a naphthalenebisimide via an oligo(phenyleneethynylene) spacer
- 2009
-
In: New Journal of Chemistry. - : Royal Society of Chemistry (RSC). - 1144-0546 .- 1369-9261. ; 33:2, s. 408-416
-
Journal article (peer-reviewed)abstract
- The preparation and the characterization of three new dyads composed of a ruthenium trisbipyridine complex linked to a naphthalene bisimide electron acceptor via a phenyleneethynylene spacer of different length (one or two units) are reported. The dyads also differ by the anchoring position of the spacer on the bipyridine, which is appended either at the 4-position or the 5-position. Cyclic voltammetry and the UV-Vis absorption spectroscopy suggested that the spacer linked at the 5-position ensures a longer pi-conjugation length but the electron transfer rates indicate a lower electronic coupling, than in 4-position. Photoinduced emission yields indicate a significant quenching of the MLCT excited-state of the ruthenium complex in these dyads. Except for the dyad linked in 5 position with one phenyleneethynylene unit, the transient absorption spectroscopy of all the other dyads evidences that the MLCT excited-state decays almost exclusively by electron transfer to form the charge-separated state Ru-III-NBI-. This state could not be observed, presumably because the subsequent recombination to the ground state was much faster than its formation. In the dyad linked in 5 position with only one phenyleneethynylene unit, at room temperature, the (MLCT)-M-3* state is in equilibrium with the (NBI)-N-3* state, and it also decays via electron transfer. The notable feature of these dyads is first the occurrence of a relatively long-range electron transfer reaction via a bis(phenylethynylene) linking unit anchored at the 5 position. Secondly, we show within these series of compounds that subtle variations in the structure of the dyads (length of the spacer and anchoring position on bipy) have a strong impact on the rates and in the mechanism of decay of the (MLCT)-M-3* state. The photophysical properties of the dyads can be explained in terms of energy proximity of different excited states and magnitude of the electronic coupling according to the anchoring position.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Chavillon, Benoit, et al.
(author)
-
P-Type Nitrogen-Doped ZnO Nanoparticles Stable under Ambient Conditions
- 2012
-
In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 134:1, s. 464-470
-
Journal article (peer-reviewed)abstract
- Zinc oxide is considered as a very promising material for optoelectronics. However, to date, the difficulty in producing stable p-type ZnO is a bottleneck, which hinders the advent of ZnO-based devices. In that context, nitrogen-doped zinc oxide receives much attention. However, numerous reviews report the controversial character of p-type conductivity in N-doped ZnO, and recent theoretical contributions explain that N-doping alone cannot lead, to p-typeness in Zn-rich ZnO. We report here that the ammonolysis at low temperature or ZnO2 yields pure wurtzite-type N-doped ZnO nanoparticles with an extraordinarily large amount of Zn vacancies (up to 20%). Electrochemical and transient spectroscopy studies demonstrate that these Zn-poor nanoparticles exhibit a p-type conductivity that is stable over more than 2 years under ambient conditions.
|
|
| 7. |
- Farré, Yoann, et al.
(author)
-
A Comparative Investigation of the Role of the Anchoring Group on Perylene Monoimide Dyes in NiO-Based Dye-Sensitized Solar Cells
- 2020
-
In: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 13:7, s. 1844-1855
-
Journal article (peer-reviewed)abstract
- The anchoring group of a sensitizer may strongly affect the overall properties and stability of the resulting dye-sensitized solar cells (DSSCs) and dye-sensitized photoelectrosynthetic solar cells (DSPECs). The properties of seven perylene monoimide (PMI) dyes have been comprehensively studied for their immobilization on nanocrystalline NiO film. The PMI dyes differ only by the nature of the anchoring group, which are: carboxylic acid (PMI-CO2H), phosphonic acid (PMI-PO3H2), acetyl acetone (PMI-acac), pyridine (PMI-Py), aniline (PMI-NH2), hydroxyquinoline (PMI-HQ), and dipicolinic acid (PMI-DPA). The dyes are investigated by cyclic voltammetry and spectroelectrochemistry and modeled by TD-DFT quantum chemical calculations. The mode of binding of these anchoring groups is investigated by infrared spectroscopy and the stability of the binding to NiO surface is studied by desorption experiments in acidic and basic media. The phosphonic acid group is found to offer the strongest binding to the NiO surface in terms of stability and dye loading. Finally, a photophysical study by ultrafast transient absorption spectroscopy shows that all dyes inject a hole in NiO with rate constants on a subpicosecond timescale and display similar charge recombination kinetics. The photovoltaic properties of the dyes show that PMI-HQ and PMI-acac give the highest photovoltaic performances, owing to a lower degree of aggregation on the surface.
|
|
| 8. |
- Farré, Yoann, et al.
(author)
-
Second Generation of DiketopyrrolopyrroleDyes for NiO based Dye-Sensitized Solar Cells
- 2016
-
In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 120:15, s. 7923-7940
-
Journal article (peer-reviewed)abstract
- In this study, four new diketopyrrolopyrrole (DPP) sensitizers, with a dicarboxylated triphenylamine anchoring group for attachment to NiO, were prepared and their electronic absorption, emission and electrochemical properties were recorded. The nature of the electronic excited-states was also modeled with TD-DFT quantum chemistry calculations. The photovoltaic performances of these new dyes were characterized in NiO-based dye-sensitized solar cells (DSCs) with the classical iodide/triiodide and cobaltII/III-polypyridine electrolytes, in which they proved to be quite active. Laser spectroscopy on dye/NiO/electrolyte films gave evidence for ultrafast hole injection into NiO (0.2-10 ps time scales). For the dyes with an appended naphtalenediimide (NDI) acceptor unit, ultrafast electron transfer to the NDI dramatically prolonged the lifetime of the charge separated state NiO(+)/dye-, from the ps time scale to an average lifetime ≈ 0.25 ms, which is among the slowest charge recombinations ever reported for dye/NiO systems. This allowed for efficient regeneration by CoIIIpolypyridine electrolytes, which translated into much improved PV-performance compared to the DPP dyes without appended NDI. Overall, these results underscore the suitability of DPP as sensitizers for NiO-based photoelectrochemical devices for photovoltaic and photocatalysis.
|
|
| 9. |
- Favereau, Ludovic, et al.
(author)
-
A Molecular Tetrad That Generates a High-Energy Charge-Separated State by Mimicking the Photosynthetic Z-Scheme
- 2016
-
In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 138:11, s. 3752-3760
-
Journal article (peer-reviewed)abstract
- The oxygenic photosynthesis of green plants, green algae, and cyanobacteria is the major provider of energy rich compounds in the biosphere. The so-called "Z-scheme" is at the heart of this "engine of life". Two photosystems (photo system I and II) work in series to build up a higher redox ability than each photosystem alone can provide, which is necessary to drive water oxidation into oxygen and NADP(+) reduction into NADPH with visible light. Here we show a mimic of the Z-scheme with a molecular tetrad. The "tetrad Bodipy-NDI-TAPD-Ru is composed of two different dyes-4,4-difluoro-1,3,5,7-tetramethyl-2,6-diethy1-4-bora-3a,4a-diaza-s-indacene (Bodipy) and a Ru-II(bipyridine), (Ru) derivative-which are connected to a naphthalene diimide (NDI) electron acceptor and tetraalkylphenyldiamine (TAPD) playing the role of electron donor. A strong laser pulse excitation of visible light where the two dye molecules (Ru and Bodipy) absorb with equal probability leads to the cooperative formation of a highly energetic charge-separated state composed of an oxidized Bodipy and a reduced Ru. The latter state cannot be reached by one single photon absorption. The energy of the final charge-separated state (oxidized Bodipy/reduced Ru) in the tetrad lies higher than that in the reference dyads (Bodipy-NDI and TAPD-Ru), leading to the energy efficiency of the tetrad being 47% of the sum of the photon threshold energies. Its lifetime was increased by several orders of magnitude compared to that in the reference dyads Bodipy-NDI and TAPD-Ru, as it passes from about 3 ns in each dyad to 850 ns in the tetrad. The overall quantum yield formation of this extended charge-separated state is estimated to be 24%. Our proof-of-concept result demonstrates the capability to translate a crucial photosynthetic energy conversion principle into man-made molecular systems for solar fuel formation, to obtain products of higher energy content than those produced by a single photon absorption.
|
|
| 10. |
- Favereau, Ludovic, et al.
(author)
-
Tris-bipyridine based dinuclear ruthenium(II)--osmium(III) complex dyads grafted onto TiO2 nanoparticles for mimicking the artificial photosynthetic Z-scheme
- 2017
-
In: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 19:6, s. 4778-4786
-
Journal article (peer-reviewed)abstract
- The Z-Scheme function within molecular systems has been rarely reported for solar energy conversion although it offers the possibility to achieve higher efficiency than single photon absorber photosystems due to the use of a wider range of visible light. In this study, we synthesized and investigated the electrochemical and spectroscopic properties of two new dyads based on ruthenium and osmium tris-bipyridine complexes covalently linked via a butane bridge to explore their ability to realize the Z-scheme function once immobilized on TiO2. These dyads can be grafted onto a nanocrystalline TiO2 film via the osmium complex bearing two dicarboxylic acid bipyridine ligands, while the ruthenium complex contains either two unsubstituted bipyridine ancillary ligands (RuH-Os) or two (4,4'-bis-trifluoro-methyl-bipyridine) ancillary ligands (RuCF3-Os). Transient absorption spectroscopy studies of the Ru(II)-Os(III) dyads with femtosecond and nanosecond lasers were conducted both in solution and on TiO2. For both conditions, the photophysical studies revealed that the MLCT excited state of the ruthenium complex is strongly quenched and predominantly decays by energy transfer to the LMCT of the adjacent Os(III) complex, in spite of the high driving force for electron transfer. This unexpected result, which is in sharp contrast to previously reported Ru(II)-Os(III) dyads, precluded us to achieve the expected Z-scheme function. However, the above results may be a guide for designing new artificial molecular systems reproducing the complex function of a Z-scheme with molecular systems grafted onto a TiO2 mesoporous film.
|
|
