Martine Bujoli-Doeuff

Smart Heterostructures for Tailoring the Optical Properties of Photochromic Hybrid Organic–Inorganic Polyoxometalates

A new concept of photoresponsive composites has been elaborated by intimately connecting a Photochromic Phase (PP), (H(2)DABCO)(2)(HDMA)(0.5)Na(0.75)(H(3)O)(0.75)[Mo(8)O(27)]·3H(2)O (1), with a second hybrid organic-inorganic molybdate material, (H(2)DABCO)(HDABCO)[Fe(OH)(6)Mo(6)O(18)]·4H(2)O (2) acting as an Oxidation Catalytic Phase (OCP) toward the former once photoexcited. The association of both the PP and the OCP in the composite drastically improves the bleaching process of the PP alone because of efficient electronic transfers through the OCP-PP interface without affecting significantly its photoinduced color change characteristic. Two OCP-PP composites with different PP weight percents have been obtained by associating 1 with 2. The optical properties of these composites before and after UV irradiation have been investigated by Diffuse Reflectance Spectroscopy, and the strong impact of the OCP on the fading kinetics of the PP has been clearly highlighted.

Copper borate as a photocathode in p-type dye-sensitized solar cells

p-Type dye-sensitized solar cells (p-DSSCs) have recently become a major research focus because coupling with n-type DSSCs yields highly efficient tandem DSSCs. Indeed many delafossite-like compounds appear as promising candidates for p-DSSCs due to their deep valence band position and high hole mobility. In this paper, the synthesis of CuBO2 was attempted by a facile sol–gel methodology. Then, the as-obtained particles were used to prepare photocathodes for p-DSSCs with DPP-NDI dye as sensitizer and tris(4,4′-di-tert-butyl-2,2′-bipyridine)cobalt(III/II) as redox mediator. Due to the deeper valence band position compared with classical NiO photocathode, the “CuBO2” based p-DSSC presents an open-circuit photovoltage (Voc) of 453 mV, which is 150 mV higher than that of NiO in the same conditions. The results show that “CuBO2” is a potential alternative for NiO in p-DSSCs.

Structure of Zn(O3PC2H4CO2H)·0.5C6H5NH2 and XANES–EXAFS study of the intercalation of amines into Zn(O3PR)·H2O zinc alkylphosphonates

On the basis of XANES–EXAFS experiments, neither the dehydration nor the subsequent n-alkylamine intercalation in Zn(O3PCH3)·H2O appears to be topotactic. On the contrary, the whole process consists of breaking Zn—O bonds present in the hydrated material, so that no bridging oxygen remains in the inorganic sheet. This hypothesis is supported by the structural determination of an aniline intercalate: Zn(O3PC2H4CO2H)·0.5C6H5NH2[orthorhombic, space group Pbcn, a= 29.880(6)A, b= 8.526 (2)A, c= 14.720 (3)A, V= 3750.3(8)A3, Z= 16, R= 0.043 and Rw= 0.047; 2063 observed reflections, I > 2σ(I)]. For steric reasons, only half of the zinc atoms are coordinated to aniline; the second half of the metal atoms that are not bound to the amine retain the environment present in the initial anhydrous phase.

CuO nanomaterials for p-type dye-sensitized solar cells

In p-type dye-sensitized solar cells (p-DSSCs), NiO is the most commonly used p-type semiconductor. Nevertheless, because of the drawbacks of NiO, much effort has been made to search for suitable substitutes. Herein, three different morphologies of CuO nanomaterials were used to prepare photocathodes for p-DSSCs, which have a deeper valence band and a higher dielectric constant compared to that of NiO. We observe that CuO is unstable in the presence of iodide/triiodide electrolyte, while cobalt complexes with bipyridine ligands are more suitable redox shuttles. We also note that the average transport time in CuO is shorter than that in NiO. Finally, the deep absorbance of CuO in the visible range indicates that suitable sensitizers for the CuO p-DSSC must exhibit high extinction coefficient and absorption bands located in the lower energy part of the solar spectrum (>600 nm) to be exploitable. In this case such CuO based photocathodes represent valuable systems to exploit the near-infrared (NIR) region.

Modulation of Defects in Semiconductors by Facile and Controllable Reduction: The Case of p-type CuCrO2 Nanoparticles

Optical and electrical characteristics of solid materials are well-known to be intimately related to the presence of intrinsic or extrinsic defects. Hence, the control of defects in semiconductors is of great importance to achieve specific properties, for example, transparency and conductivity. Herein, a facile and controllable reduction method for modulating the defects is proposed and used for the case of p-type delafossite CuCrO2 nanoparticles. The optical absorption in the infrared region of the CuCrO2 material can then be fine-tuned via the continuous reduction of nonstoichiometric Cu(II), naturally stabilized in small amounts. This reduction modifies the concentration of positive charge carriers in the material, and thus the conductive and reflective properties, as well as the flat band potential. Indeed, this controllable reduction methodology provides a novel strategy to modulate the (opto-) electronic characteristics of semiconductors.

New Hybrid Layered Molybdates Based on 2/∞[MonO3n+1]2– Units (n = 7, 9) with Systematic Organic–Inorganic Interfaces

Two new hybrid organic-inorganic molybdates based on layered (2/∞)[Mo(n)O(3n+1)](2-) blocks and organoammonium cations (+)(Me(x)H(3-x)N)(CH(2))(6)(NH(3-x)Me(x))(+) (x = 0-1), namely, (H(3)N(CH(2))(6)NH(3))[Mo(7)O(22)]·H(2)O (1) and (MeH(2)N(CH(2))(6)NH(2)Me)[Mo(9)O(28)] (2), have been synthesized under hydrothermal conditions. The (2/∞)[Mo(9)O(28)](2-) unit in 2 is an unprecedented member of the (2/∞)[Mo(n)O(3n+1)](2-) family with the n value extended to 9. The structural filiation between the (2/∞)[Mo(n)O(3n+1)](2-) (n = 5, 7, 9) blocks is well established, and their structural similarity with the (2/∞)[MoO(3)] slabs in α-MoO(3) is also discussed. Single-crystal X-ray analyses show that the (2/∞)[Mo(n)O(3n+1)](2-) layers in 1 and 2 are pillared in the three-dimensional networks by the organic cations with a similar connection at the organic-inorganic interface. In addition, a correlation between the topology of the (2/∞)[Mo(n)O(3n+1)](2-) blocks in 1 and 2 and the overall sizes of the associated organic cations is pointed out. Finally, the efficiency of Fourier transform Raman spectroscopy to easily discriminate the different (2/∞)[Mo(n)O(3n+1)](2-) blocks (n = 5, 7, 9) in hybrid organic-inorganic layered molybdate materials is clearly evidenced.

HOW THE ORGANIC MOIETY DRIVES THE COORDINATION CHEMISTRY OF METAL PHOSPHONATES : THE FIRST ENANTIOMERICALLY PURE ZINC PHOSPHONATE

The first enantiomerically pure metallophosphonate, (R)-Zn[O3PCH2P(O)(CH3)(C6H5)]·H2O has been prepared. The layered arrangement in this compound is drastically different from that observed in the racemic series; this observation gives clear evidence of the critical role played by the organic moiety that fully drives the coordination chemistry of phosphonic acids with transition metals.

Synthesis and structure of phases containing [Ni3P3S12]3− crown-shaped trimers

The exfoliation process of one-dimensional KNiPS4 showed that the breaking of 1/∞[NiPS4]− chains in polar solvent was followed by the formation of cyclic [Ni3P3S12]3− trianions. From DMF–KNiPS4 solutions, metathesis experiments were successfully carried out, but, up to now, K+ had only been exchanged by bigger isotropic organic cations such as PPh4+, (CH3)4N+ and (C2H5)4N+. After recrystallization, each metathesis compound presents the cyclic [Ni3P3S12]3− trianion. An exchange by anisotropic cations is possible by adding a cryptand molecule that fits the size of K+. Following this procedure, three new nickel thiophosphate complexes have been synthesized: [Ni3P3S12][K-(222-cryptand)]3 (I), [Ni3P3S12][K(222-cryptand)]2[C9N1H22] (II) and [Ni3P3S12][CH3(CH2)11N(CH3)3]3 (III). The structures of I and II have been fully determined from single crystal X-ray diffraction analysis. They show the occurrence of the [Ni3P3S12]3− trimer within the solid. I and II crystallize in the P212121 space group. 31P solid state NMR experiments hint at the presence of polyanions in III, maybe trianionic in nature.

Dehydration/amine intercalation in Zn(O3PR)–H2O phosphonates: the missing link, X-ray structure of Zn(O3PCH3)

Abstract The hydrothermal synthesis of colorless crystals of Zn(O3PCH3) was achieved using a solution of zinc nitrate and methylphosphonic acid (1:1) in water, in the presence of thiourea. The structure was determined by single crystal X-ray diffraction [monoclinic, space group P21/c (No. 14), a=8.7226(9) A, b=5.2156(7) A, c=10.847(1) A, V=389.48(9) A3, Z=2]. From this result, the mechanism of the structure modification taking place during the dehydration of Zn(O3PR)–H2O phosphonates was clearly demonstrated.

Investigation of the Structure of New Gallium Phosphonate Based Hybrid Materials by 31P, 71Ga, and 1H Solid-State NMR

Modern high-resolution solid-state NMR is a powerful tool for probing the structure of phosphonate-based hybrid materials, in the organic as well as in the inorganic region. This is illustrated in the case of a series of new gallium phosphon