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SSCI-VIDE+CDURABLE+BPU:SMR; International audience; A major challenge in the field of up-conversion nanomaterials (UC) is the search for improved up-conversion luminescence. Compared to conventional luminophores, the quantum yields of lanthanide-doped nanoparticles are extremely low (typically

SSCI-VIDE+CARE:CDFA+SGA:FDA:CGU:SMR; International audience; Titanium dioxide (TiO2) is one of the most promising photocatalysts due to its low cost, non-toxicity, chemical stability and high catalytic activity. One limitation of this material is that it mainly absorbs in the UV region of the solar spectrum which represents only ~3.5% energy of total solar light. The catalytic efficiency of this material is further reduced by a relatively easy recombination of the photogenerated electron/hole. To overcome these intrinsic limitations, the current research focuses mainly on decreasing the band gap of titania by introducing some defects. This usually increases the wavelength range for the absorption but also decreases the activity for titania, thus resulting in no net gain. To improve the photocatalytic activity of TiO2, we are currently focusing on its nanocomposites with low bandgap metal chalcogenide semiconductors prepared mainly by the bottom-up approach [1,2]. This communication deals with precursor-mediated synthesis of binary and ternary coinage metal selenide nanoparticles under mild conditions. It will discuss different reaction conditions leading to different reactivities of starting reagents, affording either molecular complexes or inorganic nanoparticles directly. The preparation of nanocomposites of these metal selenide nanoparticles with commercial TiO2 (P25), their characterization by a range of physico-chemical techniques and photocatalytic activity for the degradation of formic acid under UV-visible radiation will be presented.References:[1] (a)Precursor-mediated synthesis of Cu2-xSe nanoparticles and its composites with TiO2 for improved photocatalysis, S. Gahlot, E. Jeanneau, F. Dappozze,C. Guillard, S. Mishra, Dalton Trans. 2018, 47, 8897.; (b) A facile molecular precursor-based synthesis of Ag2Se nanoparticles and its composites with TiO2 for enhanced photocatalytic activity,S. Mishra, D. Du, E. Jeanneau, F. Dappozze,C. Guillard, J. Zhang, S. Daniele, Chem. Asian J. 2016, 11, 1658.[2] Metal-organic derivatives with fluorinated ligands as precursors for inorganic nanomaterials, S. Mishra, S. Daniele, Chem. Rev. 2015, 115, 8379.

SSCI-VIDE+CARE:CDFA+SGA:FDA:CGU:SMR; International audience; The reactions between copper(II) trifluoroacetate and selenoethers (R2Se) of different steric bulk were investigated in a variety of solvents in relation with their use as precursors for the selenium-containing nanomaterials. Different reaction conditions led to different reactivities and afforded either molecular complexes or different phases of copper selenide nanoparticles. The factors governing the divergent reactivity and the structures of the precursors will be discussed. The reactions leading to in situ formation of the Cu2-xSe nanoparticles were then extended in the presence of commercial TiO2 (P25) to prepare copper selenide-titania nanocomposites with different metal ratios, which were thoroughly characterized using a range of physico-chemical techniques (PXRD, UV-Vis, BET, XPS and TEM) and studied as catalysts for the photodegradation of formic acid under UV-visible radiation. Preliminary results shows an improved photocatalytic activity of Cu2-xSe-TiO2 nanocomposites as compared to P25. A possible mechanism to explain the synergistic effect between Cu2-xSe and TiO2 components for the aforesaid photocatalytic efficiency will be presented.

International @ SURFACES+FCA; International audience; None

International @ CDFA+SMR:SDA; International audience; Elaboration of lanthanide-doped NaLnF4 upconverting (UC) nanocrystals (which convert near infra-red radiation to shorter wavelength UV-visible region) via novel heterometallic Na-Ln (Ln = Y, La-Lu) trifluoroacetate complexes as single source precursors was reported for the first time by our group [1]. A study on the decomposition behaviour of the Na-Gd precursor shows that the hexagonal phase of the NaGdF4 matrix, which is many fold more efficient for the upconversion process, is easily obtained at much lower temperature than over the extensively used homometallic Ln(TFA)3(H2O)3. [2] Moreover, these molecular precursors have multiple advantages such as being anhydrous (presence of water molecules is detrimental for the up-converting properties) and containing glyme ligand, which acts as a capping-reagent during decomposition to provide controlled size and stable dispersion of nanocrystals in organic solvents. In this presentation we will discuss the synthesis and complete characterization of TiO2@NaGdF4:Yb3+,Tm3+ core/shell nano-composites. UC nanomaterials absorb extremely weakly and within a very narrow spectral window, making very high illumination intensities often necessary. We will then present further functionalization of upconverting nanopaticles using a set of dye molecules as antenna to enhance the overall upconversion due to increased absorptivity and overall broadening of the absorption spectrum of the upconverter [3]. NIR-driven photocatalytic activity of the above obtained nano-structures will be addressed.

International @ MATERIAUX+SMR:SDA; International audience; Elaboration of lanthanide-doped NaLnF4 upconverting (UC) nanocrystals (which convert near infra-red radiation to shorter wavelength UV-visible region) via novel heterometallic Na-Ln (Ln = Y, La-Lu) trifluoroacetate complexes as single source precursors was reported for the first time by our group [1]. A study on the decomposition behaviour of the Na-Gd precursor shows that the hexagonal phase of the NaGdF4 matrix, which is many fold more efficient for the upconversion process, is easily obtained at much lower temperature than over the extensively used homometallic Ln(TFA)3(H2O)3. [2] Moreover, these molecular precursors have multiple advantages such as being anhydrous (presence of water molecules is detrimental for the up-converting properties) and containing glyme ligand, which acts as a capping-reagent during decomposition to provide controlled size and stable dispersion of nanocrystals in organic solvents.

International @ MATERIAUX+CLA:JUC:ADM; International audience; Polynuclear hybrid Au(I) compounds exhibit a very large domain of applications such as electronic devices, contrast agents, sensors or photocatalysts. All these applications are related to the ability of gold(I) to form aurophilic interactions which gives luminescent materials [1]. Among gold species, thiolate gold(I) compounds are an important class of materials due to the high affinity of gold for sulfur that can generate molecular complexes, extended polymers, stabilized gold nanoparticles or SAM. Thus in nanoscience, thiolate gold(I) polymers are a key step in the Brust synthesis of functionalized gold nanoparticles. However relatively little is known about the relationship between the structure of the Au(I)-SR intermediate and the formation of the nanoparticles. Thus the luminescence of thiolate gold nanoclusters, with gold core diameter less than 2 nm, are highly dependent of the structure and the arrangement of Au(I)-thiolate motifs at the surface [2]. So to understand the luminescence and the formation of gold clusters, we will present the synthesis and the first structure resolutions by powder X-Ray diffraction of series of [Au(I)-SR]n coordination polymers. We will demonstrate that depending on the substituent (R = Ph, PhCOOH, PhNH2, PhtBu, naphthalene, C11H23, C2H4Ph…) different structures are obtained (lamellar, helicoidal or cyclic) with luminescent properties governed by Au-Au distances [3]. Reduction of these crystalline coordination polymers to form functionalized gold nanoparticles will also be reported and will contribute to a better control of gold nanoparticles preparation.

SSCI-VIDE+CDURABLE+SMR:BPU; International audience; A major challenge in the field of upconverting (UC)nanomaterials is to enhance upconversion luminescence. In comparison to conventional luminophores, quantum yields of lanthanide-doped UC nanoparticles are extremely low (typically less than 1%) and, in general, about an order of magnitude lower than those of corresponding UC bulk materials. It is well-known that –OH defects in the nanocrystals are the primary cause of upconversion quenching. We have employed designed anhydrous molecular precursors as a synthetic strategy to enhance upconversion efficiency in Yb and Tm co-doped MM'F nanocrystals (M = Li, Na; M' = Y, Gd). The bottom-up synthesis not only facilitates a better control over the composition, structure and morphology of the nanomaterials, but anhydrous conditions also minimize –OH functionality on the surface of the upconverting NPs. A detailed up-conversion studies reveal that the uniform nanoparticles obtained from these anhydrous single source precursors had i) superior up-conversion intensity than the UC materials produced from the hydrated inorganic salts, and ii) a comparable efficiency with bulk materials of the same composition. The applications of thesenanomaterials in the field of photocatalysis will be described.

SSCI-VIDE+CDURABLE+BPU:SMR; International audience; A major challenge in the field of up-conversion nanomaterials (UC) is the search for improved up-conversion luminescence. Compared to conventional luminophores, the quantum yields of lanthanide-doped nanoparticles are extremely low (typically