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A B S T R A C T S FRIDAY, JULY 2 N A N O S E A 2 0 1 0 11H00-11H20 Remarkable self-assembly effect in hybrid TiO2 systems elaborated by chemical design: Applications in cosmetics, ionic selective separation and catalysis. Raed Rahala, Fatima Annania, Stéphane Pellet-Rostaingb, Stéphane Danielea (a Institut de Recherches sur la Catalyse et l‟Environnement de Lyon (IRCELYON), UMR 5256; 2 avenue Albert Einstein; 69626 Villeurbanne cedex, France; b Institut de Chimie Séparative de Marcoule (ICSM), UMR 5257, site de Marcoule, BP 17171, 30207 Bagnol sur Cèze, France). raed_rahal@hotmail.com, fatima.annani@ircelyon.univlyon1.fr, stephane.daniele@ircelyon.univ-lyon1.fr, stephane.pellet-rostaing@cea.fr 1 – Introduction Hybrid oxide (TiO2) nanostructured materials, which combine the properties of inorganic and organic constituents, have a large range of uses in the fields of composite materials, separation, catalysis, electrical and optical devices or in the biomedical area.1 The control of the aforementioned properties of the resulting nanomaterials depends strongly on the control of parameters such as size, shape, crystallinity, phase composition of the oxide nanoparticles, nature of bonding and interface between the organic and the inorganic phases, the nature and the amount of the organic component and finally the degree of dispersion of the nanoobjects. Whereas elaborations of valuable functional inorganic mesostructures from nanostructured TiO2 hybrid particles of controlled size, morphology and phase are well documented in the literature, a chemical process that allows the generation of nanoparticle self-assembly through control over the compositions and the surface chemistries still remains a challenge. 2 – Abstract Recently, we have developed a new aqueous one-pot process for nano-structured (6 nm in size) hybrid Organic/Inorganic TiO2 materials, starting from molecular heteroleptic alkoxides of titanium.2 This method offers the convenience and economical advantages of being environmentally friendly (organic-free solvent). It also appears to be an efficient and reliable method for a precise control of the organic loadings (up to about 20% in weight) and for adjusting the combined Organic/Inorganic properties. Molecules such as para-amino benzoic acid (PABA) were found to be chemisorbed as a carboxylate onto TiO2 nano-particles. Chemical (e.g. pH) and spectroscopic (e.g. FT-IR, Neutron diffusion) data were consistent with strong chemisorption of the amino acid molecules onto the TiO2 nanoparticles surface through bidentate chelate or bridging coordination. Weight losses between 175 and 500 °C of our TiO2/PABA-I to -V samples ranged from about 7 to 21% of organics (TG average weight losses: 6.9, 10.3, 11.7, 14.8, 20.8 %), and each sample exhibited highly reproducible data as a very interesting feature (TG average standard deviation = ± 0.3 %). Other remarkable trends in the physicochemical properties of such hybrid nanomaterials were the formation of different three dimensional superstructures by increasing the surface organic rate. N2-sorption isotherm patterns of highly functionalized nanomaterials demonstrated an extensively interconnected porous network and a so-called “pore-blocking effect”. Preliminary results of solar protection evaluation were obtained with 300-μm thick films by using the same mass of hybrid nanoparticles. The TiO2/PABA-I sample displayed uniform and grain-free films with low intensity of transmitted light. Such a nanomaterial appeared efficient to block out all the UV radiation at sea level, and it also seemed promising for cosmetic applications (lowest amount of organic UV filter). The aggregation effect, that is, for the TiO2/PABA-V sample, led to inhomogeneous films and to an increase in the intensity of transmitted light in the UV-A radiation zone. These results demonstrated that precise control of the organic loading was an important parameter for adjusting the performance of nanohybrid titania for UVA + UVB sunscreen applications.2b 125
A B S T R A C T S FRIDAY, JULY 2 N A N O S E A 2 0 1 0 In an attempt to use NH2– functions as surface sites for further organic reactions, we studied the chemical reactivity of our TiO2/PABA nano-structured material through coupling reactions with DTPA dianhydride in dry DMF. Lanthanum and gadolinium nitrates were chosen in order to check the efficiency of these hybrid nanostructured materials toward the selective separation of lanthanides in acidic aqueous solution (to copy actinide/lanthanide separation). Amounts of lanthanides (La and Gd) in aqueous solutions were determined by ICP-AES spectrometry with a Spectro D (Spectro). Gd3+ and La3+ complexations efficiencies of 50 mg of each TiO2/PABA-DTPA-I, -II and -V nano-materials as a function of pH exhibited that only TiO2/PABA-DTPA-II gave a unique selectivity (SGd/La > 76) towards Gd3+ in the pH range of 2–5. By increasing the organic content using TiO2/PABA-DTPA–V, the maximum capacity increased strongly but the selectivity SGd/La decreased to 12.6 from pH 3. These data showed again that the chemical selforganization in such hybrid nanostructured materials has a remarkable influence on their physicochemical properties.3 Other applications such as support for liquid phase selective oxidation catalysis4 , drinkable water cleaning or as efficient MRI agent will also be addressed in order to demonstrate how control of the surface functionality and hence control of the self-assembly process (formed by strongly interacting nanocrystals) can considerably affect the final mesoscale physicochemical properties. 3 – Conclusion In conclusion, we have described a simple synthetic methodology for hybrid TiO2 nano-materials which successfully formed UV sunscreen additives or ionic recognition devices to enable UVA+UVB solar protection or selective lanthanides separation, respectively. They provide a better understanding in the requirements of self-assembled (-organized) material design for further elaboration of functional nanostructured materials. References 1. See review: (a) C. Sanchez, B. Julian, P. Belleville and M. Popall, J. Mater. Chem., 2005, 15, 3559 ; (b) C. Sanchez, G.J. De A.A. Soler-Illia, F. Ribot and D. Grosso, C.R. Chimie, 2003, 6, 1131. 2. (a) S. Daniele, L.G. Hubert-Pfalzgraf, patent WO 2007/017586 A1. (b) Rahal, S. Daniele, L.G. Hubert-Pfalzgraf, V. Guyot-Férreol, J.F. Tranchant, Eur. J. Inorg. Chem., 2008, 980. 3. R. Rahal, S. Daniele, S. Pellet-Rostaing, M. Lemaire, Chem Lett., 2007, 1364. 4. (a) M. Beyrhouty, S. Daniele, A.B. Sorokin, L.G. Hubert-Pfalzgraf, New J. Chem., 2005, 29, 1245-1248. (b) V. Mendez, V. Caps, S. Daniele, Chem Comm., 2009, 3116-3118. 126
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