Abstract: ZnO is a wide-band-gap semiconductor (3.37 eV) that displays interesting luminescent properties, which include the recent demonstration of ultraviolet lasing from nanowires. These properties have stimulated the search for new synthetic methodologies for well-controlled ZnO nanostructures. Several reports on high-temperature physical or chemical ZnO syntheses have recently been published. The chemical methods appear to be of particular interest since they offer the potential of facile scale-up, and occur at moderate temperatures (100–200 8C). The synthesis is generally carried out in water or alcohols using zinc salts as starting materials in the presence of a base. These methods are convenient and may lead to nanomaterials of controlled morphology. However, the synthesis makes use of ionic species, which may react with the growing oxide and modify the properties of the final material, whether chemical or physical. An alternative method using the organometallic complex [Zn(C2H5)2] (1) as a precursor was reported by Klabunde et al. However, it involves the transformation of 1 into an alkoxide prior to hydrolysis and heat treatment. Complex 1 was also recently used for the synthesis of ZnO following a “high-temperature organometallic method” derived from that originally reported by Bawendi et al. in the presence of ligands, such as tri-n-octyl phosphane oxide (TOPO) and amines. In separate studies, we have evidenced the interest of organometallic complexes for the preparation of metal nanoparticles of controlled size and shape. This methodology was extended to the synthesis of metal oxide nanoparticles through a two-step approach : 1) the formation of metal nanoparticles through decomposition of the organometallic precursor, and 2) the oxidation of the as-formed nanoparticles. This approach has allowed the preparation of SnO2 and In2O3 particles for gas sensing [16,17] and was also used for the preparation of ZnO particles from the bisalkyl zinc precursor [Zn(c-C6H11)2] (2). [18] However, we reasoned that most organometallic complexes are air-sensitive and decompose exothermically in air. A controlled oxidation of the precursor in solution could therefore lead in one step to oxidized nanomaterials (oxides or hydroxides), the shape and size of which could in principle be controlled by the ligands or surfactants present. Herein we report the room-temperature synthesis of ZnO nanoparticles of controlled size and shape in solution. This route provides crystalline nanoparticles of regular disk or rod shapes depending on the characteristics of the solution, in terms of solvent, ligand, and concentration. The oxide particles are fully soluble in organic solvents giving rise to clear and luminescent solutions from which regular monolayers can be deposited. When a solution of the dicyclohexylzinc(ii) compound 2 in THF is left standing at room temperature in open air, the solvent slowly evaporates and leaves a white luminescent residue, which was characterized by XRD and TEM as being agglomerated nanoparticles of ZnO with a zincite structure that display no defined size or shape. If, however, ligands such as long chain amines are added under argon to a solution of 2 in THF, and the resulting mixture is treated as before, welldefined nano-objects are formed, the size and shape of which depend upon the reaction conditions. For example, the reaction can be carried out in THF using hexadecylamine (HDA) as a ligand. After a reaction time of 17 h and evaporation of the solvent (concentration of reagents: 0.042 molL ; standard procedure), homogeneous nanorods of approximately 8.1 D 2.6 nm are obtained, which can be redissolved in THF (Figure 1a). Several parameters were identified as important for controlling the size, shape, and homogeneity of the nanomaterials, namely the nature of the ligand, the relative concentration of the reagents, the solvent, the overall concentration of the reagents, the reaction time, the evaporation time, and the reaction/evaporation temperature. These parameters and their influence on the ZnO nanoobjects produced are listed in Table 1 and, in some cases, illustrated in Figures 1 and 2. All new materials were characterized by X-ray diffraction (XRD) and/or selectedarea electron diffraction (SAED) and consistently display the same pattern. The XRD pattern corresponds to the hexagonal zincite phase, space group P63mc (see Supporting Information; S1). It is evident from Table 1 that the control of the size and morphology of the ZnO particles results from the nature of the solution (solvent, ligands, concentrations, and so on). We have previously shown, in particular by NMR spectroscopy, that the shape control of metal nanoparticles was related to ligand coordination. A similar effect seemed however very surprising in the case of oxides and led us to undertake an NMR study. The addition of HDA to 2 in [D8]THF leads to H and C{H} NMR spectra that suggest the coordination of the amine to 2 through nitrogen atoms. After oxidation, the C{H} NMR spectra of the reaction mixture do not reveal the presence of any trace of 2 but show peaks attributed to HDA. The signals corresponding to the carbon atoms in the a, b, and g positions relative to nitrogen at d= 42.69, 34.58, and 27.31 ppm, respectively, are very broad (see Figure 3). This phenomenon has been observed previously on ruthenium nanoparticles and can be attributed to a fast exchange between free ligand molecules in solution and coordinated ligand molecules linked to ZnO through nitrogen atoms. This therefore demonstrates that throughout the process of [*] Dr. B. Chaudret, Dr. M. Monge, Dr. M. L. Kahn, Dr. A. Maisonnat Laboratoire de Chimie de Coordination du CNRS 205, route de Narbonne 31077 Toulouse C&dex 04 (France) Fax: (+33)5-6155-3003 E-mail: chaudret@lcc-toulouse.fr

Abstract: A method is provided for growing thin oxide films on the surface of a substrate by alternatively reacting the surface of the substrate with a metal source material and an oxygen source material. The oxygen source material is preferably a metal alkoxide. The metal source material may be a metal halide, hydride, alkoxide, alkyl, a cyclopentadienyl compound, or a diketonate.

Abstract: Fourteen titanium alkoxides were synthesized for comparison of their catalytic properties in the bulk and solution polymerization of lactide (LA). In bulk polymerizations, they are effective catalysts in terms of polymer yield and molecular weight. Titanatranes gave polylactides with significantly increased molecular weight over more extended polymerization times, and those with five-membered rings afforded polymers in higher yields and with larger molecular weights than their six-membered ring counterparts. Steric hindrance of the rings was found to significantly affect polymer yields. Increased heterotactic-biased poly(rac-LA) was formed as the number of chlorine atoms increased in TiCl(x)(O-i-Pr)(4)(-)(x). In solution polymerizations, titanium alkoxides catalyzed controlled polymerizations of LA, and end group analysis demonstrated that an alkoxide substituent on the titanium atom acted as the initiator. That polymerization is controlled under our conditions was shown by the linearity of molecular weight versus conversion. A tendency toward formation of heterotactic-biased poly(rac-LA) was observed in the solution polymerizations. The rate of ring-opening polymerization (ROP) and the molecular weight of the polymers are greatly influenced by the substituents on the catalyst, as well as by factors such as the polymerization temperature, polymerization time, and concentration of monomer and catalyst.

Abstract: A series of novel five-coordinate aluminium mono alkoxide complexes supported by R1,R2BPBA (bis-3-R1-5-R2-phenoxymethyl-bisamine) ligands were synthesized to probe the effect of electronic variation in the supporting ligand on the rate of e-caprolactone polymerization. Substitution on the aromatic position para to the phenoxide donor oxygen by tert-butyl, methoxy and bromo substituents furnished aluminium complexes that catalyzed the polymerization of e-caprolactone at different rates. We propose that a subtle interplay between complex Lewis acidity and alkoxide nucleophilicity determines the overall rate of polymerization in these systems.

Abstract: Titania and sulfated-titania were prepared by the sol–gel method using titanium alkoxide as titania precursor. BET specific surface areas on samples calcined at 600 °C were 57 and 62 m2/g for titania and sulfated-titania, respectively. FTIR spectra of sulfated samples show the 1360–1370 cm−1 absorption band assigned to SO vibrations. Moreover, by means of FTIR-pyridine absorption the strength of the sulfate bonded on the TiO2 surface was studied. Pyridine absorption bands assigned to Lewis and Bronsted acidic sites were identified on sulfated TiO2. A diminution of the band gap (Eg) by effect of sulfation was observed by UV-Vis spectroscopy. X-ray diffraction patterns show that sulfate ions stabilize the anatase phase. The photoactivity of the samples determined in the 2,4-dinitroaniline decomposition was found to be higher in sulfated samples. A model is proposed, in which the sulfate anchored to the titania surface acts as an electron trap during photo activation leading to an enhancement of activity.

Abstract: Liquid feed flame spray pyrolysis of solutions of a metal oxide precursor which is an alkoxide or C1-6 carboxylate and at least one second metal oxide precursor and/or second metal compound dissolved in oxygenated solvent by combustion with oxygen lead to the formation of sub-micron mixed-metal oxide powders not accessible by other processes or by the pyrolysis of metal chlorides or nitrates. The powders have numerous uses in advanced materials applications including particulate solid state lasers, advanced ceramic materials, and as catalysts in organic synthesis and automobile exhaust systems.

Abstract: The cyclopropanation reaction of an alkene with a metal carbenoid has been studied by means of the B3LYP hybrid density functional method. The cyclopropanation of ethylene with a lithium carbenoid or a zinc carbenoid [Simmons-Smith (SS) reagent] goes through two competing pathways, methylene transfer and carbometalation. Both processes are fast for the lithium carbenoid, while, for the zinc carbenoid, only the former is fast enough to be experimentally feasible. The reaction of an SS reagent (ClZnCH(2)Cl) with ethylene and an allyl alcohol in the presence of ZnCl(2) was also studied. The allyl alcohol reaction was modeled with an SS reagent/alkoxide complex (ClCH(2)ZnOCH(2)CH=CH(2)) formed from the SS reagent and allyl alcohol. Two modes of acceleration were found. The first involves the well-accepted mechanism of 1,2-chlorine migration, and the second involves a five-centered bond alternation. The latter was found to be more facile than the former and to operate equally well both with ethylene and with aggregates of SS reagent/alkoxide complexes. Calculations on the SS reaction with 2-cyclohexen-1-ol offer a reasonable model for the hydroxy-directed diastereoselective SS reaction, which has been used for a long time in organic synthesis.

Abstract: Hetero-bimetallic Fe(II) alkoxide/aryloxides were evaluated as initiators for the ring-opening polymerization of rac-lactide. [(THF)NaFe(OtBu)3]2 (1) and [(THF)4Na2Fe(2,6-diisopropylphenolate)4] (2) (THF = tetrahydrofuran) both polymerized lactide efficiently at room temperature, with complex 1 affording better control over the molecular weight parameters of the resultant polymer. At conversions below 70%, a linear increase in molecular weight with conversion was observed, indicative of a well-controlled polymerization process. Complex 2 is the first example of a dianionic Fe(II) alkoxide and has been structurally characterized to reveal a distorted square planar FeO4 array in which both Na counterions bridge two aryloxide ligands and are further complexed by two THF ligands. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3798–3803, 2003

Abstract: A method of fabricating aluminum oxide films utilizing aluminum alkoxide precursors is described. The aluminum oxide film is formed by (a) providing an aluminum alkoxide precursor that is dissolved, emulsified or suspended in a liquid; (b) providing a vapor generated from the aluminum alkoxide precursor; and (c) depositing an aluminum oxide film on the substrate at a temperature greater than 500° C.

Abstract: Poly(dimethylsiloxane)(PDMS)−metal-oxo nanocomposites have been prepared as transparent monoliths from dimethyldiethoxysilane (DMDES) and metal alkoxides, M(OR)n, where M = Al(III), Ge(IV), Sn(IV), Ti(IV), Zr(IV), Nb(V), and Ta(V). An accurate structural analysis of these hybrid materials has been performed by FTIR, Raman, and multinuclear NMR (1H, 13C, and 29Si) spectroscopies, SAXS, and DSC measurements. These techniques show that all the hybrid systems present a structure based on amorphous metal-oxo nanodomains embedded within the siloxane network. However, a strong influence of the cross-linking metal nature on the size of the metal-oxo nanoparticles and on the extent of the interface between inorganic domains and the siloxane component has been found. Spectroscopic measurements reveal a more important nanophase separation for the PDMS systems incorporating Al(III), Ti(IV), or Zr(IV) species as cross-linking agent than for the ones cross-linked with Nb(V), Ta(V), or Ge(IV) (in which 45% of the silico...

Abstract: In the present work a comparative study of the hydrolysis–polycondensation processes of different Si-substituted alkoxides, leading to hybrid materials with covalent –Si–C– bonds, was carried out. The following alkoxides were used: tetraethoxysilane (TEOS), methyltriethoxysilane (MTEOS) and vinyltriethoxysilane (VTEOS). Using gas chromatography coupled with mass spectrometry (CG-MS), nuclear magnetic resonance (29Si-NMR) and infrared spectrometry (IR), information about the sol–gel process in the mentioned systems were obtained. The differences in the reactivity of the studied alkoxides are connected with the steric effect of the organic substituents. The reactivity of the alkoxides in the early stages of the hydrolysis-polycondensation process increased in the order TEOS

Abstract: In the present work, composite copper containing silicate thin coatings (Cu/SiO2) were prepared on glass substrates by the sol-gel route. The preparation process included hydrolysis and subsequent polycondensation of corresponding alkoxide under refluxing and addition of soluble salt of antibacterial metal to the resulting sol. The coatings deposited by dipping process, were thermally treated in oxidative and reductive conditions up to 500°C for metal nanoparticles formation. The coating structure and the nanoparticles formation were studied by the X-ray Diffraction (XRD), UV-VIS and Heavy Ion Rutherford Backscattering (HIRBS) Spectroscopies. The antibacterial activity against Escherichia Coli was examined by the so-called antibacterial-drop test. The possible correlation between the layer interdiffusion after the thermal treatment and the antibacterial activity was considered and analyzed. The coatings exhibited a high antibacterial activity, which was enhanced with the increase of the metal concentration and was decreased with the increase of temperature of thermal treatment and metal nanoparticles formation.

Abstract: Nanocrystalline as well as submicron sized, non-agglomerated, spherical ZrO2 particles have been successfully synthesized using the sol-gel technique utilizing hydroxypropyl cellulose (HPC) as a polymeric steric stabilizer. The effect of various parameters such as the ratio of molar concentration of water and alkoxide (R), the molar concentration [HPC] and the molecular weight (MWHPC) of HPC polymer as well as the calcination temperature on ZrO2 nanocrystallites size and their phase evolution behavior is systematically studied. The phase evolution behavior of nanocrystalline ZrO2 is explained and correlated with the adsorption behavior of HPC polymer on ZrO2 nanoparticles surface, which is observed to be a function of R, [HPC], MWHPC and the calcination temperature. Optimum synthesis parameters for obtaining 100% tetragonal phase in nanocrystalline ZrO2 are identified for the present sol-gel method of synthesizing nanoparticles.

Abstract: Adsorption of methanol, ethanol, propanol and isopropanol on the -alumina ( 110C )surface is investigated with semiempirical (PM3) cluster calculations. It is found that all four alcohols chemisorb to the alumina surface when they come close to the surface with suitable orientation. The chemisorption is an exothermic process when the OH hydrogen interacts with a surface oxygen atom that is in turn close to a cation vacancy. In this case only O–H interaction is required for successful dehydrogenation. If the surface oxygen has no adjacent vacancies, both the oxygen and hydrogen from the alcohol OH must interact with the surface for successful dehydrogenation. Alkoxide formation by abstraction of the alcohol OH proton is found to be favored over alkoxide production by nucleophilic attack of the alcohol C by a surface Lewis base site followed by C–OH bond scission. © 2002 Elsevier Science B.V. All rights reserved.

Abstract: Optically selective thin films of CoAl2O4 with a spinel structure were produced for an automotive lamps application by the sol-gel process using aluminum sec-butoxide, ethylacetoacetate chelating agent and cobalt nitrate hexahydrate. The use of two metal-oxide precursors is advantageous over the single bimetallic alkoxide precursor (aluminum cobalt isopropoxide), because it allows us to vary the Co/Al ratio in the precursor solution. We found that the Co/Al ratio should not exceed 0.3 if we are to achieve films with the characteristic blue colour at 700°C. The structural characteristics of the oxide powders were determined from infrared (IR) spectra and X-ray diffraction (XRD) analysis, while the optical properties of the films were investigated with UV-VIS spectroscopy.

Abstract: [Tris(hexamethyldisilyl)amide] yttrium is a catalyst for the controlled ring-opening polymerization of e-caprolactone when reacted with an excess of alcohol. Up to an alcohol-to-yttrium molar ratio of 50, the chain transfer to the alcohol is quantitative, and the molecular weight of the chains can be predicted from the monomer-to-alcohol molar ratio. At alcohol-to-yttrium ratios higher than 100, the alcohol is quantitatively consumed provided that 1,1,1,3,3,3-hexamethyldisilazane, which is formed as a byproduct, is removed from the reation medium. Depending on the structure of the alcohol, end-functional polyesters can be prepared (e.g., with N-pyrrolyl and 3-thienyl end groups). Well-defined block and random copolymers of e-CL with lactides and γ-bromo-e-caprolactone, respectively, have also been synthesized. Compared to aluminum alkoxides, the in situ formed yttrium alkoxides have the advantage of a much faster polymerization kinetics while preserving control.

Abstract: A general route toward surface-functionalized amorphous metal oxide nanoparticles via a sol−gel approach is presented. Modified metal alkoxides were obtained by the substitution of alkoxide groups against functionalized pentane-2,4-dione derivatives, which had potential initiating sites for atom transfer radical polymerization (ATRP). Surface-modified amorphous metal oxide nanoparticles of titanium, zirconium, tantalum, yttrium, and vanadium were synthesized using these novel precursors in a microemulsion-based sol−gel process. Particles with diameters below 200 nm were prepared, and the resulting surface-functionalized colloids were used as macroinitiators in ATRP reactions. The combination of the two well controllable processes, i.e., microemulsions for the formation of the inorganic core and ATRP for the polymer shell, allows for the good control over the composition and morphology of these core−shell systems.

Abstract: The synthesis of YAlO3 is described from commercially-available yttria and alumina preformed sols which have nanometer particle-size ranges. The products have been characterized by X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform (DRIFT) spectra, thermogravimetry—derivative thermogravimetry—differential thermal analysis (TG-DTG-DTA), scanning electron microscopy (SEM) as well as CHN-analysis, and are similar to those prepared by the alkoxide, nitrate and citrate routes. The proposed method is a simple, cheap and rapid synthetic route.

Abstract: TiO2 nanoparticles have been prepared by a novel alkoxide sol–gel precipitation. The presence of active carbon in different percentages could act as an interesting template. Upon calcination, carbon is eliminated leaving surface features significantly different from TiO2 prepared in the absence of carbon. Influence of calcination temperature and times will be studied. Detailed surface and structural characterisation of samples have been carried out. The correlations between residual carbon percentage after thermal treatment and photoactivity during phenol oxidation are reported.

Abstract: Oxidative dehydrogenation of ethanol to acetaldehyde has been performed on vanadium based catalysts prepared by grafting on titania–silica supports with different procedures. A comparison of the performances of the prepared catalysts in terms of activity and selectivity has been made. Grafting technique gives place to well dispersed catalysts that resulted more selective than catalysts prepared by impregnation. In particular, very selective catalysts have been obtained by grafting vanadium–titanium bimetallic alkoxides directly on silica support. The effect of both the preparation methods and the used supports on the catalytic performances have been studied and an attempt to correlate the observed properties with the obtained results has been made.

Abstract: A catalyst composition comprises the reaction product of an alkoxide or condensed alkoxide of a metal M, selected from titanium, zirconium, hafnium, aluminium, or a lanthanide, an alcohol containing at least two hydroxyl groups, a 2-hydroxy carboxylic acid and a base, wherein the molar ratio of base to 2-hydroxy carboxylic acid is in the range 0.01 - 0.79:1. The composition is useful as a catalyst for esterification reactions, especially for the production of polyesters such as polyethylene terephthalate, polytrimethylene terephthalate and polybutylene terephthalate.

Abstract: The successful stereocontrol of the Diels-Alder reaction of semicyclic dienes possessing a secondary and tertiary allylic magnesium alkoxide alcohol functionality and activated dienophiles such as methyl acrylate, methacrolein, acrolein, and N-phenylmaleimide is described.

Abstract: The oxidative dehydrogenation (ODH) of propane have been studied on three different vanadium oxide catalysts, containing comparable amounts of vanadium. All the proven catalysts have been prepared by grafting but following different procedures. One has been prepared by grafting vanadyl tri-isopropoxide, dissolved in n -hexane on a support of silica coated with a multi-layer of TiO 2 . The support has been prepared by grafting in three different steps titanium alkoxide on silica. Another catalyst has been prepared by partially hydrolysing vanadyl tri-isopropoxide, dissolved in isopropanol, before grafting the obtained product on the same support. The third catalyst has been prepared by reacting partially hydrolysed vanadyl tri-isopropoxide with titanium alkoxide in isopropanol and anchoring then the reaction product, a vanadium–titanium bimetallic alkoxide, directly on silica. The first and second catalysts have similar activities and selectivities, while the third catalyst is less active but more selective than the other two ones. A kinetic approach has been made and a pseudo-first order kinetic law has been used to interpret the results. All the observed catalytic phenomena have been interpreted also with the aid of the several used characterisation techniques.

Abstract: The novel alkali metal zinc-alkoxide and the first -siloxide aggregates [(thf)M(MeZn)(OtBu)2]21a (M = Li), 1b (M = Na), [(thf)2K(MeZn)(OSiMe3)2]22 and [(tmeda)KZn(OSiMe3)3]23 are easily accessible from the reaction of Me2Zn with MOR (molar ratio 1 ∶ 1; M = Li, Na, K; R = tBu, SiMe3) in boiling thf and tmeda, respectively. While 1a, 1b and 2 possess distorted M2Zn2O4 heterocubane frameworks, compound 3 consists of a K2Zn2O6 core of a strongly distorted, face-fused double-heterocubane with two missing corners. In contrast, heating a mixture of Me2Zn and KOtBu in the molar ratio of 1 ∶ 1 in toluene affords the donor solvent-free K–Zn–O cluster [K(MeZn)3(OtBu)4] 4 which crystallizes as a polymer of strongly distorted [KZn3O4] heterocubanes via intermolecular agostic K⋯MeZn interactions. The formation of the clusters may be rationalized in terms of alkali metal ion- and donor solvent-dependent ligand exchange reactions of methyl(alkoxide)- and methyl(siloxide)-zincates as initial products. Some of the initial products have been detected by means of electro spray ionisation (ESI) mass spectrometry.

Abstract: Fine catalyst particles are loaded on a sol-gel method porous carrier having fine pores of 0.1-50 nm and a carbon compound is decomposed to form a carbon nanotube film on the carrier that is aligned perpendicular to the carrier surface. The starting sol to be processed by a sol-gel method is a dispersion of fine alumina particles, fine aluminum hydroxide particles, fine silica particles or mixtures thereof. Alternatively, the starting sol may be an aluminum alkoxide, an alkoxysilane, a mixture thereof or a solution of an aluminum alkoxide, an alkoxysilane or a mixture thereof. If desired, a flammable or a thermally decomposable organic compound may be added as a microporous template.