Near- and Supercritical Alcohols as Solvents and Surface Modifiers for the Continuous Synthesis of Cerium Oxide Nanoparticles.

Supercritical fluids offer fast and facile routes toward well-crystallized tailor-made cerium oxide nanoparticles. However, the use of surfactants to control morphology and surface properties remains essential. Therefore, although water, near-critical (nc) or supercritical (sc), is a solvent of choice, the poor water solubility of some surfactants could require other solvent systems such as alcohols, which could themselves behave as surface modifiers. In here, the influence of seven different alcohols, MeOH, EtOH, PrOH, iPrOH, ButOH, PentOH, and HexOH, in alcothermal conditions (300 °C, 24.5 MPa) over CeO(2) nanocrystals (NCs) size, morphology, and surface properties was investigated. The crystallite size of the CeO(2) nanocrystals can be tuned in the range 3-7 nm depending on the considered alcohol, and their surface has been modified by these solvents without the use of surfactants. Mechanisms are proposed for the interaction of primary and secondary alcohols with CeO(2) surface and its functionalization during the synthesis based on FTIR and TGA-MS studies. This study allows apprehending the role of alcohols during the synthesis and may lead to an informed choice of solvent as a function of the required size and surface properties of CeO(2) NCs. It also opens new route to CeO(2) functionalization using supercritical alcohol derivatives

Functional crosslinked polymer particles synthesized by precipitation polymerization for liquid chromatography

Highly crosslinked functional polymer particles with narrow size distribution have been produced by precipitation copolymerization of divinylbenzene, ethylene glycol dimethacrylate and vinylbenzyl chloride using a simple reflux protocol. After establishing the satisfactory synthesis conditions, we produced uniform chlorobenzyl particles with different size depending on the polymerization times. The porosity of those particles was modulated from microporous to mesoporous structure by using various porogens such as toluene, dodecanol, cyclohexanol and polypropylene glycol. These particles were tested as stationary phase in high-performance liquid chromatography for the separation of polycyclic aromatic hydrocarbons in reversed-phase mode. The separation was observed even for elution 100% organic (methanol) without any participation of water fraction in the eluent composition. The influences of particles size, specific surface area and packing conditions on the separation behavior were investigated. (c) 2007 Elsevier B.V. All rights reserved

A simple route towards low-temperature processing of nanoporous thin films using UV-irradiation: Application for dye solar cells

Fabrication of anatase TiO2 porous films at low temperature was achieved by a very simple, straightforward and cheap method involving the connection of oxide particles by UV-irradiation in air. The novelty of the method relies on the direct UV-irradiation of oxide nanoparticles, without the presence of any oxide precursor or any additional treatment to form the nanoparticulate film. As electrodes for dye solar cells (DSCs), the 1–3 μm-thick films modified with Dyesol N3 dye showed high photovoltaic responses, a maximum overall energy conversion efficiency of 2.4–2.5% being measured under AM1.5 illumination at 100 and 140 mW cm−2. This method was extended to other semi-conducting oxides such as SnO2. Efficiencies as high as 1.8% and 1.5% were measured under AM1.5 illumination at 64 and 140 mW cm−2, respectively. This approach draws new prospects in the field of plastic organic–inorganic hybrid devices

A new route towards nanoporous TiO2 as powders or thin films from the thermal treatment of titanium-based hybrid materials.

Calcination of cyclopentadienyltitanium-based organic-inorganic hybrid materials at 450-500 °C led to the formation of anatase titanium dioxide as white powders consisting of a porous network of aggregated nanoparticles, the nanoporosity detected being related to the inter-particle space. Depending on the calcination temperatures, the surface area of the titanium dioxide particles varied from 65 to 158 m(2) g(-1)

Nanoscaled tin dioxide films processed from organotin-based hybrid materials: An organometallic route toward metal oxide gas sensors

Nanocrystalline tin dioxide (SnO2) ultra-thin films were obtained employing a straightforward solution-based route that involves the calcination of bridged polystannoxane films processed by the sol–gel process from bis(triprop-1-ynylstannyl)alkylene and -arylene precursors. These films have been thoroughly characterized by FTIR, contact angle measurements, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force (AFM) and scanning electron (SEM) microscopies. Annealing at a high temperature gave 30–35 nm thick cassiterite SnO2 films with a mean crystallite size ranging from 4 to 7 nm depending on the nature of the organic linker in the distannylated compound used as a precursor. In the presence of H2 and CO gases, these layers led to highly sensitive, reversible and reproducible responses. The sensing properties were discussed in regard to the crystallinity and porosity of the sensing body that can be tuned by the nature of the precursor employed. Organometallic chemistry combined with the sol–gel process therefore offers new possibilities toward metal oxide nanostructures for the reproducible and sensitive detection of combustible and toxic gase

Syntheses and characterization of new organically grafted silica foams

In this study, new hybrid Organo-Si(HIPE) macrocellular foams have been synthesized via sol–gel process, direct emulsions and lyotropic mesophases as templating agents followed by a final grafting process of silane organically modified. A variety of sililated groups, including methyl, benzyl, amines, mercapto, pyrrol and dinitro have been successfully grafted. The effects of the various organosilanes on the physical chemical properties of the resulting materials have been thoroughly characterized using several analytical techniques (SEM, TEM, SAXS, mercury porosimetry, nitrogen adsorption isotherms, FTIR, 29Si MAS NMR). If the resulting grafted compounds, labeled gOrgano Si(HIPE), exhibit the same macroscopic texture than the starting silica open-cell matrices, we found a reduction of the mesoporosity depending upon the size of the organic moiety in use and the associated enhance molecular hindrance. Final porous materials functionalized at the molecular level are potential outstanding candidates for applications such as heterogeneous catalyst, scavenger and sensor

Design of Hierarchical Porous Carbonaceous Foams from a Dual-Template Approach and Their Use as Electrochemical Capacitor and Li Ion Battery Negative Electrodes

Porous carbon foams were prepared by pyrolysis of phenolic resin from a dual-template approach using silica monoliths as hard templates and triblock copolymers as soft templating agents. Macroporosity of 50-80% arose from the Si(HIPE) hard template (the acronym "HIPE" refers to the high internal phase emulsion process), while the soft template generated micro- or mesoporosity, according to the operating procedure. The final materials exhibited a Brunauer-Emmett- Teller specific surface area of 600-900 m2 3 g-1. Their performances as electrodes for electrochemical capacitors or Li ion battery negative electrodes were investigated. The mesoporous foams gave the best capacitance, up to 20 F 3 g-1. In battery configuration, the microporous foams delivered an irreversible capacity of 500-600 mA 3 h 3 g-1 during the first discharge. Upon charging, partial extraction of Li gave reversible capacities of 125-150 mA 3 h 3 g-1

Designing Nanotextured Vanadium Oxide-Based Macroscopic Fibers: Application as Alcoholic Sensors

Composite vanadium oxide/PVA/latex macroscopic fibers have been generated by using an extrusion process. Specifically, inorganic vanadium oxide fibers enable the detection of 0.1 ppm of ethanol within 3-5 s at 42 °C, which is certainly one of the highest sensitivities to date concerning alcohol sensors. More importantly, by varying the starting latex inclusion contents, the shear rates applied during the extrusion process, and the final appliance of a thermal treatment, we were able to segregate each parameter involved within the mechanical and sensing properties associated with these as-synthesized fibers, i.e., the amount of the organic insulator counterpart, the degree of vanadium oxide ribbons alignment, and the induced porosity reached upon latex removal. Overall, we found out that all the parameters described above and involved within the as-synthesized fibers' mechanical and sensing properties are acting within a partitive action mode rather than a cooperative one