Nicolas Keller

The Catalytic Use of Onion-like Carbon Materials for Styrene Synthesis by Oxidative Dehydrogenation of Ethylbenzene

-hybridizednanostructuredcarbonhasreceivedincreasingattention both from a fundamental point of view and forpotential applications. A large variety of new fullerene-related materials (giant fullerenes, nanotubes, nanospheres,nanocones, nanofolders, nanobundles, onion-like carbons(OLCs)) have been synthesized.

Carbon Nanofilaments in Heterogeneous Catalysis: An Industrial Application for New Carbon Materials?

Special carbon! Carbon nanofilaments differ from graphite and soot catalysts in their high stability during the oxidative dehydrogenation of ethylbenzene to styrene. The high yields of styrene achieved suggest that a first industrial application of carbon nanofilaments in catalysis is possible.

Large scale synthesis of carbon nanofibers by catalytic decomposition of ethane on nickel nanoclusters decorating carbon nanotubes

A large scale synthesis of carbon nanofibers with a controlled diameter of about 50 nm has been achieved at relatively low temperatures (550–650 °C) by the decomposition of ethane on a carbon nanotube supported nickel catalyst. The carbon nanofibers can be used as a catalyst or a catalyst support without subsequent purification, due to the use of carbon nanotubes as support, the high nanofiber yields, and the purity obtained.

Layer-by-layer deposited titanate-based nanotubes for solar photocatalytic removal of chemical warfare agents from textiles.

that play determingroles in photocatalytic reactions.The threat from chemical warfare agents (CWAs) hasevolved over the past century. Attacks both on the battlefieldand in civilian areas have demonstrated the high occurrenceof casualties and thus the need for efficient protection.Therefore, post-use decontamination procedures on exposedand contaminated materials are much required. The currentmethods investigated are incineration, destruction, and neu-tralization using various chemicals, adsorption of the con-taminants by an adsorbant, and the use of impermeablemembranes. All of these methods present significant draw-backs as they cannot be directly applied on the battlefield, orthese methods do not lead to the destruction of the toxicagents, but rather the adsorption of or a skin barrier to thecontaminants.The photocatalytic activity of TiO

Ethylene removal and fresh product storage: a challenge at the frontiers of chemistry. Toward an approach by photocatalytic oxidation.

Frontiers of Chemistry. Toward an Approach by Photocatalytic Oxidation Nicolas Keller,*,† Marie-Noel̈le Ducamp,‡ Didier Robert, and Valeŕie Keller† †Institut de Chimie et Proced́eś pour l’Energie, l’Environnement et la Sante ́ (ICPEES), CNRS, Strasbourg University, 25 rue Becquerel 67087, Strasbourg, France ‡UMR 95 QUALISUD, CIRAD, TA B 95/16, 73 Bd Jean-Franco̧is Breton, 34398 Montpellier Cedex 5, France Saint-Avold Antenna, Institut de Chimie et Proced́eś pour l’Energie, l’Environnement et la Sante ́ (ICPEES), CNRS, Strasbourg University, Universite ́ de Lorraine, rue Victor Demange 57500 Saint-Avold, France

TiO2 photocatalysis damages lipids and proteins in Escherichia coli

ABSTRACT This study investigates the mechanisms of UV-A (315 to 400 nm) photocatalysis with titanium dioxide (TiO2) applied to the degradation of Escherichia coli and their effects on two key cellular components: lipids and proteins. The impact of TiO2 photocatalysis on E. coli survival was monitored by counting on agar plate and by assessing lipid peroxidation and performing proteomic analysis. We observed through malondialdehyde quantification that lipid peroxidation occurred during the photocatalytic process, and the addition of superoxide dismutase, which acts as a scavenger of the superoxide anion radical (O2·−), inhibited this effect by half, showing us that O2·− radicals participate in the photocatalytic antimicrobial effect. Qualitative analysis using two-dimensional electrophoresis allowed selection of proteins for which spot modifications were observed during the applied treatments. Two-dimensional electrophoresis highlighted that among the selected protein spots, 7 and 19 spots had already disappeared in the dark in the presence of 0.1 g/liter and 0.4 g/liter TiO2, respectively, which is accounted for by the cytotoxic effect of TiO2. Exposure to 30 min of UV-A radiation in the presence of 0.1 g/liter and 0.4 g/liter TiO2 increased the numbers of missing spots to 14 and 22, respectively. The proteins affected by photocatalytic oxidation were strongly heterogeneous in terms of location and functional category. We identified several porins, proteins implicated in stress response, in transport, and in bacterial metabolism. This study reveals the simultaneous effects of O2·− on lipid peroxidation and on the proteome during photocatalytic treatment and therefore contributes to a better understanding of molecular mechanisms in antibacterial photocatalytic treatment.

Single-Step Synthesis of SnS2 Nanosheet-Decorated TiO2 Anatase Nanofibers as Efficient Photocatalysts for the Degradation of Gas-Phase Diethylsulfide

We report on a facile one-step soft hydrothermal process for synthesizing 1D anatase TiO2 nanofibers decorated with ultrathin SnS2 nanosheets. H-titanate nanofibers were used as preshaped Ti precursor. Under controlled conditions, the H-titanate structure was transformed into anatase maintaining the fibril morphology, while at the same time SnS2 nanosheets were grown in situ on the surface of the nanofibers. The successful formation of SnS2 nanosheets on the TiO2 nanofibers was confirmed by high-resolution TEM, and together with XPS spectroscopy, the tight interface formed between the SnS2 and the anatase TiO2 nanofibers was verified. The 1D SnS2/TiO2 hierarchical nanostructures with semiconductor heterojunction were proven to be very efficient under artificial solar irradiation in the photocatalytic degradation of gaseous diethylsulfide as simulant for live yperite chemical warfare agent as well as model substrate for malodorous organosulfide volatile organic compounds. SnS2 did not operate as a visible light sensitizer for TiO2 but rather as an oxidizing agent and charge-carrier separator. The semiconductor ratio in the heterostructure controlled the photoactivity. Samples with no or high content of SnS2 were less active than those with moderate SnS2 content. Enhanced reactivity was ascribed to an efficient separation of the photogenerated charge carriers driven by the differences in band edge positions and favored by the tight interface within the coupled heterostructure.

One step synthesis of niobium doped titania nanotube arrays to form (N,Nb) co-doped TiO2 with high visible light photoelectrochemical activity

The chemical modification of aligned titanium dioxide nanotube (TiO2-NT) arrays provides new doping possibilities to improve their photoelectrochemical activity under visible light. Niobium doped TiO2-NTs containing up to 15% of Nb in the near-surface region are prepared by a flexible single step procedure using a fluoroniobate complex simultaneously acting as a source of the doping element and fluoride anions required for nanotube formation. This negatively charged complex allows an efficient insertion of Nb in the forming TiO2-NT structure during the anodization process. These nanotube arrays are further modified with nitrogen to achieve (Nb,N) co-doped nanotubes with noticeable visible light photoelectrochemical activity.

Numeration methods for targeting photoactive materials in the UV-A photocatalytic removal of microorganisms

This tutorial review reports on the different numeration methods for evaluating the efficiency of the photocatalytic action on microorganisms. Here we put forward the advantages and drawbacks of the standard methods such as the plate count, the fluorescence techniques and the Most Probable Number method for determining the biocidal photocatalytic activity and thus selecting efficient photocatalytic materials among complex systems. We highlight that bacterial spores are a representative and suitable tool for meeting the restrictive requirements resulting from the complex use of living matter instead of chemical targets.

Ru catalysts for levulinic acid hydrogenation with formic acid as a hydrogen source

The catalytic hydrogenation of levulinic acid (LA) with formic acid (FA) as a hydrogen source into γ-valerolactone (GVL) is considered as one of the crucial sustainable processes in todays biorefinery schemes. In the current work, we investigated the modification of Ru/C as efficient catalysts for both formic acid decomposition and levulinic acid hydrogenation in comparison with Pd and Pt catalysts. In order to better understand what features are responsible for high catalytic performance, we combined experimental tests, DFT calculations together with extensive material characterization. In LA hydrogenation with FA as a hydrogen source, the intermediate surface formate inhibits at least partially the LA hydrogenation. In addition, the FA decomposition is highly sensitive to the kind of the preparation method of the Ru/C catalyst: (i) the process looks structure sensitive favored on larger particles and (ii) residual chlorine decreases significantly the FA decomposition rate.