Influence of Morphology and Crystallinity on Surface Reactivity of Nanosized Anatase TiO₂ Studied by Adsorption Techniques. 1. The Use of Gaseous Molecular Probes

Various titanium dioxide nanoparticles were prepared by sol–gel method in order to obtain samples showing different sizes and morphologies. An original approach based on the adsorption of gaseous molecules from the gas phase was proposed to gain information about surface energy of nanosized TiO₂ anatase in terms of interfacial reactivity and heterogeneity. Argon, nitrogen, and ammonia were selected as such surface molecular probes. The mainly observed crystallographic faces of anatase particles were the {101} and {001} surfaces together with the {100} one. Their abundance was correlated with the energy distribution inferred from the local isotherms of argon adsorption in the low-pressure range. The acid character of the anatase surface was probed by nitrogen molecules, and, consequently, the location of polar sites on the particle surface could be determined in correlation with the argon adsorption domains. Moreover, the number and the strength of surface acid sites were evaluated with the aid of two-cycle adsorption of gaseous ammonia supplemented by appropriate flow microcalorimetry measurements. This molecular probe revealed significant differences among the samples depending on their crystal shape or face distribution

Is There a Trojan-Horse Effect during Magnetic Nanoparticles and Metalloid Cocontamination of Human Dermal Fibroblasts?

This study investigates the issue of nanoparticles/pollutants cocontamination. By combining viability assays, physicochemical and structural analysis (to probe the As speciation and valence), we assessed how γFe₂O₃ nanoparticles can affect the cytotoxicity, the intra- and extracellular speciation of As­(III). Human dermal fibroblasts were contaminated with γFe₂O₃ nanoparticles and As­(III) considering two scenarios: (i) a simultaneous coinjection of the nanoparticles and As, and (ii) an injection of the nanoparticles after 24 h of As adsorption in water. In both scenarios, we did not notice significant changes on the nanoparticles surface charge (zeta potential ∼ –10 mV) nor hydrodynamic diameters (∼950 nm) after 24 h. We demonstrated that the coinjection of γFe₂O₃ nanoparticles and As in the cellular media strongly affects the complexation of the intracellular As with thiol groups. This significantly increases at low doses the cytotoxicity of the As nonadsorbed at the surface of the nanoparticles. However, once As is adsorbed at the surface the desorption is very weak in the culture medium. This fraction of As strongly adsorbed at the surface is significantly less cytotoxic than As itself. On the basis of our data and the thermodynamics, we demonstrated that any disturbance of the biotransformation mechanisms by the nanoparticles (<i>i.e.</i>, surface complexation of thiol groups with the iron atoms) is likely to be responsible for the increase of the As adverse effects at low doses

Solvent-free Preparation of Ru/Al₂O₃ Catalysts for CO₂ Methanation: An Example of Frugal Innovation

To reduce the environmental impact of supported catalyst production in compliance with the recommendations of the UN’s 12th objective, which encourages more sustainable consumption and production patterns, we propose to revisit sol–gel chemistry in a more frugal mode. The principle of frugal innovation is to simplify products and processes, eliminate complexities to make solutions easier to understand and use, and reduce production costs. By this way, the synthesis of ruthenium-based catalysts supported on γ-AlOOH and γ-Al2O3 is revised via solvent-free sol–gel chemistry. Such catalysts are successfully prepared in one-pot preparation of the active phase and the support using Ru(acac)3/Al alkoxide that requires no sacrificial organic pore-generating agent, no washing, and no filtration and produces no liquid waste. The mixed Ru/Al precursor is hydrolyzed with a stoichiometric amount of water without any solvent. The obtained materials containing 1 and 3% Ru/Al molar ratios have high specific surface areas, from 300 to 690 m2·g–1 and exhibit well dispersed NPs of 1–4 nm on γ-AlOOH with interesting CO2 methanation activity and 100% CH4 selectivity. This proves that a frugal synthesis approach can do as well as traditional synthesis methods while having a much lower environmental impact (cE-factor, water consumption, and energy consumption are 24, 69, and 24 to 42 times lower, respectively) than the standard multistep protocol.

Solvent-free Preparation of Ru/Al₂O₃ Catalysts for CO₂ Methanation: An Example of Frugal Innovation

To reduce the environmental impact of supported catalyst production in compliance with the recommendations of the UN’s 12th objective, which encourages more sustainable consumption and production patterns, we propose to revisit sol–gel chemistry in a more frugal mode. The principle of frugal innovation is to simplify products and processes, eliminate complexities to make solutions easier to understand and use, and reduce production costs. By this way, the synthesis of ruthenium-based catalysts supported on γ-AlOOH and γ-Al2O3 is revised via solvent-free sol–gel chemistry. Such catalysts are successfully prepared in one-pot preparation of the active phase and the support using Ru(acac)3/Al alkoxide that requires no sacrificial organic pore-generating agent, no washing, and no filtration and produces no liquid waste. The mixed Ru/Al precursor is hydrolyzed with a stoichiometric amount of water without any solvent. The obtained materials containing 1 and 3% Ru/Al molar ratios have high specific surface areas, from 300 to 690 m2·g–1 and exhibit well dispersed NPs of 1–4 nm on γ-AlOOH with interesting CO2 methanation activity and 100% CH4 selectivity. This proves that a frugal synthesis approach can do as well as traditional synthesis methods while having a much lower environmental impact (cE-factor, water consumption, and energy consumption are 24, 69, and 24 to 42 times lower, respectively) than the standard multistep protocol.