Michaël Bensimon

Easily-prepared dinickel phosphide (Ni2P) nanoparticles as an efficient and robust electrocatalyst for hydrogen evolution

Polydispersed dinickel phosphide (Ni2P) nanoparticles were synthesized by a simple and scalable solid-state reaction. These nanoparticles are an excellent and robust catalyst for the electrochemical hydrogen evolution reaction, operating in both acidic and basic solutions.

Over-expression of PHO1 in Arabidopsis leaves reveals its role in mediating phosphate efflux

Inorganic phosphate (Pi) homeostasis in multi-cellular eukaryotes depends not only on Pi influx into cells, but also on Pi efflux. Examples in plants for which Pi efflux is crucial are transfer of Pi into the xylem of roots and release of Pi at the peri-arbuscular interface of mycorrhizal roots. Despite its importance, no protein has been identified that specifically mediates phosphate efflux either in animals or plants. The Arabidopsis thaliana PHO1 gene is expressed in roots, and was previously shown to be involved in long-distance transfer of Pi from the root to the shoot. Here we show that PHO1 over-expression in the shoot of A. thaliana led to a two- to threefold increase in shoot Pi content and a severe reduction in shoot growth. (31) P-NMR in vivo showed a normal initial distribution of intracellular Pi between the cytoplasm and the vacuole in leaves over-expressing PHO1, followed by a large efflux of Pi into the infiltration medium, leading to a rapid reduction of the vacuolar Pi pool. Furthermore, the Pi concentration in leaf xylem exudates from intact plants was more than 100-fold higher in PHO1 over-expressing plants compared to wild-type. Together, these results show that PHO1 over-expression in leaves leads to a dramatic efflux of Pi out of cells and into the xylem vessel, revealing a crucial role for PHO1 in Pi efflux.

Effect of surface pretreatment of TiO2 films on interfacial processes leading to bacterial inactivation in the dark and under light irradiation

Evidence is presented for radio-frequency plasma pretreatment enhancing the amount and adhesion of TiO2 sputtered on polyester (PES) and on polyethylene (PE) films. Pretreatment is necessary to attain a suitable TiO2 loading leading to an acceptable Escherichia coli reduction kinetics in the dark or under light irradiation for PES–TiO2 and PE–TiO2 samples. The amount of TiO2 on the films was monitored by diffuse reflectance spectroscopy and X-ray fluorescence. X-ray electron spectroscopy shows the lack of accumulation of bacterial residues such as C, N and S during bacterial inactivation since they seem to be rapidly destroyed by TiO2 photocatalysis. Evidence was found for Ti4+/Ti3+ redox catalysis occurring on PES–TiO2 and PE–TiO2 during the bacterial inactivation process. On PE–TiO2 surfaces, Fourier transform infrared spectroscopy (ATR-FTIR) provides evidence for a systematic shift of the na(CH2) stretching vibrations preceding bacterial inactivation within 60 min. The discontinuous IR-peak shifts reflect the increase in the C–H inter-bond distance leading to bond scission. The mechanism leading to E. coli loss of viability on PES–TiO2 was investigated in the dark up to complete bacterial inactivation by monitoring the damage in the bacterial outer cell by transmission electron microscopy. After 30 min, the critical step during the E. coli inactivation commences for dark disinfection on 0.1–5% wt PES–TiO2 samples. The interactions between the TiO2 aggregates and the outer lipopolysaccharide cell wall involve electrostatic effects competing with the van der Waals forces.

Iron oxide-mediated semiconductor photocatalysis vs. heterogeneous photo-Fenton treatment of viruses in wastewater. Impact of the oxide particle size

The photo-Fenton process is recognized as a promising technique towards microorganism disinfection in wastewater, but its efficiency is hampered at near-neutral pH operating values. In this work, we overcome these obstacles by using the heterogeneous photo-Fenton process as the default disinfecting technique, targeting MS2 coliphage in wastewater. The use of low concentrations of iron oxides in wastewater without H2O2 (wüstite, maghemite, magnetite) has demonstrated limited semiconductor-mediated MS2 inactivation. Changing the operational pH and the size of the oxide particles indicated that the isoelectric point of the iron oxides and the active surface area are crucial in the success of the process, and the possible underlying mechanisms are investigated. Furthermore, the addition of low amounts of Fe-oxides (1mgL-1) and H2O2 in the system (1, 5 and 10mgL-1) greatly enhanced the inactivation process, leading to heterogeneous photo-Fenton processes on the surface of the magnetically separable oxides used. Additionally, photo-dissolution of iron in the bulk, lead to homogeneous photo-Fenton, further aided by the complexation by the dissolved organic matter in the solution. Finally, we assess the impact of the presence of the bacterial host and the difference caused by the different iron sources (salts, oxides) and the Fe-oxide size (normal, nano-sized).

Innovative photocatalyst (FeOx–TiO2): transients induced by femtosecond laser pulse leading to bacterial inactivation under visible light

This study reports the photosensitizing effect/mechanism of FeOx under visible light irradiation and charge transfer to TiO2 on FeOx–TiO2 cosputtered film. The transients which were photo-induced by femto-second laser pulses at 545 nm (25 fs) were identified, in addition to the concomitant bleaching bands at 400 nm). This observation unexpectedly confirms the role of FeOx absorbing light in the visible region. The important role of TiO2 is reported, leading to bacterial inactivation in the FeOx–TiO2 co-sputtered films.

Silylation and sulfonation of structured supported catalysts active in the decoloration of azo-dyes under visible light

Structured silica woven fabrics have been derivatized with functional groups able to anchor by exchange of Fe3+-ions and TiO2 showing a stable performance during the visible light induced decoloration of the Orange II azo-dye. The kinetics and efficiency of the decoloration mediated by the catalytic loaded silica fabrics with Fe3+-ions were seen to be much higher than found with homogeneous Fenton reagents (Fe3+/H2O2) with the equivalent Fe3+ content. The same was observed for derivatized membranes where TiO2 has been anchored as the active catalyst surface species. In the case of the silica Fe3+-ions loaded fabrics, the decoloration was studied as a function of the amount of H2O2 oxidant added in solution, the intensity of the applied visible light and the concentration of the initial Orange II. In the case of the silica-TiO2 fabrics the decoloration kinetics was observed to be a function of the O2 present in solution. In the case of the derivatized Fe3+ and TiO2 loaded silica fabrics, the decoloration process presented three common features: (a) the decoloration process was observed only in the presence of light pointing to a photo-induced process in both cases, (b) the decoloration was also observed to be truly catalytical following repetitive cycles for Orange II, and finally (c) the decoloration processes were limited by the mass transfer kinetics taking place at the surface of both derivatized fabric catalyst and proceeded with about the same kinetics in both cases. The numerical values for the diffusion distance of the radicals species OHradical dot and HO2radical dot as well as the decrease in the concentration of radicals away from the silica fabric during the photodegradation of Orange II is estimated by the Smoluchowski diffusion equation.

New evidence for Cu-decorated binary-oxides mediating bacterial inactivation/mineralization in aerobic media

Binary oxide semiconductors TiO2-ZrO2 and Cu-decorated TiO2-ZrO2 (TiO2-ZrO2-Cu) uniform films were sputtered on polyester (PES). These films were irradiated under low intensity solar simulated light and led to bacterial inactivation in aerobic and anaerobic media as evaluated by CFU-plate counting. But bacterial mineralization was only induced by TiO2-ZrO2-Cu in aerobic media. The highly oxidative radicals generated on the films surface under light were identified by the use of appropriate scavengers. The hole generated on the TiO2-ZrO2 films is shown to be the main specie leading to bacterial inactivation. TiO2-ZrO2 and Cu-decorated TiO2-ZrO2 films release Zr and Ti <1ppb and Cu 4.6ppb/cm(2) as determined by inductively coupled plasma mass spectrometry (ICP-MS) This level is far below the citotoxicity permitted level allowed for mammalian cells suggesting that bacterial disinfection proceeds through an oligodynamic effect. By Fourier transform attenuated infrared spectroscopy (ATR-FTIR) the systematic shift of the predominating νs(CH2) vibrational-rotational peak making up most of the bacterial cell-wall content in C was monitored. Based on this evidence a mechanism suggested leading to CH bond stretching followed by cell lysis and cell death. Bacterial inactivation cycling was observed on TiO2-ZrO2-Cu showing the stability of these films leading to bacterial inactivation.

The diffuse infiltration of road runoff: an environmental improvement

The Laboratory of Engineering and Environmental Geology (GEOLEP) has been mandated by Swiss authorities (Swiss Federal Road Office FedRO) to test a new road runoff management concept. This concept promotes the diffuse infiltration of road runoff into infiltration slopes designed for this purpose. Soils retain particles and contaminants; this lowers the road impact on the environment and simultaneously improves aquifer recharge. This concept has to be adapted to aquifer vulnerability and traffic conditions. Thus, a real-scale experimental station was designed and built in Switzerland to assess the feasibility of this new concept. This station allowed the testing of two lysimeters composed of 80 cm of A and B-horizons. Water and chemical fluxes were measured at the lysimeter bases. Road runoff was sampled in a distinct collector. Infiltration of road runoff into the local aquifer was monitored thanks to six piezometers. Water quality and quantity were therefore measured at each step of the infiltration process. Results provided by 112 natural events showed that soil horizons accommodated road runoff flows. The least favourable conditions for contaminant retention are encountered during thunderstorms, when high concentrations of substances deposited on the road are remobilised within a short time and rapidly percolates through soil horizons. Thus, three artificial events were designed to mimic heavy thunderstorms. Concentrations measured in road runoff notably decreased after soil filtration. Substances with high distribution coefficients Kd (low mobility) had concentrations reduced to lower values (1/1000 to 1/10,000), while those with high mobility retained similar concentrations even after soil filtration. However, these mobile substances exhibited low concentrations in the underlying aquifer due to dilution. This innovative road runoff management concept can thus be readily implemented outside groundwater protection zones where aquifers are slightly vulnerable; it undoubtedly lowers the environmental impact of roads, does not endanger road integrity, and locally increases aquifer recharge.

Treatment of pleural malignancies by photo-induction combined to systemic chemotherapy: Proof of concept on rodent lung tumors and feasibility study on porcine chest cavities

Low‐dose, Visudyne®‐mediated photodynamic therapy (photo‐induction) was shown to selectively enhance tumor vessel transport causing increased uptake of systemically administered chemotherapy in various tumor types grown on rodent lungs. The present experiments explore the efficacy of photo‐induced vessel modulation combined to intravenous (IV) liposomal cisplatin (Lipoplatin®) on rodent lung tumors and the feasibility/toxicity of this approach in porcine chest cavities.

Interstitial fluid pressure: A novel biomarker to monitor photo‐induced drug uptake in tumor and normal tissues

Low‐dose photodynamic therapy PDT (photoinduction) can modulate tumor vessels and enhance the uptake of liposomal cisplatin (Lipoplatin®) in pleural malignancies. However, the photo‐induction conditions must be tightly controlled as overtreatment shuts down tumor vessels and enhances normal tissue drug uptake.