Using 222 Rn for hydrograph separationin a micro basin (Luxembourg)

In order to obtain information on the hydrological signature of rivers during and after heavy rain events, small catchment areas are selected as experimental sites. Hydrograph separations based on environmental tracers are performed. Natural isotopic tracers such as 18O, 2H and particularly 222Rn may help to distinguish the components dominating the outflow, particularly of 'pre-event waters', 'event waters' and 'post-event waters'. Even with moderate concentrations in groundwater, radon can be a very sensitive indicator of groundwater input into rivers. The selected microbasin under investigation is situated in the western part of Luxembourg and belongs to the Attert River catchment. At chosen points at the basin's outflow radon detectors continuously measure radon activity in water. The radon monitors are installed together with high precision thermometers, conductivity meters, flow meters and automatic water samplers for chemical analysis. Besides the continuous measurements, grab water samples are taken at different locations along the stream, most of them during periods of heavy rain events. Presented are the results of a one year measurement campaign. During the dry season i.e. during more or less continuous discharge conditions, the observed mean values do not show substantial variations and can be used as reference values. Fluctuations of the measured data during rain events are discussed and the interplay between the different parameters analysed

Synthesis of colloidal silicalite-1 at high temperatures

Stable colloidal suspensions of silicalite-1 were prepared by hydrothermal treatment of clear precursor suspensions at high temperatures, 150 and 170 °C. The precursor suspensions were pretreated prior to hydrothermal treatment. Different pretreatment procedures were applied, namely ultrasonic treatment or heating at 45–60 °C, for different periods of time. In all cases, the size of the crystals decreased with increasing the time of pretreatment. The pretreatment procedure was found to influence the behavior of the tetrapropylammonium hydroxide solution used as structure-directing template during hydrothermal treatment. Colloidal stability of pretreated samples was improved compared to samples prepared by direct hydrothermal treatment

Carbide, nitride and sulfide transition metal-based macrospheres

A general method for the preparation of transition metal carbide, nitride and sulfide composite materialsin the form of macroscopic beads is reported. Ti- and W-based materials were prepared by thermalconversion of Ti- or W-loaded ion-exchange resins in an appropriate atmosphere, inert, NH3or H2S,respectively. The spherical macroscopic shape of the resin was preserved in most of the product compositematerials. The fabrication of pure TiN spherical macrostructures is also demonstrated by using TiO2spherical beads prepared from the Ti-loaded resin by resin oxidation at 600◦C in the thermal treatmentprocedure

Characterisation and properties of visible light-active bismuth oxide-titania composite photocatalysts

© 2019 Elsevier B.V. Bismuth oxide – titanium dioxide composite materials were produced by pulsed DC reactive magnetron sputtering onto two types of commercially available titanium dioxide nanoparticles. The use of an oscillating bowl enabled deposition of bismuth oxide uniformly onto loose powders, in contrast to solid substrates typically used for the conventional magnetron sputtering processes. Variation of the deposition time allowed the production of composite materials with different amounts of bismuth oxide. The composite materials, as well as uncoated titania powders, were extensively analysed by a range of analytical techniques, including SEM/EDX, XRD, BET, XPS, TEM and UV–visible diffuse reflectance spectroscopy. Photocatalytic properties of the materials were assessed under simulated visible light irradiation via degradation of acetone and methanol through measurements of carbon dioxide evolution. Additionally, the composite materials were characterised with a newly developed technique of reversed double-beam photoacoustic spectroscopy in order to obtain information on the distribution of electron traps. Bismuth oxide was found in crystalline β-Bi 2 O 3 form on both types of substrates without any additional heat treatment applied. Though the distribution of bismuth oxide on titanium dioxide was found to depend strongly on particle size and deposition time used, the composite materials exhibited significantly enhanced visible light photocatalytic activity compared to either of the commercial titania materials used as a substrate

A Novel Technique for the Deposition of Bismuth Tungstate onto Titania Nanoparticulates for Enhancing the Visible Light Photocatalytic Activity

A novel powder handling technique was used to allow the deposition of bismuth tungstate coatings onto commercial titanium dioxide photocatalytic nanoparticles. The coatings were deposited by reactive pulsed DC magnetron sputtering in an argon/oxygen atmosphere. The use of an oscillating bowl with rotary particle propagation, positioned beneath two closed-field planar magnetrons, provided uniform coverage of the titania particle surfaces. The bismuth/tungsten atomic ratio of the coatings was controlled by varying the power applied to each target. The resulting materials were characterized by X-ray diffraction, energy-dispersive X-ray spectroscopy (EDX), Brunauer–Emmett–Teller (BET) surface area measurements, transmission electron microscopy (TEM), and UV-visible diffuse reflectance spectroscopy. Photocatalytic properties under visible light irradiation were assessed using an acetone degradation test. It was found that deposition of bismuth tungstate onto titania nanoparticles resulted in significant increases in visible light photocatalytic activity, compared to uncoated titania. Of the coatings studied, the highest photocatalytic activity was measured for the sample with a Bi/W atomic ratio of 2/1

Reactive magnetron sputtering deposition of bismuth tungstate onto titania nanoparticles for enhancing visible light photocatalytic activity

Titanium dioxide − bismuth tungstate composite materials were prepared by pulsed DC reactive magnetron sputtering of bismuth and tungsten metallic targets in argon/oxygen atmosphere onto anatase and rutile titania nanoparticles. The use of an oscillating bowl placed beneath the two magnetrons arranged in a co-planar closed field configuration enabled the deposition of bismuth tungstate onto loose powders, rather than a solid substrate. The atomic ratio of the bismuth/tungsten coatings was controlled by varying the power applied to each target. The effect of the bismuth tungstate coatings on the phase, optical and photocatalytic properties of titania was investigated by X-ray diffraction, energy-dispersive X-ray spectroscopy (EDX), Brunauer–Emmett–Teller (BET) surface area measurements, transmission electron microscopy (TEM), UV–vis diffuse reflectance spectroscopy and an acetone degradation test. The latter involved measurements of the rate of CO2 evolution under visible light irradiation of the photocatalysts, which indicated that the deposition of bismuth tungstate resulted in a significant enhancement of visible light activity, for both anatase and rutile titania particles. The best results were achieved for coatings with a bismuth to tungsten atomic ratio of 2:1. In addition, the mechanism by which the photocatalytic activity of the TiO2 nanoparticles was enhanced by compounding it with bismuth tungstate was studied by microwave cavity perturbation. The results of these tests confirmed that such enhancement of the photocatalytic properties is due to more efficient photogenerated charge carrier separation, as well as to the contribution of the intrinsic photocatalytic properties of Bi2WO6

The denture microbiome in health and disease: an exploration of a unique community

The United Nations suggests the global population of denture wearers (an artificial device that acts as a replacement for teeth) is likely to rise significantly by the year 2050. Dentures become colonized by microbial biofilms, the composition of which is influenced by complex factors such as patient’s age and health, and the nature of the denture material. Since colonization (and subsequent biofilm formation) by some micro-organisms can significantly impact the health of the denture wearer, the study of denture microbiology has long been of interest to researchers. The specific local and systemic health risks of denture plaque are different from those of dental plaque, particularly with respect to the presence of the opportunist pathogen Candida albicans and various other nonoral opportunists. Here, we reflect on advancements in our understanding of the relationship between micro-organisms, dentures, and the host, and highlight how our growing knowledge of the microbiome, biofilms, and novel antimicrobial technologies may better inform diagnosis, treatment, and prevention of denture-associated infections, thereby enhancing the quality and longevity of denture wearers

Application of Cu-FAU nanozeolites for decontamination of surfaces soiled with the ESKAPE pathogens

Antimicrobial resistance is a global threat with catastrophic forecasts in terms of human and economic losses. The so-called ESKAPE pathogens (Enterococcus species, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumanii, Pseudomonas aeruginosa and Enterobacter species) represent a range of species of particular concern because they cause many serious hospital infections, and can show resistance toward available commercial antibiotics. Copper-containing zeolite nanocrystals (10e30 nm) with FAU-type structure (Cu-FAU), in the form of stable colloidal suspensions, were prepared at high yield in the absence of organic templates and studied for their activity against ESKAPE microorganisms. The materials were active against all six ESKAPE species. The survival of Staphylococcus aureus, Klebsiella pneumoniae and Pseudomonas aeruginosa on stainless-steel coupons after direct treatment with the CuFAU zeolite suspensions was determined quantitatively. Complete decontamination (5-log reduction in bacterial counts) was achieved within 20 min for P. aeruginosa, and within 10 min for the K. pneumoniae and S. aureus. This result is significant, particularly for sanitization of surfaces in healthcare settings, with the potential to initiate a new direction of research to help address the global antimicrobial resistance threat

Comparative study of nano-ZSM-5 catalysts synthesized in OH- and F- media

This study reports the seeded synthesis of MFI-type (ZSM-5) zeolite in fluoride medium at pH = 8.5. Crystal growth kinetics of the resulting zeolite (ZSM-5-F) as a function of seed content and crystallization temperature is studied. The crystallization time is reduced to 1.5 h and crystals with sizes below 200 nm and a Si/Al ratio of 23.6 are obtained. A zeolite with similar characteristics but synthesized in a hydroxyl medium (ZSM-5-OH) is used to evaluate ZSM-5s synthesized in different crystallization media. Their physicochemical properties are compared and particular attention is paid to the nature, number, and distribution of silanol sites. The two zeolites exhibit similar number of Brφnsted acid sites; however the material synthesized in a hydroxyl medium contains a substantially larger number of surface and internal silanols that impact significantly its catalytic performance in methanol to hydrocarbon transformation. While the two materials exhibit similar selectivity in methanol transformations, the catalyst synthesized in fluoride medium shows superior activity and resistance to deactivation. The results suggest that seeded synthesis in a fluoride medium can be used for the preparation of superior zeolite catalysts

Toxicity and Antimicrobial Properties of ZnO@ZIF‑8 Embedded Silicone against Planktonic and Biofilm Catheter-Associated Pathogens

A ZnO@ZIF-8 powder on a gram scale was prepared via treatment of ZIF-8 with silver nitrate to induce spontaneous formation of ZnO nanorods on the surface of the ZIF-8 crystals. The crystal structure, phase purity, and physicochemical characteristics of ZnO@ZIF-8 were determined by X-ray diffraction, high-resolution electron microscopy, energy-dispersive spectroscopy, and nitrogen adsorption. The antimicrobial potential of ZnO@ZIF-8 for reduction of microorganisms often implicated with catheter-associated urinary tract infections (CAUTIs) was studied in detail using four target pathogens, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, and Staphylococcus aureus. The ability of the compound to kill all four microorganisms in suspension was established, and a minimum bactericidal concentration of 0.25 mg mL−1 was determined for each microorganism. ZnO@ZIF-8 compound was found to be no more toxic to Galleria mellonella than distilled water, which was assessed by injection of Galleria with 10 μL of ZnO@ZIF-8 of concentrations of up to 2 mg mL−1. ZnO@ZIF-8 suspensions (2 mg mL−1 concentration) were able to reduce well-established biofilms of all four organisms containing between 107 and 109 CFU mL−1 to below limit of detection (BLD) over a 24 h period. Silicone-embedded ZnO@ZIF-8 (2 or 4 wt % ZnO@ZIF-8 loading) also demonstrated antimicrobial properties with all four microorganisms being eliminated from the surface within 24 h. The ZnO@ZIF-8 high potency and rapid antibiofilm activity against all four test organisms coupled with its nontoxicity offer a new avenue for control of microbial colonization of catheters, which would ultimately result in reduction of CAUTIs