Photoinduced edge-specific nanoparticle decoration of two-dimensional tungsten diselenide nanoribbons

Metallic nanoparticles are widely explored for boosting light-matter coupling, optoelectronic response, and improving photocatalytic performance of two-dimensional (2D) materials. However, the target area is restricted to either top or bottom of the 2D flakes. Here, we introduce an approach for edge-specific nanoparticle decoration via light-assisted reduction of silver ions and merging of silver seeds. We observe arrays of the self-limited in size silver nanoparticles along tungsten diselenide WSe2 nanoribbon edges. The density of nanoparticles is tunable by adjusting the laser fluence. Scanning electron microscopy, atomic force microscopy, and Raman spectroscopy are used to investigate the size, distribution, and photo-response of the deposited plasmonic nanoparticles on the quasi-one-dimensional nanoribbons. We report an on-surface synthesis path for creating mixed-dimensional heterostructures and heterojunctions with potential applications in opto-electronics, plasmonics, and catalysis, offering improved light matter coupling, optoelectronics response, and photocatalytic performance of 2D materials.

Bio-Polyester/Rubber Compounds: Fabrication, Characterization, and Biodegradation

Biobased and biodegradable polymers (BBDs) such as poly(3-hydroxy-butyrate), PHB, and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) are considered attractive alternatives to fossil-based plastic materials since they are more environmentally friendly. One major problem with these compounds is their high crystallinity and brittleness. In order to generate softer materials without using fossil-based plasticizers, the suitability of natural rubber (NR) as an impact modifier was investigated in PHBV blends. Mixtures with varying proportions of NR and PHBV were generated, and samples were prepared by mechanical mixing (roll mixer and/or internal mixer) and cured by radical C-C crosslinking. The obtained specimens were investigated with respect to their chemical and physical characteristics, applying a variety of different methods such as size exclusion chromatography, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermal analysis, XRD, and mechanical testing. Our results clearly indicate that NR-PHBV blends exhibit excellent material characteristics including high elasticity and durability. Additionally, biodegradability was tested by applying heterologously produced and purified depolymerases. pH shift assays and morphology analyses of the surface of depolymerase-treated NR-PHBV through electron scanning microscopy confirmed the enzymatic degradation of PHBV. Altogether, we prove that NR is highly suitable to substitute fossil-based plasticizers; NR-PHBV blends are biodegradable and, hence, should be considered as interesting materials for a great number of applications.

Determination of ragweed allergen Amb a 1 distribution in aerosols using ELISA and immunogold scanning electron microscopy

Background

Ragweed as an invasive species in Europe has become more important for allergy sufferers in the last decade. Because pollen fractions can be found in the respirable fraction of aerosols, they can generate severe disease progressions.

Objective

To obtain information about the concentration and distribution of 1 of the main ragweed allergens Ambrosia artemisiifolia 1 in the air of Vienna, PM10 and PM2.5 fine dust filters were analyzed.

Methods

Standard fine dust filters used for air quality monitoring were analyzed via ELISA and immunogold scanning electron microscopy.

Results

Via ELISA it was possible to show that already at pollen season start in August a recognizably high A artemisiifolia 1 concentration can be found. In addition, the allergen concentration in the air stays comparatively high after the peak season has ended even when the pollen concentration drops to a moderate level. The immunogold electron microscopy investigation directly applied on filters shows that the allergen can be found on organic as well as on mixtures of organic and inorganic particles. A first semistatistical analysis of the labeled particle sizes indicates that a large number of the allergen carriers can be found within the smallest particle size range. Nevertheless, further investigations are needed to obtain enough particle counts for a significant statistical analysis.

Conclusions

It was possible to show that reliable results can be obtained from ELISA and immunogold scanning electron microscopy directly applied on filters that are used in air quality monitoring sites. By adaptation of the used protocols, it should be possible to obtain respective information about further allergens.

Correlative SEM-Raman microscopy to reveal nanoplastics in complex environments

Nowadays "microplastics" (MPs) is an already well-known term and results of micro-sized particles found in consumer products or environments are regularly reported. However, studies of native MPs smaller than 1 μm, often referred to as nanoplastics (NPs), in analytically challenging environments are rare. In this study, a correlative approach between scanning electron microscopy and Raman microscopy is tested to meet the challenges of finding and identifying NPs in the 100 nm range in various environments, ranging from ideal (distilled water) to challenging (sea salt, human amniotic fluid). To test the viability of this approach in principle, standardized polystyrene beads (Ø 200 nm) are mixed into the various environments in different concentrations. Promising detection limits of 2 10^-3 μg/L (distilled water), 20 μg/L (sea salt) and 200 μg/L (human amniotic fluid) are found. To test the approach in practices both sea salt and amniotic fluid are analysed for native NPs as well. Interestingly a nylon-NP was found in the amniotic fluid, maybe originating from the sampling device. However, the practical test reveals limitations, especially with regard to the reliable identification of unknown NPs by Raman microscopy, due to strong background signals from the environments. We conclude from this in combination with the excellent performance in distilled water that a combination of this approach with an advanced sample preparation technique would yield a powerful tool for the analysis of NPs in various environments.

Removal of Barium from Solution by Natural and Iron(III) Oxide-Modified Allophane, Beidellite and Zeolite Adsorbents

Efficient capture of barium (Ba) from solution is a serious task in environmental protection and remediation. Herein, the capacity and the mechanism of Ba adsorption by natural and iron(III) oxide (FeO) modified allophane (ALO), beidellite (BEI) and zeolite (ZEO) were investigated by considering the effects of contact time, temperature, pH, Ba2+ concentration, adsorbent dosage, the presence of competitive ions and adsorption-desorption cycles (regenerability). Physicochemical and mineralogical properties of the adsorbents were characterized by XRD, FTIR, SEM with EDX and N2 physisorption techniques. The Ba2+ adsorption fitted to a pseudo-first-order reaction kinetics, where equilibrium conditions were reached within <30 min. BEI, ALO and ZEO with(out) FeO-modification yielded removal efficiencies for Ba2+ of up to 99.9%, 97% and 22% at optimum pH (pH 7.5-8.0). Adsorption isotherms fitted to the Langmuir model, which revealed the highest adsorption capacities for BEI and FeO-BEI (44.8 mg/g and 38.6 mg/g at 313 K). Preferential ion uptake followed in the order: Ba2+ > K+ > Ca2+ >> Mg2+ for all adsorbents; however, BEI and FeO-BEI showed the highest selectivity for Ba2+ among all materials tested. Barium removal from solution was governed by physical adsorption besides ion exchange, intercalation, surface complexation and precipitation, depending mainly on the absorbent type and operational conditions. BEI and FeO-BEI showed a high regenerability (>70-80% desorption efficiency after 5 cycles) and could be considered as efficient sorbent materials for wastewater clean-up.

Scale deposits in tunnel drainage systems - A study on fabrics and formation mechanisms

Rapid deposition of chemical sediments, particularly calcium carbonate, is a widespread phenomenon in tunnel constructions, which can significantly disturb water draining. The removal of the scale deposits in the drainage setting is labor and cost intensive. Prediction or prevention of these unwanted scale deposits are challenging and require detailed knowledge on their site-specific source, formation mechanisms and environmental dependencies. This case study combines a mineralogical, (micro)structural, isotopic, microbiological, and hydrochemical approach to understand the formation of scale deposits in an Austrian motorway tunnel. Chemical and isotopic results revealed that all investigated solutions originate from a distinct local aquifer. High pH (11), indicative high alkaline element concentrations (Na 26 mg/l; K 67 mg/l), originated from concrete leaching, and a strong supersaturation in respect to calcite (SI > 1) are representative for the environmental setting of scaling type 1. This type is characterized by the formation of calcite, aragonite, and rarely documented dypingite (Mg₅(CO₃)₄(OH)₂*5H₂O), and yields in a highly porous material showing minor indications of microbial presence. In contrast, scale deposits of type 2 are strongly microbially influenced, yielding dense and layered mineral deposits, typically consisting of calcite. The corresponding aqueous solution revealed elevated Mg concentration (38 mg/l) and a high molar Mg/Ca ratio (0.8). Scale deposits containing distinct aragonite precipitates next to calcite, mostly growing in pore spaces of the scale fabric, are accounted as type 3. Therein, dypingite is always growing on top of aragonite needles, indicative for prior CaCO₃ precipitation. The composition of corresponding solutions shows the highest Mg/Ca ratio (1.1). Scale type 4 is characterized as a compact deposit consisting entirely of calcite. Its corresponding solution exhibits a molar Mg/Ca ratio of 0.6. From the obtained data sets a conceptual model was developed describing the distinct operative and (micro)environmental conditions responsible for the distinct diversity of scale deposits.

[Hospital surveillance during major outbreaks of community-acquired diseases. Pandemic Influenza Hospital Surveillance (PIKS) 2009/2010 and Surveillance of Bloody Diarrhea (SBD) 2011]

BACKGROUND AND OBJECTIVE

During the influenza pandemic 2009/2010 and the outbreak of entero-haemorrhagic Escherichia coli (EHEC)/hemolytic-uremic syndrome (HUS) 2011, the statutory reporting system in Germany was complemented by additional event-related surveillance systems in hospitals. The Pandemic Influenza Hospital Surveillance (PIKS) and the Surveillance of Bloody Diarrhea (SBD) were evaluated, to make experiences available for similar future situations.

METHODS

The description and evaluation of our surveillance systems is based on the "Updated Guidelines for Evaluating Public Health Surveillance Systems" published by the U.S. Centers for Disease Control and Prevention in 2001.

RESULTS

PIKS and SBD could be implemented quickly and were able to capture resilient data in a timely manner both on the severity and course of the influenza pandemic 2009/2010 and the outbreak of EHEC and HUS 2011. Although lacking in representativeness, sensitive and useful data were generated.

CONCLUSION

In large outbreaks of severe diseases, the establishment of specific hospital surveillance should be considered as early as possible. In Germany, the participating hospitals were able to rapidly implement the required measures.

Enhanced surveillance during a large outbreak of bloody diarrhoea and haemolytic uraemic syndrome caused by Shiga toxin/verotoxin-producing Escherichia coli in Germany, May to June 2011

Germany has a well established broad statutory surveillance system for infectious diseases. In the context of the current outbreak of bloody diarrhoea and haemolytic uraemic syndrome caused by Shiga toxin/ verotoxin-producing Escherichia coli in Germany it became clear that the provisions of the routine surveillance system were not sufficient for an adequate response. This article describes the timeline and concepts of the enhanced surveillance implemented during this public health emergency.