Formamidinium Lead Halide Perovskite Nanocomposite Scintillators.

While there is great demand for effective, affordable radiation detectors in various applications, many commonly used scintillators have major drawbacks. Conventional inorganic scintillators have a fixed emission wavelength and require expensive, high-temperature synthesis; plastic scintillators, while fast, inexpensive, and robust, have low atomic numbers, limiting their X-ray stopping power. Formamidinium lead halide perovskite nanocrystals show promise as scintillators due to their high X-ray attenuation coefficient and bright luminescence. Here, we used a room-temperature, solution-growth method to produce mixed-halide FAPbX3 (X = Cl, Br) nanocrystals with emission wavelengths that can be varied between 403 and 531 nm via adjustments to the halide ratio. The substitution of bromine for increasing amounts of chlorine resulted in violet emission with faster lifetimes, while larger proportions of bromine resulted in green emission with increased luminescence intensity. By loading FAPbBr3 nanocrystals into a PVT-based plastic scintillator matrix, we produced 1 mm-thick nanocomposite scintillators, which have brighter luminescence than the PVT-based plastic scintillator alone. While nanocomposites such as these are often opaque due to optical scattering from aggregates of the nanoparticles, we used a surface modification technique to improve transmission through the composites. A composite of FAPbBr3 nanocrystals encapsulated in inert PMMA produced even stronger luminescence, with intensity 3.8× greater than a comparative FAPbBr3/plastic scintillator composite. However, the luminescence decay time of the FAPbBr3/PMMA composite was more than 3× slower than that of the FAPbBr3/plastic scintillator composite. We also demonstrate the potential of these lead halide perovskite nanocomposite scintillators for low-cost X-ray imaging applications.

Tyre wear particles: an abundant yet widely unreported microplastic?

Owing to their physical and chemical properties, particles generated by the abrasion of tyre tread against road surfaces, or tyre wear particles, are recognised as microplastics. Recent desk-based studies suggest tyre wear to be a major contributor of microplastic emissions to the environment. This study aimed to quantify tyre wear in roadside drains and the natural environment near to a major road intersection. Tyre particles were identified by visual identification and a subsample confirmed as tyre wear by GC-MS using N-cyclohexyl-2-benzothiazolamine (NCBA) as a marker. The abundance of tyre wear within roadside drains was greater in areas associated with increased braking and accelerating than that with high traffic densities (p = < 0.05). Tyre particle abundance in the natural environment ranged from 0.6 ± 0.33 to 65 ± 7.36 in 5 mL of material, with some evidence of decline with distance from the road. This study offers preliminary data regarding the generation and abundance of this under-researched microplastic.

Tissue Distribution of Radiolabeled 110mAg Nanoparticles in Fish: Arctic Charr (Salvelinus alpinus).

This study presents the first whole-body tissue distributions of dissolved (AgI) and 20 nm silver nanoparticles (Ag0NPs20) in fish (Arctic charr, Salvelinus alpinus). The distributions are provided for fish exposed to three different treatments: (i) intravenous (IV), (ii) dietary, and (iii) waterborne. Quantitative whole-body autoradiography (QWBA) analyses obtained on high-resolution images reveal distinct silver distribution patterns according to the treatments. The IV exposures showed that AgNPs20 were mainly located in bile and kidney after 8 d, while AgI was distributed through the whole body and reached particular tissues such as bones, eyes, skin, liver, spleen, kidney, and intestine. The Ag0NPs20 distribution with the dietary exposures suggests that some dissolution occurred within fish organs. We propose that dissolved silver could later precipitate as chloride, sulfide, or selenide and be incorporated in bones during the growth. Consequently, it is yet difficult to state if Ag0NPs20 cross biological barriers. Finally, the waterborne exposures revealed that the gills can capture Ag0NPs20, but in small quantities. This suggests that the stability of Ag0NPs20 in water is critical for the uptake via the gills.

Uptake, Whole-Body Distribution, and Depuration of Nanoplastics by the Scallop Pecten maximus at Environmentally Realistic Concentrations.

Previous studies of uptake and effects of nanoplastics by marine organisms have been conducted at what may be unrealistically high concentrations. This is a consequence of the analytical challenges in tracking plastic particles in organisms at environmentally relevant concentrations and highlights the need for new approaches. Here, we present pulse exposures of 14C-radiolabeled nanopolystyrene to a commercially important mollusk, Pecten maximus, at what have been predicted to be environmentally relevant concentrations (<15 µg L-1). Uptake was rapid and was greater for 24 nm than for 250 nm particles. After 6 h, autoradiography showed accumulation of 250 nm nanoplastics in the intestine, while 24 nm particles were dispersed throughout the whole-body, possibly indicating some translocation across epithelial membranes. However, depuration was also relatively rapid for both sizes; 24 nm particles were no longer detectable after 14 days, although some 250 nm particles were still detectable after 48 days. Particle size thus apparently influenced the biokinetics and suggests a need for chronic exposure studies. Modeling extrapolations indicated that it could take 300 days of continued environmental exposure for uptake to reach equilibrium in scallop body tissues although the concentrations would still below 2.7 mg g-1. Comparison with previous work in which scallops were exposed to nonplastic (silver) nanomaterials of similar size (20 nm), suggests that nanoparticle composition may also influence the uptake tissue distributions somewhat.

Application of nuclear techniques to environmental plastics research.

Plastic pollution is ubiquitous in aquatic environments and its potential impacts to wildlife and humans present a growing global concern. Despite recent efforts in understanding environmental impacts associated with plastic pollution, considerable uncertainties still exist regarding the true risks of nano- and micro-sized plastics (<5 mm). The challenges faced in this field largely relate to the methodological and analytical limitations associated with studying plastic debris at low (environmentally relevant) concentrations. The present paper highlights how radiotracing techniques that are commonly applied to trace the fate and behaviour of chemicals and particles in various systems, can contribute towards addressing several important and outstanding questions in environmental plastic pollution research. Specifically, we discuss the use of radiolabeled microplastics and/or chemicals for 1) determining sorption/desorption kinetics of a range of contaminants to different types of plastics under varying conditions, 2) understanding the influence of microplastics on contaminant and nutrient bioaccumulation in aquatic organisms, and 3) assessing biokinetics, biodistribution, trophic transfer and potential biological impacts of microplastic at realistic concentrations. Radiotracer techniques are uniquely suited for this research because of their sensitivity, accuracy and capacity to measure relevant parameters over time. Obtaining precise and timely information on the fate of plastic particles and co-contaminants in wildlife has widespread applications towards effective monitoring programmes and environmental management strategies.

Robust Method Using Online Steric Exclusion Chromatography-Ultraviolet-Inductively Coupled Plasma Mass Spectrometry To Investigate Nanoparticle Fate and Behavior in Environmental Samples.

The foundation of nanoscience is that the properties of materials change as a function of their physical dimensions, and nanotechnology exploits this premise by applying selected property modifications for a specific benefit. However, to investigate the fate and effect of the engineered nanoparticles on toxic metal (TM) mobility, the analytical limitations in a natural environment remain a critical problem to overcome. Recently, a new generation of size exclusion chromatography (SEC) columns developed with spherical silica is available for pore sizes between 5 and 400 nm, allowing the analysis of nanoparticles. In this study, these columns were applied to the analysis of metal-based nanoparticles in environmental and artificial samples. The new method allows quantitative measurements of the interactions among nanoparticles, organic matter, and metals. Moreover, because of the new nanoscale SEC, our method allows the study of these interactions for different size ranges of nanoparticles and weights of organic molecules with a precision of 1.2 × 10(-2) kDa. The method was successfully applied to the study of nanomagnetite spiked in complex matrixes, such as sewage sludge, groundwater, tap water, and different artificial samples containing Leonardite humic acid and different toxic metals (i.e., As, Pb, Th). Finally, our results showed that different types of interactions, such as adsorption, stabilization, and/or destabilization of nanomagnetite could be observed using this new method.

Interactions between natural organic matter, sulfur, arsenic and iron oxides in re-oxidation compounds within riparian wetlands: nanoSIMS and X-ray adsorption spectroscopy evidences.

Arsenic (As) is a toxic and ubiquitous element which can be responsible for severe health problems. Recently, Nano-scale Secondary Ions Mass Spectrometry (nanoSIMS) analysis has been used to map organomineral assemblages. Here, we present a method adapted from Belzile et al. (1989) to collect freshly precipitated compounds of the re-oxidation period in a natural wetland environment using a polytetrafluoroethylene (PTFE) sheet scavenger. This method provides information on the bulk samples and on the specific interactions between metals (i.e. As) and the natural organic matter (NOM). Our method allows producing nanoSIMS imaging on natural colloid precipitates, including (75)As(-), (56)Fe(16)O(-), sulfur ((32)S(-)) and organic matter ((12)C(14)N) and to measure X-ray adsorption of sulfur (S) K-edge. A first statistical treatment on the nanoSIMS images highlights two main colocalizations: (1) (12)C(14)N(-), (32)S(-), (56)Fe(16)O(-) and (75)As(-), and (2) (12)C(14)N(-), (32)S(-) and (75)As(-). Principal component analyses (PCAs) support the importance of sulfur in the two main colocalizations firstly evidenced. The first component explains 70% of the variance in the distribution of the elements and is highly correlated with the presence of (32)S(-). The second component explains 20% of the variance and is highly correlated with the presence of (12)C(14)N(-). The X-ray adsorption near edge spectroscopy (XANES) on sulfur speciation provides a quantification of the organic (55%) and inorganic (45%) sulfur compositions. The co-existence of reduced and oxidized S forms might be attributed to a slow NOM kinetic oxidation process. Thus, a direct interaction between As and NOM through sulfur groups might be possible.

Tissue distribution and kinetics of dissolved and nanoparticulate silver in Iceland scallop (Chlamys islandica).

The fast expansion of the global nanotechnology market entails a higher environmental and human exposure to nanomaterials. Silver nanoparticles (AgNP) are used for their antibacterial properties; however, their environmental fate is yet poorly understood. Iceland scallops (Chlamys islandica) were exposed for 12 h to three different silver forms, dissolved Ag(I) (Agdiss), small (S-NP, Ø = 10-20 nm) and large AgNP (L-NP, Ø = 70-80 nm), labeled with (110m)Ag, and bioaccumulation kinetics and tissue distribution using in vivo gamma counting and whole-body autoradiography were determined. All Ag forms were readily and rapidly accumulated. Elimination process was also fast and bi-exponential, with mean biological half-life ranging from 1.4 to 4.3 days and from 17 to 50 days for fast and slow compartments, respectively. Most of the radioactivity concentrated in the hepatopancreas. Agdiss and S-NP tissue distributions were similar indicating a rapid dissolution of the latter in the tissues, contrarily to L-NP which appeared to form long lasting aggregates in the digestive system. Estimated steady-state bioconcentration factors (BCF), ranging between 2700 and 3800 ml g(-1) for dissolved and particulate silver forms, showed that C. islandica can accumulate significant quantities of Ag in a short time followed by an efficient depuration process.

Synthesis and characterization of [(110m)Ag]-nanoparticles with application to whole-body autoradiography of aquatic organisms.

Silver nanoparticles (AgNp) were synthesized using aqueous solution of silver nitrate ([(110m)Ag]NO3) with poly(allylamine) as a reducing agent and a stabilizer of the AgNp suspension. Nanoparticles were characterized by absorption spectroscopy, particle size analysis, atomic force microscopy (AFM), and transmission (TEM) electron microscopy. Different size nanoparticles (10-30 nm and 70-90 nm) were obtained by varying the polymer concentration and reaction time. The application of [(110m)Ag]AgNP to environmental studies, using nuclear techniques such as in vivo gamma counting and whole-body autoradiography, is demonstrated and discussed.