Every step of microplastic analysis (collection, extraction and characterization) is time-consuming, representing an obstacle to the implementation of large scale monitoring. This study proposes a ...semi-automated Raman micro-spectroscopy method coupled to static image analysis that allows the screening of a large quantity of microplastic in a time-effective way with minimal machine operator intervention. The method was validated using 103 particles collected at the sea surface spiked with 7 standard plastics: morphological and chemical characterization of particles was performed in <3h. The method was then applied to a larger environmental sample (n=962 particles). The identification rate was 75% and significantly decreased as a function of particle size. Microplastics represented 71% of the identified particles and significant size differences were observed: polystyrene was mainly found in the 2–5mm range (59%), polyethylene in the 1–2mm range (40%) and polypropylene in the 0.335–1mm range (42%).
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•Semi-automated micro-spectroscopy Raman method coupled to static image analysis•Time-effective and reproducible method requiring minimum operator intervention•High particles identification rate (>70%)•Fast morphological and chemical characterization of environmental particles•Efficient method for microplastics monitoring in marine environment
The concentration and spatial distribution of microplastics in the Bay of Brest (Brittany, France) was investigated in two surveys. Surface water and sediment were sampled at nine locations in areas ...characterized by contrasting anthropic pressures, riverine influences or water mixing. Microplastics were categorized by their polymer type and size class. Microplastic contamination in surface water and sediment was dominated by polyethylene fragments (PE, 53–67%) followed by polypropylene (PP, 16–30%) and polystyrene (PS, 16–17%) microparticles. The presence of buoyant microplastics (PE, PP and PS) in sediment suggests the existence of physical and/or biological processes leading to vertical transfer of lightweight microplastics in the bay. In sediment (upper 5 cm), the percentage of particles identified by Raman micro-spectroscopy was lower (41%) than in surface water (79%) and may explain the apparent low concentration observed in this matrix (0.97 ± 2.08 MP kg−1 dry sediment). Mean microplastic concentration was 0.24 ± 0.35 MP m−3 in surface water. We suggest that the observed spatial MP distribution is related to proximity to urbanized areas and to hydrodynamics in the bay. A particle dispersal model was used to study the influence of hydrodynamics on surface microplastic distribution. The outputs of the model showed the presence of a transitional convergence zone in the centre of the bay during flood tide, where floating debris coming from the northern and southern parts of the bay tends to accumulate before being expelled from the bay. Further modelling work and observations integrating (i) the complex vertical motion of microplastics, and (ii) their point sources is required to better understand the fate of microplastics in such a complex coastal ecosystem.
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•Microplastics were detected throughout the Bay of Brest.•Dominance of polyethylene fragments both in surface water and sediment.•High spatial and temporal variations were observed.•Environmental pressures and hydrodynamics influenced microplastics distribution.•A convergence zone was observed despite no permanent accumulation structure.
First assessment of microplastic contamination in the Bay of Brest: buoyant polymer fragments dominated in both surface water and sediment; their distribution exhibited spatial and temporal variations related to hydrodynamic and anthropic factors.
The development of the optical bio-chemical sensing technology is an extremely important scientific and technological issue for diagnosis and monitoring of diseases, control of industrial processes, ...environmental detection of air and water pollutants. Owing to their distinctive features, chalcogenide amorphous thin films represent a keystone in the manufacture of middle infrared integrated optical devices for a sensitive detection of biological or environmental variations. Since the chalcogenide thin films characteristics, i.e. stoichiometric conformity, structure, roughness or optical properties can be affected by the growth process, the choice and control of the deposition method is crucial. An approach based on the experimental design is undoubtedly a way to be explored allowing fast optimization of chalcogenide film deposition by means of radio frequency sputtering process. Argon (Ar) pressure, working power and deposition time were selected as potentially the most influential factors among all possible. The experimental design analysis confirms the great influence of the Ar pressure on studied responses: chemical composition, refractive index in near-IR (1.55 µm) and middle infrared (6.3 and 7.7 µm), band-gap energy, deposition rate and surface roughness. Depending on the intended application and therefore desired thin film characteristics, mappings of the experimental design meaningfully help to select suitable deposition parameters.
Chalcogenide thin films (GeSe2)100−x(Sb2Se3)x (with x=10 and 50) were deposited by Radio-frequency (RF) magnetron sputtering. In order to study the impact of Ar pressure on the structure and the ...composition of selenide thin films structural properties of thin films and targets were investigated by means of Raman scattering spectroscopy and X-ray photoelectron spectroscopy (XPS). Under low pressure (5·10−3mbar), the increase of wrong bonds like Ge(Sb)-Ge(Sb) was confirmed by Raman and also XPS for both composition. The observed structural changes with Ar pressure are linked with modification of the composition of the selenide films analyzed by EDS and XPS. Furthermore for higher Ar pressure (5·10−2mbar), RF sputtered thin film and target structure present a great similarity. These differences driven by Ar pressure modification are probably related to distinctive sputtering rate and mean free path of the particles ejected from target for the different Ar pressures.
•(GeSe2)100−x(Sb2Se3)x thin films were deposited by RF magnetron sputtering.•Structural properties of thin films were studied by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS).•Proportion of M-M bonds (M=Ge, Sb) decreases for higher Ar pressure.•Thin films structure and composition are closer to the glass target for higher Ar pressure.
While the geometry of aerospace assemblies is carefully controlled, for many industrial applications such as marine structures bond line thickness can vary significantly. In this study epoxy adhesive ...joints of different thicknesses between aluminium substrates have been characterized using physico-chemical analyses (differential scanning calorimetry, DSC; dynamic mechanical analysis, DMA; spectroscopy), nano-indentation and mechanical testing. Thermal analyses indicated no influence of thickness on structure. Nano-indentation revealed no evidence of an interphase at the metal/epoxy interface, nor any change in modulus for different thicknesses, though Raman spectroscopy suggested there may be slight variations in composition close to the substrates. However, mechanical testing using the modified Arcan fixture indicated a significant drop in strength and failure strain under pure tension and a smaller reduction for tension/shear and pure shear loads as thickness increased. Examination of sections through joints did not indicate any physical reason for this, but numerical analysis of the stress state revealed larger stress concentration factors for tensile loading in thick joints, which may explain the thickness effect. It is recommended that joint thickness should be kept below 0.8
mm to avoid obtaining artificially low values with the Arcan test.
In this article, we propose a new strategy to build a sensor for easy handling and rapid analysis on-site. Our sensor is based on the combination of surface-enhanced Raman spectroscopy (SERS) and ...molecularly imprinted polymers (MIPs). SERS provides a strong sensitivity for the detection of trace molecules while MIPs offer a highly selective and specific recognition platform. The research presented here focuses on the detection of the interaction between a robust ultra-thin layer of MIPs and of paracetamol, the targeted molecule. This drug is an environmental emerging pollutant, i.e., a molecule whose presence and significance have not yet been elucidated, which gives rise to health and environmental concerns. The results are a combined analysis of the SERS spectra and a multivariate analysis. The former provides a clear demonstration of the evolution of the MIP-nanostructure interaction when the concentration of paracetamol increases. The statistical analysis produces the proof of the selectivity of the sensor.
The development of infrared sensing platform requires adapted materials. In this work, we used sputtered gold nanoparticles on a chalcogenide glass to demonstrate that these infrared materials can be ...used as substrate for surface enhanced infrared absorption (SEIRA) spectroscopy. The sputtering parameters were optimized to get the highest possible enhancement. To assess it, a self-assembled monolayer of 4-nitrothiophenol was used. These preliminary results are promising and pave the way for various configurations of waveguide for integrated optical components.
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