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  • Philippe, Allan  (11)
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  • 1
    Language: English
    In: Analytical chemistry, 19 November 2013, Vol.85(22), pp.10643-7
    Description: Studying the environmental fate of engineered or natural colloids requires efficient methods for measuring their size and quantifying them in the environment. For example, an ideal method should maintain its correctness, accuracy, reproducibility, and robustness when applied to samples contained in complex matrixes and distinguish the target particles from the natural colloidal background signals. Since it is expected that a large portion of nanoparticles will form homo- or heteroagglomerates when released into environmental media, it is necessary to differentiate agglomerates from primary particles. At present, most sizing techniques do not fulfill these requirements. In this study, we used online coupling of two promising complementary sizing techniques: hydrodynamic chromatography (HDC) and single-particle ICPMS analysis to analyze gold nanoparticles agglomerated under controlled conditions. We used the single-particle mode of the ICPMS detector to detect single particles eluted from an HDC-column and determine a mass and an effective diameter for each particle using a double calibration approach. The average agglomerate relative density and fractal dimension were calculated using these data and used to follow the morphological evolution of agglomerates over time during the agglomeration process. The results demonstrate the ability of HDC coupled to single-particle analysis to identify and characterize nanoparticle homoagglomerates and is a very promising technique for the analysis of colloids in complex media.
    Keywords: Nanopartikel ; Einzelpartikel ; Chromatographie ; Partikelanalyse ; Eichen (Abgleichen) ; Agglomerieren ; Fraktale Dimension ; Kolloid ; Gold ; Basis (Grundlage) ; Agglomerat ; Flankendurchmesser ; Massenspektrometrie Mit Induktiv Gekoppeltem Plasma ; Engineering ; Chemistry;
    ISSN: 00032700
    E-ISSN: 1520-6882
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  • 2
    Language: English
    In: The Science of the Total Environment, Dec 1, 2015, Vol.535, p.35(10)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.scitotenv.2014.11.058 Byline: George Metreveli, Allan Philippe, Gabriele E. Schaumann Abstract: Silver nanoparticles (Ag NPs) could be found in aquatic systems in the near future. Although the interplay between aggregate formation and disaggregation is an important factor for mobility, bioavailability and toxicity of Ag NPs in surface waters, the factors controlling disaggregation of Ag NP homoaggregates are still unknown. In this study, we investigated the reversibility of homoaggregation of citrate coated Ag NPs in a Rhine River water matrix. We characterized the disaggregation of Ag NP homoaggregates by ionic strength reduction and addition of Suwannee River humic acid (SRHA) in the presence of strong and weak shear forces. In order to understand the disaggregation processes, we also studied the nature of homoaggregates and their formation dynamics under the influence of SRHA, Ca.sup.2+ concentration and nanoparticle concentration. Even in the presence of SRHA and at low particle concentrations (10[mu]gL.sup.-1), aggregates formed rapidly in filtered Rhine water. The critical coagulation concentration (CCC) of Ca.sup.2+ in reconstituted Rhine water was 1.5mmolL.sup.-1 and was shifted towards higher values in the presence of SRHA. Analysis of the attachment efficiency as a function of Ca.sup.2+ concentration showed that SRHA induces electrosteric stabilization at low Ca.sup.2+ concentrations and cation-bridging flocculation at high Ca.sup.2+ concentrations. Shear forces in the form of mechanical shaking or ultrasound were necessary for breaking the aggregates. Without ultrasound, SRHA also induced disaggregation, but it required several days to reach a stable size of dense aggregates still larger than the primary particles. Citrate stabilized Ag NPs may be in the form of reaction limited aggregates in aquatic systems similar to the Rhine River. The size and the structure of these aggregates will be dynamic and be determined by the solution conditions. Seasonal variations in the chemical composition of natural waters can result in a sedimentation-release cycle of engineered nanoparticles. Article History: Received 29 September 2014; Revised 16 November 2014; Accepted 16 November 2014
    Keywords: Water – Analysis ; Humic Acids – Analysis
    ISSN: 0048-9697
    Source: Cengage Learning, Inc.
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  • 3
    Language: English
    In: PLoS ONE, 01 January 2014, Vol.9(2), p.e90559
    Description: In this study, we evaluated hydrodynamic chromatography (HDC) coupled with inductively coupled plasma mass spectrometry (ICP-MS) for the analysis of nanoparticles in environmental samples. Using two commercially available columns (Polymer Labs-PDSA type 1 and 2), a set of well characterised calibrants and a new external time marking method, we showed that flow rate and eluent composition have few influence on the size resolution and, therefore, can be adapted to the sample particularity. Monitoring the agglomeration of polystyrene nanoparticles over time succeeded without observable disagglomeration suggesting that even weak agglomerates can be measured using HDC. Simultaneous determination of gold colloid concentration and size using ICP-MS detection was validated for elemental concentrations in the ppb range. HDC-ICP-MS was successfully applied to samples containing a high organic and ionic background. Indeed, online combination of UV-visible, fluorescence and ICP-MS detectors allowed distinguishing between organic molecules and inorganic colloids during the analysis of Ag nanoparticles in synthetic surface waters and TiO₂ and ZnO nanoparticles in commercial sunscreens. Taken together, our results demonstrate that HDC-ICP-MS is a flexible, sensitive and reliable method to measure the size and the concentration of inorganic colloids in complex media and suggest that there may be a promising future for the application of HDC in environmental science. Nonetheless the rigorous measurements of agglomerates and of matrices containing natural colloids still need to be studied in detail.
    Keywords: Sciences (General)
    E-ISSN: 1932-6203
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  • 4
    Language: English
    In: Science of the Total Environment, 01 December 2015, Vol.535, pp.35-44
    Description: Silver nanoparticles (Ag NPs) could be found in aquatic systems in the near future. Although the interplay between aggregate formation and disaggregation is an important factor for mobility, bioavailability and toxicity of Ag NPs in surface waters, the factors controlling disaggregation of Ag NP homoaggregates are still unknown. In this study, we investigated the reversibility of homoaggregation of citrate coated Ag NPs in a Rhine River water matrix. We characterized the disaggregation of Ag NP homoaggregates by ionic strength reduction and addition of Suwannee River humic acid (SRHA) in the presence of strong and weak shear forces. In order to understand the disaggregation processes, we also studied the nature of homoaggregates and their formation dynamics under the influence of SRHA, Ca concentration and nanoparticle concentration. Even in the presence of SRHA and at low particle concentrations (10 μg L ), aggregates formed rapidly in filtered Rhine water. The critical coagulation concentration (CCC) of Ca in reconstituted Rhine water was 1.5 mmol L and was shifted towards higher values in the presence of SRHA. Analysis of the attachment efficiency as a function of Ca concentration showed that SRHA induces electrosteric stabilization at low Ca concentrations and cation-bridging flocculation at high Ca concentrations. Shear forces in the form of mechanical shaking or ultrasound were necessary for breaking the aggregates. Without ultrasound, SRHA also induced disaggregation, but it required several days to reach a stable size of dense aggregates still larger than the primary particles. Citrate stabilized Ag NPs may be in the form of reaction limited aggregates in aquatic systems similar to the Rhine River. The size and the structure of these aggregates will be dynamic and be determined by the solution conditions. Seasonal variations in the chemical composition of natural waters can result in a sedimentation-release cycle of engineered nanoparticles.
    Keywords: Coagulation Kinetics ; Aggregation ; Disaggregation ; Dls ; Natural Organic Matter ; Icp-MS ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 5
    Language: English
    In: Science of the Total Environment, 01 December 2015, Vol.535, pp.3-19
    Description: Engineered inorganic nanoparticles (EINP) from consumers' products and industrial applications, especially silver and titanium dioxide nanoparticles (NP), are emitted into the aquatic and terrestrial environments in increasing amounts. However, the current knowledge on their environmental fate and biological effects is diverse and renders reliable predictions complicated. This review critically evaluates existing knowledge on colloidal aging mechanisms, biological functioning and transport of Ag NP and TiO NP in water and soil and it discusses challenges for concepts, experimental approaches and analytical methods in order to obtain a comprehensive understanding of the processes linking NP fate and effects. Ag NP undergo dissolution and oxidation with Ag S as a thermodynamically determined endpoint. Nonetheless, Ag NP also undergo colloidal transformations in the nanoparticulate state and may act as carriers for other substances. Ag NP and TiO NP can have adverse biological effects on organisms. Whereas Ag NP reveal higher colloidal stability and mobility, the efficiency of NOM as a stabilizing agent is greater towards TiO NP than towards Ag NP, and multivalent cations can dominate the colloidal behavior over NOM. Many of the past analytical obstacles have been overcome just recently. Single particle ICP-MS based methods in combination with field flow fractionation techniques and hydrodynamic chromatography have the potential to fill the gaps currently hampering a comprehensive understanding of fate and effects also at a low field relevant concentrations. These analytical developments will allow for mechanistically orientated research and transfer to a larger set of EINP. This includes separating processes driven by NP specific properties and bulk chemical properties, categorization of effect-triggering pathways directing the EINP effects towards specific recipients, and identification of dominant environmental parameters triggering fate and effect of EINP in specific ecosystems (e.g. soil, lake, or riverine systems).
    Keywords: Transport ; Aggregation ; Analytics ; Environment ; Aging ; Ecotoxicology ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 6
    Language: English
    In: Environmental science & technology, 19 August 2014, Vol.48(16), pp.8946-62
    Description: This contribution critically reviews the state of knowledge on interactions of natural colloids and engineered nanoparticles with natural dissolved organic materials (DOM). These interactions determine the behavior and impact of colloids in natural system. Humic substances, polysaccharides, and proteins present in natural waters adsorb onto the surface of most colloids. We outline major adsorption mechanisms and structures of adsorption layers reported in the literature and discuss their generality on the basis of particle type, DOM type, and media composition. Advanced characterization methods of both DOM and colloids are needed to address insufficiently understood aspects as DOM fractionation upon adsorption, adsorption reversibility, and effect of capping agent. Precise knowledge on adsorption layer helps in predicting the colloidal stability of the sorbent. While humic substances tend to decrease aggregation and deposition through electrostatic and steric effects, bridging-flocculation can occur in the presence of multivalent cations. In the presence of DOM, aggregation may become reversible and aggregate structure dynamic. Nonetheless, the role of shear forces is still poorly understood. If traditional approaches based on the DLVO-theory can be useful in specific cases, quantitative aggregation models taking into account DOM dynamics, bridging, and disaggregation are needed for a comprehensive modeling of colloids stability in natural media.
    Keywords: Humic Substances ; Colloids -- Chemistry ; Nanoparticles -- Chemistry ; Water Pollutants, Chemical -- Chemistry
    ISSN: 0013936X
    E-ISSN: 1520-5851
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  • 7
    Language: English
    In: Science of the Total Environment, 15 December 2018, Vol.645, pp.192-204
    Description: Riverbank filtration systems are important structures that ensure the cleaning of infiltrating surface water for drinking water production. In our study, we investigated the potential risk for a breakthrough of environmentally aged silver nanoparticles (Ag NP) through these systems. Additionally, we identified factors leading to the remobilization of Ag NP accumulated in surficial sediment layers in order to gain insights into remobilization mechanisms. We conducted column experiments with Ag NP in an outdoor pilot plant consisting of water-saturated sediment columns mimicking a riverbank filtration system. The NP had previously been aged in river water, soil extract, and ultrapure water, respectively. We investigated the depth-dependent breakthrough and retention of NP. In subsequent batch experiments, we studied the processes responsible for a remobilization of Ag NP retained in the upper 10 cm of the sediments, induced by ionic strength reduction, natural organic matter (NOM), and mechanical forces. We determined the amount of remobilized Ag by ICP-MS and differentiated between particulate and ionic Ag after remobilization using GFAAS. The presence of Ag-containing heteroaggregates was investigated by combining filtration with single-particle ICP-MS. Single and erratic Ag breakthrough events were mainly found in 30 cm depth and Ag NP were accumulated in the upper 20 cm of the columns. Soil-aged Ag NP showed the lowest retention of only 54%. Remobilization was induced by the reduction of ionic strength and the presence of NOM in combination with mechanical forces. The presence of calcium in the aging- as well as the remobilizing media reduced the remobilization potential. Silver NP were mainly remobilized as heteroaggregates with natural colloids, while dissolution played a minor role. Our study indicates that the breakthrough potential of Ag NP in riverbank filtration systems is generally low, but the aging in soil increases their mobility. Remobilization processes are associated to co-mobilization with natural colloids.
    Keywords: Heteroaggregation ; Nanoparticle Transformation ; Breakthrough ; Mobility ; Reversibility ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 8
    In: Environmental Science: Nano, 2016, Vol.3(2), pp.418-433
    Description: Understanding of the interplay of generally known colloidal transformations under conditions of test media (TM) used during cultivation of organisms and biological effect (=ecotoxicological) studies is still limited, although this knowledge is required for an adequate interpretation of test outcomes and for a comparison among different studies. In this context, we investigated the aggregation and dissolution dynamics of citrate-stabilized silver nanoparticles (Ag NPs) by varying the composition of three TM (ASTM, SAM-5S, and R2A, used during bioassays with Daphnia magna , Gammarus fossarum , and bacterial biofilms, respectively) in the presence and absence of two types of natural organic matter (NOM), namely, Suwanee River humic acid (SRHA) and seaweed extract (SW). Each original test medium induced reaction-limited aggregation of Ag NPs, and aggregation increased from R2A to SAM-5S and ASTM. In addition to the differences in aggregation dynamics, the concentration and speciation of Ag( i ) differed between the three TM, whereby SAM-5S and ASTM are comparable with respect to the nature of the aggregation process but clearly differ from the R2A medium. Furthermore, Cl , mainly present in SAM-5S, induced NP stabilization. The release of silver ions from Ag NPs was controlled by the presence of NOM and organic constituents of TM and by interactions with Cl and Br . The degree of aggregation, formation of interparticle cationNOM bridges or stabilization was larger for Ca 2+ than for Mg 2+ due to the stronger ability of Ca 2+ to interact with citrate or NOM compared to Mg 2+ . These observations and the dependence of aggregation rates on the particle concentration renders the interpretation of doseresponse relationships challenging, but they may open perspectives for targeted ecotoxicological testing by modifications of TM composition.
    Keywords: Bacteria ; Media ; Stabilization ; Concentration (Composition) ; Silver ; Nanoparticles ; Dynamics ; Agglomeration ; Chemical and Electrochemical Properties (MD) ; Chemical and Electrochemical Properties (Ep) ; Chemical and Electrochemical Properties (Ed) ; Chemical and Electrochemical Properties (EC);
    ISSN: 2051-8153
    E-ISSN: 2051-8161
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  • 9
    Language: English
    In: Journal of Nanoparticle Research, 2016, Vol.18(10), pp.1-10
    Description: CeO 2 nanoparticles with various characteristics find an increasing number of applications in the electronic, medical, and other industries and are therefore likely released in the environment. This calls for investigations linking the physicochemical properties of these particles with their potential environmental impacts. In this study, CeO 2 nanoparticle powders were prepared using three different precursors [Ce(NO 3 ) 3 , CeCl 3 , and Ce(CH 3 COO) 3 ] and annealing temperatures (300, 500, and 700 °C). This procedure resulted in nine different types of nanoparticles with differing size (5–90 nm), morphology, surface Ce 3+ /Ce 4+ ratio, and slightly different crystal structures as characterized using transmission electron microscopy, dynamic light scattering, X-ray photoelectron spectroscopy, and X-ray diffraction measurements with Rietveld refinement. These CeO 2 nanoparticles underwent toxicity testing at concentrations up to 64 mg L −1 using Daphnia magna . Toxic effects were observed for three particle types with EC50 values between 5 and 64 mg L −1 . No clear correlation was observed between the physicochemical properties (size, shape, oxygen occupancy, Ce 3+ /Ce 4+ ratio) of the nanoparticles and their toxicity. However, toxicity was correlated with the amount of Ce remaining suspended in the test medium after 24 h. This indicated that toxic effects may depend on the colloidal stability of CeO 2 nanoparticles during the first day of exposure. Therefore, being readily suspended and remaining stable for several days in the aquatic media increases the likelihood that CeO 2 nanoparticles will cause unwanted adverse effects.
    Keywords: CeO ; Ecotoxicity ; Daphnia magna ; XPS ; XRD ; Health and environmental effects
    ISSN: 1388-0764
    E-ISSN: 1572-896X
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  • 10
    Language: English
    In: Separations, 01 October 2018, Vol.5(4), p.50
    Description: An increasing amount of TiO2 engineered nanoparticles (TNP) is released into soils and sediments, increasing the need for dedicated detection methods. Titanium is naturally present in soils at concentrations typically much higher than the estimated concentrations for TNP. Therefore, a precise knowledge of this natural background, including the colloidal fraction, is required for developing adapted strategies for detecting TNP. In this study, we characterized the natural colloidal Ti-background by analyzing eight soils with different properties and origins. A combination of X-ray fluorescence analysis and ICP-OES was used for determining the silicate bound fraction, which was a minor fraction for all soils (0-32%). The colloidal fraction obtained by extracting colloids from soil prior to ICP-OES measurements ranged between 0.3% and 7%. Electron microscopy and hydrodynamic chromatography confirmed that Ti in the form of colloids or larger particles was mostly present as TiO2 minerals with a fraction smaller than 100 nm. The size distribution mode of the extracted colloids determined using hydrodynamic chromatography ranged between 80 and 120 nm. The chromatograms suggested a broad size distribution with a significant portion below 100 nm. In addition to these data, we also discuss possible implications of our findings for the method development for detecting TNP in soils.
    Keywords: Tio2 ; Extraction ; Soil ; Hydrodynamic Chromatography ; Icp-MS ; Natural Nanoparticles ; Chemistry
    E-ISSN: 2297-8739
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