| 1. |
- Degueldre, C., et al.
(författare)
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Gold colloid analysis by inductively coupled plasma-mass spectrometry in a single particle mode
- 2006
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 555:2, s. 263-268
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Tidskriftsartikel (refereegranskat)abstract
- Analysis in a single particle mode of gold colloids in water has been performed by inductively coupled plasma-mass spectrometry (ICP-MS). The signal induced by the flash of ions due to the ionization of a colloid in the plasma torch can be measured for the ions (197)An(+) by the mass spectrometer without interferences. The intensity of the MS signal is recorded in time scan. The recorded peak distributions were analysed as a function of the colloid size for five monodisperse colloids (80-250 nm). This study describes the experimental conditions to analyse gold colloids in a single particle mode. The size detection limit is around 25 nm corresponding to 0.15 fg colloids and one particle per ml may be detected during a 1 min time scan within standard procedure.
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| 2. |
- Degueldre, C., et al.
(författare)
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Investigations of clay colloid aggregates by scanning transmission X-ray microspectroscopy of suspensions
- 2009
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Ingår i: Applied Geochemistry. - : Elsevier BV. - 0883-2927 .- 1872-9134. ; 24:10, s. 2015-2018
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Tidskriftsartikel (refereegranskat)abstract
- The environmental behaviour of colloidal clay in aquatic systems is linked to the properties of their aggregates. Earlier investigations of clay colloids were performed with electron microscope techniques which caused de-hydration of the particles. Information on the structure of colloid aggregates is needed for understanding their sedimentation behaviour, as well as colloid contaminant transport properties in natural systems. Scanning transmission X-ray microspectroscopy successfully produced images of montmorillonite colloid aggregates in a pseudo-equilibrium state in 1 mM NaCl suspensions equilibrated for more than a year. These clay aggregates were revealed at photon energies below the O absorption edges of clay and water. They were spherical or ellipsoidal with diameters of the order of 100-800 nm. The aggregates are porous and gel like with lower densities than the clay mineral. These investigations are important for modelling the occurrence of clay aggregates in aqueous environments.
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| 3. |
- Degueldre, C., et al.
(författare)
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Uranium colloid analysis by single particle inductively coupled plasma-mass spectrometry
- 2006
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Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 68:3, s. 623-628
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Tidskriftsartikel (refereegranskat)abstract
- Uranium single particle analysis has been performed by inductively coupled plasma-mass spectrometry (ICP-MS) and the performances are compared with that provided by scanning electron microsopy and single particle counting. The transient signal induced by the flash of ions due to the ionisation of all titanium Colloidal particle in the plasma torch can be detected and measured for selected uranium ion masses (U-238(+), U-235(+) or 254[(UO)-U-238-O-16](+)) by the mass spectrometer. The signals recorded via time scanning are analysed as a function of particle size or fraction of the studied element or isotope in the colloid phase. The frequency of the flashes is directly proportional to the concentration of particles in the colloidal suspension. The feasibility tests were performed on uranium dioxide particles. The study also describes the experimental conditions and the choice of mass to detect uranium colloids in a single particle analysis mode.
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| 4. |
- García García, Sandra, et al.
(författare)
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Determining pseudo-equilibrium of montmorillonite colloids in generation and sedimentation experiments as a function of ionic strength, cationic form, and elevation
- 2009
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 335:1, s. 54-61
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Tidskriftsartikel (refereegranskat)abstract
- Colloid generation and sedimentation experiments were carried out on Na- and Ca-montmorillonite in order to verify whether pseudo-equilibrium concentrations are reached at the same level in both types of experiments. The size and concentration of colloidal Na- and Ca-montmorillonite particles were monitored as a function of time and distance from the colloid bed in different ionic strength solutions. A stable pseudo-equilibrium concentration was reached after time in generation and sedimentation experiments. The colloid concentration decreased sharply at distances near to the colloid source. Na-montmorillonite concentration at pseudo-equilibrium (roughly quantified at distances ≥7 cm from the colloid source) was 5.2 ± 0.5, 0.5 ± 0.1, and 0.2 ± 0.1 mg L-1 in 0.001, 0.01, and 0.1 M NaCl solution, respectively, while the Ca-montmorillonite concentration was 0.4 ± 0.2 mg L-1 in 0.001 M NaCl.
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| 5. |
- García García, Sandra, et al.
(författare)
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Effects of temperature on the stability of colloidal montmorillonite particles at different pH and ionic strength
- 2009
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Ingår i: Applied Clay Science. - : Elsevier BV. - 0169-1317 .- 1872-9053. ; 43:1, s. 21-26
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Tidskriftsartikel (refereegranskat)abstract
- The effect of temperature at different pH and ionic strengths on the aggregation kinetics of colloidal montmorillonite particles in aqueous dispersions was investigated. For a given temperature and pH, the rate constant for aggregation increased with increasing ionic strength. At pH:54 the rate constant for colloid aggregation increased with increasing temperature, regardless of ionic strength. At pH 10 the aggregation rate constant decreased with increasing temperature as a general trend. In the intermediate pH interval, the aggregation rate constant apparently decreased with increasing temperature except at the highest ionic strength, where it increased with increasing temperature. The aggregation rate constant decreased at alkaline pH compared with the acidic pH range. This effect became more pronounced at higher ionic strengths and higher temperatures but could not be observed at 4 degrees C. These observations are in qualitative agreement with DLVO calculations taking temperature, pH and ionic strength into account.
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| 6. |
- García García, Sandra, et al.
(författare)
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Kinetic determination of critical coagulation concentrations for sodium- and calcium-montmorillonite colloids in NaCl and CaCl2 aqueous solutions
- 2007
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 315:2, s. 512-519
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Tidskriftsartikel (refereegranskat)abstract
- The stability of the sodium and calcium forms of montmorillonite was studied at different NaCl and CaCl2 concentrations. The aggregation kinetics was determined from the decrease in particle concentration with time at different electrolyte concentrations. The DLVO theory defines the critical coagulation concentration (CCC) value as the electrolyte concentration that balances the attractive and repulsive potential energies between the particles, making aggregation diffusion-controlled. Therefore CCC values were obtained by extrapolation of the aggregation rate constants measured as a function of ionic strength to conditions where the rate constant value is determined by diffusion only. When the electrolyte was CaCl2, the CCC value was found to be approximately two orders of magnitude lower than the CCC values obtained using NaCl as electrolyte.
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| 7. |
- García García, Sandra, et al.
(författare)
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Temperature effect on the stability of bentonite colloids in water
- 2006
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 298:2, s. 694-705
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Tidskriftsartikel (refereegranskat)abstract
- The stability of natural bentonite suspensions has been investigated as a function of temperature at pH 9 and ionic strength 10-3 M. The sedimentation rate of the particles is directly related to their stability. The sedimentation kinetics was determined by examining the variation of particle concentration in solution with time. The observed kinetics for sedimentation is discussed quantitatively in terms of the potential energy between particles. The ζ-potential of the particles was measured and the DLVO theory was used to calculate attractive and repulsive potentials. Experimental observations are consistent with DLVO model predictions and show that the stability of bentonite colloids increases with temperature. Differences with other colloidal systems can be attributed to the temperature dependence of the surface charge of bentonite particles.
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| 8. |
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| 9. |
- Hedberg, Jonas, et al.
(författare)
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Interactions between surfactants and silver nanoparticles of varying charge
- 2012
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Ingår i: Journal of Colloid and Interface Science. - Amsterdam : Elsevier. - 0021-9797 .- 1095-7103. ; 369:1, s. 193-201
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Tidskriftsartikel (refereegranskat)abstract
- The interaction between silvernanoparticles (Ag NPs) of different surface charge and surfactants relevant to the laundry cycle has been investigated to understand changes in speciation, both in and during transport from the washing machine. Ag NPs were synthesized to exhibit either a positive or a negative surface charge in solution conditions relevant for the laundry cycle (pH 10 and pH 7). These particles were characterized in terms of size and surface charge and compared to commercially laser ablated Ag NPs. The surfactants included anionic sodium dodecylbenzenesulfonate (LAS), cationic dodecyltrimethylammoniumchloride (DTAC) and nonionic Berol 266 (Berol). Surfactant–Ag NP interactions were studied by means of dynamic light scattering, Raman spectroscopy, zeta potential, and Quartz Crystal Microbalance. Mixed bilayers of CTAB and LAS were formed through a co-operative adsorption process on positively charged Ag NPs with pre-adsorbed CTAB, resulting in charge reversal from positive to negative zeta potentials. Adsorption of DTAC on negatively charged synthesized Ag NPs and negatively charged commercial Ag NPs resulted in bilayer formation and charge reversal. Weak interactions were observed for nonionic Berol with all Ag NPs via hydrophobic interactions, which resulted in decreased zeta potentials for Berol concentrations above its critical micelle concentration. Differences in particle size were essentially not affected by surfactant adsorption, as the surfactant layer thicknesses did not exceed more than a few nanometers. The surfactant interaction with the Ag NP surface was shown to be reversible, an observation of particular importance for hazard and environmental risk assessments.
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| 10. |
- Hedberg, Jonas, et al.
(författare)
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Ion selective electrodes are not suitable for measurements of silver ion concentrations in alkaline carbonate media
- 2013
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Ingår i: Analytical Methods. - : RSC Publishing. - 1759-9660 .- 1759-9679. ; 5:4, s. 1068-1070
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Tidskriftsartikel (refereegranskat)abstract
- An ion selective electrode (ISE) for determination of the labile silver ion concentration in carbonate containing solutions of pH 10 was seen to give incorrect results due to shifts in the Ag vertical bar Ag+ equilibrium. This drawback was not the case for the differential pulse anodic stripping voltammetry (DPASV) method.
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