Overcharging of magnetite nanoparticles in electrolyte solutions
| Autor: | Svitlana V. Netreba, Vitaliy A. Prokopenko, Sandor Barany, Maryna Manilo, Nikolai Lebovka |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
Aqueous solution
Inorganic chemistry Nanoparticle 02 engineering and technology Electrolyte 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences 0104 chemical sciences Electrophoresis chemistry.chemical_compound Colloid and Surface Chemistry Isoelectric point chemistry Particle Surface charge 0210 nano-technology Magnetite |
| Zdroj: | Colloids and Surfaces A: Physicochemical and Engineering Aspects. 506:291-297 |
| ISSN: | 0927-7757 |
| DOI: | 10.1016/j.colsurfa.2016.06.047 |
| Popis: | The effect of electrolytes with mono-, bi-, and trivalent anions on the surface charge (ζ-potential) of magnetite nanoparticles was investigated. The nanoparticles of magnetite, Fe 3 O 4 , were synthesised using different methods: a) coprecipitation of bivalent and trivalent iron sulphates at temperature T = 25 °C (sample NM 1 ) and b) oxidation of rotating steel disk in distilled water at T = 25 °C (sample NM 2 ) and at T = 50 °C (sample NM 3 ). All samples were characterized using transmission electron microscopy, infra-red spectroscopy, by measurements of electrophoretic mobility and particle size distribution. Transmission electron microscopy data evidenced that primary particles in dried powder samples have quasi-spherical shape with mean diameters of ⿿15 nm (Nп 1 ), ⿿80 nm (Nп 2 ) and ⿿70 nm (Nп 3 ). From other hand data of particle size distribution analysis in aqueous suspensions at pH 6 indicated formation of aggregates of size of ⿿30 nm (Nп 1 ), ⿿1200 nm (Nп 2 ) and ⿿520 nm (Nп 3 ). Infra-red data also evidenced the presence of different functional groups in dependence on the protocol of synthesis. In presence of background electrolyte KCl (1 mM) the isoelectric point for all particles was in the interval ѿп 6.0⿿8.0. Adding of electrolytes with mono- (Cl ⿿ ), bi- (SO 4 2⿿ ), and trivalent (PO 4 3⿿ ) anions resulted in noticeable differences in behaviour of the ζ-potential and position of the isoelectric point for particles Nп 1 , Nп 2 and Nп 3 . An increase of concentration of electrolytes always resulted in overcharging (changing from positive to negative charge) of particles Nп 1 and NM 3 , whereas for particle Nп 2 the overcharging was observed for both bivalent (SO 4 2⿿ ) and trivalent (PO 4 3⿿ ) anions. This behaviour cannot be explained by changes in the structure of electric double layer. The observed shifts of the isoelectric point and changes in the pH values in the presence of electrolytes reflected the impact of specific adsorption of anions on the ζ-potential of magnetite nanoparticles. Differences in pH values at which overcharging of nanoparticles took place can be explained by diverse structure of the surfaces of particles Nп 1 , Nп 2 and Nп 3 . |
| Databáze: | OpenAIRE |
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