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  • 1
    ISSN: 1435-1536
    Schlagwort(e): Key words Evanescent wave ; Surface modification ; Light scattering ; Polystyrene latex ; Electrostatic interaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract The profile of the interaction potential between polystyrene latex particle and chemically modified glass surface was estimated directly by the evanescent wave light scattering microscope (EVLSM) method; this enables us to measure the distance between particle and surface as a function of time in the order of less than a millisecond. The minimum of the potential profile, which is the result of an electrostatic repulsion and an apparent attraction by gravity between the particle and surface, was clearly observed. To change the electrostatic nature, the glass surface was chemically modified by treatment with a silanization reagent and a vinyl monomer with a sulfonate group. As the absolute value of the zeta potential of the glass surface became larger, the position of the potential minimum on the interaction potential profile shifted away from the glass surface, reflecting an increase of electrostatic repulsion between the particle and the wall. The ionic strength dependence of the potential profile was also clearly observed. In conclusion, EVLSM is a powerful tool for the quantitative estimation of particle-wall interactions.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1435-1536
    Schlagwort(e): Key words Evanescent wave ; dynamic light scattering ; particle-wall interaction ; colloidal particle ; time-correlation function
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract  The diffusion behavior of polymer latex particles in dispersion near the quartz interface has been estimated by evanescent wave dynamic light scattering (EVDLS) technique. The diffusion coefficient of the particles was measured as a function of the distance between the particle and interface. The apparent diffusion coefficient estimated by EVDLS was small for particles near the interface and increased upon increasing the distance from the interface, and then saturated at a certain value which is close to the value expected for free-motion. The range of the distance over which diffusion was affected by interaction with the interface depended on the added salt concentration. This means that the diffusion of the particle is influenced by an electrostatic interaction between the particle and quartz interface in addition to the hydrodynamic effect near the wall. This range was found to be more than 800 nm at 0 M salt condition but about 400 nm at 10-4 and 10-3 M salt conditions. Hence it is appropriate to say that the hydrodynamic effect reaches up to 400 nm and the electrostatic effect is longer ranged, more than 800 nm, for the system studied here. The EVDLS technique is a very powerful tool for quantitative estimations of the dynamic behavior of the particle near the interface and for estimation of the range where the wall effect is dominant. EVDLS will give us an answer to the question of “where is the ‘interface’ and where is the ‘bulk’?”.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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