Page 173 - Book Hosokawa Nanoparticle Technology Handbook

3.5 INTERACTIONS BETWEEN PARTICLES FUNDAMENTALS
(See Fig. 3.5.20). The spectroscope (the resolu- electrical double layer (Debye length) that changes
tion is 3.2 nm/mm) is the core part of this opti- depending on the salt concentration, i.e. the Debye
length decreases with the increased salt concentra-
cal system and used to read the wavelength of
tion. This is a direct experimental demonstration of
the interference fringe (FECO). The wavelength
the DLVO theory.
of FECO is determined using micrometer The surface forces measurements enable us to inves-
equipped with an encorder and/or a CCD cam- tigate the electrical double-layer force, which plays an
era with a video gauge, at the exit side of a spec- important role for the stability of colloidal dispersions,
and the various interactions due to adsorption of poly-
troscope.
mers or polyelectrolyte [8–10]. Recently, extending
Generally, mica, which is molecularly smooth and research area, the authors have investigated the
transparent, is used as a substrate surface. A thin adsorption in binary liquids [11], and also developed a
2
film mica sheet (2~3 m thick, 10 mm ) is glued on resonance shear measurement [12] to characterize
the cylindrical quartz lens (20 mm radius, 10 mm nano-rheological and/or nano-tribological properties
diameter). These lenses are then mounted in an of liquid in a confined nanospaces. Surface force
apparatus in the crossed cylindrical geometry. measurement becomes one of essential techniques in
Interference occurs by the reflected light between nanomaterial science and technology.
the backside of mica surfaces coated with 50-nm
silver films, which enhance the interference. Since
the surfaces are in the crossed cylindrical geometry, References
the interference fringes show a parabolic shape. [1] J.N. Israelachvili: Intermolecular and Surface Forces
When two surfaces approach, the parabolic curves
move toward the short wavelength region, and the (2nd ed.), Academic Press, London (1991).
spaces of adjacent fringes increase. The separation [2] V.S.J. Craig: Colloids Surfaces A, 129/130, 75 (1997).
distance between surfaces can be calculated from the [3] D. Tabor, H.S. Winterton: Nature, 219, 1120 (1968);
wavelength of these interference fringes [6]. D. Tabor, H.S. Winterton: Proc. R. Soc. London Ser. A,
312, 435 (1969).
(2) Experimental example [4] J.N. Israelachvili, G.E. Adams: J. Chem. Soc. Faraday
Israelachvili et al. measured the interaction forces Trans. I, 74, 975 (1978).
between mica surfaces in aqueous solutions in the dis- [5] W.A. Ducker, T.J. Senden and R.M. Pashley:
tance range of 0–100 nm using SFA. Figure 3.5.21 Langmuir, 8, 1831 (1992).
compares the force curves measured by SFA and the [6] CSJ (ed): Colloid Science IV. Experimental Method in
DLVO theory for mica surfaces in KNO solution
3
-4
(10 ~1 M) [4]. The repulsive force decays exponen- Colloid Science, Kagakudojin Press, Tokyo (1996).
tially with distance, and turns to the short-range [7] K. Kurihara, T. Kunitake: J. Am. Chem. Soc., 115,
attractive force. The decay length of the long-ranged 10927 (1992).
repulsive force is in agreement with that of the [8] S.S. Patel, M. Tirrell: Annu. Rev. Phys. Chem., 40, 597
(1989).
[9] K. Kurihara, Y. Murase:Handbook of Polyelectrolytes
and their Applications, Vol. 1, American Science
Publisher, p. 207 (2002).
[10] P. Berndt, K. Kurihara and T. Kunitake: Langmuir, 8,
2486 (1992).
[11] M. Mizukami, K. Kurihara: Chem. Lett., 1005 (1999);
256 (2000).
[12] K. Kurihara: Ekisyo, 6, 34 (2002).
3.5.3.2 AFM colloid probe method
The invention of the surface force apparatus (SFA)
has helped create important and fundamental knowl-
edge about the interaction forces between solid sur-
faces. However, applying the SFA to the measurement
of a variety of surfaces is sometimes difficult because
of the following: (1) the test surface material must be
atomically smooth and transparent, which is practi-
Figure 3.5.21 cally restricted to mica; (2) it usually takes a long time
Surface forces profile between mica surfaces in an to obtain data; and (3) the instruments are rather less
aqueous solution. versatile for handling and operation. Due to these

149