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at the solid-liquid interface (Dong et al., 2011). In this mode, adsorption at
the solid-liquid interface can be determined in situ. In ATR-FTIR, a beam of
infrared light is passed through a crystal of high refractive index at an angle
that results in total internal refl ection. The total internal refl ection creates an
evanescent wave that extends several microns into the sample, allowing detec-
tion at the surface layer. In regions of the infrared spectrum where the sample
absorbs energy, the evanescent wave will be attenuated or altered and show
up on the refl ected IR spectrum (PerkinElmer, 2005). ATR-FTIR measures
the changes that occur in the refl ected infrared beam to detect and quantify
adsorption at the surface layer (Hind et al., 2001). The adsorbed amount can
be quantifi ed by comparing the absorbance of C-H stretching against a cali-
bration curve with known deposited mass (Dong et al., 2011).
10.3.5
Fluorescence and Confocal Microscopy
In fl uorescence microscopy, the sample is illuminated by light of a certain
wavelength and can then be detected at the emission wavelength of the fl uo-
rescence molecules. The fl uorescence microscope uses a dichroic mirror to
fi lter out the excitation wavelength, allowing detection of the weaker emitted
light at the higher wavelength. For the interfacial study of LCNP, fl uorescent
dye or fl uorescent lipid (lipids conjugated with fl uorescent molecules) can be
used to label the crystalline particles.
For high-resolution imaging deep within a sample, a confocal laser scanning
microscope (CLSM) can be used (Prasad et al., 2007). Confocal microscopy
uses point illumination with a spatial pinhole to eliminate out-of-focus illumi-
nation, such that only fl uorescence in the focal plane can be detected. Confocal
microscopy reduces blurring of an image from the scattered light to create
sharp optical sections. The cross-sectional images can then be combined to
create detailed three-dimentional images.
10.4
NONLAMELLAR LIQUID CRYSTALLINE SURFACE LAYERS
10.4.1
Solid Interface
Nonlamellar liquid crystalline surface layers can be formed by adsorption of
LCNPs. Recent studies have investigated the adsorption properties of GMO-
based bicontinuous cubic phase nanoparticle (CPNP) stabilized by Pluronics
F-127, on hydrophobic and hydrophilic solid surfaces by the means of null
ellipsometry, QCM-D, atomic force microscopy (AFM), fl orescence micros-
copy, and neutron refl ectometry (Vandoolaeghe et al., 2006, 2009b). Depend-
ing on the surface properties, electrolyte concentrations, and pH, different
adsorption scenarios were discerned (Figs. 10.3 and 10.4). The time evolution
of the adsorbed amount and thickness shows the structure formation and
sheds light on the mechanisms of adsorption. Figure 10.5 schematically
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