Electrospinning of Chitosan (CHT) - Modern Trends in Chemistry and Chemical Engineering - page 86

The size distribution of the dispersed solution evaluates with a Zetasizer (Malvern In-
struments). The conductivity of nanofiber samples measured using a homemade four-
probe electrical conductivity cell operating at constant humidity. The electrodes were
circular pins with separation distance of 0.33 cm and fibers were connected to pins
by silver paint (SPI). Between the two outer electrodes, a constant DC current applies
by Potentiostat/Galvanostat model 363 (Princeton Applied Research). The generated
potential difference between the inner electrodes and the current flow recorded by
digital multimeter 34401A (Agilent). Figure 5.3 illustrates the experimental setup for
conductivity measurement. The conductivity (δ: S/cm) of the nanofiber thin film with
rectangular surface can then be calculated according to equation 1 which parameters
call for length (L:cm), width (W:cm), thickness (t:cm), DC current applied (mA), and
the potential drop across the two inner electrodes (mV). All measuring repeated at
least five times for each set of samples.

IL
##

#

d =

(1)

VWt

Figure 5.3. The experimental setup for four-probe electrical conductivity measurement of nanofiber
thin film.

RESULTS AND DISCUSSION
The Characteristics of MWNT/CHT Dispersion
Utilization of MWNTs in biopolymer matrix initially requires their homogenous dis-
persion in a solvent or polymer matrix. Dynamic light scattering (DLS) is a sophisti-
cated technique used for evaluation of particle size distribution. DLS provides many
advantages for particle size analysis to measures a large population of particles in a
very short time period, with no manipulation of the surrounding medium. DLS of
MWNTs dispersions indicate that the hydrodynamic diameter of the nanotube bundles
is between 150 and 400 nm after 10 min of sonication for Sample 2. (see Fig. 5.4)