Silver nanoparticles (AgNP) were synthesized by the
chemical reduction of silver nitrate (AgNO3) using
sodium borohydride (NaBH4). To this end, 200 mL of
a 4 mM NaBH4 solution was added to 200 mL of a
2 mM AgNO3 solution (Guidelli et al. 2012c). The
color of the solution became immediately yellow,
indicating the formation of colloidal silver. The
system was kept under vigorous stirring for 12 h.
Then, different volumes of the solution containing
AgNP were added to 8 mL of NRL, to prepare the
NRL–AgNP system with different silver mass. The
mixture was stirred for 5 min. The membranes were
fabricated by carefully dropping the freshly prepared
colloidal dispersion on a 8.5 cm diameter plate
followed by drying procedure at 40 C. To insure
higher homogeneity of the membrane, the dispersion
was dropped in 10 steps. The final membranes were
yellow, suggesting that the AgNP were stabilized by
the rubber molecules and did not segregate to form
aggregates. A pure NRL membrane was also prepared
by the same procedure, as control.
Four samples containing different amounts of
AgNP were produced. They were labeled according
to the mass percentage of nanoparticles. For instances,
NRL–AgNP_0.01 % refers to an NRL membrane
containing 0.01 % silver mass percentage, and so on.