3.2. Effect polyol incorporation on metal dispersion
The non-uniform dispersion of MNPs must be due to the heterogeneous
density of the small amount of hydroxyl groups belonging to the
incorporated H20 poly dendrimer on the CT surface. Incorporation of
polyol appears to act as the main dispersing agent of MNP, favoring
complete metal entrapping by surrounding OH groups. This must take place
through stronger Polyol-HO:Metal interaction that consumes all available
OH groups of the inserted dendrimer at the expense of H20@CT surface
association. This explains the presence of Polyol:MNP composite scales
unstuck on the CT surface (Fig. 1.b ). Similar observations can
be made with Ag-modified materials, except the fact that metal salt
needles apparently occur in much higher density. This corresponds to a
relatively higher amount of residual unreduced Ag salt, i.e. less
Ag0 compared to copper-loaded materials. This lower
reduction level of Ag+ cations suggests a lower amount
of Ag0 atoms. This could explain somehow the
paradoxically weaker antibacterial activity of Ag-based materials as
compared to their Cu counterparts, given that silver is expected to
display higher performance in this regard. A partial explanation resides
in the stronger capacity of copper to undergo oxidative processes as
compared to silver. The involvement of the OH groups in metal
stabilization can be explained by changes in the hydrophilic character
and basicity of the host materials. Deeper insights in this regard were
achieved through TPD measurements.