The development of
porous materials with hierarchical porous structures
is currently of great interest. These materials exhibit properties
representative of different pore scales and thus open up the possibility
of being used in new applications. In this paper, a method for the
preparation of silver foams with hierarchical porous structures is
discussed. Here, the replication method, which is typically used to
produce coarse-pore foams, is merged with dealloying, which is commonly
used to manufacture small-pore foams. For this purpose, packed NaCl
particles (hard template) were infiltrated with 75%Al–25%Ag
alloy (whose so-called soft template is the Al-rich phase). Both the
hard and soft templates were removed by water dissolution and dealloying
with HCl or NaOH solutions, respectively. Extensive characterization
of the resulting materials revealed pores ranging from a few nanometers
to hundreds of micrometers. The materials were characterized by their
antibacterial performance against Gram-positive and Gram-negative
bacteria and showed significantly higher activity than both silver
foams prepared by sintering pure Ag particles and silver nanofoams
produced by chemical dealloying. The combinations of pores of different
sizes and the resulting high internal specific surface area have a
decisive influence on the antibacterial capacity of these new materials.