  A robust and reproducible preparation of self-standing nanoporous gold leaves
(NPGL) is presented, with optical characterization and plasmonic behaviour
analysis. Nanoporous gold (NPG) layers are tipically prepared as thin films on
a bulk substrate. Here we present an alternative approach consisting in the
preparation of NPGL in the form of a self-standing film. This solution leads to
a perfectly symmetric configuration where the metal is immersed in a
homogeneous medium and in addition can support the propagation of symmetric and
antisymmetric plasmonic modes. With respect to bulk gold, NPG shows metallic
behaviour at higher wavelengths, suggesting possible plasmonic applications in
the near / medium infrared range. In this work the plasmonic properties in the
wide wavelength range from the ultraviolet up to the mid-infrared range have
been investigated.
