Abstract
There is a growing interest in extending plasmonics applications into the ultraviolet region of the electromagnetic spectrum. Noble metals are commonly used in plasmonic, but their intrinsic optical properties limit their use above 350 nm. Aluminum is probably the most suitable material for UV plasmonics, and in this work we fabricated substrates of nanoporous aluminum starting from an alloy of Al2Mg3. The porous metal is obtained by means of a galvanic replacement reaction. Such nanoporous metal can be exploited to achieve a plasmonic material suitable for enhanced UV Raman spectroscopy and fluorescence. Thanks to the large surface to volume ratio, this material represents a powerful platform for promoting interaction between plasmonic substrates and molecules in the UV.
Highlights
Collective oscillations of electron waves at the metal/dielectric interface, known as Surface Plasmons, find extensive applications in different fields such as surface-enhanced Raman spectroscopy (SERS), metal-enhanced fluorescence (MEF), photocatalysis, etc. [1]
The galvanic replacement reaction (GRR) proceeds as follows: Al2Mg3 + 2 AlCl4− > 4 Al(s) + 3 Mg2+ + 8 Cl−. This system shows very peculiar properties from the standpoint of materials preparation: (i) The GRR causes exhaustive replacement of Mg by Al; (ii) oxide formation and hydrogen evolution are excluded or minimized by operation in ionic liquid; (iii) Al deposition occurs inward, towards the bulk of the foil loosing Mg, and not outwards as one would normally expect; (iv) the process is a homogeneous plating with fresh Al of the inner nanostructures resulting from Mg loss and Al atoms rearrangement
Here we reported on GRR based procedures to prepare nanoporous Al (NPA) films from an alloy of Al and Mg
Summary
Collective oscillations of electron waves at the metal/dielectric interface, known as Surface Plasmons, find extensive applications in different fields such as surface-enhanced Raman spectroscopy (SERS), metal-enhanced fluorescence (MEF), photocatalysis, etc. [1]. Al in particular is still extremely interesting thanks to its low cost and large abundance It has been the object of extensive researches and has demonstrated interesting performances in the UV and DUV regions [28]. In order to use Al to generate localized surface plasmonic resonances (LSPR) in the UV spectral region, small metallic features/nanostructures must be prepared. Such structures can be designed with the help of electron beam lithography (EBL) and focused ion beam (FIB) lithography or achieved with different methods of synthesis of nanoparticles [29,30]. It has not been possible to achieve porous metals in pure Al phase
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