We report the first preparation of nanoporous Al-Mg alloy films by selective dissolution of Mg from a Mg-rich AlxMg1-x alloy. We show how to tune the stoichiometry, the porosity and the oxide contents in the final film by modulating the starting ratio between Al and Mg and the dealloying procedure. The obtained porous metal can be exploited for enhanced UV spectroscopy. In this respect, we experimentally demonstrate its efficacy in enhancing fluorescence and surface Raman scattering for excitation wavelengths of 360 nm and 257 nm respectively. Finally, we numerically show the superior performance of the nanoporous Al-Mg alloy in the UV range when compared to equivalent porous gold structures.The large area to surface ratio provided by this material make it a promising platform for a wide range of applications in UV/deep-UV plasmonics. IntroductionDuring the last decade, Localized Surface Plasmon Resonances (LSPRs) have been explored extensively for their various technological applications such as surface-enhanced Raman spectroscopy (SERS), metal-enhanced fluorescence (MEF), plasmon enhanced light harvesting, and photocatalysis. 1-7 Plasmonic applications have been mainly based on noble metals (e.g. Ag and Au) because of their good chemical stability even though their application is limited to the visible/ NIR range. 4,8,9 However, the advantages of extending plasmonic enhancements down to UV and deep-UV (DUV) wavelengths are drawing interests on alternative materials. 10-12 For example, UV and DUV excitations can be uniquely exploited to extend Raman spectroscopy to biomolecules with vanishing Raman cross sections in the visible and NIR regions. [13][14][15][16] Beside Magnesium, Gallium, Indium, and Ruthenium, Aluminum (Al) has been suggested as a promising plasmonic material in the UV and DUV regions 17-23 because its large plasma frequency leads to a negative permittivity (real part) down to wavelengths of ≈100 nm. 24,25 Aluminum also exhibits strong enhanced local fields owing to its high electron density (3 valence electrons per atom compared to 1 valence electron per atom in metals such as Au or Ag) and its overall optical properties make it an excellent material for UV nanoantennas, 20,26,27 DUV SERS, 28-31 light emission enhancement of wide-bandgap semiconductors, 23 improvement of light harvesting in solar cells, and UV MEF. 17,32 Al nanostructures are generally designed with the help of electron beam lithography (EBL) and focused ion beam (FIB) lithography in order to obtain well-controlled designs. 20,26 However, since very small nanostructures/nanogaps (5-10 nm) are required to achieve plasmonic resonances in the DUV, and considering the long fabrication processes involved, these top-down techniques are not costeffective and not recommended for large area fabrication (cm 2 ). 20,26 Several bottom-up approaches have been attempted in order to circumvent these difficulties, like nanoimprint lithography, 31 electrochemical anodization, 18 and chemical synthesis of aluminum nanocrystals. 33,34 Among the n...

We fabricate a plasmonic nanoslot that is capable of performing enhanced single molecule detection at 10 μM concentrations. The nanoslot combines the tiny detection volume of a zero-mode waveguide and the field enhancement of a plasmonic nanohole. The nanoslot is fabricated on a bi-metallic film formed by the sequential deposition of gold and aluminum on a transparent substrate. Simulations of the structure yield an average near-field intensity enhancement of two orders of magnitude at its resonant frequency. Experimentally, we measure the fluorescence stemming from the nanoslot and compare it with that of a standard aluminum zero-mode waveguide. We also compare the detection volume for both structures. We observe that while both structures have a similar detection volume, the nanoslot yields a 25-fold fluorescence enhancement.

In this work, we use a site-selective functionalization strategy to decorate plasmonic nanopores with one or more fluorescent dyes. Using an easy and robust fabrication method, we manage to build single plasmonic rings on top of dielectric nanotubes with different inner diameters. The modulation of the dimension of the nanopores allows us to both tailor their field confinement and their Purcell Factor in the visible spectral range. In order to investigate how the changes in geometry influence the fluorescence emission efficiency, thiol-conjugated dyes are anchored on the plasmonic ring, thus forming a functional nanopore. We study the lifetime of ATTO 520 and ATTO 590 attached in two different configurations: single dye, and FRET pair. For the single dye configuration, we observe that the lifetime of both single dyes decreases as the size of the nanopore is reduced.The smallest nanopores yield an experimental Purcell Factor of 6. For the FRET pair configuration, we measure two regimes. For large nanopore sizes, the FRET efficiency remains constant. Whereas for smaller sizes, the FRET efficiency increases from 30 up to 45% with a decrease of the nanopore size. These findings, which have been also supported by numerical simulations, may open new pathways to engineer the energy transfer in plasmonic nanopores with potential applications in photonics and biosensing, in particular in single-molecule detection towards sequencing.In recent years, plasmonic nanopores have been proposed for applications in single molecule detection towards sequencing 1 . Compared to the more common solid-state nanopores which are typically used for single molecule experiments based on ionic current measurements 2 , plasmonic nanopores offer interesting advantages for optical spectroscopic approaches 3,4,5 . Some of the key features of plasmonic nanopore are reduction of detection volume, localization of the electromagnetic field and increase of the signal-to-noise ratio. As a result, plasmonic nanopores find application in single molecule detection and sequencing based on Surface Enhanced Raman Scattering (SERS) 4 , as well as in fluorescence spectroscopy experiments 6,7 . In particular, enhanced fluorescence in plasmonic nanopores has been verified in single molecule DNA detection 8,3 . In these works, one or more nucleotides are

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.