We report the ultrasensitive detection of adenine using deep-UV surface-enhanced resonance Raman scattering on aluminum nanostructures. Well-defined Al nanoparticle arrays fabricated over large areas using extreme-UV interference lithography exhibited sharp and tunable plasmon resonances in the UV and deep-UV wavelength ranges. Theoretical modeling based on the finite-difference time-domain method was used to understand the near-field and far-field optical properties of the nanoparticle arrays. Raman measurements were performed on adenine molecules coated uniformly on the Al nanoparticle arrays at a laser excitation wavelength of 257.2 nm. With this technique, less than 10 amol of label-free adenine molecules could be detected reproducibly in real time. Zeptomole (~30,000 molecules) detection sensitivity was readily achieved proving that deep-UV surface-enhanced resonance Raman scattering is an extremely sensitive tool for the detection of biomolecules.

This study demonstrates the metal-enhanced fluorescence of adenine using aluminum nanoparticle arrays in the deep UV range. It achieves the reproducible intensity enhancement of intrinsic fluorescence up to 80 on well-defined aluminum nanoparticle arrays at 257 nm excitation. In addition to a high signal enhancement, a strong modification of the fluorescence emission spectrum of adenine is observed. This study illustrates that the label-free detection of DNA bases and proteins that have low intrinsic fluorescence and absorption bands in the deep UV range can be facilitated using aluminum nanostructures.

We report an experimental and theoretical study of the optical properties of two-dimensional arrays of aluminum nanoparticle in-tandem pairs. Plasmon resonances and effective optical constants of these structures are investigated and strong magnetic response as well as negative permeability are observed down to 400 nm wavelength. Theoretical calculations based on the finite-difference time-domain method are performed for various particle dimensions and lattice parameters, and are found to be in good agreement with the experimental results. The results show that metamaterials operating across the whole visible wavelength range are feasible.In the last decade, a new class of optical materials known as metamaterials have emerged and attracted significant interest. These are metallic structures engineered at the subwavelength scale to exhibit novel optical properties such as negative refractive index or magnetic activity at high frequencies [1]. After the first experimental demonstration in the microwave regime, the operation frequency of metamaterials has experienced a tremendous progress within a decade due to novel designs and nanofabrication techniques [2]. In particular, metal/dielectric/metal multilayers, such as cutwire nanopairs, fishnet nanostructures, and nanoparticle pairs, have enabled metamaterials operating at optical frequencies. These structures exhibit strong antisymmetric eigenmodes providing magnetic resonances and negative permeability, which is the prerequisite of negative refractive index metamaterials [3,4,5,6,7]. With such designs magnetic metamaterials at about 1.2 µm have been realized using interference lithography [8] In these aforementioned and many other works demonstrating metamaterials with negative refractive index or negative permeability mostly Au and Ag were used, which are, in fact, the conventional choice in plasmonics. On the other hand, Al is also a good optical material because of its low absorption and large real part of the dielectric constant. Whereas Au and Ag exhibit interband absorptions below the wavelengths of about 590 nm and 350 nm, respectively, which limit their applications in optics and plasmonics, Al has low absorption down to 200 nm due to its free-electron-like character and high bulk plasmon frequency [13]. These properties make Al an ideal candidate for plasmonic applications at short wavelengths [14,15,16,17].In this letter we study the plasmonic properties of arrays of Al in-tandem particle pairs. Ordered 2D arrays of Al/Al 2 O 3 /Al nanoparticles show strong plasmonic resonances of hybridized eigenmodes due to the near-field coupling between nanoparticles. We demonstrate that it is possible to tune the magnetic resonances down to 400 nm and obtain even negative permeability covering the whole visible range. Two-dimensional arrays of Al nanoparticles pairs on quartz substrates (HPFS) were fabricated using extremeultraviolet interference lithography (EUV-IL) and sequential deposition of Al, Al 2 O 3 , and Al with a subsequent lift-off process. EUV-IL provi...

We report ultrasensitive and label-free detection of 2,4,6-trinitrotoluene (TNT) deposited by drop coating using deep-ultraviolet surface-enhanced resonance Raman scattering (DUV-SERRS). Well-defined aluminum nanoparticle arrays as the SERRS substrate at 257 nm excitation wavelength enabled highly reproducible and real-time detection of TNT down to the detection limit of the attogram level in quantity. This extreme sensitivity can be further improved by optimization of the nanostructured substrates. DUV-SERRS promises to have a large impact on public safety and security, as it can be readily extended to other explosives and hazardous materials.

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