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The ability to monitor electrogenic cells accurately plays a pivotal role in neuroscience, cardiology and cell biology. Despite pioneering research and long-lasting efforts, the existing methods for intracellular recording of action potentials on the large network scale suffer limitations that prevent their widespread use. Here, we introduce the concept of a meta-electrode, a planar porous electrode that mimics the optical and biological behaviour of three-dimensional plasmonic antennas but also preserves the ability to work as an electrode. Its synergistic combination with plasmonic optoacoustic poration allows commercial complementary metal-oxide semiconductor multi-electrode arrays to record intracellular action potentials in large cellular networks. We apply this approach to measure signals from human-induced pluripotent stem cell-derived cardiac cells, rodent primary cardiomyocytes and immortalized cell types and demonstrate the possibility of non-invasively testing a variety of relevant drugs. Due to its robustness and easiness of use, we expect the method will be rapidly adopted by the scientific community and by pharmaceutical companies.

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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...

Biosensors are easy-to-use and cost-effective devices that are emerging as an attractive tool, not only in settling diagnosis or in disease monitoring, but also in mass screening tests, a timely topic that impacts on daily life of the whole society. Nanotechnologies lend themselves to the development of highly sensitive devices whose realization has become a very interdisciplinary topic. Relying on the enhancement of the fluorescence signal detected at the surface of patterned gold nanoparticles, we report the behavior of an analytical device in detecting immunoglobulins in real urine samples that shows a limit of detection of approximately 8 μg/L and a linear range of 10−100 μg/L well below the detection limit of nephelometric method, which is the reference method for this analysis. These performances have been reached thanks to an effective surface functionalization technique and can be improved even more if superydrophobic features of the substrate we produce will be exploited. Since the analyte recognition is realized by antibodies the specificity is very high and, in fact, no interference has been detected by other compounds also present in the real urine samples. The device has been assessed on serum samples by comparing IgG concentrations values obtained by the biosensor with those provided by a nephelometer. In this step we found that our approach allows the analysis of the whole blood without any pretreatment; moreover, it is inherently extendable to the analysis of most biochemical markers in biological fluids.

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.

The enhancement of nonlinear optical effects via nanoscale engineering is a hot topic of research. Optical nanoantennas increase light–matter interaction and provide, simultaneously, a high throughput of the generated harmonics in the scattered light. However, nanoscale nonlinear optics has dealt so far with static or quasi-static configurations, whereas advanced applications would strongly benefit from high-speed reconfigurable nonlinear nanophotonic devices. Here we propose and experimentally demonstrate ultrafast all-optical modulation of the second harmonic (SH) from a single nanoantenna. Our design is based on a subwavelength AlGaAs nanopillar driven by a control femtosecond light pulse in the visible range. The control pulse photoinjects free carriers in the nanostructure, which in turn induce dramatic permittivity changes at the band edge of the semiconductor. This results in an efficient modulation of the SH signal generated at 775 nm by a second femtosecond pulse at the 1.55 μm telecommunications (telecom) wavelength. Our results can lead to the development of ultrafast, all optically reconfigurable, nonlinear nanophotonic devices for a broad class of telecom and sensing applications.

Engineered electromagnetic fields in plasmonic nanopores enable enhanced optical detection for single-molecule sensing and sequencing. Here, a plasmonic nanopore prepared in a thick nanoporous film is used to investigate, by means of surface-enhanced Raman spectroscopy, the interaction between the metallic surface of the pore and a long-chain double-strand DNA molecule free to diffuse through the pore. We discuss how the matrix of the porous material can interact with the molecule thanks to: (i) transient aspecific interactions between the porous surface and DNA; (ii) diffusion; and (iii) thermal and optical forces exerted by the localized field in a metallic nanostructure on the DNA molecule. An interaction time up to tens of milliseconds enables us to collect high signal-to-noise Raman signatures, allowing an easy label-free reading of information from the DNA molecule. Moreover, to increase the rate of detection, we tested a polymeric porous hydrogel placed beneath the solid-state membrane. The hydrogel enables a slowdown of the molecule diffusion time, thus increasing the number of detected interaction events by a factor 20. The analysis of the observed Raman peaks and their relative intensities, combined with theoretical simulations, allows us to get further information on the process of translocation and the folding state and orientation of the translocating molecule. Our results demonstrate temporary adsorption of the DNA molecule on the porous material during the translocation due to the diffusion force. Finally, we provide a qualitative evaluation of the nucleotides’ contents in the different groups of collected signal. The proposed approach can find interesting applications not only in DNA sensing and sequencing but also on generic nanopore spectroscopy.