arXiv subjects

German Lanzavecchia

Publications and source records attributed to German Lanzavecchia.

12 recordsLinked to original sources

arXiv2026

Nanoporous Copper Films as Platform for UV-SERS: Sensitivity and Ability to Perform Chiral Discrimination

Surface enhanced Raman spectroscopy (SERS) in the ultraviolet (UV) region offers important advantages for biomolecular detection, including resonance enhancement and reduced fluorescence interference. However, the development of UV SERS substrates that combine low cost, reproducibility, and chemical stability remains challenging. Here, we employ a dry synthesis approach to fabricate nanoporous Cu and copper oxide (CuO) films on silicon substrates and systematically evaluate their UV SERS performance using adenine as a Raman reporter under 325 nm excitation. Among the substrates investigated, nanoporous Cu exhibits the strongest enhancement, enabling adenine detection down to 10 microM. In contrast, no detectable adenine Raman signal is observed under 532 nm excitation, indicating that the enhancement is dominated by a UV induced chemical, charge transfer mechanism rather than conventional electromagnetic enhancement. The Cu substrates further enable the UV Raman spectroscopy of streptavidin, as a test protein, and, more interestingly, the discrimination between L and D tryptophane based solely on differences in UV SERS intensity, without chiral selectors or additional surface functionalization. By varying the substrate rotation speed during metal evaporation, the enantioselective response can be tuned, yielding L over D intensity ratios from 1.10 to 2.35 and demonstrating the critical role of substrate morphology in chiral discrimination. The dry synthesized nanoporous films provide a simpler, scalable, and ligand free fabrication strategy while offering additional capability for enantioselective detection. These findings establish dry processed nanoporous Cu films as promising platforms for UV-SERS biosensing and label free chiral analysis.

physics.app-ph↗

arXiv2026

Voltage-Controlled Phosphate Precipitation Gating in Solid-State Nanopore Memristors

Nanofluidic memristors preserve a record of electrical activity via ion migration and alterations in conductance that depend on the history of the device s state. These characteristics make them suitable for aqueous, energy efficient, and biologically compatible neuromorphic systems. To establish the viability of fluidic memristors for mimicking the brain s dynamic behavior, a more thorough understanding of the memristive materials and the underlying switching processes is required. In this study, we systematically examined a recently introduced memristive device based on inpore chemical reactions, where the combined influence of electrolyte composition and pore architecture on precipitation gated memory remains poorly understood. To address this, we constructed an asymmetric electrochemical system using CaCl2 and phosphate solutions separated by SiNx solid state nanopores. We explored how variations in pH, phosphate concentration, pore geometry, and voltage pulsing regimens affect the electrical characteristics and memristive performance. Comparison of the single pore and the array showed that parallel pores produced smoother pH and concentration dependent hysteresis and pulse responses, whereas the single pore retained larger, nonmonotonic changes.

physics.app-ph↗

arXiv2025

Plasmonic nanopore to monitor in-pore chemistry

In solid-state nanopores, achieving reliable control over pore aperture opening and closing (gating) remains a major challenge. Gating can be driven by the applied voltage involving electrically tunable chemical reactions, achieved by selecting appropriate compounds within the nanopore volume. In particular, cyclic precipitation and dissolution of metal phosphates can be triggered by regulating cation transport through an applied transmembrane voltage, thereby enabling reversible pore gating. Under negative bias, metal phosphate precipitates form inside the pore, obstructing ion flow and reducing current. Switching the polarity dissolves the precipitates, restoring ionic conductance. This process effectively produces a nanofluidic diode characterized by a remarkably high rectification ratio. To probe these localized chemical reactions more directly, we employed a plasmonic nanopore that generates strong confined fields, enabling surface-enhanced Raman scattering (SERS) measurements within the nanopore volume during cyclic gating. These measurements not only validate the proposed in-pore chemistry but also highlight the potential of plasmonic nanopores as powerful tools for monitoring nanoscale chemical processes with high spatial resolution.

physics.app-ph↗

arXiv2025

Probing Electro-Magnetic Field Enhancement in 3D Plasmonic Nanopores Using DNA-PAINT and Nanorulers

Plasmonic nanopores combine nanofluidic confinement with electromagnetic field enhancement, enabling optical interrogation of single molecules in sub-wavelength volumes. Yet, direct optical readout within these metallic geometries has remained challenging due to fluorescence quenching near the surface. Here, we implement DNA-PAINT as a molecular reporter of local optical fields inside plasmonic nanopores. Transient hybridization of fluorescent imager strands at the nanopore tips yields stochastic emission bursts that map active binding sites with nanometric precision. By varying the fluorophore-metal distance using DNA spacers of controlled length, we observe a non-monotonic intensity response consistent with near-field quenching and plasmonic enhancement, identifying an optimal separation of around 6 nm. Finally, we extend the concept to dual-material Au/Si nanopores, demonstrating lateral coupling between plasmonic and semiconducting regions. These results establish DNA-PAINT as a quantitative probe of nanoscale optical environments in hybrid nanopores.

physics.app-ph↗

arXiv2025

UV-SERS monitoring of plasmons photodegradation of biomolecules on Aluminum platforms decorated with Rhodium nanoparticles

In the search for novel nanostructured materials for UV plasmonics a limited number of choices can be done. Materials such as aluminum, rhodium, gallium and few others can be used. One of the most interesting application for UV plasmonics is Surface Enhanced Raman Spectroscopy. It can be extended to this spectral range to explore spectral properties of biomolecules that have only a small cross section in the visible spectral range. We have recently reported on a functional substrates based on nanoporous aluminum decorated with rhodium nanoparticles. This system showed an interesting behavior for UV excitation at 266 nm, with an unexpected decreasing Raman intensity for increasing rhodium nanoparticles concentrations. We proposed that this effect can be due to the difficult access to the hot spots for the molecules deposited via thermal evaporation. Here we extend this study exploring the performance of the system at another UV excitation wavelengths (325 nm) reporting on experimental results obtained using a deposition process that can bring the molecules at the hot-spots in a more efficient way. Extensive spectroscopic acquisitions, combined with 3D maps, allow to shade a more clear view on the performance of this plasmonic platform. In particular, the photodegration and the potential oxidation of biomolecules driven by the hot-electron/hot-holes produced by the rhodium nanoparticles will be reported.

physics.app-ph↗

arXiv2025

Layered Bimetal Nanoporous Platforms for SERS Sensing

Nanoporous metals are extensively investigated as platforms for applications in plasmonics. They present high surface areas and strong local electric fields that can be tuned at different energies, playing with the choice of the metals and the morphology of the porous layers. Until recently, research in the field of plasmonics has primarily focused on porous metals composed of a single element, with limited attention given to the impact of alloy composition. The investigation of bi-metallic systems has only just begun to emerge in the literature. In particular, combining two or more different plasmonic metals, it could be possible to explore the interactions between two metals excited at specific energies. This involves plasmonic coupling, electron transfer, band hybridization at the interface, electromagnetic field interactions, and possibly thermal and electronic energy transfer depending on separation, size, and materials involved. The analysis of bi-metal systems can also be interesting in biomolecule detection, such as in the case of Surface Enhanced Raman Scattering (SERS). Here we report, for the first time, a detailed study (comprising morphological analyses, numerical modelling, and optical spectroscopies) on bi-metal nanoporous platforms prepared with a dry-synthesis method enabling the easy and controllable fabrication of bilayers combining different metals such as Au, Ag, and Cu.

physics.app-ph↗

arXiv2025

Gated MoS2/SiN Nanochannel for Tunable Ion Transport and Protein Translocation

Ionic transport in nanofluidic channels holds great promise for applications such as single-molecule analysis, molecular manipulation, and energy harvesting. However, achieving precise control over ion transport remains a major challenge. In this work, we introduce a MoS2 SiN hybrid nanochannel architecture that enables electrical tuning of ionic transport via external gating, and we examine its potential for osmotic power generation and single molecule detection. To fabricate the channels, we employed a combined focused ion beam (FIB) milling and dry transfer method, producing sub 10 nm thick structures while preserving the structural integrity and electronic properties of MoS2, essential for reliable surface charge modulation. We first investigated how the gate voltage influences ionic conductance, finding evidence of gate dependent modulation of ion selectivity under different bias polarities. Next, by applying a salt concentration gradient across the nanochannels, we demonstrated the feasibility of this platform for osmotic energy harvesting. Finally, we tested the system for single molecule sensing, showing that linearized bovine serum albumin (BSA) produced translocation signals with notably long dwell times. Together, these results highlight gated MoS2 SiN nanochannels as a promising platform for tunable nanofluidics, with potential applications in controlled molecular transport and energy harvesting from osmotic gradients.

physics.app-ph↗

arXiv2024

Modular plasmonic nanopore for opto-thermal gating

Solid-state nanopore gating inspired by biological ion channels is gaining increasing traction due to a large range of applications in biosensing and drug delivery. Integration of stimuli-responsive molecules such as poly(N-isopropylacrylamide) (PNIPAM) inside nanopores can enable temperature-dependent gating, which so far has only been demonstrated using external heaters. In this work, we combine plasmonic resonators inside the nanopore architecture with PNIPAM to enable optical gating of individual or multiple nanopores with micrometer resolution and a switching speed of few milliseconds by thermo-plasmonics. We achieve a temperature change of 40 kelvin per millisecond and demonstrate the efficacy of this method using nanopore ionic conductivity measurements that enables selective activation of individual nanopores in an array. Moreover, the selective gating of specific nanopores in an array can set distinct ionic conductance levels: low, medium, and high (i.e., 0, 1, and 2), which could be exploited for logical gating with optical signal control. Such selective optical gating in nanopore arrays marks a breakthrough in nanofluidics, as it paves the way towards smart devices that offer multifunctional applications including biosensing, targeted drug delivery, and fluidic mixing.

physics.app-ph↗

arXiv2024

Tailored Fabrication of 3D Nanopores with Dielectric Oxides for Multiple Nanoscale Applications

Nanopore sensing is a key technology for single-molecule detection and analysis. Solid-state nanopores have emerged as a versatile platform, since their fabrication allows to engineer their properties by controlling size, shape, and chemical functionalization. However, lithography-based fabrication approaches for non-planar nanopores-on-chip rely on polymers that have limits with respect to hard- and robustness, durability, and refractive index. In this respect, nanopores made of metal oxides with high dielectric constant would be much more favourable and have the potential to extend the suitability of solid-state nanopores towards optoelectronic technologies. Here, we present a versatile method to fabricate three-dimensional nanopores of different dielectric oxides with controlled shapes. Our approach uses photoresist only as a template in the focused-ion-beam lithography to define the nanopore shape, which is subsequently coated with different oxides (SiO2, Al2O3, TiO2 and HfO2) by atomic-layer deposition. Then the photoresist is fully removed by chemo-physical treatment, resulting in nanopores entirely made from dielectric oxides on a thin solid-state membrane. Our methodology allows straightforward fabrication of convex, straight, and concave nanopore shapes that can be employed in various technologies and applications. We explored their performance as ionic nanochannels and investigated the dependence of the ionic current rectification on the nanopore geometry. We found hysteresis in the ionic conductance that enables potential applications of the nanopores in memristors. We also investigated the dielectric oxide nanopores for DNA sensing by measuring both cis-trans and trans-cis translocations and support our data with numerical simulations based on the Poisson-Nernst-Planck model.

physics.app-ph↗

arXiv2024

Porous aluminium decorated with rhodium nanoparticles, preparation and use as platform for UV plasmonics

There is a high current interest for novel plasmonic platforms and materials able to extend their applicability into the ultraviolet (UV) region of the electromagnetic spectrum. In the UV it is possible to explore spectral properties of biomolecules with small cross section in the visible spectral range. However, most used metals in plasmonics have their resonances at wavelengths > 350 nm. Aluminum and rhodium are two interesting candidate materials for UV plasmonics, and in this work we developed a simple and low-cost preparation of functional substrates based on nanoporous aluminum decorated with rhodium nanoparticles. We demonstrate that these functionalized nanoporous metal films can be exploited as plasmonic materials suitable for enhanced UV Raman spectroscopy

physics.app-ph↗

arXiv2024

Ionic Current Rectification in Nanopores: Effects of Nanopore Material, Electrolyte and Surface Treatment

Ionic Current Rectification (ICR) can appear in nanopores, causing a diode-like behavior that originates from different efficiency of ion transport through the pore channel with respect to the applied voltage bias polarity. This effect is particularly interesting for nanopores with a short channel length, that is smaller than 500 nm, because then the dependence of the ion current on the direction along which the ions pass through the channel is determined by the geometry and material of the nanopore, and by the ion concentration in the electrolyte. Surface charges can play an important role, and therefore nanopores consisting of multiple materials can induce ICR because of different charge distributions at the nanopore-electrolyte interface for the different material sections. In this work, we study four solid-state nanopore designs considering different geometries of charge distributions along the inner and outer surfaces of nanopores, and evaluate their impact on ICR with six different electrolytes. The direct comparison between experimental data and modeling enables to understand how the different surface charge configurations impact the ICR.

physics.app-ph↗

arXiv2023

Plasmonic Photochemistry as a Tool to Prepare Metallic Nanopores with Controlled Diameter

We show that plasmonic solid-state nanopores with tunable hole diameter can be prepared via a photocatalytic effect resulting from the enhanced electromagnetic field inside a metallic ring prepared on top of a dielectric nanotube. Under white light illumination, the maximum field intensity in these nanorings induces a site selective metal nucleation and growth. We used this approach to prepare bare Au and bimetallic Au-Ag nanorings and demonstrate the reduction of the initial inner diameter of the nanopore down to 4 nanometers. This process can be applied over large arrays with good reproducibility and good control on the nanopore diameter. The tunability of the nanopore diameter can be used to enable optimized detection of single entities with different size, such as single nanoparticles or biomolecules. As proof-of-concept, we demonstrate the versatility of the platform to perform single object detection of dsDNA, and Au nanoparticles with a diameter of 15 nm and 30 nm. We support our experimental findings with numerical simulations that provide insights into the electromagnetic field intensity distribution, showing that a field intensity enhancement of up to 104 can be achieved inside the nanopores. This strong field confinement inside the final nanopore can be used to perform enhanced optical measurements, and to generate local heating, thereby modifying the ionic conductance of the nanopore

physics.optics↗