arXiv subjects

Denis Garoli

Publications and source records attributed to Denis Garoli.

At least 19 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↗

arXiv2026

Hydrogel microwells with light-controlled reversible closure

We present a light-responsive hydrogel nanocomposite engineered into arrays of micrometer-scale wells that can be selectively and sequentially closed and re-opened via laser illumination. Polarization-controlled light exposure induces anisotropic surface deformations, leading to the formation of protrusive flaps sealing the wells. Owing to the intrinsic elasticity and anti-adhesive properties of the hydrogel matrix, the deformation process is partially reversible, allowing flap retraction and restoration of the original well geometry. This platform facilitates contactless, on-demand trapping and release of microscale objects using a standard optical microscopy configuration. As a proof of concept, we demonstrate the controlled manipulation of a single polystyrene microbead using optical tweezers, including bead positioning within a well, light-triggered closure, and subsequent reopening to release the particle into the surrounding aqueous environment.

physics.app-ph↗

arXiv2026

Ultrafast excitation of Bloch plasmon polaritons in hyperbolic metamaterials with an extreme ultra-violet transient grating

Manipulating materials properties with light drives advances in materials science and photonics. Hyperbolic metamaterials are promising candidates as next-generation quantum optical media. They support Bloch plasmon polaritons, which are characterized by potentially infinite wave-vectors and long lifetimes, but cannot be excited through direct light illumination due to momentum mismatch. Here, we experimentally show that a transient grating, formed via interference of fully coherent seeded free-electron laser pulses in a thin insulator film, enables the excitation of Bloch plasmon polaritons in an underlying hyperbolic metamaterial. Finite element simulations confirm the role of the transient grating in facilitating phase-matching and mode excitation. Our findings demonstrate a route to spatiotemporally excite Bloch plasmon polaritons modes, offering an alternative to permanently nanostructured gratings and potentially enabling ultrafast control of optical modes excitation.

physics.optics↗

arXiv2026

Reconfigurable Magnetic Nanopore Platform for Selective Trapping

Solid-state nanopores offer a powerful platform for nanoscale analysis of individual analytes, including biomolecules and functionalized nanoparticles, by confining them within a precisely defined sensing region. However, their inherently passive operation restricts practical applications, as they cannot precisely control particle position or dynamics inside the pore. Here, we introduce magnetic nanopore architectures that integrate a ferromagnetic layer into the nanopore system. Acting as a magnetic discontinuity within an otherwise uniformly magnetized film, the nanopore generates localized stray magnetic fields that enable magnetic tweezing of magnetic nanoparticles, which can be functionalized with fluorescent biomolecules. Importantly, the nanopore geometry is designed to reversibly switch between a nearly uniform magnetization state and a magnetic flux-closure state through the application of short magnetic field pulses of controlled amplitude. This capability allows the magnetic tweezing effect to be selectively activated or deactivated, enabling controlled capture and release of tagged biomolecules on demand. As a proof of concept, we demonstrate the selective magnetic trapping of fluorescent magnetic particles. These findings pave the way for reconfigurable, on-chip magnetic nanopore platforms capable of selective trapping and high-throughput single-particle detection. KEYWORDS: Nanopores, magnetic tweezers, fluorescence microscopy, vortex state, active control, magnetic nanoparticles

physics.optics↗

arXiv2026

Sel-assembled Rhodium Nanoantennas for Single-Protein UV SERS

Surface-enhanced Raman scattering (SERS) provides critical insights into analyte structure, dynamic processes, and intermolecular interactions at the single-molecule level. By exploiting the hotspot formation in the vicinity of plasmonic structures, SERS constitutes an established tool for fundamental biological research, particularly for early-stage disease diagnostics. In this context, the DNA Origami technique, with its high addressability, enables both the assembly of plasmonic nanostructures with nanometric accuracy, and the deterministic placement of a single analyte molecule precisely at the generated hotspot within them. To date, most DNA Origami based nanoantennas rely on gold or silver nanoparticles (NPs), whose plasmonic resonances are confined to the visible spectrum, severely limiting their use in other spectral ranges. To extend the operating range, we have recently established a robust strategy for self-assembling programmable ultraviolet (UV)-plasmonic dimer antennas using rhodium nanocubes. Herein, we leverage this tailored architecture to systematically investigate its performance for single-molecule UV-SERS. We demonstrated how biofabricated Rh-dimers can be used to detect the characteristic SERS signal of a single streptavidin molecule linked at the dimer s gap. Our results are validated through polarization dependent measurements that yield the expected signal modulation depending on the the dimer orientation only for the DNA origami with a protein at the hotspot. This work establishes a highly sensitive and polarization-tunable UV-SERS platform, laying a solid foundation for label-free optical investigation and bio-spectroscopy of individual biomolecules in the UV spectral range.

physics.app-ph↗

arXiv2026

DNA-Origami-Assembled Rhodium Nanoantennas for Deep-UV Label-Free Single-Protein Detection

Nanoparticles of plasmonic metals have significantly to the development of spectroscopic techniques, enabling strong confinement of electromagnetic fields at the nanoscale and corresponding signal amplification. However, to date, plasmonic applications have been limited mainly to the visible and near-infrared range, as materials supporting ultraviolet resonances typically exhibit poor chemical stability and lack robust surface functionalisation methods. In this work, we address these limitations by introducing a fully programmable approach to UV plasmonics based on rhodium nanocube dimers assembled using DNA origami templates. We have developed a reliable ligand exchange strategy that allows the functionalisation of rhodium nanocubes with DNA while maintaining their colloidal stability. These DNA-modified nanocubes act as modular building blocks that can be assembled into dimers with 69% efficiency and an average gap size of 10 nm. The DNA origami design also allows for the deterministic placement of a single streptavidin protein in the plasmonic gap, unlike previous methods based on stochastic diffusion. Experiments with single-molecule autofluorescence in UV, supported by numerical simulations, show an increase in brightness of up to 22, a reduction in fluorescence lifetime, and a more than tenfold increase in the total number of detected photons. By creating a robust and versatile platform for the production of UV-resonant plasmonic nanoantennas, this work extends the functionality of plasmonics to the deep UV spectrum and opens up new possibilities for labelling-free single-protein spectroscopy.

physics.optics↗

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

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

Molecularly imprinted nanopores for multiplexed sensing, release, and in-edge computing

In nanopore technology, the development of multiplexed detection and release platforms with high spatial and temporal resolution remains a significant challenge due to the difficulty in distinguishing signals originating from different nanopores in a single chip. In this work, we present a solid-state nanopore system functionalized with molecularly imprinted polymers (MIPs) for the selective detection and controlled release of neurotransmitters. We designed a nanopore array where each nanopore is functionalized with a specific MIP able to recognize specific neurotransmitters (dopamine, gamma-aminobutyric acid, and histamine, respectively). The platform demonstrated high performance in terms of sensitivity, selectivity, recovery, and stability. Multiplexed detection with high spatiotemporal resolution of the order of 100 ms/ 3 {\mu}m was achieved by specifically depositing MIPs and conductive hydrogels on different nanopores prepared on a single solid-state membrane. The employment of micro-chambers for each nanopore prevented signal cross-talk, thereby enabling simultaneous detection and release of multiple neurotransmitters. Moreover, we demonstrated computing with different logic gates and in-edge computing. This nanopore platform represents a radically novel approach towards hybrid solid-state nanopores able to perform real-time label-free multiplex detection, controlled biomolecule release, and ionic logic computing, addressing key challenges in neurochemical sensing and bio-computation.

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↗

arXiv2025

Transformable Plasmonic Helix with Swinging Gold Nanoparticles

Control over multiple optical elements that can be dynamically rearranged to yield substantial three-dimensional structural transformations is of great importance to realize reconfigurable plasmonic nanoarchitectures with sensitive and distinct optical feedback. In this work, we demonstrate a transformable plasmonic helix system, in which multiple gold nanoparticles (AuNPs) can be directly transported by DNA swingarms to target positions without undergoing consecutive stepwise movements. The swingarms allow for programmable AuNP translocations in large leaps within plasmonic nanoarchitectures, giving rise to tailored circular dichroism spectra. Our work provides an instructive bottom-up solution to building complex dynamic plasmonic systems, which can exhibit prominent optical responses through cooperative rearrangements of the constituent optical elements with high fidelity and programmability.

physics.bio-ph↗

arXiv2025

Ultrafast interband transitions in nanoporous gold metamaterial

Nanoporous metals have emerged as promising functional architectures due to their tunable optical and electronic properties, high surface areas, and versatile use in real-life applications such as sensing, catalysis, and biomedicine. While the optical and morphological properties of nanoporous metals have been extensively studied, their electronic properties at ultrafast timescales remain largely unexplored. Here, we study the transient response of a nanoporous gold metamaterial and compare it with the ultrafast dynamics of a continuous gold film. We unravel that the nanoporous sample supports lower energy interband transitions, due to a much higher electron temperature in the nanoporous material, which causes an enhanced redistribution of electron density around the Fermi level. The experimental results are consistent with the two-temperature model, which highlights the role of nanoscale porosity in enabling the more efficient generation of hot carriers, thus allowing lower energy photons to induce interband transitions. Our findings demonstrate that nanoporosity affects fundamental ultrafast electronic processes and introduces this platform as temporal metamaterial allowing the emergence of tunable electronic properties not supported by the bulk counterpart. Furthermore, we present new insights into ultrafast electronic properties of nanoporous metals, which can impact several areas, from photochemistry and catalysis to energy harvesting and opto-electronics.

cond-mat.mes-hall↗

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

Dynamics of DNA-Templated Ultrafine Silver Nanowires Formation

Recent research on silver nanowires prepared on DNA templates has focused on two fundamental applications: nano-scale circuits and sensors. Despite its broad potential, the formation kinetics of DNA-templated silver nanowires remains unclear. Here, we present an experimental demonstration of the formation of silver nanowires with a diameter of 2.2+0.4 nm at the single-molecule level through chemical reduction. We conducted equilibrium and perturbation kinetic experiments to measure force spectroscopy during the formation of Ag+ -DNA complexes and Ag-DNA complexes, using optical tweezers combined with microfluidics. The addition of AgNO3 resulted in an increase in force of 5.5-7.5 pN within 2 minutes, indicating that Ag+ compacts the DNA structure. In contrast, the addition of hydroquinone caused the force to decrease by 4-5 pN. Morphological characterization confirmed the presence of a dense structure formed by silver atoms bridging the DNA strands, and revealed conformational differences before and after metallization. We compare our experimental data with Brownian dynamics simulations using a coarse-grained double-stranded DNA (dsDNA) model that provides insights on the dependency of the force on the persistence length.

physics.app-ph↗

arXiv2024

Light structuring via nonlinear total angular momentum addition with flat optics

Shaping the structure of light with flat optical devices has driven significant advancements in our fundamental understanding of light and light-matter interactions, and enabled a broad range of applications, from image processing and microscopy to optical communication, quantum information processing, and the manipulation of microparticles. Yet, pushing the boundaries of structured light beyond the linear optical regime remains an open challenge. Nonlinear optical interactions, such as wave mixing in nonlinear flat optics, offer a powerful platform to unlock new degrees of freedom and functionalities for generating and detecting structured light. In this study, we experimentally demonstrate the non-trivial structuring of third-harmonic light enabled by the addition of total angular momentum projection in a nonlinear, isotropic flat optics element -- a single thin film of amorphous silicon. We identify the total angular momentum projection and helicity as the most critical properties for analyzing the experimental results. The theoretical model we propose, supported by numerical simulations, offers quantitative predictions for light structuring through nonlinear wave mixing under various pumping conditions, including vectorial and non-paraxial pump light. Notably, we reveal that the shape of third-harmonic light is highly sensitive to the polarization state of the pump. Our findings demonstrate that harnessing the addition of total angular momentum projection in nonlinear wave mixing can be a powerful strategy for generating and detecting precisely controlled structured light.

physics.optics↗

arXiv2024

Light-matter interactions in layered materials and heterostructures: from moir\'e physics and magneto-optical effects to ultrafast dynamics and hybrid meta-photonics

Layered two-dimensional (2D) materials have revolutionized how we approach light-matter interactions, offering unprecedented optical and electronic properties with the potential for vertical heterostructures and manipulation of spin-valley degrees of freedom. The discovery of moir\'e physics in twisted heterostructures has further unlocked new possibilities for controlling the band structure of tailored semiconductor heterostructures. In parallel, the integration of 2D materials with hybrid photonic structures and ultrafast studies on their optical and spin-valley properties has revealed a wealth of novel physical phenomena. This perspective highlights the recent advances in our understanding of light-matter interactions in moir\'e and 2D systems, with a particular emphasis on ultrafast processes and the integration of these materials into photonic platforms. We explore the implications for optoelectronics and emerging photonic technologies, positioning 2D materials as a transformative tool for next-generation devices.

cond-mat.mtrl-sci↗