arXiv subjects

Francesco Scotognella

Publications and source records attributed to Francesco Scotognella.

At least 19 recordsLinked to original sources

arXiv2026

Tamm Plasmon Resonance Responsiveness to SARS-CoV-2 Virus-Like Particles

Bioresponsive optical materials that transduce nanoscale biointerface events into measurable spectral signals are of growing interest for sensing and antiviral technologies Here we show that a Tamm plasmon TP device consisting of a SiOTiO distributed Bragg reflector capped with a nanostructured silver layer exhibits a selective and structure dependent response to SARSCoV2 virus like particles VLPs Upon VLP exposure the conventional wavelength shift delta lambda of the TP resonance is minimal whereas the resonance depth undergoes a systematic attenuation To capture both spectral and amplitude variations we introduce a displacement angle alpha defined from the translation vector of the Tamm dip before and after exposure The angle alpha increases monotonically with VLP concentration and enables a limit of detection of 13 ng per mL Control experiments with polystyrene nanoparticles of similar size and with heat denatured VLPs yield negligible changes indicating sensitivity to the native conformational state of viral surface proteins rather than to generic nanoparticle morphology or bulk refractive index effects These results establish Tamm plasmon structures as promising bioresponsive platforms for label free detection and for probing structure dependent virus material interactions.

physics.optics↗

arXiv2023

Time-domain observation of interlayer exciton formation and thermalization in a MoSe$_2$/WSe$_2$ heterostructure

Vertical heterostructures (HS) of transition metal dichalcogenides (TMDs) host interlayer excitons (ILX), with electrons and holes residing in different layers. With respect to their intralayer counterparts, ILX feature much longer lifetimes and diffusion lengths, paving the way to excitonic optoelectronic devices operating at room temperature. While the recombination dynamics of ILX has been intensively studied, the formation process and its underlying physical mechanisms are still largely unexplored. Here we use ultrafast transient absorption spectroscopy with a white-light probe, spanning both intralayer and interlayer exciton resonances, to simultaneously capture and time-resolve interlayer charge transfer and ILX formation dynamics in a MoSe$_2$/WSe$_2$ HS. We find that the ILX formation timescale is nearly an order of magnitude (~1 ps) longer than the interlayer charge transfer time (~100 fs). Microscopic calculations attribute the relative delay to an interplay between a phonon-assisted interlayer exciton cascade and subsequent cooling processes, and excitonic wave-function overlap. Our results provide an explanation to the efficient photocurrent generation observed in optoelectronic devices based on TMD HS, as the ILX have an opportunity to dissociate during their thermalization process.

cond-mat.mtrl-sci↗

arXiv2023

Role of the annealing parameters on the resistance of indium tin oxide nanocrystalline films

The optical and electrical properties of films made of nanoparticles of indium tin oxide (ITO) are widely studied because of the significance of this material for transparent electrodes, smart windows, and nonlinear optics components. In this work, a systematic study of the resistance in ITO nanocrystalline films, as a function of post-fabrication parameters, such as the temperature and time of annealing, has been performed. A tunability of the resistance with the annealing parameters, in a range of three orders of magnitude, has been demonstrated.

cond-mat.mes-hall↗

arXiv2022

Tamm Plasmon Resonance as Optical Fingerprint of Silver/Bacteria Interaction

Incorporation of responsive elements into photonic crystals is an effective strategy for building up active optical components to be used as sensors, actuators and modulators. In these regards, Tamm Plasmon (TP) modes have arisen recently as powerful optical tools for the manipulation of light-matter interaction and for building sensors/actuators. These emerge at the interface between a dielectric mirror and a plasmonic layer and, interestingly, can be excited at normal incidence angle with relatively high quality factors. Although its field is located at the interface between the dielectric mirror and the metal, recent studies have demonstrated that corrugation at the nanoscale permits to access the TP mode from the outside, opening new exciting perspectives for many real-life applications. Here, we show that the TP resonance obtained by capping a distributed Bragg reflector with a nanostructured layer of silver is sensitive to the presence of bacteria. We observed that nanoscale corrugation is essential for accessing the TP field, while the well-known bio-responsivity of silver nanostructures renders such a localised mode sensible to the presence of Escherichia Coli. Electrodoping experiments confirm the pivotal role of nanostructuration, as well as strengthening our hypothesis that the modifications of the TP mode upon exposure to bacteria are related to the accumulation of negative charge due to the bacterial-driven removal of Ag+ ions from its lattice. Finally, we devised a case study in which we disentangled optically the presence of proliferative and non-proliferative bacteria using the TP resonance as a read-out, thus making these devices as promising simple all-optical probes for bacterial metabolic activity, including their response against drugs and antibiotics.

physics.optics↗

arXiv2022

Vanadium oxide metal-insulator phase transition in different types of one-dimensional photonic microcavities

The optical properties of vanadium dioxide ($VO_2$) can be tuned via metal-insulator transition. In this work different types of one-dimensional photonic structure-based microcavities that embed vanadium dioxide have been studied in the spectral range between 900 nm and 2000 nm. In particular, $VO_2$ has been sandwiched between: i) two photonic crystals made of $SiO_2$ and $ZrO_2$; ii) two aperiodic structures made of $SiO_2$ and $ZrO_2$ that follow the Thue-Morse sequence; iii) two disordered photonic structures, made of $SiO_2$ and $ZrO_2$ in which the disorder is introduced either by a random sequence of the two materials or by a random variation of the thicknesses of the layers; iv) two four material-based photonic crystals made of $SiO_2$, $Al_2O_3$, $Y_2O_3$, and $ZrO_2$. The ordered structures i and iv show, respectively, one and two intense transmission valleys with defect modes, while the aperiodic and disordered structures ii and iii show a manifold of transmission valleys due to their complex layered configurations. The metal-insulator transition of $VO_2$, controlled by temperature, results in a modulation of the optical properties of the microcavities.

physics.optics↗

arXiv2022

Tunable cavity modes and light-pulse propagation in diarylethene-based photo-switchable polymeric microcavities

Light responsive devices employing molecular photo-switches are interesting for displays and dynamic light filtering. In this work, polymeric microcavities embedding a layer of photochromic compound have been studied by means of the transfer matrix method. Different polymers, such as poly vinyl carbazole, poly styrene and cellulose acetate, have been used. A microcavity that includes random one-dimensional photonic structures sandwiching the photochromic layer has also been studied. Propagation of light pulses through the microcavities has been analysed.

physics.optics↗

arXiv2022

Microcavities integrated in metal halide perovskite light-emitting field-effect transistors

Metal halide perovskites are materials that show unique characteristics for photovoltaics and light emission. Amplified spontaneous emission and stimulated emission has been shown with these materials, together with electroluminescence in light-emitting diodes and light-emitting transistors. An important achievement that combine stimulated emission and electroluminescence could be the fabrication of electrically driven metal halide perovskite lasers. In this work, the integration of metal halide perovskite light-emitting field-effect transistors with photonic microcavities is proposed. This can lead to the engineering of electrically driven lasers. The microcavities have been designed in order to have the cavity mode at 750 nm, which is the peak wavelength of the electroluminescent spectrum of recently reported MaPbI3-based electroluminescent devices. The optical properties of the photonic microcavities have been simulated by means of the transfer matrix method, considering the wavelength dependent refractive indexes of all the materials involved. The material for the gate is indium tin oxide, while different materials, either inorganic or organic, have been considered for the microcavity architectures.

physics.optics↗

arXiv2022

Near-Infrared plasmon induced hot electron extraction evidence in an indium tin oxide nanoparticle / monolayer molybdenum disulphide heterostructure

In this work, we observe plasmon induced hot electron extraction in a heterojunction between indium tin oxide nanocrystals and monolayer molybdenum disulphide. We study the sample with ultrafast differential transmission exciting the sample at 1750 nm where the intense localized plasmon surface resonance of the indium tin oxide nanocrystals is and where the monolayer molybdenum disulphide does not absorb light. With the excitation at 1750 nm we observe the excitonic features of molybdenum disulphide in the visible range, close to the exciton of molybdenum disulphide. Such phenomenon can be ascribed to a charge transfer between indium tin oxide nanocrystals and monolayer molybdenum disulphide upon plasmon excitation. These results are a first step towards the implementation of near infrared plasmonic materials for photoconversion.

physics.optics↗

arXiv2022

Bismuth vanadate layers alternated with nanoparticle-doped silicon dioxide layers for one-dimensional multilayer photonic crystals

Bismuth vanadate is one of most studied materials in the field of photocatalysis due to its high photocatalytic activity. The modulation of its optical properties can be engineered by fabricating photonic crystals in which bismuth vanadate is included. In the present study, bismuth vanadate in the monoclinic clinobisvanite structure has been included in a one-dimensional photonic crystal. Bismuth vanadate layers are alternated with layers on silicon dioxide doped with titanium dioxide nanoparticles and silver nanoparticles. The optical properties of the crystal have been studied by employing the transfer matrix method, taking into account all the refractive index dispersions of the selected materials. The transmission spectra have been studied as a function of the bismuth vanadate layers thickness and the filling factor of titanium dioxide and silver dioxide in the silicon dioxide layers.

physics.optics↗

arXiv2022

The Impact of Tamm Plasmons on Photonic Crystals Technology

This review describes hybrid photonic-plasmonic structures based on periodic structures that have metallic coatings or inserts which make use of the Tamm plasmon for sensing applications. The term Tamm plasmon refers a particular resonance resulting from the enhancement of a surface plasmon resonance absorption via coupling to a wavelength-matching photonic bandgap provided by a photonic crystal. Tamm plasmon-based devices come in an ample variety of material and geometric combinations, each designed to perform a specific kind of measurement. While the physical effect is quite well documented and understood, its implementation in devices is still a rapidly developing and thriving field, which leaves open many possibilities for novel designs and new applications. We therefore aim of giving a complete overview on the topic, so as to provide an ordered collection of designs and uses, as well as to spur further development on the subject of the Tamm plasmon for sensing applications.

physics.optics↗

arXiv2022

Ultrafast structural color change in indium tin oxide/titanium dioxide 1D photonic crystal

Photonic crystals can integrate plasmonic materials such as indium tin oxide (ITO) in their structure. Exploiting ITO plasmonic properties it is possible to tune the photonic band gap of the photonic crystal upon the application of an external stimuli. In this work, we have fabricated a one-dimensional multilayer photonic crystal via radiofrequency sputtering and we have triggered its optical response with ultrafast pump-probe spectroscopy. Upon photoexcitation we observe a change in the refractive index of indium tin oxide. Such effect has been used to create a photonic crystal that change its photonic bandgap in an ultrafast time scale. All optical modulation in the visible region, that can be tuned by designing the photonic crystal, has been demonstrated.

physics.optics↗

arXiv2021

New Strategies for Solar Cells Beyond the Visible Spectral Range

The endeavor of the scientific community to maximize the possibility to harvest Sun irradiation for energy production is mainly devoted to the improvement of the power conversion efficiency of devices and to the extension of the spectral range in which solar devices operate. Considering that a significant portion of the Sun irradiation at the ground level is in the infrared, the research on materials and systems that operate in such region is gaining increasing attention. In this review, we will report recent advancements in multijunction solar cells, inorganic-organic perovskite solar cells, organic solar cells, colloidal quantum dot solar cells focusing on the absorption of such devices in the infrared. In addition, the use of upconverting nanostructures will be introduced as a way to indirectly exploit infrared radiation to increase power conversion efficiency of photovoltaic devices. Moreover, we will describe plasmon induced hot electron extraction based solar cells, that are particularly promising in absorbing the infrared portion of the Sun irradiation when the active materials are doped semiconductors, which show intense plasmonic resonances in the infrared. The review includes the optical spectroscopy tools to study the hot electron extraction from doped semiconductor-based heterojunctions.

cond-mat.mes-hall↗

arXiv2021

Bringing the Interaction of Silver Nanoparticles with Bacteria to Light

In the last decades the exploitation of silver nanoparticles in novel antibacterial and detection devices have risen to prominence for their well-known specific interaction with bacteria. The vast majority of studies focus on the investigation over the mechanism of action underpinning bacterial eradication, while little efforts have been devoted to the modification of silver optical properties upon interaction with bacteria. Specifically, given the characteristic localized surface plasmon resonance of silver nanostructures, which is sensitive to changes in the charge carrier density or in the dielectric environment, these systems can offer a handle in the detection of bacteria pathogens. In this review, we present the state of art of the research activity on the interaction of silver nanoparticles with bacteria, with emphasis on the modification of their optical properties. This may indeed lead to easy color reading of bacterial tests and pave the way to the development of nanotechnology silver based bacterial detection.

physics.bio-ph↗

arXiv2021

MaPBI3 and 2D hybrid organic inorganic perovskite based microcavities employing periodic, aperiodic and disordered photonic structures and with the possibility of light-induced tuning

Inorganic-organic perovskites semiconductors are becoming increasingly interesting due to their remarkable optical properties, such as a high photoluminescence quantum yield and the possibility to show optical gain in a broad range of wavelengths. We have here simulated microcavities that embed MaPBI3 and 2D hybrid organic inorganic perovskite semiconductors by sandwiching such active layers between periodic, aperiodic and disordered photonic structures. We have carefully considered the refractive index dispersion of all the materials employed, such silicon dioxide, titanium dioxide and the perovskite layers. Moreover, by employing a photochromatic polymer, namely the diarylethene-based polyester pDTE, we have designed a microcavity with light-induced tuning of the cavity modes is possible.

physics.optics↗

arXiv2021

Calculated optical properties of BTTzR donor molecule and its derivatives

In this work, we study the light absorption properties of a novel molecule (BTTzR) and its more extended derivatives, which hold promise as electron-donor material in organic solar cells. By employing density functional theory, we observe that the addition of two and three oligothiophene chains to the central benzene ring of the benzo[1,2-b:4,5-b']dithiophene (BDT-T) leads to both a red-shift of the existing peaks and, interestingly, to the development of new blue-shifted features, an effect that can certainly increase the panchromaticity of the molecule in the visible spectral range.

cond-mat.mtrl-sci↗

arXiv2021

The Impact of Bacteria Exposure on the Plasmonic Response of Silver Nanostructured Surfaces

Silver, especially in the form of nanostructures, is widely employed as an antimicrobial agent in a large range of commercial products. The origin of the biocidal mechanism has been elucidated in the last decades, and most likely originates from silver cation release due to oxidative dissolution followed by cellular uptake of silver ions, a process that causes a severe disruption of bacterial metabolism and eventually leads to eradication. Despite the large number of works dealing with the effects of nanosilver shape/size on the antibacterial mechanism and on the (bio)physical chemistry pathways that drive bacterial eradication, little effort has been devoted to the investigation of the silver NPs plasmon response upon interaction with bacteria. Here we present a detailed investigation of the bacteria-induced changes of the plasmon spectral and dynamical features after exposure to one of the most studied bacterial models, Escherichia Coli. Ultrafast pump-probe measurements indicate that the dramatic changes on particle size/shape and crystallinity, which stem from a bacteria-induced oxidative dissolution process, translate into a clear modification of the plasmon spectral and dynamical features. This study may open innovative new avenues in the field of biophysics of bio-responsive materials, with the aim of providing new and reliable biophysical signatures of the interaction of these materials with complex biological environments.

cond-mat.mes-hall↗

arXiv2020

Anisotropic complex refractive indices of atomically thin materials: determination of the optical constants of few-layer black phosphorus

In this work we briefly review the studies of the optical constants of monolayer transition metal dichalcogenides and few layer black phosphorus, with particular emphasis to the complex dielectric function and refractive index. Specifically, we give an estimate of the complex index of refraction of phosphorene and few-layer black phosphorus. We extracted the complex index of refraction of this material from differential reflectance data reported in literature by employing a constrained Kramers-Kronig analysis. Finally, we studied the linear optical response of multilayer systems embedding phosphorene by using the transfer matrix method.

cond-mat.mes-hall↗

arXiv2020

Modularity affects the robustness of scale-free model and real-world social networks under betweenness and degree-based node attack

In this paper we investigate how the modularity of model and real-world social networks affect their robustness and the efficacy of node attack (removal) strategies based on node degree (ID) and node betweenness (IB). We build Barabasi-Albert model networks with different modularity by a new ad hoc algorithm that rewire links forming networks with community structure. We traced the network robustness using the largest connected component (LCC). We find that higher level of modularity decreases the model network robustness under both attack strategies, i.e. model network with higher community structure showed faster LCC disruption when subjected to node removal. Very interesting, we find that when model networks showed non-modular structure or low modularity, the degree-based (ID) is more effective than the betweenness-based node attack strategy (IB). Conversely, in the case the model network present higher modularity, the IB strategies becomes clearly the most effective to fragment the LCC. Last, we investigated how the modularity of the network structure evaluated by the modularity indicator (Q) affect the robustness and the efficacy of the attack strategies in 12 real-world social networks. We found that the modularity Q is negatively correlated with the robustness of the real-world social networks under IB node attack strategy (p-value< 0.001). This result indicates how real-world networks with higher modularity (i.e. with higher community structure) may be more fragile to betwenness-based node attack. The results presented in this paper unveil the role of modularity and community structure for the robustness of networks and may be useful to select the best node attack strategies in network.

physics.soc-ph↗