Roberto Bartolino | University of Calabria (original) (raw)

Papers by Roberto Bartolino

We present a novel fast bistable nematic cell with intrinsic grey scale. The geometry of a single... more We present a novel fast bistable nematic cell with intrinsic grey scale. The geometry of a single pixel is the usual sandwich one, with tow conductive flat plates that contain a film of nematic material with positive dielectric anisotropy. An electric field is applied perpendicularly to the boundary plates. This novel deice works by controlling the creation and the erasure

Hybrid Polymer Composite Materials, 2017

We have investigated and characterized the unique properties of a liquid crystalline DNA in terms... more We have investigated and characterized the unique properties of a liquid crystalline DNA in terms of template and spontaneous-assisted organization by exploiting both top-down and bottom-up approaches. The chemical and physical properties of a passive polymeric template are used to assist the long-range order of a long and short DNA, trapped within microperiodic channels (top-down approach). The spontaneous self-organization of a human genomic DNA is used, by means of an electrostatic mechanism, to organize gold nanorods at the nanoscale (bottom-up approach). The main opportunity highlighted in our studies is the extraordinary capability to realize several applications ranging from photonics to plasmonics by exploiting the intrinsic properties of a bio-inspired material.

Proceedings of the National Academy of Sciences, 2021

Common fluids cannot sustain static mechanical stresses at the macroscopic scale because they lac... more Common fluids cannot sustain static mechanical stresses at the macroscopic scale because they lack molecular order. Conversely, crystalline solids exhibit long-range order and mechanical strength at the macroscopic scale. Combining the properties of fluids and solids, liquid crystal films respond to mechanical confinement by both flowing and generating static forces. The elastic response, however, is very weak for film thicknesses exceeding 10 nm. In this study, the mechanical strength of a fluid film was enhanced by introducing topological defects in a cholesteric liquid crystal, producing unique viscoelastic and optomechanical properties. The cholesteric was confined under strong planar anchoring conditions between two curved surfaces with sphere–sphere contact geometry similar to that of large colloidal particles, creating concentric dislocation loops. During surface retraction, the loops shrank and periodically disappeared at the surface contact point, where the cholesteric heli...

ABSTRACT The acronym POLICRYPS indicates a nano/micro composite structure made of films of well a... more ABSTRACT The acronym POLICRYPS indicates a nano/micro composite structure made of films of well aligned nematic liquid crystal (NLC) alternated to slices of almost pure polymer. Structures are fabricated by curing a homogeneous mixture of mesogenic material, monomer and a curing agent with UV radiation, under suitable physical and geometrical conditions. In particular, geometrical conditions determine (in the range 0.2 ÷ 15μm) the spatial periodicity of the realized sample, which can be utilized for transmitting, diffracting or reflecting an impinging light beam, with negligible scattering losses. The spatial modulation of the refractive index (from polymer to NLC) can be switched ON and OFF both by applying an electric field of few V/μm or, in some cases, by irradiating the sample with a light beam of suitable wavelength. This electrical/optical tuneability is responsible for a series of distinctive characteristics of the optical effects produced by the structure, and determines the range of possible applications. In fact, in different geometries, the POLICRYPS can be exploited as a switchable holographic grating, a switchable optical phase modulator, a switchable beam splitter, a tuneable Bragg filter or it can be exploited as an electro-optical edge filter in an optical interrogation system.

Journal of Applied Physics, 2002

This work is aimed at a deeper understanding of the polarity-sensitive electro-optical response o... more This work is aimed at a deeper understanding of the polarity-sensitive electro-optical response observed in a liquid crystal (LC) cell with asymmetric insertion of thin films of TiO2-V2O5 having a Ti/V atomic ratio of 1/1, prepared by sol-gel synthesis on a transparent indium tin oxide substrate. After preliminary structural characterization of the films, the electro-optical response of the liquid crystal

The 21st International …, 2006

Valentin Barna 1, Giuseppe Strangi 1, Roberto Caputo 2, Antonio De Luca 3, Carlo Versace 1, Nicol... more Valentin Barna 1, Giuseppe Strangi 1, Roberto Caputo 2, Antonio De Luca 3, Carlo Versace 1, Nicola Scaramuzza 1, Cesare Umeton 3, Roberto Bartolino 1, and Gabriel Noam Price 4.(1) DEPARTMENT OF PHYSICS, UNIVERSITY OF CALABRIA AND LICRYL-LIQUID ...

Applied Surface Science, 2009

Journal of Nanotheranostics, 2022

Glioblastoma multiforme (GBM) is one of the deadliest and most aggressive cancers, remarkably res... more Glioblastoma multiforme (GBM) is one of the deadliest and most aggressive cancers, remarkably resilient to current therapeutic treatments. Here, we report preliminary in vivo studies of GBM treatments based on photo-nanotherapeutics to activate synergistic killing mechanisms. Core-shell nanoparticles have been weaponized by combining photophysical properties of a new generation PDT agent (Ir(III) complex) with the thermoplasmonic effects of resonant gold nanospheres. In order to investigate the damages induced in GBM treated with these photoactivable nanosystems, we employed X-ray phase-contrast tomography (XPCT). This high-resolution three-dimensional imaging technique highlighted a vast devascularization process by micro-vessels disruption, which is indicative of tumor elimination without relapse.

Photonics, 2021

A bio-photonic cavity quantum electrodynamic (C-QED) framework could be imagined as a system in w... more A bio-photonic cavity quantum electrodynamic (C-QED) framework could be imagined as a system in which both the “cavity” and the “atom” participating in the light-matter interaction scenario are bio-inspired. Can a cavity be made of a bio-polymer? If so, how should such a cavity appear and what are the best polymers to fabricate it? Can a bioluminescent material stand the comparison with new-fashion semiconductors? In this review we answer these fundamental questions to pave the way toward an eco-friendly paradigm, in which the ever-increasing demand for more performing quantum photonics technologies meets the ever-increasing yet silent demand of our planet to reduce our environmental footprint.

Materials Research Express, 2019

Molecular Crystals and Liquid Crystals, 2012

In this paper we report on the realization and characterization of a polymer template sculptured ... more In this paper we report on the realization and characterization of a polymer template sculptured in photosensitive material on a chemical inert surface, devoted to micro/nano-confinement of a wide range of organic components, with self-arrangement properties at the nanoscale. The high quality morphology of the polymeric micropattern arrays is obtained by combining a nano-precision level optical holographic setup and a

Physical Review E, 2001

A liquid crystal (LC) cell has been made by using a standard sandwich configuration with one of t... more A liquid crystal (LC) cell has been made by using a standard sandwich configuration with one of the indium tin oxide (ITO) electrodes covered by a thin layer of tungsten trioxide (WO3). In this kind of cell optical polarization switching (observed under a crossed polarizer microscope) occurs for only one of the two polarities of an ac external applied electric field, while in the usual liquid crystal cells the electro-optic response does not depend on the sign of the field. The inhibiting switching configuration corresponds to anodic polarization of the tungsten trioxide film in which the deintercalation of cations occurs. Here we present the time behavior of charge and discharge for both the anodic and cathodic currents. A model based on charge carrier exchange between the ITO-WO3 and WO3-LC interfaces and also electrochemical processes is reported. Our model is also capable of explaining the electric and electro-optic asymmetric responses of the cell. Numerical calculations confirm the model.

Thin Solid Films, 2004

Transmission ellipsometry studies of both nematic and smectic liquid crystals (LCs) confined by m... more Transmission ellipsometry studies of both nematic and smectic liquid crystals (LCs) confined by mixed conductor substrates are reported. By simultaneously measuring the Stokes parameters of transmitted light, we follow the modification of the polarization state of the monochromatic light propagating through the LC cells. The analysis of the polarization states of the probe beam during the application of a specific voltage waveform at the LC samples allows obtaining important physical information on the investigated systems. The weakening of the anchoring energy in nematic LC samples and the experimental evidence of the Goldstone mode during the switching process of smectic LCs are reported.

Physical Review Letters, 2005

Distributed feedback microstructures play a fundamental role in confining and manipulating light ... more Distributed feedback microstructures play a fundamental role in confining and manipulating light to obtain lasing in media with gain. Here, we present an innovative array of organic, color-tunable microlasers which are intrinsically phase locked. Dye-doped helixed liquid crystals were embedded within periodic, polymeric microchannels sculptured by light through a single-step process. The helical superstructure was oriented along the microchannels; the lasing was observed along the same direction at the red edge of the stop band. Several physical and technological advantages arise from this engineered heterostructure: a high quality factor of the cavity, ultralow lasing threshold, and thermal and electric control of the lasing wavelength and emission intensity. This level of integration of guest-host systems, embedded in artificially patterned small sized structures, might lead to new photonic chip architectures.

physica status solidi (c), 2008

Philosophical Magazine, 2010

Thin films of lead zirconate titanate (PZT) have been obtained by a modified sol-gel route on flo... more Thin films of lead zirconate titanate (PZT) have been obtained by a modified sol-gel route on float glass and indium tin oxide (ITO) covered float glass substrates. Different thermal treatments have been performed on the deposited films in the range between 100 to 700 °C. Spectroscopic ellipsometry was used to investigate the optical properties of the deposited films, and the changing optical absorption spectra have been associated to the growth of two different crystal phases, pyrochlore and ferroelectric perovskite, as a function of annealing temperature. Moreover, a specific resonance at 1.9 nm, was detected when thin PZT films are deposited on ITO substrates and has been attributed to a particular charge distribution at the interface. Finally, the performance in rectifying the electro-optical response of asymmetric nematic liquid crystal cells have been tested for some of the films undergoing different thermal treatments.

Optics Express, 2007

This work is aimed to the photopolarimetric characterization of the disorder evolution occurring ... more This work is aimed to the photopolarimetric characterization of the disorder evolution occurring in homeotropically aligned nematic liquid crystal films during the electrically induced Fréedericksz transition. The molecular director dynamics and the transversal reorientation modes are investigated by the analysis of the depolarization of the light beam emerging from the sample. Our measurements reveal unexpected depolarization effects at the transition, which we interpret in terms of director field unhomogeneity and defects creation.

Optics Express, 2006

We report a detailed physical characterization of a novel array of organic distributed feedback m... more We report a detailed physical characterization of a novel array of organic distributed feedback microcavity lasers possessing a high ratio between the quality factor Q of the resonant cavity and its volume V. The optical microcavity was obtained by confining self-organized mesophases doped with fluorescent guest molecules into holographically patterned polymeric microchannels. The liquid crystal microchannels act as mirrorless cavity lasers, where the emitted laser light propagates along the liquid crystal helical axis behaving as Bragg resonator. This miniaturization process allows us to obtain a micro-laser array possessing an ultralow lasing threshold (25nJ/pulse) while having directional control on the lasing emission, a fine wavelength tunability and the control over the emission intensity.

Molecular Crystals and Liquid Crystals, 2005

A study of the depolarisation effect which occurs in a light beam passing through a thin homogeno... more A study of the depolarisation effect which occurs in a light beam passing through a thin homogenously oriented layer of nematic liquid crystal (N-(methoxybenzylidene)-4-butylaniline) driven to the turbulence by an external ac voltage is reported. The time behaviour of the transmitted light polarization degree (P) has been recorded for different values of both applied voltage and polarization of the incident

Langmuir, 2013

We have developed a noninvasive, all-optical, holographic technique for permanently aligning liqu... more We have developed a noninvasive, all-optical, holographic technique for permanently aligning liquid crystalline DNA filaments in a microperiodic template realized in soft-composite (polymeric) materials. By combining optical intensity holography with a selective microfluidic etching process, a channelled microstructure has been realized which enables self-assembly of DNA. The striking chemicophysical properties of the structure immobilize the DNA filaments within the microchannels without the need of any kind of surface chemistry or functionalization. Polarized optical, confocal, and electronic microscopies have been used for characterizing the DNA geometry inside the microchannels in terms of birefringence, fluorescence, and nanoscale organization properties. In particular, observation of a far-field diffraction pattern confirms a periodic organization of the DNA filaments inside the polymeric template.