Patrizia Formoso

Light Responsive Polymer Membranes: A Review

In recent years, stimuli responsive materials have gained significant attention in membrane separation processes due to their ability to change specific properties in response to small external stimuli, such as light, pH, temperature, ionic strength, pressure, magnetic field, antigen, chemical composition, and so on. In this review, we briefly report recent progresses in light-driven materials and membranes. Photo-switching mechanisms, valved-membrane fabrication and light-driven properties are examined. Advances and perspectives of light responsive polymer membranes in biotechnology, chemistry and biology areas are discussed.

Nanotechnology for the Environment and Medicine.

Nanotechnology encompasses the production and applications of physical, chemical, and biological systems at scales ranging from individual atoms or molecules to around 100 nanometres, as well as the integration of the resulting nanostructures into larger systems. Nanomaterials differ from bulk materials for their relatively larger surface-area-to-mass ratio, consequently they become more chemically reactive and can show different optical, magnetic and electrical behaviours. In recent years, engineered nanomaterials have gained a particular attention in some fields such as environmental protection (soil, air and water remediation/treatment) and medicine (bio-sensing, imaging, and drug delivery). Nanoparticles can be used to monitor in real-time some pollutants (including heavy metal ions, organic compounds, microbiological pathogens, etc.) present even at extremely low concentrations in different environments. The use of nanomaterials for waste remediation/treatment results in a technology more cost-effective and rapid than current conventional approaches thanks to their enhanced surface area, transport properties, and sequestration characteristics. In addition, the integration of molecular biology and medicine with nanotechnology has resulted in new active nanostructures able to interact with biological systems. Nanocarriers based on carbon nanotubes, fumed silica (SiO2), titanium dioxide (TiO2), and magnetite and maghemite (Fe3O4, and γ-Fe2O3) nanoparticles have a distinct advantage over other drug carriers as they can be opportunely designed to reach the desired targets. As a consequence, such nanostructures can represent an important platform for enhanced medical imaging and controlled drug delivery. Here, some applications of nanomaterials as water purifying agents and drug delivery systems are reported.

Chromatic and dynamic characteristics of some photochromes in the components of bifunctional photochromic and electro-optical devices

This work is part of a research project whose final aim is to realise prototypes of bifunctional photochromic and electro-optical devices. The photochrome will be incorporated in films composed by nematic liquid crystals dispersed in a polymeric matrix or in fluid monomer emulsions. To choose suitable photochromic components, the behaviour of some compounds (four naphtho-spiro-indolino-oxazines and a nitromethoxy-spiropyran) was investigated in the components of the matrix (liquid crystals and monomers) and compared with that in organic solvents. The colour-forming and colour-bleaching kinetics were determined. The molecules investigated, while maintaining their photochromic behaviour, generally exhibited a better colorability in liquid crystals and monomers, due to decreasing of the bleaching rate. The results of this work indicate that two of the molecules investigated have the prerequisites of colorability, reversibility and durability to be used in the bifunctional devices. Preliminary tests on the behaviour of a prototype of bifunctional film are reported.

Photoelectrochromic switchable nematic emulsions

Switchable nematic emulsions are composite systems formed by liquid-crystal droplets dispersed in a fluid, homogeneous, monomer matrix. These systems can be switched from an opaque to a transparent state by application of a suitable alternating electric field. An electrochromic device provides a reversible and visible change in its transmittance as a result of either oxidizing or reducing electrochemical processes. A photochromic device provides a reversible and visible change in its transmittance as the result of a single chemical transformation of the species induced by suitable electromagnetic radiation. These devices have been proven to be useful for a variety of electro-optical applications as switchable windows, electromagnetic shutters, and displays. Our article reports preliminary results on trifunctional devices based on nematic emulsions that host electrochromic and photochromic guest molecules. These trifunctional films are able to modulate the light transmission (with an external alternating electric field) and to change their color (with static field or UV light) by means of suitable electric fields or electromagnetic radiation.

Prototypes of bifunctional photochromic and electro-optical systems

Two types of bifunctional films having both electro-optical and photochromic properties have been prepared and investigated. These films are able to modulate the light transmission by means of suitable electric fields and to change their color under light irradiation. One of the films is fluid-like, being an emulsion of a liquid crystal and a photochrome in an organic monomer. It is defined as a photochromic emulsion dispersed liquid crystal (PEDLC). The other film is solid, having the structure of a polymer dispersed liquid crystal and containing a small percentage of photochrome; it is defined as a photochromic polymer dispersed liquid crystal (PPDLC). The solid films were obtained by photopolymerizing the fluid one. The electro-optical and photochromic properties of these films were investigated. To choose suitable photochromic components, the color-forming and color-bleaching kinetics of some compounds of the classes of spiro-oxazines and spiropyrans were preliminarily investigated in the components o...

Electro-Conductive Membranes for Permeation Enhancement and Fouling Mitigation: A Short Review

The research on electro-conductive membranes has expanded in recent years. These membranes have strong prospective as key components in next generation water treatment plants because they are engineered in order to enhance their performance in terms of separation, flux, fouling potential, and permselectivity. The present review summarizes recent developments in the preparation of electro-conductive membranes and the mechanisms of their response to external electric voltages in order to obtain an improvement in permeation and mitigation in the fouling growth. In particular, this paper deals with the properties of electro-conductive polymers and the preparation of electro-conductive polymer membranes with a focus on responsive membranes based on polyaniline, polypyrrole and carbon nanotubes. Then, some examples of electro-conductive membranes for permeation enhancement and fouling mitigation by electrostatic repulsion, hydrogen peroxide generation and electrochemical oxidation will be presented.

Gellan gum hybrid hydrogels for the cleaning of paper artworks contaminated with Aspergillus versicolor

Abstract The degradation of archive materials is related to irreversible phenomena induced by light, temperature, humidity, air pollution, micro-organisms, and use. Among biological factors, fungi can induce harmful effects in paper artworks. Further forms of damage (e.g. artwork swelling, fibre lifting and sheet delamination) can be caused by water immersion, which is one of the most commonly used methods for cleaning paper. To avoid damage it is necessary to control the amount and absorption rate of water by paper. Recently, gellan gum hydrogels have been proposed as effective tools to allow contaminant removal from paper supports, owing to the controlled water release and adhesive properties of gellan gum. In this study hybrid hydrogels were fabricated by doping gellan gum either with calcium compounds (calcium sulphate, hydroxide, chloride, and acetate) or titanium dioxide nanoparticles in order to evaluate their ability in cleaning different types of paper samples affected by spots originating from Aspergillus versicolor. The best decolourization results were obtained by calcium acetate/gellan gum hydrogels and titanium dioxide nanoparticle/gellan gum hydrogels, while no synergistic effect was found in paper samples treated with calcium acetate/titanium dioxide/gellan gum hydrogels. Hybrid hydrogels were tested on a case-study book.

Preparation and characterisation of bifunctional reverse-mode polymer-dispersed liquid crystals

ABSTRACT Reverse-mode polymer-dispersed liquid crystals (PDLCs) are transparent films in their OFF state (no applied electric field) and become opaque in their ON state. The addition of a photo-chromic compound allows a colour change of films, when they are ultraviolet (UV)-irradiated. The aim of this work was the preparation and characterisation of bifunctional materials, able to change their transparency by application of an electric field and colour under UV irradiation. In particular, the performance of reverse-mode PDLCs doped with different spiro(indolo)-oxazine molecules was investigated. Both the electro-optical and photo-chromic response of these systems were evaluated and compared.

Conformation of succinic acid: its pH dependence by Licry-NMR analysis

The conformations of fully protonated (H2SA), fully deprotonated (SA=) and monoprotonated (HSA-) succinic acid have been investigated by means of nuclear magnetic resonance spectroscopy in liquid crystal mesophases (Licry-NMR). H-H and 13C-H direct dipolar couplings have been determined by measuring 1H-NMR and 13C-NMR spectra from quaternary nematic-lyotropic solutions of myristyltrimethylammonium bromide (MTAB), decanol, deuterated water and succinic acid (in each of its three different protonated forms). Direct dipolar couplings have been used to investigate the conformational equilibrium of the molecule in its three different protonation forms. Data could be interpreted in terms of a single conformation for each of the investigated forms. The dihedral angle between the H3-C5′-C5 and the C5′-C5-H1 planes gradually increases when going from the fully protonated H2SA species to the SA= ions. Our findings are different from those obtained by other authors by analysis of Jij couplings. In that case an equil...

A new reverse mode light shutter from silica-dispersed liquid crystals

ABSTRACT Nanoparticle dispersions in liquid crystalline materials at low concentrations allow both investigating the formation of defects in liquid crystal (LC) and enhancing the light-scattering properties of LC optical devices. Reverse mode LC dispersions are LC devices, which look like transparent in their OFF state, when no electric field is applied, and opaque in their ON state. In this paper, a new reverse mode device, formed by a dispersion of a LC mixture in a silica nanoparticle crosslinked network, is presented. The morphology and the electro-optical properties of these silica nanoparticle/LC composites were investigated for two different LC mixtures with a negative dielectric anisotropy. The observed transmittances and relaxation times were found to depend strongly on the silica amount and chemical–physical properties of LC used in the sample preparation. GRAPHICAL ABSTRACT