1,721,050 research outputs found
Synthesis and nanostructuration of thin and conductive PEDOT films by liquid-phase polymerization
Full text linkConductive polymers (CPs) have represented a key research topic in the field of organic electronic devices, as alternatives to silicon-based technologies. Among them, poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the most used and investigated materials because of its good and tailorable electrical properties, transparency to visible light and environmental stability. For all these reasons, PEDOT has found applications in organic solar cells, supercapacitors, organic light-emitting diodes and nanostructured devices.
In this project, we studied the synthesis of this polymer using a liquid-phase polymerization process.[1]
This process involves the sequential deposition of an oxidant solution (vanadium pentoxide) and a monomer solution (EDOT) onto a glass substrate treated with piranha solution. The resulting film is washed with a solvent to eliminate the excess monomer and then subjected to annealing heat treatment.
To enhance the properties of the polymeric film, we varied the deposition time of the oxidizing solution, the rotation speed and the concentration of the oxidizing solution.
The analysis showed that the thickness of the polymeric film is primarily influenced by the deposition time of the oxidant solution.
Additionally, the concentration of the oxidant slightly affects the polymer thickness due to the varying viscosities of more and less concentrated solutions. We determined the morphology and thickness of the samples using optical profilometry and measured the conductivity of the samples with the Van der Pauw method using a 4-point probe in electrical contact with the polymeric film. A direct current is applied between the outer test leads, while a voltage drop is measured between the inner leads, providing the sheet resistance (Rs, measured in Ω/□).
We studied the nanostructuring process of the films using nanosphere lithography. To improve the deposition of nanospheres on the PEDOT layer, a silica one was applied to the film. This layer facilitated the formation of a monolayer of polystyrene particles, which was subsequently reduced using reactive ion etching (RIE).[2]
The resulting mask enabled the precise nanostructuring of the PEDOT films. By optimizing this process, we achieved PEDOT nanostructures with a high degree of order
Sintesi e nanostrutturazione di film sottili e conduttivi di PEDOT mediante polimerizzazione in fase liquida
No full textI polimeri conduttivi (CPs) rappresentano una valida alternativa alle tecnologie silicon-based nella produzione di dispositivi elettronici organici. Tra questi, il PEDOT ne è un esempio notevole grazie alle sue eccellenti proprietà elettriche, alla trasparenza e alla stabilità. Questo progetto si è concentrato sulla sintesi di film di PEDOT mediante polimerizzazione in fase liquida depositando sequenzialmente soluzioni di ossidante (V2O5) e monomero (EDOT) su substrati di vetro. Variabili come il tempo di deposizione dell'ossidante, la concentrazione e la velocità di rotazione sono state regolate per migliorare le proprietà del film. La conduttività è stata misurata con il metodo Van der Pauw. Inoltre, la nanostrutturazione precisa di film di PEDOT è stata ottenuta mediante “nanosphere lithography
Sintesi e nanostrutturazione di film di PEDOT sottil e conduttivi mediante polimerizzazione in fase liquida
Full text linkI polimeri conduttivi (CPs) rappresentano una valida alternativa alle tecnologie silicon-based nella produzione di dispositivi elettronici organici. Tra questi, il PEDOT ne è un esempio notevole grazie alle sue eccellenti proprietà elettriche, alla trasparenza e alla stabilità. Questo progetto si è concentrato sulla sintesi di film di PEDOT mediante polimerizzazione in fase liquida depositando sequenzialmente soluzioni di ossidante (V2O5) e monomero (EDOT) su substrati di vetro. Variabili come il tempo di deposizione dell'ossidante, la concentrazione e la velocità di rotazione sono state regolate per migliorare le proprietà del film. La conduttività è stata misurata con il metodo Van der Pauw. Inoltre, la nanostrutturazione precisa di film di PEDOT è stata ottenuta mediante “nanosphere lithography
Nanoparticles for delivery of a pharmacologically active agent (United Kingdom Patent application)
No full textField of Invention.
The present invention relates to core-shell nanoparticles, processes for preparing them, and their use as carriers able to reversibly bind and deliver pharmacologically active substances, in particular nucleic acids, including natural and modified (deoxy)ribonucleotides (DNA, RNA), oligo(deoxy)nucleotides (ODNs) and proteins into cells
Polymer nanoparticle identification and concentration measurement using fiber-enhanced raman spectroscopy
Full text linkWe present a measurement technique for chemical identification and concentration measurement of polymer nanoparticles in aqueous solution, which is achieved using Raman spectroscopy. This work delivers an improvement in measurement sensitivity of 40 times over conventional Raman measurements in cuvettes by loading polymer nanoparticles into the hollow core of a microstructured optical fiber. We apply this "fiber-enhanced" system to measure the concentration of two separate samples of polystyrene particles (diameters of 60 nm and 120 nm respectively) with concentrations in the range from 0.07 to 0.5 mg/mL. The nanoliter volume formed by the fiber presents unique experimental conditions where nanoparticles are confined within the fiber core and prevented from diffusing outside the incident electromagnetic field, thereby enhancing their interaction. Our results suggest an upper limit on the size of particle that can be measured using the hollow-core photonic crystal fiber, as the increasing angular distribution of scattered light with particle size exceeds the acceptance angle of the liquid-filled fiber. We investigate parameters such as the fiber filling rate and optical properties of the filled fiber, with the aim to deliver repeatable and quantifiable measurements. This study thereby aids the on-going process to create compact systems that can be integrated into nanoparticle production settings for in-line measurements
Functional polymeric nano/microparticles for protein and DNA vaccine delivery.
No full textThe use of particulate polymeric carriers holds great promise for the development of effective and affordable DNA and protein subunit vaccines. Rational development of such vaccine formulations requires a detailed understanding of their physico-chemical properties, cell-free and in vitro behaviour, in addition to particle uptake and processing mechanisms to antigen presenting cells capable of stimulating safe and effective immune responses. We here provide an overview on functional polymeric nano- and micro-particles designed for surface adsorption of proteins and DNA antigens currently under investigation for the formulation of new vaccines, including comments on their preparation method, antigen delivery strategy, cell-free and in vitro behaviour. In addition, we focus on their influence in activating antigen-specific humoral and/or cellular immune responses and on their potential for the development of new vaccines
Determining nonuniformities of core‐shell nanoparticle coatings by analysis of the inelastic background of X‐ray photoelectron spectroscopy survey spectra
Full text linkMost real core‐shell nanoparticle (CSNP) samples deviate from an ideal core‐shell structure potentially having significant impact on the particle properties. An ideal structure displays a spherical core fully encapsulated by a shell of homogeneous thickness, and all particles in the sample exhibit the same shell thickness. Therefore, analytical techniques are required that can identify and characterize such deviations. This study demonstrates that by analysis of the inelastic background in X‐ray photoelectron spectroscopy (XPS) survey spectra, the following types of deviations can be identified and quantified: the nonuniformity of the shell thickness within a nanoparticle sample and the incomplete encapsulation of the cores by the shell material. Furthermore, CSNP shell thicknesses and relative coverages can be obtained. These results allow for a quick and straightforward comparison between several batches of a specific CSNP, different coating approaches, and so forth. The presented XPS methodology requires a submonolayer distribution of CSNPs on a substrate. Poly(tetrafluoroethylene)‐poly(methyl methacrylate) and poly(tetrafluoroethylene)‐polystyrene polymer CSNPs serve as model systems to demonstrate the applicability of the approach.Peer Reviewe
Doping of silicon by phosphorus end-terminated polymers: Drive-in and activation of dopants
Full text linkAn effective doping technology for the precise control of P atom injection and activation into a semiconductor substrate is presented. Polystyrene polymers with a narrow molecular weight distribution and end-terminated with a P containing moiety are used to build up a phosphorus δ-layer to be used as the dopant source. P atoms are efficiently injected into the Si substrate by high temperature (900-1250 °C) thermal treatments. Temperature dependent (100-300 K) resistivity and Hall measurements in the van der Pauw configuration demonstrate high activation rates (ηa > 80%) of injected P atoms. This bottom-up approach holds promise for the development of a mild technology for efficient doping of semiconductors
SELF-HEALING AND SHAPE-MEMORY HYDROGELS BY MICELLAR POLYMERIZATION
No full textHydrogels are three-dimensional polymeric network with the capability to absorb a large amount of water or biological fluids. Usually, these materials are made of hydrophilic crosslinked polymer chains able to swell in water and present a soft rubbery consistency similar to living tissues. For this reason, hydrogels are used for biomedical, biotechnology and pharmaceutical applications [1,2]. The crosslinker nature separates hydrogels in two large families namely chemical or physical crosslinked. In the former, crosslinking is obtained by covalent bonding the chains either during the polymerization or in a post polymerization process [3]. In the latter, hydrogels are obtained using physical interaction such as hydrophobic association, ionic bond or hydrogen bond.
In this work we prepared physically crosslinked hydrogels by radical micellar polymerization. This type of polymerization involves a hydrophilic monomer (acrylamide), a hydrophobic monomer (octadecylacrylate, C18A), a surfactant (sodium dodecyl sulfate), and a salt (sodium chloride). The polymerization was initiated using a redox initiator consisting of ammonium persulfate and sodium metabisulfite. In addition, a multifunctional monomer, divinylbenzene (DVB), was used with the aim of creating branched chains and evaluating their effect on the material characteristics. Three series of samples were prepared by varying the amount of octadecylacrylate and divinylbenzene.
The samples were characterized with thermal (DSC) and rheological analysis, both before and after each purification steps. As the concentration of C18A increases, the amount of water within the hydrogels decreases. In addition, the melting and crystallization enthalpies of the hydrophobic domains increase, and in a parallel fashion an increase in mechanical modulus G' takes place.
Furthermore, as the DVB concentration increases, the water content decreases, and the mechanical modulus G’ increases. This effect is probably due to the formation of additional chemical crosslinkings within the polymer network.
The self-healing behavior of these materials was also demonstrated by several rheology measurements and other specific experiment. As the DVB concentration increases, the self-healing efficiency decrease and so does the shape-memory behavior. Heating the materials above Tm, hydrogels could be deformed into different shapes that can be fixed on cooling. Then, heating again above Tm, the original shape is recovered. This effect can be observed only for samples containing more than 20% of hydrophobic monomer
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