Preparation of a novel polysulfone/polyethylene oxide/silicone rubber multilayer composite membrane for hydrogen-nitrogen separation

A novel poly sulfone/polyethylene oxide/silicone rubber (PSOPEO/SR) multilayer composite membrane was fabricated by double coating polysulfone substrate membrane with polyethylene oxide and silicone rubber. Gas permeation experiments were performed at 30 degrees C for hydrogen and nitrogen. PSf(PEO/SR membrane displayed high and steady performance for H-2/N-2: permeances of H-2 and N-2 of 49.51 and 0.601 GPU, respectively, and H-2/N-2 ideal separation factor of 82.3. It was explained that layer interfaces due to the introduction of PEO layer act as the permselective media and are responsible for the higher H-2/N-2 ideal separation factor which has exceeded the intrinsic permselectivities of the three polymers used in this study. (c) 2005 Elsevier B.V. All rights reserved.

Glucose-Triggered Drug Delivery from Borate Mediated Layer-by-Layer Self-Assembly

In this study, we report a novel approach for glucose-triggered anticancer drug delivery from the self-assembly of neutral poly(vinyln alcohol) (PVA) and chitosan. In the present study, we have fabricated multilayer thin film of PVA-borate and chitosan on colloidal particle (MF particle) and monitored the layer-by-layer growth using Zetapotential measurements. Formation of multilayer membrane on MF particle has been further characterized with transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM). Subsequently,disintegration of multilayer thin film and microcapsules was observed in presence of glucose. We investigated the disassembly of PVA-borate and chitosan self-assembly under CLSM and atomic force microscopy. These results suggest that this multilayer thin film is very efficient for encapsulation and release of DOX molecules above certain concentration of glucose (25 mM). This glucose-sensitive self-assembly is relevant for the application of anticancer therapeutic drug delivery.

3D thermo-electro-mechanical simulations of gas sensors based on SOI membranes

3D thermo-electro-mechanical device simulations are presented of a novel fully CMOS-compatible MOSFET gas sensor operating in a SOI membrane. A comprehensive stress analysis of a Si-SiO2-based multilayer membrane has been performed to ensure a high degree of mechanical reliability at a high operating temperature (e.g. up to 400°C). Moreover, optimisation of the layout dimensions of the SOI membrane, in particular the aspect ratio between the membrane length and membrane thickness, has been carried out to find the best trade-off between minimal device power consumption and acceptable mechanical stress.

Self-assembled multilayer graphene oxide membrane and carbon nanotubes synthesized using a rare form of natural graphite

The fabrication of flexible multilayer graphene oxide (GO) membrane and carbon nanotubes (CNTs) using a rare form of high-purity natural graphite, vein graphite, is reported for the first time. Graphite oxide is synthesized using vein graphite following Hummer's method. By facilitating functionalized graphene sheets in graphite oxide to self-assemble, a multilayer GO membrane is fabricated. Electric arc discharge is used to synthesis CNTs from vein graphite. Both multilayer GO membrane and CNTs are investigated using microscopy and spectroscopy experiments, i.e., scanning electron microscopy (SEM), atomic force microscopy (AFM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), core level photoelectron spectroscopy, and C K-edge X-ray absorption spectroscopy (NEXAFS), to characterize their structural and topographical properties. Characterization of vein graphite using different techniques reveals that it has a large number of crystallites, hence the large number of graphene sheets per crystallite, preferentially oriented along the (002) plane. NEXAFS and core level spectra confirm that vein graphite is highly crystalline and pure. Fourier transform infrared (FT-IR) and C 1s core level spectra show that oxygen functionalities (-C-OH, -CO,-C-O-C-) are introduced into the basal plane of graphite following chemical oxidation. Carbon nanotubes are produced from vein graphite through arc discharge without the use of any catalyst. HRTEM confirm that multiwalled carbon nanotube (MWNTs) are produced with the presence of some structure in the central pipe. A small percentage of single-walled nanotubes (SWNTs) are also produced simultaneously with MWNTs. Spectroscopic and microscopic data are further discussed here with a view to using vein graphite as the source material for the synthesis of carbon nanomaterials. © 2013 American Chemical Society.

A novel PTFE-reinforced multilayer self-humidifying composite membrane for PEM fuel cells

A novel polytetrafluoroethylene (PTFE)-reinforced multilayer self-humidifying composite membrane is developed. The membrane is composed of Nafion-impregnated porous PTFE composite as the central layer and nanosized SiO2 supported Pt catalyst imbedded into Nafion as the two side layers. The proton exchange membrane (PEM) fuel cells employing the self-humidifying membrane (20 mu m thick) under dry H-2/O-2 gave a peak power density of 0.95 W/cm(2) and an open-circuit voltage of 1.032 V. The good membrane performance is attributed to hygroscopic Pt-SiO2 catalyst at the two side layers, which results in enhanced anode side self-humidification function and decreased cathode polarization. (c) 2005 The Electrochemical Society.

Gelatin multilayer assembled on the poly(L-lactic acid) surface for better cytocompatibility

Gelatin multilayers were assembled on PLLA substrate at pH 3, 5, and 7, which was below, around, and above the isoelectric point of the amphoteric polymer, using the layer-by-layer assembly technique. The multilayer deposition on the PLLA substrate was monitored by X-ray photoelectron spectroscopy (XPS) and water contact angle measurement. The XPS, water contact angle, and atomic force microscopy data indicated that the layer thickness, surface hydrophicity, and surface morphology of the gelatin multilayers assembled strongly depended on the pH at which the layers were deposited

Chlorine tolerant, multilayer reverse-somosis membranes with high permeate flux and high salt rejection

A new class of high molecular weight polyethersulfone ionomers is described in which the ionic content can be varied, at will, over a very wide and fully-controllable range. A novel type of coating process enables these materials to be deposited from alcohol-type solvents as cohesive but very thin (50 – 250 nm) films on porous support-membranes, giving high-flux membranes (3.3 – 5.0 L m-2 h-1 bar-1) with very good, though not outstanding salt rejection (typically 92 - 96%). A secondary layer, of formaldehyde-cross-linked polyvinyl alcohol, can be deposited from aqueous solution on the surface of the ionomer membrane, and this layer increases salt rejection to greater than 99% without serious loss of water permeability. The final multi-layer membrane shows excellent chlorine tolerance in reverse-osmosis operation.

Immobilization of Poly(propylene imine) Dendrimer/Nickel Phtalocyanine as Nanostructured Multilayer Films To Be Used as Gate Membranes for SEGFET pH Sensors

We describe the assembly of layer-by-layer films based on the poly(propylene imine) dendrimer (PPID) generation 3 and nickel tetrasulfonated phthalocyanine (NiTsPc) for application as chemically sensitive membranes in sepal alive extended-gate field effect transistor (SEGFET) pH sensors PPID/NiTsPc films wet e adsorbed on quartz, glass. indium tin oxide. or gold (Au)-covered glass substrates Multilayer formation was monitored via UV-vis absorption upon following the increment in the Q-band intensity (615 nm) of NiTsPc The nanostructured membranes were very stable in a pH range of 4-10 and displayed a good sensitivity toward H(+), ca 30 mV/pH for PPID/N(1)TsPc films deposited on Au-covered substrates For films deposited on ITO, the sensitivity was ca 52 4 mV/pH. close to the expected theoretical value for ton-sensitive membranes. The use of chemically stable PPID/NiTsPc films as gate membranes in SEGFETs, as introduced here, may represent an alternative for the fabrication of nanostructured, porous platforms for enzyme immobilization to be used in enzymatic biosensors.

Caratterizzazione di membrane da nanofiltrazione

Nanofiltration (NF) is a pressure-driven membrane process, intermediate between reverse osmosis and ultrafiltration. Commercially available polymeric membranes have been used in a wide range of applications, such as drinking, process industry and waste water treatment. For all the applications requiring high stability and harsh washing procedures inorganic membranes are preferred due to their high chemical inertia. Typically, γ – Al2O3 as well as TiO2 and ZrO2 selective layers are used; the latter show higher chemical stability in a wide range of pH and temperatures. In this work the experimental characterization of two different type of membrane has been performed in order to investigate permeation properties, separation performance and efficiency with aqueous solutions containing strong inorganic electrolytes. The influence of salt concentration and feed pH as well as the role of concentration polarization and electrolyte type on the membrane behavior are investigated. Experimentation was performed testing a multi–layer structured NF membrane in α-Al2O3, TiO2 and ZrO2, and a polymeric membrane, in polyamide supported on polysulfone, with binary aqueous solutions containing NaCl, Na2SO4 or CaCl2; the effect of salt composition and pH in the feed side was studied both on flux and salt rejection. All the NF experimental data available for the two membranes were used to evaluate the volumetric membrane charge (X) corresponding to each operative conditions investigated, through the Donnan Steric Pore Model and Dielectric Exclusion (DSPM&DE). The results obtained allow to understand which are the main phenomena at the basis of the different behaviors observed.

Développement et caractérisation de nouveaux nanocomposites polymères électriquement conductueurs pour plaques bipolaires de piles à combustible à membrane échangeuse de protons, PEMFC

Face à la diminution des ressources énergétiques et à l’augmentation de la pollution des énergies fossiles, de très nombreuses recherches sont actuellement menées pour produire de l’énergie propre et durable et pour réduire l’utilisation des sources d’énergies fossiles caractérisées par leur production intrinsèque des gaz à effet de serre. La pile à combustible à membrane échangeuse de protons (PEMFC) est une technologie qui prend de plus en plus d’ampleur pour produire l’énergie qui s’inscrit dans un contexte de développement durable. La PEMFC est un dispositif électrochimique qui fonctionne selon le principe inverse de l’électrolyse de l’eau. Elle convertit l’énergie de la réaction chimique entre l’hydrogène et l’oxygène (ou l’air) en puissance électrique, chaleur et eau; son seul rejet dans l’atmosphère est de la vapeur d’eau. Une pile de type PEMFC est constituée d’un empilement Électrode-Membrane-Électrode (EME) où la membrane consiste en un électrolyte polymère solide séparant les deux électrodes (l’anode et la cathode). Cet ensemble est intégré entre deux plaques bipolaires (BP) qui permettent de collecter le courant électrique et de distribuer les gaz grâce à des chemins de circulation gravés sur chacune de ses deux faces. La plupart des recherches focalisent sur la PEMFC afin d’améliorer ses performances électriques et sa durabilité et aussi de réduire son coût de production. Ces recherches portent sur le développement et la caractérisation des divers éléments de ce type de pile; y compris les éléments les plus coûteux et les plus massifs, tels que les plaques bipolaires. La conception de ces plaques doit tenir compte de plusieurs paramètres : elles doivent posséder une bonne perméabilité aux gaz et doivent combiner les propriétés de résistance mécanique, de stabilité chimique et thermique ainsi qu’une conductivité électrique élevée. Elles doivent aussi permettre d’évacuer adéquatement la chaleur générée dans le cœur de la cellule. Les plaques bipolaires métalliques sont pénalisées par leur faible résistance à la corrosion et celles en graphite sont fragiles et leur coût de fabrication est élevé (dû aux phases d’usinage des canaux de cheminement des gaz). C’est pourquoi de nombreuses recherches sont orientées vers le développement d’un nouveau concept de plaques bipolaires. La voie la plus prometteuse est de remplacer les matériaux métalliques et le graphite par des composites à matrice polymère. Les plaques bipolaires composites apparaissent attrayantes en raison de leur facilité de mise en œuvre et leur faible coût de production mais nécessitent une amélioration de leurs propriétés électriques et mécaniques, d’où l’objectif principal de cette thèse dans laquelle on propose: i) un matériau nanocomposite développé par extrusion bi-vis qui est à base de polymères chargés d’additifs solides conducteurs, incluant des nanotubes de carbone. ii) fabriquer un prototype de plaque bipolaire à partir de ces matériaux en utilisant le procédé de compression à chaud avec un refroidissement contrôlé. Dans ce projet, deux polymères thermoplastiques ont été utilisés, le polyfluorure de vinylidène (PVDF) et le polyéthylène téréphtalate (PET). Les charges électriquement conductrices sélectionnées sont: le noir de carbone, le graphite et les nanotubes de carbones. La combinaison de ces charges conductrices a été aussi étudiée visant à obtenir des formulations optimisées. La conductivité électrique à travers l’épaisseur des échantillons développés ainsi que leurs propriétés mécaniques ont été soigneusement caractérisées. Les résultats ont montré que non seulement la combinaison entre les charges conductrices influence les propriétés électriques et mécaniques des prototypes développés, mais aussi la distribution de ces charges (qui de son côté dépend de leur nature, leur taille et leurs propriétés de surface), avait aidé à améliorer les propriétés visées. Il a été observé que le traitement de surface des nanotubes de carbone avait aidé à l’amélioration de la conductivité électrique et la résistance mécanique des prototypes. Le taux de cristallinité généré durant le procédé de moulage par compression des prototypes de plaques bipolaires ainsi que la cinétique de cristallisation jouent un rôle important pour l’optimisation des propriétés électriques et mécaniques visées.

Membrane associated transporter protein gene (SLC45A2) and the genetic basis of normal human pigmentation variation

This work is concerned with the genetic basis of normal human pigmentation variation. Specifically, the role of polymorphisms within the solute carrier family 45 member 2 (SLC45A2 or membrane associated transporter protein; MATP) gene were investigated with respect to variation in hair, skin and eye colour ― both between and within populations. SLC45A2 is an important regulator of melanin production and mutations in the gene underly the most recently identified form of oculocutaneous albinism. There is evidence to suggest that non-synonymous polymorphisms in SLC45A2 are associated with normal pigmentation variation between populations. Therefore, the underlying hypothesis of this thesis is that polymorphisms in SLC45A2 will alter the function or regulation of the protein, thereby altering the important role it plays in melanogenesis and providing a mechanism for normal pigmentation variation. In order to investigate the role that SLC45A2 polymorphisms play in human pigmentation variation, a DNA database was established which collected pigmentation phenotypic information and blood samples of more than 700 individuals. This database was used as the foundation for two association studies outlined in this thesis, the first of which involved genotyping two previously-described non-synonymous polymorphisms, p.Glu272Lys and p.Phe374Leu, in four different population groups. For both polymorphisms, allele frequencies were significantly different between population groups and the 272Lys and 374Leu alleles were strongly associated with black hair, brown eyes and olive skin colour in Caucasians. This was the first report to show that SLC45A2 polymorphisms were associated with normal human intra-population pigmentation variation. The second association study involved genotyping several SLC45A2 promoter polymorphisms to determine if they also played a role in pigmentation variation. Firstly, the transcription start site (TSS), and hence putative proximal promoter region, was identified using 5' RNA ligase mediated rapid amplification of cDNA ends (RLM-RACE). Two alternate TSSs were identified and the putative promoter region was screened for novel polymorphisms using denaturing high performance liquid chromatography (dHPLC). A novel duplication (c.–1176_–1174dupAAT) was identified along with other previously described single nucleotide polymorphisms (c.–1721C>G and c.–1169G>A). Strong linkage disequilibrium ensured that all three polymorphisms were associated with skin colour such that the –1721G, +dup and –1169A alleles were associated with olive skin in Caucasians. No linkage disequilibrium was observed between the promoter and coding region polymorphisms, suggesting independent effects. The association analyses were complemented with functional data, showing that the –1721G, +dup and –1169A alleles significantly decreased SLC45A2 transcriptional activity. Based on in silico bioinformatic analysis that showed these alleles remove a microphthalmia-associated transcription factor (MITF) binding site, and that MITF is a known regulator of SLC45A2 (Baxter and Pavan, 2002; Du and Fisher, 2002), it was postulated that SLC45A2 promoter polymorphisms could contribute to the regulation of pigmentation by altering MITF binding affinity. Further characterisation of the SLC45A2 promoter was carried out using luciferase reporter assays to determine the transcriptional activity of different regions of the promoter. Five constructs were designed of increasing length and their promoter activity evaluated. Constitutive promoter activity was observed within the first ~200 bp and promoter activity increased as the construct size increased. The functional impact of the –1721G, +dup and –1169A alleles, which removed a MITF consensus binding site, were assessed using electrophoretic mobility shift assays (EMSA) and expression analysis of genotyped melanoblast and melanocyte cell lines. EMSA results confirmed that the promoter polymorphisms affected DNA-protein binding. Interestingly, however, the protein/s involved were not MITF, or at least MITF was not the protein directly binding to the DNA. In an effort to more thoroughly characterise the functional consequences of SLC45A2 promoter polymorphisms, the mRNA expression levels of SLC45A2 and MITF were determined in melanocyte/melanoblast cell lines. Based on SLC45A2’s role in processing and trafficking TYRP1 from the trans-Golgi network to stage 2 melanosmes, the mRNA expression of TYRP1 was also investigated. Expression results suggested a coordinated expression of pigmentation genes. This thesis has substantially contributed to the field of pigmentation by showing that SLC45A2 polymorphisms not only show allele frequency differences between population groups, but also contribute to normal pigmentation variation within a Caucasian population. In addition, promoter polymorphisms have been shown to have functional consequences for SLC45A2 transcription and the expression of other pigmentation genes. Combined, the data presented in this work supports the notion that SLC45A2 is an important contributor to normal pigmentation variation and should be the target of further research to elucidate its role in determining pigmentation phenotypes. Understanding SLC45A2’s function may lead to the development of therapeutic interventions for oculocutaneous albinism and other disorders of pigmentation. It may also help in our understanding of skin cancer susceptibility and evolutionary adaptation to different UV environments, and contribute to the forensic application of pigmentation phenotype prediction.

Expression of Potato virus Y cytoplasmic inclusion protein in tobacco results in disorganization of parenchyma cells, distortion of epidermal cells, and induces mitochondrial and chloroplast abnormalities, formation of membrane whorls and atypical lipid accumulation

Infection of plant cells by potyviruses induces the formation of cytoplasmic inclusions ranging in size from 200 to 1000 nm. To determine if the ability to form these ordered, insoluble structures is intrinsic to the potyviral cytoplasmic inclusion protein, we have expressed the cytoplasmic inclusion protein from Potato virus Y in tobacco under the control of the chrysanthemum ribulose-1,5-bisphosphate carboxylase small subunit promoter, a highly active, green tissue promoter. No cytoplasmic inclusions were observed in the leaves of transgenic tobacco using transmission electron microscopy, despite being able to clearly visualize these inclusions in Potato virus Y infected tobacco leaves under the same conditions. However, we did observe a wide range of tissue and sub-cellular abnormalities associated with the expression of the Potato virus Y cytoplasmic inclusion protein. These changes included the disruption of normal cell morphology and organization in leaves, mitochondrial and chloroplast internal reorganization, and the formation of atypical lipid accumulations. Despite these significant structural changes, however, transgenic tobacco plants were viable and the results are discussed in the context of potyviral cytoplasmic inclusion protein function.