Roles Of Preparation Method On Characteristics Of Supramolecular-structured Polymer Electrolyte Membrane Fuel Cell Based On Sulfonated Polystyrene

Polymer Electrolyte Membrane Fuel Cell with supramolecular structure based on Sulfonated Polystyrene (S-PS) have been developed in Research Centre for Physics LIPI. In forming the supramolecular structure sulfonate groups in S-PS are aligned with polyethylene-graft-maleic anhydride (PE-g-MA) which carried out by dissolution of the constituent and mixing of both. The alignment of sulfonate groups in s-PS is carried out in a liquid form. Therefore, in this study, the effect of concentration of the solution of both polymers constituent to the alignment of the sulfonate groups and the characteristics of the membrane produced is studied. Scanning ElectronMicroscope (SEM) images showthat allmembranes prepared are rigid. Differential Scanning Calorimetry (DSC) studied show very significance differences in its crystal sizes. XRD diffraction data also support the previous results. Membrane prepared from very dilute solution having better ion exchange capacity (IEC), water uptake and ionic conductivity. Therefore, the experiments results showing that very low concentration of polymer constituent, clearly, produced better interaction of both, which agree with hyphotesis in this work where supramolecular structure can be formed by mixing two very dilute polymer solutions

Correlated disorder in myelinated axons orientational geometry and structure

While the ultrastructure of the myelin has been considered to be a quasi-crystalline stable system, nowadays its multiscale complex dynamics appears to play a key role for its functionality, degeneration and repair processes following neurological diseases and trauma. In this work, we have investigated the axons interactions associated to the nerve functionality, measuring the spatial distribution of the orientational fluctuations of axons in a Xenopus Laevis sciatic nerve. At this aim, we have used Scanning micro X-ray Diffraction (SmXRD), a non-invasive already applied to other heterogeneous systems presenting complex geometries from microscale to nanoscale. We have found that the orientational spatial fluctuations of fresh axons show a correlated disorder described by Levy flight distribution. Thus, we have studied how this correlated disorder evolves during the degeneration of the nerve. Our results show that the spatial distribution of axons orientational fluctuations in unfresh, aged nerve loose the correlated disorder assuming a randomly disordered behaviour. This work allows a deeper understanding of nerve states and paves the way to study other materials and biomaterials with the same technique to detect and to characterize their states and supramolecular structure, associated with dynamic structural changes at the nanoscale and mesoscale.Comment: 9 pages, 4 figure

Characterization of hemodialysis membranes by inverse size exclusion chromatography

Inverse size exclusion chromatography (i-SEC) was used to characterize three different cellulosic hollow fiber hemodialysis membranes, i.e. low-flux cuprophan and hemophan and high-flux RC-HP400A. With the i-SEC technique the pore size distribution and porosity of a membrane can be determined and adsorption phenomena can be studied. The membranes showed clear differences in pore size and porosity, the high-flux RC-HP400A membrane has a larger pore size as well as a higher porosity. For all the membranes it was found that the elution curves were best described by a homoporous pore volume distribution. It appeared that the bound or non-freezing water in the membranes was at least partly accessible to solutes. The test molecules creatinine and vitamin B 12 both adsorbed to the cellulosic membranes. The adsorption behavior of creatinine was strongly dependent on the NaCl concentration present. The observations could be explained by assuming that cuprophan and RC-HP400A are negatively charged whereas hemophan is positively charged due to the modification with N,N-diethylaminoethyl ether. The net charge of the hemophan is smaller

A dsorption studies of malachite green dye on mesoporous silica synthesized in 1-octyl-3-methylimidazolium chloride ionic liquid

In this work, one long-chain ionic liquid (IL), 1-octyl-3-methylimidazolium chloride, was used as a template for the preparation of mesoporous silica via a modified sol-gel route. The morphology of the obtained material was characterized by scanning electron microscopy (SEM). The various vibrational modes of different functional groups in the mesoporous silica materials were revealed by Fourier transform infrared (FTIR) spectroscopy. N2 adsorption-desorption isotherms measurement was used to characterize the pore diameter and BET surface area. The adsorption capacity of malachite green dye from aqueous solution has been performed using the mesoporous silica synthesized in ionic liquid. The adsorption equilibrium of dye on mesoporous silica was found to be at 150 min. The maximum malachite green dye adsorption was found to be 97 %

Diffusion of single dye molecules in hydrated TiO 2 mesoporous films

Mesoporous oxide films are attractive frameworks in technological areas such as catalysis, sensing, environmental protection, and photovoltaics. Herein, we used fluorescence correlation spectroscopy to explore how the pore dimensions of hydrated TiO2 mesoporous calcined films modulate the molecular diffusion. Rhodamine B molecules in mesoporous films follow a Fickian process 2–3 orders slower compared to the probe in water. The mobility increases with the pore and neck radii reaching an approximately constant value for a neck radius >2.8 nm. However, the pore size does not control the dye diffusion at low ionic strength emphasizing the relevance of the probe interactions with the pore walls on dye mobility. In conclusion, our results show that the thermal conditioning of TiO2 mesoporous films provides an exceptional tool for controlling the pore and neck radii on the nanometer scale and has a major impact on molecular diffusion within the mesoporous network.Fil: Angiolini, Juan Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Stortz, Martin Dario. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Steinberg, Paula Yael. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mocskos, Esteban Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Simulación Computacional para Aplicaciones Tecnológicas; ArgentinaFil: Bruno, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Soler Illia, Galo Juan de Avila Arturo. Universidad Nacional de San Martin. Instituto de Nanosistemas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Angelome, Paula Cecilia. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Wolosiuk, Alejandro. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Levi, Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; Argentin

Calix[n]arene-based Monolayer Protected Clusters (MPCs): Synthesis, Studies and Applications

This thesis deals with the synthesis, characterization and study of metallic nanoparticles (M = Au, Pd, Ag, Cd-Se) functionalized on their surface with calix[n]arene derivatives. These hybrid organic-inorganic materials, more commonly called "monolayer-protected clusters" (MPCs), have recently attracted a growing scientific interest for their potential applications in catalysis, in the realization of optical devices, electrical or magnetic sensors or more in general in the field of nanotechnology. In each of these applications the control, during the preparation, of the size of the nanoparticles obtained is important. The idea of preparing MPCs stabilized on their surface with macrocyclic receptors came from the possibility of combining the recognition properties of calix[n]arene derivatives with the typical properties of metal colloids in order to obtain "smart" material capable of interesting functions, that are able to perform actions in response to external chemical or electrochemical stimuli. In the first phase of the thesis it has developed new synthetic methodologies of calix[n]arene derivatives functionalized at the lower rim with alkyl chain bearing, at their ends, thiols functional groups suitable for covalent binding on metal surfaces. In a second phase it has developed reproducible synthetic methodologies for the preparation of metal nanoparticles having a core size between 0.8 -7 nm functionalized with calix[n]arene derivatives. This study has allowed us to evaluate various experimental parameters that lead to obtain size controlled and monodisperse gold nanoparticles, such as reaction temperature, duration, stochiometry of thiols and gold etc.. These studies have highlighted in particular the "denticity" of the ligand (number of thiolic chains on macrocycle) on the size and stability of such systems. All prepared nonosystems are studied by microscopic (TEM), superficial analysis (XPS, XRD), spettrometric techniques (NMR, UV-vis) and chemical techniques (elemental analysis and TGA). These thiolic derivatives were also used for the surface coating of Cd-Se semiconductor nanoparticles for the preparation of Quantum Dots-in collaboration with the University of Miami (USA). Such synthesized organic-inorganic hybrid materials were subsequently used for processes of self-assembly in solution exploiting the receptor capabilities of calix[n]arene derivatives on the surface with piridinium salts. These studies, conducted at the University of Konstanz (Germany), had been conducted using optical techniques (UV-vis and Dynamic Light Scattering) and have shown the aggregation processes in solution and the structural properties of such systems.Questo lavoro di tesi riguarda la sintesi, la caratterizzazione e lo studio di nanoparticelle metalliche ( M = Au, Pd, Ag e Cd-Se) funzionalizzate sulla loro superficie con derivati macrociclici di tipo calix[n]arenico. Questi materiali ibridi organici-inorganici, più comunemente chiamati “monolayer-protected clusters” (MPCs), hanno recentemente attirato un crescente interesse scientifico per le loro potenziali applicazioni nella catalisi, nella realizzazione di congegni ottici, elettrici o magnetici, nella sensoristica o più in generale nel campo delle nanotecnologie. In ciascuna di queste applicazioni è di primaria importanza il controllo, durante la fase di preparazione, delle dimensioni delle nanoparticelle ottenute. L’idea di preparare MPCs stabilizzati superficialmente con recettori macrociclici nasce dalla possibilità di coniugare le capacità recettoriali dei derivati calix[n]arenici con le proprietà tipiche dei colloidi metallici in modo da realizzare materiali “intelligenti” capaci di interessanti funzioni, cioè in grado di effettuare azioni in risposta a stimoli esterni di tipo chimico o elettrochimico. Nella prima fase della tesi si sono sviluppate le metodologie sintetiche di derivati calix[n]arenici opportunamente sul bordo inferiore con catene alchiliche recanti alle loro estremità gruppi funzionali tiolici adatti all’ancoraggio covalente dei macrocicli sulle superfici metalliche. In una seconda fase si è passati allo sviluppo di valide e riproducibili metodologie di sintesi volte alla preparazione di nanoparticelle metalliche di dimensioni tra 0.8 -7 nm, funzionalizzate con i diversi derivati calix[n]arenici preparati. Questo studio ha permesso di valutare diversi paramentri sperimentali che portano all’ottenimento di nanoparticelle monodisperse di oro di dimensione controllata quali ad esempio la temperatura di reazione, durata, rapporto stechiometrico legante tiolico e aurato ecc. Questi studi hanno evidenziato in modo particolare la “identicità” del legante(numero di catene tioliche presenti sul macrociclo) sulle dimensioni e sulla stabilità di tali sistemi. Tutti i nanosistemi preparati sono stati caratterizzati mediante tecniche microscopiche (TEM), di analisi superficiale (XPS,XRD), spettrometriche (NMR, UV-vis) e chimiche (analisi elementare e TGA). Alcuni derivati tiolici sono stati inoltre impiegati per il coating superficiale di nanoparticelle semiconduttrici di Cd-Se per la preparazione di Quantum-Dots in collaborazione con l’University of Miami (USA). I materiali ibridi organici-inorganici sintetizzati sono stati successivamente utilizzati per processi di self-assembly in soluzione sfruttando le capacità recettoriali dei derivati calix[n]arenici posti sulla superfice nei confronti di sali di piridinio elettrochimicamente attivi. Questi studi, effettuati presso l’Univeristà di Costanza (Germania) sono stati condotti mediante tecniche ottiche (UV-vis e Dynamic Light Scattering) che hanno permesso di constatare gli effettivi processi di aggregazione in soluzione e di valutarne le proprietà strutturali