Monitoring concentration and magnetic field influence on asphaltene aggregation by NMR spectroscopy

Asfalteni predstavljaju najteže, najmanje reaktivne i najpolarnije frakcije sirove nafte. Sastoje se od aromatskih molekula supstituiranih alifatskim lancima, heteroatomima N, S i O te metala u tragovima, poput V, Ni i Fe. Ove kompleksne makromolekule sklone su stvaranju agregata, što uzrokuje poteškoće prilikom proizvodnje i transporta nafte. Agregacija asfaltena iz vakuumskog ostatka sirove nafte je u ovome radu proučavana spektroskopijom NMR korištenjem tehnika inverznog oporavka i DOSY NMR. OdreĎeno je koncentracijsko područje u kojem nastaju agregati u toluenu te je istražen utjecaj porfirina vanadija(IV), nikla(II) i željeza(III) na vrijednosti difuzijskih koeficijenata, relaksaciju i agregaciju asfaltena. Nakon dodatka porfirina nije zapažen utjecaj na difuzijske koeficijente i agregaciju, dok je izmjereno značajno smanjenje longitudinalnog vremena relaksacije jezgre 1H zbog paramagnetnog doprinosa metala. Na temelju izmjerenih difuzijskih koeficijenata izračunati su hidrodinamički radijusi i molekulske mase monomera i agregata asfaltena. Očekuje se da će dobiveni rezultati pridonijeti boljem razumijevanju procesa agregacije ovih spojeva.Aspahltenes represent the heaviest, least reactive and most polar fraction of crude oil. They consist of aromatic molecules substituted by aliphatic chains, heteroatoms N, S and O and trace amounts of metals, such as Ni, V and Fe. These complex macromolecules tend to form aggregates causing many problems in crude oil production and transportation. In this reserch, aggregation behavior of asphaltenes obtained from vaccum residue of crude oil distillation was investigated by applying inversion recovery and DOSY NMR techniques. The lowest aggregation concentration in toluene was determined and the influence of V(IV), Ni(II) and Fe(III) porphyrins on diffusion coefficient, relaxation and aggregation process was studied. The addition of metalloporphyrins significantly decreased longitudinal relaxation time due to the paramagnetic contribution, but no effect on diffusion coefficient was observed in used concentration range. Hydrodynamic radii and molecular weights of the studied compounds were calculated from their diffusion coefficients. It is expected that the presented results will contribute to better understanding the asphaltene aggregation process

funzionalizzazione ed applicazione di carbon nanohorns e carbon onions

2006/2007“Funzionalizzazione ed applicazione di carbon nanohorns e di carbon onions” Dalla scoperta della microscopia a scansione a sonda (SPM) nel 1980 a quella del fullerene, molti sono stati i premi Nobel nel campo delle Nanotecnologie. Diverse compagnie, attualmente, hanno investito fondi in questo settore. Ma cosa sono le Nanotecnologie? La parola e’utilizzata per descrivere diversi tipi di ricerca dove le dimensioni caratteristiche sono dell’ordine dei nanometri. I principali approcci impiegati nell’assemblaggio del materiale sono: “top-down” (dal più grande al più piccolo) e “bottom-up” (dal più piccolo al più grande). Il primo consiste nel ridurre le dimensioni della struttura fino alla nanoscala. Il secondo, proposto per la prima volta nel 1959 da Richard Feyman nel congresso dell’American Physical Society, consiste nel partire da strutture nanometriche per realizzare dei sistemi più grandi attraverso assembly o selfassembly. Attualmente, i principali strumenti, per caratterizzare e manipolare nano strutture, sono SEM (Microscopia a Scansione Elettronica) TEM (Microscopia a Trasmissione Elettronica), AFM (Atomic Force Microscopy) e STM (Microscopia a corrente di Tunnelling). Nanotubi, fullerene e recentemente carbon nanohorns (CNHs) e carbon onions (multishell fullerene, CNOs) sono considerati buoni candidati per applicazioni in differenti settori delle nanotecnologie. CNOs e CNHs sono due nuove forme allotropiche di carbonio, scoperte rispettivamente da Ugarte nel 1992 e da Iijima nel 1999, che hanno attratto l’attenzione di molti ricercatori. Negli ultimi tre anni, diversi studi sono stati riportati sui CNHs mentre i CNOs sono ancora largamente inesplorati. I pristine carbon nanohorns (p-CNHs) e CNOs (p-CNOs) non sono solubili nei comuni solventi organici ma, per studiare le loro potenziali applicazioni nel campo delle scienze dei materiali, è necessario migliorarne la solubilità. Il primo aspetto, preso in considerazione in questa tesi di dottorato, riguarda la funzionalizzazione e la caratterizzazione dei CNHs. A tale proposito, è stato sintetizzato un amminoacido impiegato nella reazione di ciclo addizione 1,3-dipolare. Reazioni di amidazione e di addizione nucleofila, inoltre, hanno portato alla sintesi dei due primi sistemi in cui CNHs fungono da elettron accettori e la porfirina da elettron donatori al fine di studiare il trasferimento elettronico tra la porfirina ed CNHs. Successivamente, sia i CNOs di 5 nm (N-CNOs) che di 20 nm di diametro (A-CNOs) sono stati presi in considerazione e paragonati. Dato che gli N-CNOs risultano più reattivi, sono stati utilizzati nella sintesi di nuovi sistemi in cui CNOs fungono da elettron accettori ed il ferrocene da elettron attrattore. Per la prima volta, sono state eseguite delle misure di fotofisica e di elettrochimica del derivato ottenuto. La tesi è divisa in 4 capitoli. Il primo riguarda una descrizione panoramica delle diverse forme allotropiche del carbonio, in paricolare nanotubi e fullereni. Tecniche come arco elettrico, ablazione con laser di grafite e la deposizione mediante vapore chimico sono descritte brevemente. Quindi tre diversi approcci per funzionalizzare le nanoparticelle di carbonio sono riportati in dettaglio. Nel secondo capitolo sono stati introdotti i CNHs, le loro proprietà ed applicazioni ed un confronto tra i nanotubi e CNHs. Infine tre differenti studi sono stati affrontati: · Funzonalizzazione mediante cicloaddizione 1,3-dipolare per migliorare la solubilità dei CNHs; · Funzionalizzazione dei CNHs attraverso addizione nucleofila e reazione con la porfirina; · Funzionalizzazione dei CNHs mediante amidazione e reazione con la porfirina. Il trasferimento elettronico tra porfirina e CNHs è stato discusso. Nel terzo capitolo sono stati introdotti e confrontate le proprietà dei diversi tipi di CNOs. Successivamente e’ stato descritto uno studio relativo alla: · Funzionalizzazione mediante cicloaddizione 1,3 dipolare e reazione con l’acido carbossilico del ferrocene. L’nterazione elettronica tra il ferrocene ed i CNOs è stata studiata. Tutti i dettagli sperimentali sono descritti nel quarto capitolo.“Functionalization and application of carbon nanohorns and carbon onions” Since the discovery of scanning probe microscope (SPM) in 1980 to that of fullerene, several Nobel Prizes have been awarded in Nanotechnology. Many companies are also currently working in this field such as IBM and Samsung. Government and corporations worldwide have invested over $ 4 billion into nanotechnology in the last year alone. What is exactly Nanotechnology? The word “Nanotechnology” is used to describe different types of research where the characteristic dimensions are in a nanometer range. Two main approaches are used to assemble materials at the nanoscale: “top-down” (from larger to smaller) and “bottom-up” (from smaller to larger). The first one consists in reducing the dimension of the structures until nano levels. The second one was proposed for the first time in 1959 by Richard Feyman in the annual congress of American Physical Society. It consists in using nanometric structure, such as a molecule, and to create a mechanism larger through a process of assembly or self-assembly. To characterize and manipulate nanostructures, sophisticated techniques are required. Presently the main instruments are SEM (Scanning Electron Microscopy), TEM (Transmission Electron Microscopy), AFM (Atomic Force Microscopy), STM (Scanning Tunnelling Microscopy). Carbon nanoparticles such as carbon nanotubes (CNTs), fullerenes and recently carbon nanohorns and carbon onions, are considered good candidates in different nanotechnological applications. Carbon onions (multishell fullerene, CNOs) and carbon nanohorns (CNHs) are new allotropes of carbon. Discovered respectively by Ugarte in 1992 and by Iijima in 1999, these carbon nanoparticles start to attract the attention of many researchers. In the last three years, several studies have been reported about CNHs while CNOs are still largely unexplored. Pristine carbon nanohorns (p-CNHs) and CNOs are not soluble in common solvents. In order to study their potential applications in the field of material science, improving their solubility was necessary. First I focused my attention on the functionalization and characterization of CNHs. An aminoacid was synthesized and used in 1,3-dipolar cycloaddition reaction. This functionalization leads to an increase of the solubility of CNHs in various organic solvents. Using other reactions, such as amidation or nucleophilic additions, two assemblies, in which CNHs are electron acceptors and porphyrins the electron donors, were synthesized and the electron transfer between the porphyrins and the CNH core was studied. Then, CNOs either of 5 nm or 20 nm of diameter were synthesized, respectively by annealing of nanodiamonds and by arc discharge. These two samples of CNOs present different properties and reactivity. As CNOs produced by annealing of nanodiamonds are more reactive, they were used to synthesize a new assembly, in which CNOs are the electron acceptors and ferrocene the electron donors. For the first time, electrochemical and photophysical measurements of CNOs were performed. The thesis is divided in four chapters. The first one provides an overview of carbon allotropes, in particular CNTs and fullerenes. Different techniques as arc discharge, laser ablation and chemical vapour deposition are briefly described. Finally three general approaches to functionalize carbon nanoparticles are reported in detail. In the second chapter CNHs are introduced. The properties and the applications are shown. A comparison between CNTs and CNHs is also given. Then three different studies are presented: · Functionalization by 1,3-dipolar cycloaddition to improve the solubility of CNHs; · Functionalization by nucleophilic addition and coupling with porphyrin; · Functionalization by amidation and coupling with porphyrin. The electron transfer between the porphyrin and CNH core is discussed. In the third chapter CNOs are introduced. Two different type of CNOs are described and compared in order to choose the more reactive nanoparticles. Then a study is reported: · Functionalization by 1,3 dipolar cycloaddition and coupling with ferrocene carboxylic acid. The interaction between the ferrocene moiety and the CNOs is discussed. All the experimental details are given in the fourth chapter.XX Ciclo197

Giant extracellular hemoglobin of Glossoscolex paulistus: an extraordinary supramolecular hemoprotein system

Giant extracellular hemoglobins are considered the summit of complexity in systems that carry oxygen, constituting an extraordinary model system to the study of hemoproteins. This class includes the hemoglobin of the annelid Glossoscolex paulistus that presents high cooperativity, great oligomeric and redox stabilities and ability of oligomeric reassociation. These properties have motivated evaluations about its utilization as prototype of artificial blood and biosensor. Kinetic studies involving autoxidation and detailed spectroscopic characterizations of its ferrous and ferric species have propitiated information about the structure-activity relationship of this macromolecule. The present review analyzes several biochemical issues, evaluating the state-of-art of this subject.CNP

Fotodecoloración de rojo de alizarina con películas delgadas de tetracarboxifenilporfirina de hierro (III) adsorbida sobre dióxido de silicio

El rojo de alizarina es un colorante de antraquinona soluble en agua que se usa ampliamente en la industria textil como agente de tinción y se considera uno de los contaminantes más recalcitrantes y duraderos. La reacción de Fenton puede usarse para destruir una amplia variedad de compuestos orgánicos: un ion ferroso reacciona con el peróxido de hidrógeno (H2O2) para formar un radical hidroxilo (HO•) que es un poderoso agente oxidante. La velocidad de esta reacción podría aumentarse cuando se expone a la luz UV-Vis, este método se conoce como proceso de Foto-Fenton y constituye una alternativa atractiva a los procesos de oxidación avanzada. En este trabajo se estudió la decoloración fotocatalítica del colorante rojo de alizarina mediante un proceso Foto-Fenton heterogéneo inducido por luz visible; para tal fin, se utilizaron películas delgadas de tetra(4-carboxifenil) porfirina de hierro (III) adsorbidas sobre dióxido de silicio. La caracterización del catalizador fue realizada por UV-Vis, reflectancia difusa e IR-FT. Los ensayos fueron realizados a tres (3) valores de pH 1.0, 3.0 y 5.0; finalmente, se utilizó el modelo cinético descrito por Langmuir-Hinshelwood para obtener los parámetros cinéticos del proceso de fotodecoloración. Los resultados mostraron que la mayor decoloración del rojo de alizarina se presentó a un pH de 1.0; además, el modelo de pseudo-primer orden aplicado permitió obtener la constante de velocidad (k) del proceso de decoloración encontrando que el mayor valor de k fue 1.1x10-2 min-1. Los radicales hidroxilo se detectaron por atrapamiento químico a través de fluorescencia indirecta del ácido 2-hidroxitereftálico. Los procesos de foto-Fenton basados en sistemas de catálisis heterogénea resuelven parte de estos problemas ambientales, proporcionando una fácil separación y recuperación del catalizador de las aguas residuales tratadas, en el que no es corrosivo y, además, es ecológico.Alizarin Red is a water soluble anthraquinone dye used extensively in the textile industry as a staining agent and is considered to be one of the most recalcitrant and durable pollutants. Fenton reaction can be used to destroy a wide variety of organic compounds: a ferrous ion reacts with hydrogen peroxide (H2O2) to form hydroxyl radical (HO•) which is a powerful oxidizing agent. The rate of this reaction could be increased when exposed o UV–vis light, this method is known as photo-assisted Fenton process and constitutes an attractive alternative of advance oxidation process. In this work, we studied the alizarin red dye photocatalytic discoloration through heterogeneous Photo-Fenton process induced by visible light; we used tetra (4-carboxyphenyl) porphyrin iron (III) adsorbed on silicon dioxide thin films. The characterization of the catalyst was carried out by UV-Vis, diffuse reflectance and IR-FT; The tests were carried out at three (3) pH values 1.0, 3.0 and 5.0; finally, the kinetic model described by Langmuir-Hinshelwood was used to obtain kinetic parameters for photo-discoloration process. The results showed that at pH = 1.0 highest alizarin red photo-discoloration percentage was reported; furthermore, after applied the pseudo-first order model, we obtained rate constants (k) for discoloration process that finds the highest k value was 1.1x10-2 min-1. The hydroxyl radicals were detected by chemical trapping through indirect fluorescence of the 2-hydroxyterephthalic acid. Photo-Fenton processes based on heterogeneous catalysis systems solve part of these environmental problems providing an easy separation and recovery of the catalyst from the treated wastewater, wherein it is noncorrosive, and, besides, it is environmentally friendly

Synthesis and emission properties of meso-substituted porphyrins

Discovering of various organic dyes including porphyrins have attracted considerable attention to mimic the energy and electron transfer process for the artificial photosynthetic model systems which can be applied in developing optoelectronic devices. The accessibility on tailoring porphyrin properties makes them a good candidate to, be developed as the red light emitting materials for these applications. Thus, symmetrical and unsymmetrical molecular models of porphyrins with appended fluorenyl components and extended π electrons conjugated system were synthesized towards increasing the efficiency of energy and electron transfer. In the photophysical studies, the emission spectra proposed the evidence of energy transfer of appended fluorenyl arms into the porphyrin macrocyclic whereas the extension of conjugating system in porphyrins exhibits lower absorption energy and intensified the red fluorescent properties