Synthesis and optical properties of SWCNTs doped by Boron and Nitrogen Heteroatoms

Diese Masterarbeit beschäftigt sich hauptsächlich mit der Studie von single walled carbon nanotubes (SWCNTs) sowie mit der Änderung deren elektronischer Eigenschaften, hervorgerufen durch deren Dotierung mit N beziehungsweise B. Hinsichtlich der Synthese von Nanoröhren existiert bereits eine breite Menge an Literatur, welche sich in erster Linie mit multi-walled nanotubes Strukturen beschäftigt. Obwohl die meisten jener Studien auch von der Verwendung von single-walled nanotubes sprechen, haben die experimentellen Methoden um solche Strukturen zu erhalten erst kürzlich die bisherigen Schwierigkeiten bei der Synthese von dotierten single-walled carbon nanotubes überwunden. Aus diesem Grund wird die umfassende Charakterisierung gerade dieser relativ neuen Materialien dringend benötigt. In der vorliegenden Arbeit wurden unterschiedliche Arten von SWCNTs, welche mittels diverser spektroskopischer Techniken mit Stickstoff dotiert wurden, untersucht. In situ wurde die Dotierung während des Wachstums in N-dotierten SWCNTs studiert, wobei in diesem Fall hauptsächlich die chemical vapor deposition auf zwei verschiedene Arten als Synthesemethode angewendet wurde. Des Weiteren wurde die SWCNTs-Dotierung mit N auch nach deren Synthese an einem pristine laser ablation SWCNTs buckypaper untersucht, wobei N+2 Ionen implantiert wurden. Im Zuge dieses Projektes wurde ebenso versucht die kontrollierte Synthese B-dotierter single-walled nanotubes mittels der high vacuum chemical vapor deposition-Methode zu optimieren. Die optischen und elektronischen Eigenschaften dieser Nanoröhren wurden einerseits durch spektroskopische Techniken (optische Absorption, Multi-Frequenz Raman-spektroskopie, Photoluminiszenz) als auch mittels zusätzlicher, dazu komplementärer Studien, durchgeführt im Zuge der Zusammenarbeit mit diversen anderen Gruppen (XPS, TEM, EELS), auf welche in späteren Textpassagen noch weiter eingegangen wird, analysiert.This master thesis is mainly focused on the study of single walled-carbon nanotubes (SWCNTs) and the changes of their electronic properties upon doping with N and B. The literature related to the topic of synthesis is relatively vast regarding multi-walled nanotube structures. However, although most of the theoretical studies involve the use of single walled material, the experimental methods to obtain such structures have only recently overcome the difficulties to synthesize doped single-walled carbon nanotubes. For this reason, an extensive characterization of these relatively new materials is still urgently required. In this work, different kinds of SWCNTs doped with nitrogen via different spectroscopic techniques have been studied. In situ doping during growth was studied in N-doped SWCNTs, in which case the main synthesis method was chemical vapor deposition in two different types. Additionally, post synthesis doping with N on SWCNTs was studied on a buckypaper of pristine laser ablation SWCNTs where N+2 ion implantation was applied. During this project, the controlled synthesis of singlewalled nanotubes doped with B was optimized via the high vacuum chemical vapor deposition method. The optical and electronic properties of these nanotubes were examined also by the spectroscopic techniques (optical absorption, multi-frequency Raman spectroscopy, photoluminescence), and complemented with additional studies done via collaborations (XPS, TEM, EELS), which will be mentioned along the text where it applies

Disentangling Vacancy Oxidation on Metallicity-Sorted Carbon Nanotubes

Pristine single-walled carbon nanotubes (SWCNTs) are rather inert to O$_2$ and N$_2$, which for low doses chemisorb only on defect sites or vacancies of the SWCNTs at the ppm level. However, very low doping has a major effect on the electronic properties and conductivity of the SWCNTs. Already at low O$_2$ doses (80 L), the X-ray photoelectron spectroscopy (XPS) O 1s signal becomes saturated, indicating nearly all the SWCNT's vacancies have been oxidized. As a result, probing vacancy oxidation on SWCNTs via XPS yields spectra with rather low signal-to-noise ratios, even for metallicity-sorted SWCNTs. We show that, even under these conditions, the first principles density functional theory calculated Kohn-Sham O 1s binding energies may be used to assign the XPS O 1s spectra for oxidized vacancies on SWCNTs into its individual components. This allows one to determine the specific functional groups or bonding environments measured. We find the XPS O 1s signal is mostly due to three O-containing functional groups on SWCNT vacancies: epoxy (C$_2$$>$O), carbonyl (C$_2$$>$C$=$O), and ketene (C$=$C$=$O), as ordered by abundance. Upon oxidation of nearly all the SWCNT's vacancies, the central peak's intensity for the metallic SWCNT sample is 60\% greater than for the semiconducting SWCNT sample. This suggests a greater abundance of O-containing defect structures on the metallic SWCNT sample. For both metallic and semiconducting SWCNTs, we find O$_2$ does not contribute to the measured XPS O~1s spectra

Revealing the adsorption mechanisms of nitroxides on ultrapure, metallicity-sorted carbon nanotubes

Terms of Use CC-BY.-- et al.Carbon nanotubes are a natural choice as gas sensor components given their high surface to volume ratio, electronic properties, and capability to mediate chemical reactions. However, a realistic assessment of the interaction of the tube wall and the adsorption processes during gas phase reactions has always been elusive. Making use of ultraclean single-walled carbon nanotubes, we have followed the adsorption kinetics of NO2 and found a physisorption mechanism. Additionally, the adsorption reaction directly depends on the metallic character of the samples. Franck–Condon satellites, hitherto undetected in nanotube–NOx systems, were resolved in the N 1s X-ray absorption signal, revealing a weak chemisorption, which is intrinsically related to NO dimer molecules. This has allowed us to identify that an additional signal observed in the higher binding energy region of the core level C 1s photoemission signal is due to the C═O species of ketene groups formed as reaction byproducts . This has been supported by density functional theory calculations. These results pave the way toward the optimization of nanotube-based sensors with tailored sensitivity and selectivity to different species at room temperature.This work was supported by the Austrian Science Fund through Project FWF P21333-N20 and by the EU Proposal No. 20105285 for ELETTRA. P.A. was supported by a Marie Curie Intra European Fellowship within the Seventh European Community Framework Programme. D.J.M. acknowledges funding through the Spanish “Juan de la Cierva” program (JCI-2010-08156). We acknowledge funding by the European Research Council Advanced Grant DYNamo (ERC-2010-AdG-Proposal No. 267374), Spanish Grants (FIS2010-21282-C02-01 and PIB2010US-00652), “Grupos Consolidados UPV/EHU del Gobierno Vasco” (IT-319-07 and IT-578-13), and the European Commission project CRONOS (280879-2 CRONOS CP-FP7) and POCAONTAS (FP7-PEOPLE-2012-ITN). A.G. thanks the COST ACTION EuNetAir (No. TD1105).Peer reviewe

Analysis of protective factors in the approach of child abuse from the clinical perspective

El objetivo de este trabajo fue explorar desde una mirada clínica la presencia de los factores protectores necesarios para otorgar el alta en un proceso terapéutico de casos de maltrato infantil confirmados, según la opinión de los profesionales especialistas en su abordaje. Desde la perspectiva cualitativa, se utilizó una muestra no probabilística ocasional constituida por 51 médicos, psicólogos, trabajadores sociales y otras disciplinas afines, especialistas en el abordaje de casos de maltrato infantil. Como instrumentos, se implementaron entrevistas y grupos de enfoque. Los resultados señalan la necesidad de la evaluación y fortalecimiento de las funciones parentales. Además, se rescataron notablemente los recursos y potencialidades propios del niño y de la familia, los recursos institucionales y los del equipo de salud. Esta propuesta se orienta a integrar la investigación con la reflexión acerca de las prácticas en el ámbito del maltrato infantil,con el fin de mejorar las intervenciones clínicas.The aim of this study was to explore from a clinical gaze the presence of protective factors necessary to grant discharge of confirmed cases of child abuse after a therapeutic process, in the opinion of the specialists. From the qualitative perspective, it was used a non-probabilistic sample consisting of 51 casual professionals (doctors, psychologists, social workers, and related disciplines), specialists all of them in cases of child abuse. As instruments, interviews and focal groups were implemented. The results indicated the need for evaluation and strengthening of the parental roles. In addition, there were rescued significantly the resources and potentials of the child and the family, as well the institutional and the health team ones. This proposal aims to integrate research with reflection about the practices in the field of child abuse, in order to improve clinical interventions.Fil: Morelato, Gabriela Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Ciencias Humanas, Sociales y Ambientales; Argentina. Universidad del Aconcagua. Facultad de Psicología; ArgentinaFil: Giménez, Silvina. Universidad del Aconcagua. Facultad de Psicología; ArgentinaFil: Vitaliti, Jose Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Ciencias Humanas, Sociales y Ambientales; Argentina. Universidad del Aconcagua. Facultad de Psicología; ArgentinaFil: Casari, Leandro Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Ciencias Humanas, Sociales y Ambientales; Argentina. Universidad del Aconcagua. Facultad de Psicología; ArgentinaFil: Ruiz Soria, Rosa Georgina. Universidad del Aconcagua. Facultad de Psicología; Argentin

Revealing the Adsorption Mechanisms of Nitroxides on Ultrapure, Metallicity-Sorted Carbon Nanotubes

Carbon nanotubes are a natural choice as gas sensor components given their high surface to volume ratio, electronic properties, and capability to mediate chemical reactions. However, a realistic assessment of the interaction of the tube wall and the adsorption processes during gas phase reactions has always been elusive. Making use of ultraclean single-walled carbon nanotubes, we have followed the adsorption kinetics of NO₂ and found a physisorption mechanism. Additionally, the adsorption reaction directly depends on the metallic character of the samples. Franck–Condon satellites, hitherto undetected in nanotube–NO_<i>x</i> systems, were resolved in the N 1<i>s</i> X-ray absorption signal, revealing a weak chemisorption, which is intrinsically related to NO dimer molecules. This has allowed us to identify that an additional signal observed in the higher binding energy region of the core level C 1<i>s</i> photoemission signal is due to the CO species of ketene groups formed as reaction byproducts . This has been supported by density functional theory calculations. These results pave the way toward the optimization of nanotube-based sensors with tailored sensitivity and selectivity to different species at room temperature

Hypoxia Induces Alterations in the Circadian Rhythm in Patients with Chronic Respiratory Diseases

The function of the circadian cycle is to determine the natural 24 h biological rhythm, which includes physiological, metabolic, and hormonal changes that occur daily in the body. This cycle is controlled by an internal biological clock that is present in the body’s tissues and helps regulate various processes such as sleeping, eating, and others. Interestingly, animal models have provided enough evidence to assume that the alteration in the circadian system leads to the appearance of numerous diseases. Alterations in breathing patterns in lung diseases can modify oxygenation and the circadian cycles; however, the response mechanisms to hypoxia and their relationship with the clock genes are not fully understood. Hypoxia is a condition in which the lack of adequate oxygenation promotes adaptation mechanisms and is related to several genes that regulate the circadian cycles, the latter because hypoxia alters the production of melatonin and brain physiology. Additionally, the lack of oxygen alters the expression of clock genes, leading to an alteration in the regularity and precision of the circadian cycle. In this sense, hypoxia is a hallmark of a wide variety of lung diseases. In the present work, we intended to review the functional repercussions of hypoxia in the presence of asthma, chronic obstructive sleep apnea, lung cancer, idiopathic pulmonary fibrosis, obstructive sleep apnea, influenza, and COVID-19 and its repercussions on the circadian cycles

On the bonding environment of phosphorus in purified doped single-walled carbon nanotubes

In this work, phosphorous-doped single-walled carbon nanotubes have been synthesized by the thermal decomposition of trimethylphosphine using a high-vacuum chemical vapor deposition method. Furthermore, a modified density-gradient-ultracentrifugation process has been applied to carefully purify our doped material. The combined use of Raman and X-ray photoelectron spectroscopy allowed us to provide the first insight into the bonding environment of P incorporated into the carbon lattice, avoiding competing signals arising from synthesis byproducts. This study represents the first step toward the identification of the bonding configuration of P atoms when direct substitution takes place.Copyright © 2014 Elsevier Ltd