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1.
Eur J Prosthodont Restor Dent ; 32(1): 133-141, 2024 Feb 29.
Artículo en Inglés | MEDLINE | ID: mdl-38088266

RESUMEN

AIM: To evaluate the microtensile bond strength of self-etching adhesive systems in dentin treated with 2% chlorhexidine digluconate (CHX). MATERIALS AND METHODS: The occlusal surfaces of 20 human molars were removed and divided into eight groups: 1A, Clearfil SE adhesive (SE) with self-etching technique (TS); 1B, SE with TS and previous application of CHX; 2A, Scotchbond Universal (SBU) adhesive with TS; 2B, SBU adhesive with TS and previous application of CHX; 1C, SE with total-etching technique (TT); 1D, SE with TT and previous application of CHX; 2C, SBU with TT; 2D SBU with TT and previous application of CHX. Composite resin (5mm) was applied on the hybridized surface. Samples were subjected to microtensile test and evaluated on Scanning Electron Microscope (SEM) and with energy-dispersive X-ray (EDX). RESULTS: Low values of bond strength were observed in groups 1A (39,77±11,56) and 2A (40,84±12,49) comparing with 1B (22,86±5,18) and 2B (27,02±5,58). TS group presented adhesive type remover fracture while TT groups presented cohesive at the top of hybrid layer. EDX revealed the presence of CHX crystals for TS, which was not found in the TT. CONCLUSION: The previous application of chlorhexidine on dentin decreased the bond strength of adhesive systems on self-etching technique.


Asunto(s)
Clorhexidina , Recubrimiento Dental Adhesivo , Humanos , Clorhexidina/química , Cementos Dentales , Recubrimiento Dental Adhesivo/métodos , Cementos de Resina/química , Resinas Compuestas/química , Dentina , Resistencia a la Tracción , Recubrimientos Dentinarios/química , Ensayo de Materiales , Adhesivos
2.
Environ Monit Assess ; 193(4): 188, 2021 Mar 13.
Artículo en Inglés | MEDLINE | ID: mdl-33713187

RESUMEN

The present study examined the seasonal cycling of phosphorous (P) along the southwest coast of India (SWCI) based on two cruises during the southwest monsoon (SWM) and northeast monsoon (NEM) of 2018. During SWM, the entire SWCI experienced intense upwelling manifested by the incursion of cold, nutrient-rich, and hypoxic waters. During NEM, the region was transformed into a warm, well-oxygenated and nutrient-deplete environment. Dissolved inorganic phosphorus (DIP) was significantly high in the subsurface during SWM due to its release from sediments. The sediment P was high and showed an increasing trend towards the south, principally dependent on the sediment texture, organic carbon, and Fe concentrations. Bioavailable P, the sum of exchangeable (PEx) and reducible (PFe) fractions, was almost consistent (5-20%) over seasons, though PFe showed a marked reduction during SWM. Authigenic fraction (PAut) was the most dominant (46%), followed by detrital (PDet 41%) and residual (PRes 8%) fractions. Principal component analysis (PCA) of geochemical parameters for SWM was indicative of the high dissolution of Fe (oxy)hydroxides under hypoxia releasing P and its complexation with organic matter and Fe. PCA results for the NEM were different, as it indicated increased preservation of P-associated organic matter and Fe, alternately favouring the formation of PAut in sediments. The study's significance is the observation that the bottom water oxygen concentration can significantly influence sedimentary P cycling in tropical coastal upwelling zones.


Asunto(s)
Monitoreo del Ambiente , Fósforo , Carbono , Sedimentos Geológicos , India , Fósforo/análisis , Estaciones del Año
3.
Mar Pollut Bull ; 164: 112042, 2021 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-33524831

RESUMEN

This study investigates the influence of upwelling induced seasonal hypoxia in the sediment-water interface on the distribution, bioavailability and geochemical partitioning of selected trace metals in surficial sediments along the southwest coast of India based on two successive cruises. The first cruise was during the southwest monsoon (SWM) season when coastal waters exhibited intermittent bottom hypoxia due to upwelling. The second cruise during the northeast monsoon (NEM) season was characterised by a uniformly warm and well-oxygenated water column in the study region. The results showed that grain size, organic carbon and Fe are the major factors influencing the distribution of trace metals in the surface sediments. Based on the geochemical indices (contamination factor, enrichment factor and geo-accumulation factor), the study region appears to be moderately contaminated by Ni, Cr, and Pb. Based on the ecological risk assessment criteria, the enrichment of Pb, Cr and Ni may cause adverse effects on the benthic organisms. The fractionation studies demonstrated that the major pathway of metal deposition in the sediment is lithogenic. The data also showed that labile and organic fractions are the second dominant forms, while other fractions (exchangeable and carbonate) are insignificant. The consistency in the reactive Fe concentrations during SWM and NEM could be due to the absence of Fe dissolution in sediments under mild reducing condition (intermittent hypoxia). In addition to the above, an enrichment of organic matter also leads to increased deposition of trace metals in sediments. Conversely, the secondary phase enrichment factor and risk assessment code calculated based on the metal fractionation data indicated low risk and contamination along the southwest coast of India except for Zn that showed moderate contamination in some transects. The study provides the need for regular geochemical assessment to control metal pollution in the coastal environment, which is a major resource of the fishery.


Asunto(s)
Metales Pesados , Contaminantes Químicos del Agua , Disponibilidad Biológica , Monitoreo del Ambiente , Sedimentos Geológicos , India , Metales Pesados/análisis , Contaminantes Químicos del Agua/análisis
4.
Acta Reumatol Port ; 43(1): 10-31, 2018.
Artículo en Inglés | MEDLINE | ID: mdl-29602163

RESUMEN

BACKGROUND: Advances in osteoporosis (OP)case definition, treatment options, optimal therapy duration and pharmacoeconomic evidence in the national context motivated the Portuguese Society of Rheumatology (SPR) to update the Portuguese recommendations for the diagnosis and management of osteoporosis published in 2007. METHODS: SPR bone diseases' working group organized meetings involving 55 participants (rheumatologists, rheumatology fellows and one OP specialist nurse) to debate and develop the document. First, the working group selected 11 pertinent clinical questions for the diagnosis and management of osteoporosis in standard clinical practice. Then, each question was investigated through literature review and draft recommendations were built through consensus. When insufficient evidence was available, recommendations were based on experts' opinion and on good clinical practice. At two national meetings, the recommendations were discussed and updated. A draft of the recommendations full text was submitted to critical review among the working group and suggestions were incorporated. A final version was circulated among all Portuguese rheumatologists before publication and the level of agreement was anonymously assessed using an online survey. RESULTS: The 2018 SPR recommendations provide comprehensive guidance on osteoporosis prevention, diagnosis, fracture risk assessment, pharmacological treatment initiation, therapy options and duration of treatment, based on the best available evidence. They attained desirable agreement among Portuguese rheumatologists. As more evidence becomes available, periodic revisions will be performed. Target audience and patient population: The target audience for these guidelines includes all clinicians. The target patient population includes adult Portuguese people. Intended use: These recommendations provide general guidance for typical cases. They may not be appropriate in all situations - clinicians are encouraged to consider this information together with updated evidence and their best clinical judgment in individual cases.


Asunto(s)
Osteoporosis/diagnóstico , Osteoporosis/terapia , Humanos , Osteoporosis/prevención & control
6.
Acta Reumatol Port ; 41(3): 256-259, 2016.
Artículo en Inglés | MEDLINE | ID: mdl-27155318

RESUMEN

Accounting for 2.2-4.7% of all tuberculosis cases in Europe and USA and around 10-15% of extra-pulmonary tuberculosis cases, osteoarticular tuberculosis tends to be chronic, slowly progressive and destructive. We report the case of an 81-year-old male with 3 weeks of progressively worsening pain, swelling and limited range of motion of the left knee. A knee arthroscopy was performed for synovial biopsy at our department revealing diffuse synovitis with scarce villi formation. The positive polymerase chain reaction assay for Mycobacterium tuberculosis in the synovial tissue allowed the establishment of the diagnosis and synovium histology showed caseating granulomas. A lengthy delay between first symptoms of osteoarticular tuberculosis and the beginning of treatment has been reported. A high index of suspicion, synovial membrane biopsy and appropriate microbiologic testing are fundamental to avoid a delay in diagnosis.


Asunto(s)
Artritis Infecciosa/patología , Artroscopía , Membrana Sinovial/patología , Tuberculosis Osteoarticular/patología , Anciano de 80 o más Años , Artritis Infecciosa/microbiología , Biopsia , Humanos , Masculino , Membrana Sinovial/microbiología , Tuberculosis Osteoarticular/microbiología
8.
J Colloid Interface Sci ; 464: 117-25, 2016 Feb 15.
Artículo en Inglés | MEDLINE | ID: mdl-26609931

RESUMEN

A molecule with a π conjugated backbone built from aromatic thiophene and dialkoxyphenylene units and substituted imidazolium groups (TPO) is designed to obtain ultra-stable single walled carbon nanotube (SWCNT) dispersion in aqueous medium. The proposed mechanism of non-covalent interaction is accompanied by individualization of SWCNT and comprises of dominant nondisruptive π-π and cation-π interaction between them and the TPO conjugated oligomer. The individualization of SWCNT and dispersibility and stability of the ultra-stable suspensions were estimated using high resolution transmission electron microscopy, UV-Visible-NIR absorption spectroscopy, Raman spectroscopy, photoluminescence and zeta potential measurement. Nuclear magnetic resonance data provides direct evidence toward possible cation-π interaction.

9.
Psychol Med ; 46(5): 1079-90, 2016 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-26708017

RESUMEN

BACKGROUND: Anxiety and depression are common following traumatic brain injury (TBI), often co-occurring. This study evaluated the efficacy of a 9-week cognitive behavioral therapy (CBT) program in reducing anxiety and depression and whether a three-session motivational interviewing (MI) preparatory intervention increased treatment response. METHOD: A randomized parallel three-group design was employed. Following diagnosis of anxiety and/or depression using the Structured Clinical Interview for DSM-IV, 75 participants with mild-severe TBI (mean age 42.2 years, mean post-traumatic amnesia 22 days) were randomly assigned to an Adapted CBT group: (1) MI + CBT (n = 26), or (2) non-directive counseling (NDC) + CBT (n = 26); or a (3) waitlist control (WC, n = 23) group. Groups did not differ in baseline demographics, injury severity, anxiety or depression. MI and CBT interventions were guided by manuals adapted for individuals with TBI. Three CBT booster sessions were provided at week 21 to intervention groups. RESULTS: Using intention-to-treat analyses, random-effects regressions controlling for baseline scores revealed that Adapted CBT groups (MI + CBT and NDC + CBT) showed significantly greater reduction in anxiety on the Hospital Anxiety and Depression Scale [95% confidence interval (CI) -2.07 to -0.06] and depression on the Depression Anxiety and Stress Scale (95% CI -5.61 to -0.12) (primary outcomes), and greater gains in psychosocial functioning on Sydney Psychosocial Reintegration Scale (95% CI 0.04-3.69) (secondary outcome) over 30 weeks post-baseline relative to WC. The group receiving MI + CBT did not show greater gains than the group receiving NDC + CBT. CONCLUSIONS: Findings suggest that modified CBT with booster sessions over extended periods may alleviate anxiety and depression following TBI.


Asunto(s)
Trastornos de Ansiedad/terapia , Lesiones Traumáticas del Encéfalo/psicología , Terapia Cognitivo-Conductual/métodos , Trastorno Depresivo/terapia , Entrevista Motivacional/métodos , Adulto , Ansiedad , Trastornos de Ansiedad/diagnóstico , Australia , Depresión , Trastorno Depresivo/diagnóstico , Manual Diagnóstico y Estadístico de los Trastornos Mentales , Femenino , Humanos , Masculino , Persona de Mediana Edad , Análisis de Regresión , Índice de Severidad de la Enfermedad , Resultado del Tratamiento
10.
Braz J Biol ; 75(2 Suppl): 85-90, 2015 May.
Artículo en Inglés | MEDLINE | ID: mdl-26270219

RESUMEN

The activated carbon filter is used in residences as another step in the treatment of drinking water, based on a physical-chemical process to absorb pollutants that are not removed in conventional treatment. Endocrine disruptors (EDCs) are exogenous substances or mixtures of substances that acts on the endocrine system similarly to the endogenously produced hormones, triggering malfunctions and harmful changes to human and animal health. The objective of the present work was to study EDCs through semi-quantitative analysis of residential water filters collected in the region of Rio dos Sinos basin, focusing on two specific classes: hormones and phenols. The solid phase extraction principle was used for the extraction of compounds and gas chromatography coupled with mass spectrometry for the separation and characterization of EDCs. Four samples of residential filters collected from public water distribution and artesian wells, from the cities of Novo Hamburgo and São Leopoldo were analysed. Using the developed methodology, it was possible to detect and comparatively quantify selected EDCs in all studied samples, which indicates the presence of these contaminants in drinking water from different sources.


Asunto(s)
Agua Potable/análisis , Disruptores Endocrinos/análisis , Ríos/química , Contaminantes Químicos del Agua/análisis , Calidad del Agua , Brasil , Monitoreo del Ambiente , Filtración , Cromatografía de Gases y Espectrometría de Masas , Hormonas/análisis , Fenoles/análisis , Extracción en Fase Sólida
11.
Parasitology ; 142(11): 1398-403, 2015 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-26194017

RESUMEN

Dientamoeba fragilis is an inhabitant of human gastrointestinal tract with a worldwide distribution. The first description considered this protozoan a rare and harmless commensal, since then it has struggled to gain recognition as a pathogen. Commercial multiplex real-time PCR was used to detect D. fragilis in fecal samples from hospitalized children (⩽18 years) with acute gastrointestinal disease, admitted to two hospitals of Lisbon area, with different demographic characteristics. A total of 176 children were studied, 103 (58·5%) male, 144 (81·8%) children between 0 and 5 years and 32 (18·2%) above 6 years old. The overall protozoa frequency considering the four tested microorganisms were 8·5% (15/176), and the most frequently found protozoan was D. fragilis, 6·3% (11/176). Dientamoeba fragilis frequency was higher among older children (21·9%), than younger children (2·8%), and greater in boys (6·8%) than in girls (5·5%). All positive children presented with diarrhoea associated with vomiting, fever and abdominal pain. Infection was associated with the age of children (P < 0·001), school attendance (P = 0·002) and consumption of certain foods (P = 0·014), e.g. cakes with crème and ham. The frequency of diantamoebiasis found in a cohort of hospitalized Portuguese children, with acute gastrointestinal disease, could be considered a very high value when compared with the protozoan frequency normally associated with this pathology.


Asunto(s)
Dientamoeba/aislamiento & purificación , Dientamebiasis/epidemiología , Gastroenteritis/epidemiología , Dolor Abdominal , Enfermedad Aguda , Adolescente , Animales , Niño , Preescolar , Estudios de Cohortes , Diarrea , Dientamoeba/genética , Dientamebiasis/parasitología , Heces/parasitología , Femenino , Gastroenteritis/parasitología , Tracto Gastrointestinal/parasitología , Humanos , Lactante , Masculino , Reacción en Cadena de la Polimerasa Multiplex , Portugal/epidemiología
12.
Oral Health Dent Manag ; 13(3): 728-30, 2014 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-25284547

RESUMEN

BACKGROUND: Kohlschütter-Tönz syndrome is a rare neurodegenerative disorder presenting with intractable seizures, developmental regression, and characteristic hypoplastic dental enamel indicative of amelogenesis imperfecta. Recently, mutations in ROGDI were identified in part of Kohlschütter-Tönz syndrome cases, but the siblings reported here do not have a mutation in the ROGDI gene, showing that there is genetic heterogeneity in Kohlschütter-Tönz syndrome. AIM: Report two siblings that have Kohlschütter-Tönz syndrome. CONCLUSION: Early onset of seizures and lack of the ability to walk without support may be signs of non-ROGDI mutations in Kohlschütter-Tönz syndrome patients.

13.
Genet Mol Res ; 10(4): 3937-41, 2011 Oct 25.
Artículo en Inglés | MEDLINE | ID: mdl-22033907

RESUMEN

The testis-specific protein Y-encoded gene (TSPY) is a Y-specific gene present in variable copy number in many mammalian species, including cattle. We tested the applicability of the TSPY gene as a Y-specific marker to predict preimplantation embryo sex in Nelore (Bos indicus) cattle. Two blastomeres were removed from each embryo. A total of 36 single blastomeres and the remaining cells of their 18 matched in vitro conceived embryos were screened for TSPY amplification by nested-PCR. The results obtained from a single blastomere and the remaining cells of the same embryo were concordant in all cases. All blastomeres (16/16) from eight embryos produced with sexed sperm (specific for production of male embryos) were TSPY-positive. We conclude that TSPY is a good male-specific marker, the usefulness of which is probably enhanced by the high copy number. Other methods that are less time-consuming, such as real-time PCR, could be improved with the use of the TSPY gene sequences to generate primers and/or probes. This is the first report to demonstrate the applicability of the TSPY gene for sexing single cells in cattle.


Asunto(s)
Blastómeros/metabolismo , Proteínas de Ciclo Celular/genética , Reacción en Cadena de la Polimerasa/métodos , Análisis para Determinación del Sexo/métodos , Animales , Bovinos , Electroforesis en Gel de Poliacrilamida , Embrión de Mamíferos/metabolismo , Femenino , Masculino
14.
Clin Microbiol Infect ; 17(9): 1397-402, 2011 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-20731680

RESUMEN

Multidrug-resistance and extensive drug-resistance pose a serious threat to tuberculosis management in Portugal. The country has high TB incidence rates in comparison with other European Union countries, with the Lisbon Health Region being one of the most affected. In the present study we have analysed a convenience sample of 3025 Mycobacterium tuberculosis clinical isolates, recovered over a 6-year period (2001-2006) in the Lisbon Health Region, regarding drug-resistance both to first-line and second-line drugs. Moreover, 100 of these isolates were also genotyped by 12-loci Mycobacterial Interspersed Repetitive Unit - Variable Number of Tandem Repeats (MIRU-VNTR) analysis. We have compared each year and observed the existence of 22 different resistance profiles, with MDR-TB rates ranging between 9.9% and 15.2% and XDR-TB rates, relative to the number of MDR-TB isolates, between 44.3% and 66.1% (excluding 1 year here considered as an outlier). A steady increase in the fraction of MDR-TB isolates resistant to all first-line drugs was also noticed. The genotyping analysis of MDR-TB isolates revealed six clusters, of which three (Lisboa3, Lisboa4 and Q1) were related to XDR-TB. Our results show that active transmission of MDR- and XDR-TB is taking place and that the high prevalence of observed XDR-TB is due to the continued transmission of particular genetic clusters. Enforcement of the implementation of genotyping in diagnostic routines would lead to early detection of resistant cases.


Asunto(s)
Tuberculosis Extensivamente Resistente a Drogas/epidemiología , Mycobacterium tuberculosis/efectos de los fármacos , Tuberculosis Resistente a Múltiples Medicamentos/epidemiología , Farmacorresistencia Bacteriana Múltiple , Tuberculosis Extensivamente Resistente a Drogas/microbiología , Genes Bacterianos , Genotipo , Humanos , Secuencias Repetitivas Esparcidas , Pruebas de Sensibilidad Microbiana , Repeticiones de Minisatélite , Mycobacterium tuberculosis/genética , Mycobacterium tuberculosis/aislamiento & purificación , Portugal/epidemiología , Prevalencia , Estudios Retrospectivos , Tuberculosis Resistente a Múltiples Medicamentos/microbiología
15.
J Phys Condens Matter ; 22(33): 334222, 2010 Aug 25.
Artículo en Inglés | MEDLINE | ID: mdl-21386512

RESUMEN

Surface composition plays an important role in carbon nanotube dispersibility in different environments. Indeed, it determines the choice of dispersion medium. In this paper the effect of oxidation on the dispersion of HiPCO single-walled carbon nanotubes (SWNTs) in N-methyl-pyrrolidinone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), N-dodecyl-pyrrolidinone (N12P) and cyclohexyl-pyrrolidinone (CHP) was systematically studied. During the oxidation process, similar amounts of carboxylic acid and phenolic groups were introduced to mostly already existing defects. For each solvent the dispersion limits and the absorption coefficients were estimated by optical absorption analysis over a range of SWNT concentrations. The presence of acid oxygenated groups increased SWNT dispersibility in NMP, DMF and DMA, but decreased in N12P and CHP. The absorption coefficients, however, decreased for all solvents after oxidation, reflecting the weakening of the effective transition dipole of the π-π transition with even limited extension functionalization and solvent interaction. The analysis of the results in terms of Hansen and Flory-Huggins solubility parameters evidenced the influence of dipolar interactions and hydrogen bonding on the dispersibility of oxidized SWNTs.


Asunto(s)
Amidas/química , Coloides/química , Nanotubos de Carbono/química , Nanotubos de Carbono/ultraestructura , Oxígeno/química , Solventes/química , Sustancias Macromoleculares/química , Ensayo de Materiales , Conformación Molecular , Tamaño de la Partícula , Propiedades de Superficie
16.
Acta Psychiatr Scand ; 120(4): 265-73, 2009 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-19486330

RESUMEN

OBJECTIVE: To identify possible differences in the mean midsagittal corpus callosum (CC) total and subdivision areas in treatment-resistant schizophrenia and depression (TRS and TRD) patients. METHOD: Areas of the total CC and its five equidistant subregions (from CC1 to CC5) obtained by parallel grid partitioning schemes were manually segmented from brain MRI of 42 TRS, 45 TRD patients and 30 healthy controls. The intracranial volume (ICV) normalized areas were calculated and compared between groups. RESULTS: When compared with controls, patients with TRS had reduced ICV and a larger CC5, and TRD patients had a smaller CC4 while no significant difference in CC total area in patients with TRS or TRD was found. Multiple individual segments and total CC areas were significantly larger in TRS than TRD patients after normalization. CONCLUSION: Patients with TRS and TRD have different CC morphological characteristics, and therefore there may be aberrant interhemispheric connectivity in schizophrenia and major depressive disorder patients.


Asunto(s)
Agenesia del Cuerpo Calloso , Cuerpo Calloso/fisiopatología , Trastorno Depresivo Mayor/tratamiento farmacológico , Trastorno Depresivo Mayor/fisiopatología , Resistencia a Medicamentos , Esquizofrenia/tratamiento farmacológico , Esquizofrenia/fisiopatología , Adolescente , Adulto , Antipsicóticos/clasificación , Antipsicóticos/uso terapéutico , Femenino , Humanos , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Índice de Severidad de la Enfermedad , Adulto Joven
18.
Epidemiol Infect ; 137(2): 161-5, 2009 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-18667108

RESUMEN

Neisseria meningitidis capsular switching has been reported in several countries. In order to establish the genetic relationship within group B and C strains expressing subtypes 2a or 2b, and to evaluate whether C to B capsular switching occurred in Portugal, 64 meningococci (56 serogroup C and 8 serogroup B) isolated from invasive meningococcal disease were typed using molecular methods. The studied phenotypes, 2b:P1.5,2 and 2a:P1.5-1,10-8, were the most frequent among serogroup C, but were uncommon among serogroup B strains. The multi-locus sequence typing (MLST) allelic profile and the pulsed-field gel electrophoresis (PFGE) fingerprints showed that seven serogroup B strains were genotypically identical to C strains, suggesting that capsular switching occurred. Active laboratory surveillance to find evidence of capsule switching is a now priority as MenC was introduced in the Portuguese vaccination schedule in January 2006.


Asunto(s)
Variación Antigénica , Cápsulas Bacterianas/genética , Infecciones Meningocócicas/epidemiología , Infecciones Meningocócicas/microbiología , Neisseria meningitidis/genética , Neisseria meningitidis/aislamiento & purificación , Técnicas de Tipificación Bacteriana , Análisis por Conglomerados , Dermatoglifia del ADN , ADN Bacteriano/genética , Electroforesis en Gel de Campo Pulsado , Genotipo , Humanos , Neisseria meningitidis/clasificación , Portugal/epidemiología , Análisis de Secuencia de ADN , Serotipificación
20.
J Nanosci Nanotechnol ; 7(10): 3421-30, 2007 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-18330151

RESUMEN

A classical protocol widely used in organic chemistry of aromatic and polyaromatic molecules has been successfully applied in this work for the decarboxylation of oxidized single-wall carbon nanotube (SWNT) to rend C-H SWNT derivatives. SWNT produced by arc discharge method have been oxidized during a purification process using strongly oxidant agents, such as hydrogen peroxide and nitric acid. The decarboxylation of oxidized SWNT has been conduced with copper(I) oxide in a 50:50 solution of N-methylpyrrolidone and quinoline. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and acid-base potentiometric titration analyses were carried out to characterize quali and quantitatively the changes in the chemical environment on the SWNT surface in each step of the purification and the decarboxylation process. Those techniques showed the appearance of mainly carboxylic and phenolic groups after the purification process and the disappearance of the carboxylic groups after the decarboxylation reaction. Fourier transform infrared spectroscopy analysis indicated also the formation of aliphatic and aromatic C-H groups. X-ray photoelectron spectroscopy and potentiometric titration results determined an efficiency higher than 90% for our decarboxylation procedure. The purity and structural quality of the SWNT sample used in the decarboxylation process were evaluated by thermogravimetry and Raman spectroscopy. Thermogravimetric analysis identified a purified sample with approximately 80 wt% of SWNT, in fractions distributed in highly structured SWNTs (25 wt%), with distribution in composition, length and structural quality (35 wt%) and with very defective and short tubes (25 wt%). The damages on the purified SWNT walls were characterized by the Raman scattering analysis.


Asunto(s)
Cristalización/métodos , Nanotecnología/métodos , Nanotubos de Carbono/química , Nanotubos de Carbono/ultraestructura , Oxígeno/química , Sustancias Macromoleculares/química , Ensayo de Materiales , Conformación Molecular , Oxidación-Reducción , Tamaño de la Partícula , Propiedades de Superficie
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