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1.
Langmuir ; 39(14): 5002-5011, 2023 Apr 11.
Article in English | MEDLINE | ID: mdl-36989403

ABSTRACT

We report on a new iron (iii)-cyamelurate-based coordination polymer. The new material based on a heptazine derivative was prepared in aqueous medium and characterized by a variety of techniques including TGA, FTIR, XRD, HRTEM, and STEM. Due to the high structural stability of the complex in aqueous media, its heterogeneous Fenton-like catalytic activity was evaluated using a model molecule. The results obtained showed a high catalytic activity in both in basic and acid media. The pseudo-first-order rate constants normalized by iron(III) concentrations was approximately 1000 times higher than the result obtained for traditional heterogeneous catalysts based on iron(III) oxyhydroxides. The best observed catalytic activities were attributed to the increase in the binding sites of Fe3+ ions, in parallel with the increased exposure of the catalytic sites, leading to a higher atomic efficiency of the reaction.

2.
Animals (Basel) ; 11(8)2021 Aug 03.
Article in English | MEDLINE | ID: mdl-34438747

ABSTRACT

Brazil is the fifth largest country in the world with diverse socioeconomic and sanitary conditions, also being the fourth largest pig producer in the world. The aim of the present systematic review was to collect and summarize all HEV published data from Brazil (from 1995 to October 2020) performed in humans, animals, and the environment, in a One Health perspective. A total of 2173 papers were retrieved from five search databases (LILACs, Mendeley, PubMed, Scopus, and Web of Science) resulting in 71 eligible papers after application of exclusion/inclusion criteria. Data shows that HEV genotype 3 (HEV-3) was the only retrieved genotype in humans, animals, and environment in Brazil. The South region showed the highest human seroprevalence and also the highest pig density and industry, suggesting a zoonotic link. HEV-1 and 2 were not detected in Brazil, despite the low sanitary conditions of some regions. From the present review we infer that HEV epidemiology in Brazil is similar to that of industrialized countries (only HEV-3, swine reservoirs, no waterborne transmission, no association with low sanitary conditions). Hence, we alert for the implementation of HEV surveillance systems in swine and for the consideration of HEV in the diagnostic routine of acute and chronic hepatitis in humans.

3.
Article in English | MEDLINE | ID: mdl-33923769

ABSTRACT

The purpose of this study was to investigate the multivariate profile of different types of Brazilian runners and to identify the discriminant pattern of the distinct types of runners, as a runners' ability to self-classify well. The sample comprised 1235 Brazilian runners of both sexes (492 women; 743 men), with a mean age of 37.94 ± 9.46 years. Individual characteristics were obtained through an online questionnaire: Sex, age, body height (m) and body mass (kg), socioeconomic status, and training information (i.e., self-classification, practice time, practice motivation, running pace, frequency and training volume/week). Multivariate analysis of variance was conducted by sex and the discriminant analysis was used to identify which among running pace, practice time, body mass index and volume/training could differentiate groups such as "professional athletes", "amateur athletes" and "recreational athletes". For both sexes, running pace was the variable that better discriminated the groups, followed by BMI and volume/week. The practice time is not a good indicator to differentiate runner's types. In both sexes, semi-professional runners were those that better self-classify themselves, with amateur runners presenting the highest classification error. This information can be used to guide the long-term training, athlete's selection programs, and to identify the strengths and weaknesses of athletes.


Subject(s)
Running , Adult , Anthropometry , Brazil , Discriminant Analysis , Female , Humans , Male , Middle Aged , Motivation
4.
J Colloid Interface Sci ; 587: 479-488, 2021 Apr.
Article in English | MEDLINE | ID: mdl-33387842

ABSTRACT

The photo-Fenton activity of graphitic carbon nitride (g-C3N4) has been widely studied, nevertheless, its Fenton-like catalytic behavior in the dark has not yet been demonstrated. In the present work, it is shown that oxygenated g-C3N4 obtained at different temperatures (500-600 °C) can degrade indigo carmine with hydrogen peroxide in the dark by a reaction similar to a conventional Fenton's reaction. Based on an extensive characterization of g-C3N4, we conclude that Fenton-like activity is directly related to the oxygenated functional groups on g-C3N4 structure, mainly by -OH functional groups. Oxygenated functional groups (e.g., hydroquinone-like groups) can reduce the H2O2 and generate oxidizing hydroxyl radicals, just like in the Fenton reaction performed by metals. In addition to new information on g-C3N4 surface reactivity revealed by this study, the metal-free oxygenated g-C3N4 catalyst may be an alternative to traditional metal catalysts used in Fenton-like reactions for advanced oxidation.

5.
Sci Total Environ ; 764: 142802, 2021 Apr 10.
Article in English | MEDLINE | ID: mdl-33071145

ABSTRACT

BACKGROUND: Although an increasing body of data reports the detection of SARS-CoV-2 RNA in air, this does not correlate to the presence of infectious viruses, thus not evaluating the risk for airborne COVID-19. Hence there is a marked knowledge gap that requires urgent attention. Therefore, in this systematic review, viability/stability of airborne SARS-CoV-2, SARS-CoV and MERS-CoV viruses is discussed. METHODS: A systematic literature review was performed on PubMed/MEDLINE, Web of Science and Scopus to assess the stability and viability of SARS-CoV, MERS-CoV and SARS-CoV-2 on air samples. RESULTS AND DISCUSSION: The initial search identified 27 articles. Following screening of titles and abstracts and removing duplicates, 11 articles were considered relevant. Temperatures ranging from 20 °C to 25 °C and relative humidity ranging from 40% to 50% were reported to have a protective effect on viral viability for airborne SARS-CoV and MERS-CoV. As no data is yet available on the conditions influencing viability for airborne SARS-CoV-2, and given the genetic similarity to SARS-CoV and MERS-CoV, one could extrapolate that the same conditions would apply. Nonetheless, the effect of these conditions seems to be residual considering the increasing number of cases in the south of USA, Brazil and India, where high temperatures and humidities have been observed. CONCLUSION: Higher temperatures and high relative humidity can have a modest effect on SARS-CoV-2 viability in the environment, as reported in previous studies to this date. However, these studies are experimental, and do not support the fact that the virus has efficiently spread in the tropical regions of the globe, with other transmission routes such as the contact and droplet ones probably being responsible for the majority of cases reported in these regions, along with other factors such as human mobility patterns and contact rates. Further studies are needed to investigate the extent of aerosol transmission of SARS-CoV-2 as this would have important implications for public health and infection-control policies.


Subject(s)
COVID-19 , Middle East Respiratory Syndrome Coronavirus , Brazil , Humans , India , RNA, Viral , SARS-CoV-2
6.
Chemosphere ; 240: 124871, 2020 Feb.
Article in English | MEDLINE | ID: mdl-31546186

ABSTRACT

In Paracatu, a city in Minas Gerais State (Brazil), the gold mineral extraction produces wastes that contribute to environmental contamination by arsenic. This work describes the evaluation of arsenic concentration from soil of a gold mining area in Paracatu and the selection of arsenic resistant bacteria. In the process of culturing enrichment, 38 bacterial strains were isolated and the minimum inhibitory concentration (MIC) was determined in solid medium for each strain. Three bacterial strains named P1C1Ib, P2Ic and P2IIB were resistant to 3000 mg L-1 of arsenite. Analysis of 16S rDNA gene sequences revealed that these bacteria belong to Bacillus cereus and Lysinibacillus boronitolerans species. After cultivation of the strains P1C1Ib, P2Ic and P2IIIb, 69.38%-71.88% of arsenite and 82.39%-85.72% of arsenate concentrations were reduced from the culture medium, suggesting the potential application of theses strains in bioremediation processes.


Subject(s)
Arsenic/chemistry , Bioaccumulation/drug effects , Gold/chemistry , Mining/methods , Bacteria/genetics , Brazil
7.
J Cardiovasc Magn Reson ; 21(1): 50, 2019 08 15.
Article in English | MEDLINE | ID: mdl-31412875

ABSTRACT

BACKGROUND: Identifying the patients with hypertrophic cardiomyopathy (HCM) in whom the risk of sudden cardiac death (SCD) justifies the implantation of a cardioverter-defibrillator (ICD) in primary prevention remains challenging. Different risk stratification and criteria are used by the European and American guidelines in this setting. We sought to evaluate the role of cardiovascular magnetic resonance (CMR) late gadolinium enhancement (LGE) in improving these risk stratification strategies. METHODS: We conducted a multicentric retrospective analysis of HCM patients who underwent CMR for diagnostic confirmation and/or risk stratification. Eligibility for ICD was assessed according to the HCM Risk-SCD score and the American College of Cardiology Foundation/American Heart Association (ACCF/AHA) algorithm. The amount of LGE was quantified (LGE%) and categorized as 0%, 0.1-10%, 10.1-19.9% and ≥ 20%. The primary endpoint was a composite of SCD, aborted SCD, sustained ventricular tachycardia (VT), or appropriate ICD discharge. RESULTS: A total of 493 patients were available for analysis (58% male, median age 46 years). LGE was present in 79% of patients, with a median LGE% of 2.9% (IQR 0.4-8.4%). The concordance between risk assessment by the HCM Risk-SCD, ACCF/AHA and LGE was relatively weak. During a median follow-up of 3.4 years (IQR 1.5-6.8 years), 23 patients experienced an event (12 SCDs, 6 appropriate ICD discharges and 5 sustained VTs). The amount of LGE was the only independent predictor of outcome (adjusted HR: 1.08; 95% CI: 1.04-1.12; p <  0.001) after adjustment for the HCM Risk-SCD and ACCF/AHA criteria. The amount of LGE showed greater discriminative power (C-statistic 0.84; 95% CI: 0.76-0.91) than the ACCF/AHA (C-statistic 0.61; 95% CI: 0.49-0.72; p for comparison < 0.001) and the HCM Risk-SCD (C-statistic 0.68; 95% CI: 0.59-0.78; p for comparison = 0.006). LGE was able to increase the discriminative power of the ACCF/AHA and HCM Risk-SCD criteria, with net reclassification improvements of 0.36 (p = 0.021) and 0.43 (p = 0.011), respectively. CONCLUSIONS: The amount of LGE seems to outperform the HCM Risk-SCD score and the ACCF/AHA algorithm in the identification of HCM patients at increased risk of SCD and reclassifies a relevant proportion of patients.


Subject(s)
Cardiomyopathy, Hypertrophic/diagnostic imaging , Contrast Media/administration & dosage , Death, Sudden, Cardiac/etiology , Magnetic Resonance Imaging/standards , Practice Guidelines as Topic/standards , Adult , Brazil , Cardiomyopathy, Hypertrophic/complications , Cardiomyopathy, Hypertrophic/therapy , Clinical Decision-Making , Death, Sudden, Cardiac/prevention & control , Defibrillators, Implantable , Electric Countershock/instrumentation , Female , Humans , Male , Middle Aged , Patient Selection , Portugal , Predictive Value of Tests , Primary Prevention , Prognosis , Retrospective Studies , Risk Assessment , Risk Factors
8.
Ann Hepatol ; 17(2): 335-338, 2018 Mar 01.
Article in English | MEDLINE | ID: mdl-29469037

ABSTRACT

Hepatitis E in industrialized countries is mainly associated with genotype 3 hepatitis E virus (HEV) and normally causes a sporadic self-limiting disease in immunocompetent individuals. Unlike genotype 3, genotypes 1 and 2 circulate in developing countries, produce severe disease and occur in the epidemic form. Hepatitis E occurring in travellers returning from endemic areas in developing countries is not a novel epidemiological occurrence, however the vast majority of cases remain to be genetically studied. The present study describes two cases of severe acute hepatitis E that required hospitalization for 6 and 9 days in two individuals of Indian nationality that had recently migrated to Portugal to work. The retrieved HEV sequences both belonged to genotype 1 and had a high degree of nucleotide sequence identity, clustering with strains isolated in India and Nepal, in 2013 and 2014. Confirmed HEV genotypes of increased pathogenicity like genotype 1 are being introduced into otherwise naïve populations of industrialized countries such as European countries with consequences difficult to predict. As far as we know the present study is the first in Portugal to describe and genetically characterize imported cases of hepatitis E infection caused by HEV genotype 1.


Subject(s)
DNA, Viral/genetics , Hepatitis E virus/genetics , Hepatitis E/virology , Adult , Emigrants and Immigrants , Emigration and Immigration , Genotype , Hepatitis E/diagnosis , Hepatitis E/therapy , Hepatitis E virus/pathogenicity , Humans , India , Male , Middle Aged , Portugal , Severity of Illness Index , Treatment Outcome
9.
ChemSusChem ; 11(3): 589-597, 2018 02 09.
Article in English | MEDLINE | ID: mdl-29193761

ABSTRACT

Using dual-photoelectrode photoelectrochemical (PEC) devices based on earth-abundant metal oxides for unbiased water splitting is an attractive means of producing green H2 fuel, but is challenging, owing to low photovoltages generated by PEC cells. This problem can be solved by coupling n-type BiVO4 with n-type Bi4 V2 O11 to create a virtual p/n junction due to the formation of a hole-inversion layer at the semiconductor interface. Thus, photoelectrodes with high photovoltage outputs were synthesized. The photoelectrodes exhibited features of p- and n-type semiconductors when illuminated under an applied bias, suggesting their use as photoanode and photocathode in a dual-photoelectrode PEC cell. This concept was proved by connecting a 1 mol % W-doped BiVO4 /Bi4 V2 O11 photoanode with an undoped BiVO4 /Bi4 V2 O11 photocathode, which produced a high photovoltage of 1.54 V, sufficient to drive stand-alone water splitting with 0.95 % efficiency.


Subject(s)
Bismuth/chemistry , Electrochemical Techniques/instrumentation , Electrodes , Photochemical Processes , Vanadates/chemistry , Water/chemistry , Green Chemistry Technology , Microscopy, Electron, Scanning , Microscopy, Electron, Transmission , Semiconductors , Solar Energy
10.
Radiol. bras ; Radiol. bras;50(6): 359-365, Nov.-Dec. 2017. tab, graf
Article in English | LILACS | ID: biblio-896135

ABSTRACT

Abstract Objective: To assess the magnetic resonance imaging (MRI) patterns associated with central nervous system infection with Cryptococcus sp. in relation to patient immune status. Materials and Methods: This was a retrospective study of MRI data for 19 patients with neurocryptococcosis who underwent the examination between January 2000 and March 2014. The MRI characteristics examined included lesion topography, aspects of diffusion, T1-weighted images, T2-weighted images, and contrast enhancement patterns. Results: In all cases, cryptococcal infection was confirmed by cerebrospinal fluid analysis. Of the 19 patients, 10 were immunocompromised and 9 were immunocompetent. Abnormal imaging patterns occurred alone or in conjunction with other manifestations. The imaging patterns found in immunocompromised patients included the following: leptomeningeal enhancement, in 6; pachymeningeal enhancement, in 3 (due to intracranial hypotension in 2); perivascular space involvement, in 4; granulomas, in 2; hydrocephalus, in 2; miliary nodules, in 1; and plexitis, in 1. In immunocompetent patients, the following imaging patterns were observed: leptomeningeal enhancement, in 5; perivascular space involvement, in 3; granulomas, in 3; cryptococcoma, in 1; ventriculitis, in 1; and hydrocephalus, in 1. In 2 immunocompetent patients, diffusion-weighted imaging showed diffusion restriction in cerebral cryptococcal granuloma. Conclusion: In both groups, the most common imaging finding was leptomeningeal enhancement, followed by dilatation of perivascular spaces with the presence of mucoid material. Rare presentations, such as miliary nodules, plexitis, ventriculitis, and pachymeningeal enhancement, were also observed. None of the imaging patterns common to immunocompetent and immunocompromised patients differed significantly in frequency between them.


Resumo Objetivo: Avaliar os padrões de ressonância magnética (RM) associados à infecção do sistema nervoso central por Cryptococcus sp. em relação ao status imunológico dos pacientes. Materiais e Métodos: Dados de RM de 19 casos de neurocriptococose foram analisados retrospectivamente de janeiro de 2000 a março de 2014. As características de RM examinadas incluíram: sítio da lesão, aspectos em difusão, imagens ponderadas em T1 e T2 e padrões de realce pelo contraste. Resultados: A infecção por Cryptococcus sp. foi confirmada pela análise do liquor em todos os casos. Dos 19 pacientes, 10 eram imunossuprimidos e 9 eram imunocompetentes. Os padrões de imagem anormais ocorreram isoladamente ou em associação com outras manifestações. Os padrões de imagem encontrados nos pacientes imunossuprimidos incluíram: realce leptomeníngeo (n = 6), realce paquimeníngeo (n = 3; 2 devidos a hipotensão intracraniana), envolvimento do espaço perivascular (n = 4), granulomas (n = 2), hidrocefalia (n = 2), nódulos miliares (n = 1) e plexite (n = 1). Em pacientes imunocompetentes, os padrões de imagem incluíram: realce leptomeníngeo (n = 5), envolvimento do espaço perivascular (n = 3), granulomas (n = 3), criptococoma (n = 1), ventriculite (n = 1) e hidrocefalia (n = 1). As sequências ponderadas em difusão mostraram restrição em 2 pacientes imunocompetentes com granulomas intracerebrais por criptococose. Conclusão: O achado mais comum de imagem em ambos os grupos foi realce leptomeníngeo, seguido de dilatação dos espaços perivasculares pela presença do material mucoide. Apresentações raras como nódulos miliares, plexite, ventriculite e realce paquimeníngeo foram também observadas. Nenhum dos padrões de imagem comuns aos pacientes imunocompetentes e imunossuprimidos diferiu significativamente em frequência entre eles.

11.
Langmuir ; 33(43): 12235-12243, 2017 10 31.
Article in English | MEDLINE | ID: mdl-28988485

ABSTRACT

In general, the methodologies for the preparation of carbon dots (CDs) lead to the formation of nanostructures with size and surface chemistry heterogeneity. Because the electronic and optical properties of these nanoparticles are directly associated with these properties, the development of purification and selection strategies is essential. Herein, we report a systematic study of the spontaneous partition and separation of highly oxidized carbon dots (OCDs) prepared by the dehydration and oxidation reactions of cotton cellulose in aqueous two-phase systems (ATPSs) based on polymer-salt pairs. The partition of the CDs was investigated in different ATPSs in which the effects of the cations and anions of the salts, molecular mass and nature of the polymer, tie-line length, initial pH, and surface modification of the nanoparticles on the partition coefficient (K) were evaluated. The results showed that the best separation occurred with a system consisting of PEO1500 + lithium sulfate + water using reduced CDs with hydrazine. Alternatively, the lowest value of K, 0.79, was obtained for a poly(ethylene oxide) PEO1500 + sodium tartrate + water system with pH = 6 using OCDs. The detailed analyses of the top and bottom phases of the systems with fluorescence and ultraviolet-visible spectroscopy showed that ATPSs are capable, in addition to partitioning, of separating the nanoparticles with different optical properties, which are directly associated with the surface properties and particle sizes. We believe that the presented methodology is an alternative, practical, fast, and potentially scalable technique for the separation of carbon nanostructures with different optical properties.

12.
Langmuir ; 33(43): 11857-11861, 2017 10 31.
Article in English | MEDLINE | ID: mdl-28957632

ABSTRACT

KOH activation of a mesophase pitch produces very efficient carbons for the removal of sulfide in aqueous solution, increasing the sulfur oxidation rate with the degree of activation of the carbon. These carbons are characterized by their graphitic structures, with domains of sizes of around 20 nm, and a moderate concentration of surface oxygen groups (0.2-0.5 mmol·g-1) dominating the basic groups. Because the activation leads first to a strong development of the micropores and later to a development of the mesopores, the surface area values are always high, reaching values of as high as 3250 m2·g-1 in the most activated carbon, with a volume of mesopores of as high as 44% of the total pore volume. In the presence of this carbon, the sulfide oxidation rate is 100 times higher than that found for a commercial activated carbon, the results indicating that the porosity of the carbon, especially mesoporosity, plays a role more important than the structure or the chemical nature of the carbon in the kinetics of sulfide oxidation to different polysulfides.

13.
Radiol Bras ; 50(6): 359-365, 2017.
Article in English | MEDLINE | ID: mdl-29307925

ABSTRACT

OBJECTIVE: To assess the magnetic resonance imaging (MRI) patterns associated with central nervous system infection with Cryptococcus sp. in relation to patient immune status. MATERIALS AND METHODS: This was a retrospective study of MRI data for 19 patients with neurocryptococcosis who underwent the examination between January 2000 and March 2014. The MRI characteristics examined included lesion topography, aspects of diffusion, T1-weighted images, T2-weighted images, and contrast enhancement patterns. RESULTS: In all cases, cryptococcal infection was confirmed by cerebrospinal fluid analysis. Of the 19 patients, 10 were immunocompromised and 9 were immunocompetent. Abnormal imaging patterns occurred alone or in conjunction with other manifestations. The imaging patterns found in immunocompromised patients included the following: leptomeningeal enhancement, in 6; pachymeningeal enhancement, in 3 (due to intracranial hypotension in 2); perivascular space involvement, in 4; granulomas, in 2; hydrocephalus, in 2; miliary nodules, in 1; and plexitis, in 1. In immunocompetent patients, the following imaging patterns were observed: leptomeningeal enhancement, in 5; perivascular space involvement, in 3; granulomas, in 3; cryptococcoma, in 1; ventriculitis, in 1; and hydrocephalus, in 1. In 2 immunocompetent patients, diffusion-weighted imaging showed diffusion restriction in cerebral cryptococcal granuloma. CONCLUSION: In both groups, the most common imaging finding was leptomeningeal enhancement, followed by dilatation of perivascular spaces with the presence of mucoid material. Rare presentations, such as miliary nodules, plexitis, ventriculitis, and pachymeningeal enhancement, were also observed. None of the imaging patterns common to immunocompetent and immunocompromised patients differed significantly in frequency between them.


OBJETIVO: Avaliar os padrões de ressonância magnética (RM) associados à infecção do sistema nervoso central por Cryptococcus sp. em relação ao status imunológico dos pacientes. MATERIAIS E MÉTODOS: Dados de RM de 19 casos de neurocriptococose foram analisados retrospectivamente de janeiro de 2000 a março de 2014. As características de RM examinadas incluíram: sítio da lesão, aspectos em difusão, imagens ponderadas em T1 e T2 e padrões de realce pelo contraste. RESULTADOS: A infecção por Cryptococcus sp. foi confirmada pela análise do liquor em todos os casos. Dos 19 pacientes, 10 eram imunossuprimidos e 9 eram imunocompetentes. Os padrões de imagem anormais ocorreram isoladamente ou em associação com outras manifestações. Os padrões de imagem encontrados nos pacientes imunossuprimidos incluíram: realce leptomeníngeo (n = 6), realce paquimeníngeo (n = 3; 2 devidos a hipotensão intracraniana), envolvimento do espaço perivascular (n = 4), granulomas (n = 2), hidrocefalia (n = 2), nódulos miliares (n = 1) e plexite (n = 1). Em pacientes imunocompetentes, os padrões de imagem incluíram: realce leptomeníngeo (n = 5), envolvimento do espaço perivascular (n = 3), granulomas (n = 3), criptococoma (n = 1), ventriculite (n = 1) e hidrocefalia (n = 1). As sequências ponderadas em difusão mostraram restrição em 2 pacientes imunocompetentes com granulomas intracerebrais por criptococose. CONCLUSÃO: O achado mais comum de imagem em ambos os grupos foi realce leptomeníngeo, seguido de dilatação dos espaços perivasculares pela presença do material mucoide. Apresentações raras como nódulos miliares, plexite, ventriculite e realce paquimeníngeo foram também observadas. Nenhum dos padrões de imagem comuns aos pacientes imunocompetentes e imunossuprimidos diferiu significativamente em frequência entre eles.

14.
Sci Rep ; 6: 31406, 2016 08 09.
Article in English | MEDLINE | ID: mdl-27503274

ABSTRACT

The conversion of solar energy into hydrogen fuel by splitting water into photoelectrochemical cells (PEC) is an appealing strategy to store energy and minimize the extensive use of fossil fuels. The key requirement for efficient water splitting is producing a large band bending (photovoltage) at the semiconductor to improve the separation of the photogenerated charge carriers. Therefore, an attractive method consists in creating internal electrical fields inside the PEC to render more favorable band bending for water splitting. Coupling ferroelectric materials exhibiting spontaneous polarization with visible light photoactive semiconductors can be a likely approach to getting higher photovoltage outputs. The spontaneous electric polarization tends to promote the desirable separation of photogenerated electron- hole pairs and can produce photovoltages higher than that obtained from a conventional p-n heterojunction. Herein, we demonstrate that a hole inversion layer induced by a ferroelectric Bi4V2O11 perovskite at the n-type BiVO4 interface creates a virtual p-n junction with high photovoltage, which is suitable for water splitting. The photovoltage output can be boosted by changing the polarization by doping the ferroelectric material with tungsten in order to produce the relatively large photovoltage of 1.39 V, decreasing the surface recombination and enhancing the photocurrent as much as 180%.


Subject(s)
Bismuth/chemistry , Calcium Compounds/chemistry , Hydrogen/chemistry , Oxides/chemistry , Titanium/chemistry , Vanadates/chemistry , Electrochemical Techniques , Photochemical Processes , Semiconductors , Solar Energy , Water
18.
Carbohydr Polym ; 90(1): 210-7, 2012 Sep 01.
Article in English | MEDLINE | ID: mdl-24751032

ABSTRACT

Bio-based nanocomposites were obtained through covalent linkage between cellulose nanocrystals (CNCs) and the natural polymer chitosan (CH). The CNCs were first functionalized with methyl adipoyl chloride (MAC) and the reactive end groups on the surface of the CNCs were reacted with the amino groups of the CH biopolymer in an aqueous medium. The functionalized CNCs and the resulting nanocomposites were characterized using FTIR, TEM, XRD, and elemental analyses. Characterization of the functionalized CNCs showed that up to 8% of the hydroxyl groups in the nanocrystals were substituted by the MAC residue. The covalent linkage between the CNCs and CH was confirmed by FTIR spectroscopy. The nanocomposites demonstrated a significant improvement in the mechanical performance and a considerable decrease in the hydrophilicity relative to the neat chitosan. The approach used in this work can be extended to other natural polymers.


Subject(s)
Cellulose/chemistry , Chitosan/chemistry , Nanocomposites/chemistry , Nanoparticles/chemistry , Cellulose/metabolism , Chitosan/metabolism , Nanoparticles/metabolism , Spectroscopy, Fourier Transform Infrared/methods , Tensile Strength
19.
Biomacromolecules ; 11(2): 473-80, 2010 Feb 08.
Article in English | MEDLINE | ID: mdl-20055503

ABSTRACT

A new biodegradable nanocomposite was obtained from layer-by-layer (LBL) technique using highly deacetylated chitosan and eucalyptus wood cellulose nanowhiskers (CNWs). Hydrogen bonds and electrostatic interactions between the negatively charged sulfate groups on the whisker surface and the ammonium groups of chitosan were the driving forces for the growth of the multilayered films. The film growth was followed by UV-vis spectroscopy through the maximum value of the absorption band at 194 nm and showed the deposition of 14.7 mg.m(-2) of chitosan polymer in each cycle. Scanning electron microscopy showed high density and homogeneous distribution of CNWs adsorbed on each chitosan layer. Cross-section characterization of the assembled films indicates an average of approximately 7 nm of thickness per bilayer. The results presented in this work indicate that the methodology used can be extended to different biopolymers for the design of new biobased nanocomposites in a wide range of applications such as biomedical and food packaging.


Subject(s)
Chemistry, Pharmaceutical/methods , Chitosan/chemistry , Nanocomposites/chemistry , Eucalyptus/chemistry , Plant Extracts/chemistry , Surface Properties
20.
J Hazard Mater ; 165(1-3): 87-94, 2009 Jun 15.
Article in English | MEDLINE | ID: mdl-18996644

ABSTRACT

Ferric chloride was used as a new activating agent, to obtain activated carbons (AC) from agro industrial waste (coffee husks). This material was compared with two samples from the same raw material: one of them activated by using the classical activating agent, zinc chloride, and the other, activated with a mixture of the two mentioned activating agents in the same mass proportion. The carbonaceous materials obtained after the activation process showed high specific surface areas (BET), with values higher than 900 m(2)g(-1). It is interesting to observe that the activation with FeCl(3) produces smaller pores compared to the activation with ZnCl(2). An important fact to emphasize in the use of FeCl(3) as activating agent is the activation temperature at 280 degrees C, which is clearly below to the temperature commonly employed for chemical or physical activation, as described in the bibliography. All the studied materials showed different behaviors in the adsorption of methylene blue dye and phenol from aqueous solutions.


Subject(s)
Charcoal/chemical synthesis , Coffee/chemistry , Ferric Compounds/chemistry , Adsorption , Chlorides/chemistry , Indicators and Reagents , Methylene Blue/isolation & purification , Phenol/isolation & purification , Temperature , Zinc Compounds/chemistry
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