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Factorial design to optimize microwave-assisted synthesis of FDU-1 silica with a new triblock copolymer

Silva, Luis Carlos Cides da; REIS, T. V. S. dos; COSENTINO, I. C.; Fantini, Marcia Carvalho de Abreu; MATOS, J. R.; BRUNS, R. E.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
813.05945%
The synthesis of FDU-1 silica with large cage-like mesopores prepared with a new triblock copolymer Vorasurf 504 (R) (Eo)(38)(BO)(46)(EO)(38) was developed. The hydrothermal treatment temperature, the dissolution of the copolymer in ethanol, the HCl concentration, the solution stirring time and the hydrothermal treatment time in a microwave oven were evaluated with factorial design procedures. The dissolution in ethanol is important to produce a material with better porous morphology. Increases in the hydrothermal temperature (100 degrees C) and HCl concentration (2 M) improved structural, textural and chemical properties of the cubic ordered mesoporous silica. Also, longer times induced better physical and chemical property characteristics. (C) 2010 Elsevier Inc. All rights reserved.; FAPESP[03/10067-3]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); FAPESP[2007/07646-2]; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); CNPq; CAPES; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Síntese e caracterização de compósitos de NiO-YSZ-CeO2 com tratamento hidrotermal assistido por micro-ondas; Synthesis and caracterization of NiO-YSZ-CeO2 composites with microwave-assisted hydrothermal treatment

Pinheiro, Lucas Batochi
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 03/10/2013 PT
Relevância na Pesquisa
708.4896%
Neste trabalho foi avaliado o efeito de um tratamento hidrotermal assistido por micro-ondas (HMO) nas propriedades estruturais, térmicas e elétricas de compósitos NiO-YSZ-CeO2 sintetizados pelo método de coprecipitação de hidróxidos. Curvas termogravimétricas e térmicas diferenciais simultâneas (TG/ATD) em conjunto com medidas de difração de raios X (DRX) mostraram que o tratamento HMO contribuiu para uma maior cristalização da fase hidróxido de níquel. A retração linear dos compactos durante o processo de sinterização foi observada por análise termomecânica (ATM) e os resultados obtidos indicaram uma maior sinterabilidade para as amostras submetidas ao tratamento HMO. Compactos cerâmicos foram sinterizados em forno convencional resistivo e micro-ondas. Estes compactos tiveram suas microestruturas analisadas por microscopia eletrônica de varredura (MEV) e propriedades elétricas investigadas por espectroscopia de impedância (EI). As imagens de MEV apresentaram homogeneidade das fases presentes e grãos com tamanho submicrométrico. As medidas de EI mostraram que as amostras tratadas em sistema hidrotermal assistido por micro-ondas, apresentaram aumento de condutividade elétrica para temperaturas acima de 500 ºC...

Síntese e caracterização do composto SrTiO3 e SrTi1-xFexO3 através do método hidrotermal assistido por microondas; Synthesis and characterization of SrTiO3 and SrTi1-xFexO3 compounds prepared by microwave-assisted hydrothermal method

Silva, Luís Fernando da
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 26/08/2013 PT
Relevância na Pesquisa
718.2628%
Dentre os materiais de estrutura perovskita, o titanato de estrôncio, SrTiO3, é um dos mais conhecidos e estudado por apresentar interessantes propriedades como a ferroeletricidade, fotoluminescência, entre outras. Além disso, tem sido reportado na literatura que a adição de diferentes dopantes ao composto SrTiO3 modifica suas propriedades dando origem, por exemplo, a materiais para serem aplicados como sensores de gás ou na fotocatálise. Diferentes trabalhos encontrados na literatura descrevem a síntese do composto SrTiO3 e suas soluções sólidas através do método hidrotermal. Entretanto, poucos trabalhos tiveram como foco o estudo do precursor de Ti e do íon dopante nas propriedades estruturais, morfológicas, ópticas e elétricas destes materiais. Desta forma, este trabalho de tese teve como objetivo o estudo da influência da composição e de alguns parâmetros de síntese sobre as propriedades estruturais, morfológicas e ópticas do composto SrTiO3 preparado através do método hidrotermal assistido por microondas HAM. Inicialmente, foi realizada a síntese do composto SrTiO3 a 140oC por 10 minutos, onde se verificou a possibilidade de controlar a morfologia e a propriedade fotoluminescente das amostras através do tipo de precursor de Ti utilizado. Em uma segunda etapa do trabalho...

Structural and optical properties of CaTiO3 perovskite-based materials obtained by microwave-assisted hydrothermal synthesis: An experimental and theoretical insight

Moreira, Mario L.; Paris, Elaine C.; do Nascimento, Gabriela S.; Longo, Valeria M.; Sambrano, Julio R.; Mastelaro, Valmor R.; Bernardi, Maria I. B.; Andres, Juan; Varela, José Arana; Longo, Elson
Fonte: Pergamon-Elsevier B.V. Ltd Publicador: Pergamon-Elsevier B.V. Ltd
Tipo: Artigo de Revista Científica Formato: 5174-5185
ENG
Relevância na Pesquisa
712.2181%
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Processo FAPESP: 98/14324-8; CaTiO3 powders were synthesized using both a polymeric precursor method (CTref) and a microwave-assisted hydrothermal (CTHTMW) method in order to compare the chemical and physical properties of the perovskite-based material as a function of the synthesis method. To this end, X-ray diffraction, Raman spectroscopy, inductively coupled plasma atomic emission spectroscopy and experimental Ti and Ca K-edge X-ray absorption near-edge structure spectroscopy, as well as measurements of photoluminescence (PL) emission, were used to characterize the typical bottom-up process of the CaTiO3 perovskite phase at different times. Detailed Rietveld refinements show a random polycrystalline distortion in the powder structure, which can be associated with the tilting (alpha angle < O-Ti-O) between adjacent TiO6 octahedra (intermediate range) for CTHTMW samples and an intrinsic TiO6 distortion (short range) in relation to the polymeric precursor CTref sample. These properties were further investigated by first-principles calculations based on the density functional theory at the B3LYP level. The relationship between this tilting on the PL profile is highlighted and discussed. Thus...

Photoluminescence properties and synthesis of a PZT mesostructure obtained by the microwave-assisted hydrothermal method

Teixeira, G. F.; Zaghete, M. A.; Gasparotto, G.; Costa, M. G. S.; Espinosa, J. W. M.; Longo, Elson; Varela, José Arana
Fonte: Elsevier B.V. Sa Publicador: Elsevier B.V. Sa
Tipo: Artigo de Revista Científica Formato: 124-127
ENG
Relevância na Pesquisa
707.0148%
Micro-cube-shaped lead zirconate titanate was synthesized using the microwave-assisted hydrothermal method. Photoluminescence and field emission scanning electron microscopy were used for monitoring the formation of mesocrystals. Based on these results, a growth mechanism was then proposed which involved nanoparticle aggregation, nanoplate self-assembly on specific architecture and the final formation of mesoscopic micro-cube-shaped lead zirconate titanate. (C) 2011 Elsevier B. V. All rights reserved.

Microwave-assisted hydrothermal synthesis of nanocrystalline SnO powders

Pires, F. I.; Joanni, E.; Savu, R.; Zaghete, M. A.; Longo, Elson; Varela, José Arana
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 239-242
ENG
Relevância na Pesquisa
715.9601%
Tin oxide (SnO) powders were obtained by the microwave-assisted hydrothermal synthesis technique using SnCl2 center dot 2H(2)O as a precursor. By changing the hydrothermal processing time, temperature, the type of mineralizing agent (NaOH, KOH or NH4 OH) and its concentration, SnO crystals having different sizes and morphologies could be achieved. The powders were characterized by X-ray diffraction (X-ray), Field Emission Scanning Electron Microscopy (FE-SEM), High Resolution Transmission Electron Microscopy (HR-TEM) and Selected Area Electron Diffraction (SAED). The results showed that plate-like form is the characteristic morphology of growth and the TEM analyses indicate the growth direction as (200). (c) 2007 Elsevier B.V. All rights reserved.

Microwave-assisted hydrothermal synthesis of ZnO powders with different reagents

Xavier, C. S.; De Moura, A. P.; Li, M. S.; Varela, José Arana; Longo, Elson; Cava, S.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 405-408
ENG
Relevância na Pesquisa
726.5617%
In this work, zinc oxide powders were synthesized by microwave-assisted hydrothermal method in basic medium. These powders were analyzed by X-ray diffraction (XRD), Field-emisson gum scanning electron microscopy (FEG-SEM), Ultraviolet-visible (UV-vis) absorption spectroscopy and photoluminescence (PL) measurements. XRD pattern confirmed that the pure ZnO phases were obtained after MH processing performed at 130°C/ 1h. FEG-SEM micrographs reveals that these nanostructures are made up of ZnO plates. UV-vis results were employed to determine the optical band gap these materials. Also, it showed existence of photoluminescence (PL) in the different zinc powders. An orange PL emission when excited by 350 nm wavelength at room temperature was observad in the different powders.

Synthesis of wurtzite ZnS nanoparticles using the microwave assisted solvothermal method

La Porta, Felipe A.; Ferrer, Mateus M.; De Santana, Yuri V.B.; Raubach, Cristiane W.; Longo, Valéria M.; Sambrano, Júlio R.; Longo, Elson; Andrés, Juan; Li, Máximo S.; Varela, José Arana
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 153-159
ENG
Relevância na Pesquisa
710.8031%
In this article, we report the development of an efficient and rapid microwave assisted solvothermal (MAS) method to prepare wurtzite ZnS nanoparticles at 413 K using different precursors. The materials obtained were analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (MET) ultraviolet-visible (UV-vis) and photoluminescence (PL) measurements. The structure, surface chemical composition and optical properties were investigated as a function of the precursor. In addition, effects as well as merits of microwave heating on the processing and characteristics of ZnS nanoparticles obtained are reported. The possible formation mechanism and optical properties of these nanoparticles were also reported. © 2012 Elsevier B.V. All rights reserved.

TiO2 synthesized by microwave assisted solvothermal method: Experimental and theoretical evaluation

Moura, K. F.; Maul, J.; Albuquerque, A. R.; Casali, G. P.; Longo, E.; Keyson, D.; Souza, A. G.; Sambrano, J. R.; Santos, I. M. G.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 171-177
ENG
Relevância na Pesquisa
713.05945%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); In this study, a microwave assisted solvothermal method was used to synthesize TiO2 with anatase structure. The synthesis was done using Ti (IV) isopropoxide and ethanol without templates or alkalinizing agents. Changes in structural features were observed with increasing time of synthesis and evaluated using periodic quantum chemical calculations. The anatase phase was obtained after only 1 min of reaction besides a small amount of brookite phase. Experimental Raman spectra are in accordance with the theoretical one. Micrometric spheres constituted by nanometric particles were obtained for synthesis from 1 to 30 min, while spheres and sticks were observed after 60 min. (c) 2013 Elsevier Inc. All rights reserved.

Titanate nanotubes produced from microwave-assisted hydrothermal synthesis: Photocatalytic and structural properties

Manfroi, Daniela C.; Anjos, Ademir dos; Cavalheiro, Alberto A.; Perazolli, Leinig A.; Varela, Jose A.; Zaghete, Maria A.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 14483-14491
ENG
Relevância na Pesquisa
707.0148%
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Processo FAPESP: 13/07296-2; Titanate nanotubes were successfully synthesized using the microwave-assisted hydrothermal method from commercial TiO2-anatase powder. Several samples were obtained at varying temperatures and time. Powder samples containing titanate nanotube (Na2Ti6O13) single phase were obtained at 130 degrees C for 4 h and 150 degrees C for 2 h, demonstrating the kinetics dependence of reaction temperature. Through XRD analysis and electron diffraction pattern, the nanotube structures were found to be composed of a short range ordering, thus giving rise to a broad XRD peak profile. The higher time and temperature (150 degrees C for 4 h) led to the formation of more organized structures. The nanotubes UV-vis spectra showed a band gap of 3.90 eV and a shoulder on the curve which led to another band gap value 3.25 eV. The photoluminescence spectrum emission peak presented a significant decrease, indicating the reduction of surface or structural defects of titanate nanotubes due to longer hydrothermal treatment duration. All structural...

Factorial design to optimize microwave-assisted synthesis of FDU-1 silica with a new triblock copolymer

SILVA, L. C. Cides da; REIS, T. V. S. dos; COSENTINO, I. C.; FANTINI, M. C. A.; MATOS, J. R.; BRUNS, R. E.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
810.7567%
The synthesis of FDU-1 silica with large cage-like mesopores prepared with a new triblock copolymer Vorasurf 504 (R) (Eo)(38)(BO)(46)(EO)(38) was developed. The hydrothermal treatment temperature, the dissolution of the copolymer in ethanol, the HCl concentration, the solution stirring time and the hydrothermal treatment time in a microwave oven were evaluated with factorial design procedures. The dissolution in ethanol is important to produce a material with better porous morphology. Increases in the hydrothermal temperature (100 degrees C) and HCl concentration (2 M) improved structural, textural and chemical properties of the cubic ordered mesoporous silica. Also, longer times induced better physical and chemical property characteristics. (C) 2010 Elsevier Inc. All rights reserved.; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Synthesis of aliphatic suberin-like polyesters by ecofriendly catalytic systems

Sousa, Andreia F.; Silvestre, Armando J. D.; Gandini, Alessandro; Neto, Carlos Pascoal
Fonte: SAGE Publications Publicador: SAGE Publications
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
707.0148%
A rapid and ecofriendly microwave assisted p-dodecylbenzenesulfonic acid (DBSA) emulsion polycondensation of long-chain suberin model comonomers was successfully carried out for the first time. Microwave irradiation reduced drastically the reaction time to only 15 min, compared with the DBSA/water polycondensation under conventional heating. Bulk polycondensation using CALB lipase or Bi(OTf)(3) were also carried out with isolation yields up to 93% and number-average molecular weights up to around 7300.

Microwave-assisted synthesis and antileishmanial activity of 3-methoxycarbonyl-γ-butyrolactone derivatives

Pinatto-Botelho,Marcos F.; Crotti,Antonio E. M.; Souza,Julia M. de; Magalhães,Lizandra G.; Donate,Paulo M.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2014 EN
Relevância na Pesquisa
1018.2628%
We describe the microwave-assisted synthesis of ten 3-methoxycarbonyl-γ-butyrolactone derivatives and evaluate their in vitro antileishmanial activity against promastigote forms of Leishmania amazonensis. The synthesis furnished most of the compounds in 80-95% yield and reactions lasted about 10-20 min. Most of the compounds displayed IC50 values higher than 400 µM. Compounds 5 (trans-3-(p-methoxy)benzyl-4-methyl-3-methoxycarbonyl-γ-butyrolactone) and 10 (trans-3-(p-methoxy)benzyl-4-benzyl-3-methoxycarbonyl-γ-butyrolactone) were the exceptions: they displayed IC50 values of 170.4 and 179.6 µM, respectively, suggesting that the leishmanicidal activity of 3-methoxycarbonyl-γ-butyrolactones may be related to the nature and size of the substituent at position C-4.

Microwave Assisted Synthesis and Sintering of Ba0.5Sr0.5Co0.8Fe0.2O3-δ Perovskite

Nuernberg,Rafael Bianchini; Morelli,Márcio Raymundo
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2015 EN
Relevância na Pesquisa
825.6624%
Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) perovskite-type oxide is currently one of the most promising materials for applications in solid-oxide fuel cells (SOFCs), protonic ceramic fuel cells (PCFCs), oxygen separation membranes, and catalytic membranes for methane conversion. BSCF powder synthesis has received considerable attention and new synthesis methods have been proposed to obtain nanoscale powders with high chemical homogeneity. In this study, BSCF perovskite powder has been successfully prepared by microwave assisted combustion in aqueous solution. The synthesized powder was characterized by DSC, BET, XRD, and SEM. BSCF powder presented phase homogeneity, high specific surface area (9.93 g/m2) and nanometric crystallite size (23nm). The microwave sintering has been conducted in different conditions of dwell time and temperature. The influence of the temperature and the dwell time on microstructure was evaluated by optical microscopy. The results showed that microwave sintering could achieve the same densification compared to conventional sintering with only 10% of processing time. This shorter processing time has resulted in a reduction of grain size of up to 46.5%, compared to conventional sintering.

Microwave-Assisted Synthesis of N-Phenylsuccinimide

Shell, Thomas A.; Shell, Jennifer R.; Poole, Kathleen A.; Guetzloff, Thomas F.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/10/2011 EN
Relevância na Pesquisa
713.05945%
A microwave-assisted synthesis of N-phenylsuccinimide has been developed for the second-semester organic teaching laboratory. Utilizing this procedure, N-phenylsuccinimide can be synthesized by heating a mixture of aniline and succinic anhydride in a domestic microwave oven for four minutes in moderate yields (40–60%). This technique reduces the reaction time as compared to the traditional synthesis by several hours, which allows the preparation to be achieved in a single organic chemistry laboratory period. This reaction is performed in the absence of solvent, is energy efficient, and is atom economical; therefore, it represents a “greener” preparation than the traditional synthesis of N-phenylsuccinimide.

Microwave-assisted synthesis of macrocycles via intramolecular and/or bimolecular Ullmann coupling

Shen, Li; Simmons, Charles J.; Sun, Dianqing
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
719.3753%
Microwave-assisted synthesis of macrocyclic diaryl ethers via intramolecular and/or bimolecular Ullmann coupling is described. Using the optimized conditions, a panel of macrocycles, with different substitution patterns, ring sizes, and linkers, has been successfully synthesized using microwave irradiation. To the best of our knowledge, this work represents the first examples of the microwave-assisted synthesis of macrocyclic diaryl ethers via intramolecular and/or bimolecular Ullmann coupling.

Microwave-Assisted Synthesis of Phenothiazine and Quinoline Derivatives

Găină, Luiza; Cristea, Castelia; Moldovan, Claudia; Porumb, Dan; Surducan, Emanoil; Deleanu, Călin; Mahamoud, Abdalah; Barbe, Jacques; Silberg, Ioan A.
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
Publicado em 13/02/2007 EN
Relevância na Pesquisa
719.3753%
Application of a dynamic microwave power system in the chemical synthesis of some phenothiazine and quinoline derivatives is described. Heterocyclic ring formation, aromatic nucleophilic substitution and heterocyclic aldehydes/ketones condensation reactions were performed on solid support, or under solvent free reaction conditions. The microwave-assisted Duff formylation of phenothiazine was achieved. Comparison of microwave-assisted synthesis with the conventional synthetic methods demonstrates advantages related to shorter reaction times and in some cases better reaction yields.

Comparison of Conventional and Microwave-assisted Synthesis of Benzotriazole Derivatives

Shah, J. J.; Mohanraj, Krishnapriya
Fonte: Medknow Publications & Media Pvt Ltd Publicador: Medknow Publications & Media Pvt Ltd
Tipo: Artigo de Revista Científica
Publicado em //2014 EN
Relevância na Pesquisa
723.9916%
A green chemistry approach for organic synthesis is described here, which involves microwave exposure of reactants in presence or absence of solvents. A novel and simple method has been developed for the synthesis of some benzotriazole derivatives under microwave irradiation. In addition, these compounds were synthesised also by conventional heating procedures for comparison. All the compounds synthesised were characterised by melting point, TLC, IR and 1H NMR spectroscopy. Comparison between conventional and microwave-assisted synthesis was done by comparing total reaction time and percentage yield. The results suggest that microwave-assisted syntheses lead to higher yields within very short reaction times. On antifungal evaluation by cup plate method, all compounds showed antifungal activity. One compound showed activity similar to and two compounds showed better activity than standard antifungal drug flucanazole.

Magnetic behavior of lamellar mnps3 and cdps3 composites with a paramagnetic manganese(iii) macrocyclic guest

Valencia, P.; Manzur, J.; Garcia, A. M,; Paredes-Garcia, V.; ...[et al.].
Fonte: Sociedad Chilena de Química Publicador: Sociedad Chilena de Química
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
718.8354%
Indexación: Scielo; Six new composites derived from the intercalation of the MPS3 phases (M = MnII, CdIII) with the macrocyclic manganese(III) complex [MnL(H2O)2].NO3(H2O) (LH2 = Schiff base macrocyclic ligand derived from the condensation of 2-hydroxy-5-methy1-1,3-benzene-dicarbaldehyde and 1,2-diamine-benzene) were obtained by two different synthetic procedures: a conventional and a microwave assisted method. The composites [MnL]0.25K0.15Mn0.80 PS3(H2O)~1.0 (1), and [MnL]0.25K0.15Cd 0. 80PS3(H2O)~0.5 (2) were obtained by the conventional method, after stirring a suspension of the corresponding potassium precursor and the macrocyclic complex for two weeks, while [MnL]0.35K0.15Mn0.80 PS3(H2O)~1.0 (3) and [MnL]0.25K0.15Cd 0. 80PS3(H2O)~0.5 (4) after stirring for four weeks at room temperature. Using a microwave assisted reaction permitted to obtain in a shorter period of time as compared with the conventional method, composites [MnL]0.20K0.15Mn0.80 PS3(H2O)~1.0 (5) and [MnL]0.15K0.15Cd 0. 80PS3(H2O)~0.5 (6). All the M = MnII, MnIII composites show a bulk antiferromagnetic behavior. However, the spontaneous magnetization present at low temperature in the potassium precursor K0.40Mn0.80 PS3(H2O)~1.0 is observable in composite [MnL]0.20K0.15Mn0.80 PS3(H2O)~1.0 (5)...

Novel and Fast Microwave-Assisted Synthesis of Carbon Quantum Dots from Raw Cashew Gum

Pires,Natalia R.; Santos,Clara M. W.; Sousa,Rayane R.; Paula,Regina C. M. de; Cunha,Pablyana L. R.; Feitosa,Judith P. A.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2015 EN
Relevância na Pesquisa
922.57734%
Carbon quantum dots (C-dots) with average size of 9 nm were synthesized from an aqueous solution of raw cashew gum (RCG) using a novel and fast microwave-assisted technique which involves two steps. In the first step (partial depolymerization in solution) some monomer units are formed through the autohydrolysis of CG and a small amount of 5-hydroxymethyl furfural can be obtained. The second step involves polycondensation/polymerization to give rise to a polyfuranic structure followed by aromatization/carbonization and nuclear burst. At the end of the process a composite of partially depolymerized CG and C-dot was formed. A mechanism involved in microwave-assisted two-steps synthesis was suggested. Although no passivation reagent was used, an intensely blue photoluminescent material in UV light was obtained. C-dot was characterized by spectroscopy in the medium infrared, thermal analysis, gel permeation chromatography, transmission electron microscopy, zeta potential, and photoluminescence.