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This paper reports the successful synthesis of magnetic nanocomposite of calcium ferrite with nitrogen doped graphene oxide (CaFe2O4-NGO) for the effective removal of Pb(II) ions and photocatalytic degradation of congo red and p-nitrophenol. X-ray diffraction (XRD), Fourier transform infrared (FT-IR), transmission electron microscopy (TEM), and scanning electron microscopy-energy dispersive X-ray (SEM-EDX) techniques confirmed the presence of NGO and CaFe2O4 in the nanocomposite. The Mössbauer studies depicted the presence of paramagnetic doublet and sextet due to presence of CaFe2O4 NPs in the nanocomposite. The higher BET surface area in case of CaFe2O4-NGO (52.86 m2/g) as compared to CaFe2O4 NPs (23.45 m2/g) was ascribed to the effective modulation of surface in the presence of NGO. Adsorption followed the Langmuir model with maximum adsorption capacity of 780.5 mg/g for Pb(II) ions. Photoluminescence spectrum of nanocomposite displayed four-fold decrease in the intensity, as compared to ferrite NPs, thus confirming its high light capturing potential and enhanced photocatalytic activity. The presence of NGO in nanocomposite offered an excellent visible light driven photocatalytic performance. The quenching experiments supported ●OH and O2●− radicals as the main reactive species involved in carrying out the catalytic system. The presence of Pb(II) had synergistic effect on photocatalytic degradation of pollutants. This study highlights the synthesis of CaFe2O4-NGO nanocomposite as an efficient adsorbent and photocatalyst for remediating pollutants.
Manmeet Kaur; Manpreet Kaur; Dhanwinder Singh; Aderbal Oliveira; Vijayendra Garg; Virender Sharma. Synthesis of CaFe2O4-NGO Nanocomposite for Effective Removal of Heavy Metal Ion and Photocatalytic Degradation of Organic Pollutants. Nanomaterials 2021, 11, 1471 .
AMA StyleManmeet Kaur, Manpreet Kaur, Dhanwinder Singh, Aderbal Oliveira, Vijayendra Garg, Virender Sharma. Synthesis of CaFe2O4-NGO Nanocomposite for Effective Removal of Heavy Metal Ion and Photocatalytic Degradation of Organic Pollutants. Nanomaterials. 2021; 11 (6):1471.
Chicago/Turabian StyleManmeet Kaur; Manpreet Kaur; Dhanwinder Singh; Aderbal Oliveira; Vijayendra Garg; Virender Sharma. 2021. "Synthesis of CaFe2O4-NGO Nanocomposite for Effective Removal of Heavy Metal Ion and Photocatalytic Degradation of Organic Pollutants." Nanomaterials 11, no. 6: 1471.
The effect of Lithium insertion in the crystal structure and magnetic properties of Barbosalite [Fe3(PO4)2(OH)2], a polymorph of iron hydroxyl phosphate synthesized from variable Fe precursor (Fe(II) and Fe(III)), have been investigated. Effect of distortion in the crystal structure of Barbosalite appeared with minimum lithium hydroxide (LiOH.H2O) concentration of 0.5 M as depicted from the XRD patterns. Further, appearance of fresh peaks from 2 M is well matched with the crystal structure of LiFePO4. Studies with Mössbauer spectroscopy and SQUID Magnetometer intriguingly reveals that Li intercalation in the barbosalite affects only Fe(III) sites whereas the Fe(II) sites remains unaffected till 2 M. However, further increase in the Li concentration leads to structural transformation and results in LiFePO4 phase. Comparative studies of the structural and magnetic properties, magnetic transition are also discussed.
N. Joseph Singh; L. Herojit Singh; S.S. Pati; J.A.H. Coaquira; A.C. Oliveira; Junhu Wang; V.K. Garg. Effect of Li insertion in the crystal structure and magnetism of barbosalite prepared using solvothermal method. Materials Chemistry and Physics 2019, 240, 122133 .
AMA StyleN. Joseph Singh, L. Herojit Singh, S.S. Pati, J.A.H. Coaquira, A.C. Oliveira, Junhu Wang, V.K. Garg. Effect of Li insertion in the crystal structure and magnetism of barbosalite prepared using solvothermal method. Materials Chemistry and Physics. 2019; 240 ():122133.
Chicago/Turabian StyleN. Joseph Singh; L. Herojit Singh; S.S. Pati; J.A.H. Coaquira; A.C. Oliveira; Junhu Wang; V.K. Garg. 2019. "Effect of Li insertion in the crystal structure and magnetism of barbosalite prepared using solvothermal method." Materials Chemistry and Physics 240, no. : 122133.
Thick freestanding iron-doped semi-insulating GaN layers were grown by Hydride Vapor Phase Epitaxy on GaN/sapphire templates. Iron doping was achieved by using Fe57-enriched Fe2O3 reduced to elemental Fe in-situ avoiding uptake of C from organometallic sources. The morphology and crystalline quality of the films show no evidence of degradation upon iron doping. Mössbauer and spin resonance experiments demonstrate that the Fe-impurity is in the isolated Fe3+ paramagnetic state and no Fe-precipitates are formed at the highest doping levels. Low temperature photoluminescence studies are consistent with full compensation of the shallow pervasive Si and O donors.
J.A. Freitas; J.C. Culbertson; E.R. Glaser; E. Richter; Markus Weyers; A.C. Oliveira; Vijayendra Garg. Efficient iron doping of HVPE GaN. Journal of Crystal Growth 2018, 500, 111 -116.
AMA StyleJ.A. Freitas, J.C. Culbertson, E.R. Glaser, E. Richter, Markus Weyers, A.C. Oliveira, Vijayendra Garg. Efficient iron doping of HVPE GaN. Journal of Crystal Growth. 2018; 500 ():111-116.
Chicago/Turabian StyleJ.A. Freitas; J.C. Culbertson; E.R. Glaser; E. Richter; Markus Weyers; A.C. Oliveira; Vijayendra Garg. 2018. "Efficient iron doping of HVPE GaN." Journal of Crystal Growth 500, no. : 111-116.
57Fe Mössbauer spectroscopy, XRD, and TEM were used to investigate the effect of mandelic- and salicylic acid coatings on the iron oxide nanoparticles. These two carboxylic acids have similar molecules size and stoichiometry, but different structure and acidity. Significant differences were observed between the Mössbauer spectra of samples coated with mandelic acid and salicylic acid. These results indicate that the occurrence of iron microenvironments in the mandelic- and salicylic acid-coated iron oxide nanoparticles is different. The results can be interpreted in terms of the influence of the acidity of carboxylic acids on the formation, core/shell structure, and oxidation of coated iron oxide nanocomposites.
Attila Lengyel; Gyula Tolnai; Zoltan Klencsar; Vijayendra Kumar Garg; Aderbal Carlos De Oliveira; L. Herojit Singh; Zoltán Homonnay; Roland Szalay; Peter Nemeth; Bálint Szabolcs; Mira Ristic; Svetozar Musić; Ernő Kuzmann. The effect of carboxylic acids on the oxidation of coated iron oxide nanoparticles. Journal of Nanoparticle Research 2018, 20, 137 .
AMA StyleAttila Lengyel, Gyula Tolnai, Zoltan Klencsar, Vijayendra Kumar Garg, Aderbal Carlos De Oliveira, L. Herojit Singh, Zoltán Homonnay, Roland Szalay, Peter Nemeth, Bálint Szabolcs, Mira Ristic, Svetozar Musić, Ernő Kuzmann. The effect of carboxylic acids on the oxidation of coated iron oxide nanoparticles. Journal of Nanoparticle Research. 2018; 20 (5):137.
Chicago/Turabian StyleAttila Lengyel; Gyula Tolnai; Zoltan Klencsar; Vijayendra Kumar Garg; Aderbal Carlos De Oliveira; L. Herojit Singh; Zoltán Homonnay; Roland Szalay; Peter Nemeth; Bálint Szabolcs; Mira Ristic; Svetozar Musić; Ernő Kuzmann. 2018. "The effect of carboxylic acids on the oxidation of coated iron oxide nanoparticles." Journal of Nanoparticle Research 20, no. 5: 137.
NiFe2O4 nanocrystalline samples were synthesized by the sol-gel method. The X-ray diffraction patterns of the as-synthesized samples (S- NiFe2O4) showed the formation of main spinel ferrite structure, with an average crystalline size of ∼50 nm. After a washing process with magnetic separation two sets of NiFe2O4 particles was observed, one with ∼36 nm and other with very small size (∼2–3 nm). X-ray photoelectron spectroscopy (XPS) indicated the presence of Fe3+ and Ni2+ ions on the sample surface. Mössbauer spectra were recorded at 77 K and room temperature and were least square fitted for two sextets which have been assigned to the iron ions occupying the two symmetry sites of the ferrite structure. Magnetic measurements are consistent with the magnetic moment of Ni2+ ions suggesting the formation of an ideal inverse spinel structure in the sample S-NiFe2O4. Moreover, after the washing process with magnetic separation (sample P- NiFe2O4), when the formation of extremely small particles was determined, the Mössbauer and magnetic measurements indicated the reorganization of Ni2+/Fe3+ ions in the tetragonal and octahedral sites of the spinel structure and some features related to thermal relaxations of the small particles are determined.
John Mantilla; Lizbet León Félix; M.A. Rodriguez; F.H. Aragon; P.C. Morais; Jose Coaquira; E. Kuzmann; A.C. de Oliveira; I. Gonzalez; W.A.A. Macedo; V.K. Garg. Washing effect on the structural and magnetic properties of NiFe 2 O 4 nanoparticles synthesized by chemical sol-gel method. Materials Chemistry and Physics 2018, 213, 295 -304.
AMA StyleJohn Mantilla, Lizbet León Félix, M.A. Rodriguez, F.H. Aragon, P.C. Morais, Jose Coaquira, E. Kuzmann, A.C. de Oliveira, I. Gonzalez, W.A.A. Macedo, V.K. Garg. Washing effect on the structural and magnetic properties of NiFe 2 O 4 nanoparticles synthesized by chemical sol-gel method. Materials Chemistry and Physics. 2018; 213 ():295-304.
Chicago/Turabian StyleJohn Mantilla; Lizbet León Félix; M.A. Rodriguez; F.H. Aragon; P.C. Morais; Jose Coaquira; E. Kuzmann; A.C. de Oliveira; I. Gonzalez; W.A.A. Macedo; V.K. Garg. 2018. "Washing effect on the structural and magnetic properties of NiFe 2 O 4 nanoparticles synthesized by chemical sol-gel method." Materials Chemistry and Physics 213, no. : 295-304.
We study the influence of dynamic capping of Fe3O4 nanoparticles with phosphate and oleic acid, on their structure, magnetic properties and thermal stability of magnetic nanoparticles. It is observed that the phosphate coating on iron oxide lowers the dipole–dipole interaction significantly, as compared to oleic acid capping. The Mössbauer results show that the spin canting order of oxidized shell and the mean hyperfine field values follow the order Fe0 (uncoated) > FeOA (oleic acid capped) > FP1 (phosphate capped). The uncoated Fe3O4 nanoparticle is non-stoichiometric in nature due to oxidation, whereas FP1 and FeOA are of the correct stoichiometry. Mössbauer and photoacoustic spectroscopic studies on air-annealed phosphate-coated magnetite nanoparticles confirm that the magnetic iron oxide phase is preserved up to 833 K and a complete conversion of Fe3O4 into the non-magnetic hematite phase occurs at 1173 K. The iron oxide air annealed at 833 K is found to have a shell of orthorhombic α-Fe2O3 over the magnetite core. However, in oleic acid-coated nanoparticles, the magnetic to non-magnetic phase transformation commences at 623 K and the conversion was complete at 823 K. The photoacoustic spectra of the air-annealed phosphate-coated Fe3O4 particles showed a flipping of the absorption intensity between 500−700 nm and 800−1000 nm, due to the conversion of Fe3O4 to γ-Fe2O3 at 923 and γ-Fe2O3 to α-Fe2O3 at 1173 K, respectively. The γ-Fe2O3 showed an intense absorption peak above 750 nm, whereas the α-Fe2O3 showed a peak broadening in the wavelength range of 600–700 nm, in addition to the strong peaks at a wavelength above 750 nm. This study suggests that the photoacoustic spectroscopy can distinguish clearly the three polymorphs of iron oxide i.e., Fe3O4, γ-Fe2O3 and α-Fe2O3. Our results confirm the ability of phosphate-capped iron oxide particles to retard the oxidation of Fe2+ contents during the crystal growth process.
T. Muthukumaran; Sudhanshu Pati; L. H. Singh; A. C. De Oliveira; Vijayendra Garg; John Philip. Comparison of magnetic properties and high-temperature phase stability of phosphate- and oleic acid-capped iron oxide nanoparticles. Applied Nanoscience 2018, 8, 593 -608.
AMA StyleT. Muthukumaran, Sudhanshu Pati, L. H. Singh, A. C. De Oliveira, Vijayendra Garg, John Philip. Comparison of magnetic properties and high-temperature phase stability of phosphate- and oleic acid-capped iron oxide nanoparticles. Applied Nanoscience. 2018; 8 (4):593-608.
Chicago/Turabian StyleT. Muthukumaran; Sudhanshu Pati; L. H. Singh; A. C. De Oliveira; Vijayendra Garg; John Philip. 2018. "Comparison of magnetic properties and high-temperature phase stability of phosphate- and oleic acid-capped iron oxide nanoparticles." Applied Nanoscience 8, no. 4: 593-608.
Nanoparticles of iron oxide play an important role on the field of nanotechnology and nanoscience presenting tremendous potential for various applications. Oleic acid has been shown to be a promising coating material, allowing to obtain monodisperse, uniform and stable nanoparticles. However, for certain applications which utilize the encapsulation of magnetic nanoparticles into polymer matrices it becomes necessary to use coating materials which exhibit functional groups in their structure capable of avoiding leaching problems. To this end, the present study aimed to develop magnetite nanoparticles coated with chemically modified oleic acid. The reactive functional group present in the fatty acid molecule can promote polymerization between the monomer species and the coating material with high encapsulation efficiency. The different steps of the reactions to obtain acrylated oleic acid were evaluated by Fourier transform infrared (FTIR) spectroscopy and 1H nuclear magnetic resonance spectroscopy. The coated nanoparticles were characterized by FTIR, thermogravimetric analysis, X-ray diffraction, transmission electron microscopy, Mössbauer spectroscopy, Raman spectroscopy and magnetization measurements. The coated nanoparticles showed high dispersibility with a uniform average size of 9.5 nm, saturation magnetization of 61.2 emu/g and superparamagnetic behavior, which make it a very promising for the formation of nanocomposites.
Weslany Silvério Neto; Gabriel Victor Simões Dutra; Alan Thyago Jensen; Olacir Alves Araújo; Vijayendra Garg; Aderbal Carlos de Oliveira; Leonardo Fonseca Valadares; Fernando Gomes de Souza; Fabricio Machado. Superparamagnetic nanoparticles stabilized with free-radical polymerizable oleic acid-based coating. Journal of Alloys and Compounds 2018, 739, 1025 -1036.
AMA StyleWeslany Silvério Neto, Gabriel Victor Simões Dutra, Alan Thyago Jensen, Olacir Alves Araújo, Vijayendra Garg, Aderbal Carlos de Oliveira, Leonardo Fonseca Valadares, Fernando Gomes de Souza, Fabricio Machado. Superparamagnetic nanoparticles stabilized with free-radical polymerizable oleic acid-based coating. Journal of Alloys and Compounds. 2018; 739 ():1025-1036.
Chicago/Turabian StyleWeslany Silvério Neto; Gabriel Victor Simões Dutra; Alan Thyago Jensen; Olacir Alves Araújo; Vijayendra Garg; Aderbal Carlos de Oliveira; Leonardo Fonseca Valadares; Fernando Gomes de Souza; Fabricio Machado. 2018. "Superparamagnetic nanoparticles stabilized with free-radical polymerizable oleic acid-based coating." Journal of Alloys and Compounds 739, no. : 1025-1036.
Iron-oxide nanoparticles were prepared by two ways of chemical methods when the coprecipitated nanomagnetites were functionalized by different (citric and mandelic) carboxylic acids. The colloid samples were characterized by 57Fe Mössbauer spectroscopy, electron microscopy, RAMAN spectroscopy and magnetization measurements. Considerable paramagnetic contributions are present in the 80 K Mössbauer spectra in both citric acid coated and mandelic acid coated nanomagnetites. The 5 K measurement revealed that the paramagnetic component appearing at 80 K can represent a superparamagnetic fraction due to the small particle size in the case of mandelic acid functionalized sample. However, in the case of citric acid functionalized nanomagnetite sample, the paramagnetic components occurring also in the 5 K spectra can be associated with components of precursors and of by-product phases.
A. Lengyel; V. K. Garg; A. C. De Oliveira; S. W. Da Silva; L. R. Guilherme; Z. Klencsár; Z. Homonnay; J. A. H. Coaquira; Gy. Tolnai; E. Kuzmann. Mössbauer spectroscopy control of the preparation of citric- and mandelic acid functionalized nanomagnetites. Hyperfine Interactions 2018, 239, 17 .
AMA StyleA. Lengyel, V. K. Garg, A. C. De Oliveira, S. W. Da Silva, L. R. Guilherme, Z. Klencsár, Z. Homonnay, J. A. H. Coaquira, Gy. Tolnai, E. Kuzmann. Mössbauer spectroscopy control of the preparation of citric- and mandelic acid functionalized nanomagnetites. Hyperfine Interactions. 2018; 239 (1):17.
Chicago/Turabian StyleA. Lengyel; V. K. Garg; A. C. De Oliveira; S. W. Da Silva; L. R. Guilherme; Z. Klencsár; Z. Homonnay; J. A. H. Coaquira; Gy. Tolnai; E. Kuzmann. 2018. "Mössbauer spectroscopy control of the preparation of citric- and mandelic acid functionalized nanomagnetites." Hyperfine Interactions 239, no. 1: 17.
We have prepared nano-structured In-doped (1 mol %) LiFePO4/C samples by sol–gel method followed by a selective high temperature (600 and 700 °C) annealing in a reducing environment of flowing Ar/H2 atmosphere. The crystal structure, particle size, morphology, and magnetic properties of nano-composites were characterized by X-ray diffraction (XRD), scanning electron microsopy (SEM), transmission electron microscopy (TEM), and 57Fe Mössbauer spectroscopy. The Rietveld refinement of XRD patterns of the nano-composites were indexed to the olivine crystal structure of LiFePO4 with space group Pnma, showing minor impurities of Fe2P and Li3PO4 due to decomposition of LiFePO4. We found that the doping of In in LiFePO4/C nanocomposites affects the amount of decomposed products, when compared to the un-doped ones treated under similar conditions. An optimum amount of Fe2P present in the In-doped samples enhances the electronic conductivity to achieve a much improved electrochemical performance. The galvanostatic charge/discharge curves show a significant improvement in the electrochemical performance of 700 °C annealed In-doped-LiFePO4/C sample with a discharge capacity of 142 mAh·g−1 at 1 C rate, better rate capability (~128 mAh·g−1 at 10 C rate, ~75% of the theoretical capacity) and excellent cyclic stability (96% retention after 250 cycles) compared to other samples. This enhancement in electrochemical performance is consistent with the results of our electrochemical impedance spectroscopy measurements showing decreased charge-transfer resistance and high exchange current density.
Ajay Kumar; Parisa Bashiri; Balaji P. Mandal; Kulwinder S. Dhindsa; Khadije Bazzi; Ambesh Dixit; Maryam Nazri; Zhixian Zhou; Vijayendra K. Garg; Aderbal C. Oliveira; Prem P. Vaishnava; Vaman M. Naik; Gholam-Abbas Nazri; Ratna Naik. Optimization of Electrochemical Performance of LiFePO4/C by Indium Doping and High Temperature Annealing. Inorganics 2017, 5, 67 .
AMA StyleAjay Kumar, Parisa Bashiri, Balaji P. Mandal, Kulwinder S. Dhindsa, Khadije Bazzi, Ambesh Dixit, Maryam Nazri, Zhixian Zhou, Vijayendra K. Garg, Aderbal C. Oliveira, Prem P. Vaishnava, Vaman M. Naik, Gholam-Abbas Nazri, Ratna Naik. Optimization of Electrochemical Performance of LiFePO4/C by Indium Doping and High Temperature Annealing. Inorganics. 2017; 5 (4):67.
Chicago/Turabian StyleAjay Kumar; Parisa Bashiri; Balaji P. Mandal; Kulwinder S. Dhindsa; Khadije Bazzi; Ambesh Dixit; Maryam Nazri; Zhixian Zhou; Vijayendra K. Garg; Aderbal C. Oliveira; Prem P. Vaishnava; Vaman M. Naik; Gholam-Abbas Nazri; Ratna Naik. 2017. "Optimization of Electrochemical Performance of LiFePO4/C by Indium Doping and High Temperature Annealing." Inorganics 5, no. 4: 67.
Composites of CoFe2O4 and ZnO ([email protected]) nanomaterials were synthesized using double stage co-precipitation. The structural properties have been investigated by x-ray diffraction which shows the presence of hexagonal ZnO and spinel CoFe2O4. Variation in lattice parameters, after annealing at elevated temperature, indicates the diffusion of cations from the ZnO to CoFe2O4 and vice versa. Magnetic properties were measured by Mössbauer spectroscopy and superconducting quantum interference device magnetometer. The transition from ferrimagnet to paramagnet at 973 K is due to the formation of ZnFe2O4. High quadrupole splitting values in Mössbauer spectra depict the presence of interstitial Co defects. The Co cations diffuse in the ZnO lattice in the course of annealing at 1273 K, forming CoxZn1−xO resulting in ferromagnetism.
L. Herojit Singh; Sudhanshu S. Pati; A. C. Oliveira; Vijayendra K Garg; Erno Kuzmann. Thermal-induced magnetic transition in [email protected] Journal of Applied Physics 2017, 122, 143901 .
AMA StyleL. Herojit Singh, Sudhanshu S. Pati, A. C. Oliveira, Vijayendra K Garg, Erno Kuzmann. Thermal-induced magnetic transition in [email protected] Journal of Applied Physics. 2017; 122 (14):143901.
Chicago/Turabian StyleL. Herojit Singh; Sudhanshu S. Pati; A. C. Oliveira; Vijayendra K Garg; Erno Kuzmann. 2017. "Thermal-induced magnetic transition in [email protected]" Journal of Applied Physics 122, no. 14: 143901.
N.C. Sena; T.J. Castro; V.K. Garg; A.C. Oliveira; P.C. Morais; S.W. da Silva. Gadolinium ferrite nanoparticles: Synthesis and morphological, structural and magnetic properties. Ceramics International 2017, 43, 4042 -4047.
AMA StyleN.C. Sena, T.J. Castro, V.K. Garg, A.C. Oliveira, P.C. Morais, S.W. da Silva. Gadolinium ferrite nanoparticles: Synthesis and morphological, structural and magnetic properties. Ceramics International. 2017; 43 (5):4042-4047.
Chicago/Turabian StyleN.C. Sena; T.J. Castro; V.K. Garg; A.C. Oliveira; P.C. Morais; S.W. da Silva. 2017. "Gadolinium ferrite nanoparticles: Synthesis and morphological, structural and magnetic properties." Ceramics International 43, no. 5: 4042-4047.
The effect of coating with nine different carboxylic acids (glycolic, propionic, lactic, malic, tartaric, citric, mandelic, caproic and caprylic) on nanostructured magnetite (D ~ 10 nm) was studied by Raman and photoacoustic, magnetic and 57Fe Mössbauer measurements. Mössbauer spectra of frozen suspensions showed dominantly magnetically split envelopes at lower temperatures, which were evaluated by hyperfine field distribution method. Mössbauer and Raman spectroscopy indicated similar variation of relative occurrence of magnetite and maghemite phases. These results are discussed on the basis of the hypothesis that different carboxylic acids can promote either the oxidation or reduction of iron oxide nanoparticles.
Sebastiao William da Silva; Luciana Rebelo Guilherme; Aderbal Oliveira; Vijayendra Garg; Pedro Augusto Matos Rodrigues; Jose Coaquira; Queila Da Silva Ferreira; Guilherme Henrique Ferreira de Melo; Attila Lengyel; Roland Szalay; Zoltán Homonnay; Zoltán Klencsár; Gyula Tolnai; Ernő Kuzmann. Mössbauer and Raman spectroscopic study of oxidation and reduction of iron oxide nanoparticles promoted by various carboxylic acid layers. Journal of Radioanalytical and Nuclear Chemistry 2017, 312, 111 -119.
AMA StyleSebastiao William da Silva, Luciana Rebelo Guilherme, Aderbal Oliveira, Vijayendra Garg, Pedro Augusto Matos Rodrigues, Jose Coaquira, Queila Da Silva Ferreira, Guilherme Henrique Ferreira de Melo, Attila Lengyel, Roland Szalay, Zoltán Homonnay, Zoltán Klencsár, Gyula Tolnai, Ernő Kuzmann. Mössbauer and Raman spectroscopic study of oxidation and reduction of iron oxide nanoparticles promoted by various carboxylic acid layers. Journal of Radioanalytical and Nuclear Chemistry. 2017; 312 (1):111-119.
Chicago/Turabian StyleSebastiao William da Silva; Luciana Rebelo Guilherme; Aderbal Oliveira; Vijayendra Garg; Pedro Augusto Matos Rodrigues; Jose Coaquira; Queila Da Silva Ferreira; Guilherme Henrique Ferreira de Melo; Attila Lengyel; Roland Szalay; Zoltán Homonnay; Zoltán Klencsár; Gyula Tolnai; Ernő Kuzmann. 2017. "Mössbauer and Raman spectroscopic study of oxidation and reduction of iron oxide nanoparticles promoted by various carboxylic acid layers." Journal of Radioanalytical and Nuclear Chemistry 312, no. 1: 111-119.
Apresentamos neste trabalho uma breve revis˜ao bibliogr´afica sobre a espectroscopia M¨ossbauer. Partindo do conceitos de ressonˆancia em diferentes contextos f´ısicos, discutimos o efeito M¨ossbauer e suas aplica¸c˜oes. Por fim, apresentamos de forma sucinta a estrutura f´ısica e os trabalhos desenvolvidos no Laborat´orio de Espectroscopia M¨ossbauer da Universidade de Bras´ılia.
Vijayendra K. Garg. Espectroscopia Mössbauer no Instituto de Física da Universidade de Brasília. e-Boletim da Física 2016, 5, 1 -9.
AMA StyleVijayendra K. Garg. Espectroscopia Mössbauer no Instituto de Física da Universidade de Brasília. e-Boletim da Física. 2016; 5 (4):1-9.
Chicago/Turabian StyleVijayendra K. Garg. 2016. "Espectroscopia Mössbauer no Instituto de Física da Universidade de Brasília." e-Boletim da Física 5, no. 4: 1-9.
Sudhanshu S. Pati; L. Herojit Singh; E.M. Guimarães; John Mantilla; J.A.H. Coaquira; A.C. Oliveira; Virender K. Sharma; Vijayendra K. Garg. Magnetic chitosan-functionalized [email protected] nanoparticles: Synthesis and characterization. Journal of Alloys and Compounds 2016, 684, 68 -74.
AMA StyleSudhanshu S. Pati, L. Herojit Singh, E.M. Guimarães, John Mantilla, J.A.H. Coaquira, A.C. Oliveira, Virender K. Sharma, Vijayendra K. Garg. Magnetic chitosan-functionalized [email protected] nanoparticles: Synthesis and characterization. Journal of Alloys and Compounds. 2016; 684 ():68-74.
Chicago/Turabian StyleSudhanshu S. Pati; L. Herojit Singh; E.M. Guimarães; John Mantilla; J.A.H. Coaquira; A.C. Oliveira; Virender K. Sharma; Vijayendra K. Garg. 2016. "Magnetic chitosan-functionalized [email protected] nanoparticles: Synthesis and characterization." Journal of Alloys and Compounds 684, no. : 68-74.
Highlights•Various gold species are identified in stabilized 1.3–4 nm nanoparticles.•Partial coverage of particles with thiol is suggested.•Partly irregular crystal structure of nanoparticles is evidenced. AbstractStabilized gold nanoparticles (Au NPs) were prepared with 4: 2.6 Au to buthyldithiol stoichiometry using modified Brust synthesis. The size of the particles falls into the 1.3–4 nm range in which the molecular cluster − metallic particle transition takes place. Stabilized particles were characterized by transmission electron microscopy (TEM/HRTEM). Moreover, numerous spectroscopic techniques like UV-Vis, infrared (FTIR), X-ray diffraction (XRD), Raman, photoacoustic and Mössbauer spectroscopies were also used for detailed structural identification of the functionalized Au NPs. The presence of Au-S bonds was proven by FTIR and Raman spectra. It was found that the distribution of covering thiol layer is uneven, therefore the presence of uncovered surface gold atoms can be assumed at the applied stoichiometry. In good coincidence, four types of gold species could be identified in the corresponding Mössbauer spectrum. They can be attributed to metallic gold in the core, to bare gold in the surface layer, to surface gold atoms attached to thiol, and finally, to gold atoms pulled out from the particle, located in S-Au-S bridges. Graphical abstract
Erno Kuzmann; E. Csapó; S. Stichleutner; V.K. Garg; A.C. De Oliveira; S.W. Da Silva; L.H. Sing; S.S. Pati; E.M. Guimaraes; A. Lengyel; I. Dékány; K. Lázár. Fine structure of gold nanoparticles stabilized by buthyldithiol: Species identified by Mössbauer spectroscopy. Colloids and Surfaces A: Physicochemical and Engineering Aspects 2016, 504, 260 -266.
AMA StyleErno Kuzmann, E. Csapó, S. Stichleutner, V.K. Garg, A.C. De Oliveira, S.W. Da Silva, L.H. Sing, S.S. Pati, E.M. Guimaraes, A. Lengyel, I. Dékány, K. Lázár. Fine structure of gold nanoparticles stabilized by buthyldithiol: Species identified by Mössbauer spectroscopy. Colloids and Surfaces A: Physicochemical and Engineering Aspects. 2016; 504 ():260-266.
Chicago/Turabian StyleErno Kuzmann; E. Csapó; S. Stichleutner; V.K. Garg; A.C. De Oliveira; S.W. Da Silva; L.H. Sing; S.S. Pati; E.M. Guimaraes; A. Lengyel; I. Dékány; K. Lázár. 2016. "Fine structure of gold nanoparticles stabilized by buthyldithiol: Species identified by Mössbauer spectroscopy." Colloids and Surfaces A: Physicochemical and Engineering Aspects 504, no. : 260-266.
57Fe Mössbauer spectroscopy and XRD have successfully been applied to show the incorporation of Fe ion into the interlayer space of montmorillonite via treatment with FeCl 3 in acetone. The 78K 57Fe Mössbauer spectra of montmorillonite samples reflected magnetically split spectrum part indicating the intercalation of iron into the interlayer of montmorillonite via the treatment with FeCl 3+acetone and washed with water until the initial pH=2.3 increased to pH=4.14. It was found that the occurrence of intercalated iron in the form of oxide-oxihydroxide in montmorillonite increases with the pH. Intercalation was confirmed by the gradual increase in the basal spacing d 001 with pH.
Erno Kuzmann; V. K. Garg; H. Singh; A. C. De Oliveira; S. S. Pati; Z. Homonnay; M. Rudolf; Á. M. Molnár; E. M. Kovács; E. Baranyai; S. Kubuki; N. M. Nagy; J. Kónya. Mössbauer study of pH dependence of iron-intercalation in montmorillonite. Hyperfine Interactions 2016, 237, 106 .
AMA StyleErno Kuzmann, V. K. Garg, H. Singh, A. C. De Oliveira, S. S. Pati, Z. Homonnay, M. Rudolf, Á. M. Molnár, E. M. Kovács, E. Baranyai, S. Kubuki, N. M. Nagy, J. Kónya. Mössbauer study of pH dependence of iron-intercalation in montmorillonite. Hyperfine Interactions. 2016; 237 (1):106.
Chicago/Turabian StyleErno Kuzmann; V. K. Garg; H. Singh; A. C. De Oliveira; S. S. Pati; Z. Homonnay; M. Rudolf; Á. M. Molnár; E. M. Kovács; E. Baranyai; S. Kubuki; N. M. Nagy; J. Kónya. 2016. "Mössbauer study of pH dependence of iron-intercalation in montmorillonite." Hyperfine Interactions 237, no. 1: 106.
We have studied LiFePO4/C nanocomposites prepared by sol-gel method using lauric acid as a surfactant and calcined at different temperatures between 600 and 900 °C. In addition to the major LiFePO4 phase, all the samples show a varying amount of in situ Fe2P impurity phase characterized by x-ray diffraction, magnetic measurements, and Mössbauer spectroscopy. The amount of Fe2P impurity phase increases with increasing calcination temperature. Of all the samples studied, the LiFePO4/C sample calcined at 700 °C which contains ∼15 wt% Fe2P shows the least charge transfer resistance and a better electrochemical performance with a discharge capacity of 136 mA h g−1 at a rate of 1 C, 121 mA h g−1 at 10 C (∼70 % of the theoretical capacity of LiFePO4), and excellent cycleability. Although further increase in the amount of Fe2P reduces the overall capacity, frequency-dependent Warburg impedance analyses show that all samples calcined at temperatures ≥700 °C have an order of magnitude higher Li+ diffusion coefficient (∼1.3 × 10−13 cm2 s−1) compared to the one calcined at 600 °C, as well as the values reported in literature. This work suggests that controlling the reduction environment and the temperature during the synthesis process can be used to optimize the amount of conducting Fe2P for obtaining the best capacity for the high power batteries.
K. S. Dhindsa; Amit Kumar; G. A. Nazri; V. M. Naik; V. K. Garg; A. C. Oliveira; P. P. Vaishnava; Zhixian Zhou; R. Naik. Enhanced electrochemical performance of LiFePO4/C nanocomposites due to in situ formation of Fe2P impurities. Journal of Solid State Electrochemistry 2016, 20, 2275 -2282.
AMA StyleK. S. Dhindsa, Amit Kumar, G. A. Nazri, V. M. Naik, V. K. Garg, A. C. Oliveira, P. P. Vaishnava, Zhixian Zhou, R. Naik. Enhanced electrochemical performance of LiFePO4/C nanocomposites due to in situ formation of Fe2P impurities. Journal of Solid State Electrochemistry. 2016; 20 (8):2275-2282.
Chicago/Turabian StyleK. S. Dhindsa; Amit Kumar; G. A. Nazri; V. M. Naik; V. K. Garg; A. C. Oliveira; P. P. Vaishnava; Zhixian Zhou; R. Naik. 2016. "Enhanced electrochemical performance of LiFePO4/C nanocomposites due to in situ formation of Fe2P impurities." Journal of Solid State Electrochemistry 20, no. 8: 2275-2282.
We have studied the stoichiometry of magnetite nanoparticles using three spectroscopic techniques: Mössbauer, photoacoustic and ferromagnetic resonance (FMR). By varying the weight ratio of the Fe precursor to the reducing agent (sodium acetate) and a post-synthesis annealing, we were able to synthesize samples with different amounts of Fe vacancies, from stoichiometric Fe3O4 to γ-Fe2O3. By synthesizing magnetite in the presence of zeolite we obtained nanoparticles within the 3–10 nm diameter range. The spectroscopic results show that there is a correlation between the amount of Fe vacancies and (i) the optical absorption and (ii) the g-values from the Electron paramagnetic resonance EPR spectra of the nanoparticles.
L. Herojit Singh; S.S. Pati; Edi M. Guimarães; Pedro A. M. Rodrigues; Aderbal C. Oliveira; V.K. Garg. Synthesis, structure, morphology and stoichiometry characterization of cluster and nano magnetite. Materials Chemistry and Physics 2016, 178, 182 -189.
AMA StyleL. Herojit Singh, S.S. Pati, Edi M. Guimarães, Pedro A. M. Rodrigues, Aderbal C. Oliveira, V.K. Garg. Synthesis, structure, morphology and stoichiometry characterization of cluster and nano magnetite. Materials Chemistry and Physics. 2016; 178 ():182-189.
Chicago/Turabian StyleL. Herojit Singh; S.S. Pati; Edi M. Guimarães; Pedro A. M. Rodrigues; Aderbal C. Oliveira; V.K. Garg. 2016. "Synthesis, structure, morphology and stoichiometry characterization of cluster and nano magnetite." Materials Chemistry and Physics 178, no. : 182-189.
We report the hydrothermal synthesis and structure of FexCo1−x alloy nanoparticles with considerable stability against oxidation under ambient atmosphere. Powder X-ray diffractometry (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), inductively coupled plasma mass spectrometry (ICP-MS), 57Fe Mössbauer spectroscopy and magnetization measurements are applied to characterize the composition, morphology, crystal structure, atomic order and magnetic properties of the nanoparticles. As-prepared samples are composed mainly of the bcc FexCo1−x alloy phase. TEM images of heat-treated samples confirm the nanoparticle nature of the original alloys. A consistent analysis of the experimental results leads to x ≈ 53% and x ≈ 62% Fe atomic ratio respectively in two analogous alloy samples, and suggests that the atomic level structure of the nanoparticles corresponds to that of a fully disordered (A2-type) alloy phase. Exploration of the effect of cobalt on the 57Fe hyperfine parameters of iron microenvironments suggests that in these alloys the electronic state of Fe atoms is perturbed equally and in an additive manner by atoms in their first two coordination spheres.
Z. Klencsár; P. Németh; Z. Sándor; T. Horváth; István Sajó; S. Mészáros; J. Mantilla; Jose Coaquira; Vijayendra Garg; Erno Kuzmann; Gy. Tolnai. Structure and magnetism of Fe–Co alloy nanoparticles. Journal of Alloys and Compounds 2016, 674, 153 -161.
AMA StyleZ. Klencsár, P. Németh, Z. Sándor, T. Horváth, István Sajó, S. Mészáros, J. Mantilla, Jose Coaquira, Vijayendra Garg, Erno Kuzmann, Gy. Tolnai. Structure and magnetism of Fe–Co alloy nanoparticles. Journal of Alloys and Compounds. 2016; 674 ():153-161.
Chicago/Turabian StyleZ. Klencsár; P. Németh; Z. Sándor; T. Horváth; István Sajó; S. Mészáros; J. Mantilla; Jose Coaquira; Vijayendra Garg; Erno Kuzmann; Gy. Tolnai. 2016. "Structure and magnetism of Fe–Co alloy nanoparticles." Journal of Alloys and Compounds 674, no. : 153-161.
Novel montmorillonites were prepared by the exchange of the interlayer cations with a series of rare earth cations (La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, and Er) and characterized by XRD, XRF, SEM, chemical analysis and 57Fe Mössbauer spectroscopy. An unexpected magnetically split component, assigned to iron being in the interlayer space, was observed in the Mössbauer spectra at 78K in some rare earth cation exchanged montmorillonite. This paper is the initial report about this observation. The transition of iron from the octahedral site to the interlayer and possible incorporation of rare earths in sites different from those which are in the interlayer space was concluded.
E. Kuzmann; L. H. Singh; Vijayendra Garg; Aderbal Oliveira; E. M. Kovács; Á. M. Molnár; Z. Homonnay; P. Kónya; N. M. Nagy; J. Kónya. Mössbauer study of the effect of rare earth substitution into montmorillonite. Hyperfine Interactions 2016, 237, 1 -8.
AMA StyleE. Kuzmann, L. H. Singh, Vijayendra Garg, Aderbal Oliveira, E. M. Kovács, Á. M. Molnár, Z. Homonnay, P. Kónya, N. M. Nagy, J. Kónya. Mössbauer study of the effect of rare earth substitution into montmorillonite. Hyperfine Interactions. 2016; 237 (1):1-8.
Chicago/Turabian StyleE. Kuzmann; L. H. Singh; Vijayendra Garg; Aderbal Oliveira; E. M. Kovács; Á. M. Molnár; Z. Homonnay; P. Kónya; N. M. Nagy; J. Kónya. 2016. "Mössbauer study of the effect of rare earth substitution into montmorillonite." Hyperfine Interactions 237, no. 1: 1-8.