Stability of citrate-coated magnetite and cobalt-ferrite nanoparticles under laser irradiation: A raman spectroscopy investigation

Silva, S.W. da; Melo, T.F.O.; Soler, Maria A. G.; Lima, E.C.D.; Silva, M.F. da; Morais, P.C.

doi:10.1109/tmag.2003.815540

Cited by 70 publications

(35 citation statements)

References 8 publications

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“…Magnetite has five typical Raman bands: two A 1g and three E g . 40 The labelled Raman peaks 384 cm À1 and 588 cm À1 can be ascribed as two E g modes 40 while the intense peak observed at 1278 cm À1 is assigned to two-magnon scattering of hematite present due to partial oxidation of magnetite. 41 In addition to them, no Raman peaks from any typical surfactant molecules are observed, indicating the high purity of the prepared substrate.…”

Section: Results and Discusionmentioning

confidence: 99%

Maximizing surface-enhanced Raman scattering sensitivity of surfactant-free Ag-Fe3O4 nanocomposites through optimization of silver nanoparticle density and magnetic self-assembly

Bao

Lei

2013

Journal of Applied Physics

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Magnetic composite nanomaterials consisting of more than two functional constituents have been attracting much research interests due to the realization of multiple functionalities in a single entity. In particular, integration of ferromagnetic oxides and noble metal nanoparticles (NPs) in composites results in simultaneous magnetic activity and optical response where the optical property of the whole system could be modulated by application of an external magnetic field. In this work, we prepared Ag NPs-coated Fe 3 O 4 microspheres as a novel surfactant-free surfaceenhanced Raman scattering (SERS) substrate through a solid-phase thermal decomposition reaction. The SERS sensitivity of the fabricated nanocomposites is maximized by adjusting the size and density of Ag NPs supported on the Fe 3 O 4 microspheres and further increased by magneticfield-directed self-assembly of the composite substrates, with both effects attributed to the efficient generation of plasmonic near-field "hot" spots. At the optimal conditions, the prepared substrate is capable of detecting rhodamine 6G molecules at a concentration down to 10 À12 M, thus demonstrating the great potential of using bifunctional nanocomposites as an excellent candidate for ultra-high sensitive Raman spectroscopy and biosensors. We also reveal the underlying mechanisms responsible for the observed SERS enhancements through full-wave numerical simulations. V C 2013 AIP Publishing LLC. [http://dx

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Section: Results and Discusionmentioning

confidence: 99%

Maximizing surface-enhanced Raman scattering sensitivity of surfactant-free Ag-Fe3O4 nanocomposites through optimization of silver nanoparticle density and magnetic self-assembly

Bao

Lei

2013

Journal of Applied Physics

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“…Contributions to Raman spectroscopy investigations of nanosized iron oxides have already been reported, with some special emphasis on the works of da Faria et al [9] and Shebanova and Lazor [10]. Some ferrofluid investigations involving this vibrational spectroscopy have also been made, where the preparative techniques yield either dried [11], precipitated [12], or frozen [13] samples to be measured. In our investigations, we used a simple procedure to probe the state of the magnetic core in liquid surrounding at normal conditions.…”

Section: Introductionmentioning

confidence: 99%

Raman spectroscopy investigation of magnetite nanoparticles in ferrofluids

Slavov

Abrashev

Merodiiska

et al. 2010

Journal of Magnetism and Magnetic Materials

218

107

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a b s t r a c tRaman spectroscopy is used to investigate magnetite nanoparticles dispersed in two types of bcyclodextrin suspensions. An approach is presented for characterization of the magnetic core in liquid surrounding at room temperature and atmospheric pressure. The effect of elevating laser power on the structural stability and chemical composition of magnetite in the ferrofluids is discussed. The data are compared with data from dry by-products from the fluids. Powder samples undergo total phase transition from magnetite to hematite at laser power of 1.95 mW. The same nanoparticles in the fluid undergo transformation at 9 mW, but no hematite positions appear throughout that investigation. The Raman spectra revealed that the main phase of the magnetic core in the fluids is magnetite. That is indicated by a strong and non-diminishing in intensity peak at 670 cm. A second phase is present at the nanoparticle's surface with Raman spectroscopy unveiling maghemite-like and small fractions of goethite-like structures. The Fourier transform infrared spectroscopy investigations confirm deviations in the surface structure and also point to the fact that the oxidation process starts at an early stage after formation of the nanoparticles. The analyses of the infrared data also show that b-cyclodextrin molecules retain their cyclic character and the coating does not affect the oxidation process once the particles are evicted from the fluids. A Mössbauer spectroscopy measurement on a ferrofluidic sample is also presented.

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“…Several groups have tried to use Raman spectroscopy to investigate the chemical structure of magnetic nanoparticles and the majority of the work was done using water based magnetic fluids [9][10][11][12][13][14][15][16][17][18][19][20]. However, Raman scattering is a very weak process, with molecular cross sections ranging from 10 À29 to 10 À32 cm 2 [21].…”

Section: Introductionmentioning

confidence: 99%

“…In this sense, the adsorption of methylene blue [12] and tetrasulfonated zinc phthalocyanine [17] on maghemite surfaces was characterized by resonance Raman scattering.…”

Section: Introductionmentioning

confidence: 99%

Surface-enhanced Raman spectra of magnetic nanoparticles adsorbed on a silver electrode

Jacintho

Cório

Rubim

2007

Journal of Electroanalytical Chemistry

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Stability of citrate-coated magnetite and cobalt-ferrite nanoparticles under laser irradiation: A raman spectroscopy investigation

Cited by 70 publications

References 8 publications

Maximizing surface-enhanced Raman scattering sensitivity of surfactant-free Ag-Fe3O4 nanocomposites through optimization of silver nanoparticle density and magnetic self-assembly

Maximizing surface-enhanced Raman scattering sensitivity of surfactant-free Ag-Fe3O4 nanocomposites through optimization of silver nanoparticle density and magnetic self-assembly

Raman spectroscopy investigation of magnetite nanoparticles in ferrofluids

Surface-enhanced Raman spectra of magnetic nanoparticles adsorbed on a silver electrode

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