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Direct synthesis of ultrasmall and stable magnetite nanoparticles coated with one single carbon layer for sensitive surface-enhanced Raman scattering
摘要： Ultrasmall spherical magnetite nanoparticles (Fe3O4 NPs) coated with one single carbon layer (Fe3O4@1C NPs) were directly synthesized by a simple, fast one-step hydrothermal reaction at low temperature (200℃). The as-synthesized Fe3O4@1C NPs were easily separated and purified from the resultant mixture, without the need for any additional energy input and chemicals. The as-purified Fe3O4@1C NPs not only displayed typical superparamagnetic behavior but also exhibited quite good long-term stability after being exposed to the open air under the room conditions for more than 2 months. Importantly, the long-term stored Fe3O4@1C NPs exhibited a highly sensitive surface-enhanced Raman spectroscopy (SERS) response toward Rhodamine-b (RdB) molecules with low concentration. The multifunctional and recyclable Fe3O4@1C NPs presented a prospective application for the selective enrichment and sensitive SERS detection of chemical and biomolecular assays.
关键词： coated with one single carbon layer (Fe3O4@1C NPs),Dehydration reaction,Saturation magnetization,Long-term stability,Magnetite nanoparticles (Fe3O4 NPs)
更新于2025-11-14 17:03:37
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Magnetite-Supported Gold Nanostars for the Uptake and SERS Detection of Tetracycline
摘要： Magnetite nanoparticles (MNPs) decorated with gold nanostars (AuNSs) have been prepared by using a seed growth method without the addition of surfactants or colloidal stabilizers. The hybrid nanomaterials were investigated as adsorbents for the uptake of tetracycline (TC) from aqueous solutions and subsequent detection using surface-enhanced Raman scattering (SERS). Several parameters were investigated in order to optimize the performance of these hybrid platforms on the uptake and SERS detection of TC, including variable pH values and the effect of contact time on the removal of TC. The spatial distribution of TC and AuNS on the hybrid composites was accomplished by coupling SERS analysis with Raman imaging studies, allowing also for the determination of the detection limit for TC when dissolved in ultrapure water (10 nM) and in more complex aqueous matrices (1 μM). Attempts were also made to investigate the adsorption modes of the TC molecules at the surface of the metal NPs by taking into account the enhancement of the Raman bands in these different matrices.
关键词： SERS,antibiotics,magnetite nanoparticles,Au nanostars,water pollutants
更新于2025-09-23 15:23:52
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Light scattering from the critical modes of the Verwey transition in magnetite
摘要： We present inelastic light scattering data on a single crystal of magnetite (Fe3O4) across the Verwey transition. We identify anomalies of the lattice vibrations that originate from strong coupling to electronic excitations. We reveal spectroscopic signatures of diffusive modes in the electronic contribution to the Raman response function. We thereby provide information on the critical dynamics and the hierarchy of the structural and electronic modes in the mechanism of the Verwey transition.
关键词： Raman spectroscopy,Verwey transition,critical dynamics,inelastic light scattering,magnetite
更新于2025-09-23 15:21:21
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Laser Optoacoustic Method for Measurement of Light Extinction Coefficient and Investigation of Its Spatial Distribution in Colloidal Media
摘要： In the present work, the method which allows investigating the spatial distribution of light extinction coefficient in colloidal media is experimentally realized. The proposed method is based on the dependence of temporal profiles of excited OA-signals on the absorption and extinction coefficients of the studied medium. Water-based and kerosene-based magnetic fluids with volume content of magnetite particles in the range 0.35–3.5 % were studied as an example of the medium with spatially non-uniform optical properties. The capability of the reconstruction of the one-dimensional spatial distribution for the light extinction coefficient in the investigated media is demonstrated. It was shown that the relative change of the extinction coefficient with depth depends on volume concentration of magnetite particles, type of acoustical boundary and properties of carrier liquids. In the case of acoustical rigid boundary of magnetic fluid, an additional induced anisotropy occurs, which leads to increasing of the light extinction coefficient with depth in comparison with acoustical free boundary of fluid.
关键词： Laser optoacoustic method,Concentration,Magnetite particles,Thermo-optical excitation,Magnetic fluids,Structural inhomogeneities,Light extinction,Colloidal medium
更新于2025-09-23 15:21:01
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Spectroscopic and Microscopic Analyses of Fe3O4/Au Nanoparticles Obtained by Laser Ablation in Water
摘要： Magneto-plasmonic nanoparticles constituted of gold and iron oxide were obtained in an aqueous environment by laser ablation of iron and gold targets in two successive steps. Gold nanoparticles are embedded in a mucilaginous matrix of iron oxide, which was identified as magnetite by both microscopic and spectroscopic analyses. The plasmonic properties of the obtained colloids, as well as their adsorption capability, were tested by surface-enhanced Raman scattering (SERS) spectroscopy using 2,2'-bipyridine as a probe molecule. DFT calculations allowed for obtaining information on the adsorption of the ligand molecules that strongly interact with positively charged surface active sites of the gold nanoparticles, thus providing efficient SERS enhancement. The presence of iron oxide gives the bimetallic colloid new possibilities of adsorption in addition to those inherent to gold nanoparticles, especially regarding organic pollutants and heavy metals, allowing to remove them from the aqueous environment by applying a magnetic field. Moreover, these nanoparticles, thanks to their low toxicity, are potentially useful not only in the field of sensors, but also for biomedical applications.
关键词： SERS,magnetite,gold,2,2'-bipyridine,laser ablation
更新于2025-09-19 17:13:59
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EXPRESS: A Study of the Surface of Fe <sub/>3</sub> O <sub/>4</sub> @SiO <sub/>2</sub> Nanoparticles Functionalized with Different Groups Using a Photoacoustic Infrared Spectroscopic Method
摘要： A permanent development of hybrid materials based on the highly absorptive or opaque materials has prompted a need of analytical tools, which are able to overcome obstacles connected with their physicochemical features. Iron oxide (II, III) (Fe3O4) nanoparticles gained a huge attention as supporters, as they are not only easily accessible using various synthetic approaches, but they also exhibit homogeneity and paramagnetic properties, which make them easily separable materials. Nevertheless, the classic infrared spectroscopic studies might meet several problems with characterization of such systems. Therefore, infrared spectroscopy in photoacoustic mode using Fourier transform infrared–photoacoustic infrared spectroscopy (FT-IR PAS) can be an extremely sensitive and exact analytical tool for investigation of the magnetite-based hybrid materials surface. Herein, we present a synthesis of Fe3O4 nanoparticles using co-precipitation method with their subsequent encapsulation within silica matrix decorated with different silanes containing various terminal functional groups. The proper syntheses of core/shell structures were confirmed using the FT-IR PAS method. Each spectrum exhibited specific bands corresponding to vibrations of magnetite particles, silica lattice and particular surface functional groups, which strictly indicated successful grafting of silanes onto Fe3O4 surface.
关键词： PAS,Magnetite nanoparticles,Fourier transform infrared,core/shell structures,surface analysis,photoacoustic infrared spectroscopy,FT-IR PAS,FT-IR
更新于2025-09-19 17:13:59
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Epitaxial Fe3O4 Films Grown on R-Plane Sapphire by Pulsed Laser Deposition
摘要： We have studied the influence of growth temperature and molecular oxygen pressure on the properties of thin (≤180 nm) epitaxial magnetite (Fe3O4) (001) films grown by pulsed laser deposition on R-plane single-crystal sapphire (Al2O3 ( 012)) with and without MgO seed layer. The electrical, morphological, and structural characteristics of the films have been investigated as functions of growth conditions. Fe3O4 has been shown to have a stable growth plateau at pressures in the range (4–9) × 10–5 Torr. The properties of the epitaxial Fe3O4 films grown on a MgO seed layer (5 nm thick) approach those of magnetite films grown on single-crystal MgO substrates and are superior to those of films grown on pure R-plane sapphire. The best electrical characteristic of the films and the corresponding crystal structure can be obtained at elevated growth temperatures, whereas reduced growth temperatures minimize the roughness of their surface and maximize its homogeneity. These conditions can be reconciled by high-temperature high-vacuum annealing of magnetite films grown at reduced temperatures.
关键词： epitaxial growth,atomic force microscopy,magnetite,thin films
更新于2025-09-19 17:13:59
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Laser synthesis of magnetite-partially reduced graphene oxide nanocomposites for arsenate removal from water
摘要： Herein, we report the development of a facile process for the synthesis of magnetite-partially reduced graphene oxide (Mag-PRGO) without the use of chemical reducing agents or solvents for the efficient removal of arsenate As(V) ions from contaminated water. The Mag-PRGO is synthesized using the laser vaporization-controlled condensation method where a compressed target consisting of metallic iron (Fe) powder and solid graphene oxide (GO) is laser vaporized in an O2–He atmosphere resulting in the simultaneous oxidation of the Fe nanoparticles and the partial reduction of the GO to form the Mag-PRGO nanocomposite where the magnetic Fe3O4 nanoparticles are anchored to the surface of the PRGO nanosheets. FTIR, Raman, XPS, XRD, TEM, and SEM confirm the successful attachment of the magnetic Fe3O4 nanoparticles to the PRGO nanosheets. The Mag-PRGO (50 wt% Fe) adsorbent shows exceptional selectivity for the extraction of As(V) ions with a capacity of 132 mg/g with no leaching of Fe ions into the solution, placing it among the best carbon-based materials for the efficient removal of As(V) from aqueous solutions. The Mag-PRGO displays a 100% removal of As(V) at concentrations up to 100 ppm with 98% and 100% removal within 15 min and 30 min, respectively, at 50 ppm concentration. The excellent agreement of the experimental sorption isotherms with the Langmuir model suggests a monolayer adsorption behavior. The mechanism of As(V) removal is based on surface complexation between the protonated hydroxyl groups on the surface of Mag-PRGO and the monobasic and dibasic arsenate anions forming (Fe–O–As) bonds as confirmed by FTIR and XPS. The Mag-PRGO is easily regenerated with the desorption of the As(V) ions reaching 99% from their maximum sorption capacities using NaOH. The efficient magnetic separation and high chemical stability of Mag-PRGO are demonstrated over six adsorption–desorption cycles of As(V). The Mag-PRGO is proposed as an excellent remediation adsorbent for the extraction of As(V) from contaminated water.
关键词： Magnetite-partially reduced graphene oxide,Arsenate removal,Water remediation,Adsorption,Laser vaporization-controlled condensation
更新于2025-09-16 10:30:52
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Investigation of nitrogen and iron co-doped TiO2 films synthesized in N2/CH4 via pulsed laser deposition technique
摘要： Nitrogen and iron ions co-doped titania films have been synthesized by PLD technique in nitrogen/methane (N2/CH4) (5:1) media at 1 mbar. Most of the samples are XRD amorphous but a certain amount of crystalline rutile is detected by Raman measurements. The presence of rutile phase only and its low crystallinity degree can be caused by nitrogen doping of oxide matrix. The most intensive VIS absorption and the lowest band gap values are observed for 5% Fe2O3 or Fe3O4 titania films that are supported by the highest nitrogen amount on the surface. The strongest photocatalysts in process of dichromate reduction under either UV or VIS irradiation are shown to be the films obtained from 5% iron oxide in titania target and synthesized at 550 °C as a result of optimal content of Ti–N and Ti–O–Fe structural fragments as revealed by XPS. The presence of Fe3+ and Fe2+ surrounded by oxygen as well as Fe–N bonds is confirmed by XPS data.
关键词： Pulsed laser deposition,Magnetite,Photocatalysis,Hematite,Titania,Nitrogen doping
更新于2025-09-16 10:30:52
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Wide-band enhancement of the transverse magneto-optical Kerr effect in magnetite-based plasmonic crystals
摘要： The transverse magneto-optical Kerr effect (TMOKE) in magnetite-based magnetoplasmonic crystals is studied experimentally and theoretically. We analyze angle-resolved TMOKE spectra from two types of structures where noble metallic stripes are incorporated inside a thin magnetite film or located on top of a homogeneous film. A multiple-wide-band enhancement of the TMOKE signal in transmission is demonstrated. The complex dielectric permittivity and gyration are experimentally determined using the ellipsometry technique as well as Faraday rotation and ellipticity measurements. The obtained parameters are used in rigorous coupled-wave analysis (RCWA) calculations for studying the optical resonances. Our RCWA calculations of transmittance and TMOKE are in good agreement with the experimental data. The role of guiding and plasmonic modes in the TMOKE enhancement is revealed. We demonstrate that the TMOKE provides rich information about the studied optical resonances.
关键词： transverse magneto-optical Kerr effect,ellipticity measurements,gyration,magnetoplasmonic crystals,Faraday rotation,dielectric permittivity,optical resonances,RCWA,magnetite,TMOKE
更新于2025-09-12 10:27:22