Colloidal Anisotropic ZnO–Fe@FexOy Nanoarchitectures with Interface-Mediated Exchange-Bias and Band-Edge Ultraviolet Fluorescence

Κωστοπούλου, Αθανασία; Thétiot, Franck; Tsiaoussis, I.; Androulidaki, M.; Cozzoli, P. Davide; Lappas, Alexandros

doi:10.1021/cm3008182

Cited by 28 publications

(24 citation statements)

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“…In this endeavor, solution-chemistry methods are widely used to develop size-controlled [18] and shape-controlled [19] ferrite-based nanocrystals and to facilitate their interfacial connectivity on a nanoscale motif, e.g., Fe@Fe 3−δ O 4 [20], CoO@CoFe 2 O 4 [21], FePt@MFe 2 O 4 (M ¼ Mn, Fe, Co, Zn) [22], etc. Within these systems, unforeseen magnetic properties are occasionally reported [23][24][25][26], especially when thermodynamically metastable phases such as wüstite [27] or novel interfaces are introduced during the nanoscale particle nucleation and growth.…”

Section: Introductionmentioning

confidence: 99%

Vacancy-Driven Noncubic Local Structure and Magnetic Anisotropy Tailoring in FexO−Fe3−δO

et al. 2019

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In contrast to bulk materials, nanoscale crystal growth is critically influenced by size-and shape-dependent properties. However, it is challenging to decipher how stoichiometry, in the realm of mixed-valence elements, can act to control physical properties, especially when complex bonding is implicated by short and long-range ordering of structural defects. Here, solution-grown iron-oxide nanocrystals (NCs) of the pilot wüstite system are found to convert into iron-deficient rock-salt and ferro-spinel sub-domains, but attain a surprising tetragonally distorted local structure. Cationic vacancies within chemically uniform NCs are portrayed as the parameter to tweak the underlying properties. These lattice imperfections are shown to produce local exchange-anisotropy fields that reinforce the nanoparticles' magnetization and overcome the influence of finite-size effects. The concept of atomic-scale defect control in subcritical size NCs, aspires to become a pathway to tailor-made properties with improved performance for hyperthermia heating over defect-free NCs. 5 Results 1 Structural insights Single-particle local structureFour nanoparticle samples were made available for this study, with specimen of spherical shape, entailing diameters of 8.1 ± 0.6 nm and 15.4 ± 1.3 nm and of cubic shape, obtaining edge-lengths of 12.3 ± 0.7 nm and 17.7 ± 1.6 nm ( Fig. S1). Henceforth, these are called S8, S15, C12 and C18, where 'S' stands for spherical and 'C' for cubic morphologies. Moreover, high-resolution transmission electron microscopy (HRTEM) ( Fig. 2a-d) suggests that the smaller S8 and C12 NPs entail a domain of a single-phase material, but the bimodal contrast in the larger S15 and C18 points that above a particle size of 12 nm two nanodomains are attained. The coexistence of dark and light contrast features in the S15 and C18 could be justified assuming that two chemical phases, of varying electron diffracting power, share the same nanoparticle volume. Crystallographic image processing by Fast Fourier transform (FFT) analysis of the relevant HRTEM images results in their corresponding (spot) electron diffraction patterns ( Fig. 2e-h). The unequivocal indexing of reflections in the S8 and C12 specimen may suggest that these adopt the magnetite type of phase ( Fig. 2e, f). On the other hand, a similar conclusion cannot be made after the evaluation of the FFT patterns of the apparently bimodal contrast S15 and C18 specimen as the cubic spinel and rock salt reflections (Fig. 2g, h) appear to be resolution limited. The behavior appears in line with the tendency of bulk wüstite for oxidative conversion, [28], [42] and infers a process analogous to its elimination from 23 nm core@shell FexO@Fe3-δO4 nanoparticles. [25] The long and short-range modulations of the selected (hkl) atomic planes could become more easily isolated with direct space images derived from the inverse FFT synthesis of chosen families of reflections. We find that the (400) (or (200) for the core@shell S15 and C18 NPs) family generates perfect atomic...

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Section: Introductionmentioning

confidence: 99%

Vacancy-Driven Noncubic Local Structure and Magnetic Anisotropy Tailoring in FexO−Fe3−δO

et al. 2019

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“…Some of the most important of these methods are electrospinning [34], plasmon-enhanced spectroscopy [35], Ultraviolet fluorescence [36], adhesion [37], novel flame-gradient [38], and direct growth on Titanium foil [39], adsorption [40], layer by layer [41] and electron beam [42].…”

Section: Physical Methodsmentioning

confidence: 99%

“…Finally, a film of Fe 2 O 3 nanorods will be shaped by calcination of substrate at 600°C for 2 h. To provide a hydrophobic surface, the resulting film soak on n-hexane solution for 5 h at room temperature and then dried under nitrogen gas ( Figure 12 and Figure 13) . [36].…”

Section: Adhesionmentioning

confidence: 99%

Fabrication of magnetic nanorods and their applications in medicine

2017

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Abstract:Nanorods in nanotechnology called a specific type of morphology of nanoscale materials that their dimensions range is from 1 to 100 nm. Nanorods can be synthesized from metal or semi-conductive material with a surface to volume ratio of 3-5. One method of making nanorods is direct chemical method. Ligands compounds as a shape control agents cause growth the nanorods and create stretched and extended modes of them. In recent years, magnetic nanorods are one of the nanorods that have been raised in the field of nano medicine [Nath S, Kaittanis C, Ramachandran V, Dalal NS, Perez JM. Synthesis, magnetic characterization, and sensing applications of novel dextran-coated iron oxide nanorods. Chem Mater. 2009;21:1761-7.]. Superparamagnetic properties of magnetic nanorods causes to sensing be done with high accuracy. In addition, other applications of magnetic nanorods are in the field of separation and treatment [Hu B, Wang N, Han L, Chen ML, Wang JH. Magnetic nanohybrids loaded with bimetal core-shell-shell nanorods for bacteria capture, separation, and near-infrared photothermal treatment. Chemistry. 2015;21:6582-9.]. Therefore, in biomedical applications, the nanorods are used usually with biological molecules such as antibodies [Schrittwieser S, Pelaz B, Parak WJ, Lentijo-Mozo S, Soulantica K, Dieckhoff J, et al. Homogeneous protein analysis by magnetic core-shell nanorod probes. ACS Appl Mater Interfaces. 2016;8:8893-9.]. For this purpose, in the present work we will try to introduce magnetic nanorods and mention their different methods of synthesis and applications.

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“…The PL spectra were measured using spectrometer with grating 600grooves/mm blazed at 300 nm, and a sensitive liquid nitrogen cooled CCD camera [21].…”

Section: Methodsmentioning

confidence: 99%

Growth of ZnO nanolayers inside the capillaries of photonic crystal fibres

Konidakis¹,

Androulidaki²,

Zito³

et al. 2014

Thin Solid Films

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In this study, we describe the formation of ZnO nanolayers inside the air capillaries of a silica photonic crystal fibre (PCF), targeting random laser and organic vapor sensing applications. ZnO nanolayers were developed by infiltrating the capillaries of the silica PCF with Zn-acetate/methanol solutions of various concentrations, followed by annealing treatments. The growth and morphology of the synthesized ZnO nanolayers were characterized by means of scanning electron microscopy (SEM), and found to be affected by the concentration of the Zn-acetate/methanol infiltration solution. For low concentrations inspection with SEM revealed the formation of 25 and 100 nm thick ZnO nanolayers across the entire length of the infiltrated capillaries, whereas increasing the Zn-acetate concentration resulted to the formation of randomly placed isolated ZnO nanorods. Room temperature photoluminescence spectra of the ZnO nanolayers inside the PCF were measured and compared with the corresponding spectra reported for ZnO structures formed on typical surfaces.

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Colloidal Anisotropic ZnO–Fe@Fe_xO_y Nanoarchitectures with Interface-Mediated Exchange-Bias and Band-Edge Ultraviolet Fluorescence

Cited by 28 publications

References 74 publications

Vacancy-Driven Noncubic Local Structure and Magnetic Anisotropy Tailoring in FexO−Fe3−δO

Vacancy-Driven Noncubic Local Structure and Magnetic Anisotropy Tailoring in FexO−Fe3−δO

Fabrication of magnetic nanorods and their applications in medicine

Growth of ZnO nanolayers inside the capillaries of photonic crystal fibres

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