Influence of the nanoparticles agglomeration state in the quantum-confinement effects: Experimental evidences

Lorite, I.; Romero, J.J.; Fernández, J.F.

doi:10.1063/1.4914107

Cited by 23 publications

(6 citation statements)

References 18 publications

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“…Five main phonon excitations were observed at T A = 450 °C, as shown at the bottom of Fig. 6(a), which are in good agreement with the values predicted by the group theory and the related report of the Co 3 O 4 nanoparticles 37,38 , consisting of + E g + + + A 1g 39–42 . The band at 674 cm −1 is viewed as the symmetric Co-O stretching vibration of the octahedral (CoO 6 ) group, which is assigned to the A 1g species in the spectroscopic symmetry.…”

Section: Resultssupporting

confidence: 87%

Role of cobalt cations in short range antiferromagnetic Co3O4 nanoparticles: a thermal treatment approach to affecting phonon and magnetic properties

Gawali

Gandhi

Gaikwad

et al. 2018

Sci Rep

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We report the phonon and magnetic properties of various well-stabilized Co3O4 nanoparticles. The net valence in cobalt (II)/(III) cation can be obtained by subtracting the Co2+ ions in tetrahedral interstices and Co3+ ions in the octahedral interstices, respectively, which will possess spatial inhomogeneity of its magnetic moment via Co2+ in tetrahedra and Co3+ in octahedral configurations in the normal spinel structure. Furthermore, the distribution of Co2+/Co3+ governed by various external (magnetic field and temperature) and internal (particle size and slightly distorted CoO6 octahedra) sources, have led to phenomena such as a large redshift of phonon-phonon interaction and short-range magnetic correlation in the inverse spinel structure. The outcome of our study is important in terms of the future development of magnetic semiconductor spintronic devices of Co3O4.

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Section: Resultssupporting

confidence: 87%

Role of cobalt cations in short range antiferromagnetic Co3O4 nanoparticles: a thermal treatment approach to affecting phonon and magnetic properties

Gawali

Gandhi

Gaikwad

et al. 2018

Sci Rep

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“…In this configuration phonons can be partially reflected at the particle's surface or can be transmitted to other systems as phonon bottlenecks [60]. Partially reflected phonons seem to present a slower decay, which allows a larger addition of modes out of the Brillouin zone centre than those given for the total reflected phonon in a single nanoparticle [61]. This effect produces a larger red shift and FWHM broadening for aggregated nanoparticles, which is not presented for the isolated ones.…”

Section: Thermal Stability Of Shell Raman Modesmentioning

confidence: 95%

Investigation of thermal stability of 2D and 3D CoAl2O4 particles in core-shell nanostructures by Raman spectroscopy

Álvarez-Docio

Reinosa

Campo

et al. 2019

Journal of Alloys and Compounds

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We are studying the formation of a nanostructured spinel CoAl2O4 layer on α-Al2O3 giving rise to a core-shell composite. In the final product, two mechanisms of CoAl2O4 crystallization onto a α-Al2O3 microparticle surface are observed, depending on the dispersion grade of Co3O4: a 3D nanostructure from the arrangement of Co3O4 agglomerated nanoparticles; 2D nanoparticles from the diffusion mechanism of isolated Co3O4 nanoparticles. As a consequence, two different crystallization pathways may occur during the thermal treatment. In order to understand the formation mechanisms a Raman Confocal Study is performed. The features of the Raman spectra of the samples depend strongly on the morphology of the nanoparticles located in the shell of the microparticle.Average spectra of the samples show a variation in the Raman shift between the different samples. The differences between 3D or 2D structures is associated with the transmission of phonons among the nanoparticles. The high results clearly indicate that extrinsic parameters such as the size of the crystals and their aggregation state affects their Raman properties.

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“…The band gap increasing with the reduction of particle size is in agreement with the quantum confinement effects that it is also modulated by the agglomeration state. In nanoparticle agglomerates, there is a particle–particle phonon partial transmission, which produces a larger relaxation of the momentum conservation than in single isolated nanoparticles . So, the lowest band gap value for the NS-ZnO with respect to ZnO microparticles and nanoparticles band gap values is a consequence of the agglomerated nanoparticles in the nanostructure organization.…”

Section: Resultsmentioning

confidence: 99%

ZnO Nanoporous Spheres with Broad-Spectrum Antimicrobial Activity by Physicochemical Interactions

Lucas-Gil

Leret

Monte-Serrano

et al. 2018

ACS Appl. Nano Mater.

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The extensive range of applications where synthetic nanomaterials are nowadays used is causing a huge commercial market. An incipient use of these nanomaterials arises from the need to generate alternative antimicrobial agents, anticipating the development of resistant microorganisms. Here, we show a nanostructured ZnO with antimicrobial properties and low-cytotoxicity based on a nanoparticles arrangement by controlling the formation of sintering-neck into nanoporous spheres. The antimicrobial effectiveness of ZnO spheres is tested in a broad-spectrum of microorganisms such as fungi, Gram-negative and Gram-positive bacteria. The hierarchical structures show highly effective antimicrobial activity at low concentrations and in relatively short action times (24-72h). We demonstrate that the enhanced antimicrobial properties against microorganisms are ascribed to a combining of both physical and chemical interactions between microorganism and ZnO. The approximation mechanism between microorganism and ZnO is provided through electrostatic forces (physical interaction) which, thanks to the ZnO-microorganism proximity, promote a rapid release of zinc cations and the reactive oxygen species penetration into microorganisms (chemical interaction). We believe that this work provides insights on the mechanisms underlying the interactions ZnOmicroorganism and possess a combined action mechanism for which nanostructured ZnO is so effective to combat microorganisms.

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Influence of the nanoparticles agglomeration state in the quantum-confinement effects: Experimental evidences

Cited by 23 publications

References 18 publications

Role of cobalt cations in short range antiferromagnetic Co3O4 nanoparticles: a thermal treatment approach to affecting phonon and magnetic properties

Role of cobalt cations in short range antiferromagnetic Co3O4 nanoparticles: a thermal treatment approach to affecting phonon and magnetic properties

Investigation of thermal stability of 2D and 3D CoAl2O4 particles in core-shell nanostructures by Raman spectroscopy

ZnO Nanoporous Spheres with Broad-Spectrum Antimicrobial Activity by Physicochemical Interactions

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