Electronic Structure and Size of TiO 2 Nanoparticles of Controlled Size Prepared by Aerosol Methods

Soriano, L.; Ahonen, Petri; Kauppinen, Esko I.; Gómez-García, J.; Morant, Carmen; Palomares, F. J.; Sánchez‐Agudo, M.; Bressler, P.; Sanz, J. M.

doi:10.1007/s007060200057

Cited by 7 publications

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“…However, the physicochemical origin of • OH formation by NPs in biological systems is still unclear to date. Generally, the iron ion-catalyzed Fenton or Haber–Weiss reactions, which make use of Fenton chemistry, are considered to be the major mechanism for the generation of highly reactive hydroxyl radicals in biological systems . However, for heterogeneous NPs, both the free iron ions induced homogeneous and surface-catalyzed heterogeneous reactions may all contribute to the • OH formation, whereas the dominant reaction processes will depend on the specific biomicroenvironment.…”

Section: Resultsmentioning

confidence: 99%

“…Generally, the iron ion-catalyzed Fenton or Haber− Weiss reactions, which make use of Fenton chemistry, are considered to be the major mechanism for the generation of highly reactive hydroxyl radicals in biological systems. 37 However, for heterogeneous NPs, both the free iron ions induced homogeneous and surface-catalyzed heterogeneous reactions may all contribute to the • OH formation, whereas the dominant reaction processes will depend on the specific biomicroenvironment. Much research has reported that iron oxide NPs internalized by cells were mainly located in lysosome, 38,39 where the acidic microenvironment (4.5−5.5) causes the NPs dissolution.…”

Section: ■ Introductionmentioning

confidence: 99%

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Physicochemical Origin for Free Radical Generation of Iron Oxide Nanoparticles in Biomicroenvironment: Catalytic Activities Mediated by Surface Chemical States

et al. 2012

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A wide range of nanoparticles (NPs) have been found to generate free radicals in biological systems. Hence, it is hypothesized that free radical generation may play a key role in the mechanism of nanomaterial toxicity in vivo. However, the main physicochemical basis for the free radical generation particularly in the biomicroenvironment has not yet been fully established. In this study, we performed comprehensive spectroscopic techniques to probe the physicochemical origin of free radical generation induced by iron oxide nanoparticles in biomicroenvironment. We demonstrated that α-Fe2O3 and γ-Fe2O3 NPs induced hydroxyl radical (•OH) via homogeneous and heterogeneous Fenton process, depending on the biological microenvironment of pH and reducing agent presence. The physicochemical structures such as chemical states of oxygen and iron on nanosurface are the key factors in the homogeneous and heterogeneous catalytic reactions. A noteworthy finding was that in situ surface reduction of Fe2O3 NPs occurred in the presence of a physiological amount of biological reducing agents (l-cysteine or NADPH), which could enhance and even reverse the capacity of •OH generation by α-Fe2O3 and γ-Fe2O3 NPs under low pH 1.2 condition. The present study demonstrates that exploration of the physicochemical basis at the nanobio interface in biomicroenvironments may help to understand the mechanism of nanotoxicity and guide safe design of nanomaterials for biomedical application

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Section: Resultsmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Physicochemical Origin for Free Radical Generation of Iron Oxide Nanoparticles in Biomicroenvironment: Catalytic Activities Mediated by Surface Chemical States

et al. 2012

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“…The oxygen 1s XANES spectra of TiO 2 reflect the density of unoccupied electronic states of 2p type. Because the O 2p orbitals are hybridized with the Ti 3d and 4sp ones, they also account for these metal states. − Two energy regions can be distinguished (see Figure ): (i) the region from 530 to 535 eV, which is associated to transitions to the O(2p)-Ti(3d) band. As the crystal field splits the 3d levels into t 2g and e g this gives rise to two contributions labeled A and B, respectively.…”

Section: Resultsmentioning

confidence: 99%

Influence of N-Doping on the Structure and Electronic Properties of Titania Nanoparticle Photocatalysts

et al. 2006

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N-containing TiO(2)-based nanostructured materials (average particle size approximately 10 nm) with an anatase-type structure were investigated using oxygen (O) K-edge and titanium (Ti) K- and L-edge X-ray absorption near-edge spectroscopy (XANES). The Ti K pre-edge features indicate that samples predominantly contain ([6])Ti with some ([5])Ti, and there is no evidence for ([4])Ti. We observed that those samples with a larger fraction of Ti in a fivefold coordination, that is, with a significant number of oxygen vacancies, also present a modified Ti environment at the medium-range scale. The presence of these defects drastically modifies the electronic structure of the conduction band, as evidenced by the O K XANES spectra, but does not result in the presence of reduced Ti(3+) states. We discuss the influence of N-doping on titania nanoparticles and their structure, electronics and photocatalytic activity.

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“…Such a spectral broadening has previously been observed in XANES studies of other semiconductor nanoparticles (such as InAs, CdSe, and TiO 2 ) of similar sizes. [22][23][24] However, the interpretation of this effect is not straightforward since a number of factors, which are difficult to control, can affect XANES spectra. These factors include surface reconstruction and passivation, stress, particle-particle and particle-support interaction, quantum confinement, and charging.…”

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confidence: 99%

Atomic layer deposition of ZnO on ultralow-density nanoporous silica aerogel monoliths

Kucheyev

Biener

Wang

et al. 2005

Applied Physics Letters

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We report on atomic layer deposition of an ∼ 2-nm-thick ZnO layer on the inner surface of ultralow-density (∼ 0.5% of the full density) nanoporous silica aerogel monoliths with an extremely large effective aspect ratio of ∼ 10 5 (defined as the ratio of the monolith thickness to the average pore size). The resultant monoliths are formed by amorphous-SiO2/wurtzite-ZnO nanoparticles which are randomly oriented and interconnected into an open-cell network with an apparent density of ∼ 3% and a surface area of ∼ 100 m 2 g −1. Secondary ion mass spectrometry and high-resolution transmission electron microscopy imaging reveal excellent uniformity and crystallinity of ZnO coating. Oxygen K-edge and Zn L3-edge soft x-ray absorption near-edge structure spectroscopy shows broadened O 2p-as well as Zn 4s-, 5s-, and 3d-projected densities of states in the conduction band.

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Electronic Structure and Size of TiO 2 Nanoparticles of Controlled Size Prepared by Aerosol Methods

Cited by 7 publications

References 0 publications

Physicochemical Origin for Free Radical Generation of Iron Oxide Nanoparticles in Biomicroenvironment: Catalytic Activities Mediated by Surface Chemical States

Physicochemical Origin for Free Radical Generation of Iron Oxide Nanoparticles in Biomicroenvironment: Catalytic Activities Mediated by Surface Chemical States

Influence of N-Doping on the Structure and Electronic Properties of Titania Nanoparticle Photocatalysts

Atomic layer deposition of ZnO on ultralow-density nanoporous silica aerogel monoliths

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