Ion-sensing properties of 1D vanadium pentoxide nanostructures

The application of one-dimensional (1D) V2O5 center dot nH(2)O nanostructures as pH sensing material was evaluated. 1D V2O5 center dot nH(2)O nanostructures were obtained by a hydrothermal method with systematic control of morphology forming different nanostructures: nanoribbons, nanowires and nanorods. Deposited onto Au-covered substrates, 1D V2O5 center dot nH(2)O nanostructures were employed as gate material in pH sensors based on separative extended gate FET as an alternative to provide FET isolation from the chemical environment. 1D V2O5 center dot nH(2)O nanostructures showed pH sensitivity around the expected theoretical value. Due to high pH sensing properties, flexibility and low cost, further applications of 1D V2O5 center dot nH(2)O nanostructures comprise enzyme FET-based biosensors using immobilized enzymes.

Chemical mechanism of controlled nitric oxide release from trans-[RuCl([15]aneN(4))NO](PF6)(2) as a vasorelaxant agent

The nitrosyl ruthenium complex, trans-[RuCl([15]aneN(4))NO](PF6)(2), ([15]aneN(4) = 1,4,8,12-tetraazacyclopentadecane), exhibits vasorelaxation characteristics attributed to its nitric oxide release properties. The observed in vitro and in vivo vasodilation is dependent on noradrenaline concentration. We report here the chemical mechanism of the reaction between noradrenaline and trans-[RuCl([15]aneN(4))NO](PF6)(2) in aqueous phosphate buffer solution at pH 7.40. NO measurement by NO-sensor electrode, cyclic voltammetry, (PNMR)-P-31 and HPLC analysis were used to investigate the reduction process as the fundamental step for NO release characteristic of trans-[RuCl([15]aneN(4))NO](PF6)(2). A supramolecular species containing HPO4 (2-) as a bridging group between noradrenaline and trans-[RuCl([15]aneN(4))NO](PF6)(2) is suggested as an intermediate prior to the reduction of the nitrosyl ruthenium complex.

Recent Advances in the Development of Magnetically Recoverable Metal Nanoparticle Catalysts

The aim of this Account is to provide an overview of our current research activities on the design and modification of superparamagnetic nanomaterials for application in the field of magnetic separation and catalysis. First, an introduction of magnetism and magnetic separation is done. Then, the synthetic strategies that have been developed for generating superparamagnetic nanoparticles spherically coated by silica and other oxides, with a focus on well characterized systems prepared by methods that generate samples of high quality and easy to scale- up, are discussed. A set of magnetically recoverable catalysts prepared in our research group by the unique combination of superparamagnetic supports and metal nanoparticles is highlighted. This Account is concluded with personal remarks and perspectives on this research field.

Growth kinetics of CdS in germanium oxide glassy matrix

In the present work we revisit the size data of CdS microcrystals previously collected in the glassy matrix of Germanium oxide. The CdS clusters analyzed using electron microscopy images have shown a wurtzite structure. The mean average radius, dispersion and volume evaluated from the histograms showed good agreement for t(1/3), t(2/3) and t laws, respectively. We observed that the amount of microcrystals remains constant throughout the heat treatment process, as well as that the radii distribution has a lower limit and increases with heat treatment. The distribution of radii follows a distribution similar to the Lifshitz-Slyozov-Wagner distribution limited in the origin. Discussions led to the conclusion that the growth of CdS is a process that occurs after the fluctuating nucleation and coalescence phases. We then analyze the growth process, assuming that the evaporation is overcome by the precipitation rate, stabilizing all clusters with respect to dissolution back into the matrix. The problem was simplified neglecting anisotropy and the assuming a spherical shape for clusters and particles. The low interface tension was described in terms of an empirical potential barrier in the surface of the cluster. The growth dynamics developed considering that the number of clusters remains constant, and that the minimum size of these clusters grow with time, as the first order approximation showed a good agreement with the flaw. (C) 2012 Elsevier B.V. All rights reserved.

First-principles studies of complex magnetism in Mn nanostructures on the Fe(001) surface

The magnetic properties of Mn nanostructures on the Fe(001) surface have been studied using the noncollinear first-principles real space-linear muffin-tin orbital-atomic sphere approximation method within density-functional theory. We have considered a variety of nanostructures such as adsorbed wires, pyramids, and flat and intermixed clusters of sizes varying from two to nine atoms. Our calculations of interatomic exchange interactions reveal the long-range nature of exchange interactions between Mn-Mn and Mn-Fe atoms. We have found that the strong dependence of these interactions on the local environment, the magnetic frustration, and the effect of spin-orbit coupling lead to the possibility of realizing complex noncollinear magnetic structures such as helical spin spiral and half-skyrmion.

Ethanol and Water Adsorption on Close-Packed 3d, 4d, and 5d Transition-Metal Surfaces: A Density Functional Theory Investigation with van der Waals Correction

Nowadays, there is a great interest in the economic success of direct ethanol fuel cells; however, our atomistic understanding of the designing of stable and low-cost catalysts for the steam reforming of ethanol is still far from satisfactory, in particular due to the large number of undesirable intermediates. In this study, we will report a first-principles investigation of the adsorption properties of ethanol and water at low coverage on close-packed transition-metal (TM) surfaces, namely, Fe(110), Co(0001), Ni(111), Cu(111), Ru(0001), Rh(111), Pd(111), Ag(111), Os(0001), Ir(111), Pt(111), and Au(111), employing density functional theory (DFT) calculations. We employed the generalized gradient approximation with the formulation proposed by Perdew, Burke, and Erzenholf (PBE) to the exchange correlation functional and the empirical correction proposed by S. Grimme (DFT+D3) for the van der Waals correction. We found that both adsorbates binds preferentially near or on the on top sites of the TM surfaces through the 0 atoms. The PBE adsorption energies of ethanol and water decreases almost linearly with the increased occupation of the 4d and 5d d-band, while there is a deviation for the 3d systems. The van der Waals correction affects the linear behavior and increases the adsorption energy for both adsorbates, which is expected as the van der Waals energy due to the correlation effects is strongly underestimated by DFT-PBE for weak interacting systems. The geometric parameters for water/TM are not affected by the van der Waals correction, i.e., both DFT and DFT+D3 yield an almost parallel orientation for water on the TM surfaces; however, DFT+D3 changes drastically the ethanol orientation. For example, DFT yields an almost perpendicular orientation of the C-C bond to the TM surface, while the C-C bond is almost parallel to the surface using DFT +D3 for all systems, except for ethanol/Fe(110). Thus, the van der Waals correction decreases the distance of the C atoms to the TM surfaces, which might contribute to break the C-C bond. The work function decreases upon the adsorption of ethanol and water, and both follow the same trends, however, with different magnitude (larger for ethanol/TM) due to the weak binding of water to the surface. The electron density increases mainly in the region between the topmost layer and the adsorbates, which explains the reduction of the substrate work function.

Magnetic nanohydrometallurgy: A promising nanotechnological approach for metal production and recovery using functionalized superparamagnetic nanoparticles

We report on a new, promising nanotechnological approach for hydrometallurgy based on recyclable, chemically functionalized superparamagnetic nanoparticles. In this process, the metal ions (e.g. Cu2+) are captured by the nanoparticles and confined at the electrode surface by means of an external magnet. Due to the pre-concentration effect the electrodeposition process is greatly improved, yielding the pure metal in a much shorter time in comparison with the conventional electrodeposition process. After the electrolysis, the magnetic nanoparticles are ready to return to the process. The proposed strategy can advantageously be incorporated in hydrometallurgy, reducing the number of steps associated with complexation, organic solvent extraction, metal release and diffusional electroprocessing, leading to a more sustainable technology. (C) 2012 Elsevier B.V. All rights reserved.

GIDL behavior of p- and n-MuGFET devices with different TiN metal gate thickness and high-k gate dielectrics

This work studies the gate-induced drain leakage (GIDL) in p- and n-MuGFET structures with different TiN metal gate thickness and high-k gate dielectrics. As a result of this analysis, it was observed that a thinner TiN metal gate showed a larger GIDL due to the different gate oxide thickness and a reduced metal gate work function. In addition, replacing SiON by a high-k dielectric (HfSiON) results for nMuGFETs in a decrease of the GIDL On the other hand, the impact of the gate dielectric on the GIDL for p-channel MuGFETs is marginal. The effect of the channel width was also studied, whereby narrow fin devices exhibit a reduced GIDL current in spite of the larger vertical electric field expected for these devices. Finally, comparing the effect of the channel type, an enhanced GIDL current for pMuGFET devices was observed. (C) 2011 Elsevier Ltd. All rights reserved.

Photo-induced electron transfer in supramolecular materials of titania nanostructures and cytochrome c

In the present paper, we report on the molecular interaction and photochemistry of TiO2 nanoparticles (NPs) and cytochrome c systems for understanding the effects of supramolecular organization and electron transfer by using two TiO2 structures: P25 TiO2 NPs and titanate nanotubes. The adsorption and reduction of cytochrome c heme iron promoted by photo-excited TiO2, arranged as P25 TiO2 NPs and as nanotubes, were characterized using electronic absorption spectroscopy, thermogravimetric analysis, and atomic force microscopy. In an aqueous buffered suspension (pH 8.0), the mass of cytochrome c adsorbed on the P25 TiO2 NP surface was 2.3 fold lower (0.75 mu g m(-2)) than that adsorbed on the titanate nanotubes (1.75 mu g m(-2)). Probably due to the high coverage of titanate nanotubes by adsorbed cytochrome c, the low amount of soluble remaining protein was not as efficiently photo-reduced by this nanostructure as it was by the P25 TiO2 NPs. Cytochrome c, which desorbed from both titanium materials, did not exhibit changes in its redox properties. In the presence of the TiO2 NPs, the photo-induced electron transfer from water to soluble cytochrome c heme iron was corroborated by the following findings: (i) identification by EPR of the hydroxyl radical production during the irradiation of an aqueous suspension of TiO2 NPs, (ii) impairment of a cytochrome c reduction by photo-excited TiO2 in the presence of dioxane, which affects the dielectric constant of the water, and (iii) change in the rate of TiO2-promoted cytochrome c reduction when water was replaced with D2O. The TiO2-promoted photo-reduction of cytochrome c was reverted by peroxides. Cytochrome c incorporated in the titanate nanotubes was also reversibly reduced under irradiation, as confirmed by EPR and UV-visible spectroscopy.

Femtosecond laser processing of glassy and polymeric matrices containing metals and semiconductor nanostructures

Tailoring properties of materials by femtosecond laser processing has been proposed in the last decade as a powerful approach for technological applications, ranging from optics to biology. Although most of the research output in this field is related to femtosecond laser processing of single either organic or inorganic materials, more recently a similar approach has been proposed to develop advanced hybrid nanomaterials. Here, we report results on the use of femtosecond lasers to process hybrid nanomaterials, composed of polymeric and glassy matrices containing metal or semiconductor nanostructures. We present results on the use of femtosecond pulses to induce Cu and Ag nanoparticles in the bulk of borate and borosilicate glasses, which can be applied for a new generation of waveguides. We also report on 3D polymeric structures, fabricated by two-photon polymerization, containing Au and ZnO nanostructures, with intense two-photon fluorescent properties. The approach based on femtosecond laser processing to fabricate hybrid materials containing metal or semiconductor nanostructures is promising to be exploited for optical sensors and photonics devices.

Noble-metal nanoparticles produced with colloidal lithography: fabrication, optical properties and applications

In this work, metal nanoparticles produced by nanosphere lithography were studied in terms of their optical properties (in connection to their plasmon resonances), their potential application in sensing platforms - for thin layer sensing and bio-recognition events -, and for a particular case (the nanocrescents), for enhanced spectroscopy studies. The general preparation procedures introduced early in 2005 by Shumaker-Parry et al. to produce metallic nanocrescents were extended to give rise to more complex (isolated) structures, and also, by combining colloidal monolayer fabrication and plasma etching techniques, to arrays of them. The fabrication methods presented in this work were extended not only to new shapes or arrangements of particles, but included also a targeted surface tailoring of the substrates and the structures, using different thiol and silane compounds as linkers for further attachment of, i.e. polyelectrolyte layers, which allow for a controlled tailoring of their nanoenvironment. The optical properties of the nanocrescents were studied with conventional transmission spectroscopy; a simple multipole model was adapted to explain their behaviour qualitatively. In terms of applications, the results on thin film sensing using these particles show that the crescents present an interesting mode-dependent sensitivity and spatial extension. Parallel to this, the penetrations depths were modeled with two simplified schemes, obtaining good agreement with theory. The multiple modes of the particles with their characteristic decay lengths and sensitivities represent a major improvement for particle-sensing platforms compared to previous single resonance systems. The nanocrescents were also used to alter the emission properties of fluorophores placed close to them. In this work, green emitting dyes were placed at controlled distances from the structures and excited using a pulsed laser emitting in the near infrared. The fluorescence signal obtained in this manner should be connected to a two-photon processes triggered by these structures; obtaining first insight into plasmon-mediated enhancement phenomena. An even simpler and faster approach to produce plasmonic structures than that for the crescents was tested. Metallic nanodiscs and nanoellipses were produced by means of nanosphere lithography, extending a procedure reported in the literature to new shapes and optical properties. The optical properties of these particles were characterized by extinction spectroscopy and compared to results from the literature. Their major advantage is that they present a polarization-dependent response, like the nanocrescents, but are much simpler to fabricate, and the resonances can be tailored in the visible with relative ease. The sensing capabilities of the metallic nanodiscs were explored in the same manner as for the nanocrescents, meaning their response to thin layers and to bio-recognition events on their surface. The sensitivity of these nanostructures to thin films proved to be lower than that of the crescents, though in the same order of magnitude. Experimental information about the near field extension for the Au nanodiscs of different sizes was also extracted from these measurements. Further resonance-tailoring approaches based on electrochemical deposition of metals on the nanodiscs were explored, as a means of modifying plasmon resonances by changing surface properties of the nanoparticles. First results on these experiments would indicate that the deposition of Ag on Au on a submonolayer coverage level can lead to important blue-shifts in the resonances, which would open a simple way to tailor resonances by changing material properties in a local manner.

Point defects in carbon nanostructures studied by in-situ electron microscopy

In the present work, the formation and migration of point defects induced by electron irradiation in carbon nanostructures, including carbon onions, nanotubes and graphene layers, were investigated by in-situ TEM. The mobility of carbon atoms normal to the layers in graphitic nanoparticles, the mobility of carbon interstitials inside SWCNTs, and the migration of foreign atoms in graphene layers or in layers of carbon nanotubes were studied. The diffusion of carbon atoms in carbon onions was investigated by annealing carbon onions and observing the relaxation of the compressed clusters in the temperature range of 1200 – 2000oC. An activation energy of 5.0±0.3 eV was obtained. This rather high activation energy for atom exchange between the layers not only prevents the exchange of carbon atoms between the layers at lower temperature but also explains the high morphological and mechanical stability of graphite nanostructures. The migration of carbon atoms in SWCNTs was investigated quantitatively by cutting SWCNT bundles repeatedly with a focused electron beam at different temperatures. A migration barrier of about 0.25 eV was obtained for the diffusion of carbon atoms inside SWCNTs. This is an experimental confirmation of the high mobility of interstitial atoms inside carbon nanotubes, which corroborates previously developed theoretical models of interstitial diffusivity. Individual Au and Pt atoms in one- or two-layered graphene planes and MWCNTs were monitored in real time at high temperatures by high-resolution TEM. The direct observation of the behavior of Au and Pt atoms in graphenic structures in a temperature range of 600 – 700°C allows us to determine the sites occupied by the metal atoms in the graphene layer and the diffusivities of the metal atoms. It was found that metal atoms were located in single or multiple carbon vacancies, not in off-plane positions, and diffused by site exchange with carbon atoms. Metal atoms showed a tendency to form clusters those were stable for a few seconds. An activation energy of around 2.5 eV was obtained for the in-plane migration of both Au and Pt atoms in graphene (two-dimensional diffusion). The rather high activation energy indicates covalent bonding between metal and carbon atoms. Metal atoms were also observed to diffuse along the open edge of graphene layers (one-dimensional diffusion) with a slightly lower activation energy of about 2.3 eV. It is also found that the diffusion of metal atoms in curved graphenic layers of MWCNTs is slightly faster than in planar graphene.

Near-field mediated enhancement effects on plasmonic nanostructures

In dieser Arbeit wird eine detaillierte Untersuchung und Charakterisierung der Zwei-Photonen-induzierten Fluoreszenzverstärkung von organischen Farbstoffen auf plasmonischen Nanostrukturen vorgestellt. Diese Fluoreszenzverstärkung ist insbesondere für hochaufgelöste Fluoreszenzmikroskopie und Einzelmolekülspektroskopie von großer Bedeutung. Durch die Zwei-Photonen-Anregung resultiert eine Begrenzung des Absorptionsprozesses auf das fokale Volumen. In Kombination mit dem elektrischen Nahfeld der Nanostrukturen als Anregungsquelle entsteht eine noch stärkere Verringerung des Anregungsvolumens auf eine Größe unterhalb der Beugungsgrenze. Dies erlaubt die selektive Messung ausgewählter Farbstoffe. Durch die Herstellung der Nanopartikel mittels Kolloidlithografie wird eine definierte, reproduzierbare Geometrie erhalten. Polymermultischichten dienen als Abstandshalter, um die Farbstoffe an einer exakten Distanz zum Metall zu positionieren. Durch die kovalente Anbindung des Farbstoffs an die oberste Schicht wird eine gleichmäßige Verteilung des Farbstoffs in geringer Konzentration erhalten. rnEs wird eine Verstärkung der Fluoreszenz um den Faktor 30 für Farbstoffe auf Goldellipsen detektiert, verglichen mit Farbstoffen außerhalb des Nahfelds. Sichelförmige Nanostrukturen erzeugen eine Verstärkung von 120. Dies belegt, dass das Ausmaß der Fluoreszenzverstärkung entscheidend von der Stärke des elektrischen Nahfelds der Nanostruktur abhängt. Auch das Material der Nanostruktur ist hierbei von Bedeutung. So erzeugen Silberellipsen eine 1,5-fach höhere Fluoreszenzverstärkung als identische Goldellipsen. Distanzabhängige Fluoreszenzmessungen zeigen, dass die Zwei-Photonen-angeregte Fluoreszenzverstärkung an strukturspezifischen Abständen zum Metall maximiert wird. Elliptische Strukturen zeigen ein Maximum bei einem Abstand von 8 nm zum Metall, wohingegen bei sichelförmigen Nanostrukturen die höchste Fluoreszenzintensität bei 12 nm gemessen wird. Bei kleineren Abständen unterliegt der Farbstoff einem starken Löschprozess, sogenanntes Quenching. Dieses konkurriert mit dem Verstärkungsprozess, wodurch es zu einer geringen Nettoverstärkung kommt. Hat die untersuchte Struktur Dimensionen größer als das Auflösungsvermögen des Mikroskops, ist eine direkte Visualisierung des elektrischen Nahfelds der Nanostruktur möglich. rnrnEin weiterer Fokus dieser Arbeit lag auf der Herstellung neuartiger Nanostrukturen durch kolloidlithografische Methoden. Gestapelte Dimere sichelförmiger Nanostrukturen mit exakter vertikaler Ausrichtung und einem Separationsabstand von etwa 10 nm wurden hergestellt. Die räumliche Nähe der beiden Strukturen führt zu einem Kopplungsprozess, der neue optische Resonanzen hervorruft. Diese können als Superpositionen der Plasmonenmoden der einzelnen Sicheln beschrieben werden. Ein Hybridisierungsmodell wird angewandt, um die spektralen Unterschiede zu erklären. Computersimulationen belegen die zugrunde liegende Theorie und erweitern das Modell um experimentell nicht aufgelöste Resonanzen. rnWeiterhin wird ein neuer Herstellungsprozess für sichelförmige Nanostrukturen vorgestellt, der eine präzise Formanpassung ermöglicht. Hierdurch kann die Lage der Plasmonenresonanz exakt justiert werden. Korrelationen der geometrischen Daten mit den Resonanzwellenlängen tragen zum grundlegenden Verständnis der Plasmonenresonanzen bei. Die vorgestellten Resultate wurden mittels Computersimulationen verifiziert. Der Fabrikationsprozess erlaubt die Herstellung von Dimeren sichelförmiger Nanostrukturen in einer Ebene. Durch die räumliche Nähe überlappen die elektrischen Nahfelder, wodurch es zu kopplungs-induzierten Shifts der Plasmonenresonanzen kommt. Der Unterschied zu theoretisch berechneten ungekoppelten Nanosicheln kann auch bei den gegenüberliegenden sichelförmigen Nanostrukturen mit Hilfe des Plasmonenhybridisierungsmodells erklärt werden.

Glycerol oxidehydration to acrylic acid on complex mixed-metal oxides

The project of this Ph.D. thesis is based on a co-supervised collaboration between Università di Bologna, ALMA MATER STUDIORUM (Italy) and Instituto de Tecnología Química, Universitat Politècnica de València ITQ-UPV (Spain). This Ph.D. thesis is about the synthesis, characterization and catalytic testing of complex mixed-oxide catalysts mainly related to the family of Hexagonal Tungsten Bronzes (HTBs). These materials have been little explored as catalysts, although they have a great potential as multifunctional materials. Their peculiar acid properties can be coupled to other functionalities (e.g. redox sites) by isomorphous substitution of tungsten atoms with other transition metals such as vanadium, niobium and molybdenum. In this PhD thesis, it was demonstrated how it is possible to prepare substituted-HTBs by hydrothermal synthesis; these mixed-oxide were fully characterize by a number of physicochemical techniques such as XPS, HR-TEM, XAS etc. They were also used as catalysts for the one-pot glycerol oxidehydration to acrylic acid; this reaction might represent a viable chemical route to solve the important issue related to the co-production of glycerin along the biodiesel production chain. Acrylic acid yields as high as 51% were obtained and important structure-reactivity correlations were proved to govern the catalytic performance; only fine tuning of acid and redox properties as well as the in-framework presence of vanadium are fundamental to achieve noteworthy yields into the acid monomer. The overall results reported herein might represent an important contribution for future applications of HTBs in catalysis as well as a general guideline for a multifaceted approach for their physicochemical characterization.

Analysis of zinc oxide nanoparticles as a potential mutagen of respiratory epithelia

Metallische Nanopartikel und ihre Oxide (z.B. ZnO NP, TiO2 NP und Fe2O3 NP) werden aufgrund ihrer chemischen und physikalischen Eigenschaften häufig als Additive in der Reifenproduktion, in Katalysatoren, Lebensmitteln, Arzneimitteln und Kosmetikprodukten verwendet. Künftig wird ein kontinuierlicher Anstieg der industriellen Anwendung (~ 1663 Tonnen im Jahr 2025) mit gesteigerter Freisetzung in die Umwelt erwartet, was zwangsläufig zu einer vermehrten Aufnahme über das respiratorische Epithel führt. Metalldampffieber ist als gesundheitsschädigender Effekt von Metalloxid-haltigen Aerosolen (z.B. ZnO) nach Inhalation bekannt. Immunreaktionen, wie beispielsweise Entzündungen, werden häufig mit der Entstehung von Sauerstoffradikalen (ROS) in Verbindung gebracht, die wiederum zu DNA-Schäden führen können. Drei mögliche Ursachen der Genotoxität werden angenommen: direkte Interaktion von Nanopartikeln mit intrazellulären Strukturen, Interaktion von Ionen dissoziierter Partikel mit intrazellulären Strukturen sowie die Entstehung von ROS initiiert durch Partikel oder Ionen.rnDie vorliegende Studie befasst sich mit den Mechanismen der Genotoxizität von ZnO Nanopartikeln (ZnO NP), als Beispiel für metallische Nanopartikel, im respiratorischen Epithel. In der Studie wurde gezielt die intrazelluläre Aufnahme und Verteilung von ZnO NP, deren Toxizität, deren DNA schädigendes Potential sowie die Aktivierung der DNA damage response (DDR) analysiert.rnEs konnten kaum internalisierte ZnO NP mittels TEM detektiert werden. Innerhalb der ersten Sekunden nach Behandlung mit ZnO NP wurde spektrofluorometrisch ein starker Anstieg der intrazellulären Zn2+ Konzentration gemessen. In unbehandelten Zellen war Zn2+ in granulären Strukturen lokalisiert. Die Behandlung mit ZnO NP führte zu einer Akkumulation von Zn2+ in diesen Strukturen. Im zeitlichen Verlauf verlagerten sich die Zn2+-Ionen in das Zytoplasma, sowie in Zellkerne und Mitochondrien. Es wurde keine Kolokalisation von Zn2+ mit den frühen Endosomen und dem endoplasmatischen Retikulum beobachtet. Die Vorbehandlung der Zellen mit Diethylen-triaminpentaessigsäure (DTPA), als extrazellulärem Komplexbildner, verhinderte den intrazellulären Anstieg von Zn2+ nach Behandlung mit den Partikeln.rnDie Behandlung mit ZnO NP resultierte in einer zeit- und dosisabhängigen Reduktion der zellulären Viabilität, während die intrazelluläre ROS-Konzentrationen in den ersten 30 min leicht und anschließend kontinuierlich bis zum Ende der Messung anstiegen. Außerdem verringerte sich das mitochondriale Membranpotential, während sich die Anzahl der frühapoptotischen Zellen in einer zeitabhängigen Weise erhöhte. rnDNA Doppelstrangbrüche (DNA DSB) wurden mittels Immunfluoreszenz-Färbung der γH2A.X foci sichtbar gemacht und konnten nach Behandlung mit ZnO NP detektiert werden. Die Vorbehandlung mit dem Radikalfänger N-Acetyl-L-Cytein (NAC) resultierte in stark reduzierten intrazellulären ROS-Konzentrationen sowie wenigen DNA DSB. Die DNA Schädigung wurde durch Vorbehandlung mit DTPA ganz verhindert.rnDie Aktivierung der DDR wurde durch die Analyse von ATM, ATR, Chk1, Chk2, p53 und p21 mittels Western Blot und ELISA nach Behandlung mit ZnO NP überprüft. Der ATR/Chk1 Signalweg wurde durch ZnO NP nicht aktiviert. Die Komplexierung von Zn2+ resultierte in einer verminderten ATM/Chk2 Signalwegaktivierung. Es zeigte sich, dass das Abfangen von ROS keinen Effekt auf die ATM/Chk2 Signalwegaktivierung hatte.rnZusammengefasst wurde festgestellt, dass die Exposition mit ZnO NP in der Entstehung von ROS, reduzierter Viabilität und vermindertem mitochondrialem Membranpotential resultiert, sowie zeitabhängig eine frühe Apoptose initiiert. ZnO NP dissoziierten extrazellulär und wurden schnell als Zn2+ über unbekannte Mechanismen internalisiert. Die Zn2+-Ionen wurden im Zytoplasma, sowie besonders in den Mitochondrien und dem Zellkern, akkumuliert. Die DDR Signalgebung wurde durch ZnO NP aktiviert, jedoch nicht durch NAC inhibiert. Es wurde gezeigt, dass DTPA die DDR Aktivierung komplett inhibierte. Die Behandlung mit ZnO NP induzierte DNA DSB. Die Inhibition von ROS reduzierte die DNA DSB und die Komplexierung der Zn2+ verhinderte die Entstehung von DNA DSB.rnDiese Daten sprechen für die Dissoziation der Partikel und die hierbei freigesetzten Zn2+ als Hauptmediator der Genotoxizität metallischer Nanopartikel. rn