The role of oxygen and water on molybdenum nanoclusters for electro catalytic ammonia production

• Jakob G. Howalt and
• Tejs Vegge

Beilstein J. Nanotechnol. 2014, 5, 111–120, doi:10.3762/bjnano.5.11

• preferred over H in nitrogen vacancy sites at lower nitrogen coverages at the potential of U = −0.6 V needed for electrochemical ammonia production through the associative mechanism [2]. Adsorption of oxygen atoms at nitrogen vacancy sites is presented in Figure 1, where they have been adsorbed at the

• −1.58 eV increasing to −2.15 eV. Under these conditions, the vacancy sites will be filled with oxygen and block nitrogen molecules from adsorbing to the active sites and stop the electrochemical formation of ammonia. At the potentials needed for ammonia production (−0.6 V), the adsorption of oxygen is

• the fabrication process. Formation of ammonia at relative high oxygen coverage Nitrogen molecules are not able to adsorb to neither an oxygen vacancy site nor ontop of an oxygen atom at high oxygen coverages. Once the oxygen skin has been partially reduced, the nitrogen molecules adsorb onto the

Simulation of electron transport during electron-beam-induced deposition of nanostructures

• Francesc Salvat-Pujol,
• Harald O. Jeschke and
• Roser Valentí

Beilstein J. Nanotechnol. 2013, 4, 781–792, doi:10.3762/bjnano.4.89

• the ionized shell. A second electron from an outer shell, S1, fills the vacancy and, subsequently, two processes are possible: (1) a radiative transition in which a photon is emitted with a characteristic energy US0 − US1, where U denotes the ionization energy of the corresponding shell, or (2

Ellipsometry and XPS comparative studies of thermal and plasma enhanced atomic layer deposited Al₂O₃-films

• Jörg Haeberle,
• Karsten Henkel,
• Hassan Gargouri,
• Franziska Naumann,
• Bernd Gruska,
• Michael Arens,
• Massimo Tallarida and
• Dieter Schmeißer

Beilstein J. Nanotechnol. 2013, 4, 732–742, doi:10.3762/bjnano.4.83

• the PE-ALD samples. For the 200 °C T-ALD sample it is only about 2 × 1011 cm−2. Tetrahedral coordinated Al has a charge of −3 [29] and can be counted as an aluminum vacancy which can react with an oxygen atom originating from the SiO2 interface resulting in a net negative charge [1][29]. Moreover

Modulation of defect-mediated energy transfer from ZnO nanoparticles for the photocatalytic degradation of bilirubin

• Tanujjal Bora,
• Karthik K. Lakshman,
• Soumik Sarkar,
• Abhinandan Makhal,
• Samim Sardar,
• Samir K. Pal and
• Joydeep Dutta

Beilstein J. Nanotechnol. 2013, 4, 714–725, doi:10.3762/bjnano.4.81

• ; Förster resonance energy transfer (FRET); neonatal jaundice; oxygen vacancy; photocatalysis; phototherapy; zinc oxide nanoparticles; Introduction Bilirubin (BR) is a yellow-orange pigment which is a byproduct of the normal heme catabolism in mammals. In the human body, 250–400 mg BR is produced every day

• ]. It has been reported that the native defects in the ZnO lattice, mostly the oxygen vacancy sites, play an important role in the photocatalytic activity of the nanostructures [11]. Oxygen vacancies have been reported as the cause of the characteristic green luminescence of ZnO [12][13][14]. These

• large and broad green–yellow emission centered at around 530 nm, which can be attributed to the oxygen vacancy defect states (mostly present at the surface of the nanoparticles) [27]. A. van Dijken et al. [28] have proposed the transition of a photo-excited electron from the conduction band of ZnO to a

Evolution of microstructure and related optical properties of ZnO grown by atomic layer deposition

• Adib Abou Chaaya,
• Roman Viter,
• Mikhael Bechelany,
• Zanda Alute,
• Donats Erts,
• Anastasiya Zalesskaya,
• Kristaps Kovalevskis,
• Vincent Rouessac,
• Valentyn Smyntyna and
• Philippe Miele

Beilstein J. Nanotechnol. 2013, 4, 690–698, doi:10.3762/bjnano.4.78

• defect concentration and diminishes at annealing in an oxygen environment (oxygen vacancy healing) [21]. One of the methods applied to analyze the crystalline structure and defect level in zinc oxide is photoluminescence. It has been shown that ZnO exhibits a narrow UV emission band in the 378–381 nm

Characterization of electroforming-free titanium dioxide memristors

• John Paul Strachan,
• J. Joshua Yang,
• L. A. Montoro,
• C. A. Ospina,
• A. J. Ramirez,
• A. L. D. Kilcoyne,
• Gilberto Medeiros-Ribeiro and
• R. Stanley Williams

Beilstein J. Nanotechnol. 2013, 4, 467–473, doi:10.3762/bjnano.4.55

• technique has been used for previous studies of the single layer TiO2 memristor devices and can identify the presence of spatially-localized channels of oxygen vacancy rich Ti–O phases through analysis of the near-edge X-ray absorption fine structure (NEXAFS) [26]. After electrical operation of the

• observed in titanium oxide based resistance switching devices [24][25][26][27] by engineering devices with an oxygen deficient layer which can serve as a vacancy reservoir. It was shown that, electrically, such a structure removed the need for a high voltage electroforming step and the as-fabricated device

Digging gold: keV He⁺ ion interaction with Au

• Vasilisa Veligura,
• Gregor Hlawacek,
• Robin P. Berkelaar,
• Raoul van Gastel,
• Harold J. W. Zandvliet and
• Bene Poelsema

Beilstein J. Nanotechnol. 2013, 4, 453–460, doi:10.3762/bjnano.4.53

• of interlayer diffusion by the step edge or Ehrlich–Schwoebel barrier [14][20][24][25][26][27][28]. The activation energy for vacancy diffusion on Au{111} is much higher than the one for adatoms [29], hence we can suppose that at room temperature adatoms are dominantly responsible for the pattern

• well-known phenomenon [32][33][34]. After entering the crystal, an energetic He+ ion creates vacancy–interstitial pairs. These vacancies can aggregate into bigger voids. Since helium is hardly solvable in metals, it is effectively trapped at open-volume defects and has a tendency to agglomerate into

Photoresponse from single upright-standing ZnO nanorods explored by photoconductive AFM

• Igor Beinik,
• Markus Kratzer,
• Astrid Wachauer,
• Lin Wang,
• Yuri P. Piryatinski,
• Gerhard Brauer,
• Xin Yi Chen,
• Yuk Fan Hsu,
• Aleksandra B. Djurišić and
• Christian Teichert

Beilstein J. Nanotechnol. 2013, 4, 208–217, doi:10.3762/bjnano.4.21

• corresponding energy-level diagram also accounting for the band bending due to surface states is presented in Figure 6. The model involves a two-step process where an oxygen vacancy VO changes its state from nonconductive (α-configuration of defect localized state (DLS), ) to conductive (β-configuration of DLS

• an oxygen vacancy are marked as (1), (2) and (3), respectively. Acknowledgements This work was financially supported by the Austrian Science Fund (FWF) under Project No. P19636-N20.

Plasticity of Cu nanoparticles: Dislocation-dendrite-induced strain hardening and a limit for displacive plasticity

• Antti Tolvanen and
• Karsten Albe

Beilstein J. Nanotechnol. 2013, 4, 173–179, doi:10.3762/bjnano.4.17

• activity (stacking faults within the encapsulated material even though the extruded material was not crystalline) and thermodynamical arguments stating the insufficient speed of diffusion for vacancy-assisted creep in the experimental system. Yet, neither dislocation nucleation nor dislocation interactions

Diamond nanophotonics

• Katja Beha,
• Helmut Fedder,
• Marco Wolfer,
• Merle C. Becker,
• Petr Siyushev,
• Mohammad Jamali,
• Anton Batalov,
• Christopher Hinz,
• Jakob Hees,
• Lutz Kirste,
• Harald Obloh,
• Etienne Gheeraert,
• Boris Naydenov,
• Ingmar Jakobi,
• Florian Dolde,
• Sébastien Pezzagna,
• Daniel Twittchen,
• Matthew Markham,
• Daniel Dregely,
• Harald Giessen,
• Jan Meijer,
• Fedor Jelezko,
• Christoph E. Nebel,
• Rudolf Bratschitsch,
• Alfred Leitenstorfer and
• Jörg Wrachtrup

Beilstein J. Nanotechnol. 2012, 3, 895–908, doi:10.3762/bjnano.3.100

• creation of single color centers in diamond is achieved by implantation of nitrogen atoms through high-aspect-ratio channels in a mica mask. Enhanced broadband single-photon emission is demonstrated by coupling nitrogen–vacancy centers to plasmonic resonators, such as metallic nanoantennas. Improved photon

• incorporate color centers based on nickel and tungsten, in situ into diamond using microwave-plasma-enhanced chemical vapor deposition. The fabrication of silicon–vacancy centers in nanodiamonds by microwave-plasma-enhanced chemical vapor deposition is discussed in addition. Keywords: CVD diamond doping

• vibrational levels and its strength depends on how much the optical emission couples to lattice vibrations. Figure 3 shows a typical room-temperature optical emission spectrum of the nitrogen–vacancy (NV) color center in diamond. The resonant optical emission appears as a weak peak at a wavelength of 637 nm

Pure hydrogen low-temperature plasma exposure of HOPG and graphene: Graphane formation?

• Baran Eren,
• Dorothée Hug,
• Laurent Marot,
• Rémy Pawlak,
• Marcin Kisiel,
• Roland Steiner,
• Dominik M. Zumbühl and
• Ernst Meyer

Beilstein J. Nanotechnol. 2012, 3, 852–859, doi:10.3762/bjnano.3.96

• ) [32]. Such a broadening was also observed for HOPG that had been exposed to a low-energy argon plasma, and the reason for this was stated as geometric defects (roughening) without any contribution from vacancy formation or hydrogenation [22]. In a similar manner, the broadening of the C 1s peak in our

Plasmonics-based detection of H₂ and CO: discrimination between reducing gases facilitated by material control

• Gnanaprakash Dharmalingam,
• Nicholas A. Joy,
• Benjamin Grisafe and
• Michael A. Carpenter

Beilstein J. Nanotechnol. 2012, 3, 712–721, doi:10.3762/bjnano.3.81

• vacancies in each of the films. For the calculation of the oxygen-vacancy concentration in all films, a general assumption was that the YSZ film had a cubic fluorite lattice structure. The calculations were performed by taking into account the deposited area, thickness and lattice parameter of the YSZ film

• medium-particle sample and 4.08 × 1015/cm2 for the large-particle sample. Given the proposed reaction mechanism, the enhanced response towards H2 for the small-particle sample may be due to the highest oxygen vacancy concentration in this film among all the samples, which would facilitate an increase in

Spontaneous dissociation of Co₂(CO)₈ and autocatalytic growth of Co on SiO₂: A combined experimental and theoretical investigation

• Kaliappan Muthukumar,
• Harald O. Jeschke,
• Roser Valentí,
• Evgeniya Begun,
• Johannes Schwenk,
• Fabrizio Porrati and
• Michael Huth

Beilstein J. Nanotechnol. 2012, 3, 546–555, doi:10.3762/bjnano.3.63

• this study, we consider fully (FOH) and partially hydroxylated (POH) SiO2 surfaces that directly represent the untreated and pretreated surfaces. For the POH-SiO2 surfaces three different cases that differ in the degree of hydroxylation, corresponding to an OH vacancy concentration of 11, 22 and 33

Functionalised zinc oxide nanowire gas sensors: Enhanced NO₂ gas sensor response by chemical modification of nanowire surfaces

• Eric R. Waclawik,
• Jin Chang,
• Andrea Ponzoni,
• Isabella Concina,
• Dario Zappa,
• Elisabetta Comini,
• Nunzio Motta,
• Guido Faglia and
• Giorgio Sberveglieri

Beilstein J. Nanotechnol. 2012, 3, 368–377, doi:10.3762/bjnano.3.43

• which a gas sensor can achieve enhanced response in the case of ZnO nanowire sensors. For instance it is well known that gas sensitivity to NO2 is linearly proportional to oxygen-vacancy-related defects [25]. THMA-SAMs appeared to have little effect on ΔR/R with NO2 exposure, so in this case the surface

Noncontact atomic force microscopy study of the spinel MgAl₂O₄(111) surface

• Morten K. Rasmussen,
• Kristoffer Meinander,
• Flemming Besenbacher and
• Jeppe V. Lauritsen

Beilstein J. Nanotechnol. 2012, 3, 192–197, doi:10.3762/bjnano.3.21

• do not unambiguously determine the observed structure, and the detailed features, such as the specific size of the triangular features, may be influenced by other factors such as vacancy repulsion and edge energies, which are not readily explained by our data. It should be possible to image the

Molecular-resolution imaging of pentacene on KCl(001)

• Julia L. Neff,
• Jan Götzen,
• Enhui Li,
• Michael Marz and
• Regina Hoffmann-Vogel

Beilstein J. Nanotechnol. 2012, 3, 186–191, doi:10.3762/bjnano.3.20

• an upright configuration. The molecular arrangement was resolved in high-resolution images. In these images two different types of patterns were observed, which switch repeatedly. In addition, defects were found, such as a molecular vacancy and domain boundaries. Keywords: KCl; molecular growth

• observed. Furthermore, the high-resolution images show domain boundaries and a defect resulting from a molecular vacancy. Experimental Experiments were carried out in an ultrahigh-vacuum (UHV) variable-temperature SFM (Omicron NanoTechnology GmbH, Taunusstein, Germany) with a base pressure below 3 × 10−10

• the undisturbed island. This line defect shows the true molecular resolution of pattern I. For pattern II a point-like defect is displayed in Figure 3a. Here, a darker area is observed with the size of half a unit cell. We attribute this defect to a molecular vacancy caused by one missing molecule

Size-dependent phase diagrams of metallic alloys: A Monte Carlo simulation study on order–disorder transitions in Pt–Rh nanoparticles

• Johan Pohl,
• Christian Stahl and
• Karsten Albe

Beilstein J. Nanotechnol. 2012, 3, 1–11, doi:10.3762/bjnano.3.1

• due to the fact that vacancy diffusion is frozen at these temperatures, making it impossible to establish thermodynamic equilibrium in the particle within an observable time frame. Nevertheless, the results should give us valuable general insights into ordered-phase equilibria in nanoparticles. In the

Kinetic lattice Monte-Carlo simulations on the ordering kinetics of free and supported FePt L1₀-nanoparticles

• Michael Müller and
• Karsten Albe

Beilstein J. Nanotechnol. 2011, 2, 40–46, doi:10.3762/bjnano.2.5

• other mechanisms like interstitial diffusion play a role for atomic rearrangements. It is rather the vacancy-mediated site exchange that is responsible for the ordering. Therefore, the ordering kinetics depends on the concentration and mobility of vacancies in the nanoparticle. In a recent paper, we

• have shown that the thermal vacancy concentration in the inner part of a metallic nanoparticle is significantly reduced [13]. This can be attributed to the excess energy of surface formation that leads to an 1/r-dependence of the vacancy formation energy. Considering this, one can anticipate that the

• ordering kinetics is slower than in the bulk counterpart because of the reduced vacancy concentration. On the other hand, the formation of L10 domains is a nucleation process and therefore the presence of surface sites can facilitate the formation of ordered domains. In addition, the interface to the