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Journal of Physical Chemistry. C, Nanomaterials and Interfaces

Bernhard C Bayer, David A Bosworth, F Benjamin Michaelis, Raoul Blume, Gerlinde Habler, Rainer Abart, Robert S Weatherup, Piran R Kidambi, Jeremy J Baumberg, Axel Knop-Gericke, Robert Schloegl, Carsten Baehtz, Zoe H Barber, Jannik C Meyer, Stephan Hofmann
Nanocomposite thin films comprised of metastable metal carbides in a carbon matrix have a wide variety of applications ranging from hard coatings to magnetics and energy storage and conversion. While their deposition using nonequilibrium techniques is established, the understanding of the dynamic evolution of such metastable nanocomposites under thermal equilibrium conditions at elevated temperatures during processing and during device operation remains limited. Here, we investigate sputter-deposited nanocomposites of metastable nickel carbide (Ni3C) nanocrystals in an amorphous carbon (a-C) matrix during thermal postdeposition processing via complementary in situ X-ray diffractometry, in situ Raman spectroscopy, and in situ X-ray photoelectron spectroscopy...
October 6, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Rowan K Leary, Anjli Kumar, Patrick J Straney, Sean M Collins, Sadegh Yazdi, Rafal E Dunin-Borkowski, Paul A Midgley, Jill E Millstone, Emilie Ringe
Catalytic and optical properties can be coupled by combining different metals into nanoscale architectures in which both the shape and the composition provide fine-tuning of functionality. Here, discrete, small Pt nanoparticles (diameter = 3-6 nm) were grown in linear arrays on Au nanoprisms, and the resulting structures are shown to retain strong localized surface plasmon resonances. Multidimensional electron microscopy and spectroscopy techniques (energy-dispersive X-ray spectroscopy, electron tomography, and electron energy-loss spectroscopy) were used to unravel their local composition, three-dimensional morphology, growth patterns, and optical properties...
September 22, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Marco Carlotti, Maarten Degen, Yanxi Zhang, Ryan C Chiechi
Large-area tunneling junctions using eutectic Ga-In (EGaIn) as a top contact have proven to be a robust, reproducible, and technologically relevant platform for molecular electronics. Thus far, the majority of studies have focused on saturated molecules with backbones consisting mainly of alkanes in which the frontier orbitals are either highly localized or energetically inaccessible. We show that self-assembled monolayers of wire-like oligophenyleneethynylenes (OPEs), which are fully conjugated, only exhibit length-dependent tunneling behavior in a low-O2 environment...
September 15, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Arantxa Fernandes, David McKay, Scott Sneddon, Daniel M Dawson, Sebastian Lawson, Richard Veazey, Karl R Whittle, Sharon E Ashbrook
An NMR crystallographic approach, involving the combination of (119)Sn NMR spectroscopy, XRD, and DFT calculations, is demonstrated for the characterization of La2Sn2-x Ti x O7 ceramics. A phase change from pyrochlore (La2Sn2O7) to a layered perovskite phase (La2Ti2O7) is predicted (by radius ratio rules) to occur when x ≈ 0.95. However, the sensitivity of NMR spectroscopy to the local environment is able to reveal a significant two-phase region is present, extending from x = 1.8 to ∼0.2, with limited solid solution at the two extremes, in broad agreement with powder XRD measurements...
September 15, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Dominik Kriegner, Mykhailo Sytnyk, Heiko Groiss, Maksym Yarema, Wolfgang Grafeneder, Peter Walter, Ann-Christin Dippel, Matthias Meffert, Dagmar Gerthsen, Julian Stangl, Wolfgang Heiss
While galvanic exchange is commonly applied to metallic nanoparticles, recently its applicability was expanded to metal-oxides. Here the galvanic exchange is studied in metal/metal-oxide core/shell nanocrystals. In particular Sn/SnO2 is treated by Ag(+), Pt(2+), Pt(4+), and Pd(2+). The conversion dynamics is monitored by in situ synchrotron X-ray diffraction. The Ag(+) treatment converts the Sn cores to the intermetallic Ag x Sn (x ∼ 4) phase, by changing the core's crystal structure. For the analogous treatment by Pt(2+), Pt(4+), and Pd(2+), such a galvanic exchange is not observed...
September 8, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Christian Friedl, Thomas Renger, Hans V Berlepsch, Kai Ludwig, Marcel Schmidt Am Busch, Jörg Megow
Cryogenic transmission electron microscopy (cryo-TEM) studies suggest that TTBC molecules self-assemble in aqueous solution to form single-walled tubes with a diameter of about 35 Å. In order to reveal the arrangement and mutual orientations of the individual molecules in the tube, we combine information from crystal structure data of this dye with a calculation of linear absorbance and linear dichroism spectra and molecular dynamics simulations. We start with wrapping crystal planes in different directions to obtain tubes of suitable diameter...
September 1, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Jun Li, Stefano Gottardi, Leonid Solianyk, Juan Carlos Moreno-López, Meike Stöhr
The self-assembly of 1,3,5-benzenetribenzoic acid (BTB) molecules on both Cu(111) and epitaxial graphene grown on Cu(111) were studied by scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED) under ultrahigh vacuum conditions. On Cu(111), the BTB molecules were found to mainly arrange in close-packed structures through H-bonding between the (partially) deprotonated carboxylic acid groups. In addition, porous structures formed by intact BTB molecules-and also based on H-bonding-were observed...
August 18, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Brian G Alberding, Adam J Biacchi, Angela R Hight Walker, Edwin J Heilweil
Tin(II) monosulfide (SnS) is a semiconductor material with an intermediate band gap, high absorption coefficient in the visible range, and earth abundant, non-toxic constituent elements. For these reasons, SnS has generated much interest for incorporation into optoelectronic devices, but little is known concerning the charge carrier dynamics, especially as measured by optical techniques. Here, as opposed to prior studies of vapor deposited films, phase-pure colloidal SnS was synthesized by solution chemistry in three size regimes, ranging from nanometer- to micron-scale (SnS small nanoparticles, SnS medium 2D nanosheets, and SnS large 2D μm-sheets), and evaluated by time-resolved terahertz spectroscopy (TRTS); an optical, non-contact probe of the photoconductivity...
July 21, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Giulia Serrano, Stefan Wiespointner-Baumgarthuber, Stefano Tebi, Svetlana Klyatskaya, Mario Ruben, Reinhold Koch, Stefan Müllegger
We report a low-temperature scanning tunneling microscopy and spectroscopy study of the structural and electronic properties of a bilayer of terbium double-decker (bis(phthalocyaninato)terbium(III), TbPc2) molecules on Au(111) at 5 K. The TbPc2 molecules are found to adsorb flat on top of a first compact TbPc2 monolayer on Au(111), forming a square-like packing similar to the underlying first layer. Their frontier-orbital electronic structure, measured by tunneling conductance spectroscopy, clearly differs from that of the underlying first monolayer...
June 30, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Fan Shi, Ping He, Quinn A Best, Kirsten Groome, Milton L Truong, Aaron M Coffey, Greg Zimay, Roman V Shchepin, Kevin W Waddell, Eduard Y Chekmenev, Boyd M Goodson
Two synthetic strategies are investigated for the preparation of water-soluble iridium-based catalysts for NMR signal amplification by reversible exchange (SABRE). In one approach, PEGylation of a variant N-heterocyclic carbene provided a novel catalyst with excellent water solubility. However, while SABRE-active in ethanol solutions, the catalyst lost activity in >50% water. In a second approach, synthesis of a novel di-iridium complex precursor where the cyclooctadiene (COD) rings have been replaced by CODDA (1,2-dihydroxy-3,7-cyclooctadiene) leads to the creation of a catalyst [IrCl(CODDA)IMes] that can be dissolved and activated in water-enabling aqueous SABRE in a single step, without need for either an organic cosolvent or solvent removal followed by aqueous reconstitution...
June 9, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Joakim Löfgren, Henrik Grönbeck, Kasper Moth-Poulsen, Paul Erhart
Alkanethiolate monolayers on gold are important both for applications in nanoscience as well as fundamental studies of adsorption and self-assembly at metal surfaces. While considerable experimental effort has been put into understanding the phase diagram of these systems, theoretical work based on density functional theory (DFT) has long been hampered by the inability of conventional exchange-correlation functionals to describe dispersive interactions. In this work, we combine dispersion-corrected DFT calculations using the new vdW-DF-CX functional with the ab initio thermodynamics method to study the stability of dense standing-up and low-coverage lying-down phases on Au(111)...
June 9, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Kresimir Anic, Andrey V Bukhtiyarov, Hao Li, Christoph Rameshan, Günther Rupprechter
Clean and stable surface modifications of an iridium (100) single crystal, i.e., the (1 × 1) phase, the (5 × 1) reconstruction, and the oxygen-terminated (2 × 1)-O surface, were prepared and characterized by low energy electron diffraction (LEED), temperature-programmed desorption (TPD), infrared reflection absorption spectroscopy (IRAS) and polarization modulation IRAS (PM-IRAS). The adsorption of CO in UHV and at elevated (mbar) pressure/temperature was followed both ex situ and in situ on all three surface modifications, with a focus on mbar pressures of CO...
May 26, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Samantha J Chadwick, Dina Salah, Penelope M Livesey, Mathias Brust, Martin Volk
The formation of singlet oxygen by irradiation of gold nanoparticles in their plasmon resonance band with continuous or pulsed laser light has been investigated. Citrate-stabilized nanoparticles were found to facilitate the photogeneration of singlet oxygen, albeit with low quantum yield. The reaction caused by pulsed laser irradiation makes use of the equilibrated hot electrons that can reach temperatures of several thousand degrees during the laser pulse. Although less efficient, continuous irradiation, which acts via the short-lived directly excited primary "hot" electrons only, can produce enough singlet oxygen for photodynamic cancer therapy and has significant advantages for practical applications...
May 19, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Elyahb Allie Kwizera, Elise Chaffin, Xiao Shen, Jingyi Chen, Qiang Zou, Zhiming Wu, Zheng Gai, Saheel Bhana, Ryan O'Connor, Lijia Wang, Hitesh Adhikari, Sanjay R Mishra, Yongmei Wang, Xiaohua Huang
Magnetic-plasmonic core-shell nanomaterials offer a wide range of applications across science, engineering and biomedical disciplines. However, the ability to synthesize and understand magnetic-plasmonic core-shell nanoparticles with tunable sizes and shapes remains very limited. This work reports experimental and computational studies on the synthesis and properties of iron oxide-gold core-shell nanoparticles of three different shapes (sphere, popcorn and star) with controllable sizes (70 to 250 nm). The nanoparticles were synthesized via a seed-mediated growth method in which newly formed gold atoms were added onto gold-seeded iron oxide octahedrons to form gold shell...
May 19, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Vytenis Pranculis, Arvydas Ruseckas, Dimali A Vithanage, Gordon J Hedley, Ifor D W Samuel, Vidmantas Gulbinas
Charge separation and extraction dynamics were investigated in high-performance bulk heterojunction solar cells made from the polymer PTB7 and the soluble fullerene PC71BM on a broad time scale from subpicosecond to microseconds using ultrafast optical probing of carrier drift and the integral-mode photocurrent measurements. We show that the short circuit current is determined by the separation of charge pairs into free carriers, which is strongly influenced by blend composition. This separation is found to be efficient in fullerene-rich blends where a high electron mobility of >0...
May 12, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Joong Il Jake Choi, Wernfried Mayr-Schmölzer, Ilaria Valenti, Paola Luches, Florian Mittendorfer, Josef Redinger, Ulrike Diebold, Michael Schmid
Nucleation and growth of transition metals on zirconia has been studied by scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. Since STM requires electrical conductivity, ultrathin ZrO2 films grown by oxidation of Pt3Zr(0001) and Pd3Zr(0001) were used as model systems. DFT studies were performed for single metal adatoms on supported ZrO2 films as well as the (1̅11) surface of monoclinic ZrO2. STM shows decreasing cluster size, indicative of increasing metal-oxide interaction, in the sequence Ag < Pd ≈ Au < Ni ≈ Fe...
May 12, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Jessica K Bristow, Katrine L Svane, Davide Tiana, Jonathan M Skelton, Julian D Gale, Aron Walsh
We report an investigation of the "missing-linker phenomenon" in the Zr-based metal-organic framework UiO-66 using atomistic force field and quantum chemical methods. For a vacant benzene dicarboxylate ligand, the lowest energy charge-capping mechanism involves acetic acid or Cl(-)/H2O. The calculated defect free energy of formation is remarkably low, consistent with the high defect concentrations reported experimentally. A dynamic structural instability is identified for certain higher defect concentrations...
May 5, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
S Pomp, D Kuhness, G Barcaro, L Sementa, V Mankad, A Fortunelli, M Sterrer, F P Netzer, S Surnev
The exceptional physical properties of graphene have sparked tremendous interests toward two-dimensional (2D) materials with honeycomb structure. We report here the successful fabrication of 2D iron tungstate (FeWO x ) layers with honeycomb geometry on a Pt(111) surface, using the solid-state reaction of (WO3)3 clusters with a FeO(111) monolayer on Pt(111). The formation process and the atomic structure of two commensurate FeWO x phases, with (2 × 2) and (6 × 6) periodicities, have been characterized experimentally by combination of scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS), and temperature-programmed desorption (TPD) and understood theoretically by density functional theory (DFT) modeling...
April 14, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Hadeel Hussain, Xavier Torrelles, Gregory Cabailh, Parasmani Rajput, Robert Lindsay, Oier Bikondoa, Marcus Tillotson, Ricardo Grau-Crespo, Jörg Zegenhagen, Geoff Thornton
The positions of atoms in and around acetate molecules at the rutile TiO2(110) interface with 0.1 M acetic acid have been determined with a precision of ±0.05 Å. Acetate is used as a surrogate for the carboxylate groups typically employed to anchor monocarboxylate dye molecules to TiO2 in dye-sensitized solar cells (DSSC). Structural analysis reveals small domains of ordered (2 × 1) acetate molecules, with substrate atoms closer to their bulk terminated positions compared to the clean UHV surface. Acetate is found in a bidentate bridge position, binding through both oxygen atoms to two 5-fold titanium atoms such that the molecular plane is along the [001] azimuth...
April 14, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Nahid Ilyas, Shashank S Harivyasi, Percy Zahl, Rocio Cortes, Oliver T Hofmann, Peter Sutter, Egbert Zojer, Oliver L A Monti
In this combined low-temperature scanning tunneling microscopy (STM) and density functional theory (DFT) study, we investigate self-assembly of the dipolar nonplanar organic semiconductor chloro boron-subphthalocyanine (ClB-SubPc) on Cu(111). We observe multiple distinct adsorption configurations and demonstrate that these can only be understood by taking surface-catalyzed dechlorination into account. A detailed investigation of possible adsorption configurations and the comparison of experimental and computational STM images demonstrates that the configurations correspond to "Cl-up" molecules with the B-Cl moiety pointing toward the vacuum side of the interface, and dechlorinated molecules...
April 7, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
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