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Journal of Physical Chemistry. C, Nanomaterials and Interfaces

Ailin Wang, Y Randika Perera, Mackenzie B Davidson, Nicholas C Fitzkee
Gold nanoparticle- (AuNP-) protein conjugates are potentially useful in a broad array of diagnostic and therapeutic applications, but the physical basis of the simultaneous adsorption of multiple proteins onto AuNP surfaces remains poorly understood. Here, we investigate the contribution of electrostatic interactions to protein-AuNP binding by studying the pH-dependent binding behavior of two proteins, GB3 and ubiquitin. For both proteins, binding to 15-nm citrate-coated AuNPs closely tracks with the predicted net charge using standard pKa values, and a dramatic reduction in binding is observed when lysine residues are chemically methylated...
October 27, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Natalie A Belsey, David J H Cant, Caterina Minelli, Joyce R Araujo, Bernd Bock, Philipp Brüner, David G Castner, Giacomo Ceccone, Jonathan D P Counsell, Paul M Dietrich, Mark H Engelhard, Sarah Fearn, Carlos E Galhardo, Henryk Kalbe, Jeong Won Kim, Luis Lartundo-Rojas, Henry S Luftman, Tim S Nunney, Johannes Pseiner, Emily F Smith, Valentina Spampinato, Jacobus M Sturm, Andrew G Thomas, Jon P W Treacy, Lothar Veith, Michael Wagstaffe, Hai Wang, Meiling Wang, Yung-Chen Wang, Wolfgang Werner, Li Yang, Alexander G Shard
We report the results of a VAMAS (Versailles Project on Advanced Materials and Standards) inter-laboratory study on the measurement of the shell thickness and chemistry of nanoparticle coatings. Peptide-coated gold particles were supplied to laboratories in two forms: a colloidal suspension in pure water and; particles dried onto a silicon wafer. Participants prepared and analyzed these samples using either X-ray photoelectron spectroscopy (XPS) or low energy ion scattering (LEIS). Careful data analysis revealed some significant sources of discrepancy, particularly for XPS...
October 27, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Battulga Munkhbat, Johannes Ziegler, Hannes Pöhl, Christian Wörister, Dmitry Sivun, Markus C Scharber, Thomas A Klar, Calin Hrelescu
Here, we report that hybrid multilayered plasmonic nanostars can be universally used as feedback agents for coherent random lasing in polar or nonpolar solutions containing gain material. We show that silver-enhancement of gold nanostars reduces the pumping threshold for coherent random lasing substantially for both a typical dye (R6G) and a typical fluorescent polymer (MEH-PPV). Further, we reveal that the lasing intensity and pumping threshold of random lasers based on silver-enhanced gold nanostars are not influenced by the silica coating, in contrast to gold nanostar-based random lasers, where silica-coated gold nanostars support only amplified spontaneous emission but no coherent random lasing...
October 20, 2016: 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
Matthew R Bailey, R Scott Martin, Zachary D Schultz
The strength of the analyte-substrate interaction is a key component when evaluating the observed enhancements in surface-enhanced Raman scattering (SERS) detection. By performing Raman and electrochemical measurements on a series of neurotransmitters, including dopamine, serotonin, norepinephrine, and epinephrine, as well as catechol as it allows us to examine the diol moiety without the side chains present, we were able to correlate surface chemistry with the measured SERS signal and examine the oxidation mechanism of each analyte...
September 22, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Xin Zhao, M H Alizadeh, Björn M Reinhard
Hybrid structures containing plasmonic and photonic components can enhance light-matter interaction through both photonic and plasmonic modes and potentially their interactions. In this article, we systematically investigate the optical properties of nanoparticle-tipped silicon nanowires (NPTWs) and characterize their ability to enhance the fluorescence signal of two cyanine dyes (Cy3 and Cy5) selectively bound to the gold tip. Although both gold and silicon components contribute to the fluorescence signal enhancement, the experimentally observed strong morphology dependence of the fluorescence emission enhancement is demonstrated to depend on tunable leaky modes of the silicon nanowires...
September 22, 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
Gilad Reut, Eitan Oksenberg, Ronit Popovitz-Biro, Katya Rechav, Ernesto Joselevich
A major challenge toward large-scale integration of nanowires is the control over their alignment and position. A possible solution to this challenge is the guided growth process, which enables the synthesis of well-aligned horizontal nanowires that grow according to specific epitaxial or graphoepitaxial relations with the substrate. However, the guided growth of horizontal nanowires was demonstrated for a limited number of materials, most of which exhibit unintentional n-type behavior. Here we demonstrate the vapor-liquid-solid growth of guided horizontal ZnTe nanowires and nanowalls displaying p-type behavior on four different planes of sapphire...
August 4, 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
Wenhui Zhu, Jonathan Winterstein, Itai Maimon, Qiyue Yin, Lu Yuan, Aleksey N Kolmogorov, Renu Sharma, Guangwen Zhou
The atomic-scale reduction mechanism of α-Fe2O3 nanowires by H2 was followed using transmission electron microscopy to reveal the evolution of atomic structures and the associated transformation pathways for different iron oxides. The reduction commences with the generation of oxygen vacancies that order onto every 10(th) [Formula: see text] plane. This vacancy ordering is followed by an allotropic transformation of α-Fe2O3 → γ-Fe2O3 along with the formation of Fe3O4 nanoparticles on the surface of the γ-Fe2O3 nanowire by a topotactic transformation process, which shows 3D correspondence between the structures of the product and its host...
July 14, 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
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