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Journal of Physical Chemistry. C, Nanomaterials and Interfaces

Danila A Barskiy, Oleg G Salnikov, Roman V Shchepin, Matthew A Feldman, Aaron M Coffey, Kirill V Kovtunov, Igor V Koptyug, Eduard Y Chekmenev
Parahydrogen-induced polarization (PHIP) is an NMR hyperpolarization technique that increases nuclear spin polarization by orders of magnitude, and it is particularly well-suited to study hydrogenation reactions. However, the use of high-field NMR spectroscopy is not always possible, especially in the context of potential industrial-scale reactor applications. On the other hand, the direct low-field NMR detection of reaction products with enhanced nuclear spin polarization is challenging due to near complete signal cancellation from nascent parahydrogen protons...
December 29, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Daniele Selli, Cristiana Di Valentin
In biomedical applications, TiO2 nanoparticles are generally coated with polymers to prevent agglomeration, improve biocompatibility, and reduce cytotoxicity. Although the synthesis processes of such composite compounds are well established, there is still a substantial lack of information on the nature of the interaction between the titania surface and the organic macromolecules. In this work, the adsorption of polyethylene glycol (PEG) on the TiO2 (101) anatase surface is modeled by means of dispersion-corrected density functional theory (DFT-D2) calculations...
December 29, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Silvio Pipolo, Stefano Corni
The optical properties of molecules close to plasmonic nanostructures greatly differ from their isolated molecule counterparts. To theoretically investigate such systems from a quantum-chemistry perspective, one has to take into account that the plasmonic nanostructure (e.g., a metal nanoparticle-NP) is often too large to be treated atomistically. Therefore, a multiscale description, where the molecule is treated by an ab initio approach and the metal NP by a lower level description, is needed. Here we present an extension of one such multiscale model [Corni, S...
December 22, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Andrea Zen, Loïc M Roch, Stephen J Cox, Xiao Liang Hu, Sandro Sorella, Dario Alfè, Angelos Michaelides
Clay minerals are ubiquitous in nature, and the manner in which they interact with their surroundings has important industrial and environmental implications. Consequently, a molecular-level understanding of the adsorption of molecules on clay surfaces is crucial. In this regard computer simulations play an important role, yet the accuracy of widely used empirical force fields (FF) and density functional theory (DFT) exchange-correlation functionals is often unclear in adsorption systems dominated by weak interactions...
November 23, 2016: 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
Kayla S B Culver, Yu Jin Shin, Matthew W Rotz, Thomas J Meade, Mark C Hersam, Teri W Odom
Gold nanostars functionalized with Gd(III) have shown significant promise as contrast agents for magnetic resonance imaging (MRI) because of their anisotropic, branched shape. However, the size and shape polydispersity of as-synthesized gold nanostars have precluded efforts to develop a rigorous relationship between the gold nanostar structure (e.g., number of branches) and relaxivity of surface-bound Gd(III). This paper describes the use of a centrifugal separation method that can produce structurally refined populations of gold nanostars and is compatible with Gd(III) functionalization...
September 29, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Marina Gühlke, Zsuzsanna Heiner, Janina Kneipp
A thiol-modified carotene, 7'-apo-7'-(4-mercaptomethylphenyl)-β-carotene, was used to obtain nonresonant surface-enhanced Raman scattering (SERS) spectra of carotene at an excitation wavelength of 1064 nm, which were compared with resonant SERS spectra at an excitation wavelength of 532 nm. These spectra and surface-enhanced hyper-Raman scattering (SEHRS) spectra of the functionalized carotene were compared with the spectra of nonmodified β-carotene. Using SERS, normal Raman, and SEHRS spectra, all obtained for the resonant case, the interaction of the carotene molecules with silver nanoparticles, as well as the influence of the resonance enhancement and the SERS enhancement on the spectra, were investigated...
September 22, 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
Fani Madzharova, Zsuzsanna Heiner, Marina Gühlke, Janina Kneipp
Using picosecond excitation at 1064 nm, surface-enhanced hyper-Raman scattering (SEHRS) spectra of the nucleobases adenine, guanine, cytosine, thymine, and uracil with two different types of silver nanoparticles were obtained. Comparing the SEHRS spectra with SERS data from the identical samples excited at 532 nm and with known infrared spectra, the major bands in the spectra are assigned. Due to the different selection rules for the one- and two-photon excited Raman scattering, we observe strong variation in relative signal strengths of many molecular vibrations obtained in SEHRS and SERS spectra...
July 21, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
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