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Journal of Physical Chemistry. C, Nanomaterials and Interfaces

Saskia Streubel, Felix Schulze-Zachau, Eric Weißenborn, Björn Braunschweig
Mixed layers of 6-hydroxy-5-[(4-sulfophenyl)azo]-2-naphthalenesulfonate (Sunset Yellow, SSY) and cetyltrimethylammonium bromide (C16TAB) at the air-water interface were studied using vibrational sum-frequency generation (SFG) and dynamic surface tension measurements. In the bulk, addition of C16TAB to SSY aqueous solution causes substantial changes in UV/vis absorption spectra, which originate from strong electrostatic interactions between the anionic SSY azo dye with the cationic C16TAB surfactant. These interactions are a driving force for the formation of SSY/C16TAB ion pairs...
December 21, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Jan Balajka, Ulrich Aschauer, Stijn F L Mertens, Annabella Selloni, Michael Schmid, Ulrike Diebold
The rutile TiO2(011) surface exhibits a (2 × 1) reconstruction when prepared by standard techniques in ultrahigh vacuum (UHV). Here we report that a restructuring occurs upon exposing the surface to liquid water at room temperature. The experiment was performed in a dedicated UHV system, equipped for direct and clean transfer of samples between UHV and liquid environment. After exposure to liquid water, an overlayer with a (2 × 1) symmetry was observed containing two dissociated water molecules per unit cell...
November 30, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
María C Gélvez-Rueda, Eline M Hutter, Duyen H Cao, Nicolas Renaud, Constantinos C Stoumpos, Joseph T Hupp, Tom J Savenije, Mercouri G Kanatzidis, Ferdinand C Grozema
The optoelectronic properties of hybrid perovskites can be easily tailored by varying their components. Specifically, mixing the common short organic cation (methylammonium (MA)) with a larger one (e.g., butyl ammonium (BA)) results in 2-dimensional perovskites with varying thicknesses of inorganic layers separated by the large organic cation. In both of these applications, a detailed understanding of the dissociation and recombination of electron-hole pairs is of prime importance. In this work, we give a clear experimental demonstration of the interconversion between bound excitons and free charges as a function of temperature by combining microwave conductivity techniques with photoluminescence measurements...
November 30, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Hongsheng Liu, Cristiana Di Valentin
Magnetite exhibits a famous phase transition, called Verwey transition, at the critical temperature TV of about 120 K. Although numerous efforts have been devoted to the understanding of this interesting transition, up to now, it is still under debate whether a charge ordering and a band gap exist in magnetite above TV. Here, we systematically investigate the charge ordering and the electronic properties of magnetite in its cubic phase using different methods based on density functional theory: DFT+U and hybrid functionals...
November 22, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Karen Markey, Martin Krüger, Tomasz Seidler, Helge Reinsch, Thierry Verbiest, Dirk E De Vos, Benoît Champagne, Norbert Stock, Monique A van der Veen
p-Nitroaniline presents the typical motif of a second-order nonlinear optically (NLO) active molecule. However, because of its crystallization in an antiparallel and hence centrosymmetric structure, the NLO activity is lost. In this contribution, the p-nitroaniline motif was built successfully into the MIL-53 metal-organic framework. More precisely, MIL-53 was synthesized with 2-amino-5-nitroterephthalate as organic linker, with Al(3+), Ga(3+), or In(3+) as inorganic cation. The Al and Ga structures are polar, as confirmed by second-harmonic generation microscopy, yielding stable NLO materials...
November 16, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Steven Vandenbrande, Toon Verstraelen, Juan José Gutiérrez-Sevillano, Michel Waroquier, Veronique Van Speybroeck
The search for nanoporous materials that are highly performing for gas storage and separation is one of the contemporary challenges in material design. The computational tools to aid these experimental efforts are widely available, and adsorption isotherms are routinely computed for huge sets of (hypothetical) frameworks. Clearly the computational results depend on the interactions between the adsorbed species and the adsorbent, which are commonly described using force fields. In this paper, an extensive comparison and in-depth investigation of several force fields from literature is reported for the case of methane adsorption in the Zr-based Metal-Organic Frameworks UiO-66, UiO-67, DUT-52, NU-1000, and MOF-808...
November 16, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Ru-Pan Wang, Boyang Liu, Robert J Green, Mario Ulises Delgado-Jaime, Mahnaz Ghiasi, Thorsten Schmitt, Matti M van Schooneveld, Frank M F de Groot
We show that with 2p3d resonant inelastic X-ray scattering (RIXS) we can accurately determine the charge-transfer parameters of CoF2, CoCl2, CoBr2, and CoS. The 160 meV resolution RIXS results are compared with charge-transfer multiplet calculations. The improved resolution and the direct observation of the crystal field and charge-transfer excitations allow the determination of more accurate parameters than could be derived from X-ray absorption and X-ray photoemission, both limited in resolution by their lifetime broadening...
November 16, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Andrew Mellor, David Humphrey, Chi M Yim, Chi L Pang, Hicham Idriss, Geoff Thornton
Au nanoparticles supported on reducible metal oxide surfaces are known to be active catalysts for a number of reactions including CO oxidation and hydrogen production. The exact choice of a metal oxide support has been shown to have a marked impact on activity, suggesting that interactions between Au and the support play a key role in catalysis. For TiO2, a model substrate for Au catalysis, it had been thought that bridging oxygen vacancies are involved in binding Au atoms to the (110) surface based on indirect evidence...
November 9, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
O T Hofmann, H Glowatzki, C Bürker, G M Rangger, B Bröker, J Niederhausen, T Hosokai, I Salzmann, R-P Blum, R Rieger, A Vollmer, P Rajput, A Gerlach, K Müllen, F Schreiber, E Zojer, N Koch, S Duhm
The adsorption of molecular acceptors is a viable method for tuning the work function of metal electrodes. This, in turn, enables adjusting charge injection barriers between the electrode and organic semiconductors. Here, we demonstrate the potential of pyrene-tetraone (PyT) and its derivatives dibromopyrene-tetraone (Br-PyT) and dinitropyrene-tetraone (NO2-PyT) for modifying the electronic properties of Au(111) and Ag(111) surfaces. The systems are investigated by complementary theoretical and experimental approaches, including photoelectron spectroscopy, the X-ray standing wave technique, and density functional theory simulations...
November 9, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Lorena Martín-Olivera, Dmitry G Shchukin, Gilberto Teobaldi
Magnetic hardening and generation of room-temperature ferromagnetism at the interface between originally nonmagnetic transition metals and π-conjugated organics is understood to be promoted by interplay between interfacial charge transfer and relaxation-induced distortion of the metal lattice. The relative importance of the two contributions for magnetic hardening of the metal remains unquantified. Here, we disentangle their role via density functional theory simulation of several models of interfaces between Cu and polymers of different steric hindrance, π-conjugation, and electron-accepting properties: polyethylene, polyacetylene, polyethylene terephthalate, and polyurethane...
October 26, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Chong Liu, Ionut Tranca, Rutger A van Santen, Emiel J M Hensen, Evgeny A Pidko
Zeolites are widely applied as solid acid catalysts in various technological processes. In this work we have computationally investigated how catalytic reactivity scales with acidity for a range of zeolites with different topologies and chemical compositions. We found that straightforward correlations are limited to zeolites with the same topology. The adsorption energies of bases such as carbon monoxide (CO), acetonitrile (CH3CN), ammonia (NH3), trimethylamine (N(CH3)3), and pyridine (C5H5N) give the same trend of acid strength for FAU zeolites with varying composition...
October 26, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
S Strazdaite, J Versluis, N Ottosson, Huib J Bakker
We use heterodyne-detected vibrational sum-frequency generation (HD-VSFG) to determine the orientation of the molecular plane of methylguanidinium ions at the surface of aqueous solutions. We measure the VSFG response of the symmetric and antisymmetric methyl stretch vibrations of the methylguanidinium ion with different polarization combinations. We find that for at least 50% of the methylguanidinium ions the molecular plane is at an angle >20° with respect to the surface plane. Hence, for only a minor fraction of the ions does the molecular plane have an orientation (near-)parallel to the surface plane, in contrast to the predictions of recent molecular dynamics simulation studies...
October 26, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
María C Gélvez-Rueda, Nicolas Renaud, Ferdinand C Grozema
The fundamental opto-electronic properties of organic-inorganic hybrid perovskites are strongly affected by their structural parameters. These parameters are particularly critical in formamidinium lead iodide (FAPbI3), in which its large structural disorder leads to a non-perovskite yellow phase that hinders its photovoltaic performance. A clear understanding of how the structural parameters affect the opto-electronic properties is currently lacking. We have studied the opto-electronic properties of FAPbI3 using microwave conductivity measurements...
October 26, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Andrew G M Rankin, Paul B Webb, Daniel M Dawson, Jasmine Viger-Gravel, Brennan J Walder, Lyndon Emsley, Sharon E Ashbrook
Isotopic enrichment of 29Si and DNP-enhanced NMR spectroscopy are combined to determine the detailed surface structure of a silicated alumina catalyst. The significant sensitivity enhancement provided by DNP is vital to the acquisition of multinuclear and multidimensional experiments that provide information on the atomic-level structure of the species present at the surface. Isotopic enrichment not only facilitates spectral acquisition, particularly given the low (1.5 wt %) Si loading, but also enables spectra with higher resolution than those acquired using DNP to be obtained...
October 19, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Konstantinos D Vogiatzis, Guanna Li, Emiel J M Hensen, Laura Gagliardi, Evgeny A Pidko
Identifying Cu-exchanged zeolites able to activate C-H bonds and selectively convert methane to methanol is a challenge in the field of biomimetic heterogeneous catalysis. Recent experiments point to the importance of trinuclear [Cu3(μ-O)3](2+) complexes inside the micropores of mordenite (MOR) zeolite for selective oxo-functionalization of methane. The electronic structures of these species, namely, the oxidation state of Cu ions and the reactive character of the oxygen centers, are not yet fully understood...
October 12, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
May S Maung, Young-Seok Shon
This article presents the systematic evaluation of colloidal palladium nanoparticles functionalized with well-defined small organic ligands that provide spatial control of the geometric and electronic surface properties of nanoparticle catalysts. Palladium nanoparticles stabilized with thiolate ligands of different structures and functionalities (linear alkyl vs cyclohexyl vs phenyl) are synthesized using the thiosulfate protocol in a two-phase system. The structure and composition of palladium nanoparticles are characterized using transmission electron microscopy, thermogravimetric analysis, NMR, and UV-vis spectroscopies...
September 28, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Pengyu Lv, Hai Le The, Jan Eijkel, Albert Van den Berg, Xuehua Zhang, Detlef Lohse
Whereas bubble growth out of gas-oversatured solutions has been quite well understood, including the formation and stability of surface nanobubbles, this is not the case for bubbles forming on catalytic surfaces due to catalytic reactions, though it has important implications for gas evolution reactions and self-propulsion of micro/nanomotors fueled by bubble release. In this work we have filled this gap by experimentally and theoretically examining the growth and detachment dynamics of oxygen bubbles from hydrogen peroxide decomposition catalyzed by gold...
September 28, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
A D Pathak, I Tranca, S V Nedea, H A Zondag, C C M Rindt, D M J Smeulders
Chloride-based salt hydrates form a promising class of thermochemical materials (TCMs), having high storage capacity and fast kinetics. In the charging cycles of these hydrates however hydrolysis might appear along with dehydration. The HCl produced during the hydrolysis degrades and corrodes the storage system. Our GGA-DFT results show that the enthalpy charge during proton formation (an important step in hydrolysis) is much higher for CaCl2·2H2O (33.75 kcal/mol) than for MgCl2·2H2O (19.55 kcal/mol). This is a strong indicator that hydrolysis can be minimized by appropriate chemical mixing of CaCl2 and Mg Cl2 hydrates, which is also confirmed by recent experimental studies...
September 28, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Esmail A Elbassal, Clifford Morris, Thomas W Kent, Richard Lantz, Bimlesh Ojha, Ewa P Wojcikiewicz, Deguo Du
The process of amyloid-β (Aβ) amyloid formation is pathologically linked to Alzheimer's disease (AD). The identification of Aβ amyloids and intermediates that are crucial players in the pathology of AD is critical for exploring the underlying mechanism of Aβ aggregation and the diagnosis of the disease. Herein, we performed a gold nanoparticle (AuNP)-based study to detect the formation of Aβ amyloid fibrils and oligomers. Our results demonstrate that the intensity of the surface plasmon resonance (SPR) absorption band of the AuNPs is sensitive to the quantity of Aβ40 amyloids...
September 14, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Marlous Kamp, Giuseppe Soligno, Fabian Hagemans, Bo Peng, Arnout Imhof, René van Roij, Alfons van Blaaderen
Nucleation-and-growth processes are used extensively in the synthesis of spherical colloids, and more recently regiospecific nucleation-and-growth processes have been exploited to prepare more complex colloids such as patchy particles. We demonstrate that surface geometry alone can be made to play the dominant role in determining the final particle geometry in such syntheses, meaning that intricate chemical surface patternings are not required. We present a synthesis method for "lollipop"-shaped colloidal heterodimers (patchy particles), combining a recently published nucleation-and-growth technique with our recent findings that particle geometry influences the locus of droplet adsorption onto anisotropic template particles...
September 14, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
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