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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
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
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
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
Swetha Barkam, Julian Ortiz, Shashank Saraf, Nicholas Eliason, Rameech Mccormack, Soumen Das, Ankur Gupta, Craig Neal, Alex Petrovici, Cameron Hanson, Michael D Sevilla, Amitava Adhikary, Sudipta Seal
In this work, we tested our hypothesis that surface chemistry and antioxidant properties of cerium nanoparticles (CNPs) are affected by presence of counterions. We first employed various precursor cerium (III) (Ce(III)) salts with different counterions (acetate, nitrate, chloride, sulfate) to synthesize CNPs following the same wet chemical methodology. Electron spin resonance (ESR) studies provided evidence for the formation of radicals from counterions (e.g., NO3•(2-) from reduction of NO3(-) in CNPs synthesized from Ce(III) nitrate)...
September 14, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Matthias Müllner, Jan Balajka, Michael Schmid, Ulrike Diebold, Stijn F L Mertens
Electrochemical surface science of oxides is an emerging field with expected high impact in developing, for instance, rationally designed catalysts. The aim in such catalysts is to replace noble metals by earth-abundant elements, yet without sacrificing activity. Gaining an atomic-level understanding of such systems hinges on the use of experimental surface characterization techniques such as scanning tunneling microscopy (STM), in which tungsten tips have been the most widely used probes, both in vacuum and under electrochemical conditions...
September 14, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Chris de Weerd, Junhao Lin, Leyre Gomez, Yasufumi Fujiwara, Kazutomo Suenaga, Tom Gregorkiewicz
Nanocrystals of all-inorganic cesium lead halide perovskites (CsPbX3, X = Cl, Br, I) feature high absorption and efficient narrow-band emission which renders them promising for future generation of photovoltaic and optoelectronic devices. Colloidal ensembles of these nanocrystals can be conveniently prepared by chemical synthesis. However, in the case of CsPbBr3, its synthesis can also yield nanocrystals of Cs4PbBr6 and the properties of the two are easily confused. Here, we investigate in detail the optical characteristics of simultaneously synthesized green-emitting CsPbBr3 and insulating Cs4PbBr6 nanocrystals...
September 7, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Jacobine J H A van Hest, Gerhard A Blab, Hans C Gerritsen, Celso de Mello Donega, Andries Meijerink
Lanthanide-doped nanocrystals (NCs) differ from their bulk counterparts due to their large surface to volume ratio. It is generally assumed that the optical properties are not affected by size effects as electronic transitions occur within the well-shielded 4f shell of the lanthanide dopant ions. However, defects and disorder in the surface layer can affect the luminescence properties. Trivalent europium is a suitable ion to investigate the subtle influence of the surface, because of its characteristic luminescence and high sensitivity to the local environment...
September 7, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Prashant Bhaskar, Alexander W Achtstein, Silke L Diedenhofen, Laurens D A Siebbeles
Trigonal selenium is a semiconducting van der Waals solid that consists of helical atomic chains. We studied the mobility and decay dynamics of excess electrons and holes moving along the selenium chains. Excess charge carriers were generated by irradiation of powdered selenium with 3 MeV electron pulses. Their mobility and decay via trapping or recombination was studied by time-resolved microwave conductivity measurements as a function of temperature. The mobility of charge carriers along the Se chains is at least ca...
August 31, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Monchai Jitvisate, James R T Seddon
The interfacial behavior of ionic liquids promises tunable lubrication as well as playing an integral role in ion diffusion for electron transfer. Diluting the ionic liquids optimizes bulk parameters, such as electric conductivity, and one would expect dilution to disrupt the near-wall molecular ordering. We study this ordering in the ionic liquids [Emim](+)[NTf2](-), [Emim](+)[DCA](-), and [C4mpyr](+)[NTf2](-), diluted in the solvent dimethyl sulfoxide. We found a structural crossover from well-ordered ionic liquids to a well-ordered solvent with increasing dilution, but this occurs nonlinearly, with solvent molecules initially space-filling and solvating and later disrupting the ionic layers...
August 31, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Boyang Liu, Matti M van Schooneveld, Yi-Tao Cui, Jun Miyawaki, Yoshihisa Harada, Thomas O Eschemann, Krijn P de Jong, Mario U Delgado-Jaime, Frank M F de Groot
In-situ carbon-thermal reduction of cobalt oxide nanoparticles supported on carbon nanotubes was studied by cobalt 2p3d resonant inelastic X-ray scattering (RIXS). The in-situ 2p X-ray absorption spectroscopy (XAS) and RIXS measurements were performed at 500, 600, and 700 °C, where four consistent excitation energies were used for RIXS acquisitions. After 700 °C reduction, the XAS spectrum shows a cobalt metal-like shape, while the RIXS spectra reveal the minority cobalt monoxide phase. The holistic fit on both XAS and RIXS data reveals the respective contributions from metal and monoxide...
August 17, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Ian J McPherson, Philip A Ash, Lewys Jones, Aakash Varambhia, Robert M J Jacobs, Kylie A Vincent
The oxidation of adsorbed CO is a key reaction in electrocatalysis. It has been studied extensively on both extended model surfaces and on nanoparticles; however, correlation between the two is far from simple. Molecular insight into the reaction is often provided using in situ IR spectroscopy; however, practical challenges mean in situ studies on nanoparticles have yet to provide the same level of detail as those on model surfaces. Here we use a new approach to in situ IR spectroscopy to study the mechanism of CO adlayer oxidation on a commercial carbon-supported Pt catalyst...
August 17, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Cheng-Yu Shih, Maxim V Shugaev, Chengping Wu, Leonid V Zhigilei
The ability of short pulse laser ablation in liquids to produce clean colloidal nanoparticles and unusual surface morphology has been employed in a broad range of practical applications. In this paper, we report the results of large-scale molecular dynamics simulations aimed at revealing the key processes that control the surface morphology and nanoparticle size distributions by pulsed laser ablation in liquids. The simulations of bulk Ag targets irradiated in water are performed with an advanced computational model combining a coarse-grained representation of liquid environment and an atomistic description of laser interaction with metal targets...
August 3, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Daniel M Dawson, Robert F Moran, Sharon E Ashbrook
NMR crystallography has recently been applied to great effect for silica zeolites. Here we investigate whether it is possible to extend the structural information available from routine NMR spectra via a simple structure-spectrum relationship. Unlike previous empirically derived relationships that have compared experimental crystal structures for (often disordered) silicates with experimental NMR spectra, where the structure may not be an accurate representation of the material studied experimentally, we use NMR parameters calculated by density functional theory (DFT) for both model Si(OSi(OH)3)4 clusters and also extended zeolitic SiO2 frameworks, for which the input structure corresponding to the NMR parameters is known exactly...
July 20, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Daniele Ongari, Davide Tiana, Samuel J Stoneburner, Laura Gagliardi, Berend Smit
The copper paddle-wheel is the building unit of many metal organic frameworks. Because of the ability of the copper cations to attract polar molecules, copper paddle-wheels are promising for carbon dioxide adsorption and separation. They have therefore been studied extensively, both experimentally and computationally. In this work we investigate the copper-CO2 interaction in HKUST-1 and in two different cluster models of HKUST-1: monocopper Cu(formate)2 and dicopper Cu2(formate)4. We show that density functional theory methods severely underestimate the interaction energy between copper paddle-wheels and CO2, even including corrections for the dispersion forces...
July 20, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Yanxi Zhang, Xinkai Qiu, Pavlo Gordiichuk, Saurabh Soni, Theodorus L Krijger, Andreas Herrmann, Ryan C Chiechi
This paper examines the relationship between mechanical deformation and the electronic properties of self-assembled monolayers (SAMs) of the oligothiophene 4-([2,2':5',2″:5″,2‴-quaterthiophen]-5-yl)butane-1-thiol (T4C4) in tunneling junctions using conductive probe atomic force microscopy (CP-AFM) and eutectic Ga-In (EGaIn). We compared shifts in conductivity, transition voltages of T4C4 with increasing AFM tip loading force to alkanethiolates. While these shifts result from an increasing tilt angle from penetration of the SAM by the AFM tip for the latter, we ascribe them to distortions of the π system present in T4C4, which is more mechanically robust than alkanethiolates of comparable length; SAMs comprising T4C4 shows about five times higher Young's modulus than alkanethiolates...
July 13, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Luuk Kortekaas, Federico Lancia, Jorn D Steen, Wesley R Browne
The coupling of substituted carbazole compounds through carbon-carbon bond formation upon one-electron oxidation is shown to be a highly versatile approach to the formation of redox polymer films. Although the polymerization of single carbazole units has been proposed earlier, we show that by tethering pairs of carbazoles double sequential dimerization allows for facile formation of redox polymer films with fine control over film thickness. We show that the design of the monomers and in particular the bridging units is key to polymer formation, with the diaminobenzene motif proving advantageous, in terms of the matching to the redox potentials of the monomer and polymer film and thereby avoiding limitations in film thickness (autoinsulation), but introduces unacceptable instability due to the intrinsic redox activity of this moiety...
July 13, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
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