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Molecular adsorbant

Elisabeth Therese Ulrikkeholm, Martin Hangaard Hansen, Jan Rossmeisl, Ib Chorkendorff
Gd modified Pt(111) single crystals have been prepared in an ultra high vacuum (UHV). By vacuum deposition of ∼200 Å Gd on a sample heated to 800 °C, a Pt5Gd alloy terminated by a single atomic layer of Pt was formed. Subsequently the surfaces were characterized using low energy electron diffraction (LEED), showing that a highly ordered crystal structure had appeared. To study the molecular dynamics on this surface a detailed study of the CO adsorption on the surface was conducted using temperature programmed desorption (TPD) of CO...
October 19, 2016: Physical Chemistry Chemical Physics: PCCP
Anna L Calkins, Jennifer Yin, Jacenda L Rangel, Madeleine R Landry, Amelia A Fuller, Grace Y Stokes
The first report of a water-soluble peptoid adsorbed to silica monitored by second harmonic generation (SHG) at the liquid/solid interface is presented here. The molecular insights gained from these studies will inform the design and preparation of novel peptoid coatings. Simple 6- and 15-residue peptoids were dissolved in phosphate buffered saline and adsorbed to bare silica surfaces. Equilibrium binding constants and relative surface concentrations of adsorbed peptoids were determined from fits to the Langmuir model...
October 18, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Mark J DelloStritto, James David Kubicki, Jorge Osvaldo Sofo
We use ab-initio molecular dynamics simulations to study the effect of ions on the structure and dynamics of the quartz(101)-water interface. We study several IA (Na(+),Rb(+)) and IIA (Mg(2+),Sr(2+)) cations, with Cl(-) as counterion, adsorbed onto acidic, neutral, and basic surface configurations at 300K and 373K. We find that both cations and anions can bond directly to the surface and perturb the local H-bond network. The adsorbed ions promote the formation of intrasurface H-bonds, as shown by vibrational density of states and orientations of the surface silanols...
October 18, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
He Wang, Yongfeng Jia
The bioavailability of heavy metals strongly depends on their speciation in the environment. Adsorption (ADS) and coprecipitation (CPT) on amorphous metal hydroxides are important processes, controlling the fates of heavy metals in an aqueous environment. This work studied the bioavailability of Cu, Cd, Ni, and Pb adsorbed on and/or coprecipitated with amorphous iron and iron/aluminum mixed hydroxides to the wetland plant Phragmites australis. After a 13-day treatment, there was an apparent uptake of the heavy metals by the plant, and the amount of metal bioaccumulation was measurably different for different association forms (ADS vs...
October 18, 2016: Environmental Science and Pollution Research International
Shenli Zhang, Maria Perez-Page, Kelly Guan, Erick Yu, Joseph W Tringe, Ricardo H R Castro, Roland Faller, Pieter Stroeve
Molecular Dynamics (MD) and Monte Carlo (MC) simulations were applied together for the first time to reveal the porous structure transformation mechanisms of mesoporous silica MCM-41 subjected to temperatures up to 2885 K. Silica was experimentally characterized to inform the models and enable prediction of changes in gas adsorption/separation properties. MD simulations suggest that the pore closure process is activated by a collective diffusion of matrix atoms into the porous region, accompanied by bond reformation at the surface...
October 17, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Shiladitya Chatterjee, George H Major, Barry M Lunt, Massoud Kaykhaii, Matthew R Linford
Resist lithography is an important microfabrication technique in the electronics industry. In this, patterns are transferred by irradiation onto a photosensitive polymer. SU-8 has emerged as a favorite photoresist for High Aspect Ratio (HAR) lithography, showing high chemical and mechanical stability and biocompatibility. Unfortunately, its poor adhesion to substrates is a drawback, with possible solutions being the use of low-viscosity SU-8, surface modification with a low molecular weight adsorbate like hexamethyldisilazane (HMDS), or a commercial adhesion promotion reagent...
October 17, 2016: Microscopy and Microanalysis
Parnia Abyar Ghamsari, Milad Nouraliei, Sara Soleimani Gorgani
Adsorption of hydrogen (H2) and nitrogen (N2) molecules was analyzed on a new fullerene-like C16Mg8O8 nano-cage, composed of magnesium, oxygen, and carbon, using density functional theory. A detailed analysis of the energy, geometry, and electronic structure of various H2 and N2 adsorptions on the cluster surface was performed. The adsorption energies of H2 and N2 were estimated to ranging from -0.16 to -0.52eV, respectively. The most stable adsorption configurations were those in which the H or N atoms of the adsorbates were located near the Mg atom of the cluster surface at different sides...
August 13, 2016: Journal of Molecular Graphics & Modelling
Wei-Yuan Wang, Xiu-Fen Zhao, Xiao-Han Ju, Yu Wang, Lin Wang, Shu-Ping Li, Xiao-Dong Li
A novel morphology change of Au-methotrexate (Au-MTX) conjugates that could transform from nanochains to discrete nanoparticles was achieved by a simple, one-pot, and hydrothermal growth method. Herein, MTX was used efficiently as a complex-forming agent, reducing agent, capping agent, and importantly a targeting anticancer drug. The formation mechanism suggested a similarity with the molecular imprinting technology. The Au-MTX complex induced the MTX molecules to selectively adsorb on different crystal facets of gold nanoparticles (AuNPs) and then formed gold nanospheres...
October 12, 2016: International Journal of Pharmaceutics
Han Lu, Li Xiang, Xin Cui, Jing Liu, Yinan Wang, Ravin Narain, Hongbo Zeng
In this study, poly(2-lactobionamidoethyl methacrylamide) (PLAEMA) with various molecular weights (MW) were synthesized by conventional free-radical polymerization. The effect of molecular weight and polymer dosage on the settling rate of kaolin particles, the turbidity of supernatant, mud-line position, and solid content were investigated to determine the flocculation performance. The interaction forces, polymer conformation, particle sizes and molecular weights were determined by several techniques, including surface forces apparatus (SFA), atomic force microscopy (AFM), dynamic light scattering (DLS), and gel permeation chromatography (GPC)...
October 14, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Vanessa J Bukas, Karsten Reuter
We augment ab initio molecular dynamics simulations with a quantitative account of phononic dissipation to study the hyperthermal adsorbate dynamics resulting from a noninstantaneous energy dissipation during exothermic surface chemical reactions. Comparing the hot adatom diffusion ensuing O_{2} dissociation over Pd(100) and Pd(111) we find experimentally accessible product end distances to form a rather misleading measure for the lifetime of this hyperthermal state. The lifetime is particularly long at Pd(111) where a random-walk-type diffusion leads only to small net displacements...
September 30, 2016: Physical Review Letters
Francia C Díaz, Esteban Sáez-González, Salvador Benlloch, Diego Álvarez-Sotomayor, Isabel Conde, Begoña Polo, María García, María Rodríguez, Martín Prieto
:  Background and aims. Steroid-related hepatotoxicity has become one of the most relevant causes of drug induced liver cholestasis. Some patients do not improve after standard medical treatment (SMT) and may therefore require other approaches, like extracorporeal liver support. MATERIAL AND METHODS: We report four cases of patients with pruritus, abnormal liver function tests and biopsy-proven anabolic steroid-induced cholestasis who were unresponsive to SMT. They underwent treatment with albumin dialysis (Molecular Adsorbent Recirculating System -MARS®-)...
November 2016: Annals of Hepatology
Nathan D Rudd, Hao Wang, Erika M A Fuentes-Fernandez, Simon J Teat, Feng Chen, Gene Stephen Hall, Yves J Chabal, Jing Li
We have designed and synthesized an isoreticular series of luminescent metal-organic frameworks (LMOFs) by incorporating a strongly emissive molecular fluorophore and functionally diverse co-linkers into Zn-based structures. The three-dimensional porous networks of LMOF-261, -262 and -263 represent a unique/new type of nets, classified as a 2-nodal, (4,4)-c net (mot-e type) with four-fold, class IIIa interpenetration. All compounds crystallize in body-centered tetragonal crystal system (space group I41/a). A systematic study has been implemented to analyze their interactions with heavy metals...
October 13, 2016: ACS Applied Materials & Interfaces
Kyeounghak Kim, Jeong Woo Han
Caffeic acid (CA) is well known for its strong adsorption on metal or metal oxide surfaces mostly due to the catecholic functional group. On the other hand, the detailed adsorption configurations and the effects of functional groups on molecular adsorption have not been clarified yet. In this study, first-principles calculations were implemented to elucidate the adsorption phenomena of CA and its deprotonated forms on Au(100), (110) and (111), and then predict the morphology of Au nanoparticles (AuNPs). The adsorption energetics and configurations were carefully examined by employing van der Waals interactions to take dispersion forces into consideration...
October 12, 2016: Physical Chemistry Chemical Physics: PCCP
Fanny Hiebel, Bonggeun Shong, Wei Chen, Robert J Madix, Efthimios Kaxiras, Cynthia M Friend
Weak inter-adsorbate interactions are shown to play a crucial role in determining surface structure, with major implications for its catalytic reactivity. This is exemplified here in the case of acetate bound to Au(110), where the small extra energy of the van der Waals interactions among the surface-bound groups drives massive restructuring of the underlying Au. Acetate is a key intermediate in electro-oxidation of CO2 and a poison in partial oxidation reactions. Metal atom migration originates at surface defects and is likely facilitated by weakened Au-Au interactions due to bonding with the acetate...
October 12, 2016: Nature Communications
Paolo Restuccia, Mauro Ferrario, Pier Luigi Sivestrelli, Giampaolo Mistura, Maria Clelia Righi
Recent nanofriction experiments of xenon on graphene revealed that the slip onset can be induced by increasing the adsorbate coverage above a critical value, which depends on temperature. Moreover, the xenon slippage on gold is much higher than on graphene in spite of the same physical nature of the interactions. To shed light on these intriguing results we have performed molecular dynamics simulations relying on ab initio derived potentials. By monitoring the interfacial structure factor as a function of coverage and temperature, we show that the key mechanism to interpret the observed frictional phenomena is the size-dependence of the island commensurability...
October 11, 2016: Physical Chemistry Chemical Physics: PCCP
Simone Marocchi, Andrea Candini, David Klar, Willem Van den Heuvel, Haibei Huang, Filippo Troiani, Valdis Corradini, Roberto Biagi, Valentina De Renzi, Svetlana Klyatskaya, Kurt Kummer, Nicholas B Brookes, Mario Ruben, Heiko Wende, Umberto Del Pennino, Alessandro Soncini, Marco Affronte, Valerio Bellini
We investigate the electronic and magnetic properties of \ce{TbPc2} single ion magnets adsorbed on a graphene/Ni(111) substrate, by density-functional theory (DFT), ab-initio complete active space self-consistent field calculations, and x-ray magnetic circular dichroism (XMCD) experiments. Despite the presence of the graphene decoupling layer a sizable antiferromagnetic coupling between Tb and Ni is observed in the XMCD experiments. The molecule-surface interaction is rationalized by the DFT analysis and is found to follow a relay-like communication pathway, where the radical spin on the organic Pc ligands mediates the interaction between Tb ion and Ni substrate spins...
October 11, 2016: ACS Nano
Najam U Qadir, Syed A M Said, Rached B Mansour, Khalid Mezghani, Anwar Ul-Hamid
Conventional small-scale adsorption chillers generally employ silica-gel/water or zeolite/water working pairs given the relatively high level of mesoporosity and water affinity in these adsorbent materials. However, the coefficient of performance (COP) and specific cooling power (SCP) evaluated for the adsorption chiller using these adsorbent/adsorbate pairs cannot be still considered practically feasible in the context of a commercial system. Metal organic frameworks (MOFs) are not only characterized by much higher water adsorption capacities than these materials, but also can be mass-produced using much simpler methods than the template-assisted synthesis routes of most zeolites...
October 4, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Ling Zhang, Jens Ulstrup, Jingdong Zhang
DNA quadruplexes (qs) are a class of "non-canonical" oligonucleotides (OGNs) composed of stacked guanine (G) quartets stabilized by specific cations. Metal porphyrins selectively bind to G-qs complexes to form what is known as DNAzyme, which can exhibit peroxidase and other catalytic activity similar to heme group metalloenzymes. In the present study we investigate the electrochemical properties and the structure of DNAzyme monolayers on single-crystal Au(111)-electrode surfaces using cyclic voltammetry and scanning tunnelling microscopy under electrochemical potential control (in situ STM)...
September 20, 2016: Faraday Discussions
K M O'Donnell, H Hedgeland, G Moore, A Suleman, M Siegl, L Thomsen, O Warschkow, S R Schofield
In this work we combine scanning tunneling microscopy, near-edge X-ray absorption fine structure spectroscopy, X-ray photoemission spectroscopy and density functional theory to resolve a long-standing confusion regarding the adsorption behaviour of benzonitrile on Si(001) at room temperature. We find that a trough-bridging structure is sufficient to explain adsorption at low coverages. At higher coverages when steric hindrance prevents the phenyl ring lying flat on the surface, the 2+2 cycloaddition structure dominates...
October 5, 2016: Physical Chemistry Chemical Physics: PCCP
Andrew G Stack, Jose M Borreguero, Timothy R Prisk, Eugene Mamontov, Hsiu-Wen Wang, Lukas Vlcek, David J Wesolowski
Solvent exchanges on solid surfaces and dissolved ions are a fundamental property important for understanding chemical reactions, but the rates of fast exchanges are poorly constrained. We probed the diffusional motions of water adsorbed onto nanoparticles of the mineral barite (BaSO4) using quasi-elastic neutron scattering (QENS) and classical molecular dynamics (MD) to reveal the complex dynamics of water exchange along mineral surfaces. QENS data as a function of temperature and momentum transfer (Q) were fit using scattering functions derived from MD trajectories...
October 10, 2016: Physical Chemistry Chemical Physics: PCCP
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