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Langmuir: the ACS Journal of Surfaces and Colloids

Ross J Verploegh, Ying Wu, David S Sholl
The rates of adsorbate diffusion in zeolitic imidazolate frameworks (ZIFs) can be varied by several orders of magnitude by incorporating two different imidazolate linkers in the ZIF crystals. Although some prior measurements of short-range order in these mixed-linker materials have been reported, it is unclear how this short-range order impacts the net diffusion of adsorbates. We introduce a lattice diffusion model that treats diffusion in ZIF-8x-90100-x crystals as a series of activated hops between cages, allowing us to assess the effects of short-range imidazolate order on molecular diffusion...
June 23, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Ian T McCrum, Michael A Hickner, Michael J Janik
Platinum is a widely used catalyst in aqueous and electrochemical environments. The size and shape of Pt nanoparticles and the faceting (and roughness) of extended Pt surfaces change during use in these environments due to dissolution, growth, and reconstruction. Further, many Pt nanoparticle synthesis techniques are carried out in an aqueous environment. The surface structures formed are impacted by the relative surface energies of the low index facets in these environments. Density functional theory is used to calculate the surface energy of the low index facets of platinum as a function of electrochemical potential and coverage of adsorbed hydrogen, hydroxide, oxygen, and the formation of surface oxide in an aqueous environment...
June 22, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Zhendong Li, Yanfeng Liu, Kai-Cheng Zhang, Zhao-Wei Wang, Peng Huang, Dahua Li, Yi Zhou, Bo Song
In order to provide orthogonal solvent processible surface modification and improve device stability of bulk-heterojunction polymer solar cells (PSCs), n-type semiconducting material naphthalene diimide (NDI) was chemically introduced on ITO surface as cathode interlayer (CIL) using 3-bromopropyltrimethoxysilane (BrTMS) as coupling agent. After modification, the work function of ITO can be decreased from 4.70 eV to 4.23 eV. The modified ITO cathode was applied in inverted PSCs based on PTB7-Th:PC71BM. With the CIL modification, a champion power conversion efficiency (PCE) of 5...
June 22, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Saim Özkar, Richard G Finke
The question is addressed if dust is kinetically important in the nucleation and growth of Ir(0)n nanoparticles formed from [Bu4N]5Na3(1,5-COD)Ir(I)·P2W15Nb3O62 (hereafter [(COD)Ir·POM](8-)), reduced by H2 in propylene carbonate solvent. Following a concise review of the (often-neglected) literature addressing dust in nucleation phenomena dating back to the late 1800s, the nucleation and growth kinetics of the [(COD)Ir·POM](8-) precatalyst system are examined for the effects of 0.2 μm microfiltration of the solvent and precatalyst solution, of rinsing the glassware with that microfiltered solvent, of silanizing the glass reaction vessel, for the addition of <0...
June 22, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Madhu Ranjan Gunjan, Rishi Raj
The spatio-temporal evolution of an evaporating sessile droplet and its effect on lifetime is crucial to various disciplines of science and technology. While experimental investigations suggest three distinct modes through which a droplet evaporates, namely, the constant contact radius (CCR), the constant contact angle (CCA), and the mixed, only the CCR and the CCA modes have been modeled reasonably. Here we use experiments with water droplets on flat and micropillared silicon substrates to characterize the mixed mode...
June 22, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Anne Büngeler, Benjamin Hämisch, Klaus Huber, Wolfgang Bremser, Oliver Ingolf Strube
The final step in the supramolecular buildup of eumelanin particles is investigated regarding involved species and mechanism. Time resolved in situ light scattering and scanning electron microscopy reveal an aggregation of particles with narrow size distribution around 40 nm, previously only observed as substructures. These form larger particles with again very uniform size and diameters around 200 nm. Aggregation of each single particle takes only a few minutes to complete, whereas the entire process goes on for at least three hours, partly due to kinetics of the precursors...
June 22, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Yan Zhang, Peng-Fei Yin, Xiao-Hua Liu, Jing Mao, Sergei A Kulinich, Xi-Wen Du
Owing to their high extinction coefficient and moderate band gap, cadmium chalcogenides are known as common semiconductors for photoelectric conversion. Nevertheless, no ideal cadmium chalcogenide with proper band structure is available yet for photoelectrochemical hydrogen evolution. In this work, we modified the band structure of CdTe via alloying with Se to achieve a ternary compound (CdSe0.8Te0.2) with n-type conduction, a narrower band gap, and a more negative band position compared to those of CdSe and CdTe...
June 22, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
M Teresa Garcia, Isabel Ribosa, Lourdes Perez, Angeles Manresa, Francesc Comelles
Imidazolium-based ionic liquids (ILs) containing cleavable carbonate linkages, 1-alkyloxycarbonyloxyethyl-3-methylimidazolium chlorides with alkyl chains of 10, 12, and 14 carbon atoms, were synthesized, and their self-assembly behavior and antimicrobial activity were investigated. Differential scanning calorimetry and polarized optical microscopy studies reveal that carbonate-functionalized ILs form stable thermotropic smectic liquid-crystalline phases over a wide range of temperature. The surface activity and aggregation behavior of these new ILs were investigated by tensiometry, conductometry, potentiometry, and spectrofluorimetry...
June 22, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Sirimuvva Tadepalli, Zheyu Wang, Keng-Ku Liu, Qisheng Jiang, Joseph Slocik, Rajesh R Naik, Srikanth Singamaneni
The physicochemical properties of abiotic nanostructures determine the structure and function of biological counterparts in biotic-abiotic nanohybrids. A comprehensive understanding of the interfacial interactions and the predictive capability of their structure and function is paramount for virtually all fields of bionanotechnology. In this study, using plasmonic nanostructures as a model abiotic system, we investigate the effect of the surface charge of nanostructures on the biocatalytic reaction kinetics of a bound enzyme...
June 22, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Daniel G Gregory, Qianying Guo, Li Lu, Christopher J Kiely, Mark A Snyder
Convectively assembled colloidal crystal templates, composed of size-tunable (ca. 15-50 nm) silica (SiO2) nanoparticles, enable versatile sacrificial templating of three-dimensionally ordered mesoporous (3DOm) metal oxides (MOx) at both mesoscopic and microscopic size scales. Specifically, we show for titania (TiO2) and zirconia (ZrO2) how this approach not only enables the engineering of the mesopore size, pore volume, and surface area but can also be leveraged to tune the crystallite polymorphism of the resulting 3DOm metal oxides...
June 22, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Hyun Deog Yoo, Sang-Don Han, Igor L Bolotin, Gene M Nolis, Ryan D Bayliss, Anthony K Burrell, John T Vaughey, Jordi Cabana
The energy density of rechargeable batteries utilizing metals as anodes surpasses Li-ion batteries, which employ carbon instead. Among possible metals, magnesium represents a potential alternative to the conventional choice, lithium, in terms of storage density, safety, stability, and cost. However, a major obstacle for metal-based batteries is the identification of electrolytes that show reversible deposition/dissolution of the metal anode and support reversible intercalation of ions into a cathode. Traditional Grignard-based Mg electrolytes are excellent toward reversible deposition of Mg, but their limited anodic stability and compatibility with oxide cathodes hinder their applicability in Mg batteries with higher voltage...
June 21, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Laura C Merrill, Jennifer L Schaefer
Magnesium batteries are a promising alternative to lithium-ion batteries due to the widespread abundance of magnesium and its high specific volumetric energy capacity. Ethereal solvents such as tetrahydrofuran (THF) are commonly used for magnesium-ion electrolytes due the chemical compatibility with magnesium metal, but the volatile nature of THF is a concern for practical application. Herein, we investigate magnesium bis(hexamethyldisilazide) plus aluminum chloride (Mg(HMDS)2-AlCl3) electrolytes in THF, diglyme, and tetraglyme at varying temperature...
June 21, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Daniele Ongari, Peter G Boyd, Senja Barthel, Matthew Witman, Maciej Haranczyk, Berend Smit
Pore volume is one of the main properties for the characterization of microporous crystals. It is experimentally measurable and it can also be obtained from the refined unit cell by a number of computational techniques. In this work we assess the accuracy and the discrepancies between the different computational methods which are commonly used for this purpose, i.e, geometric, helium and probe center pore volume, by studying a database of more than 5000 frameworks. We developed a new technique to fully characterize the internal void of a microporous material and to compute the probe accessible and occupiable pore volume...
June 21, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Bin He, Ren Liu, Jiabin Ren, Caijian Tang, Yijun Zhong, Yong Hu
Metal ion doping and nanocoating to CdS photocatalyst have been proved to be effective strategies to inhibit photocorrosion and improve photocatalytic performance. In this study, carbon-coated Cu+-doped CdS nanocomposites (C-Cu-CdS) with a stable petalous structure and highly uniform size distribution were successfully synthesized via a facile one-step solvothermal method. Both Cu+ doping and carbon coating to the CdS photocatalyst are realized in this one-step strategy. Benefiting from the unique core-shell structure and metal ion doping, the as-prepared C-Cu-CdS catalyst exhibits significantly enhanced photostability and visible-light-driven photocatalytic efficiency...
June 21, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Victoria A Nikitina, Maxim V Zakharkin, Sergey Yu Vassiliev, Lada V Yashina, Evgeny V Antipov, Keith J Stevenson
The charge transfer kinetics of lithium ion intercalation into LixMn2O4 cathode materials was examined in dilute and concentrated aqueous and carbonate LiTFSI solutions using electrochemical methods. Distinctive trends in ion intercalation rates were observed between water-based and ethylene carbonate/diethyl carbonate solutions. The influence of the solution concentration on the rate of lithium ion transfer in aqueous media can be tentatively attributed to the process associated with Mn dissolution, while in carbonate solutions the rate is influenced by the formation of a concentration-dependent solid electrolyte interface (SEI)...
June 21, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Jessica Davis, Aaron M Chalifoux, Stephanie L Brock
Oxidative assembly of metal chalcogenide nanocrystals (NCs) enables formation of 2-D (dense) and 3-D porous structures without the presence of intervening ligands between particles that can moderate transport properties. This route has been demonstrated successful for a range of single component structures including CdQ, PbQ and ZnQ (Q = S, Se, Te). En route to controllable assembly of multicomponent nanostructures, the roles of Q redox properties (2Q2-  Q22- + 2e), responsible for particle crosslinking, and the native structure (cubic zinc blende vs...
June 21, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Tooba Shoaib, Prathima Chandra Nalam, Yichen He, Yuting Chen, Rosa M Espinosa-Marzal
Recognizing the limitations of solid-supported lipid bilayers to reproduce the behavior of cell membranes, including bendability, transmembrane protein inclusion and virus entry, this study describes a novel biomimetic system for cell membranes with the potential to overcome these and other limitations. The developed strategy utilizes a hydrogel with tunable mechanical behavior that resembles those of living cells as the soft support for the phospholipid bilayer, while a polyelectrolyte multilayer film serves as an intermediate layer to facilitate the self-assembly of the lipid bilayer on the soft cushion...
June 21, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Rahul Jain, Ranga Pitchumani
This paper presents a fractal model to describe wettability on multiscale randomly rough surfaces. Hydrophobic or superhydrophobic surfaces produced using processes such as electrodeposition and etching lead to the creation of random roughness at multiple length scales on the surface. This paper considers the description of such surfaces with a fractal asperity model based on the Weierstrass-Mandelbrot (W-M) function, where the fractal parameters are uniquely determined from a power spectrum of the surface...
June 21, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Sabrina Valetti, Adam Feiler, Martin Trulsson
We develop and combine a novel numerical model, within the Poisson-Boltzmann frame- work, with classical experimental titration techniques for mesoporous silica particles to study the charging behavior as both pH and the amount of monovalent salt are varied. One key finding is that these particles can be considered to have an effectively or apparent electroneutral inner core with an effectively charged rim. As a consequence, the total apparent charge of the particle is several orders of magnitude smaller than that of the bare silica charge, which accounts only for the charged silanol groups of the mesoporous silica particles and which has its major contribution from the interior...
June 21, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Ali Saad, Christian Vard, Manef Abderrabba, Mohamed Mehdi Chehimi
Noble and precious metal catalysts are sought for their remarkable efficiency in catalyzing numerous reactions in heterogeneous phase. However, they are costly and request the development of high surface area supports that favor their strong immobilization, dispersion and stability. Towards this end, mesoporous silica-based materials can be regarded as unique supports for nanometric-sized noble metal catalysts provided they are functionalized with appropriate ligands. In this work, mesoporous silica SBA-15 was prepared and modified with 3-azidopropyltriethoxysilane then clicked with alkyne derivatives of 1,3,5-triazines complex ligand...
June 21, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
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