Search results for "surface"
showing 10 items of 9345 documents
Atomistic Simulations of Functional Au_{144}(SR)_{60} Gold Nanoparticles in Aqueous Environment
2012
Charged monolayer-protected gold nanoparticles (AuNPs) have been studied in aqueous solution by performing atomistic molecular dynamics simulations at physiological temperature (310 K). Particular attention has been paid to electrostatic properties that modulate the formation of a complex comprised of the nanoparticle together with surrounding ions and water. We focus on Au-144 nanoparticles that comprise a nearly spherical Au core (diameter similar to 2 nm), a passivating Au-S interface, and functionalized alkanethiol chains. Cationic and anionic AuNPs have been modeled with amine and carboxyl terminal groups and Cl-/Na+ counterions, respectively. The radial distribution functions show tha…
Selective Surface Modification of SiO2−TiO2 Supports with Phosphonic Acids
2004
The selective surface modification by phosphonic acids of SiO2−TiO2 supports at the micrometer and molecular scale was investigated. Under aqueous conditions, phosphonic acids bind to TiO2 and not to SiO2 surfaces. A micropatterned support was prepared by electron beam microlithography and selectivity, of the surface modification was evidenced using scanning Auger electron spectroscopy (SAES). The second support was a mesoporous SiO2−TiO2 mixed oxide (10 mol % Ti) epoxidation catalyst prepared by sol−gel processing. Selectivity was deduced from the decrease of the catalytic activity upon modification and from chemical analysis; bonding modes to the surface were investigated using solid-stat…
On-Surface Synthesis of Oligo(indenoindene)
2020
Fully conjugated ladder polymers (CLP) possess unique optical and electronic properties, and are considered promis-ing materials for applications in (opto)electronic devices. Poly(indenoindene) is a CLP consisting of an alternating array of five- and six-membered rings, which has remained elusive so far. Here, we report an on-surface synthesis of oligo(indenoindene) on Au(111). Its structure and a low elec-tronic bandgap have been elucidated by low-temperature scanning tunneling microscopy and spectroscopy and non-contact atomic force microscopy, complemented by density functional theory calculations. Achieving defect-free seg-ments of oligo(indenoindene) offers an exclusive insight into th…
Molecular Recognition-Induced Function and Competitive Replacement by Hydrogen-Bonding Interactions: Amphiphilic Barbituric Acid Derivatives, 2,4,6-…
1998
The phenomenon of molecular recognition inducing further function is common in nature. However, there are few synthetic systems which achieve this cascade type mechanism, and those are generally ca...
Fine tuning of the catalytic effect of a metal-free porphyrin on the homogeneous oxygen reduction.
2011
The catalytic effect of tetraphenylporphyrin on the oxygen reduction with ferrocene in 1,2-dichloroethane can be finely tuned by varying the molar ratio of the acid to the catalyst present in the solution. The mechanism involves binding of molecular oxygen to the protonated free porphyrin base, in competition with ion pairing between the protonated base and the acid anion present.
Sponge aggregation factor: identification of the specific collagen-binding site by means of a monoclonal antibody.
1988
The aggregation factor (AF) from the sponge Geodia cydonium is known to be a complex proteinaceous particle, composed of a series of different (glyco)proteins (Mr lower than 150,000) around a 90S sunburst-like core structure. One of the low-Mr proteins is the 47-KD cell binding fragment. We describe a new monoclonal antibody (mAb), III1E6, raised against purified AF particles, which recognizes in tissue slices structures present both on the plasma membrane and in a network-like manner in the extracellular space. By applying immunoelectron microscopical, immunoblotting, and immunoaffinity chromatographical techniques, the mAb III1E6 was shown to recognize the core structure of the AF partic…
Bulk and interfacial properties in colloid-polymer mixtures
2005
Large-scale Monte Carlo simulations of a phase-separating colloid-polymer mixture are performed and compared to recent experiments. The approach is based on effective interaction potentials in which the central monomers of self-avoiding polymer chains are used as effective coordinates. By incorporating polymer nonideality together with soft colloid-polymer repulsion, the predicted binodal is in excellent agreement with recent experiments. In addition, the interfacial tension as well as the capillary length are in quantitative agreement with experimental results obtained at a number of points in the phase-coexistence region, without the use of any fit parameters.
Treatment of poly(styrene-co-methacrylic acid)/poly(4-vinylpyridine) blends in solution under liquid–liquid phase-separation conditions. A new method…
2006
Phase diagrams are contributed for polymer mixture systems in solution. One polymer has proton-acceptor character and the other has growing proton-donor nature, which is reflected in the phase diagrams. Usually, these diagrams are obtained from size-exclusion chromatographic (SEC) measurements. A totally novel application, which is exposed in this report, is the construction of the phase diagram from the viscometric experiments of polymer mixtures. The evaluated binodal or cloud-point isotherms so built agree well with those from SEC. The results indicate an augmentation in the dimensions of donor polymer B, in the presence of acceptor polymer C, intensifying with the concentration of C, wh…
Simulation and theory of fluid demixing and interfacial tension of mixtures of colloids and nonideal polymers.
2005
An extension of the Asakura-Oosawa-Vrij model of hard sphere colloids and non-adsorbing polymers, that takes polymer non-ideality into account through a repulsive stepfunction pair potential between polymers, is studied with grand canonical Monte Carlo simulations and density functional theory. Simulation results validate previous theoretical findings for the shift of the bulk fluid demixing binodal upon increasing strength of polymer-polymer repulsion, promoting the tendency to mix. For increasing strength of the polymer-polymer repulsion, simulation and theory consistently predict the interfacial tension of the free colloidal liquid-gas interface to decrease significantly for fixed colloi…
Novel Polycaprolactone Nanocomposites Containing Thymol of Interest in Antimicrobial Film and Coating Applications
2008
It is well-known that the nanocomposites technology can significantly enhance, among others, the thermal, mechanical, and barrier properties of plastics. It is also known that most bioplastics, including the thermoplastic biopolymers, have lower than desired levels for certain properties which makes their use in certain packaging applications problematic. The combination of active technologies such as antimicrobials and nanotechnologies such as nanocomposites can synergistically lead to bioplastic formulations with balanced properties and functionalities for their implementation in packaging applications. The present work presents the development and characterization of novel nanocomposite…