Search results for "force microscopy"

Invasive Observation by Atomic Force Microscope of a Langmuir-Blodgett Monolayer of Gramicidin

2002

The properties of gramicidin, a linear antibiotic polypeptide of 15 amino acids, have been studied at the air-water interface. Analysis of the pressure-area isotherm is not able to conclude about the conformational behavior of gramicidin in the monolayer. Langmuir-Blodgett deposition of gramicidin layers onto a mica substrate has been developed for atomic force microscopy (AFM) observations. At high pressure of deposition, the gramicidin monolayer is composed of dimers perpendicular to the surface. The possibility of removing the half upper part of this dimer monolayer with the AFM tip is more in favor of a structure of single-stranded helical dimers.

Relating morphology to nanoscale mechanical properties: from crystalline to mesomorphic iPP

2005

Discotic Twin and Triple Molecules with Charge-Transfer Interactions in Langmuir−Blodgett Films

1996

X-ray and atomic force microscopy observations reveal features of the surface morphology of Langmuir-Blodgett (LB) films from discotic donor-acceptor molecules with strong core-to-core interactions caused by a charge-transfer (CT) complexation. The compounds are designed to be twin and triple molecules composed of chemically connected donor (triphenylene) and acceptor (trinitrofluorenone) fragments which display liquid crystalline structure in the bulk state. The LB films from these compounds possess edge-on orientation of molecules within monolayers with a smooth surface on a submicron scale but with substantial macroscopic imperfections. These imperfections are represented by the micron s…

Templating: Substrate Templating upon Self-Assembly of Hydrogen-Bonded Molecular Networks on an Insulating Surface (Small 19/2012)

2012

Electric and elastic properties of conductive polymeric nanocomposites on macro- and nanoscales

2002

Abstract In the past several years, the macroscopic electric and elastic properties of conductive polymeric composites have been studied from the viewpoint of such applications as thermistors and pressure sensors. In particular, we studied carbon black (CB) polymeric nanocomposites on macro- and nanoscales, using polyisoprene as the composite matrix. The filler component was an extra conductive carbon black (PRINTEX XE2, DEGUSSA) with a primary particle diameter of about 30 nm. A very strong reversible tensoresistive effect of electric resistance dependence on uniaxial tension deformation was observed in composites with the 10 carbon black mass parts added to 100 mass parts of polyisoprene.…

Chemical Identification at the Solid–Liquid Interface

2017

Solid-liquid interfaces are decisive for a wide range of natural and technological processes, including fields as diverse as geochemistry and environmental science as well as catalysis and corrosion protection. Dynamic atomic force microscopy nowadays provides unparalleled structural insights into solid-liquid interfaces, including the solvation structure above the surface. In contrast, chemical identification of individual interfacial atoms still remains a considerable challenge. So far, an identification of chemically alike atoms in a surface alloy has only been demonstrated under well-controlled ultrahigh vacuum conditions. In liquids, the recent advent of three-dimensional force mapping…

Where Is the Most Hydrophobic Region? Benzopurpurine Self-Assembly at the Calcite–Water Interface

2017

Control of molecular self-assembly at solid–liquid interfaces is challenging due to the complex interplay between molecule–molecule, molecule–surface, molecule–solvent, surface–solvent, and solvent–solvent interactions. Here, we use in-situ dynamic atomic force microscopy to study the self-assembly of Benzopurpurine 4B into oblong islands with a highly ordered inner structure yet incommensurate with the underlying calcite (10.4) surface. Molecular dynamics and free energy calculations provide insights by showing that Benzopurpurine 4B molecules do not anchor to the surface directly but instead assemble on top of the second hydration layer. This seemingly peculiar behavior was then rationali…

Stabilization of Polar Step Edges on Calcite (10.4) by the Adsorption of Congo Red

2015

In this work, we present the stabilization of polar step edges along the [010] direction of calcite (10.4) by the presence of a water-soluble organic molecule, namely Congo Red. While characteristic etch pits are observed on the surface in the absence of the additive, no etch pits can be found in the presence of the additive. Using atomic force microscopy, we can directly follow the restructuring of the surface. Upon addition of Congo Red, the charge-neutral step edges confining the characteristic etch pits vanish, while polar step edges along the [010] direction appear on the surface, which are entirely decorated by well-ordered molecular islands of the additive. After the restructuring ha…

Structure-Dependent Dissolution and Restructuring of Calcite Surfaces by Organophosphonates

2017

Organophosphonates are well-known to strongly interact with the surfaces of various minerals, such as brucite, gypsum, and barite. In this work, we study the influence of six systematically varied organophosphonate molecules (tetraphosphonates and diphosphonates) on the dissolution process of the (10.4) surface of calcite. In order to pursue a systematic study, we have selected organophosphonates that exhibit similar structural features, but also systematic architectural differences. The effect of this class of additives on the dissolution process of the calcite (10.4) surface is evaluated using in situ dynamic atomic force microscopy. For all of the six organophosphonate derivatives, we ob…

Deposition order controls the first stages of a metal-organic coordination network on an insulator surface

2016

| openaire: EC/FP7/610446/EU//PAMS We report on first stages toward the formation of a surface-confined metal-organic coordination network (MOCN) by sequential deposition of biphenyl-4,4′-dicarboxylic acid and iron atoms on the surface of a bulk insulator, calcite (10.4). The influence of the deposition order on the structure formation is studied by noncontact atomic force microscopy operated in ultrahigh vacuum at room temperature. It is found that sequential deposition facilitates MOCN formation when the organic linker molecules are first adsorbed on the surface, followed by iron deposition. This observation is explained by first-principles computations, indicating that the metal-molecule…