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AFM Tip (afm + tip)
Selected AbstractsSynthesis of Zinc Glycerolate Microstacks from a ZnO Nanorod Sacrificial TemplateEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2009Róbert Rémiás Abstract We synthesized zinc glycerolate (ZnGly) microstacks bytreating ZnO with glycerol at 100 °C under reflux. We observed that the morphology of the ZnO source has a pronounced effect on the appearance of the ZnGly product. In the absence of structure-directing effects the product ZnGly is obtained as a random heap of hexagonal prisms with an average diameter and thickness of ca. 2.5 ,m and ca. 350 nm, respectively. However, bundles of nanorod-shaped ZnO obtained by the thermal decomposition of zinc oxalate nanorods could readily be transformed into 2,4 ,m long zinc glycerolate microstacks in which 6,12 hexagonal prisms are aligned face-to-face. We present evidence that the ZnGly plates in the microstacks are bound together by forces strong enough to withstand mechanical deformation exercised by a contacting AFM tip. The ZnGly microstacks appear to emerge from the ZnO nanorod bundles in an approx. 1:1 ratio in the reactive template synthesis.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Contact Angle Analysis During the Electro-oxidation of Self-Assembled Monolayers Formed by n -OctadecyltrichlorosilaneADVANCED FUNCTIONAL MATERIALS, Issue 19 2010Nicole Herzer Abstract The electrochemical oxidation process of self-assembled monolayers formed by n -octadecyltrichlorosilane (OTS) molecules on silicon wafers has been studied in a droplet of water by means of in situ water contact angle measurements. The application of different bias voltages between the substrate and a counter electrode placed into the droplet resulted in changes of the chemical nature of the monolayer, which yielded a significant alteration of the surfaces properties. Due to the changes of the wetting properties of the monolayer during the electro-oxidation process a change in the contact angles of the water droplet is concomitantly observed. This allows the in situ monitoring of the electro-oxidation process for large modified areas of several millimeters in diameter. The chosen approach represents an easy way to screen the major parameters that influence the oxidation process. Afterwards, the oxidized regions are characterized by Fourier-transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) measurements, and atomic force microscopy (AFM) investigations to obtain more information about the electro-oxidation process. The observations are correlated to experimental results obtained for oxidations performed on a smaller dimension range in the water meniscus of a conductive, biased AFM tip. A good correlation of the results in the different dimension ranges could be found. [source] All-Oxide Crystalline Microelectromechanical Systems: Bending the Functionalities of Transition-Metal Oxide Thin FilmsADVANCED MATERIALS, Issue 23 2009Luca Pellegrino A crystalline all-oxide microelectromechanical system is presented. A suspended SrTiO3(001) cantilever is employed as flexible substrate for the deposition of epitaxial transition-metal oxide films. A strain generator device for oxide films is thus demonstrated, changing the conductivity of an overgrown epitaxial (La,Sr-)-MnO3 film by bending downward the SrTiO3 element with an AFM tip or a gate voltage bias. [source] Comments on ,Electric-Field-Assisted Growth of Highly Uniform and Oriented Gold Nanotriangles on Conducting Glass Substrates'ADVANCED MATERIALS, Issue 13 2009Peng Diao AFM artifacts: Recent results by Sajanlal and Pradeep on the electric-field-assisted growth of highly uniform and oriented gold nanotriangles appear to provide a simple route to the size-, shape-, and orientation-controlled synthesis of nano structures. In our view, however, the triangle patterns observed in the AFM images are not real surface features but artifacts produced by a broken or contaminated AFM tip. [source] Localized "Click" Chemistry Through Dip-Pen Nanolithography,ADVANCED MATERIALS, Issue 24 2007A. Long Local reactions are triggered by delivering molecules from an AFM probe tip, allowing for direct modification of chemically functionalized surfaces. Silicon wafer-bound acetylene moieties readily undergo 1,3-dipolar cycloadddition with solution-phase azides delivered from an AFM tip. This selective and robust technique allows for the facile creation and placement of sub-micrometer-sized features. [source] Atomic force microscopy study of the role of LPS O-antigen on adhesion of E. coliJOURNAL OF MOLECULAR RECOGNITION, Issue 5 2009Joshua Strauss Abstract The O-antigen is a highly variable component of the lipopolysaccharide (LPS) among Escherichia coli strains and is useful for strain identification and assessing virulence. While the O-antigen has been chemically well characterized in terms of sugar composition, physical properties such as O-antigen length of E. coli LPS have not been well studied, even though LPS length is important for determining binding of bacteria to biomolecules and epithelial cells. Atomic force microscopy (AFM) was used to characterize the physicochemical properties of the LPS of eight E. coli strains. Steric repulsion between the AFM tip (silicon nitride) and the E. coli cells was measured and modeled, to determine LPS lengths for three O157 and two O113 E. coli strains, and three control (K12) strains that do not express the O-antigen. For strains with an O-antigen, the LPS lengths ranged from 17,±,10 to 37,±,9,nm, and LPS length was positively correlated with the force of adhesion (Fadh). Longer lengths of LPS may have allowed for more hydrogen bonding between the O-antigen and silanol groups of the AFM silicon nitride tip, which controlled the magnitude of Fadh. For control strains, LPS lengths ranged from 3,±,2 to 5,±,3,nm, and there was no relationship between LPS length and adhesion force between the bacterium and the silicon nitride tip. In the absence of the O-antigen, we attributed Fadh to electrostatic interactions with lipids in the bacterial membrane. Copyright © 2009 John Wiley & Sons, Ltd. [source] On the Use of the Nanoindentation Unloading Curve to Measure the Young's Modulus of Polymers on a Nanometer ScaleMACROMOLECULAR RAPID COMMUNICATIONS, Issue 22 2005Davide Tranchida Abstract Summary: The nanoindentation test is a fundamental tool to assess the link between morphology and mechanical properties. The preliminary results of a more exhaustive study about the applicability to polymers of the most used procedure to determine elastic modulus by indentation are reported in this short communication. A departure of the experimental conditions from the theoretical assumptions and results that give rise to the Oliver and Pharr analysis is shown to occur under a wide range of experimental conditions, with applied loads and penetration depths covering several orders of magnitude and using different indenter geometries. Unloading curves with exponents significantly larger than 2 are observed in disagreement with the contact mechanics approach used by Oliver and Pharr. An AFM image obtained in non contact mode of an indentation induced by a sharp AFM tip with a maximum applied load of ca 1.2 µN on amorphous PET. [source] Characterization of spin crossover crystal surface by AFMPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2010C. Chong Abstract Imaging nano-domains in spin crossover (SCO) compounds remains so far an unreached goal. We report on the first AFM tapping-mode investigation of SCO single crystals, performed at room temperature with the well known mononuclear compound [Fe(ptz)6](BF4)2 (ptz,=,1-propyl-tetrazole) and the trinuclear supramolecular compound [Fe3(hyetrz)6(H2O)6](CF3SO3)6 (hyetrz,=,4-(2,-hydroxyethyl)-1,2,4-triazole) which shows a gradual spin conversion centred at room temperature. The natural surface of the former crystal revealed a volatile coating of the scanned area attributed to the transport of adsorbed water under the effect of interaction with the AFM tip. The second one showed astonishing leopard-skin patterns assigned to the effect of atmospheric humidity on this hygroscopic compound. Their origin is discussed. We suggest the use of fluid coating layers as a general method for revealing the nano-patterning of physical properties (e.g. like-spin domains) at the surface of dielectric materials. AFM-tapping images of [Fe3(hyetrz)6(H2O)6](CF3SO3)6 at room temperature and ambient atmosphere. [source] On dot and out of dot electrical characteristics of silicon oxide nanodots patterned by scanning probe lithographyPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2009Sabar D. Hutagalung Abstract Silicon oxide nanodot arrays were grown on pre-cleaned silicon (100) substrate by scanning probe nanolithography. In this study, a conductive AFM was used to fabricate nanoscale oxide dots in humidity controlled environment. The AFM is equipped with a nanotechnology software package providing the control of tip-sample voltage and tip motion according to pre-designed patterns. The surface topography and size of obtained patterns (diameter and height) were investigated by a noncontact AFM mode. A series of five silicon oxide nanodot array with diameter in the range of 146.05-247.65 nm and height 2.14-4.87 nm had been successfully fabricated. Meanwhile, a contact AFM mode was used to investigate the localized I-V characteristics on the dots and out of dot position. It was found, the on dot characteristics are highly nonohmic due to potential barrier interface between silicon oxide and silicon substrate. However, the out of dot characteristic is linear indicates an ohmic contact between AFM tip and sample. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Atomic force microscopy: A powerful molecular toolkit in nanoproteomicsPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 24 2009Yves F. DufrêneArticle first published online: 7 OCT 200 Abstract Analysing microbial cell surface proteins is a challenging task in current microbial proteomic research, which has major implications for drug design, vaccine development, and microbial monitoring. In this context, atomic force microscopy (AFM) has recently emerged has a powerful characterization platform, providing valuable insights into the surface proteome of microbial cells. The aim of this article is to show how advanced AFM techniques, that all have in common functionalization of the AFM tip with specific molecules, can be used to answer pertinent questions related to surface-associated proteins, such as what is their spatial arrangement on the cell surface, and what are the forces driving their interaction with the environment? [source] Measuring the Interaction Forces between Protein Inclusion Bodies and an Air Bubble Using an Atomic Force MicroscopeBIOTECHNOLOGY PROGRESS, Issue 5 2001N. D. Wangsa-Wirawan Interaction forces between protein inclusion bodies and an air bubble have been quantified using an atomic force microscope (AFM). The inclusion bodies were attached to the AFM tip by covalent bonds. Interaction forces measured in various buffer concentrations varied from 9.7 nN to 25.3 nN (± 4,11%) depending on pH. Hydrophobic forces provide a stronger contribution to overall interaction force than electrostatic double layer forces. It also appears that the ionic strength affects the interaction force in a complex way that cannot be directly predicted by DLVO theory. The effects of pH are significantly stronger for the inclusion body compared to the air bubble. This study provides fundamental information that will subsequently facilitate the rational design of flotation recovery system for inclusion bodies. It has also demonstrated the potential of AFM to facilitate the design of such processes from a practical viewpoint. [source] Cyclic Control of the Surface Properties of a Monolayer-Functionalized Electrode by the Electrochemical Generation of Hg NanoclustersCHEMISTRY - A EUROPEAN JOURNAL, Issue 33 2006Michael Riskin Abstract Hg2+ ions are bound to a 1,4-benzenedimethanethiol (BDMT) monolayer assembled on a Au electrode. Electrochemical reduction of the Hg2+,BDMT monolayer to Hg+,BDMT (at E°=0.48 V) and subsequently to Hg0,BDMT (at E°=0.2 V) proceeds with electron-transfer rate constants of 8 and 11 s,1, respectively. The Hg0 atoms cluster into aggregates that exhibit dimensions of 30 nm to 2 ,m, within a time interval of minutes. Electrochemical oxidation of the nanoclusters to Hg+ and further oxidation to Hg2+ ions proceeds with electron-transfer rate constants corresponding to 9 and 43 s,1, respectively, and the redistribution of Hg2+ on the thiolated monolayer occurs within approximately 15 s. The reduction of the Hg2+ ions to the Hg0 nanoclusters and their reverse electrochemical oxidation proceed without the dissolution of mercury species to the electrolyte, implying high affinities of Hg2+, Hg+, and Hg0 to the thiolated monolayer. The electrochemical transformation of the Hg2+ -thiolated monolayer to the Hg0 -nanocluster-functionalized monolayer is characterized by electrochemical means, surface plasmon resonance (SPR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact-angle measurements. The Hg0 -nanocluster-modified surface reveals enhanced hydrophobicity (contact angle 76°) as compared to the Hg2+ -thiolated monolayer (contact angle 57°). The hydrophobic properties of the Hg0 -nanocluster-modified electrode are further supported by force measurements employing a hydrophobically modified AFM tip. [source] Probing the interaction forces between hydrophobic peptides and supported lipid bilayers using AFMJOURNAL OF MOLECULAR RECOGNITION, Issue 6 2007Guillaume Andre Abstract Despite the vast body of literature that has accumulated on tilted peptides in the past decade, direct information on the forces that drive their interaction with lipid membranes is lacking. Here, we attempted to use atomic force microscopy (AFM) to explore the interaction forces between the Simian immunodeficiency virus peptide and phase-separated supported bilayers composed of various lipids, i.e. dipalmitoylphosphatidylcholine, dioleoylphosphatidylcholine, dioleoylphosphatidic acid and dipalmitoylphosphatidylethanolamine. Histidine-tagged peptides were attached onto AFM tips terminated with nitrilotriacetate and tri(ethylene glycol) groups, an approach expected to ensure optimal exposure of the C-terminal hydrophobic domain. Force,distance curves recorded between peptide-tips and the different bilayer domains always showed a long-range repulsion upon approach and a lack of adhesion upon retraction, in marked contrast with the hydrophobic nature of the peptide. To explain this unexpected behaviour, we suggest a mechanism in which lipids are pulled out from the bilayer due to strong interactions with the peptide-tip, in agreement with the very low force needed to extract lipids from supported bilayers. Copyright © 2007 John Wiley & Sons, Ltd. [source] Friction and wear effects on a micro/nano-scaleLUBRICATION SCIENCE, Issue 1 2001E. Santner Abstract In this paper are described tribological effects which can be found in micro-tribological systems, and in those macro-systems which can be analysed by micro-methods, e.g., by atomic force microscopy (AFM) or related methods. Micro-tribology systems have friction contacts with loads in the micro/nano-newton range and/or dimensions in the micro/nanometre range. Experiments on the micro/nano-scale should be easier to explain by theoretical modelling due to their simpler system structure. An example is discussed of adhesion and friction measurements between AFM tips and clean, flat, solid surfaces in ultra-high vacuum, which shows some of the special aspects of micro/nano-tribology. Surprising friction characteristics on surfaces with an artificial micro-structure can be explained by skilled and careful topographical analysis of the friction path with an AFM. In micro-sensor contacts, ,single wear events' can be detected using AFM analysis of the contact region. For ceramic compounds, different friction levels for the components of the material can be found. The problems, difficulties, and dangers of misinterpretation are also discussed. [source] | ||||||||||||||||