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Atomic force microscopy

Florian Albrecht, Felix Bischoff, Wilhelm Auwärter, Johannes V Barth, Jascha Repp
In recent years atomic force microscopy (AFM) at highest resolution was widely applied to mostly planar molecules, while its application towards exploring species with structural flexibility and a distinct 3D-character remains a challenge. Herein, the scope of non-contact AFM is widened by investigating subtle conformational differences occurring in the well-studied reference systems 2H-TPP and Cu-TPP on Cu(111). Different saddle-shape conformations of both species can be recognized in conventional constant-height AFM images...
October 25, 2016: Nano Letters
Hugh Sherman, Anh V Nguyen, Warren Bruckard
Atomic force microscopy makes it possible to measure the interacting forces between individual colloidal particles and air bubbles, which can provide a measure of the particle hydrophobicity. To indicate the level of hydrophobicity of the particle the contact angle can be calculated, assuming that no interfacial deformation occurs with the bubble retaining a spherical profile. Our experimental results obtained using a modified sphere tensiometry apparatus to detach sub-millimeter spherical particles show that deformation of the bubble interface does occur during particle detachment...
October 25, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Jangheon Kim, Janghyeon Lee, Soohyun Kim, Wonsuk Jung
We generate networks and carbonization between individualized single-walled carbon nanotubes (SWCNTs) by an optimized plasmonic heating process using a halogen lamp to improve electrical properties for flow-induced energy harvesting. These properties were characterized by Raman spectra, a field-emission-scanning probe, transmission electron microscopy, atomic force microscopy and thermo-graphic camera. The electrical sheet resistance of carbonized SWCNTs was decreased to 2.71 , 2.5 times smaller than normal-SWCNTs...
October 25, 2016: ACS Applied Materials & Interfaces
Miyeon Lee, Changjun Park, Hyoban Lee, Hongki Kim, Sang Youl Kim, Insik In, Bongsoo Kim
We report the characterization and formation of catechol-terminated molecules immobilized on gold nanoplates (Au NPLs) using N-(3,4-dihydroxyphenethyl)-2-mercaptoacetamide (Cat-EAA-SH). Single-crystalline Au NPLs, synthesized using a one-step chemical vapor transport method, have ultraclean and ultraflat surfaces that make Cat-EAA-SH molecules aligned into a well-ordered network of a large-scale. Topographic study of the catechol-terminated molecules on Au NPLs using atomic force microscopy showed more orderly orientation and higher density, leading to significantly higher adhesion as observed from local force-distance curves than those on other Au surfaces...
November 25, 2016: Nanotechnology
Ho Young Kim, Jae-Won Lee, Hye Min Oh, Kang-Jun Baeg, Sunshin Jung, Ho-Soon Yang, Wonki Lee, Jun Yeon Hwang, Keun Soo Kim, Seung Yol Jeong, Joong Tark Han, Mun Seok Jeong, Geon-Woong Lee, Hee Jin Jeong
Despite recent progress in producing flexible and stretchable electronics based on two-dimensional (2D) nanosheets, their intrinsic properties are often degraded by the presence of polymeric residues that remain attached to the 2D nanosheet surfaces following fabrication. Further breakthroughs are therefore keenly awaited to obtain clean surfaces compatible with flexible applications. Here we report a method that allows the 2D nanosheets to be intrinsically integrated onto flexible substrates. The method involves thermal decomposition of polymeric residues by microwave-induced ultrafast heating of the surface without affecting the underlying flexible substrate...
October 25, 2016: ACS Applied Materials & Interfaces
Alexander Dundua, Steffen Franzka, Mathias Ulbricht
Nonspecific adsorption of proteins is a challenging problem for the development of biocompatible materials, as well as for antifouling and fouling-release coatings, for instance for the marine industry. The concept of preparing amphiphilic systems based on low surface energy hydrophobic materials via their hydrophilic modification is being widely pursued. This work describes a novel two-step route for the preparation of interpenetrating polymer networks of otherwise incompatible poly(dimethylsiloxane) and zwitterionic polymers...
October 25, 2016: Macromolecular Rapid Communications
Benjamin H J Yap, Simon A Crawford, Raymond R Dagastine, Peter J Scales, Gregory J O Martin
Nitrogen deprivation (N-deprivation) is a proven strategy for inducing triacylglyceride accumulation in microalgae. However, its effect on the physical properties of cells and subsequently on product recovery processes is relatively unknown. In this study, the effect of N-deprivation on the cell size, cell wall thickness, and mechanical strength of three microalgae was investigated. As determined by analysis of micrographs from transmission electron microscopy, the average cell size and cell wall thickness for N-deprived Nannochloropsis sp...
October 24, 2016: Journal of Industrial Microbiology & Biotechnology
Andrew Gross, Raoudha Haddad, Christophe Travelet, Eric Reynaud, Pierre Audebert, Redouane Borsali, Serge Cosnier
The controlled self-assembly of precise and well-defined photochemically and electrochemically active carbohydrate-coated nanoparticles offers the exiting prospect of biocompatible catalysts for energy storage/conversion and biolabeling applications. Here an aqueous nanoparticle system has been developed with a versatile outer layer for host-guest molecule encapsulation via β-cyclodextrin inclusion complexes. A β-cyclodextrin modified polystyrene polymer was first obtained by copper nanopowder "click chemistry"...
October 25, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Coy P McNew, Negin Kananizadeh, Yusong Li, Eugene J LeBoeuf
Despite the prevalence of nonspherical colloidal particles, the role of particle shape in the transport of colloids is largely understudied. This study investigates the attachment of colloidal particles onto environmentally relevant surfaces while varying particle shape and ionic strength. Using quartz crystal microbalance and atomic force microscopy measurements, the role of particle shape was elucidated and possible mechanisms discussed. The attachment of both spherical and stretched polystyrene colloidal particles onto a smooth alginate-coated silica surface showed qualitative agreement with DLVO theory...
October 21, 2016: Chemosphere
Ravindra Kumar Jha, Prasanta Kumar Guha
WS2 nanosheets have been synthesized by ultrasonication in a binary mixture of acetone and 2-propanol, with a volume ratio of 80:20. Hansen solubility parameters were taken into consideration as part of the process. These nanosheets have been characterized by electron microscopy, atomic force microscopy, and x-ray diffraction, along with spectroscopy such as ultraviolet-visible spectroscopy, Raman spectroscopy, and x-ray photoelectron spectroscopy. The nanosheets were further used as a sensing material to fabricate a humidity sensor on interdigitated aluminum electrodes, realized over Si/SiO2 substrate using a conventional photolithography technique...
October 24, 2016: Nanotechnology
Moussa Biaye, Ewa Zbydniewska, Thierry Mélin, Dominique Deresmes, Guillaume Copie, Fabrizio Cleri, Neralagatta Sangeetha, Nicolas Decorde, Benoit Viallet, Jérémie Grisolia, Laurence Ressier, Heinrich Diesinger
Nanoparticle assemblies with thiol-terminated alkyl chains are studied by conducting atomic force microscopy (c-AFM) regarding their use as strain gauges for touch-sensitive panels. Current-force spectroscopy is used as a characterization tool complementary to the macroscopic setup since it allows a bias to be applied to a limited number of junctions, overcoming the Coulomb blockade energy and focusing on the contact electromechanics and the transport mechanism across the ligand. First, transition voltage spectroscopy is applied with varying force to target the underlying tunneling mechanism by observing whether the transition between the ohmic and exponential current-voltage behavior is force-dependent...
October 24, 2016: Nanotechnology
Takuro Ikeuchi, John Mack, Tebello A Nyokong, Nagao Kobayashi, Mutsumi Kimura
A water-soluble zinc phthalocyanine (ZnPc) complex with four negatively charged electron-withdrawing sulfonic acid substituents at the non-peripheral positions (-ZnTSPc) is found to have a high singlet oxygen (1O2) quantum yield and displays high photostability, since the formation of aggregates is hindered and the HOMO is significantly stabilized, this making -ZnTSPc potentially suitable for use as a photosensitizer for photodynamic therapy and photoimmunotherapy. Atomic force microscopy (AFM) reveals that mixtures of the negatively charged -ZnTSPc complex with a similar positively charged ZnPc were found to result in the self-assembly of one-dimensional accordion-like fibers...
October 24, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Christian Helbing, Robert Stößel, Dominik A Hering, Matthias Michael Lothar Arras, Jörg Bossert, Klaus D Jandt
Nanostructured surfaces have the potential to influence the assembly as well as the orientation of adsorbed proteins and may, thus, strongly influence the biomaterials performance. For the class of polymeric (bio)materials a reproducible and well characterized nanostructure is the ordered chain folded surface of a polyethylene single crystal (PE-SC). We tested the hypothesis that the trinodal-rod shaped protein human plasma fibrinogen (HPF) adsorbs on the (001) surface of PE-SCs along specific crystallographic directions...
October 24, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Mehwish Naz, Toby Hallam, Nina C Berner, Niall McEvoy, Riley Gatensby, John B McManus, Zareen Akhter, Georg S Duesberg
We report on 2H-2H'/1T phase conversion of MoS2 and MoSe2 polycrystalline films grown by thermally assisted conversion. The structural conversion of the transition metal dichalcogenides was successfully carried out by organolithium treatment on chip. As a result we obtained a new 2H-2H'/1T co-phase system of the TMDs thin films which was verified by Raman spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The conversion was successfully carried to on selected areas yielding a lateral heterostructure between the pristine 2H phase and the 2H'/1T co-phase regions...
October 24, 2016: ACS Applied Materials & Interfaces
Ren-Feng Ding, Chih-Wen Yang, Kuang-Yuh Huang, Ing-Shouh Hwang
In the operation of a dynamic mode atomic force microscope, a micro-fabricated rectangular cantilever is typically oscillated at or near its mechanical resonance frequency. Lateral bending resonances of cantilevers are rarely used because the resonances are not expected to be detected by the beam-deflection method. In this work, we found that micro-cantilevers with a large tip produced an out-of-plane displacement in lateral resonance (LR), which could be detected with the beam-deflection method. Finite-element analysis indicated that the presence of a large tip is the major source of the out-of-plane coupling for the LR...
October 24, 2016: Nanoscale
Fabrizio Bernini, Daniele Malferrari, Marcello Pignataro, Carlo Augusto Bortolotti, Giulia Di Rocco, Lidia Lancellotti, Maria Franca Brigatti, Rakez Kayed, Marco Borsari, Federica Del Monte, Elena Castellini
The pathological hallmark of misfolded protein diseases and aging is the accumulation of proteotoxic aggregates. However, the mechanisms of proteotoxicity and the dynamic changes in fiber formation and dissemination remain unclear, preventing a cure. Here we adopted a reductionist approach and used atomic force microscopy to define the temporal and spatial changes of amyloid aggregates, their modes of dissemination and the biochemical changes that may influence their growth. We show that pre-amyloid oligomers (PAO) mature to form linear and circular protofibrils, and amyloid fibers, and those can break reforming PAO that can migrate invading neighbor structures...
October 24, 2016: Scientific Reports
Miriam Rothdiener, Miriam Hegemann, Tatiana Uynuk-Ool, Brandan Walters, Piruntha Papugy, Phong Nguyen, Valentin Claus, Tanja Seeger, Ulrich Stoeckle, Karen A Boehme, Wilhelm K Aicher, Jan P Stegemann, Melanie L Hart, Bodo Kurz, Gerd Klein, Bernd Rolauffs
Using matrix elasticity and cyclic stretch have been investigated for inducing mesenchymal stromal cell (MSC) differentiation towards the smooth muscle cell (SMC) lineage but not in combination. We hypothesized that combining lineage-specific stiffness with cyclic stretch would result in a significantly increased expression of SMC markers, compared to non-stretched controls. First, we generated dense collagen type I sheets by mechanically compressing collagen hydrogels. Atomic force microscopy revealed a nanoscale stiffness range known to support myogenic differentiation...
October 24, 2016: Scientific Reports
Ion N Mihailescu, Dorota Bociaga, Gabriel Socol, George E Stan, Mariana-Carmen Chifiriuc, Coralia Bleotu, Marius A Husanu, Gianina Popescu-Pelin, Liviu Duta, Catalin R Luculescu, Irina Negut, Claudiu Hapenciuc, Cristina Besleaga, Irina Zgura, Florin Miculescu
We report on the selection by combinatorial pulsed laser deposition of Silver-doped Carbon structures with reliable physical-chemical characteristics and high efficiency against microbial biofilms. The investigation of the films was performed by scanning electron microscopy, high resolution atomic force microscopy, energy dispersive X-Ray Spectroscopy, X-ray diffraction, Raman spectroscopy, bonding strength "pull-out" tests, and surface energy measurements. In vitro biological assays were carried out using a large spectrum of bacterial and fungal strains, i...
October 20, 2016: International Journal of Pharmaceutics
Van-Chien Bui, Thi-Huong Nguyen
Knowledge about the mechanism by which some antibodies can block HIV-1 entry is critical to our understanding of their function and may offer new avenues for controlling the adhesion of HIV-1 to the host cells. While much progress has been made, this mechanism remains unclear. Here, atomic force microscopy, isothermal titration calorimetry (ITC), and circular dichroism spectroscopy were used to measure some biophysical characteristics of the interaction of four-domains (D1-D4) membrane protein CD4 with anti-D3 antibody OKT4 and with HIV-1 entry blocking anti-D1 antibody Leu3a...
October 17, 2016: Immunobiology
Gölnur Fakhrullina, Farida Akhatova, Maria Kibardina, Denis Fokin, Rawil Fakhrullin
Here we introduce PeakForce Tapping non-resonance atomic force microscopy for imaging and nanomechanical mapping of Caenorhabditis elegans nematodes. The animals were imaged both in air and water at nanoscale resolution. Layer-by-layer glass surface modification was employed to secure the worms for imaging in water. Microtopography of head region, annuli, furrows, lateral alae and tail region was visualised. Analysis of nanoscale surface features obtained during AFM imaging of three larval and adult hermaphrodite nematodes in natural environment allowed for numerical evaluation of annuli periodicity, furrows depth and annuli roughness...
October 19, 2016: Nanomedicine: Nanotechnology, Biology, and Medicine
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