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Atomic force microscopy

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https://www.readbyqxmd.com/read/28449542/estimation-of-the-number-of-quantum-dots-immobilized-on-an-ultra-flat-au-surface
#1
Hiroki Ito, Atsushi Iio, Katsutoshi Tokuhara, Hiroyuki Sakaue, Yutaka Kadoya, Hitoshi Suzuki
Quantum dots (QDs) were immobilized on an ultra-flat Au surface by using amide binding between the carboxyl groups on the QDs and the amino groups of the self-assembled monolayer on the surface. The number density of the QDs estimated by atomic force microscopy (AFM) agreed with the quantity of QDs estimated by X-ray photoelectron spectroscopy and fluorescence microscopy. QDs were also immobilized on dot patterns fabricated by e-beam lithography. AFM was able to identify clusters of just a few QDs on the dot patterns, whose minimum designed size was 50 nm × 50 nm per dot...
December 2017: Nanoscale Research Letters
https://www.readbyqxmd.com/read/28448920/the-effect-of-equiaxial-stretching-on-the-osteogenic-differentiation-and-mechanical-properties-of-human-adipose-stem-cells
#2
Sanni Virjula, Feihu Zhao, Joni Leivo, Sari Vanhatupa, Joose Kreutzer, Ted J Vaughan, Anna-Maija Honkala, Marlitt Viehrig, Conleth A Mullen, Pasi Kallio, Laoise M McNamara, Susanna Miettinen
Although mechanical cues are known to affect stem cell fate and mechanobiology, the significance of such stimuli on the osteogenic differentiation of human adipose stem cells (hASCs) remains unclear. In this study, we investigated the effect of long-term mechanical stimulation on the attachment, osteogenic differentiation and mechanical properties of hASCs. Tailor-made, pneumatic cell stretching devices were used to expose hASCs to cyclic equiaxial stretching in osteogenic medium. Cell attachment and focal adhesions were visualised using immunocytochemical vinculin staining on days 3 and 6, and the proliferation and alkaline phosphatase activity, as a sign of early osteogenic differentiation, were analysed on days 0, 6 and 10...
April 13, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28448149/hofmeister-effect-on-pnipam-in-bulk-and-at-an-interface-surface-partitioning-of-weakly-hydrated-anions
#3
Saeed Zajforoushan Moghaddam, Esben Thormann
Effect of sodium fluoride, sodium trichloroacetate, and sodium thiocyanate on the stability and conformation of poly(N-isopropylacrylamide), in bulk solution and at the gold-aqueous interface, is investigated by differential scanning calorimetry, dynamic light scattering, quartz crystal microbalance, and atomic force microscopy. The results indicate a surface partitioning of the weakly hydrated anions, i.e., thiocyanate and trichloroacetate, and the findings are discussed in terms of anion-induced electrostatic stabilization...
April 27, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28448123/enhancing-the-domain-wall-conductivity-in-lithium-niobate-single-crystals
#4
Christian Godau, Thomas Kämpfe, Andreas Thiessen, Lukas M Eng, Alexander Haußmann
Domain walls (DWs) in ferroelectric/ferroic materials have been in the central research focus for the last 50 years; DWs bear a multitude of extraordinary physical parameters within a unit-cell-sized lateral confinement. Especially, one outstanding feature has recently attracted a lot of attention for room-temperature applications, which is the potential to use DWs as 2-dimensional (2D) conducting channels that completely penetrate bulk compounds. Domain wall currents in lithium niobate (LNO) so far lie in the lower $pA$ regime...
April 27, 2017: ACS Nano
https://www.readbyqxmd.com/read/28447179/influence-of-inherent-mechanophenotype-on-competitive-cellular-adherence
#5
Manisha K Shah, Iris H Garcia-Pak, Eric M Darling
Understanding the role of mechanophenotype in competitive adherence of cells to other cells versus underlying substrates can inform such processes as tissue development, cancer progression, and wound healing. This study investigated how mechanophenotype, defined by whole-cell, elastic/viscoelastic properties for the perinuclear region, and cellular assembly are intertwined through the mechanosensing process. Atomic force microscopy was used to characterize the temporal elastic/viscoelastic properties of individual and assembled fibroblasts grown on substrates with elastic moduli above, below, or similar to whole-cell mechanophenotypes measured for three, genetically modified cell lines...
April 26, 2017: Annals of Biomedical Engineering
https://www.readbyqxmd.com/read/28446335/quantitative-nano-characterization-of-polymers-using-atomic-force-microscopy
#6
Milad Radiom, Svilen Kozhuharov, Phally Kong, Michela di Giannantonio, Mathieu A Ayer, Plinio Maroni, Andreas F M Kilbinger, Katharina M Fromm, Christoph Weder, Michal Borkovec
The present article offers an overview on the use of atomic force microscopy (AFM) to characterize the nanomechanical properties of polymers. AFM imaging reveals the conformations of polymer molecules at solid- liquid interfaces. In particular, for polyelectrolytes, the effect of ionic strength on the conformations of molecules can be studied. Examination of force versus extension profiles obtained using AFM-based single molecule force spectroscopy gives information on the entropic and enthalpic elasticities in pN to nN force range...
April 26, 2017: Chimia
https://www.readbyqxmd.com/read/28446012/differentiation-potential-of-mesenchymal-stem-cells-is-related-to-their-intrinsic-mechanical-properties
#7
Ihn Han, Byung-Su Kwon, Hun-Kuk Park, Kyung Sook Kim
PURPOSE: The differentiation properties of stem cells are not yet fully understood due to their close association with multiple environmental and extrinsic factors. This study investigates the differentiation properties of mesenchymal stem cells (MSCs) and correlates them with their intrinsic mechanical properties. METHODS: A total of 3 different types of MSCs, namely bone marrow-derived MSCs (BMSCs), umbilical cord-derived MSCs (UCSCs), and adipose-derived MSCs (ADSCs) were evaluated...
April 2017: International Neurourology Journal
https://www.readbyqxmd.com/read/28445745/increased-tissue-stiffness-in-tumors-from-mice-with-neurofibromatosis-1-optic-glioma
#8
Christopher Walter, Lindsey Crawford, Melinda Lai, Joseph A Toonen, Yuan Pan, Shelly Sakiyama-Elbert, David H Gutmann, Amit Pathak
Children with neurofibromatosis type 1 (NF1) cancer predisposition syndrome are prone to the development of low-grade brain tumors (gliomas) within the optic pathway (optic gliomas). One of the key obstacles to developing successful therapeutic strategies for these tumors is the striking lack of information about the mechanical properties that characterize these tumors relative to non-neoplastic optic nerve tissue. To study the physical changes that may occur when an optic nerve glioma is present, we employed atomic force microscopy to measure the stiffness of healthy versus tumor-bearing optic nerve tissue...
April 25, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28444700/fluorescence-lifetime-imaging-and-super-resolution-microscopies-shed-light-on-the-directed-and-self-assembly-of-functional-porphyrins-onto-carbon-nanotubes-and-flat-surfaces
#9
Boyang Mao, David González Calatayud, Vincenzo Mirabello, Haobo Ge, Benjamin J Hodges, Robert M J Jacobs, Ashley M Shepherd, José Alberto Ribeiro Martins, Navaratnarajah Kuganathan, Jorge Bernardino De La Serna, Stanley W Botchway, Sofia Ioana Pascu
Two new routes to functionalized SWNTs have been established using a bulky Zn(II)-porphyrin featuring thiolate groups at the periphery. We probed the optical properties of this Zinc(II)-substituted, bulky aryl porphyrin and those of the corresponding new nano-composites with single walled carbon nanotube (SWNTs) and coronene, as a model for graphene. We report hereby on: (i) the supramolecular interactions between the pristine SWNTs and Zn(II)-porphyrin by virtue of π-π stacking, and (ii) a novel covalent binding strategy based on the Bingel reaction...
April 25, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28444689/the-young-s-modulus-fracture-stress-and-fracture-strain-of-gellan-hydrogels-filled-with-whey-protein-microparticles
#10
Cherry Wing Yu Lam, Shinya Ikeda
Texture modifying abilities of whey protein microparticles are expected to be dependent on pH during heat-induced aggregation of whey protein in the microparticulation process. Therefore, whey protein microparticles were prepared at either pH 5.5 or 6.8 and their effects on small and large deformation properties of gellan gels containing whey protein microparticles as fillers were investigated. The majority of whey protein microparticles had diameters around 2 μm. Atomic force microscopy images showed that whey protein microparticles prepared at pH 6...
April 25, 2017: Journal of Food Science
https://www.readbyqxmd.com/read/28443936/effects-of-graphene-defects-on-gas-sensing-properties-towards-no2-detection
#11
Filiberto Ricciardella, Sten Vollebregt, Tiziana Polichetti, Mario Miscuglio, Brigida Alfano, Maria L Miglietta, Ettore Massera, Girolamo Di Francia, Pasqualina M Sarro
The crystal structure of graphene flakes is expected to significantly affect their sensing properties. Here we report an experimental investigation on the crystalline structure of graphene aimed at exploring the effects on the gas sensing properties. The morphology of graphene, prepared via Chemical Vapor Deposition (CVD), Liquid Phase Exfoliation (LPE) and Mechanical Exfoliation (ME), is inspected through Raman spectroscopy, Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). CVD and LPE-graphene structures are found to be more defective with respect to ME-graphene...
April 26, 2017: Nanoscale
https://www.readbyqxmd.com/read/28443855/dielectric-functions-and-critical-points-of-crystalline-ws2-ultrathin-films-with-tunable-thickness
#12
Da-Hai Li, Hua Zheng, Zi-Yi Wang, Rong-Jun Zhang, Hao Zhang, Yu-Xiang Zheng, Song-You Wang, David Wei Zhang, Liang-Yao Chen
Centimeter-scale WS2 ultrathin films were synthesized on sapphire substrates, and they showed highly oriented crystallographic growth along the c axis. Afterwards, the as-grown samples were systematically characterized using various detection methods. Reliable values of the roughness layer thickness and the film thickness were extracted using both atomic force microscopy (AFM) and spectroscopic ellipsometry (SE), and identified using Raman spectroscopy as well. The expansion and tensile strain along the [001] direction were discovered using X-ray diffraction (XRD) measurements...
April 26, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28443694/fractal-features-and-surface-micromorphology-of-unworn-surfaces-of-rigid-gas-permeable-contact-lenses
#13
Ştefan Ţălu, Miroslaw Bramowicz, Slawomir Kulesza, Ilenia Fiorillo, Stefano Giovanzana
PURPOSE: The aim of this exploratory study was to investigate the micromorphology of surfaces of rigid gas permeable (RGP) contact lenses (CLs) using atomic force microscopy (AFM) followed by fractal analysis. MATERIALS AND METHODS: In order to characterize in a quantitative manner the micromorphology of surfaces of new and unworn RGP CLs made of twelve different materials, AFM was taken and then analyzed using fractal methods. Surface topography was sampled in an intermittent-contact mode in air, on square areas of 5 × 5 µm(2) (MultiMode with Nanoscope V (Bruker)...
April 26, 2017: Current Eye Research
https://www.readbyqxmd.com/read/28443645/electronegativity-determination-of-individual-surface-atoms-by-atomic-force-microscopy
#14
Jo Onoda, Martin Ondráček, Pavel Jelínek, Yoshiaki Sugimoto
Electronegativity is a fundamental concept in chemistry. Despite its importance, the experimental determination has been limited only to ensemble-averaged techniques. Here, we report a methodology to evaluate the electronegativity of individual surface atoms by atomic force microscopy. By measuring bond energies on the surface atoms using different tips, we find characteristic linear relations between the bond energies of different chemical species. We show that the linear relation can be rationalized by Pauling's equation for polar covalent bonds...
April 26, 2017: Nature Communications
https://www.readbyqxmd.com/read/28441775/progress-in-the-correlative-atomic-force-microscopy-and-optical-microscopy
#15
REVIEW
Lulu Zhou, Mingjun Cai, Ti Tong, Hongda Wang
Atomic force microscopy (AFM) has evolved from the originally morphological imaging technique to a powerful and multifunctional technique for manipulating and detecting the interactions between molecules at nanometer resolution. However, AFM cannot provide the precise information of synchronized molecular groups and has many shortcomings in the aspects of determining the mechanism of the interactions and the elaborate structure due to the limitations of the technology, itself, such as non-specificity and low imaging speed...
April 24, 2017: Sensors
https://www.readbyqxmd.com/read/28441470/al2o3-and-sio2-atomic-layer-deposition-layers-on-zno-photoanodes-and-degradation-mechanisms
#16
Qian Cheng, Manpuneet Kaur Benipal, Qianlang Liu, Xingye Wang, Peter A A Crozier, Candace K Chan, Robert J Nemanich
Strategies for protecting unstable semiconductors include the utilization of surface layers comprised of thin films deposited using atomic layer deposition (ALD). The protective layer is expected to: (1) be stable against reaction with photogenerated holes, (2) prevent direct contact of the unstable semiconductor with the electrolyte, and (3) prevent the migration of ions through the semiconductor/electrolyte interface, while still allowing photogenerated carriers to transport to the interface and participate in the desired redox reactions...
April 25, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28438164/aggregation-dispersion-transitions-of-t4-phage-triggered-by-environmental-ion-availability
#17
Bożena Szermer-Olearnik, Marek Drab, Mateusz Mąkosa, Maria Zembala, Jakub Barbasz, Krystyna Dąbrowska, Janusz Boratyński
BACKGROUND: Bacteriophage survives in at least two extremes of ionic environments: bacterial host (high ionic-cytosol) and that of soil (low ionic-environmental water). The impact of ionic composition in the micro- and macro-environments has not so far been addressed in phage biology. RESULTS: Here, we discovered a novel mechanism of aggregation/disaggregation transitions by phage virions. When normal sodium levels in phage media (150 mM) were lowered to 10 mM, advanced imaging by scanning electron microscopy, atomic force microscopy and dynamic light scattering all revealed formation of viral packages, each containing 20-100 virions...
April 24, 2017: Journal of Nanobiotechnology
https://www.readbyqxmd.com/read/28437078/a-step-towards-high-energy-silicon-based-thin-film-lithium-ion-batteries
#18
Antonia Reyes Jiménez, Richard Klöpsch, Ralf Wagner, Uta C Rodehorst, Martin Kolek, Roman Nölle, Martin Winter, Tobias Placke
The next generation of lithium ion batteries (LIBs) with increased energy density for large-scale applications, such as electric mobility, but also for small electronic devices, e.g. micro-batteries and on-chip batteries, requires advanced electrode active materials with enhanced specific and volumetric capacities. In this regard, silicon (Si) as anode material has attracted much attention due to its high specific capacity. However, the enormous volume changes during lithiation/de-lithiation are still a main obstacle avoiding the broad commercial use of Si-based electrodes...
April 24, 2017: ACS Nano
https://www.readbyqxmd.com/read/28437063/charge-transport-in-intermixed-regions-of-all-polymer-solar-cells-studied-by-conductive-atomic-force-microscopy
#19
Miki Osaka, Daisuke Mori, Hiroaki Benten, Hiroki Ogawa, Hideo Ohkita, Shinzaburo Ito
Charge transport in intermixed regions of all-polymer solar cells based on a blend of poly(3-hexylthiophene) (P3HT; electron donor) with poly[2,7-(9,9-didodecylfluorene)-alt-5,5-(4',7'-bis(2-thienyl)-2',1',3'-benzothiadiazole)] (PF12TBT; electron acceptor) was studied by conductive atomic force microscopy (C-AFM). For a blend film fabricated from a chlorobenzene solution, intermixed regions were detected between the P3HT-rich and PF12TBT-rich domains. The overall hole current in the intermixed regions remained almost constant, both before and after thermal annealing at 80 C, but it increased in the P3HT-rich domains...
April 24, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28436508/purification-characterization-and-bioactivities-of-polysaccharides-from-pleurotus-ferulae
#20
Jinyu Li, Pengfei Yuan, Xinhui Wang, Adila Aipire, Minjing Li, Jie Yang, Hong Tao, Tianlei Ying, Changshuang Fu, Xianxian Wei, Fuchun Zhang, Jinyao Li
Pleurotus ferulae is an edible mushroom and has been used in Uygur medicine for a long time. In this study, we purified polysaccharides from P. ferulae (PFPS) and investigated its structural characteristics. We obtained a homogeneous PFPS with a molecular weight of around 1600 kDa and prominent characteristic polysaccharide groups, which mainly contained glucose (97%), followed by mannose and galactose (3%). Both (1)H and (13)C NMR spectra indicated that PFPS contained both α- and β-anomeric configurations...
April 24, 2017: Food & Function
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