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Atomic force microscopy

Francesca Malvano, Luigi Maritato, Giovanni Carapella, Pasquale Orgiani, Roberto Pilloton, Marisa Di Matteo, Donatella Albanese
Due to their interesting ferroelectric, conductive and dielectric properties, in recent years, perovskite-structured materials have begun to attract increasing interest in the biosensing field. In this study, a strontium titanate perovskite layer (SrTiO₃) has been synthesized on a platinum electrode and exploited for the development of an impedimetric label-free immunosensor for Escherichia coli O157:H7 detection. The electrochemical characterization of the perovskite-modified electrode during the construction of the immunosensor, as well as after the interaction with different E...
March 16, 2018: Biosensors
N G Fischer, A Tsujimoto, A G Baruth
OBJECTIVE: Limited information is available on how to polish and finish zirconia surfaces following computer-aided design/computer-aided manufacturing (CAD/CAM), specifically, how differing application forces and reuse of zirconia polishing systems affect zirconia topography. PURPOSE: To determine the effect of differing, clinically relevant, polishing application forces and multiple usages of polishing burs on the surface topography of CAD/CAM zirconia. METHODS: One hundred twenty 220-grit carbide finished zirconia disks were sintered according to manufacturer's directions and divided into two groups for the study of two coarse polishing bur types...
March 16, 2018: Operative Dentistry
Iain M Aldous, Laurence J Hardwick
The deposition and dissolution of sodium superoxide (NaO2 ) was investigated by atomic force microscopy. Rectangular prisms consisting of 8 smaller sub-structures grew from NaO2 platelets, when discharged in 0.5 M NaClO4 , diethylene glycol dimethyl ether on highly ordered pyrolytic graphite. During oxidation the 8 sub-structures are conserved. Ring-like structures of Na2 CO3 of 200 nm diameter remain at the end of oxidation.
March 16, 2018: Chemical Communications: Chem Comm
Y J Son, H S Kim, W Mao, J B Park, D Lee, H Lee, H S Yoo
A two-step strategy for coaxial electrospinning and postelectrospinning is an effective method for fabricating superfine nanofibers composed of highly swellable hydrogels. Alginate and poly(ε-caprolactone) [PCL] were coelectrospun via fibrous meshes with a coaxial nozzle; alginate at the core was subsequently cross-linked in calcium chloride solution. The PCL sheath was removed from the meshes by repeated organic-phase washing. The peeling process was monitored by scanning electron microscopy, transmission electron microscopy, and differential scanning calorimetry, and the complete removal of the PCL outer layers was confirmed by the thinning of the fiber volume...
March 16, 2018: Nanoscale
Y Ni, Y Qin, Z Fang, Z Zhang
PURPOSE: Dysfunction or death of retinal pigment epithelial (RPE) cells is a common pathogenesis of various types of retinal degenerative diseases. Recent reports indicated that ROCK pathway inhibitors regulate cell proliferation or apoptosis in a cell-type-dependent manner. Here, we aim to investigate the effect of ROCK inhibitor Y-27632 on the human retinal pigment epithelium (RPE) in vitro. METHODS: Cell proliferation and apoptosis were analyzed by CCK-8 and flow cytometry respectively...
March 16, 2018: Current Molecular Medicine
Hisao Tsukamoto, Masahiro Higashi, Hideyoshi Motoki, Hiroki Watanabe, Christian Ganser, Koichi Nakajo, Yoshihiro Kubo, Takayuki Uchihashi, Yuji Furutani
Canonical K+ channels are tetrameric and highly K+ selective, whereas two-pore domain K+ (K2P) channels form dimers, but with a similar pore architecture. A two-pore domain potassium channel TWIK1 (KCNK1 or K2P1) allows permeation of Na+ and other monovalent ions, resulting mainly from the presence of Thr118 in the P1 domain. However, the mechanistic basis for this reduced selectivity is unclear. Using ion-exchange-induced difference infrared spectroscopy, we analyzed WT TWIK1 and T118I (highly K+ selective) and L228F (substitution in the P2 domain) TWIK1 variants and found that in the presence of K+ ions, WT and both variants exhibit an amide-I band at 1680 cm-1 This band corresponds to interactions of the backbone carbonyls in the selectivity filter with K+ , a feature very similar to that of the canonical K+ channel KcsA...
March 15, 2018: Journal of Biological Chemistry
Chao Wang, Zhi-Yi Hu, Heng Zhao, Wenbei Yu, Sijia Wu, Jing Liu, Lihua Chen, Yu Li, Bao-Lian Su
We report three types of conducting polymers (CPs), polyaniline (PANI), polypyrrole (PPY) and poly (3,4-ethylenedioxythiophene) (PEDOT) to modify the surface of the CdS nanorods to probe their photocorrosion inhibition and photocatalytic hydrogen production. Various characterizations, such as high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and density function theory (DFT) calculations have been conducted to reveal the intrinsic structure of the as-constructed CPs@CdS (@ means CPs at the surface of CdS) core-shell nanorods...
March 6, 2018: Journal of Colloid and Interface Science
Qing Li, Biao Yang, Jonas Björk, Qigang Zhong, Huanxin Ju, Junjie Zhang, Nan Cao, Ziliang Shi, Haiming Zhang, Daniel Ebeling, Andre Schirmeisen, Junfa Zhu, Lifeng Chi
Hierarchical control of chemical reactions is being considered as one of the most ambitious and challenging topics in modern organic chemistry. In this study, we have realized the one-by-one scission of the X-H bonds (X=N and C) of aromatic amines in a controlled fashion on the Cu(111) surface. Each dehydrogenation reaction leads to certain metal-organic supramolecular structures, which were monitored in single-bond resolution via scanning tunneling microscopy and non-contact atomic force microscopy. Moreover, the reaction pathways were elucidated from X-ray photoelectron spectroscopy measurements and density functional theory calculations...
March 15, 2018: Journal of the American Chemical Society
Guanglei Cheng, Anil Annadi, Shicheng Lu, Hyungwoo Lee, Jung-Woo Lee, Mengchen Huang, Chang-Beom Eom, Patrick Irvin, Jeremy Levy
The widely reported magnetoresistance oscillations in LaAlO_{3}/SrTiO_{3} heterostructures have invariably been attributed to the Shubnikov-de Haas (SdH) effect, despite a pronounced inconsistency with low-field Hall resistance measurements. Here we report SdH-like resistance oscillations in quasi-1D electron waveguides created at the LaAlO_{3}/SrTiO_{3} interface by conductive atomic force microscopy lithography. These oscillations can be directly attributed to magnetic depopulation of magnetoelectric subbands...
February 16, 2018: Physical Review Letters
Heather M Hill, Albert F Rigosi, Sugata Chowdhury, Yanfei Yang, Nhan V Nguyen, Francesca Tavazza, Randolph E Elmquist, David B Newell, Angela R Hight Walker
Monolayer epitaxial graphene (EG) is a suitable candidate for a variety of electronic applications. One advantage of EG growth on the Si face of SiC is that it develops as a single crystal, as does the layer below, referred to as the interfacial buffer layer (IBL), whose properties include an electronic band gap. Though much research has been conducted to learn about the electrical properties of the IBL, not nearly as much work has been reported on the optical properties of the IBL. In this work, we combine measurements from Mueller matrix ellipsometry, differential reflectance contrast, atomic force microscopy, and Raman spectroscopy, as well as calculations from Kramers-Kronig analyses and density functional theory (DFT), to determine the dielectric function of the IBL within the energy range of 1 eV to 8...
November 2017: Physical Review. B
Yara Abidine, Andrei Constantinescu, Valérie M Laurent, Vinoth Sundar Rajan, Richard Michel, Valentin Laplaud, Alain Duperray, Claude Verdier
Cancer cells are usually found to be softer than normal cells, but their stiffness changes when they are in contact with different environments because of mechanosensitivity. For example, they adhere to a given substrate by tuning their cytoskeleton, thus affecting their rheological properties. This mechanism could become efficient when cancer cells invade the surrounding tissues, and they have to remodel their cytoskeleton in order to achieve particular deformations. Here we use an atomic force microscope in force modulation mode to study how local rheological properties of cancer cells are affected by a change of the environment...
March 13, 2018: Biophysical Journal
Roshan Kumar, Raniki Kumari, Sanjay Kumar, Deepak Kumar Jangir, Tushar Kanti Maiti
α-Synuclein, a major constituent of proteinaceous inclusions named Lewy body, has been shown to be released and taken up by cells, which may facilitate its progressive pathological spreading and neuronal cell death in Parkinson's disease. However, the pathophysiological effect and signalling cascade initiated by extracellular α-synuclein in cellular milieu are not well understood. Herein we have investigated the perturbations induced by low molecular weight α-synuclein and different types of α-synuclein oligomers in the neuroblastoma SH-SY5Y cells...
March 14, 2018: Biomacromolecules
Franz Dinkelacker, Philipp Marzak, Jeongsik Yun, Yunchang Liang, Aliaksandr S Bandarenka
So-called solid electrolyte interface (SEI) in a lithium ion battery largely determines the performance of the whole system. However, it is one of the least understood objects in these types of batteries. SEIs are formed during the initial charge discharge cycles, prevent the organic electrolytes from further decomposition and at the same time govern lithium intercalation into the graphite anodes. In this work, we use electrochemical impedance spectroscopy and atomic force microscopy (AFM) to investigate the properties of SEI film and electrified "graphite/SEI/electrolyte interface"...
March 14, 2018: ACS Applied Materials & Interfaces
Xue-Jiao Ma, Yin-Juan Zhang, Cheng-Ming Zeng
Sodium dodecyl sulfate (SDS), as an anionic surfactant, can induce protein conformational changes. Recent investigations demonstrated different effects of SDS on protein amyloid aggregation. In the present study, the effect of SDS on amyloid aggregation of bovine serum albumin (BSA) was evaluated. BSA transformed to β-sheet-rich amyloid aggregates upon incubation at pH 7.4 and 65°C, as demonstrated by thioflavin T fluorescence, circular dichroism, and transmission electron microscopy. SDS at submicellar concentrations inhibited BSA amyloid aggregation with IC50 of 47...
January 2018: Biochemistry. Biokhimii︠a︡
Martin Dehnert, Robert Magerle
In the atomic force microscopy (AFM) investigation of soft polymers and liquids, the tip-sample interaction is dominated by long-range van der Waals forces, capillary forces and adhesion. Furthermore, the tip can indent several tens of nanometres into the surface, and it can pull off a polymer filament from the surface. Therefore, measuring the unperturbed shape of a polymeric fluid can be challenging. Here, we study the tip-sample interaction with polystyrene droplets swollen in chloroform vapour, where we can utilize the solvent vapour concentration to adjust the specimen's mechanical properties from a stiff solid to a fluid film...
March 13, 2018: Nanoscale
Hossein Rokni, Wei Lu
We combine conductive atomic force microscopy (CAFM) and molecular dynamics (MD) simulations to reveal the interaction of atomically thin layered materials (ATLMs) down to nanoscale lateral dimension. The setup also allows quantifying, for the first time, the effect of layer number and electric field on the dielectric constant of ATLMs with few-layer down to monolayer thickness. Our CAFM-assisted electrostatic technique shows that high-quality mono- and bilayer graphene is reliably produced at significant yields only by the shear type of bond breaking between layers, whereas the normal type of bond breaking exhibits a very stochastic process mainly due to the coexistence of local delamination and interlayer twist...
February 28, 2018: ACS Central Science
Shuaa Alotaibi, Joshua Samba, Sabin Pokharel, Yucheng Lan, Kelechi Uradu, Ayodeji Afolabi, Ilyas Unlu, Gobind Basnet, Kadir Aslan, Bret N Flanders, Abdellah Lisfi, Birol Ozturk
AC electric fields were utilized in the growth of individual high-aspect ratio cobalt nanowires from simple salt solutions using the Directed Electrochemical Nanowire Assembly method. Nanowire diameters were tuned from the submicron scale to 40 nm by adjusting the AC voltage frequency and the growth solution concentration. The structural properties of the nanowires, including shape and crystallinity, were identified using electron microscopy. Hysteresis loops obtained along different directions of an individual nanowire using vibrating sample magnetometry showed that the magnetocrystalline anisotropy energy has the same order of magnitude as the shape anisotropy energy...
February 26, 2018: Applied Physics Letters
Longhua Xu, Jia Tian, Houqin Wu, Shuai Fang, Zhongyuan Lu, Caifeng Ma, Wei Sun, Yuehua Hu
Anisotropic surface properties of minerals play an important role in a variety of fields. With a focus on the two most intensively investigated silicate minerals (i.e., phyllosilicate minerals and pegmatite aluminosilicate minerals), this review highlights the research on their anisotropic surface properties based on their crystal structures. Four surface features comprise the anisotropic surface chemistry of minerals: broken bonds, energy, wettability, and charge. Analysis of surface broken bond and energy anisotropy helps to explain the cleavage and growth properties of mineral crystals, and understanding surface wettability and charge anisotropy is critical to the analysis of minerals' solution behavior, such as their flotation performance and rheological properties...
March 7, 2018: Advances in Colloid and Interface Science
Qian Zhou, Xinghui Li, Menglin Geng, Haifei Hu, Kai Ni, Lunchao Zhong, Peng Yan, Xiaohao Wang
We propose a new technique to fabricate a highly specialized optical element, a hybrid planar Grating/Fresnel lens (G-Fresnel), which is particularly useful to improve or enable more-affordable miniature/portable spectrometers. Both the Fresnel and the grating surface are fabricated simultaneously by sandwiching soft PDMS between a hard grating and a pre-replicated negative Fresnel surface. Several adhesion reduction techniques are also investigated that help improve both fabrication and cost efficiency (by reducing the solidification time) as well as the lifetime of the mold...
March 5, 2018: Optics Express
Orestis G Andriotis, Sylvia Desissaire, Philipp J Thurner
Tissue hydration is well known to influence tissue mechanics and can be tuned via osmotic pressure. Collagen fibrils are nature's nanoscale building blocks to achieve biomechanical function in a broad range of biological tissues and across many species. Intrafibrillar covalent cross-links have long been thought to play pivotal role for collagen fibril elasticity, but predominantly at large, far from physiological, strains. Performing nanotensile experiments of collagen fibrils at varying hydration levels by adjusting osmotic pressure in situ during atomic force microscopy experiments, we show the power the intrafibrillar non-covalent interactions have for defining collagen fibril tensile elasticity at low fibril strains...
March 12, 2018: ACS Nano
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