Atomic Force Microscopy Methods Research Articles

Модификация структурно-фазового состояния и электрических свойств медьсодержащих фуллеритовых пленок при термическом отжиге в вакууме

Методами растровой и атомно-силовой микроскопии, рентгеновской дифракции, рентгеноспектрального микроанализа и дифракции отраженных электронов исследованы изменения структуры, элементного и фазового состава пленок фуллерит–медь с атомной долей металла 0.5, 1, 2 и 4%, осажденных на окисленные монокристаллические подложки кремния и подвергнутых термическому воздействию в вакууме при разных температурах (470, 520, 570 и 620 К). Установлено, что в результате термического отжига при Т = 520 К (t = 1 ч) формируется нанокристаллическая структура со средним размером структурных элементов 33, 42, 50 и 65 нм для пленок фуллерит–медь с атомной долей металла 0.5, 1, 2 и 4% соответственно. Повышение температуры и времени отжига приводит к увеличению размера структурных элементов и образованию новой фазы Cux C60, относящейся к моноклинной пр. гр. P2/m. Методом электросиловой микроскопии и четырехзондовым методом исследованы изменения локальных электрических свойств и удельного электросопротивления медьсодержащих фуллеритовых пленок при отжиге в вакууме.

Reaction of Spot Radioactive Source with the Energy of 661.7 KeV on the Modification in the Structure of Surface Layer of Metal Composite Material

This paper presents the results of studies of the composite metal radio-protective building material by method of atomic-force probe microscopy, before and after its irradiation with gamma rays of 661.7 keV and absorbed dose up to 2 MGy. Composite metal material is based on the filling of hematite iron ore concentrate and aluminum matrix. This composite material has high technical (physical and mechanical) and radio-protective proprieties. The composite is planned to be employed as a bearing structure at various nuclear facilities.

Toward an Improved Method for Determining the Hamaker Constant of Solid Materials Using Atomic Force Microscopy. I. Quasi-Static Analysis for Arbitrary Surface Roughness

The initial development and preliminary validation of improvements to an existing approach-to-contact atomic force microscopy (AFM) method for determining the Hamaker constant, A, of solid materials is presented. The updated method explicitly accounts for the surface topography of the given substrate, which will lead to improved estimates of A and extend the range of the types of the surfaces to which the method can be applied. After deriving a general van der Waals (vdW) force expression between the AFM cantilever tip, treated as an effective sphere, and a surface with arbitrary roughness, the deflection of the cantilever tip at first contact with the surface, dc, is then obtained for all tip locations. Since the vdW force varies locally along the surface, a distribution of dc-values is obtained for a given value of A. For various model surfaces, we discuss the effect of surface roughness on the resulting dc-distributions, which indicates that surface roughness cannot be accounted for in an approximate way. We also present preliminary experimental validation of the updated method, whereby the predicted dc-distribution of a simplified version of an amorphous silica surface is found to compare favorably with the dc-distribution obtained from AFM experiments.

Возможные антиноцицептивные механизмы, запускаемые наномолярными концентрациями уабаина в первичных сенсорных нейронах

The responses of the primary sensory neuron to the effect of subnanomolar and nanomolar concentrations of ouabain, which correspond to its endogenous concentrations (EO), were investigated. By the method of atomic force microscopy (AFM) it was found that the effect of EO led to an increase in the stiffness of the neuron. It was found using the patch-clamp method that due to the ligand-receptor binding of EO to the Na, K-ATPase/Src complex, the effective charge of the activation gating system of NaV1.8 channels decreases. It was also found that EO-activated triggering of the intracellular cascade, in which the Na, K-ATPase/Src complex acts as a signal transducer, leads to a decrease in the fluorescence intensity of antibodies to NaV1.8 channels, which was revealed using confocal laser scanning microscopy. The results obtained allowed us to suggest that EO, triggering the transducer function of the Na, K-ATPase/Src complex and the corresponding intracellular signaling cascade, is able to modulate the expression of the SCN10A gene, which produces the NaV1.8 channels responsible for encoding nociceptive signals.

Atomic force microscopy in the study of retinal structure

The review addresses the current state of atomic force microscopy (AFM) usage in ophthalmology. Briefly presented here are the history of the development of AFM, principles and modes of operation, its advantages, disadvantages, as well as a comparison with other types of microscopy. The review describes the capabilities of AFM in visualization of various structures of the eye. A significant part of the review is devoted to the study of the retina, which arouses great interest among researchers. In particular, the possibilities of AFM for visualization at the submicron level of various structures in the retina, such as the internal limiting membrane, membrane cells, Müller cells, retinal pigment epithelium in their normal state and in the presence of a pathology (age-related macular degeneration, diabetes mellitus) were reviewed. In addition, several study papers were analyzed, providing a base for the judgement of the mechanical properties of said structures. An AFM study of the visual pigment rhodopsin helped identify its dimeric structure. The stability of the rhodopsin molecule was proved to be determined by the degree of strength of its individual segments connected to each other. The AFM method is a highly accurate method that helps solve many fundamental and practical problems, particularly in ophthalmology.

Микроструктура и элементный состав наноразмерных порошков и пленок редкоземельных ферритов-гранатов на основе Sm-=SUB=-3-=/SUB=-Fe-=SUB=-5-=/SUB=-O-=SUB=-12-=/SUB=-

The synthesis of nanostructured powders and films based on rare-earth ferrite garnet Sm3Fe5O12 was carried out with hydrothermal as well as with the method of precipitation of aqueous solutions of nitrates on the substrate surface. Using atomic force microscopy (AFM), scanning electron microscopy (SEM), Raman spectroscopy (Raman), and X-ray phase analysis (XRD), the topology of the surface and the phase composition of the samples were studied. According to AFM and SEM, particle sizes were evaluated and the structural features of powders and films were analyzed. Raman spectroscopy (RS) and X-ray phase analysis were used to examine the chemical composition and crystal structures of synthesized samples. The possibility of simultaneous investigation of the same sample area with AFM methods and Raman spectroscopy made it possible to obtain data of the chemical composition, the presence of impurities and defects, and the shape of macromolecules. Taking into account the set of obtained results, it is shown that materials based on Sm3Fe5O12, due to their structural features and physics-chemical parameters, can be used as filters for industrial sewage treatment.

Tính chất quang xúc tác của các cấu trúc dị thể TiO2/ZnO

In this paper, three kinds of heterostructure of TiO2/ZnO were fabricated by combining electrochemical, sputtering and/or hydrothermal methods. The crystal structure and morphology of ZnO/TiO2 were studied by the X-ray diffraction method (XRD), scanning electron microscopy method (SEM), atomic force microscopy method (AFM). The photocatalytic performance of the TiO2/ZnO heterostructures was examined by monitoring the degradation of methylene blue (MB) under ultraviolet (UV) or visible light irradiation. The results show that all the TiO2/ZnO heterostructures exhibited the right crystal structure of ZnO and TiO2 phases. All the TiO2/ZnO heterostructures presented superior photocatalytic activities as compared to the TiO2 or ZnO single material. In addition, amongst the three heterostructures, the TiO2-hydrothermal/ZnO rod obtained the highest reaction rate constant (0,065 min-1; 0,056 min-1), followed by TiO2/ZnO rod structure (0,054 min-1; 0,031 min-1), and double-layer TiO2/ZnO(0,05 min-1; 0,021 min-1) under UV light and visible light respectively, primarily due to the effects of enhanced charge separation and generation and the characteristics of the surface area of each heterostructure.

Research of the structure of teeth enamel mineral component in connective tissue dysplasia by densitometry and atomic force microscopy in the late postpartum ontogenesis period

Цель работы — дать количественную и качественную характеристику структуре минерального компонента эмали ретинированных зубов при дисплазии соединительной ткани и без нее в различные периоды позднего постнатального онтогенеза человека методами денситометрии и атомно-силовой микроскопии. Материалы и методы. Удаляли 3.8, 4.8 зубы, не имеющие контакта с ротовой жидкостью, у 60 мужчин с дисплазией соединительной ткани и без нее (возрастные группы: 31—40, 41—50, 51—60 лет). Денситометрическую оценку плотности неорганического компонента эмали проводили в программе Kodak Dental Systems. Форму, упаковку, расстояние между эмалевыми призмами анализировали в программе Image Analysis NT—VDT. Результаты. Установлено, что после 30 лет в ретинированных зубах наблюдается выраженный эмалевый метаболизм, характеризующийся изменением формы, плотности упаковки и расстоянием между эмалевыми призмами. Показано, что при дисплазии соединительной ткани темпы созревания эмалевых призм в позднем постнатальном периоде онтогенеза снижены. Заключение. При дисплазии соединительной ткани наблюдается картина незавершенного амелогенеза с низкой плотностью упаковки и большим расстоянием между эмалевыми призмами.

Bactericidal Effect of Cotton Fabric Treated with Polymer Solution Containing Silver Nanoparticles of Different Sizes and Shapes

Stable silver nanoparticles in solutions of sodium-carboxymethylcellulose (Na-CMC) were synthesized and their structure and physico-chemical properties were evaluated. The form and sizes of silver nanoparticles formed in solutions of CMC and cotton fabrics were studied using UV-VIS spectroscopy, atomic force microscopy and transmission electron microscopy methods. It was found that silver nitrate concentration increase in sodium carboxymethylcellulose solutions, as well as photoirradiation of the hydrogel lead to the changes of the silver nanoparticles size and shape. Investigations have also shown that spherical silver nanoparticles with sizes of 5-35 nm and content of 0.0086 mass% in cotton fabrics possess high bactericidal activity. Stabilization of silver nanoparticles has preserved bactericidal and bacteriostatic activities during the washing of cotton fabrics and textiles on their base.

Boundary slip measurement and mechanism analysis in ultraviolet nanoimprint lithography of subwavelength moth-eye nanostructure

Subwavelength moth-eye nanostructure has been commonly used to reduce the surface reflection of optoelectronic devices, such as liquid crystal display, solar cell, image sensor, etc. Among various fabrication processes, the ultraviolet nanoimprint lithography (UV-NIL) technique combined with anodic aluminum oxide (AAO) mold provides an effective way for high-precision and high-efficiency fabrication of moth-eye nanostructure. To obtain high-precision moth-eye nanostructure, accurate analysis of UV-curing resin filling process into nanoscale AAO mold is necessary. In this research, the boundary slip phenomenon in nanoscale flow was investigated using atomic force microscope (AFM) method and it was found that boundary slip could produce a significant effect on nanoscale flow. Besides, the slip law on rough surfaces was further investigated. It was found the slip length reduced from 23.7 nm to 12.7 nm as roughness Ra increased from 0.47 nm to 3.18 nm, indicating that the roughness suppressed the slip motion. Moreover, the physical mechanism of boundary slip was also revealed, that was, the fluid properties and wettability caused intrinsic slip motion while the roughness could suppress intrinsic slip motion due to enhancement of internal viscous dissipation loss. The research could provide guidance for a more accurate understanding of boundary slip in nanoscale flow and high-precision fabrication of subwavelength moth-eye nanostructure.

Nanoscale Mapping of Extrinsic Interfaces in Hybrid Solid Electrolytes

Summary Inorganic-organic hybrid solid electrolytes are promising material systems for all solid-state batteries (ASSBs). These electrolytes contain numerous solid | solid interfaces that govern transport pathways, electrode | electrolyte compatibility, and durability. This paper evaluates the role that electrode | electrolyte interfaces and electrolyte structure have on electrochemical performance. Atomic force microscopy techniques reveal how mechanical, adhesion, and morphological properties transform in a series of model hybrid solid electrolytes. These measurements are mapped to sub-surface microstructural features using synchrotron nano-tomography. Hybrid solid electrolytes with shorter polymer chains demonstrate a higher adhesion ( > 100 nN), Young's Modulus (6.4 GPa), capacity (114.6 mAh/g), and capacity retention (92.9%) than hybrid electrolytes with longer polymer chains (i.e., higher molecular weight). Extrinsic interfacial properties largely dictate electrochemical performance in ASSBs. Microstructural control over inorganic constituents may provide a means for tailoring interfacial properties in hybrid solid electrolytes.

Gold Nanowires/Fibrin Nanostructure as Microfluidics Platforms for Enhancing Stem Cell Differentiation: Bio-AFM Study.

Organ-on-a-chip technology has gained great interest in recent years given its ability to control the spatio-temporal microenvironments of cells and tissues precisely. While physical parameters of the respective niche such as microchannel network sizes, geometric features, flow rates, and shear forces, as well as oxygen tension and concentration gradients, have been optimized for stem cell cultures, little has been done to improve cell-matrix interactions in microphysiological systems. Specifically, detailed research on the effect of matrix elasticity and extracellular matrix (ECM) nanotopography on stem cell differentiation are still in its infancy, an aspect that is known to alter a stem cell’s fate. Although a wide range of hydrogels such as gelatin, collagen, fibrin, and others are available for stem cell chip cultivations, only a limited number of elasticities are generally employed. Matrix elasticity and the corresponding nanotopography are key factors that guide stem cell differentiation. Given this, we investigated the addition of gold nanowires into hydrogels to create a tunable biointerface that could be readily integrated into any organ-on-a-chip and cell chip system. In the presented work, we investigated the matrix elasticity (Young’s modulus, stiffness, adhesive force, and roughness) and nanotopography of gold nanowire loaded onto fibrin hydrogels using the bio-AFM (atomic force microscopy) method. Additionally, we investigated the capacity of human amniotic mesenchymal stem cells (hAMSCs) to differentiate into osteo- and chondrogenic lineages. Our results demonstrated that nanogold structured-hydrogels promoted differentiation of hAMSCs as shown by a significant increase in Collagen I and II production. Additionally, there was enhanced calcium mineralization activity and proteoglycans formation after a cultivation period of two weeks within microfluidic devices.

Antibacterial effect of cotton fabric treated with silver nanoparticles of different sizes and shapes

Stable silver Nanoparticles in solutions of sodium-carboxymethylcellulose (Na-CMC) were synthesized, and their structure and physico-chemical properties were studied. The form and sizes of silver nanoparticles formed in solutions of CMC and cotton fabrics were studied using UV-VIS spectroscopy, atomic force microscopy and transmission electron microscopy methods. It was found that the silver nitrate concentration increase in sodium carboxymethylcellulose solutions, as well as photoirradiation of the hydrogel lead to the changes of the silver nanoparticles size and shape. Investigations have shown that spherical silver nanoparticles with sizes of 5-35nm and content of 0.0086 mass% in cotton fabrics possess high bactericidal activity. Stabilization of silver nanoparticles has preserved bactericidal and bacteriostatic activities during the washing of cotton fabrics and textiles on their base.

Conjugates of Gold Nanoparticles and Antitumor Gold(III) Complexes as a Tool for Their AFM and SERS Detection in Biological Tissue.

Citrate-capped gold nanoparticles (AuNPs) were functionalized with three distinct antitumor gold(III) complexes, e.g., [Au(N,N)(OH)2][PF6], where (N,N)=2,2′-bipyridine; [Au(C,N)(AcO)2], where (C,N)=deprotonated 6-(1,1-dimethylbenzyl)-pyridine; [Au(C,N,N)(OH)][PF6], where (C,N,N)=deprotonated 6-(1,1-dimethylbenzyl)-2,2′-bipyridine, to assess the chance of tracking their subcellular distribution by atomic force microscopy (AFM), and surface enhanced Raman spectroscopy (SERS) techniques. An extensive physicochemical characterization of the formed conjugates was, thus, carried out by applying a variety of methods (density functional theory—DFT, UV/Vis spectrophotometry, AFM, Raman spectroscopy, and SERS). The resulting gold(III) complexes/AuNPs conjugates turned out to be pretty stable. Interestingly, they exhibited a dramatically increased resonance intensity in the Raman spectra induced by AuNPs. For testing the use of the functionalized AuNPs for biosensing, their distribution in the nuclear, cytosolic, and membrane cell fractions obtained from human lymphocytes was investigated by AFM and SERS. The conjugates were detected in the membrane and nuclear cell fractions but not in the cytosol. The AFM method confirmed that conjugates induced changes in the morphology and nanostructure of the membrane and nuclear fractions. The obtained results point out that the conjugates formed between AuNPs and gold(III) complexes may be used as a tool for tracking metallodrug distribution in the different cell fractions.

A New Algorithm for Measuring the Young’s Modulus of Suspended Nanoobjects by the Bending-Based Test Method of Atomic Force Microscopy

Atomic force microscopy is a unique technique for probing the mechanical properties of nanostructures. Using the bending-based test method, one can measure the Young’s modulus of the material of a suspended object, a nanobridge. This article presents a new, improved version of the bending-based test method. A special algorithm is elaborated to establish the nanobridge span length and to identify the boundary conditions of the nanobridge fixation. In particular, to realize this algorithm we propose a model of the beam with transformable boundary conditions (between clamped and supported beam model cases) varied by the only fitting parameter. To illustrate the main features of the developed bending-based test method application, the Young’s modulus measurements of mineral chrysotile nanoscrolls, forming the nanobridges across the pores of a track membrane, are presented.

Microscopy investigation of conical and layered nanowires

This article discusses the use of scanning microscopy in the study of one-dimensional nanostructures – nanowires. The nanowires were produced by matrix synthesis. Atomic force microscopy (AFM) of conical nanowires was carried out, and layered nanowires were investigated by AFM and magnetic force microscopy (MFM) methods.

Optimization of physicochemical and optical properties of nanocrystalline TiO2 deposited on porous silicon by metal-organic chemical vapor deposition (MOCVD)

Titanium dioxide (TiO2) is very employed in solar cells due to its interesting physicochemical and optical properties allowing high device performances. Considering the extension of applications in nanotechnologies, nanocrystalline TiO2 is very promising for nanoscale components. In this work, nanocrystalline TiO2 thin films were successfully deposited on porous silicon (PSi) by metal organic chemical vapor deposition (MOCVD) technique at temperature of 550 °C for different periods of times: 5, 10 and 15 min. The objective was to optimize the physicochemical and optical properties of the TiO2/PSi films dedicated for photovoltaic application. The structural, morphological and optical properties of the elaborated TiO2/PSi samples were analyzed by means of x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), atomic force microscopy (AFM), photoluminescence (PL) and UV-Visible absorption spectroscopy methods. The effect of deposition time on the microstructural properties which influences the optical characteristics of the obtained samples was also examined. The XRD analysis confirms the nanocrystalline structure of the deposited TiO2 composed only by anatase phase. The SEM characterization evidenced an increase in the TiO2 film thickness showing more uniform surfaces as the deposition time rises. Correspondingly, the surface roughness increases with the particle size and film thickness as indicated by AFM studies. The TiO2/PSi/Si sandwich structure evidenced by cross-sectional SEM confirms the good adherence of the TiO2 nanocrystalline film on the porous silicon forming with silicon a composite material. The UV-Vis measurements showed a considerable enhancement in optical absorption of porous silicon after the deposition of TiO2 films. Indeed, the TiO2 coatings deposited on PSi for 15 min with thickness of 200 nm have the best structure quality and exhibit, consequently, the highest absorption. From these interesting results, we demonstrate the viability of the use of the MOCVD as reproducible process for the elaboration of high-quality TiO2/PSi films.

A novel method to remove impulse noise from atomic force microscopy images based on Bayesian compressed sensing.

A novel method based on Bayesian compressed sensing is proposed to remove impulse noise from atomic force microscopy (AFM) images. The image denoising problem is transformed into a compressed sensing imaging problem of the AFM. First, two different ways, including interval approach and self-comparison approach, are applied to identify the noisy pixels. An undersampled AFM image is generated by removing the noisy pixels from the image. Second, a series of measurement matrices, all of which are identity matrices with some rows removed, are constructed by recording the position of the noise-free pixels. Third, the Bayesian compressed sensing reconstruction algorithm is applied to recover the image. Different from traditional compressed sensing reconstruction methods in AFM, each row of the AFM image is reconstructed separately in the proposed method, which will not reduce the quality of the reconstructed image. The denoising experiments are conducted to demonstrate that the proposed method can remove the impulse noise from AFM images while preserving the details of the image. Compared with other methods, the proposed method is robust and its performance is not influenced by the noise density in a certain range.

A detailed investigation of the chloride-induced corrosion of mild steel in the presence of combined green organic molecules of Primrose flower and zinc cations

This study aims at finding a novel natural species for the corrosion mitigation of the mild steel immersed in saline solutions. For this purpose, for the very first time, the inhibition potent of different blends of the petal extract of Primrose flower (PPE) and zinc cations were studied. The PPE and PPE:Zn composite adsorption on the steel substrate was examined by Fourier-transform infrared spectroscopy (FT-IR). Surface characterizations of the metal surface were carried out using scanning electron microscopy (SEM), ultraviolet-visible spectroscopy (UV–Vis), grazing incidence X-ray diffraction (GIXRD), atomic force microscopy (AFM) method and contact angle measurement (CA). The inhibition actions of the PPE:Zn containing solutions were evaluated by means of the electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization spectroscopy (PPS). Surface studies proved the chelation between the organic molecules of the PPE and Fe2+/Zn2+ cations. In the presence of PPE and Zn alone, the inhibition efficiencies were in the range of 40–80% while the mixture of 300 ppm PPE + 700 ppm Zn has resulted in a 95.3% protection degree. It was found that the protection mechanism was mixed-type with anodic reaction retardation dominancy. In addition, computational methods (density functional theory, DFT and molecular dynamics, MD and Monte Carlo, MC) were utilized to study the reactivity and interfacial adsorption of extract molecules. These computations ensured the adsorption of green molecules over the substrate of the target.

Highly conductive polyporphyrin films obtained by superoxide-assisted electropolymerization of para – aminophenyl porphyrin

The process of deposition of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (H2T(4-NH2Ph)P) electopolymer films induced by superoxide anion radical in dimethyl sulfoxide (DMSO) has been studied. By the methods of electrode impedance spectroscopy and atomic-force microscopy it has, for the first time, been proved that it is possible to form a poly-H2T(4-NH2Ph)P film in DMSO in potentiostatic conditions at oxygen electroreduction potentials. Charge transfer through the poly-H2T(4-NH2Ph)P film has been characterized by modeling electrochemical impedance spectroscopy (EIS) data. It has been shown that in potentiostatic conditions, the formation of a poly-H2T(4-NH2Ph)P film induced by superoxide anion radical consists of at least two stages. At the first stage, the resistance of the surface film changes insignificantly, and at the second one it increases approximately linearly over time. Using the vibrational spectroscopy we have determined the type of binding of monomer fragments in the polyporphyrin film. The morphology and thickness of the deposited polyporphyrin films have been studied by the methods of atomic force microscopy. Based on the resistance and thickness estimates, we have determined the value of specific conductivity of the obtained film (about 4.2•10−4 S cm−1). The metal-free aminophenyl porphyrin electopolymer was also successfully tested as an electrocatalyst for the oxygen reduction reaction.