Evaluation of surface topography changes in three NiTi file systems using rotary and reciprocal motion: An atomic force microscopy study

Aim: To evaluate the surface topography changes in three nickel‐titanium (NiTi) file systems using either rotary or reciprocal motion using atomic force microscopy (AFM), and to determine the effect of scanning area on the AFM results in this study. Methodology: Five points on a F2 Protaper file, R25 Reciproc file, and a Primary file from WaveOne systems were scanned preoperatively in 1 × 1 and 5 × 5 µm² with an AFM device that can scan an intact (not sectioned) file. One standardized resin block was used for each instrument, according to the manufacturer's recommendations. Points were re‐scanned postoperatively using the same AFM and settings. Root‐mean‐square (RMS) and roughness average (Ra) values were obtained. The preoperative and postoperative surface topographies were compared separately in terms of RMS and Ra values. The surface topography change scores were analyzed using Kruskal–Wallis and Mann–Whitney U tests using a 0.10 significance level. Results: There were no significant differences preoperatively among the NiTi file systems in 1 × 1 or 5 × 5 µm² areas. Postoperatively, the WaveOne Primary had more surface irregularities (significant for 5 × 5 µm² scan in Ra evaluation). Conclusions: Three‐dimensional AFM images of instrument surfaces showed topographic irregularities preoperatively and postoperatively. AFM results differ depending on the scanning area and file used. Microsc. Res. Tech. 77:177–182, 2014. © 2013 Wiley Periodicals, Inc.     

Topographic characterization of unworn contact lenses assessed by atomic force microscopy and wavelet transform

This paper analyses the three‐dimensional (3‐D) surface morphology of optic surface of unworn contact lenses (CLs) using atomic force microscopy (AFM) and wavelet transform. Refractive powers of all lens samples were 2.50 diopters. Topographic images were acquired in contact mode in air‐conditioned medium (35% RH, 23°C). Topographic measurements were taken over a 5 µm × 5 µm area with 512 pixel resolution. Resonance frequency of the tip was 65 kHz. The 3‐D surface morphology of CL unworn samples revealed (3‐D) micro‐textured surfaces that can be analyzed using (AFM) and wavelet transform. AFM and wavelet transform are accurate and sensitive tools that may assist CL manufacturers in developing CLs with optimal surface characteristics. Microsc. Res. Tech. 78:1026–1031, 2015. © 2015 Wiley Periodicals, Inc.     

Rapid and Highly Sensitive Method for Protein Determination in Biological Samples with m‐Nitrophenylfluorone‐Mo(VI) Complex as a Spectral Probe

Abstract

A simple, rapid, highly sensitive, and selective method for detecting protein in biological samples has been developed, which is based on the interaction between protein and m‐nitrophenylfluorone‐Mo(VI) complex as a spectral probe. The optimum condition for the reaction is investigated. Bovine serum albumin (BSA) obeys Beer's law up to 10 µg · mL^?1, having a molar absorption coefficient of 8.51×10⁶ L · mol^?1 · cm^?1 at 535 nm. Many amino acids and metal ions do not interfere. The results of determination for biological samples are comparable to those obtained by the Bradford method. Meanwhile, the binding number is also determined.     

Simultaneous Determination of Six Trace Elements in Plant Medicines by Derivative Adsorption Waves in Conjunction with a Microwave Technique

Abstract

Complex adsorption waves of Cu(II), Pb(II), Cd(II), Ni(II), Co(II), and Zn(II) in substrate solution (pH=9.26) of diacetyldioxime‐ammonia‐ammonium chloride‐sodium citrate‐gelatin‐sodium sulfite were studied and a new method for determination of the six trace elements in aqueous solutions was developed. The results show that there are sensitive adsorption waves of Cu(II), Pb(II), Cd(II), Ni(II), Co(II), and Zn(II) complexes at about ?0.45, ?0.61,?0.78, ?1.07, ?1.23, and ?1.38 V, respectively. The method is easy to operate and is able to determine these trace elements in aqueous solutions rapidly and simultaneously. When the signal‐to‐noise ratio equals 3, the detection limits of copper, lead, cadmium, nickel, cobalt, and zinc are 3.2×10^?4, 4.8×10^?3, 1.9×10^?3, 1.7×10^?5, 2.1×10^?6, and 1.0×10^?3 µg/cm³. Good linear relationships exist between the concentrations and the current peaks when copper, lead, cadmium, nickel, cobalt, and zinc concentrations are within 6.5×10^?4～10⁰, 9.3×10^?3～10, 4.1×10^?3～10, 3.2×10^?5～10^?1, 4.0×10^?6～10^?2, and 2.1×10^?3～10 µg/cm³, respectively. In conjunction with a microwave assimilation technique, the method has been used in the rapid and simultaneous determination of these trace elements in some plant medicines with satisfactory results.     

Micromorphology analysis of TiO2 thin films by atomic force microscopy images: The influence of postannealing

This work describes an analysis of titanium dioxide (TiO₂) thin films prepared on silicon substrates by direct current (DC) planar magnetron sputtering system in O₂/Ar atmosphere in correlation with three‐dimensional (3D) surface characterization using atomic force microscopy (AFM). The samples were grown at temperatures 200, 300, and 400°C on silicon substrate using the same deposition time (30 min) and were distributed into four groups: Group I (as‐deposited samples), Group II (samples annealed at 200°C), Group III (samples annealed at 300°C), and Group IV (samples annealed at 400°C). AFM images with a size of 0.95 μm × 0.95 μm were recorded with a scanning resolution of 256 × 256 pixels. Stereometric analysis was carried out on the basis of AFM data, and the surface topography was described according to ISO 25178‐2:2012 and American Society of Mechanical Engineers (ASME) B46.1‐2009 standards. The maximum and minimum root mean square roughnesses were observed in surfaces of Group II (Sq = 7.96 ± 0.1 nm) and Group IV (Sq = 3.87 ± 0.1 nm), respectively.     

A compact CCD‐monitored atomic force microscope with optical vision and improved performances

A novel CCD‐monitored atomic force microscope (AFM) with optical vision and improved performances has been developed. Compact optical paths are specifically devised for both tip‐sample microscopic monitoring and cantilever's deflection detecting with minimized volume and optimal light‐amplifying ratio. The ingeniously designed AFM probe with such optical paths enables quick and safe tip‐sample approaching, convenient and effective tip‐sample positioning, and high quality image scanning. An image stitching method is also developed to build a wider‐range AFM image under monitoring. Experiments show that this AFM system can offer real‐time optical vision for tip‐sample monitoring with wide visual field and/or high lateral optical resolution by simply switching the objective; meanwhile, it has the elegant performances of nanometer resolution, high stability, and high scan speed. Furthermore, it is capable of conducting wider‐range image measurement while keeping nanometer resolution. Microsc. Res. Tech. 76:931–935, 2013. © 2013 Wiley Periodicals, Inc.     

Effects of Galla chinensis on the surface topography of initial enamel carious lesion: an atomic force microscopy study

To investigate the effect of Galla chinensis on the surface topography of initial enamel carious lesion, atomic force microscope (AFM) was used, and it was a new AFM application in enamel de‐/remineralization research. Bovine sound enamel slabs were demineralized to produce initial carious lesion in vitro. Then, the lesions were exposed to a pH‐cycling regime for 12 days. Each daily cycle included 4×1 min applications with one of three treatments: negative control group: deionized water; positive control group: 1 g/L aqueous solutions of NaF; experimental group: 4 g/L aqueous solutions of G. chinensis extract (GCE). The surface topography and roughness were investigated on the enamel slabs before and after pH‐cycling by AFM. 3D AFM images revealed the surface topographical changes of GCE‐treated enamel. Significant difference existed before and after the pH‐cycling among the groups. AFM offers a powerful tool for enamel de‐/remineralization research. The surface roughness results provide the evidences to remineralization of carious lesion, and indicate the potential of G. chinensis in promoting the remineralization. G. chinensis may become one more promising agent for caries prevention. SCANNING 31: 195–203, 2009. © 2010 Wiley Periodicals, Inc.     

Rippling on Wear Scar Surfaces of Nanocrystalline Diamond Films After Reciprocating Sliding Against Ceramic Balls

The formation of nanoscopic ripple patterns on top of material surfaces has been reported for different materials and processes, such as sliding against polymers, high-force scanning in atomic force microscopy (AFM), and surface treatment by ion beam sputtering. In this work, we show that such periodic ripples can also be obtained in prolonged reciprocating sliding against nanocrystalline diamond (NCD) films. NCD films with a thickness of 0.8 µm were grown on top of silicon wafer substrates by hot-filament chemical vapor deposition using a mixture of methane and hydrogen. The chemical structure, surface morphology, and surface wear were characterized by Raman spectroscopy, scanning electron microscopy (SEM), and AFM. The tribological properties of the NCD films were evaluated by reciprocating sliding tests against Al₂O₃, Si₃N₄, and ZrO₂ counter balls. Independent of the counter body material, clear ripple patterns with typical heights of about 30 nm induced during the sliding test are observed by means of AFM and SEM on the NCD wear scar surfaces. Although the underlying mechanisms of ripple formation are not yet fully understood, these surface corrugations could be attributed to the different wear phenomena, including a stress-induced micro-fracture and plastic deformation, a surface smoothening, and a surface rehybridization from diamond bonding to an sp ² configuration. The similarity between ripples observed in the present study and ripples reported after repeated AFM tip scanning indicates that ripple formation is a rather universal phenomenon occurring in moving tribological contacts of different materials.     

Electrochemical Behavior of Uric Acid at a Meso‐2,3‐Dimercaptosuccinic Acid Self‐Assembled Gold Electrode

Abstract

The fabrication and electrochemical characteristics of a meso‐2,3‐dimercaptosuccinic acid (DMSA) self‐assembled monolayer modified gold electrode were investigated. The DMSA self‐assembled electrode can enhance the electrochemical stability of uric acid (UA) and the electrochemical reaction of UA on the DMSA electrode has been studied by cyclic voltammetry and electrochemical quartz crystal microbalance. Some electrochemical parameters, such as diffusion coefficient, standard rate constant, electron transfer coefficient, and protons transfer number have been determined for the electrochemical behavior on the DMSA self‐assembled monolayer electrode. The electrode reaction of UA is an irreversible process which is controlled by the diffusion of UA with two electrons and two protons transfer at the DMSA/Au electrode. In phosphate buffer (pH 5.0), the peak current is proportional to the concentration of UA in the range of 8.0×10^?5?1.0×10^?2 mol L^?1 and 8.0×10^?5?8.0×10^?3 mol L^?1 for the cyclic voltammetry and differential pulse voltammetry methods with the detection limits of 1×10^?6 and 8×10^?7 mol L^?1, respectively. This method can be applied to the determination of the UA concentration.     

Imaging and studying human topoisomerase I on mica surfaces in air and in liquid by atomic force microscopy

In this study, the topography of human topoisomerase I (TOPO I) on mica surfaces in air and in liquid has been studied by atomic force microscopy (AFM). The average height of TOPO I on mica surface in air measured by AFM was 2.59±0.32 nm. After adsorption of the 0.3 U/µl TOPO I on mica surfaces for 2 h, and then imaged in liquid by AFM, well‐separated single TOPO I was observed. The average height of TOPO I on mica surfaces in liquid measured by AFM was 2.93±0.42 nm. After adsorption of the 4 U/µl TOPO I on mica surfaces for 1.5 h, TOPO I monolayer can be formed. The produced TOPO I monolayer on mica was flat and exhibited good stability. SCANNING 31: 160–166, 2009. © 2009 Wiley Periodicals, Inc.     

The role of substrates on the structural,optical, and morphological properties of zno nanotubes prepared by spray pyrolysis

ZnO films were deposited onto glass, ITO coated glass, and sapphire substrate by spray pyrolysis, and subsequently annealed at the same temperature of 400°C for 3 h. The role of substrate on the properties of ZnO films was investigated. The structural and optical properties of the films were investigated by X‐ray diffractometer (XRD) and photoluminescence (PL) spectrophotometer, respectively. The surface morphology of the nanostructured ZnO film was investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Crystallographic properties revealed that the ZnO films deposited on sapphire and ITO substrates exhibit a strong c‐axis orientation of grains with hexagonal wurtzite structure. Extremely high UV emission intensity was determined in the film on ITO. The different luminescence behaviors was discussed, which would be caused by least value of strain in the film. Films grown on different substrates revealed differences in the morphology. ZnO films on ITO and sapphire substrates revealed better morphology than that of the film on glass. AFM images of the films prepared on ITO show uniform distribution of grains with large surface roughness, suitable for application in dye sensitized solar cells. Microsc. Res. Tech. 77:211–215, 2014. © 2013 Wiley Periodicals, Inc.     

Flow‐Injection Chemiluminescence Determination of Catecholamines

Abstract

A new flow‐injection chemiluminescence method is proposed for the determination of catecholamines, including adrenaline, dopamine, and l‐Dopa. The method is based on the chemiluminescence (CL) produced during the oxidation of catecholamines by sodium hypochlorite in an alkaline medium. The CL intensity is greatly increased when 2,7‐dichlorofluoresceine is used as a sensitizer. The calibration graphs are linear in the range of 3–80 µg/mL for adrenaline and l‐Dopa and 3–50 µg/mL for dopamine. The influence of foreign compounds was studied and the method was applied to the determination of catecholamines in pharmaceutical formulations.     

Error analysis and regression mode of the V‐grooved sample in the atomic force microscope simulation measurement mode by the molecular mechanics

Based on the molecular mechanics, this study uses the two‐body potential energy function to construct a trapezoidal cantilever nano‐scale simulation measurement model of contact mode atomic force microscopy (AFM) under the constant force mode to simulate the measurement the nano‐scale V‐grooved standard sample. We investigate the error of offset distance of the cross‐section profile when using the probes with different trapezoidal cantilever probe tip radii (9.5, 8.5, and 7.5 Å) to scan the peak of the V‐grooved standard sample being reduced to one‐tenth (1/10) of its size, and use the offset error to inversely find out the regression equation. We analyze how the tip apex as well as the profile of the tip edge oblique angle and the oblique edge angle affects the offset distance. Furthermore, a probe with a larger radius of 9.5 nm is used to simulate and measure the offset error of scan curve, and acquire the regression equation. By the conversion proportion coefficient of size (ω), and revising the size‐reduced regression equation during the small size scale, a revised regression equation of a larger size scale can be acquired. The error is then reduced, further enhancing the accuracy of the AFM scanning and measurement. SCANNING 31: 147–159, 2009. © 2009 Wiley Periodicals, Inc.     

Substrate influence on cell shape and cell mechanics: HepG2 cells spread on positively charged surfaces

A human hepatoma cell line (HepG2) was cultured on positively and negatively charged polyelectrolytes. Cell/surface adhesion and cell shape evolution were followed with quartz microbalance with dissipation (QCM‐D) and optical microscopy as a function of time, respectively. In particular, substrates coated with poly(ethyleneimine) (PEI) led to fast cell attachment and further spreading, with average maximum frequency Δf = 79 Hz and dissipation ΔD = 40 × 10^?6. On the contrary, no cell spreading was observed on poly(sodium‐4‐styrenesulfonate) (PSS), with Δf = 33 Hz and ΔD = 4.5 × 10^?6. Atomic force microscopy (AFM) was used to investigate the influence of cell shape on its mechanical properties. Considering the cells as an homogenous solid material, the corresponding elastic modulus was estimated using the Hertz model. The elastic modulus was calculated at the central part of the cell, and the average values obtained were 191 ± 14 Pa and 941 ± 58 Pa for cells adsorbed on PSS and PEI, respectively. Thus, different cell–substrate interaction implied different cell mechanical properties reflected in a higher elastic modulus for stronger cell/substrate interaction. The combination of QCM‐D, AFM, and optical microscopy allowed the online study of the cell adhesion process, and the mechanical properties of the adhered cells. Microsc. Res. Tech. 2009. © 2009 Wiley‐Liss, Inc.     

PVC Membrane Sensor for Potentiometric Determination of Atropine in Some Pharmaceutical Formulations

Abstract

The construction and general performance of a novel potentiometric membrane sensor for determination of atropine has been developed. It is based on the formation of the ion association complex of the atropinium cation with phosphotungstate counter anion as electroactive material dispersed in a PVC matrix, β‐Cyclodextrin and o‐nitrophenyl octyl ether serve as a plasticizer. The sensor shows a fast, stable, near Nernstian response for 1×10^?2 M to 1×10^?6 M atropine at 25°C over the pH range of 3–8 with a cationic slope of 51±0.5 mV/decade. The lower detection limit is 8×10^?7 M and the response time is 20–45 sec. Selectivity coefficients of atropine, relative to a number of interfering substances, were investigated. There are negligible interferences caused by most of the studied cations, anions, and pharmaceutical excipients. The direct determination of atropine shows an average recovery of 98.6% and a mean relative standard deviation (RSD) of 1.6% at 100 µg/mL. The results obtained by determination of atropine in some formulations (atropine injection and eye drops) are favorably comparable with those obtained by the British Pharmacopoeia method. The developed membrane electrode has been used as end point indicator electrode for some potentiometric titrations.     

A SMALL-ANGLE X-RAY SCATTERING STATION AT BEIJING SYNCHROTRON RADIATION FACILITY

This article presents the development and current state of a small-angle X-ray scattering station at beamline 1W2A of the Beijing Synchrotron Radiation Facility, China. The source of the beamline is introduced from a 14-pole wiggler. A triangular bending Si(111) crystal is used to horizontally focus the beam and provide a monochromatic X-ray beam (8.052 keV). A bending cylindrical mirror coated with rhodium downstream from the monochromator is used to vertically focus the beam. The X-ray beam is focused on the detector which is fixed at 30 m from the source. The focused beam size (full width at half maximum) is 1.4 × 0.2 mm² (horizontal × vertical) with a flux of 5.5 × 10¹¹ phs/s at 2.5 GeV and 250 mA. Besides the routine mode of small-angle X-ray scattering, the combination of small- and wide-angle X-ray scattering, grazing incidence small-angle X-ray scattering, and time-resolved small-angle X-ray scattering in sub-second level are also available for the users. Dependent on the measurement requirements, several detectors can be chosen for the collection of scattering signals. Furthermore, multiple sample environments, including temperature, stress-strain, and liquid sampling are available for in situ measurements. In a typical camera length of 1.5 m, the small-angle X-ray scattering resolution is about 115 nm. The steady operation of the small-angle X-ray scattering station at Beijing Synchrotron Radiation Facility not only provides the small-angle X-ray scattering beam time for users, but also promotes the development and application of these techniques in China.     

Micromorphological characterization of zinc/silver particle composite coatings

The aim of this study was to evaluate the three‐dimensional (3D) surface micromorphology of zinc/silver particles (Zn/AgPs) composite coatings with antibacterial activity prepared using an electrodeposition technique. These 3D nanostructures were investigated over square areas of 5 μm × 5 μm by atomic force microscopy (AFM), fractal, and wavelet analysis. The fractal analysis of 3D surface roughness revealed that (Zn/AgPs) composite coatings have fractal geometry. Triangulation method, based on the linear interpolation type, applied for AFM data was employed in order to characterise the surfaces topographically (in amplitude, spatial distribution and pattern of surface characteristics). The surface fractal dimension D_f, as well as height values distribution have been determined for the 3D nanostructure surfaces. Microsc. Res. Tech. 78:1082–1089, 2015. © 2015 The Authors published by Wiley Periodicals, Inc.     

WiFi‐controlled portable atomic force microscope

This article proposes to develop a WiFi‐controlled portable atomic force microscope (AFM). The AFM consists of a horizontal probe, controlling circuits, digital to analog (D/A) and analog to digital (A/D) interfaces, a microcomputer (Raspberry Pi, RPi), and a laptop. The proposed AFM uses a pocket‐size power supply to drive the controlling circuits, the D/A and A/D interfaces, as well as the RPi that constructs network hotspots and generates scanning signals. With special design and integration of the whole system, both of the AFM probe and electronic controlling system are portable. At a distance of 50 m from the proposed AFM, experiments in the constant height mode and the constant force mode are conducted to evaluate its performance. The results show that this WiFi‐controlled AFM has a maximum scan range of 3.6 × 3.6 μm² with nanometer order resolution. Meanwhile, it achieves satisfactory image contrast, stability, and repeatability. Compared with conventional AFMs, the AFM proposed in this paper no longer relies on commercial AC mains supply or high‐voltage DC power supply, and realizes WiFi‐controlled AFM scanning and imaging in 50 m or farther without wire or network cable connection to a laptop or a desktop computer. Given credits to these features, WiFi‐controlled AFMs are expected to own a wider range of application, especially in isolated environments, outdoor researches, or even fieldwork investigations.     

Near Infrared Raman Spectroscopy System for Real Time Monitoring of Fast Processes: A Resin Composite Photopolymerization Application

Abstract

This work describes the implementation of a technique for data monitoring using dispersive near‐infrared Raman spectroscopy that presents the advantage of non‐invasively being capable to make real time fast measurements. The degree of conversion of an odontological resin composite (A3, Z100^®, 3 M), photopolymerized by an LED (450 nm, 230 mW), was measured as an application of the technique. The Raman system consisted of a 785 nm Ti:Sapphire laser, a Chromex spectrograph with an entrance slit of 200 µm, and a liquid nitrogen cooled CCD detector. The system allowed acquisition of Raman spectra at times as short as 6 s. The progress of the photopolymerization was followed by obtaining Raman spectra every 6 s during 84 s. The intensity of the 1640 cm^?1 Raman peak, attributed to the aliphatic carbon double bonds, was chosen to calculate the conversion degree of the resin photopolymerization. Results showed that the degree of conversion presented an exponential growth, reaching a maximum of 50% after 60 s. Findings seem to confirm the trustworthiness of the system.     

Effect on Particle Size to Emitted X-Ray Intensity in Pellet Cement Sample Analyzed with WDXRF Spectrometer

Abstract

The particle size and heterogeneity effects on the analyte line were investigated for the analysis of powdered samples by X-ray fluorescence technique. In the analysis of samples utilizing the powder method, these effects caused serious errors with variations in particle size for the emitted intensity. The fluorescence intensities of some elements in pellet samples of cement (the range of particle sizes, < 32 µm, 32–38 µm, 38–45 µm, 45–63 µm, 45–75 µm, 75–106 µm, and 106–150 µm and, at press pressure 3.50 and 1.41 × 10⁷ kg/m²), are measured using a wavelength dispersive X-ray fluorescence (WDXRF) spectrometer for 14 pellets prepared according to the powder method. The results show that the K _α X-ray fluorescence intensities from samples can effect about 17% maximum differences in normalized intensities within selected particle sizes. These experimental results were interpreted by comparing with the other experimental results in the literature.