Emission Type Scanning Electron Microscope Research Articles

Silver Nanoscale Hexagonal Column Chips for Detecting Cell-free DNA and Circulating Nucleosomes in Cancer Patients.

Blood tests, which are commonly used for cancer screening, generally have low sensitivity. Here, we developed a novel rapid and simple method to generate silver nanoscale hexagonal columns (NHCs) for use in surface-enhanced Raman scattering (SERS). We reported that the intensity of SERS spectra of clinical serum samples obtained from gastrointestinal cancer patients is was significantly higher than that of SERS spectra of clinical serum samples obtained from non-cancer patients. We estimated the combined constituents on silver NHCs by using a field emission-type scanning electron microscope, Raman microscopes, and a 3D laser scanning confocal microscope. We obtained the Raman scattering spectra of samples of physically fractured cells and clinical serum. No spectra were obtained for chemically lysed cultured cells and DNA, RNA, and protein extracted from cultured cells. We believe that our method, which uses SERS with silver NHCs to detect circulating nucleosomes bound by methylated cell-free DNA, may be successfully implemented in blood tests for cancer screening.

Study of corrosion protection of mild steel by eco-friendly silane sol–gel coating

The effects of dipping duration in the silane solution and the sol pH on the protective performance of an eco-friendly silane sol–gel coating consisting a mixture of tetraethoxysilane, methyltriethoxysilane and glycidyloxypropyltrimethoxysilane applied on mild steel substrate were studied in this paper using electrochemical techniques and surface analysis. In consistency with the data obtained from electrochemical impedance spectroscopy and polarization curves, electrochemical current noise fluctuation analysis, appearance of the power spectral density plots and noise resistance indicated the most efficient sol pH and immersion time in the silane solution. In this regard, field emission type scanning electron microscopy images and water contact angle values revealed impact of the sol pH on the film structure. The enhancement in protective performance of the hybrid coating resulting from optimum immersion in the silane solution with appropriate pH was connected to the film homogeneity and higher cross linking and thickness as well. Moreover, a good trend correlation was observed between the noise resistance and low-frequency impedance modulus data.

Free Volume Study of Severely Plastic Deformed Pure Fe

There is a growing interest for investigation of free-volume type defects in SPD-processed ultrafine-grained materials. In the present work, excess free volume in pure Fe prepared by shaped rolling is studied by high-resolution differential dilatometer as well as Archimedes method. The results show the formation of excess volume with increasing deformation strain. The volume fraction of free volume detected by dilatometer is below the evaluation of Archimedes method maybe because of the existence of void in the deformed metal. Microstructural study by field emission type scanning electron microscope confirms the presence of voids.

Preparation and characterization of poly(vinyl alcohol)/organo-modified cloisite Na+ with chiral L-leucine amino acid/TiO2 nanocomposites

Poly(vinyl alcohol)/organo-clay/TiO2 nanocamposites films were prepared with 10 wt % of organo-nanoclay and various amount of TiO2 nanoparticles. Cloisite Na+ has been modified via cation exchange reaction using ammonium salt of natural L-leucine amino acid as a cationic surfactant. After that poly(vinyl alcohol)/organo-nanoclay/TiO2 nanocomposites were synthesized by dispersion of TiO2 on the surfaces of organo-nanoclay in poly(vinyl alcohol) matrix by using ultrasonic energy. Three nanocomposites with different loading of TiO2 were prepared and characterized by X-ray diffraction, fourier transform infrared spectroscopy, field emission type scanning electron microscope, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis and ultraviolet-visible transmission spectra. The results showed that the organo-nanoclay and TiO2 were dispersed homogeneously in poly(vinyl alcohol) matrix and also showed improvement in their thermal properties compared with the pure poly(vinyl alcohol).

Field emissions of graphene films deposited on different substrates by CVD system

Graphene films are deposited on copper (Cu) and aluminum (Al) substrates, respectively, by using a microwave plasma chemical vapour deposition technique. Furthermore, these graphene films are characterized by a field emission type scanning electron microscope (FE-SEM), Raman spectra, and field emission (FE) I–V measurements. It is found that the surface morphologies of the films deposited on Cu and Al substrates are different: the field emission property of graphene film deposited on the Cu substrate is better than that on the Al substrate, and the lowest turn-on field of 2.4 V/μm is obtained for graphene film deposited on the Cu substrate. The macroscopic areas of the graphene samples are all above 400 mm2.

In situ preparation of high performance polyimide nanocomposites based on functionalized multiwalled carbon nanotubes

Nanocomposites of high performance polyimide and modified multiwalled carbon nanotube were prepared via in situ polymerization technique. Neat fluorinated polyimide was synthesized from the reaction between 4,4′-(hexafluoroisopropylidene) diphthalic anhydride and 2-(3,5-diaminophenyl)-benzimidazole. Polyimide/modified carbon nanotube nanocomposites enclosing 0.5, 1, 3, and 5% of functionalized carbon nanotube were successfully prepared by an in situ polymerization reaction through thermal imidization. The Fourier transform infrared spectroscopy, X-ray diffraction, field emission type scanning electron microscope, transmission electron microscopy, and thermogravimetric analysis techniques were used to evaluate the properties of the novel nanocomposites. According to thermogravimetric analysis results, the addition of the modified multiwalled carbon nanotube improved thermal stability of the obtained hybrid materials. The morphological images show that the carbon nanotubes were dispersed homogeneously in polymer matrix. The mechanical properties of nanocomposites were substantially improved by the incorporation of functionalized carbon nanotube into the polymer matrix.

Preparation of Porous Silicon and Effect of Gettering on the Resistivity

The porous silicon layer was fabricated by electrochemical etching process using an aqueous HF-based electrolyte. The characterizations of porous silicon layer were investigated by Emission-type scanning electron microscope (SEM), Raman spectra and X-ray diffraction (XRD). With the current density increasing, the pore diameter and density become much bigger. This result also was confirmed by Raman spectra and XRD result of samples, which revealed the decreasing of grain size of silicon. The resistivity of crystalline silicon increased when the porous layer was removed after heat treatment at 850°C for 2.5h, which should be attributed to the gettering process of porous silicon.

Modification of Clay with L-Leucine and TiO2 with Silane Coupling Agent for Preparation of Poly(Vinyl Alcohol)/Organo-Nanoclay/Modified TiO2 Nanocomposites Film

Poly(vinyl alcohol)/organo-nanoclay/modified-TiO2 nanocomposites films were fabricated by dispersion of modified TiO2 on the surface of organo-nanoclay in a poly(vinyl alcohol) matrix via an ultrasonic process followed by solution film casting. For this purpose surface-modified TiO2 nano-particles were added into the poly(vinyl alcohol)/organo-modified Cloisite Na + nanocomposites matrix with 10 wt% organonanoclay. For the improvement of nanoparticles dispersion and increasing possible interactions between nano-particles and polymeric matrix, the surface of the nano-TiO2 was modified with silane coupling agent (KH550). Also, the negative charge on the silica layer can play an important role in dispersing nanosized TiO2. Three nanocomposites with different loading of modified-TiO2 (1, 3 and 6 wt%) were prepared and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, field emission type scanning electron microscope, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis and UV-Vis transmission spectra. In morphological images it was observed that the OMMT was dispersed homogeneously in PVA matrix and modified TiO2 nanoparticles are regularly dispersed on whole surface of organo-nanoclay layers. TGA results show that thermal stability of poly(vinyl alcohol)/organoclay/modified TiO2 nanocomposites are enhanced compared with neat PVA.

Effect of Inorganic Nanomater ials on the Morphology and Thermal Proper ties of PVA Nanocomposite Nanowebs

Poly(vinyl alcohol) (PVA), PVA/Montmorillonite (MMT), PVA/Silver (Ag), and PVA/MMT/Ag nanocomposite nanowebs were prepared by electrospinning technique in aqueous solution. In order to investigate the effect of inorganic materials on the morphology and thermal properties of PVA based nanocomposite nanowebs, experiments were performed with 5 wt.% of MMT and Ag. Field emission type scanning electron microscopy, transmission electron microscopy (TEM), reflection type X-ray diffraction (XRD), and thermal gravimetric analyzer were utilized to characterize nanocomposite nanowebs. TEM and XRD results show MMT and Ag were well dispersed in PVA nanowebs. Those inorganic nanoparticles enhanced thermal property of the nanocomposite nanowebs.

Effect of HF Concentration on Physical and Electronic Properties of Electrochemically Formed Nanoporous Silicon

The most common fabrication technique of porous silicon (PS) is electrochemical etching of a crystalline silicon wafer in a hydrofluoric (HF) acid‐based solution. The electrochemical process allows for precise control of the properties of PS such as thickness of the porous layer, porosity, and average pore diameter. The effect of HF concentration in the used electrolyte on physical and electronic properties of PS was studied by visual color observation, measuring nitrogen sorption isotherm, field emission type scanning electron microscopy, Raman spectroscopy, and photoluminescence spectroscopy. It was found that with decrease in HF concentration, the pore diameter increased. The PS sample with large pore diameter, that is, smaller nanocrystalline size of Si between the pores, was found to lead to a pronounced photoluminescence peak. The systematic rise of photoluminescence peak with increase of pore diameter and porosity of PS was attributed to quantum confinement. The changes in nanocrystalline porous silicon were also clearly observed by an asymmetric broadening and shift of the optical silicon phonons in Raman spectra. The change in electronic properties of PS with pore diameter suggests possibilities of use of PS material as a template for fundamental physics as well as an optical material for technological applications.

Preparation of SrTiO 3-supported TiO 2 photocatalyst

Strontium titanate (SrTiO 3) nano particles were supported on titania (TiO 2) particles P25, which is commercially available photocatalysts with a high activity, by reacting with strontium hydroxide aqueous solution under hydrothermal condition at 70 °C. SrTiO 3-supported TiO 2 powders were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), field emission type scanning electron microscopy (FE-SEM), and energy dispersive spectrometer (EDS). The photocatalytic activity of SrTiO 3-supported TiO 2 was examined by decolorisation of methylene blue (MB) under UV irradiation in the photocatalyst-dispersed solution. Enhancement on the photocatalytic activity of TiO 2 by supporting of SrTiO 3 was confirmed.

Field emission characteristics of nano-structured carbon films deposited on differently pretreated Mo films

Nano-structured carbon films (NCFs) were grown on Mo layers by microwave plasma chemical vapor deposition (MPCVD) system. The Mo layers were deposited on ceramic substrates by electron beam deposition method and were pretreated by different techniques, which include ultrasonically scratching and laser-grooving technology (10 line/mm). NCFs were characterized by a field emission type scanning electron microscope (FE-SEM), Raman spectra and field emission (FE) I– V measurements. Effects of process parameters on morphologies, structures and FE properties of NCFs were examined. The experimental results show that two kinds of NCFs deposited at the same parameters employed for the MPCVD process were respectively composed of carbon nano-balls and reticular carbon nano-tubes inlayed by carbon nano-balls with dissimilar disorder structures, both NCFs showed each merits and exhibited good field emission properties, especially shown in the uniformity of FE, the uniform field emission images with areas of 4 cm 2 were obtained. Growth mechanism influenced by different pretreated method was discussed and the possible FE mechanisms of the NCFs were also investigated. Finally, the process characteristics of laser-grooving technology were analyzed, and its potential applications were predicted.

Effect of Thermal Oxidation Treatment on Surface Characteristic and Corrosion Resistance of Ni-Ti Shape Memory Alloy

In this study, a mechanically polished Ni-Ti alloy was subjected to isothermal oxidation (TO) in N2-20vol.%O2 at temperatures ranging from 300 to 800°C. TO-treated surfaces were then characterized by field emission type scanning electron microscopy (FE-SEM), energy dispersive X-ray spectrometer (EDX), X-ray electron spectroscopy (XPS) and X-ray diffraction (XRD). Electrochemical corrosion tests were also carried out using a three electrochemical cell connected to a computer driven potentiostat. Results showed that Ni-Ti alloy exhibited different oxidation behavior depending on the treatment temperatures. A Ni free layer was observed in the oxide layer for the specimens TO-treated at temperatures 500°C and above. Specimens TO-treated at temperatures ranging from 300 to 500°C showed higher corrosion resistance compared to that of the surface finished by polishing. This was because the TO-treatment created a thick oxide layer with an amorphous structure. Specimens TO-treated at above 600°C showed very low passive current densities, but lower pitting potential. This was because these samples were covered with crystalline oxide. Consequently, the TO-treatment at 500°C produced a smooth protective nickel free oxide layer, which contributes to good biocompatibility of Ni-Ti implants.

Structural Control of Micro-Pore Surface and Trihalomethanes Adsorption Ability of Phenol Activated Carbon

The purpose of this study was to improve the adsorption ability of activated carbon for removal of trihalomethanes (THMs) to design a small and efficient water purifier. The phenol activated carbon with the high adsorption ability to THMs was used in the experiment. To improve the adsorption ability of the activated carbon, the effect of heat treatment temperature under the nitrogen atmosphere was investigated. The effect of the heat treatment temperature was evaluated from the chloroform adsorption isotherm, and the amount of purified water containing THMs. First of all, phenol resin was carbonized at 600°C for 3 h, and was activated by steaming at 900°C. Activation time was 0.5, 1.0, and 2.5 h. Next, the heat treatment was carried out for the sample of 1.0 h activation with the highest adsorption ability. The heat treatment temperature was 450, 600, 750, and 900°C. The heat treatment time was fixed at 3 h for all samples. As a result, it was found that the adsorption ability of the phenol activated carbon to THMs raised by about 1.6 times with the heat treatment at 750°C following the activation. On the other hand, the influence of the heat treatment on the structure of the phenol activated carbon was investigated. The structure was analyzed with pore size distribution measurement, X-ray photoelectron spectroscopy (XPS), temperature programmed desorption mass spectrometry (TPD-MS), and field emission-type scanning electron microscope (FE-SEM). The elimination of functional groups were observed clearly with the heat treatment, which means increased hydrophobicity of pore surface in the phenol activated carbon. Moreover, enlargement of the pore entrance were confirmed. Therefore, we concluded that THMs were efficiently led into pores due to the enlarged pore entrance, and was adsorbed strongly due to the increased hydrophobicity.

Field Emission-Type Scanning Electron Microscope for Examination of Irradiated Fuels

A field emission-type scanning electron microscope (FE-SEM) for observation of irradiated fuels and materials was installed at the Reactor Fuel Examination Facility at the Japan Atomic Energy Research Institute. A cell with remote-handling systems only for the FE-SEM was made to enable safe manipulation of highly radioactive samples. Some parts of the FE-SEM were modified for the remote handling outside the cell. The energy dispersive spectrometer modified for the samples was also equipped on the FE-SEM to determine element compositions of the observed samples. After the modifications, characterization tests were carried out using deposited gold film and uranium rock samples that were unirradiated. In results of the tests, high-resolution images of those specimens were obtained with high magnification above 10 000. From those results, it was expected that the FE-SEM kept the high performance even after the modifications and would be utilized for radioactive samples.

Development of Observation Method for Tempered Martensite Microstructure Using Chemical Mechanical Polishing Technique

A new observation method was developed for visualizing microstructure on a chemical mechanically polished (CMP) surface for tempered martensite of JIS-SCM440, a medium-carbon steel. The CMP and an electropolished (EP) surfaces were observed using an atomic force microscope (AFM) and a field emission type-scanning electron microscope (FE-SEM), respectively. AFM images, FE-secondary and backscattered electron images and electron backscattered patterns (EBSP) were obtained for the CMP and EP surfaces. The AFM and FE-secondary electron images of the EP surface clearly visualized martensite blocks and cementite particles, since unevenness corresponding to blocks and cementite particles was created by electropolishing. On the other hand, the AFM images of the CMP surface revealed that the CMP process produced a very smooth surface with unevenness not exceeding 10 nm. The FE-backscattered electron images of the CMP surface only visualized the crystal misorientation of the martensite matrix microstructure, since the images are not influenced by surface unevenness. The CMP surface is more appropriate than the EP surface for EBSP measurements, since the CMP surface is smoother than that of the EP surface. Blocks with a high-angle boundary exceeding 15° could be recognized by EBSP mapping, but laths with a low-angle boundary below 3° could not.

Characterization of amorphous carbon film-coated nanotubes as electron field emission material

Effects of amorphous carbon (a-C) thin film coating over carbon nanotubes (CNTs) on the field emission characteristics have been studied. Large-area surface-wave plasma (SWP) device was used both for growth of multi-wall CNTs on Ni-evaporated Si substrate and for deposition of a-C thin layer over CNTs. Field emission characteristics of the a-C film-coated CNTs prepared with different CVD durations were investigated. Experimental results show that the emission performance was significantly improved by coating a-C film typically with a thickness of 0.6–1 μm, that is, the ignition voltage for electron emission was reduced from 240 V for the sample of CNTs only to 110 V for that of CNTs deposited with a-C film during 60 min. The surface morphology has been also studied using the field emission type scanning electron microscopy (FE-SEM). It was deduced that the reduction of ignition voltage was due to the field enhancement originated from grain shape structures of the surface after a-C film deposition.

Photoinduced formation and aggregation of silver nanoparticles at the surface of carboxymethylcellulose films

Formation and aggregation of photolytic silver nanoparticles at the surface of silver salt of carboxymethylcellulose films (CMCAg films) have been investigated. Detailed X-ray photoelectron spectroscopy (XPS) study and field emission type scanning electron microscopy (FE-SEM) observation have been carried out to characterize silver nanoparticles at the film surface. When the CMCAg films were irradiated with UV light in wet air at room temperature for 30–60 min, silver nanoparticles of ca. 10 nm size were formed at the irradiated surface. According to the FE-SEM observation, the growth of the particle diameter and aggregation of nanoparticles took place after prolonged irradiation, and finally, the irradiated side of the film surface was densely covered with the silver nanoparticles of ca. 35 nm size. Chemical composition analysis by the XPS measurements has confirmed the increase in the atomic concentration of silver with irradiation time. It is suggested that silver atoms and clusters can move in the film and precipitate at the irradiated surface.

Aggregation of Photolytic Gold Nanoparticles at the Surface of Chitosan Films

Formation and aggregation of photolytic gold nanoparticles at the surface of chitosan (CTO) films have been investigated. When thin films of chloroauric acid salt of CTO were irradiated with UV light in wet air at room temperature for 10 min, gold nanoparticles of approximately 10 nm size are formed at the film surface. Detailed X-ray photoelectron spectroscopy (XPS) study and field emission type scanning electron microscopy (FE-SEM) observation have been carried out to characterize gold nanoparticles at the film surface. The shift of Au(4f) peak to the higher energy side and broadening of full width at half-maximum in the XPS spectrum are the direct evidence of the existence of gold atoms and small clusters in the early stage of photolysis. According to FE-SEM observation, growth in the particle diameter and aggregation of nanoparticles were observed after prolonged irradiation, and, finally, the film surface was densely covered with gold particles of 20-100-nm size. Gold atoms and clusters could move in the film and precipitate to the irradiated surface. Chemical composition analysis further suggests that gold particles at the surface are covered with an ultrathin CTO layer, which is partly oxidized by oxygen and chlorinated by chlorine during photochemical reactions.

TOF-SIMS measurement for the complex particulate matter in urban air environment

We developed the measurement method for the complex particulate matter in urban air environment using micro-beam analyses [electron probe microanalysis (EPMA), field emission type scanning electron microscope (FE-SEM), and TOF-SIMS]. In this study, the environmental particles collected at the location near both the traffic route and the railroad were characterized. By the EPMA analysis and FE-SEM observation, it became clear that many iron particles adsorbed smaller environmental particles on surface. The most of adsorbed particles were the carbonaceous particles containing small amount of silicon, as observed from the results of TOF-SIMS measurement. From these results, we concluded that the complex particles such as the iron particles emitted from a railroad combined with diesel exhaust particles (DEPs) were suspended in the urban air environment.