Imaging Of Surface Structures Research Articles

Quality assessment of biomass residues from sugar cane, cassava and the efficacy of pretreatment technique to converse into bioethanol

The aim of this research was to assess the quality of four agricultural waste biomass from sugar cane and cassava in Vietnam, the effect of pretreatment technique and the effect of cellulase enzyme in hydrolysis process to transform them into bioethanol. The agriculture biomass residues samples were collected, analysed, treated physically with popping technology. The treated samples then hydrolised using cellulase enzyme then fermented to produce ethanol. Surface structure of samples before and after the pretreatment were obtained by scanning electron microscopy. The result indicated that agricultural waste biomass from sugarcane and cassava pulp possessed component were highly favorable for bioethanol production. In contrast, the component from cassava sterm was not favorable for bioethanol production. Images of surface structures shot in 500 μm, 100 μm, 50 μm and 10 μm resolution of lignocellulose materials showed obviouly change of surface structure after popping pretreatment.

Local crystallography analysis for atomically resolved scanning tunneling microscopy images

Scanning probe microscopy has emerged as a powerful and flexible tool for atomically resolved imaging of surface structures. However, due to the amount of information extracted, in many cases the interpretation of such data is limited to being qualitative and semi-quantitative in nature. At the same time, much can be learned from local atom parameters, such as distances and angles, that can be analyzed and interpreted as variations of local chemical bonding, or order parameter fields. Here, we demonstrate an iterative algorithm for indexing and determining atomic positions that allows the analysis of inhomogeneous surfaces. This approach is further illustrated by local crystallographic analysis of several real surfaces, including highly ordered pyrolytic graphite and an Fe-based superconductor FeTe0.55Se0.45. This study provides a new pathway to extract and quantify local properties for scanning probe microscopy images.

Physical and Chemical Studies of Bacterial Bioaerosols at Wastewater Treatment Plant Using Scanning Electron Mikroscopy and X-Ray Photoelectron Spectroscopy

The paper presents the research results of the airborne bacteria collected at the wastewater treatment plants working with activated sludge system. Samples were taken by a six-stage Andersen Impactor placed near the aeration chambers. Bacteria cought at Petri plates were incubated at room temperature for 4 days, then analyzed in a macroscopic and microscopic way. This initial investigation was aimed at morphological characteristics of colonies and breeding characteristics of particular strains to giver general overwiev. Bacteria were identified on the basis of their metabolic properties using API biochemical tests. The essential studies were carried out using JOEL scanning electron microscope (FE-SEM model with field gun 7600[F]), equipped with "Cryo-SEM”, which gives the possibility of testing delicate biological samples in a frozen state. Its high resolving power and large depth of field allows to obtain images of surface structure of microorganisms in a magnification range from 1 000x to 70 000x. Bacteria samples were analyzed also in a fructured state what revealed internal structes and the thickness of cell walls which was in the range of 0,080-0,180 [μm]. Moreover, elemental composition of the surface layer of bacterial was also examined using photoelectron spectroscopy (XPS). Dominant elements were carbon, oxygen and nitrogen. Analysis of main line (C1s, O1s, N1s) allowed the identification of chemical composition of studied bioaerosols. Investigation found that the main compounds were polymers such as peptides and polysaccharides, as well hydrocarbon like compounds.

Scanning Electron Microscopy (SEM) of Plant Tissues

INTRODUCTIONScanning electron microscopy (SEM) is used to produce detailed images of surface structures. This article details the steps required to prepare a sample for SEM. In brief, the sample is fixed, dehydrated, subjected to critical-point drying, mounted, and coated with an electrically conducting material such as gold or palladium.

The generation of images of surface structures by laser-accelerated protons

Ion acceleration by lasers is one of the most important innovations in laser-plasma research in recent years. A mechanism that has gained great attention due to the remarkable properties of the accelerated beam is laser acceleration of protons from the rear surface of solid targets. A striking prediction is that these protons are capable of generating images of micro-structures present on this surface. These images might be useful to measure properties of the accelerated beam. In this article, we address the physics of the generation of images of surface structures imprinted into the target back surface with laser-accelerated protons.

Initial stages of cobalt film growth on MgO(001) surface

The initial stages of cobalt film growth on a MgO(001) surface was studied by methods of sample surface structure imaging by reflected electrons, low-energy electron diffraction, and Auger electron spectroscopy. The measurements were performed at room temperature for cobalt layer thicknesses up to 40 A. It is established that cobalt film growth proceeds according to the island mechanism. In the interval of cobalt film thicknesses below ∼ 10 A, the dominating surface phase has the form of cobalt islands with an fcc structure; at greater layer thicknesses, the surface film consists predominantly of cobalt grains with an hcp structure.

The generation of micro-fiducials in laser-accelerated proton flows, their imaging property of surface structures and application for the characterization of the flow

A mechanism that has gained great attention in the field of laser-ion acceleration due to remarkable properties of the accelerated beam is laser acceleration of protons from the rear surface of solid targets. It is shown that these protons are capable of transporting structure information from the rear surface of the target into the detector, which can be used to measure essential properties of the flow like an upper limit of the lateral beam emittance and the source area of the laser accelerated protons for a particular energy. In this Letter the essential mechanism responsible for the generation of images of surface structures by laser-accelerated protons is addressed and used to explain the experiment is described in the Letter.

Examination of Dentin Surface Using AFM (Our Experience)

Atomic force microscopy (AFM) as one the technique of Scanning Probe Microscopy is useful for imaging of surface structure. This method can yield three-dimensional high-resolution topographic images of sample surfaces by using a scanning technique for conductors and insulators on atomic scale. It is based upon mapping of atomic-forces on a surface of an investigated sample. The method is useful not only in physics and chemistry; it can be also applied in biological fields. Special construction of AFM scanner enables to follow biological samples in liquid environments. Artifacts caused by dehydration of samples are removed this way. Dentin of human teeth is a vital hydrated tissue. It is strongly sensitive to dehydration and drying that are commonly used in preparation of samples in examinations by Scanning Electron Microscopy (SEM). We describe our experience in examination of dentin surfaces of extracted human third molars using contact method of AFM under moist conditions.

Electrochemical Polymerization of Aniline Monomers Infiltrated into Well-Ordered Truncated Eggshell Structures of Polyelectrolyte Multilayers

The use of nanosphere lithography to construct two-dimensional arrays of polystyrene (PS) particles coated with multilayered polyelectrolyte (PE) shells and truncated eggshell structures composed of PE thin layers is reported. The truncated eggshell PE structures were produced by extraction of the PS particle cores with toluene. The core-extraction process ruptures the apex of the PE coating and causes a slight expansion of the PE thin layers. Aniline hydrochloride was infiltrated into the PE shells and subsequently electropolymerized to yield an array of a composite containing polyaniline (PAni) and PE thin shells. Voltammetric, quartz crystal microbalance, and reflectance Fourier transform infrared spectroscopic measurements indicate that aniline monomers were confined within the thin PE shells and the electropolymerization occurred in the interior of the PE shell. The PE thickness governs the amount of infiltrated monomer and the ultimate loading of the PAni in the truncated eggshell structure. Surface-structure imaging by atomic force microscopy and scanning electron microscopy, carried out after each step of the fabrication process, shows the influence of the PE thickness on the organization and dimensions of the arrays. Thus, the PE thin shells composed of different layers can function as nanometer-sized vessels for the entrapment of charged species for further construction of composite materials and surface modifications. This approach affords a new avenue for the synthesis of new materials that combine the unique properties of conductive polymers and the controllability of template-directed surface reactions.

Is seeing believing?: Atomic-scale imaging of surface structures using scanning tunnelling microscopy

Scanning tunnelling microscopy produces beautiful atomic resolution images of surfaces which appear to show atomic positions in a very direct fashion. However, the technique is intrinsically a probe of spatial variations in electronic structure, so interpreting such images correctly is sometimes far from trivial. A brief survey is presented of some of the known effects and their physical origins, and of the progress being made in theoretical modelling which has helped to understand many of these phenomena and to provide far more reliable image interpretation.

True atomic resolution imaging of surface structure and surface charge on the GaAs(110)

We demonstrated a novel method to detect the van der Waals and the electrostatic force interactions simultaneously on an atomic scale, which is based on frequency modulation detection method. For the first time, the surface structure and the surface charge at atomic-scale point defects on the GaAs(110) surface have been simultaneously resolved with true atomic resolution under ultra-high vacuum condition. From the bias voltage dependence of the image contrast, we can verify that the sign of the atomically resolved surface charge at the point defect was positive.

APPLICATIONS OF STEM INSTRUMENTS FOR SURFACE STUDIES

Scanning transmission electron microscopy (STEM) instruments have some particular advantages as compared with the more common transmission electron microscopes for some applications to surface research. Imaging of surfaces and mapping of the elemental distributions on surfaces with spatial resolutions approaching 1 nm are possible in an ultrahigh-vacuum STEM instrument when the low-energy secondary electrons or the Auger-emitted electrons are collected with high efficiency. In the imaging of surface layers on thin-film substrates, viewed in transmission, the use of a thin annular detector in STEM may greatly enhance the contrast, as illustrated by the case of the imaging of very thin nanocrystalline carbon layers on much thicker amorphous SiO2 films. The scanning reflection mode in a STEM instrument can provide some useful forms of contrast in images of surface structure. Standing wave fields can be formed on the surfaces of crystals with electrons, as with X-rays, one advantage of the electron case being that the standing wave fields may be imaged. Two new forms of electron holography, involving a STEM instrument and suitable for the study of surface structure, are proposed.

A new focusing ultrasonic transducer and two foci acoustic lens for acoustic microscopy

The textured piezoelectric film of a new organic-based material produced by vapor deposition was used as an active element of a focusing ultrasonic transducer. The transducer exhibits near theoretical lateral and axial resolution, unipolar pulse response to a step voltage, and 30 dB insertion losses in an octave frequency band. The transducer is acoustically transparent over a wide frequency range and can be fabricated on a concave spherical surface of the standard acoustic lens. The resulting double transducer and two foci acoustic lens are capable of improving the quality of the surface structure imaging or of being used in continuous wave reflection acoustic microscopy.

IMAGING SURFACE STRUCTURES BY DIRECT PHASING

We report success in applying direct phasing methods to produce images of surface structures at the atomic scale from intensity data collected using transmission electron diffraction.

Surface-oxidized carbon fibers: I. Surface structure and chemistry

The surface structure and chemistry of various surface oxidized HT carbon fibers, an IM and a HM carbon fiber were studied by SEM, STM, CAM (contact angle measurement), XPS and TPD with special reference to adsorbed oxidation products and adsorbed water. It is shown that a real image of surface structure and surface chemistry is only obtained after removal of adsorbed oxidation products by extraction with water and careful drying of the fibers without changing the surface chemistry. A comparison on the usefulness of the various surface analytical methods will be given in Parts II–IV of this paper.

Surface fractal dimension of graphitized carbon black particles

Fractal analysis of adsorption isotherms is used to study the surface roughness of carbon blacks graphitized at 3000 K. Gases of various molecular sizes (nitrogen, argon, ethane, propane, and butane) are adsorbed on different grades of carbon black. Using the molecular yardstick method, it is found that the surface fractal dimension of graphitized carbon black is 2.0 ± 0.1 and is independent of carbon black grade. Another approach, the FHH method, was also used. But the slopes of the FHH plots are sensitive to the forces responsible for adsorption and thus they cannot give the fractal dimension of carbon blacks. Direct imaging of surface structure of carbon black particles carried out using atomic force microscopy (AFM) confirmed that the surface of graphitized carbon black particles exhibits a low degree of irregularity on the atomic scale.

Combining atomic imaging, growth, and surface spectroscopy

UHV transmission electron microscopy brings several advantages to the study of surfaces including direct imaging of surface structures and surface defects with contrast based on atomic scattering and the ability to obtain information from subsurface layers. Over the last several months our research group has implemented several image and diffraction analysis techniques to enhance these advantages and help determine four noble metal induced silicon surface structures. Perhaps the most significant of these techniques are Wiener and Parametric Wiener image filtering to improve signal to noise levels in off axis HREM images of surface structures, two examples of which are shown in Figs. 1 and 2. Figure 1 is a Parametric Wiener filtered, near Schertzer, off-zone HREM image of Si(lll)-(5×2) Au which clearly shows the rows of gold and also contains some information on the silicon structure between the gold rows. With data from images and χ2 diffraction analysis we have found this structure is basically a Si surface dislocation decorated by two rows of gold atoms.

The Natural Subcellular Surface Structure of the Bovine Sperm Cell

We used atomic force microscopy (AFM), which utilizes a novel 3D image-contrast mechanism, to obtain nanometer-resolved, topographic data images of the natural surface structures of untreated bovine sperm cells. Freshly ejaculated, thawed, sonicated, and demembranated bovine sperm were adsorbed passively or by motility from suspension onto a coverglass substrate and directly imaged in normal air and saline environments without damaging the cells. Our AFM images of the surface structures of unfixed sperm imaged in normal air were consistent with previous electron microscope results on frozen or fixed sperm, demonstrating that the accurate preservation of small cellular structures is achievable using greatly simplified AFM sample preparation and imaging environments. Our AFM results also indicate that imaging sperm in physiologic buffer provides more native views of sperm due to the retention of cytoplasmic structures easily disrupted by drying forces. In addition, the AFM images show that numerous nanometersized subcellular structures of the sperm head and tail regions could be clearly visualized on rapidly prepared, unfixed, intact cells. Consequently, AFM should be considered a new tool for studying sperm structure abnormalities and monitoring the specific effects of, or damage caused by, various chemical reactants or other treatments on the structures of metabolically active or partially demembranated sperm. AFM is now emerging as an important new structural technique for imaging hydrated cells and organelles and, in addition, has the capabilities to physically "interrogate" them with the local probe.

Surface structure imaging, electronically induced modifications and electroluminescence of porous silicon by scanning tunneling microscopy

By means of scanning tunneling microscopy (STM) we have examined the surface morphology of photoluminescent porous silicon (PS) layers and we demonstrate the feasibility of modifying these films on a nanometer scale. For surface imaging, very thin porous coatings (∽ 20 nm in thickness) were used to allow a sufficient current flow through the material. The samples were prepared by anodic etching at low current densities (0.3-3 mA/cm 2), followed by a post-chemical treatment to yield appreciable photoluminescence in the visible range. The diameter of the detected surface features is typically well below 5 nm, in accordance with the quantum confinement approach for describing the luminescent properties in this material. By increasing the tunnel voltage and current beyond imaging conditions, electronic modifications of the PS films could be induced, which were subsequently detected with the same instrument. Operating the STM in the point-contact regime, local regions of PS layers 5–75 μm thick could be excited entailing an electroluminescence signal.

Surface characterization of fluorinated polyimide films grown by vapor deposition polymerization

Vapor deposition polymerization (VDP) was used to prepare fluorinated polyimide films. The process utilizes the coevaporation of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (TFDB) monomers. We characterized the surface by x-ray photoelectron spectroscopy (XPS), scanning electron microscopy, atomic force microscopy (AFM), and scanning tunneling microscopy (STM). The XPS analysis showed that the film stoichiometry greatly depended on the ratio of source effusion rates, and that a 6FDA/TFDB pressure ratio of 1:10 was best for obtaining stoichiometric 6FDA/TFDB polyimide. The surface structure image obtained by AFM was clearly different from that of spin-cast films. The surface morphology of the VDP films was characterized by an accumulation of parallel rod shaped structures, whereas that of the spin-cast one was a rough structure. The surface morphology of the VDP grown films at the initial growth state was also found to be a vertical stripe structure according to STM results.