DETERMINATION OF THE WAX LAYER ULTRASTRUCTURE OF JONAGOLD WITH CONFOCAL AND RASTER ELECTRON MICROSCOPY

The independent channel method which is intended for the calculation of specific electrical conductivity of graphene-contained shungite is proposed and realized on practice. It is noted that the most important of shungite application is the creation of screen hawing large area which are able to block electromagnetic radiation in wide frequency range. The most important factor which determines the blocking properties of shungite is the specific electrical conductivity of its carbon part which is determined by the spatial distribution of carbon atoms. As a main method of carbon structure investigation is mentioned the high-resolution raster electron microscopy which allows from the surface of specimen to receive the card of distribution of graphene slides and graphene packets. The spatial factor which determines the shungite conductivity is large anisotropy of single graphene slide which reaches three orders and more in the cases along and across the slide. The proposed method independent channels takes into consideration the arbitrary orientation of graphene packets relatively to direction of current flow. As a basis of method is employing the card of carbon spatial distribution which is received by raster electron microscopy method. The card is divided by parallel channels which transverse dimension is near or slightly exceeds the typical dimension of graphene packet. The channels are divided to square blocks which sides are equal to width of channel. The whole resistance of channel is formed by the successive connection of individual resistances of blocks. The resistance of whole card is determined by parallel connection of channels or averaging of resistance of all channels and following filling the whole area of card. The first step of analysis is the determination of advantage orientation of slides inside of every blocks. On the basis of determined orientation the block is filled by periodic structure which period is equal to the width of graphene slide and neighbouring interval. As a parameter which determines the orientation is used the angle between advantage orientation of graphene slides and axis of current flow between contacts. Owing to symmetry of task in comparison of current direction the limited meanings of corner is 0 and 90 degree. It is established two principal different cases of orientation: first – when determining angle is less than 45 degree and second when this angle is more than 45 degree. In the first case the current flows along the stripe with large conductivity. In the second case the current flows across these stripes so as through the stripes with low conductivity. It is found the smooth dependence of block resistivity from the angle of strip orientation. For the characteristic of area which is filled graphene slides it is proposed the coefficient of filling which is determined by binary discretization method. On the basis of analysis of slides orientation and filling coefficients are calculated the resistance of individual blocks. The resistances of all channels of investigated card are proposed. By using two methods – parallel connection and averaging over all channels it is calculated the specific electrical resistance and specific electrical conductivity of material as a whole. It is found that the received values of specific conductivity exceed the determined in experiment value in several (to 10) times. For the coordination of calculated value with experimental value it is made the variation of specific resistances of graphene slides and intervals between its. It id found that the calculation by method of parallel connection of channels ensures several better coordination than method of averaging. It is shown that the resistance is improved in the first turn by the increasing the resistance of interval between slides. In the quality of possible reason of decisive role of interval it is proposed the observed in experiment sharp non-homogeneity of relative arrangement of graphene slides. It is discussed the possible courses of further development of work. As a most important task it is proposed the more circumstantial determination of statistical character of received results.

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Enhanced information from biological materials through technological improvements in cryo-electron microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100124343 ◽

1992 ◽

Vol 50 (1) ◽

pp. 788-789

Author(s):

Marc J.C. de Jong ◽

Wim M. Busing ◽

Max T. Otten

Keyword(s):

Electron Microscopy ◽

Electron Beam ◽

Biological Materials ◽

Electron Crystallography ◽

Cryo Electron Microscopy ◽

Transmission Electron ◽

The Many ◽

Technological Improvements ◽

Beam Damage

Biological materials damage rapidly in the electron beam, limiting the amount of information that can be obtained in the transmission electron microscope. The discovery that observation at cryo temperatures strongly reduces beam damage (in addition to making it unnecessaiy to use chemical fixatives, dehydration agents and stains, which introduce artefacts) has given an important step forward to preserving the ‘live’ situation and makes it possible to study the relation between function, chemical composition and morphology.Among the many cryo-applications, the most challenging is perhaps the determination of the atomic structure. Henderson and co-workers were able to determine the structure of the purple membrane by electron crystallography, providing an understanding of the membrane's working as a proton pump. As far as understood at present, the main stumbling block in achieving high resolution appears to be a random movement of atoms or molecules in the specimen within a fraction of a second after exposure to the electron beam, which destroys the highest-resolution detail sought.

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Ambient air. Determination of numerical concentration of inorganic fibrous particles. Scanning electron microscopy method

10.3403/02711247 ◽

2002 ◽

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Ambient Air ◽

Microscopy Method ◽

Scanning Electron Microscopy Method ◽

Electron Microscopy Method ◽

Scanning Electron ◽

Numerical Concentration

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Ambient air � Determination of numerical concentration of inorganic fibrous particles � Scanning electron microscopy method

10.3403/30375051 ◽

2019 ◽

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Ambient Air ◽

Microscopy Method ◽

Scanning Electron Microscopy Method ◽

Electron Microscopy Method ◽

Scanning Electron ◽

Numerical Concentration

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Determination of intermediate state structures in the opening pathway of SARS-CoV-2 spike using cryo-electron microscopy

Chemical Science ◽

10.1039/d1sc00244a ◽

2021 ◽

Author(s):

Z. Faidon Brotzakis ◽

Thomas Lohr ◽

Michele Vendruscolo

Keyword(s):

Infectious Disease ◽

Electron Microscopy ◽

Severe Acute Respiratory Syndrome ◽

Intermediate State ◽

Therapeutic Interventions ◽

Cryo Electron Microscopy ◽

Welfare Systems

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes COVID-19, a highly infectious disease that is severely affecting our society and welfare systems. In order to develop therapeutic interventions against this...

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A Magnetic Nanocomposite Modifier for Improved Ultrasensitive Detection of Hexavalent Chromium in Water Samples

Chemosensors ◽

10.3390/chemosensors9080189 ◽

2021 ◽

Vol 9 (8) ◽

pp. 189

Author(s):

Nuša Hojnik ◽

Olivija Plohl ◽

Matjaž Finšgar

Keyword(s):

Electron Microscopy ◽

Analytical Performance ◽

Magnetic Nanocomposite ◽

Ex Situ ◽

Trace Determination ◽

Silica Layer ◽

X Ray ◽

Square Wave ◽

Static Contact

In this work, different electrodes were employed for the determination of Cr(VI) by the cathodic square‑wave voltammetry (SWV) technique and the square-wave adsorptive stripping voltammetry (SWAdSV) technique in combination with diethylenetriaminepentaacetic acid. Using SWV, a comparison of the analytical performance of the bare glassy carbon electrode (GCE), ex situ electrodes (antimony-film—SbFE, copper-film—CuFE, and bismuth-film—BiFE), and the GCE modified with a new magnetic nanocomposite (MNC) material was performed. First, the MNC material was synthesized, i.e., MNPs@SiO2@Lys, where MNPs stands for magnetic maghemite nanoparticles, coated with a thin amorphous silica (SiO2) layer, which was additionally functionalized with derived lysine (Lys). The crystal structure of the prepared MNCs was confirmed by X-ray powder diffraction (XRD), while the morphology and nano-size of the MNCs were investigated by field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM), where TEM was additionally used to observe the MNP core and silica layer thickness. The presence of functional groups of the MNCs was investigated by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and surface analysis was performed by X-ray photoelectron spectroscopy (XPS). The hydrophilicity of the modified electrodes was also tested by static contact angle measurements. Then, MNPs@SiO2@Lys was applied onto the electrodes and used with the SWV and SWAdSV techniques. All electrodes tested with the SWV technique were effective for Cr(VI) trace determination. On the other hand, the SWAdSV technique was required for ultra-trace determination of Cr(VI). Using the SWAdSV technique, it was shown that a combination of ex situ BiFE with the deposited MNPs@SiO2@Lys resulted in excellent analytical performance (LOQ = 0.1 µg/L, a linear concentration range of 0.2–2.0 µg/L, significantly higher sensitivity compared to the SWV technique, an RSD representing reproducibility of 9.0%, and an average recovery of 98.5%). The applicability of the latter system was also demonstrated for the analysis of a real sample.

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