Photocatalytic Properties: Effect of Size, Shape and Surface Structures of Fine Particles

Scanning electron microscopy (SEM) provides three dimensional details of external surface structures and supplements ultrastructural information provided by transmission electron microscopy (TEM). Animals composed of watery jellylike tissues such as hydras and other coelenterates have not been considered suitable for SEM studies because of the difficulty in preserving such organisms in a normal state. This study demonstrates 1) the successful use of SEM on such tissue, and 2) the unique arrangement of batteries of nematocysts within large epitheliomuscular cells on tentacles of Hydra littoralis.Whole specimens of Hydra were prepared for SEM (Figs. 1 and 2) by the fix, freeze-dry, coat technique of Small and Màrszalek. The specimens were fixed in osmium tetroxide and mercuric chloride, freeze-dried in vacuo on a prechilled 1 Kg brass block, and coated with gold-palladium. Tissues for TEM (Figs. 3 and 4) were fixed in glutaraldehyde followed by osmium tetroxide. Scanning micrographs were taken on a Cambridge Stereoscan Mark II A microscope at 10 KV and transmission micrographs were taken on an RCA EMU 3G microscope (Fig. 3) or on a Hitachi HU 11B microscope (Fig. 4).

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Electron Microscopic Observation of Biological Specimens in Their Native State by Employing Cryogenic Techniques

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100095315 ◽

1972 ◽

Vol 30 ◽

pp. 410-411 ◽

Cited By ~ 1

Author(s):

Tokio Nei ◽

Haruo Yotsumoto ◽

Yoichi Hasegawa ◽

Yuji Nagasawa

Keyword(s):

Electron Microscopic Observation ◽

Surface Structures ◽

Specimen Preparation ◽

Native State ◽

Electron Microscopic ◽

Biological Specimen ◽

Specimen Holder ◽

Cold Stage ◽

Preparation Techniques ◽

Scanning Electron

In order to observe biological specimens in their native state, that is, still containing their water content, various methods of specimen preparation have been used, the principal two of which are the chamber method and the freeze method.Using its recently developed cold stage for installation in the pre-evacuation chamber of a scanning electron microscope, we have succeeded in directly observing a biological specimen in its frozen state without the need for such conventional specimen preparation techniques as drying and metallic vacuum evaporation. (Echlin, too, has reported on the observation of surface structures using the same freeze method.)In the experiment referred to herein, a small sliced specimen was place in the specimen holder. After it was rapidly frozen by freon cooled with liquid nitrogen, it was inserted into the cold stage of the specimen chamber.

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Cytoplasmic Organization in the Receptor Cells of the Crista Ampullaris

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100093559 ◽

1972 ◽

Vol 30 ◽

pp. 60-61 ◽

Cited By ~ 1

Author(s):

Robert F. Dunn

Keyword(s):

Fine Particles ◽

Apical Cell ◽

Apical Region ◽

Receptor Cells ◽

Cuticular Plate ◽

Morphological Organization ◽

Crista Ampullaris ◽

Cytoplasmic Organization ◽

High Degree ◽

General Appearance

Receptor cells of the cristae in the vestibular labyrinth of the bullfrog, Rana catesbiana, show a high degree of morphological organization. Four specialized regions may be distinguished: the apical region, the supranuclear region, the paranuclear region, and the basilar region.The apical region includes a single kinocilium, approximately 40 stereocilia, and many small microvilli all projecting from the apical cell surface into the lumen of the ampulla. A cuticular plate, located at the base of the stereocilia, contains filamentous attachments of the stereocilia, and has the general appearance of a homogeneous aggregation of fine particles (Fig. 1). An accumulation of mitochondria is located within the cytoplasm basal to the cuticular plate.

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Imaging molecules adsorbed onto electrodes under potential control by scanning probe microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100086180 ◽

1991 ◽

Vol 49 ◽

pp. 376-377 ◽

Cited By ~ 1

Author(s):

N.J. Tao ◽

J.A. DeRose ◽

P.I. Oden ◽

S.M. Lindsay

Keyword(s):

Surface Charge ◽

Environmental Effects ◽

Scanning Probe Microscopy ◽

Statistical Significance ◽

Electrochemical Methods ◽

Surface Structures ◽

Scanning Probe ◽

Potential Control ◽

Afm Imaging ◽

Special Circumstances

Clemmer and Beebe have pointed out that surface structures on graphite substrates can be misinterpreted as biopolymer images in STM experiments. We have been using electrochemical methods to react DNA fragments onto gold electrodes for STM and AFM imaging. The adsorbates produced in this way are only homogeneous in special circumstances. Searching an inhomogeneous substrate for ‘desired’ images limits the value of the data. Here, we report on a reversible method for imaging adsorbates. The molecules can be lifted onto and off the substrate during imaging. This leaves no doubt about the validity or statistical significance of the images. Furthermore, environmental effects (such as changes in electrolyte or surface charge) can be investigated easily.

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Bright-Field Images (Ctem) of Phase Objects at High Resolution

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100092414 ◽

1976 ◽

Vol 34 ◽

pp. 490-491 ◽

Cited By ~ 1

Author(s):

Sumio Iijima

Keyword(s):

High Resolution ◽

Electron Beam Irradiation ◽

Fine Particles ◽

High Resolution Electron Microscopy ◽

Good Test ◽

Resolution Electron ◽

Single Crystal Films ◽

Crystal Films ◽

By Products ◽

Test Objects

We have developed a technique to prepare thin single crystal films of graphite for use as supporting films for high resolution electron microscopy. As we showed elsewhere (1), these films are completely noiseless and therefore can be used in the observation of phase objects by CTEM, such as single atoms or molecules as a means for overcoming the difficulties because of the background noise which appears with amorphous carbon supporting films, even though they are prepared so as to be less than 20Å thick. Since the graphite films are thinned by reaction with WO3 crystals under electron beam irradiation in the microscope, some small crystallites of WC or WC2 are inevitably left on the films as by-products. These particles are usually found to be over 10-20Å diameter but very fine particles are also formed on the film and these can serve as good test objects for studying the image formation of phase objects.

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Ultrathin Platinum Crystal Surface Structures

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100118849 ◽

1985 ◽

Vol 43 ◽

pp. 394-395

Author(s):

R. L. Hines

Keyword(s):

Crystal Surface ◽

Surface Structures ◽

Platinum Surface ◽

Platinum Surfaces ◽

Resolution Level ◽

Experimental Facilities ◽

Carbon Backing ◽

Mesh Grid ◽

Atom Layer

The importance of atom layer terraces or steps on platinum surfaces used for catalysis as discussed by Somorjai justifies an extensive investigation of the structure of platinum surfaces through electron microscopy at the atomic resolution level. Experimental and theoretical difficulties complicate the quantitative determination of platinum surface structures but qualitative observation of surface structures on platinum crystals is now possible with good experimental facilities.Ultrathin platinum crystals with nominal 111 orientation are prepared using the procedure reported by Hines without the application of a carbon backing layer. Platinum films with thicknesses of about ten atom layers are strong enough so that they can be mounted on grids to provide ultrathin platinum crystals for examination of surface structure. Crystals as thin as possible are desired to minimize the theoretical difficulties in analyzing image contrast to determine structure. With the current preparation procedures the crystals frequently cover complete openings on a 400 mesh grid.

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