scholarly journals Optical Features of Nanosize Iron and Molybdenum Sulfide Clusters

1994 ◽  
Vol 358 ◽  
Author(s):  
J. P. Wilcoxon ◽  
G. Samara ◽  
P. Newcomer
Keyword(s):  
Surface Characterization ◽  
Surface States ◽  
Molybdenum Sulfide ◽  
Narrow Bandgap ◽  
Sulfide Clusters ◽  
Optical Applications ◽  
Bandgap Semiconductors ◽  
Large Clusters ◽  
Small Clusters

ABSTRACTIn the bulk state FeS2 and MoS2 are optically opaque, narrow bandgap semiconductors with no optical applications. We demonstrate that nanosize FeS2 and MoS2 have bandgaps that can be adjusted to the visible and even UV region of the spectrum by control of the cluster size. This opens up a host of applications of these materials as inexpensive solar photocatalysts. We demonstrate that the band-gap of both materials shifts to the blue with decreasing size but ceases shifting when a size of ∼ 3 nm (in the case of MoS2) is attained. We interpret this observation as a change from bulk quantum confinement of the hole-electron pair of a tiny semiconductor to a set of discrete molecular-like transitions more characteristic of a large molecule. Room temperature photoemission studies of these clusters demonstrate that, while photoemission shifts to the blue with increasing bandgap for large clusters, small clusters have photoemission exclusively from trapped sub-bandgap surface states. Chemical modification of the surface to introduce hole or electron traps can result in either an enhancement or a decrease in the photoluminescence. In addition, we report our results concerning chemical purification and preliminary surface characterization of MoS2 clusters by chromatography.

scholarly journals Characterization of maturity and quality of Brazilian apirenic grapes in the São Francisco river Valley

2012 ◽  
Vol 32 (1) ◽  
pp. 26-33 ◽  
Author(s):  
Robson de Jesus Mascarenhas ◽  
Silvanda de Melo Silva ◽  
Maria Auxiliadora Coêlho de Lima ◽  
Rejane Maria Nunes Mendonça ◽  
Heinz Johann Holschuh
Keyword(s):  
Titratable Acidity ◽  
Soluble Solids ◽  
Minimum Diameter ◽  
Red Grapes ◽  
Berry Size ◽  
Large Clusters ◽  
Small Clusters ◽  
Light Green

The objective of this study was to characterize and correlate maturity and quality of the first varieties of Brazilian seedless grapes 'BRS Clara', 'BRS Linda', 'BRS Morena', and 'Advanced Selection 8' compared with the American variety 'Crimson Seedless' in compliance with the Brazilian Normative/2002 and export standards Advanced Selection 8' is dark reddish, has large clusters, and is a very large ellipsoid berry; 'BRS Morena' is black with medium sized clusters and large berry shaped as ellipsoid to globoid; 'BRS Linda' is light green and has large sized clusters; 'Crimson' is pink and has small clusters with berries varying from medium to large sizes and ellipsoid shaped; and 'BRS Clara' is green yellowish has medium sized clusters and small berry of elongated ellipsoid shape. All varieties evaluated meet the standard for domestic market established as berry size minimum diameter 12 mm. 'BRS Clara' does not meet the export requirements of diameter. Berries of the red grapes 'BRS Morena' and 'Crimson Seedless' are firmer. The pH, titratable acidity, and soluble solids meet the official standards. Larger clusters are less acidic and present higher soluble solids/titratable acidity ratios implying that they are the sweetest type when ripe.

Process and Surface Characterization of Hydrogen Plasma Cleaning of Si(100)

1990 ◽  
Vol 204 ◽  
Author(s):  
T. P. Schneider ◽  
J. Cho ◽  
J. Vander Weide ◽  
S.E. Wells ◽  
G. Lucovsky ◽  
...  
Keyword(s):  
Surface Characterization ◽  
Hydrogen Plasma ◽  
Surface States ◽  
Diagnostic Techniques ◽  
Gas Analysis ◽  
Plasma Cleaning ◽  
Low Energy Electron ◽  
Diffraction Patterns ◽  
Surface Diffraction

ABSTRACTThis study details low pressure and low temperature cleaning of Si(100) surfaces. The properties of Si surfaces exposed to variations in plasma generated H are described. The diagnostic techniques used to study the processing conditions are residual gas analysis (RGA) and emission spectroscopy. The surface is characterized by low energy electron diffraction (LEED) and angle resolved uv-photoemission spectroscopy (ARUPS). During the cleaning, Si complexes are formed which indicates the removal of species from the Si(100) surface. Plasma cleaning at 300°C results in a Si(100) surface with 2×1 surface diffraction patterns as detected by LEED. Measurements by ARUPS with He I radiation show the absence of Si surface states on the Hpassivated surface. The ARUPS measurements also indicate that the H begins to desorb from the Si(100) H-passivated surface at ∼500°C.

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

1973 ◽  
Vol 31 ◽  
pp. 132-133 ◽  
Author(s):  
R. E. Herfert
Keyword(s):  
Surface Characterization ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
Depth Of Penetration ◽  
X Ray ◽  
The Past ◽  
Transmission Electron ◽  
Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

Surface Characterization of Functionalized Imidazolium-Based Ionic Liquids

Langmuir ◽  
2008 ◽  
Vol 24 (17) ◽  
pp. 9500-9507 ◽  
Author(s):  
Claudia Kolbeck ◽  
Manuela Killian ◽  
Florian Maier ◽  
Natalia Paape ◽  
Peter Wasserscheid ◽  
...  
Keyword(s):  
Ionic Liquids ◽  
Surface Characterization

scholarly journals Characterization of Steel Slag Filler and Its Effect on Aging Resistance of Asphalt Mastic with Various Aging Methods

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 869
Author(s):  
Minghua Wei ◽  
Shaopeng Wu ◽  
Haiqin Xu ◽  
Hechuan Li ◽  
Chao Yang
Keyword(s):  
Particle Size ◽  
Surface Characterization ◽  
Steel Slag ◽  
Self Healing ◽  
Limestone Filler ◽  
Asphalt Mastic ◽  
Pore Characterization ◽  
Asphalt Mastics ◽  
Healing Property

Steel slag is the by-product of the steelmaking industry, the negative influences of which prompt more investigation into the recycling methods of steel slag. The purpose of this study is to characterize steel slag filler and study its feasibility of replacing limestone filler in asphalt concrete by evaluating the resistance of asphalt mastic under various aging methods. Firstly, steel slag filler, limestone filler, virgin asphalt, steel slag filler asphalt mastic and limestone filler asphalt mastic were prepared. Subsequently, particle size distribution, surface characterization and pore characterization of the fillers were evaluated. Finally, rheological property, self-healing property and chemical functional groups of the asphalt mastics with various aging methods were tested via dynamic shear rheometer and Fourier transform infrared spectrometer. The results show that there are similar particle size distributions, however, different surface characterization and pore characterization in the fillers. The analysis to asphalt mastics demonstrates how the addition of steel slag filler contributes to the resistance of asphalt mastic under the environment of acid and alkaline but is harmful under UV radiation especially. In addition, the pore structure in steel slag filler should be a potential explanation for the changing resistance of the asphalt mastics. In conclusion, steel slag filler is suggested to replace limestone filler under the environment of acid and alkaline, and environmental factor should be taken into consideration when steel slag filler is applied to replace natural fillers in asphalt mastic.

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