Incorporating Non-NIR Absorbing Agent into Packed Powder Samples in Diffuse Reflectance NIR Measurement to Improve Representation of Sample Composition and Accuracy of Concentration Determination

Abstract On the base of Schuster-Kubelka-Munk's theory, quantitative relations between the bulk absorp tion and diffuse reflectance spectra of undiluted and diluted semiconductor powder samples are established in the region of the long-wave tail of the absorption edge. Investigations in the long wave region of the diffuse reflectance spectra of V2O5, based on these relations, led to the result that in contradiction with earlier observations on single crystals7, 22, 27, allowed direct optical transitions between valence band and conduction band do not seem to be excluded. Quantitative optical activation energies are obtained from diffuse reflectance spectra.

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MONTMORILLONITE SURFACE AS A CATALYST FOR THE FORMATION OF SAT METAL TETRA (P-SULPHOPHENYL) PORPHYRINS

Jurnal Teknologi ◽

10.11113/jurnalteknologi.v82.14564 ◽

2020 ◽

Vol 82 (6) ◽

pp. 1-9

Author(s):

Jasim Hamadi Hassen ◽

Jack Silver

Keyword(s):

Metal Ion ◽

Diffuse Reflectance ◽

External Surface ◽

Water Soluble ◽

Sodium Ions ◽

X Ray Diffraction ◽

Visible Absorption ◽

X Ray ◽

Powder Samples ◽

Orange Colour

The adsorption of the water-soluble tetra(p-sulphophenyl)porphyrin (TPPS) compound on Fe(II), Fe(III), Cu(II), Co(II), Ni(II), Zn(II), Cd(II), Sn(IV) and UO22+ metal ion-exchanged montmorillonite (MMT) facilitated the formation of the SAT metal-TPPS MMT complexes of these cations (where SAT indicates sitting atop, ie the metal is above the porphyrin plane and is bound to external ligands in this case the MMT surface). All the resulting powder samples have a brown-orange colour due to the presence of the metal-TPPS-MMT complexes of these cations. Heating the solid powder samples caused demetallation and changed the colour of the powder from brown-orange colour of the metal-TPPS-MMT complex to the green colour of the diacid porphyrin on the clay. When such samples were exposed to the open atmosphere where they could absorb water vapour, the brown-orange colour appeared again due to the remetallation. The cation remained in the vicinity of the TPPS molecule upon demetallation, which makes the metallation-demetallation process reversible. The TPPS has been found to be adsorbed only on the external surface, and can be intercalated using sodium ions in solution with the compound to open the clay lattice. The reactions were monitored using visible absorption spectra, diffuse reflectance spectra, Mössbauer spectroscopy and X-ray diffraction.

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Concentration determination of chromatin in unstained resin-embedded sections by means of Z-contrast in STEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100134521 ◽

1990 ◽

Vol 48 (2) ◽

pp. 186-187

Author(s):

M. Haider ◽

B. Bohrmann

Keyword(s):

Energy Loss ◽

Freeze Substitution ◽

Biological Macromolecules ◽

Local Concentration ◽

E Coli ◽

Concentration Determination ◽

Phosphorous Content ◽

Z Contrast ◽

Electron Energy Loss

The technique of Z-contrast in STEM offers the possibility to determine the local concentration of macromolecules like lipids, proteins or DNA. Contrast formation depends on the atomic composition of the particular structure. In the case of DNA, its phosphorous content discriminates it from other biological macromolecules. In our studies, sections of E. coli, the dinoflagellate Amphidinium carterae and Euglena spec. cells were used which were obtained by cryofixation followed by freeze-substitution into acetone with 3% glutaraldehyde. The samples were then embedded either in Lowicryl HM20 at low temperature or in Epon at high temperature. Sections were coated on both sides with 30Å carbon.The DF- and the inelastic image have been recorded simultaneously with a Cryo-STEM. This Cryo-STEM is equipped with a highly dispersive Electron Energy Loss Spectrometer. With this instrument pure Z-contrast can be achieved either with a Filtered DF-image divided by the inelastic image or, as is used in this paper, by dividing the conventional DF-image by an inelastic image which has been recorded with an inelastic detector whose response is dependent on the total energy loss of the inelastically scattered electrons.

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A study of oxygen and vacancy ordering in YBa2Cu3O7−x

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100152793 ◽

1989 ◽

Vol 47 ◽

pp. 164-165

Author(s):

Y. P. Lin ◽

A. H. O’Reilly ◽

J. E. Greedan ◽

M. Post

Keyword(s):

Electron Microscopy ◽

Neutron Diffraction ◽

Oxygen Content ◽

Carbon Film ◽

Nitrogen Atmosphere ◽

Vacancy Ordering ◽

Powder Samples ◽

Vacancy Chains ◽

Chain Ordering

In the basal planes of the orthorhombic YBa2Cu3O7-X compound with x=0.07, which has a Tc of around 90K, chains of copper-oxygen are formed along the [010] direction. Previous investigations on the variation of Tc with oxygen content have shown the existence of a plateau at Tc = 60K for x=0.3 to 0.4, suggesting the presence of a separate phase. This phase has also been identified to be orthorhombic, but with a 2x superlattice along [100] of the parent structure, and the superlattice has been attributed to the formation of alternating copper-oxygen and copper-vacancy chains. In our work, we have studied the chain ordering phenomenon by electron microscopy and neutron diffraction on samples with different oxygen contents. We report here some of our electron microscopy findings for samples with x=0.4.Powder samples of YBa2Cu3O7-X were prepared by controlled re-oxidation of previously reduced material. For electron microscopy, the sample was dry ground using a mortar and pestle in a dry nitrogen atmosphere without the use of any solvent and transferred dry onto holey carbon film for examination in a Philips CM12 microscope.

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