Green Shift Research Articles

Successive chemical solution deposition of ZnO films on flexible steel substrate: structure, photoluminescence and optical transitions

Zinc oxide is an attractive optoelectronic material with wide applications. Thin ZnO films were prepared on steel foil by successive chemical solution deposition (SCSD). The film structure, room-temperature photoluminescence (PL) and optical absorption characteristics were investigated. This study revealed that films of high structural and optical quality can be prepared by the SCSD method. PL of as-grown films shows a weak green peak at 560 nm and a strong UV peak at 380 nm. Annealing in either air or argon suppresses the green peak and red shifts the UV emission towards 390 nm. The presence of chlorine in the deposition solution destroys the PL of as-grown films. A strong UV emission, however, develops after annealing the films in air. Several optical transitions measured from the film PL and optical absorption coefficients are shown to be related to transitions through the known defect levels in ZnO, such as E1, L1, E3 and VO2+ levels.

Theoretical Investigation of Intercalated Water Molecules and Hydroxyl Groups in BAM ( BaMgAl10O17 : Eu2 + ) Phosphor and Associated Degradation Processes

Intercalation of water molecules into the β-alumina lattice of barium magnesium aluminate has been recently reported to be responsible for degradation of this phosphor. The associated degradation process is characterized by a green shift of the emission spectrum accompanied by oxidation of the activator ions. However, the structure and location of intercalated water molecules, and the degradation mechanism are not understood. In this report, both the location and geometry of water molecules are investigated using an atomistic simulation method with empirical interatomic potentials and a quantum mechanical method of structure optimization using full periodicity of the lattice. The oxidation of activator ions is modeled based on dissociation of water molecules to hydroxyl groups in this lattice. It is shown that the dissociation to hydroxyl groups is energetically favorable, and that the protons released in the process could be responsible for oxidation of europium ions.

Morphology and Stability of Flux Grown Blue Emitting BAM Phosphors for Plasma Display Panels Applications

The (BAM) phosphor is being used as a blue component in plasma display panels (PDPs) due to its color purity as well as its high luminescence efficiency. When compared to two other components (green and red), the degradation in brightness of the BAM phosphor is high. To understand the role of morphology in the degradation mechanism, a number of BAM samples with various flux materials, viz., alkali halides along with halides of ammonium and/or aluminum were prepared. In addition to green shift (peak maximum shifts toward green), the degradation in intensity of these phosphor materials was studied by heating samples in moisture and by exposing them to a high energy Xe flash lamp or Kr excimer lamp. By employing a specific type of alumina as a starting chemical and a suitable flux material in the preparation of the BAM phosphor by solid-state reaction, the green shift could be eliminated and the degradation minimized.

Sweden continues to pursue its green tax shift

Sweden continues to pursue its green tax shift

Five ways to be green and profitable

In this paper five ways to make money while staying green are described. These include a form of Eco-design (Design for environment) in which company, customer and societal benefits are taken into account, a new way of dealing with suppliers, green marketing and sales focussing on add-on benefits, increasing product quality through green and paradigm shifts in creative thinking both for improved and alternative products. These concepts can be applied separately but when combined there are substantial ramifications of the results.

Sol-gel materials for the solid phase extraction of metals from aqueous solution

Silica that was prepared by sol-gel chemistry to have pore widths in the microporous and in the mesoporous domains was evaluated as the host for performing solid phase extraction (SPE). Selective SPE of Ni II was accomplished with dimethylglyoxime (DMG)-doped silica, but the pore width was demonstrated to influence the chemistry of the material. With microporous silica as the host, the stoichiometry of the Ni II-DMG complex was 1:1 rather than 1:2, which is the value observed in aqueous solution. A green shift in the visible absorption spectrum was the primary evidence for the difference in stoichiometry; the alternative explanation of a rigidochromic effect on the spectrum was eliminated. The capacity of the DMG-doped mesoporous silica was only 9 μmol Ni g −1 because of leaching of the complexing agent. The microporous material showed no loss of DMG, but low permeability lowered the capacity. An alternative, albeit not selective, approach was to employ a mesoporous host to which a complexing agent, diethylenetriamine (DTA), was covalently bound. In this case, a capacity of 0.156 mmol Cu g −1, was achieved.

Vat dye sensitised fibre damage and dye fading by catalytic and activated peroxide bleaching

At equal levels of performance, activated (TAED) and catalytic (Mn-TMTACN) laundry bleaching can differ considerably in terms of the concomitant damage to fibres and dyes. To quantify this damage, differently dyed cotton fabrics, and a representative set of eight vat dyes and CI Reactive Brown 7 were used. It is shown that dye fading and fibre degradation are dye-specific and are both highly coupled phenomena. The interpretation of the damage data is based on dye chemistry, reflectance spectroscopy (UV/VIS and NIR) and EPR measurements. Whereas compelling evidence for a genuine catalytic cycle with the quoted manganese complex is lacking, a possible catalytic role of the dyes is proposed. The dramatic green shift resulting from the catalytic bleaching of Cl Vat Blue 4 is explained in detail. The corresponding oxidation is reversible and possibly useful as a fibre damage indicator.

Chromaticity and electroluminescent efficiency of atomic layer epitaxy SrS:Ce thin films

We have studied various factors that control the luminous properties of atomic layer epitaxy (ALE) SrS:Ce electroluminescent (EL) devices by using electron paramagnetic resonance, photoluminescent decay, x-ray diffraction, and charge-voltage characterization. EL and PL light is green shifted in ALE SrS:Ce films, compared to powders and thin films prepared with some other techniques. The origin of the green shift is discussed. Moderate heat treatments of as-deposited SrS:Ce devices were found to dramatically improve the EL efficiency. This is due to the removal of defects leading to nonradiative Ce3+ decay and to reduction of Ce4+ to radiative Ce3+. Different heat treatments were found to influence the transferred charge, so that there is an optimal heat treatment temperature between 500 and 750 °C. Heat treatments also induce macroscopic stress in these SrS:Ce films. This was seen to induce a local stress around Ce3+ sites. However, the stresses were not found to directly correlate with the luminous efficiency. The SrS:Ce growth temperature was found to affect the Ce3+ excitation efficiency in EL. Electronic traps in SrS:Ce films are discussed. We suggest that some traps can be beneficial in providing necessary charge for the Ce3+ excitation process and others can be deleterious in that they suppress radiative Ce3+ decay events. To determine the effects of Ce doping, undoped SrS films were also deposited and fully characterized. Finally, we compare the properties of films prepared by ALE to those deposited via rf sputtering.

Investigation of complex anisotropic centers of blue and green luminescence of SrS:Ce by the method of the polarized intracentral photoexcitation

In this work, we investigate the luminescent properties of SrS:Ce powders with different activator concentrations. The method of linear polarized intracentral photo excitation and luminescence, which has been co-developed by the author, was used for the detection of anisotropic luminescent centers in amorphous and polycrystalline compounds. The dependence of the luminescence band intensity on the polarization and on the excitation wavelength for different cerium concentrations shows that the Ce 3+ ions form complex luminescent centers with different positions of the impurities and the native V sr defects in neighboring sites of the SrS crystal lattice. These associates cause the green shift of the SrS:Ce blue emission.

Unique hue judgments as a function of test size in the fovea and at 20-deg temporal eccentricity

Unique hue loci were measured for four observers in the fovea and at 20-deg temporal eccentricity as a function of test size. Eccentric measurements were made on the cone plateau following a rod bleach. The results indicate that unique yellow remains approximately invariant with respect to test size and retinal eccentricity, whereas unique blue and unique green shift to longer wavelengths with increasing test size. The locus of unique blue in the periphery reaches an asymptote at approximately the same wavelength as that from the foveal measurements, whereas unique green measured in the periphery is consistently at shorter wavelengths than in the fovea. In general, the data are best described by a model in which the short-wavelength-sensitive cone input to the two opponent-color channels decreases with decreasing test size and increasing retinal eccentricity.

Remote sensing of the xanthophyll cycle and chlorophyll fluorescence in sunflower leaves and canopies.

Sudden illumination of sunflower (Helianthus annuus L. cv. CGL 208) leaves and canopies led to excess absorbed PFD and induced apparent reflectance changes in the green, red and near-infrared detectable with a remote spectroradiometer. The green shift, centered near 531 nm, was caused by reflectance changes associated with the de-epoxidation of violaxanthin to zeaxanthin via antheraxanthin and with the chloroplast thylakoid pH gradient. The red (685 nm) and near-infrared (738 nm) signals were due to quenching of chlorophyll fluorescence. Remote sensing of shifts in these spectral regions provides non-destructive information on in situ photosynthetic performance and could lead to improved techniques for remote sensing of canopy photosynthesis.

Influence of organic material on mineralization processes in the Permian Kupferschiefer formation, Poland

The Permian Kupferschiefer horizon in Southwest Poland acted as a geochemical trap by accumulating metals from an ascending oxidizing brine. The hydrogen-rich organic material in the Kupferschiefer supplied sufficient reduction equivalents for the precipitation of base and precious metals from these brines by redox reactions. This is indicated by regular changes in the molecular composition of the extractable organic material in a set of samples collected from a 1.4 m thick horizon in a Polish mine. The degree of oxidation is shown to change drastically from the bottom to the top of the horizon. In the bottom section, saturated hydrocarbons are diminished and heteroaromatic systems containing oxygen and sulphur are enriched significantly; alkylated aromatic hydrocarbon abundances are relatively low. The ratio of phenanthrene/sum of methylphenanthrenes varies with the degree of oxidation. Spectral fluorescence measurements reveal an increase in fluorescence intensities of the extracts with increasing oxidation. Moreover, the green shift of fluorescence maxima is related to oxidation effects. Parallel to the intensity of oxidation, as observed from changes in the extractable organic matter, the content of copper and silver changes within the horizon. The results confirm that organic matter in sediments, under appropriate geological conditions, can play a significant role in ore formation processes.

Changes in the circadian rhythmicity of hydroxyindole-O-methyl transferase (HIOMT) activity in the synthesis of 5-methoxyindoles in the pineal gland of 28 day old male Wistar rats exposed to white, red and green light.

Hydroxyindole-O-methyl transferase activity for the synthesis of 5-methoxyindoles was investigated in the pineal gland of 28 day old male Wistar rats after exposure to white, red and green light for 12 hours daily. It could be demonstrated that, in comparison to white light, red light causes a shift of HIOMT activity for the synthesis of melatonin/5-methoxytryptophol towards an earlier period being highest between 12 and 16 hours. The synthesis of 5-methoxytryptamine and of 5-methoxytryptophan is shifted to 16 hours, while the synthesis of 5-methoxyindole-3-acetic acid, which normally peaks at 16 hours, is increased at this same hour. Green light shifts HIOMT activity for the synthesis of melatonin/5-method being highest between 12 and 16 hours. The synthesis of 5-methoxytryptamine and of 5-methoxytryptophan is shifted to 16 hours, while the synthesis of 5-methoxyindole-3-acetic acid, which normally peaks at 16 hours, is increased at this same hour. Green light shifts HIOMT activity for the synthesis of melatonin/5-method being highest between 12 and 16 hours. The synthesis of 5-methoxytryptamine and of 5-methoxytryptophan is shifted to 16 hours, while the synthesis of 5-methoxyindole-3-acetic acid, which normally peaks at 16 hours, is increased at this same hour. Green light shifts HIOMT activity for the synthesis of melatonin/5-methoxytryptophol to a later period, showing a peak at 24 hours. The synthesis of 5-methoxytryptamine is significantly increased at 24 hours. An increase is also observed in the synthesis of 5-methoxyindole-3-acetic acid at 12 and at 4 hours, times at which this synthesis is also maximal using white light, whereas the synthesis of 5-methoxytryptophan is generally decreased. A possible relationship between the present results and those obtained after exposure to different wavelengths of light on N-acetyltransferase activity, the effect of pterins on HIOMT activity and the effect of different wavelengths on gonadal growth are discussed.

The post-mortem detection of early myocardial infarction by a simple fluorescent method.

A rapid and simple method is described for demonstrating early ischaemic/anoxic damage to the myocardium due either to coronary artery disease or hypertensive heart disease. Using formalin-fixed paraffin-embedded standard histological sections, staining for only 3 seconds in an aqueous solution of acridine-orange was sufficient to demonstrate a green shift of the secondary emission produced when the section was viewed in ultraviolet light. The results correlated well with sensitive enzyme studies which, however, were technically more difficult. The ease of retaining tissues and the rapidity of the technique, coupled with the reliability of the method even in the presence of moderate post-mortem autolysis, makes this a useful method for routine use.

Resistance due to potential scattering in dilute magnetic alloys

The resistance due to impurity potential scattering and spin-disorder scattering are additive in simple Born approximation. If the impurity scattering is calculated generally by a Green function or phase shift analysis it is also found to affect the spin-disorder scattering because of the modification of the local charge density. This is calculated using the previous Green function method when the spin scattering is derived to second order both for spin-ordered and spin-disordered systems. It is also calculated for spin effects in third order (Kondo effect) in the spin-disordered case. It is found that the spin resistivity is markedly affected in magnitude and in sign if a resonance is caused by the impurity potential near the Fermi energy.

Romanowsky-type staining: enzymatic analysis of nuclear metachromasia in formalin-fixed paraffin sections.

The red color of nuclei produced in formol-fixed paraffin sections stained with toluidine blue has been investigated by using deoxyribonuclease (DNase), ribonuclease (RNase) and 0.1 M Tris buffer. The action of DNase on formol-fixed material is not fully reliable, but clear-cut when positive. Nuclear basophilia and metachromasia is removed, nucleolar and cytoplasmic RNA is preserved. The picture produced by RNase depends to some extent on the concentration and acidity of the toluidine blue used for subsequent staining. Cytoplasmic RNA is always removed, while the red stain in nuclei usually remains intact. With 0.1% toluidine blue in 1% acetic acid, a nuclear color change from red to pale green is observed. Using this same staining solution, it can be shown that 0.1 M Tris buffer (overnight extraction at 37° C) will remove cytoplasmic RNA but leave intact the nuclear material that stains red. A red to green shift can subsequently be produced by RNase. From this it is deduced that there is a chromatin-associated nuclear RNA fraction which can be removed by the enzyme, but is stable to the buffer solution.

The Green Raylat Sunset and Sunrise

As the green segment continues to be debated, permit me to put a few facts on record. I have often in Egypt watched the sunrise light descending the western hills, and when the edge of the shadow reached me, turned to view the sun. The first appearance of the sun is a blue segment, changing to green, and then to white. This is exactly the converse of the colours of the sunset segment; as the rising light cannot be due to an after-image, no more is the setting light. Moreover I have never seen the green light shift about, as an after-image does, by movement of the eye; it is always exactly on the segment.