Stability of fast elaborated small CdS quantum dots

2011 ◽  
Vol 1286 ◽  
Author(s):  
M. Fregnaux ◽  
S. Dalmasso ◽  
J.-J. Gaumet ◽  
J.-P. Laurenti
Keyword(s):  
Absorption Spectra ◽  
Broad Band ◽  
Surface States ◽  
The Other ◽  
Cds Quantum Dots ◽  
Other Hand ◽  
Direct Exposure ◽  
Single Source Precursor ◽  
Excitonic Transition ◽  
Excitonic Emission

ABSTRACTSmall size CdS QDs were synthesized by (i) the single source precursor methodology and by (ii) the microwave synthetic route. The consequences of CdS QD direct exposure to air for a period of 7 days were investigated by following the evolution of the photoluminescence (PL) and absortion spectra. For QDs obtained by (i), the excitonic emission band (3.0 ‑ 3.1 eV) decreases in intensity, relatively to the low energy one (2.2 ‑ 2.5 eV) tentatively associated to midgap surface states. This suggests arising of new recombination path(s) associated to degradations during aging, possibly an oxidative formation of a CdO surface layer. On the other hand, no significant change is observed in the absorption spectra. For QDs obtained by (ii), no degradation is revealed by the PL spectra which remain unchanged. On the other hand, the absorption spectra are dominated by an unexplained broad band around 3.6 eV which tends to hide the fundamental excitonic transition one and increases in intensity with aging.

Complexes moléculaires d'hétérocycles soufrés et oxygénés. Étude spectrophotométrique de bandes de transfert de charge multiples

1982 ◽  
Vol 60 (7) ◽  
pp. 862-871 ◽  
Author(s):  
Jean-Paul Canselier ◽  
Serge Domenech ◽  
Štefan Stankovsky ◽  
Sabine Gautier
Keyword(s):  
Charge Transfer ◽  
Absorption Spectra ◽  
Electronic Absorption ◽  
Electronic Absorption Spectra ◽  
Molecular Complexes ◽  
The Other ◽  
Ionization Potentials ◽  
Nonpolar Solvents ◽  
Other Hand ◽  
The One

As with benzenoid donors, the electronic absorption spectra of the molecular complexes of simple or condensed sulfur or oxygen-containing five-membered heterocycles with TCNE (or DDQ) often show two charge-transfer bands. In many cases, the knowledge of the actual frequencies requires a technique of resolution. The results so obtained are correlated with the ionization potentials of donors on the one hand, and the refractivity of nonpolar solvents on the other hand.

The aggregation of copper phthalocyanine dyes

1972 ◽  
Vol 25 (8) ◽  
pp. 1661 ◽  
Author(s):  
LC Gruen
Keyword(s):  
Dielectric Constant ◽  
Ionic Strength ◽  
Absorption Spectra ◽  
Copper Phthalocyanine ◽  
Reactive Dyes ◽  
The Other ◽  
Visible Absorption ◽  
Monomeric Species ◽  
Other Hand ◽  
Phthalocyanine Dyes

The visible absorption spectra of two reactive dyes based on the copper phthalocyanine chromophore have been investigated as a function of concentration, temperature, pH, ionic strength, and solvent. The persistence of isosbestic points indicates that an equilibrium exists, over the concentration range investigated, between two forms of the dye only, namely dimer and monomer. The addition of urea exerts a relatively small disaggregating influence on this equilibrium. On the other hand decrease in dielectric constant substantially changes the equilibrium in favour of the monomeric species.

Observations on the colouring of pink and green zoned tourmaline

1953 ◽  
Vol 30 (220) ◽  
pp. 26-38 ◽  
Author(s):  
J. E. S. Bradley ◽  
Olive Bradley
Keyword(s):  
Absorption Spectra ◽  
Absorption Spectroscopy ◽  
Emission Spectra ◽  
The Other ◽  
Other Hand

This investigation was concerned with two aspects of the colour-zoning in tourmaline: firstly, the origin of the green and pink colours ; secondly, the reason for the apparent incompatibility of these two forms. Much of the previous work on the colour of tourmaline has involved the use of emission spectra. This method provides information as to which elements are present; it does not, of course, indicate which of the twenty or so elements identified is responsible for the colour, although it may be possible to infer this. Absorption spectra, on the other hand, are directly concerned with colour. They have been employed quite extensively in Germany, and more recently in Russia, but the earlier data and instruments were often inadequate. The last decade has seen marked improvements in the technique of absorption spectroscopy, particularly in the development of photo-electric methods for the quantitative recording of spectra, and the method is likely to prove one of increasing value.

Mechanism of the formation of halogen monoxides during flash photolysis of halogen + oxygen mixtures

1963 ◽  
Vol 271 (1346) ◽  
pp. 289-295 ◽  
Keyword(s):  
Absorption Spectra ◽  
Flash Photolysis ◽  
Radiant Energy ◽  
The Other ◽  
Other Hand ◽  
Absorption Of Light ◽  
Oxygen Atoms

The mechanism of the formation of BrO and CIO in the flash photolysis of halogen + oxygen mixtures was investigated. It was found that the predominant mechanism for the production of BrO (about 90 % in our experiments) involves the absorption of light by the oxygen molecules. The O* 2 or the oxygen atoms produced create ozone, which in turn produces BrO when photolyzed. It is possible that some of O* 2 or O produces BrO directly and not via an ozone intermediate. About 10 % of the BrO is produced when two quanta of radiant energy are absorbed by the Br 2 molecule. The highly energetic molecule formed in this way is capable of breaking the O—O bond and forming BrO. The reaction between the excited Br atoms and O 2 , suggested by Durie & Bamsey (1958), does not occur. It seems likely that IO is formed by a mechanism similar to that of BrO. On the other hand, CIO is produced predominantly in a reaction of Cl( 2 P ) atoms with O 2 , as suggested by Porter & Wright (1953). Chlorine and bromine absorption spectra were measured down to 1880 and 1930 Å, respectively.

A study of cometary eruptions through OH radio-lines

1999 ◽  
Vol 173 ◽  
pp. 249-254
Author(s):  
A.M. Silva ◽  
R.D. Miró
Keyword(s):  
Short Duration ◽  
Growth Curves ◽  
The Other ◽  
Initial Mass ◽  
Radio Lines ◽  
Other Hand ◽  
Sudden Rise

AbstractWe have developed a model for theH2OandOHevolution in a comet outburst, assuming that together with the gas, a distribution of icy grains is ejected. With an initial mass of icy grains of 108kg released, theH2OandOHproductions are increased up to a factor two, and the growth curves change drastically in the first two days. The model is applied to eruptions detected in theOHradio monitorings and fits well with the slow variations in the flux. On the other hand, several events of short duration appear, consisting of a sudden rise ofOHflux, followed by a sudden decay on the second day. These apparent short bursts are frequently found as precursors of a more durable eruption. We suggest that both of them are part of a unique eruption, and that the sudden decay is due to collisions that de-excite theOHmaser, when it reaches the Cometopause region located at 1.35 × 105kmfrom the nucleus.

Closing the GAP—A 5Å Scanning Microscope

1969 ◽  
Vol 27 ◽  
pp. 6-7
Author(s):  
A. V. Crewe
Keyword(s):  
Normal Form ◽  
The Other ◽  
Resolving Power ◽  
Scanning Microscope ◽  
Conventional Microscope ◽  
Other Hand ◽  
Closing The Gap ◽  
Thermal Sources ◽  
Better Than ◽  
Transmission Microscope

We have become accustomed to differentiating between the scanning microscope and the conventional transmission microscope according to the resolving power which the two instruments offer. The conventional microscope is capable of a point resolution of a few angstroms and line resolutions of periodic objects of about 1Å. On the other hand, the scanning microscope, in its normal form, is not ordinarily capable of a point resolution better than 100Å. Upon examining reasons for the 100Å limitation, it becomes clear that this is based more on tradition than reason, and in particular, it is a condition imposed upon the microscope by adherence to thermal sources of electrons.

Life Beyond 1MeV

1980 ◽  
Vol 38 ◽  
pp. 30-33
Author(s):  
K.H. Westmacott
Keyword(s):  
Electron Microscopy ◽  
Past Experience ◽  
The Other ◽  
Good Case ◽  
Other Hand ◽  
The U.S

Life beyond 1MeV – like life after 40 – is not too different unless one takes advantage of past experience and is receptive to new opportunities. At first glance, the returns on performing electron microscopy at voltages greater than 1MeV diminish rather rapidly as the curves which describe the well-known advantages of HVEM often tend towards saturation. However, in a country with a significant HVEM capability, a good case can be made for investing in instruments with a range of maximum accelerating voltages. In this regard, the 1.5MeV KRATOS HVEM being installed in Berkeley will complement the other 650KeV, 1MeV, and 1.2MeV instruments currently operating in the U.S. One other consideration suggests that 1.5MeV is an optimum voltage machine – Its additional advantages may be purchased for not much more than a 1MeV instrument. On the other hand, the 3MeV HVEM's which seem to be operated at 2MeV maximum, are much more expensive.

Can the Academic Self-Concept be Positive and Realistic?

2005 ◽  
Vol 19 (3) ◽  
pp. 129-132 ◽  
Author(s):  
Reimer Kornmann
Keyword(s):  
Academic Performance ◽  
Opposite Effect ◽  
Self Esteem ◽  
Point Of View ◽  
The Other ◽  
Self Concept ◽  
High Ability ◽  
Self Image ◽  
Other Hand

Summary: My comment is basically restricted to the situation in which less-able students find themselves and refers only to literature in German. From this point of view I am basically able to confirm Marsh's results. It must, however, be said that with less-able pupils the opposite effect can be found: Levels of self-esteem in these pupils are raised, at least temporarily, by separate instruction, academic performance however drops; combined instruction, on the other hand, leads to improved academic performance, while levels of self-esteem drop. Apparently, the positive self-image of less-able pupils who receive separate instruction does not bring about the potential enhancement of academic performance one might expect from high-ability pupils receiving separate instruction. To resolve the dilemma, it is proposed that individual progress in learning be accentuated, and that comparisons with others be dispensed with. This fosters a self-image that can in equal measure be realistic and optimistic.

Stories and the Self

2020 ◽  
Vol 32 (2) ◽  
pp. 47-58 ◽  
Author(s):  
Stefan Krause ◽  
Markus Appel
Keyword(s):  
Meta Analysis ◽  
The Self ◽  
The Other ◽  
Lower Degree ◽  
Contrast Effects ◽  
Self Perception ◽  
Self Perceptions ◽  
Other Hand ◽  
The One ◽  
Implicit And Explicit

Abstract. Two experiments examined the influence of stories on recipients’ self-perceptions. Extending prior theory and research, our focus was on assimilation effects (i.e., changes in self-perception in line with a protagonist’s traits) as well as on contrast effects (i.e., changes in self-perception in contrast to a protagonist’s traits). In Experiment 1 ( N = 113), implicit and explicit conscientiousness were assessed after participants read a story about either a diligent or a negligent student. Moderation analyses showed that highly transported participants and participants with lower counterarguing scores assimilate the depicted traits of a story protagonist, as indicated by explicit, self-reported conscientiousness ratings. Participants, who were more critical toward a story (i.e., higher counterarguing) and with a lower degree of transportation, showed contrast effects. In Experiment 2 ( N = 103), we manipulated transportation and counterarguing, but we could not identify an effect on participants’ self-ascribed level of conscientiousness. A mini meta-analysis across both experiments revealed significant positive overall associations between transportation and counterarguing on the one hand and story-consistent self-reported conscientiousness on the other hand.

Don’t Put Me in This Group

2019 ◽  
Vol 50 (2) ◽  
pp. 80-93
Author(s):  
Jort de Vreeze ◽  
Christina Matschke
Keyword(s):  
Positive Emotions ◽  
Negative Emotions ◽  
Negative Information ◽  
The Self ◽  
The Other ◽  
Other Hand ◽  
Group Memberships

Abstract. Not all group memberships are self-chosen. The current research examines whether assignments to non-preferred groups influence our relationship with the group and our preference for information about the ingroup. It was expected and found that, when people are assigned to non-preferred groups, they perceive the group as different to the self, experience negative emotions about the assignment and in turn disidentify with the group. On the other hand, when people are assigned to preferred groups, they perceive the group as similar to the self, experience positive emotions about the assignment and in turn identify with the group. Finally, disidentification increases a preference for negative information about the ingroup.

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