A Luminescent Probe Study of Water/Acetonitrile Mixtures

1979 ◽  
Vol 32 (2) ◽  
pp. 271 ◽  
Author(s):  
AJ Easteal
Keyword(s):  
Salicylic Acid ◽  
Luminescence Band ◽  
Composition Dependence ◽  
Water Structure ◽  
Luminescence Spectra ◽  
Broad Emission Band ◽  
Luminescent Probe ◽  
Broad Emission ◽  
Alcohol Mixtures ◽  
Water Alcohol

Luminescence spectra for 1.0 × 10-2 mol dm-3 solutions of salicylic acid in water, acetonitrile and water/acetonitrile mixtures have been determined. In the wavelength range 300-600 nm, all spectra showed a single broad emission band. The variations of the wavelength of maximum luminescence intensity (λmax) and luminescence band half-width (Δ�) with solvent composition are similar to the composition dependence of these parameters observed previously for solutions of salicylic acid in water/alcohol mixtures. The invariance of Δ� with acetonitrile content up to approximately 15 mole% supports earlier conclusions that up to c. 15 mole% acetonitrile is accommodated within cavities in the water structure. The rapid increase in near 15 mole% acetonitrile provides further evidence for a progressive destruction of the water structure as the acetonitrile content is increased beyond c. 15 mole%.

scholarly journals Defect Characterization in ZnGeP2 by Time -Resolved Photoluminescence

1996 ◽  
Vol 450 ◽  
Author(s):  
N. Dietz ◽  
W. Busse ◽  
H. E. Gumlich ◽  
W. Ruderman ◽  
I. Tsveybak ◽  
...  
Keyword(s):  
Energy Range ◽  
Infrared Emission ◽  
Luminescence Spectra ◽  
Broad Emission Band ◽  
Wide Energy Range ◽  
Time Resolved ◽  
Broad Emission ◽  
Donor Acceptor ◽  
Donor States ◽  
Time Resolved Photoluminescence

AbstractSteady state and time-resolved photoluminescence (PL) investigations on ZnGeP2 crystals grown from the vapor phase by high pressure physical vapor transport (HPVT) and from the melt by gradient freezing (GF) are reported. The luminescence spectra reveal a broad infrared emission with peak position at 1.2 eV that exhibits features of classical donor-acceptor recombination. The hyperbolic decay characteristic over a wide energy range, investigated from 1.2 eV up to 1.5eV, suggest that this broad emission band is related to one energetic recombination center. Higher energetic luminescence structures at 1.6eV and 1.7eV were revealed after annealing of ZnGeP2 crystals in vacuum for a longer period of time. The emission decay behavior in this energy range is characterized by two hyperbolic time constants, viewed as the supercomposition of the decay from the broad emission center peaked at 1.2eV and additional donor-acceptor recombination emissions at 1.6eV and 1.7eV, respectively. ZnGeP2 crystals grown under Ge-deficient conditions by HPVT show an additional emission structure at 1.8 eV with sharp emission fine structures at 1.778 eV related to the presence of additional donor states.

Thermodynamic properties of water in the water-poor region of binary water + alcohol mixtures

2005 ◽  
Vol 83 (5) ◽  
pp. 420-429 ◽  
Author(s):  
Karin Liltorp ◽  
Peter Westh ◽  
Yoshikata Koga
Keyword(s):  
Hydrogen Bonding ◽  
Composition Dependence ◽  
Pure Water ◽  
Molar Enthalpy ◽  
Partial Molar Enthalpy ◽  
Alcohol Water ◽  
Mixing Schemes ◽  
Alcohol Mixtures ◽  
Excess Partial Molar Enthalpy ◽  
Water Alcohol

In our previous thermodynamic studies, we suggested that alcohol molecules in water-poor water + alcohol mixtures exist as alcohol clusters in a form similar to the pure alcohols. Here, we use calorimetry and densitometry to investigate how H2O interacts with alcohol clusters in water-poor binary aqueous mixtures of 12 different alcohols. The composition dependence of the measured excess partial molar enthalpy and volume of water (HEW and VEW), along with entropy data calculated from HEW and literature data for excess chemical potentials, showed that in water-poor solutions of small alcohols such as methanol, ethanol, and 1-propanol, mutual water–water interactions are endothermic, but entropically favorable. Conversely, in long-chain solvents such as 1-octanol and 1-decanol, the interaction is exothermic and entropically unfavorable. We suggest that these observations reflect water–alcohol hydrogen bonding in short-chain solvents and water clustering with more hydrogen bonding than in pure water or "dewetting" in mixtures of the longer alcohols, respectively. The composition dependence of HEW was also used to locate anomalies that specify the boundary between the mixing schemes characterizing the intermediate and the water-poor regions of alcohol + water mixtures.Key words: aqueous alkane-mono-ols, excess partial molar enthalpy, entropy and volume, mixing schemes.

Native Defect Characterization in ZnGeP2

1999 ◽  
Vol 607 ◽  
Author(s):  
A. Hoffmann ◽  
H. Born ◽  
A. Näser ◽  
W. Gehlhoff ◽  
J. Maffetone ◽  
...  
Keyword(s):  
Energy Range ◽  
Infrared Emission ◽  
Peak Position ◽  
Metastable Equilibrium ◽  
Chalcopyrite Structure ◽  
Luminescence Spectra ◽  
Broad Emission Band ◽  
Cation Sublattice ◽  
Broad Emission ◽  
Donor Acceptor

AbstractElectron paramagnetic resonance (EPR) as well as time-resolved and time-integrated photoluminescence (PL) are used to characterize the defect centers in ZnGeP2 bulk crystals. The samples, as-grown, electron-irradiated and annealed, reveal a strong intensity dependence of the VZn-correlated EPR-transitions. Photo-EPR experiments show that this intensity behavior is mainly caused by a recharging of the VZn centers owing to the preparation induced shift of the Fermi-level. The luminescence spectra show a broad infrared emission with peak position at 1.23 eV that exhibits features of classical donor-acceptor recombination. The hyperbolic decay characteristics, investigated in energy range from 1.2 eV up to 1.5eV, suggest that this broad emission band is related to one energetic recombination center. This recombination is interpreted to be between donor-acceptor states related to residual disorder on the cation sublattice that is retained in metastable equilibrium during the formation of the chalcopyrite structure. The emission decay behavior in the energy range from 1.2 eV up to 1.6 eV is characterized by two hyperbolic time constants, and explained as the super-composition of the decays from the broad emission center peaked at 1.2 eV and an additional donor-acceptor recombination centers at 1.4 eV.

Equilibria in Water–Alcohol Mixtures

Nature ◽  
1963 ◽  
Vol 199 (4894) ◽  
pp. 692-693 ◽  
Author(s):  
A. JOHNSON ◽  
B. B. NILAWAR ◽  
R. H. PETERS
Keyword(s):  
Alcohol Mixtures ◽  
Water Alcohol

scholarly journals The Effects of the Characteristics of Support Layers on Separation of Water-Alcohol Mixtures through Chitosan Pervaporation Composite Membranes.

MEMBRANE ◽  
1995 ◽  
Vol 20 (3) ◽  
pp. 229-238
Author(s):  
Qunhui Guo ◽  
Haruhiko Ohya ◽  
Youichi Negishi ◽  
Jicai Huang
Keyword(s):  
Composite Membranes ◽  
Alcohol Mixtures ◽  
Water Alcohol

Lu3(Al,Si)5(O,N)12:Ce3+ phosphors with broad emission band and high thermal stability for white LEDs

2015 ◽  
Vol 158 ◽  
pp. 322-327 ◽  
Author(s):  
Jiaqing Liu ◽  
Xiaojun Wang ◽  
Tongtong Xuan ◽  
Chunbo Wang ◽  
Huili Li ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Emission Band ◽  
High Thermal Stability ◽  
Broad Emission Band ◽  
White Leds ◽  
Broad Emission
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