Surface photochemistry: the effect of surface modification on the photophysics of naphthalene and pyrene adsorbed on silica gel

1984 ◽  
Vol 62 (7) ◽  
pp. 1279-1286 ◽  
Author(s):  
Richard K. Bauer ◽  
Paul de Mayo ◽  
Lalgudi V. Natarajan ◽  
William R. Ware
Keyword(s):  
Heat Treatment ◽  
Silica Gel ◽  
Ground State ◽  
Emission Spectra ◽  
Fluorescence Decay ◽  
Relative Importance ◽  
Broad Emission ◽  
State Association ◽  
Excimer Formation ◽  
Effect Of Surface

The influence of heat treatment and of added coadsorbates on the surface photophysics of pyrene and naphthalene adsorbed on silica gel is reported. When the silica gel surface is partially dehydroxylated, the distribution of pyrene or naphthalene is inhomogeneous, as indicated by multiexponential fluorescence decay and broad emission spectra. Addition of polar coadsorbates renders the surface more homogeneous with singlet lifetimes approaching solution values. The pretreatment and addition of coadsorbates, in the case of pyrene, also influence the relative importance of dynamic excimer formation vis-a-vis ground state association.

Modifications of Light Emission Spectra and Atomic Structure of Europium Molibdate Bulk Crystals Caused by High Pressure and Heat Treatment

2008 ◽  
Vol 55 (3) ◽  
pp. 1128-1132 ◽  
Author(s):  
S. Z. Shmurak ◽  
A. P. Kiselev ◽  
N. V. Klassen ◽  
V. V. Sinitsyn ◽  
I. M. Shmyt'ko ◽  
...  
Keyword(s):  
Heat Treatment ◽  
High Pressure ◽  
Atomic Structure ◽  
Light Emission ◽  
Emission Spectra ◽  
Bulk Crystals

scholarly journals Energy Transfer Study on Tb3+/Eu3+ Co-Activated Sol-Gel Glass-Ceramic Materials Containing MF3 (M = Y, La) Nanocrystals for NUV Optoelectronic Devices

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2522 ◽  
Author(s):  
Natalia Pawlik ◽  
Barbara Szpikowska-Sroka ◽  
Wojciech A. Pisarski
Keyword(s):  
Heat Treatment ◽  
Energy Transfer ◽  
Glass Ceramic ◽  
Sol Gel ◽  
Optoelectronic Devices ◽  
Emission Spectra ◽  
Ceramic Materials ◽  
Near Ultraviolet ◽  
Glass Ceramic Materials ◽  
Significant Prolongation

In the present work, the Tb3+/Eu3+ co-activated sol-gel glass-ceramic materials (GCs) containing MF3 (M = Y, La) nanocrystals were fabricated during controlled heat-treatment of silicate xerogels at 350 °C. The studies of Tb3+ → Eu3+ energy transfer process (ET) were performed by excitation and emission spectra along with luminescence decay analysis. The co-activated xerogels and GCs exhibit multicolor emission originated from 4fn–4fn optical transitions of Tb3+ (5D4 → 7FJ, J = 6–3) as well as Eu3+ ions (5D0 → 7FJ, J = 0–4). Based on recorded decay curves, it was found that there is a significant prolongation in luminescence lifetimes of the 5D4 (Tb3+) and the 5D0 (Eu3+) levels after the controlled heat-treatment of xerogels. Moreover, for both types of prepared GCs, an increase in ET efficiency was also observed (from ηET ≈ 16% for xerogels up to ηET = 37.3% for SiO2-YF3 GCs and ηET = 60.8% for SiO2-LaF3 GCs). The changes in photoluminescence behavior of rare-earth (RE3+) dopants clearly evidenced their partial segregation inside low-phonon energy fluoride environment. The obtained results suggest that prepared SiO2-MF3:Tb3+, Eu3+ GC materials could be considered for use as optical elements in RGB-lighting optoelectronic devices operating under near-ultraviolet (NUV) excitation.

Solubilization and fluorescence emission spectra of substances generated by thermal treatment of carbohydrates on silica gel

1984 ◽  
Vol 295 ◽  
pp. 123-128 ◽  
Author(s):  
Daniel Mario Alperin ◽  
Norberto Daniel Iusem ◽  
Victor Idoyaga-Vargas ◽  
Hector Carminatti
Keyword(s):  
Thermal Treatment ◽  
Silica Gel ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Fluorescence Emission Spectra

Fatigue in Engine Design

1953 ◽  
Vol 57 (513) ◽  
pp. 580-584
Author(s):  
F. M. Owner
Keyword(s):  
Crystal Structure ◽  
Heat Treatment ◽  
Cold Work ◽  
Controlled Atmosphere ◽  
The Core ◽  
Test Conditions ◽  
Engine Design ◽  
The Difference ◽  
Cylindrical Test ◽  
Effect Of Surface

The difference in outlook between metallurgist, physicist and designer on the problem of fatigue of metals is due not only to the differences in training and method but also in immediate objective, however closely their ultimate objectives may coincide.Physicists consider fatigue in terms of crystal structure and composition of the constituents of the crystal, noting in passing that certain types of crystal structures are associated with poor fatigue strength. The metallurgist's prime interest lies in the effect of surface finish, heat treatment, the physical condition of the surface, such as degree of cold work, the effect of carburised and nitrided cases having different hardness from the core. Both think in terms of controlled condition tests, with idealised test conditions such as cylindrical test specimens, close control of changes of section, polished surfaces of only a few micro-inches surface roughness, operating in a controlled atmosphere.

The effect of pressure on excimer formation

1965 ◽  
Vol 18 (7) ◽  
pp. 977 ◽  
Author(s):  
H Seidel ◽  
BK Selinger
Keyword(s):  
Excited State ◽  
Hydrostatic Pressure ◽  
Molar Volume ◽  
Aromatic Hydrocarbons ◽  
Ground State ◽  
Dominant Factor ◽  
Effect Of Pressure ◽  
Excimer Formation ◽  
Ground State Molecule ◽  
True Equilibrium

The formation of excited dimers by aromatic hydrocarbons in solution was found to be influenced by hydrostatic pressure. The increase in the viscosity of the solvent with pressure is the dominant factor for the more stable excited dimers and this causes a decrease in the amount of dimer with increasing pressure. Where there is a true equilibrium between excited dimer and monomer an increase in pressure causes an increase in dimer concentration. The change in molar volume for the formation of an excited dimer of 1,6-dimethylnaphthalene from a ground state molecule and one in the excited state was found to be -20 cm3 mole-1, representing a 10% reduction.

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