Optical properties of Cu− centres in NaCl crystals

1977 ◽  
Vol 55 (15) ◽  
pp. 1316-1321 ◽  
Author(s):  
Taiju Tsuboi
Keyword(s):  
Optical Properties ◽  
Spectral Range ◽  
Systematic Study ◽  
Vacuum Ultraviolet ◽  
Emission Spectra ◽  
Absorption Bands ◽  
Weak Absorption ◽  
Isoelectronic Series

For a systematic study of the isoelectronic series of s2-type centres, absorption, excitation and emission spectra of Cu− centres in NaCl crystals are investigated in the ultraviolet and vacuum ultraviolet spectral range at temperatures from 77 to 300 K. Two weak absorption bands were observed at 269 and 256 nm in addition to four bands at 288, 272, 232, and 189 nm which are assigned to the A, B, C and D bands of s2-type spectra, respectively, while only two emission bands peaking at 423 and 318 nm were detected. These results of Cu− centres are compared with those of the hitherto investigated s2-type centres.

scholarly journals Interactions between photoacidic 3-hydroxynaphtho[1,2-b]quinolizinium and cucurbit[7]uril: Influence on acidity in the ground and excited state

2017 ◽  
Vol 13 ◽  
pp. 203-212 ◽  
Author(s):  
Jonas Becher ◽  
Daria V Berdnikova ◽  
Darinka Dzubiel ◽  
Heiko Ihmels ◽  
Phil M Pithan
Keyword(s):  
Optical Properties ◽  
Excited State ◽  
Ground State ◽  
Emission Spectra ◽  
Weak Acid ◽  
Deprotonated Form ◽  
Absorption Bands ◽  
Absorption And Emission ◽  
Ph Values ◽  
Acidic Conditions

3-Hydroxynaphtho[1,2-b]quinolizinium was synthesized by cyclodehydration route and its optical properties in different media were investigated. The absorption and emission spectra of this compound depend on the pH of the solution. Thus, at higher pH values the deprotonation yields a merocyanine-type dye that exhibits significantly red-shifted absorption bands and causes a dual emisson, i.e., a combination of emission bands of the hydroxyquinolizinium and its deprotonated form. Whereas this compound is a weak acid in the ground state (pK a = 7.9), it has a strongly increased acidity in the excited state (pK a * = 0.4). As a result, the blue-shifted fluorescence of the hydroxyquinolizinium becomes dominant only under strongly acidic conditions. In addition, it is shown that 3-hydroxynaphtho[1,2-b]quinolizinium binds to cucurbit[7]uril (CB[7]) with moderate affinity (K b = 1.8 × 104 M−1, pH 5) and that the pK a and pK a * values of this ligand increase by about two to three orders of magnitude, respectively, when bound to CB[7].

scholarly journals Influence of Calcination Temperature on Crystal Growth and Optical Characteristics of Eu3+ Doped ZnO/Zn2SiO4 Composites Fabricated via Simple Thermal Treatment Method

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 115
Author(s):  
Suhail Huzaifa Jaafar ◽  
Mohd Hafiz Mohd Zaid ◽  
Khamirul Amin Matori ◽  
Sidek Hj. Ab Aziz ◽  
Halimah Mohamed Kamari ◽  
...  
Keyword(s):  
Thermal Treatment ◽  
Band Gap ◽  
Calcination Temperature ◽  
Emission Intensity ◽  
Emission Spectra ◽  
Treatment Method ◽  
Absorption Bands ◽  
Vis Spectroscopy ◽  
Doped Zno ◽  
Zno Crystal

This research paper proposes the usage of a simple thermal treatment method to synthesis the pure and Eu3+ doped ZnO/Zn2SiO4 based composites which undergo calcination process at different temperatures. The effect of calcination temperatures on the structural, morphological, and optical properties of ZnO/Zn2SiO4 based composites have been studied. The XRD analysis shows the existence of two major phases which are ZnO and Zn2SiO4 crystals and supported by the finding in the FT-IR. The FESEM micrograph further confirms the existence of both ZnO and Zn2SiO4 crystal phases, with progress in the calcination temperature around 700–800 °C which affects the existence of the necking-like shape particle. Absorption humps discovered through UV-Vis spectroscopy revealed that at the higher calcination temperature effects for higher absorption intensity while absorption bands can be seen at below 400 nm with dropping of absorption bands at 370–375 nm. Two types of band gap can be seen from the energy band gap analysis which occurs from ZnO crystal and Zn2SiO4 crystal progress. It is also discovered that for Eu3+ doped ZnO/Zn2SiO4 composites, the Zn2SiO4 crystal (5.11–4.71 eV) has a higher band gap compared to the ZnO crystal (3.271–4.07 eV). While, for the photoluminescence study, excited at 400 nm, the emission spectra of Eu3+ doped ZnO/Zn2SiO4 revealed higher emission intensity compared to pure ZnO/Zn2SiO4 with higher calcination temperature exhibit higher emission intensity at 615 nm with 700 °C being the optimum temperature. The emission spectra also show that the calcination temperature contributed to enhancing the emission intensity.

Structure and microstructure of near infrared-absorbing Au–Au2S nanoparticles

2007 ◽  
Vol 22 (9) ◽  
pp. 2531-2538 ◽  
Author(s):  
Mei Chee Tan ◽  
Jackie Y. Ying ◽  
Gan Moog Chow
Keyword(s):  
Optical Properties ◽  
Surface Segregation ◽  
Near Infrared ◽  
Small Degree ◽  
Core Shell ◽  
Shell Microstructure ◽  
Absorption Bands ◽  
Interfacial Effects ◽  
Nir Absorption ◽  
Structure And Microstructure

Near infrared (NIR) absorbing nanoparticles synthesized by the reduction of HAuCl4 with Na2S exhibited absorption bands at ∼530 nm, and in the NIR region of 650–1100 nm. The NIR optical properties were not found to be related to the earlier proposed Au2S–Au core-shell microstructure in previous studies. From a detailed study of the structure and microstructure of as-synthesized particles in this work, S-containing, Au-rich, multiply-twinned nanoparticles were found to exhibit NIR absorption. They consisted of amorphous AuxS (where x = 2), mostly well mixed within crystalline Au, with a small degree of surface segregation of S. Therefore, NIR absorption was likely due to interfacial effects on particle polarization from the introduction of AuxS into Au particles, and not the dielectric confinement of plasmons associated with a core-shell microstructure.

Composition, particle size, and near-infrared irradiation effects on optical properties of Au–Au2S nanoparticles

2008 ◽  
Vol 23 (1) ◽  
pp. 281-293 ◽  
Author(s):  
Mei Chee Tan ◽  
Jackie Y. Ying ◽  
Gan Moog Chow
Keyword(s):  
Particle Size ◽  
Optical Properties ◽  
Thermal Effects ◽  
Near Infrared ◽  
Sodium Sulfide ◽  
Irradiation Effects ◽  
Absorption Bands ◽  
Molar Ratios ◽  
Nir Absorption ◽  
Structure And Microstructure

Near-infrared (NIR)-absorbing nanoparticles synthesized by the reduction of tetrachloroauric acid (HAuCl4) using sodium sulfide (Na2S) exhibited absorption bands at ∼530 nm and at the NIR region of 650−1100 nm. A detailed study on the structure and microstructure of as-synthesized nanoparticles was reported previously. The as-synthesized nanoparticles were found to consist of amorphous AuxS (x = ∼2), mostly well mixed within crystalline Au. In this work, the optical properties were tailored by varying the precursor molar ratios of HAuCl4 and Na2S. In addition, a detailed study of composition and particle-size effects on the optical properties was discussed. The change of polarizability by the introduction of S in the form of AuxS (x = ∼2) had a significant effect on NIR absorption. Also, it was found in this work that exposure of these particles to NIR irradiation using a Nd:YAG laser resulted in loss of the NIR absorption band. Thermal effects generated during NIR irradiation had led to microstructural changes that modified the optical properties of particles.

ELECTRONIC STRUCTURE AND OPTICAL PROPERTIES OF CRYSTALLINE C60

1992 ◽  
Vol 06 (06) ◽  
pp. 309-321 ◽  
Author(s):  
W.Y. CHING ◽  
MING-ZHU HUANG ◽  
YONG-NIAN XU ◽  
FANQI GAN
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
First Principles ◽  
Optical Spectrum ◽  
Local Density ◽  
Low Dielectric Constant ◽  
Experimental Measurements ◽  
Absorption Bands ◽  
Low Dielectric ◽  
Good Agreement

The electronic structure and optical properties of crystalline C 60 and their pressure dependence have been studied by first-principles local density calculations. It is shown that fcc C 60 has a low dielectric constant and an optical spectrum rich in structures. The spectrum shows five disconnected absorption bands in the 1.4 to 7.0 eV region with sharp structures in each band that can be attributed to critical point transitions. This is a manifestation of the localized molecular structure coupled with long range crystalline order unique to the C 60 crystal. At a sufficient high pressure, the structures in the optical spectrum start to merge due to the merging of the bands. These results are in good agreement with some recent experimental measurements.

Optical properties of selected native and coagulated human brain tissues in vitro in the visible and near infrared spectral range

2002 ◽  
Vol 47 (12) ◽  
pp. 2059-2073 ◽  
Author(s):  
A N Yaroslavsky ◽  
P C Schulze ◽  
I V Yaroslavsky ◽  
R Schober ◽  
F Ulrich ◽  
...  
Keyword(s):  
Optical Properties ◽  
Human Brain ◽  
Spectral Range ◽  
Near Infrared ◽  
Infrared Spectral Range ◽  
Infrared Spectral ◽  
Brain Tissues

Enhancement of optical properties of poly (9,9′-di-n-octylfluorenyl-2,7-diyl) in conjugated polymer/TiO2 nanocomposites

2014 ◽  
Vol 92 (9) ◽  
pp. 1021-1025 ◽  
Author(s):  
Bandar Ali Al-Asbahi ◽  
Mohammad Hafizuddin Haji Jumali
Keyword(s):  
Optical Properties ◽  
Conjugated Polymer ◽  
Emission Spectra ◽  
Treatment Temperature ◽  
Nanocomposite Films ◽  
Glass Substrates ◽  
Solution Blending ◽  
Heat Treated ◽  
Blending Method ◽  
Splitting Energy

The influence of colloidal TiO2 nanoparticle contents on the optical properties of poly (9,9′-di-n-octylfluorenyl-2,7-diyl) conjugated polymer (PFO) has been investigated. The solution blending method was used to prepare homogenous PFO/TiO2 nanocomposite. The nanocomposite films were prepared on glass substrates using the spin-coating technique. The films were divided into two groups, the first was left to dry at room temperature while the second was heat-treated at 120 °C for 1 h. Absorption and emission spectra showed that the PFO existed in α- and β-phases morphology having monomeric, excimeric, and double excimeric states. In addition, both spectra revealed that TiO2 contents and heat treatment temperature extended the conjugation length of PFO. Finally, emission spectra for both cases exhibited decreasing in the line width of zero-phonon emission spectra and increasing in the vibronic splitting energy, upon increment of the TiO2, led to a significant increase in π-electron delocalization and lower degree in chain disorder.

Influence of the Dispersion of the Size of the Si Nanocrystals on their Emission Spectra

1994 ◽  
Vol 358 ◽  
Author(s):  
J. B. Khurgin ◽  
E. W. Forsythe ◽  
S. I. Kim ◽  
B. S. Sywe ◽  
B. A. Khan ◽  
...  
Keyword(s):  
Systematic Study ◽  
Quantum Confinement ◽  
Emission Spectra ◽  
Emission Peak ◽  
Nanocrystal Size ◽  
Pl Spectra ◽  
Si Nanocrystals ◽  
Average Size ◽  
Size Dispersion ◽  
Confinement Model

ABSTRACTA systematic study of the PL spectra of Si quantum nanocrystals in the SiO2 matrix has been performed. The results have been fitted to a quantum-confinement model that includes the nanocrystal size dispersion rather than a specific size of the nanocrystal. This serves as a strong confirmation of the confinement-induced nature of the PL. It has been shown that if the dispersion is taken into account, the position of the emission peak as well as the PL width can always be correlated with the average size of the nanocrystal.

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