Optical Absorption Processes in CdSe Nanocrystals Embedded in Silicate Glass and Organic Polymer Matrices Under 7-MeV Electron Irradiation

2008 ◽  
Vol 8 (2) ◽  
pp. 806-811 ◽  
Author(s):  
Yu. M. Azhniuk ◽  
A. V. Gomonnai ◽  
V. V. Lopushansky ◽  
I. G. Megela ◽  
A. E. Raevskaya ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Optical Absorption ◽  
Silicate Glass ◽  
Electron Irradiation ◽  
Polymer Matrices ◽  
Organic Polymer ◽  
Color Centers ◽  
Cdse Nanocrystals ◽  
Deep Traps ◽  
The Matrix

Irradiation-induced bleaching occurs in the spectra of glass-embedded CdSe nanocrystals due to their ionization resulting from charge transfer between them and color centers formed in glass by electron irradiation. No bleaching in the spectra of CdSe nanocrystals encapsulated in gelatine is observed because no deep traps are formed in the matrix under electron irradiation.

Long-Term Stability of Optical Properties of Colloidal CdSe Nanocrystals in Polymer Matrices

2019 ◽  
Vol 18 (03n04) ◽  
pp. 1940052
Author(s):  
Yu. M. Azhniuk ◽  
V. V. Lopushansky ◽  
A. V. Gomonnai ◽  
B. V. Lopushanska ◽  
A. E. Raevskaya ◽  
...  
Keyword(s):  
Optical Properties ◽  
Optical Absorption ◽  
Polyvinyl Alcohol ◽  
Aqueous Solutions ◽  
Polymer Matrices ◽  
Cdse Nanocrystals ◽  
Term Stability ◽  
Long Term Stability ◽  
Mild Conditions

Properties of CdSe nanocrystals (NCs) fabricated in aqueous solutions at relatively mild conditions in the presence of gelatine and stabilized in polymer (gelatine, gelatine + polyvinylpyrrolidone, polyvinyl alcohol) matrices are characterized by Raman, optical absorption and photoluminescence spectroscopies. The effect of heating of the reaction mixture on the average NC size is discussed.

scholarly journals Colloidal CdSe nanocrystals are inherently defective

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Tamar Goldzak ◽  
Alexandra R. McIsaac ◽  
Troy Van Voorhis
Keyword(s):  
Charge Transfer ◽  
Energy Spectrum ◽  
Surface Structure ◽  
Short Range ◽  
Surface Defects ◽  
Low Energy ◽  
Lewis Base ◽  
Cdse Nanocrystals ◽  
Photoinduced Charge Transfer ◽  
Photoinduced Charge

AbstractColloidal CdSe nanocrystals (NCs) have shown promise in applications ranging from LED displays to medical imaging. Their unique photophysics depend sensitively on the presence or absence of surface defects. Using simulations, we show that CdSe NCs are inherently defective; even for stoichiometric NCs with perfect ligand passivation and no vacancies or defects, we still observe that the low energy spectrum is dominated by dark, surface-associated excitations, which are more numerous in larger NCs. Surface structure analysis shows that the majority of these states involve holes that are localized on two-coordinate Se atoms. As chalcogenide atoms are not passivated by any Lewis base ligand, varying the ligand should not dramatically change the number of dark states, which we confirm by simulating three passivation schemes. Our results have significant implications for understanding CdSe NC photophysics, and suggest that photochemistry and short-range photoinduced charge transfer should be much more facile than previously anticipated.

Formation of color centers in a soda-lime silicate glass by excimer laser irradiation

2010 ◽  
Vol 22 (4) ◽  
pp. 045901 ◽  
Author(s):  
Kohei Kadono ◽  
Nobuyuki Itakura ◽  
Tomoko Akai ◽  
Masaru Yamashita ◽  
Tetsuo Yazawa
Keyword(s):  
Laser Irradiation ◽  
Excimer Laser ◽  
Silicate Glass ◽  
Soda Lime ◽  
Color Centers ◽  
Excimer Laser Irradiation ◽  
Soda Lime Silicate Glass

scholarly journals Энергетический спектр и оптическое поглощение эндоэдральных комплексов Er-=SUB=-2-=/SUB=-C-=SUB=-2-=/SUB=-@C-=SUB=-90-=/SUB=- на основе изомеров N 21 и N 44

2021 ◽  
Vol 129 (9) ◽  
pp. 1111
Author(s):  
А.И. Мурзашев ◽  
А.П. Жуманазаров ◽  
М.Ю. Кокурин
Keyword(s):  
Experimental Data ◽  
Charge Transfer ◽  
Optical Absorption ◽  
Absorption Spectra ◽  
Coulomb Interaction ◽  
Energy Spectra ◽  
Optical Absorption Spectra ◽  
Endohedral Complexes

The article simulates the optical absorption spectra (OAS) of endohedral complexes Er2C2 @ C90 based on isomers No. 44 (C2) No. 21 (C1) of fullerene C90. For this purpose, the energy spectra of the indicated isomers have been calculated. The calculation was carried out within the framework of two models. Within the framework of the first model, which is traditional, only hops of π-electrons from site to site were taken into account (the integral of hopping to the nearest sites B ~ -2.6 eV). Within the framework of the second model, developed in a series of our works [1-5], in addition to hopping from site to site (the integral of hopping to the nearest sites B ~ -1.0 eV), the intrasite Coulomb interaction (ICCI) of π-electrons was also taken into account (the integral of the Coulomb interaction U ~ 7.0 eV). Comparison of the OSS curves obtained by us with the experimental data [5] convincingly indicates that the second model adequately describes the OSS of the endohedral Er2C2 @ C90 complexes based on the investigated isomers. The magnitude of charge transfer from the Er2C2 system to the fullerene shell turned out to be -4e.

scholarly journals Локализованные экситоны в спектре оптического поглощения оксида цинка, легированного марганцем

2019 ◽  
Vol 61 (5) ◽  
pp. 817
Author(s):  
В.И. Соколов ◽  
Н.Б. Груздев ◽  
В.А. Важенин ◽  
А.В. Фокин ◽  
А.В. Дружинин
Keyword(s):  
Zinc Oxide ◽  
Charge Transfer ◽  
Absorption Band ◽  
Optical Absorption ◽  
Absorption Spectra ◽  
Polarized Light ◽  
Threshold Energy ◽  
Impurity Absorption ◽  
Charge Transfer Transitions ◽  
Long Time

AbstractThe results of the study of optical absorption and EPR signals of single crystals of zinc oxide doped with manganese are presented. A broad impurity absorption band with the threshold energy about 2.1 eV, which was treated as a result of charge transfer transitions, has been observed for a long time in ZnO : Mn absorption spectra. In absorption spectra of a polarized light at 4.2 and 77.3 K, we first detected several lines of different intensity in a 1.877–1.936 eV range of energies of the light quanta. The observed lines are attributed to a donor exciton [( d ^5 + h ) e ] that emerges as a result of the Coulomb binding a free s electron and a hole, which is localized on p – d hybridized states. The EPR spectra of Mn^2+ ion signals, when corresponding to the impurity absorption band exposed to light, are found to be not photosensitive. The obtained results indicate that the ZnO : Mn impurity absorption is due to transitions from antibonding p – d hybridized DBH states to the conduction band.

Radiation-induced defects in montebrasite: An electron paramagnetic resonance study of O – hole and Ti3+ electron centers

2020 ◽  
Vol 105 (7) ◽  
pp. 1051-1059
Author(s):  
José R. Toledo ◽  
Raphaela de Oliveira ◽  
Lorena N. Dias ◽  
Mário L.C. Chaves ◽  
Joachim Karfunkel ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Electron Irradiation ◽  
Color Centers ◽  
Hydroxyl Groups ◽  
Γ Irradiation ◽  
Paramagnetic Resonance ◽  
Radiation Induced ◽  
Induced Defects ◽  
Electron Paramagnetic ◽  
Hole Centers

Abstract Montebrasite is a lithium aluminum phosphate mineral with the chemical formula LiAlPO4(Fx,OH1–x) and considered a rare gemstone material when exhibiting good crystallinity. In general, montebrasite is colorless, sometimes pale yellow or pale blue. Many minerals that do not have colors contain hydroxyl ions in their crystal structures and can develop color centers after ionization or particle irradiation, examples of which are topaz, quartz, and tourmaline. The color centers in these minerals are often related to O− hole centers, where the color is produced by bound small polarons inducing absorption bands in the near UV to the visible spectral range. In this work, colorless montebrasite specimens from Minas Gerais state, Brazil, were investigated by electron paramagnetic resonance (EPR) for radiation-induced defects and color centers. Although γ irradiation (up to a total dose of 1 MGy) did not visibly modify color, a 10 MeV electron irradiation (80 MGy) induced a pale greenish-blue color. Using EPR, O− hole centers were identified in both γ- or electron-irradiated montebrasite samples showing superhyperfine interactions with two nearly equivalent 27Al nuclei. In addition, two different Ti3+ electron centers were also observed. From the γ irradiation dose dependency and thermal stability experiments, it is concluded that production of O− hole centers is limited by simultaneous creation of Ti3+ electron centers located between two equivalent hydroxyl groups. In contrast, the concentration of O− hole centers can be strongly increased by high-dose electron irradiation independent of the type of Ti3+ electron centers. From detailed analysis of the EPR angular rotation patterns, microscopic models for the O− hole and Ti3+ electron centers are presented, as well as their role in the formation of color centers discussed and compared to other minerals.

scholarly journals Theoretical Insight into the Spectral Characteristics of Fe(II)-Based Complexes for Dye-Sensitized Solar Cells—Part I: Polypyridyl Ancillary Ligands

2011 ◽  
Vol 2011 ◽  
pp. 1-11 ◽  
Author(s):  
Xiaoqing Lu ◽  
Shuxian Wei ◽  
Chi-Man Lawrence Wu ◽  
Ning Ding ◽  
Shaoren Li ◽  
...  
Keyword(s):  
Solar Cells ◽  
Charge Transfer ◽  
Optical Absorption ◽  
Absorption Spectra ◽  
Dye Sensitized Solar Cells ◽  
Optical Absorption Spectra ◽  
Ancillary Ligands ◽  
Dye Sensitized ◽  
Ligand Charge Transfer ◽  
Sensitized Solar Cells

The design of light-absorbent dyes with cheaper, safer, and more sustainable materials is one of the key issues for the future development of dye-sensitized solar cells (DSSCs). We report herein a theoretical investigation on a series of polypyridyl Fe(II)-based complexes of FeL2(SCN)2, [FeL3]2+, [FeL′(SCN)3]-, [FeL′2]2+, and FeL′′(SCN)2(L = 2,2′-bipyridyl-4,4′-dicarboxylic acid, L′ = 2,2′,2″-terpyridyl-4,4′,4″-tricarboxylic acid, L″= 4,4‴-dimethyl-2,2′ : 6′,2″ :6″,2‴-quaterpyridyl-4′,4″-biscarboxylic acid) by density functional theory (DFT) and time-dependent DFT (TD-DFT). Molecular geometries, electronic structures, and optical absorption spectra are predicted in both the gas phase and methyl cyanide (MeCN) solution. Our results show that polypyridyl Fe(II)-based complexes display multitransition characters of Fe → polypyridine metal-to-ligand charge transfer and ligand-to-ligand charge transfer in the range of 350–800 nm. Structural optimizations by choosing different polypyridyl ancillary ligands lead to alterations of the molecular orbital energies, oscillator strength, and spectral response range. Compared with Ru(II) sensitizers, Fe(II)-based complexes show similar characteristics and improving trend of optical absorption spectra along with the introduction of different polypyridyl ancillary ligands.

Formation of Helical Mesopores in Organic Polymer Matrices

2007 ◽  
Vol 129 (13) ◽  
pp. 3788-3789 ◽  
Author(s):  
François-Xavier Simon ◽  
Nawel S. Khelfallah ◽  
Marc Schmutz ◽  
Nancy Díaz ◽  
Philippe J. Mésini
Keyword(s):  
Polymer Matrices ◽  
Organic Polymer
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