scholarly journals Optical Transitions from Hexavalent Chromium in Lithium-Borate Glasses

2021 ◽  
Author(s):  
Dhia-Aldin Slibi ◽  
Moukhtar Hassan ◽  
Zakaria M. Abd El-Fattah ◽  
M. Atallah ◽  
M. A. El-Sherbiny ◽  
...  
Keyword(s):  
Optical Band Gap ◽  
Oxidation States ◽  
Resonance Spectroscopy ◽  
Borate Glasses ◽  
Optical Transitions ◽  
Melt Quenching ◽  
Glass Color ◽  
Spin Resonance ◽  
Optical Applications ◽  
Cr Doping

Abstract The melt-quenching technique was used to prepare a series of chromium-doped borate glasses with the composition xCr2O3 - (70-x) B2O3- 30 Li2O- (x = 0, 0.1, 0.2, 0.3 and 0.5 mol %). The low-doping level here employed allowed to unambiguously identify well-defined near-edge Cr6+ optical transitions, and to precisely determine the optical band gap of the borate glass host. Additional Cr3+ transitions were observed in the visible regime, rendering a strong modulation of the glass color, from colorless to dark greenish, with Cr content. Both Cr6+(after the charge transfer transformation into Cr5+) and Cr3+oxidation states and their variations with Cr doping were identified from electron spin resonance spectroscopy. All samples exhibit similar vibrational spectra dominated by BO3 and BO4 structural units, with the development of weak Cr6+ vibration with Cr doping. The present study provides structurally similar but optically active and tunable glass hosts suitable for various optical applications.

Upconversion Luminescence and Optical Studies of Nd3+ in Bismuth Borate Glasses

2013 ◽  
Vol 770 ◽  
pp. 153-156
Author(s):  
Onanong Chamlek ◽  
Pruittipol Limkitjaroenporn ◽  
Hong Joo Kim ◽  
Jakrapong Kaewkhao
Keyword(s):  
Energy Level ◽  
Band Gap ◽  
Glass Matrix ◽  
Optical Band Gap ◽  
Upconversion Luminescence ◽  
Emission Spectra ◽  
Borate Glasses ◽  
Optical Studies ◽  
Melt Quenching ◽  
Bismuth Borate

Neonymium doped bismuth borate glasses with composition 50Bi2O3 : (50-x)B2O3: xNd2O3 (where x = 0.5, 1.0, 1.5, 2.0 and 2.5 mol%) have been prepared by melt quenching technique. The optical and upconversion luminescence properties of glasses were investigated. The nine absorption peaks were observed, correspond with Nd3+ energy level in glass. The optical band gap decreased with increasing Nd2O3 concentration due to the increase of non-bridging oxygen (NBOs) in glass matrix. The upconversion luminescence emission spectra shows peak at 393 nm, assign to 4D3/24I11/2 transition.

scholarly journals Precise Determination of Optical Band Gap in Cr-Doped Semiconductor Nanowires

2021 ◽  
Author(s):  
N. S. Anad ◽  
Zakaria M Abd El-Fattah ◽  
M. Attallah ◽  
Hanaa M. Ahmed ◽  
Mohammed M. El-Okr ◽  
...  
Keyword(s):  
Band Gap ◽  
Absorption Edge ◽  
Optical Band Gap ◽  
Precise Determination ◽  
Precipitation Method ◽  
Structure Characteristic ◽  
Optical Transitions ◽  
Optical Resonance ◽  
Co Precipitation ◽  
Cr Doping

Abstract Pristine and chromium-doped ZnO nanowires were prepared following the traditional co-precipitation method. X-ray diffraction data identified a pure wurtzite hexagonal crystal structure characteristic for ZnO, irrespective of the doping level. The particle size, as deduced form Williamson–Hall plots, was found to be 45-55 nm for all samples. Scanning electron microscopy revealed a clear nanowires morphology for the pure and doped samples, while elemental analysis ensured the successful Cr-doping. Distinct spectroscopic signatures of Cr-doping were revealed from a detailed deconvolution process applied to optical spectra of doped samples, where Cr 3+ optical transitions were unambiguously identified at ~420 and ~665 nm. Particularly relevant, is the spectral decomposition here performed for the superimposed absorption edge (~385 nm) and Cr 3+ optical resonance at ~420 nm, allowing to claim practically doping-independent optical band gap behavior in the present doping regime. This is further supported by identifying the characteristic ZnO near edge photoluminescence peak (~ 392 nm) which maintains fixed wavelength after Cr-doping. These findings contrast earlier studies on Cr-doped semiconductor nanoparticles and glass systems where the optical band gap has been largely underestimated. We attribute the inconsistence band gap values reported in literature for Cr-doped semiconductors to the proximity of Cr optical transitions to the semiconductor absorption edge.

Effect of BaO on physical, optical and structural characteristics of ZnO– Al2O3–B2O3 glasses

2015 ◽  
Vol 11 (3) ◽  
pp. 3190-3197
Author(s):  
H. A. Saudi
Keyword(s):  
Optical Band Gap ◽  
Structural Characteristics ◽  
Band Gap Energy ◽  
Borate Glasses ◽  
Barium Borate ◽  
Melt Quenching ◽  
Structural Units ◽  
Gap Energy ◽  
Ir Studies ◽  
Absorption Studies

Zinc barium borate glasses with composition (65-x) B2O3-10Na2O-10Al2O3-10ZnO-5Li2O-xBaO with (0 ≤ x ≤40 % mol)have been prepared using melt quenching technique.The density, molar volume and the optical absorption studies revealed that the optical band gap energy (Eopt) and Urbachenergy increase with the increase of BaOcontent.This is mainly due to the increased polarization of theBa2+ ions and theenhanced formation of non-bridging oxygen (NBO). The IR studies indicate that these glasses are made up of [AlO6],[BO3],[BO4], and [AlO4] basic structural units.

Physical and Optical Properties of Ce3+ Doped in Bismuth Borate Glass

2013 ◽  
Vol 770 ◽  
pp. 254-257 ◽  
Author(s):  
Kitipun Boonin ◽  
Onanong Chamlek ◽  
Pruittipol Limkitjaroenporn ◽  
Hong Joo Kim ◽  
Jakrapong Kaewkhao
Keyword(s):  
Optical Properties ◽  
Absorption Spectra ◽  
Borate Glass ◽  
Optical Band Gap ◽  
Composition Range ◽  
Borate Glasses ◽  
Melt Quenching ◽  
Bismuth Borate ◽  
Bismuth Borate Glass ◽  
No Absorption

Bismuth borate glasses doped with cerium in the composition 50Bi2O3:(50-x)B2O3:xCeF3 were prepared for the composition range 0x2.5 (in mol%). The glass samples have been fabricated by the conventional melt quenching technique. The physical and optical properties of glass samples were investigated. The optical absorption spectra of the glasses have been measured in the wavelength range 190-1100 nm and no absorption peak was obtained in this region. The absorption spectra of all samples were shifted to longer wavelength with increasing of CeF3 concentrations. Optical band gap decreased and refractive index increased with increasing of CeF3 concentrations.

Effect of Addition TiO2 on Bi2O3-TiO2-B2O3 Glasses

2013 ◽  
Vol 770 ◽  
pp. 72-75 ◽  
Author(s):  
Keerati Kirdsiri ◽  
Nattapon Srisittipokakun ◽  
Yotsakit Ruangtaweep ◽  
Kitipun Boonin ◽  
Pichet Limsuwan ◽  
...  
Keyword(s):  
Band Gap ◽  
Molar Volume ◽  
Optical Band Gap ◽  
Measurement Techniques ◽  
Spectroscopic Properties ◽  
Borate Glasses ◽  
Visible Spectroscopy ◽  
Melt Quenching ◽  
Bismuth Borate ◽  
Uv Visible

Bismuth titanium borate glasses in compositions xTiO2 : (30-x)Bi2O3 : 70B2O3 (with x is in mol%, varying from 0% to 10%) were fabricated by the conventional melt quenching technique. The effect of TiO2 on the physical and spectroscopic properties of bismuth borate glasses have been carried out by means of density and UV-Visible spectroscopy measurement techniques. The density and molar volume of all glasses are found to change depend on TiO2 substitution. The fundamental absorption edges for all glasses have been identified using the theory proposed by Davis and Mott. The optical band gap (Eg) is found to decrease with increase in TiO2 content.

scholarly journals Multiple Optical Features In Binary-Transition-Metal Borate Glasses

2021 ◽  
Author(s):  
Moukhtar A. Hassan ◽  
M. A. Ashoush ◽  
F. M. Ebrahim ◽  
M. M. EL Hady ◽  
F. Ahmad ◽  
...  
Keyword(s):  
Transition Metal ◽  
Borate Glasses ◽  
Optical Transitions ◽  
Structural Modifications ◽  
Spin Resonance ◽  
Infrared Spectral ◽  
Opposite Behavior ◽  
Racah Parameters ◽  
Cr Concentration ◽  
Metal Borate

Abstract Glasses doped with transition metal (TM) ions exhibit rich optical transitions spanning the entire ultraviolet, visible, and infrared spectral regimes. Here we utilize the melt-quenching techniques to synthesis binary-TM-doped borate glasses of composition xCuO-(75-x)B2O3-24.7Li2O-0.3Cr2O3, with x = 0, 0.2, 1.0 and 2.0 mol %. We identify several optical transitions from Cr3+, Cr6+, and Cu2+ ions, the latter manifests at longer wavelengths and gains higher intensity with Cu additives. Despite Cr concentration being fixed, the Cr6+ peaks are quenched and Cr3+ signals are barely attenuated. This behavior rules out possible phase separation and suggests non-trivial interplay between the two TM ions and ligand, as supported by probing their oxidation states from electron spin resonance. The crystal field and Racah parameters followed an opposite behavior, while the optical band gap is reduced upon doping. These changes are correlated with structural modifications introduced by Cu additives, where we anticipate homogenous and preferential proximity of Cu-Cr ions within the network.

scholarly journals Tuning flavin environment to detect and control light-induced conformational switching in Drosophila cryptochrome

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Siddarth Chandrasekaran ◽  
Connor M. Schneps ◽  
Robert Dunleavy ◽  
Changfan Lin ◽  
Cristina C. DeOliveira ◽  
...  
Keyword(s):  
Side Reactions ◽  
Resonance Spectroscopy ◽  
Conformational Switching ◽  
Spin Resonance ◽  
Degradation Activity ◽  
Recognition Motifs ◽  
Cellular Turnover ◽  
Control Light ◽  
Dynamics Simulations ◽  
And Control

AbstractLight-induction of an anionic semiquinone (SQ) flavin radical in Drosophila cryptochrome (dCRY) alters the dCRY conformation to promote binding and degradation of the circadian clock protein Timeless (TIM). Specific peptide ligation with sortase A attaches a nitroxide spin-probe to the dCRY C-terminal tail (CTT) while avoiding deleterious side reactions. Pulse dipolar electron-spin resonance spectroscopy from the CTT nitroxide to the SQ shows that flavin photoreduction shifts the CTT ~1 nm and increases its motion, without causing full displacement from the protein. dCRY engineered to form the neutral SQ serves as a dark-state proxy to reveal that the CTT remains docked when the flavin ring is reduced but uncharged. Substitutions of flavin-proximal His378 promote CTT undocking in the dark or diminish undocking in the light, consistent with molecular dynamics simulations and TIM degradation activity. The His378 variants inform on recognition motifs for dCRY cellular turnover and strategies for developing optogenetic tools.

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