scholarly journals Spectroscopic and Structural Properties of β-Tricalcium Phosphates Ca9RE(PO4)7 (RE = Nd, Gd, Dy)

Crystals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1269
Author(s):  
Veronica Paterlini ◽  
Asmaa El Khouri ◽  
Marco Bettinelli ◽  
Daniele Maria Trucchi ◽  
Francesco Capitelli
Keyword(s):  
Emission Spectra ◽  
Structural Disorder ◽  
Light Emitters ◽  
Local Environments ◽  
Powder Samples ◽  
High Concentrations ◽  
Vibrational Features ◽  
Low Symmetry ◽  
Tricalcium Phosphates ◽  
Weak Concentration

Rare-earth-basedCa9RE(PO4)7 (RE = Nd, Gd, Dy) materials were synthesized by solid-state reaction at T = 1200 °C. The obtained tricalcium phosphate (TCP) materials are efficient light emitters due to the presence of RE3+ ions, although these ions are present at high concentrations. Moreover, in these host structures, these ions can be used as optical probes to study their local environments. Thus, photoluminescence (PL) emission spectra of the powder samples clearly indicated, for Dy3+ and Gd3+ ions, the presence of the RE3+ ion in low-symmetry sites with some local structural disorder, and the spectra show the presence of vibrational features (in the case of Gd3+). For the Nd3+ phase, emission bands are present around 900, 1050, and 1330 nm, originating from the 4F3/2 level. In general, these RE-TCP samples are interesting luminescent materials in the visible (Dy), UV (Gd), and NIR (Nd) regions, due to weak concentration quenching even for high concentrations of the emitting ion.

Band-Gap Engineering Based on Ti@ZnO Nanocolloids: Tunable Optical Properties

2014 ◽  
Vol 617 ◽  
pp. 161-165
Author(s):  
Chrystelle Neaime ◽  
Fabien Grasset ◽  
Tangi Aubert
Keyword(s):  
Thin Films ◽  
Band Gap ◽  
Uv Light ◽  
Sol Gel ◽  
Wide Band ◽  
Colloidal Solutions ◽  
Light Emitters ◽  
Wide Range ◽  
High Concentrations ◽  
Acoustic Wave Devices

One of the largest application areas of sol-gel chemistry is thin-film preparation. Using this approach, we started to synthesize M@ZnO colloidal solutions for the preparation of functional thin films. ZnO is a wide band-gap (3.37 eV) semiconductor with large exciton binding energy. In the bulk or in nanosized form, it could be used in a wide range of applications such as UV light emitters, spin functional devices, gas sensors, transparent electronics or surface acoustic wave devices. Since recently, the preparation of innovative functional M@ZnO materials by doping or functionalizing nanocolloids constitutes a new challenge. Using high concentrations of the different Ti@ZnO nanocolloids, we were able to prepare various functional colloidal solutions with tunable emission and thin films, such as red-luminescent Eu3+@ZnTiO3 or versatile ZnTiON colored nanomaterials.

Structural and Luminescence Properties of Eu3+ and Dy3+ Doped Magnesium Tellurite Borophosphate Ceramic

2015 ◽  
Vol 1107 ◽  
pp. 53-58
Author(s):  
Siti Maisarah Aziz ◽  
Rosli Hussin ◽  
N.M. Yusoff
Keyword(s):  
Solid State ◽  
Emission Spectra ◽  
Solid State Reaction Method ◽  
Luminescence Properties ◽  
Functional Material ◽  
X Ray Diffraction ◽  
Co Doping ◽  
Powder Samples ◽  
Diffraction Patterns ◽  
Co Doped

Lately, researchers have been considering the miscellaneous in the borophosphate crystalline’s luminescence as one of the important properties in hunt of the new functional material. In this study we discus the structural and luminescence properties of Eu3+/Dy3+ co-doped borophosphate ceramic. A series of ceramic samples based on B2O3-(65-)P2O5-25MgO-10TeO2 where (065) mol has successfully been prepared using solid state reaction method and sintered at 900°C. The crystalline phase of the powder samples was characterized using X-ray diffraction pattern. The diffraction patterns analysis indicated that the prepared samples were polycrystalline phase of B(PO4), Mg(PO3)2and Mg(BO3)(PO4). The local structure network structure has been investigated using Infrared Spectroscopy using KBr method. The FT-Infrared spectra reveal the presence of B-O-B vibrations, BO3 and BO4 bridging oxygen and P-O stretching modes of P-O-P, P=O and PO4 unit in the ceramics sample. Meanwhile, the luminescence properties of doped sample were measured based on analysis of emission spectra of photoluminescence spectroscopy. The emission peaks of Eu3+ doped sample were located at 593 nm, 613 nm, 652 nm, 685 nm due to the assigned transition 5D0-7FJ( J = 1, 2, 3, 4 ). The Dy3+ emission is due to 4F9/2 -5H15/2 and 4F9/2-6H13/2 transition. For Eu3+/Dy3+ co-doped sample consists of peaks belonging to the 4F9/2-6H15/2 (482 nm) and 4F9/2-6H13/2 (573 nm) transition while red emission 5D0-7F2 transitions appears at 611 nm. Improvement in the optical properties due to co-doping may be useful to discover a new highly efficient luminescent material that are very useful in optical devices and solid-state lighting.

Local and Electronic Structure of Siloxene

1999 ◽  
Vol 14 (4) ◽  
pp. 1235-1237 ◽  
Author(s):  
Ernst Z. Kurmaev ◽  
Sergei N. Shamin ◽  
David L. Ederer ◽  
Ursula Dettlaff-Weglikowska ◽  
Jörg Weber
Keyword(s):  
Electronic Structure ◽  
Infrared Absorption ◽  
Emission Spectra ◽  
Close Similarity ◽  
X Ray ◽  
Powder Samples ◽  
Absorption Measurements ◽  
Good Agreement ◽  
Oxygen Atoms

Silicon L2,3 x-ray emission spectra (XES) of siloxene powder samples prepared according to Wöohler and Kautsky (Wöhler and Kautsky siloxene) are presented. The results are compared with the Si L2,3 spectra of the reference compounds a-Si, c-Si, SiO2, and SiOx. A close similarity of the electronic structure of Wöhler siloxene to that of a-SiO0.43: H and of Kautsky siloxene to that of a-SiO0.87: H is found. We determine the number of oxygen atoms per Si atom at ~0.5 in Wöhler siloxene and ~0.8 in Kautsky siloxene. The relative concentrations are in good agreement with the results of infrared absorption measurements on the same samples.

scholarly journals Fluorescent Silica Hybrid Film-Forming Materials Based on Salicylaldazine

Coatings ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1255
Author(s):  
Alina Raditoiu ◽  
Valentin Raditoiu ◽  
Florentina Monica Raduly ◽  
Georgiana Cornelia Ispas ◽  
Violeta Purcar ◽  
...  
Keyword(s):  
Photophysical Properties ◽  
Sol Gel ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Hybrid Films ◽  
Fluorescence Emission Spectra ◽  
Network Modifier ◽  
Local Environments ◽  
Film Forming ◽  
Silica Sols

Fluorescent film-forming materials were obtained by embedding salicylaldazine (SAA) in silica hybrids generated by sol–gel processes from different silane precursors in acid catalysis. Tuned local environments for the fluorophore were generated in the hosting network by modifying silica sols with organic groups through the co-condensation of tetraethylortosilicate (TEOS) and different alkoxysilanes hydrolysis products. The photophysical properties of the luminescent hybrid films were studied in direct relationship with structural, textural, and surface properties and based on interactions between SAA species and the silica hosting network. Film-forming materials were studied in order to determine differences in absorption and fluorescence emission due to the environments around the fluorophore. The variations recorded in the fluorescence emission spectra of the hybrid films were related to interactions established between the fluorophore species and their sterically hindered surroundings of the host hybrid silica, where free molecular motions are restricted. The influence of the type and amount of network modifier and of the fluorophore loading on the transparency of the films and fluorescence intensity was also investigated. The study carried out led to the elucidation of the necessary conditions for obtaining luminescent film-forming materials with high luminescence intensity and transparency useful for the design of new light concentrators.

Electroluminescence in Chalcogenide Nanocrystals and Nanocomposites

2014 ◽  
Vol 357 ◽  
pp. 127-169 ◽  
Author(s):  
Meera Ramrakhiani ◽  
Nitendra Kumar Gautam ◽  
Kamal Kushwaha ◽  
Sakshi Sahare ◽  
Pranav Singh
Keyword(s):  
Threshold Voltage ◽  
Light Emission ◽  
Emission Spectra ◽  
Nanocrystalline Powder ◽  
Research Groups ◽  
Size Quantization ◽  
Chemical Route ◽  
Quantization Effect ◽  
Powder Samples ◽  
Znse Nanocrystals

Several research groups have reported that nanocrystalline II-VI semiconductors show enhanced luminescence, increased oscillator strength and shorter response time. Nanocrystalline powder samples of CdS, CdSe, ZnS and ZnSe nanocrystals and their composites with PVA and PVK have been prepared by chemical route. SEM. TEM and AFM images indicate agglomeration of particles. XRD reveal the crystal structure and size in nanometer range and absorption spectra show increased band gap due to quantum confinement.The EL studies on nanocrystalline powder samples and nanocrystal/polymer composites have shown that the light emission starts at certain threshold voltage, different for different specimens and then increases with increasing voltage. It is found that smaller nanocrystals have lower threshold voltage and higher EL brightness. It is observed that nanocomposite give much higher electroluminescence starting at lower voltage and increasing very fast with the voltage as compared to nanocrystalline powder. The emission spectra are found to depend on the material, crystalline size and doping. Electroluminescence in undoped and doped chalcogenide nanocrystals and nanocomposites is reviewed in this paper. In nanosize regime, electroluminescence (EL) is governed by the size quantization effect. Contents of Paper

Fluorescence Lifetime Studies of Crude Oils

1994 ◽  
Vol 48 (8) ◽  
pp. 977-984 ◽  
Author(s):  
Xin Wang ◽  
Oliver C. Mullins
Keyword(s):  
Energy Transfer ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Quantum Yields ◽  
Crude Oils ◽  
Fluorescence Lifetimes ◽  
Concentration Effects ◽  
Fluorescence Emission Spectra ◽  
High Concentrations ◽  
Lifetime Studies

The fluorescence lifetimes of a series of crude oils at various concentrations have been measured for UV-visible excitation and emission wavelengths. The lifetime results are compared with fluorescence spectra and quantum yields for these solutions. The concentration effects of energy transfer and quenching are large and result in a significant decrease in fluorescence lifetimes for high concentrations and for heavy crude oils. Thus, radiationless processes dominate in energy transfer. At high concentrations, energy transfer produces large red shifts in fluorescence emission spectra, while quenching produces a large reduction in quantum yields. Stern-Volmer analyses of lifetime and quenching data show a linear dependence of energy transfer and quenching rates on concentration. The rate constants are consistent with collisions which are very efficient at energy transfer and quenching, and the rates of these two processes are comparable.

scholarly journals Effects of ionic strength on the catalysis and stability of prolyl oligopeptidase

1995 ◽  
Vol 312 (1) ◽  
pp. 267-271 ◽  
Author(s):  
L Polgár
Keyword(s):  
Ionic Strength ◽  
Fluorescence Emission ◽  
Water Structure ◽  
Emission Spectra ◽  
Heat Denaturation ◽  
Prolyl Oligopeptidase ◽  
Fluorescence Emission Spectra ◽  
Water Shell ◽  
Serine Protease Family ◽  
High Concentrations

Prolyl oligopeptidase is the prototype of a new serine protease family, unrelated to trypsin and subtilisin. In contrast with these proteases, prolyl oligopeptidase is remarkably sensitive to ionic strength, being more active in the presence of high concentrations of salt. The enzyme has two catalytic forms, which interconvert with changing pH. To reveal the structural bases of these phenomena, the effects of 0.5 M NaCl on the stability of the enzyme were investigated by studying its denaturation as a function of pH, temperature, and urea concentration. The three independent methods have unequivocally demonstrated that denaturation of the enzyme is promoted in the presence of NaCl. Furthermore, destabilization of the low-pH form by urea is more significant than that of the high-pH form. Examination of the fluorescence emission spectra of various denatured forms indicates that the enzyme is not fully unfolded in 8 M urea, nor at acidic pH. The tryptophan residues in the acid-denatured state are mainly buried. The results are interpreted in terms of the decay of the protective water shell at the higher ionic strength. The higher enthalpy and entropy of activation for heat denaturation provide further evidence that a more ordered water structure stabilizes the protein in the absence of salt. The biphasic kinetics obtained with denaturation by heat and urea suggest that the enzyme has two domains of different stabilities.

Emission of Precipitation Deposited PbS Quantum Dots on Polyethylene Terephthalate

2013 ◽  
Vol 1436 ◽  
Author(s):  
Bruno Ullrich ◽  
Andrew R. Markelonis ◽  
Joanna S. Wang ◽  
Gail J. Brown
Keyword(s):  
Quantum Dots ◽  
Fourier Transform ◽  
Emission Spectrum ◽  
Polyethylene Terephthalate ◽  
Emission Spectra ◽  
Cryogenic Temperatures ◽  
Light Emitters ◽  
Double Frequency ◽  
Organic Matrices ◽  
Pbs Quantum Dots

ABSTRACTCentrifuge enforced precipitation was used to disperse PbS quantum dots (diameter 4.7 nm) on polyethylene terephthalate. By employing double frequency Fourier transform spectroscopy, we studied the emission properties of the sample. Gaussian shaped emission spectra from cryogenic temperatures up to room temperatures were observed, demonstrating the potential of PbS quantum dots to be used as light emitters in combination with organic matrices. One interesting feature is that the linewidth of the emission spectrum does not follow the expected thermal broadening.

MCD spectroscopy and TD-DFT calculations of low-symmetry acenaphthoporphyrins with dual fluorescence

2013 ◽  
Vol 17 (10) ◽  
pp. 996-1007 ◽  
Author(s):  
John Mack ◽  
Jun Nakamura ◽  
Tetsuo Okujima ◽  
Hiroko Yamada ◽  
Hidemitsu Uno ◽  
...  
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
Dft Calculations ◽  
Magnetic Circular Dichroism ◽  
Emission Spectra ◽  
Dual Fluorescence ◽  
Band Region ◽  
Td Dft ◽  
Sign Sequence ◽  
Low Symmetry

Magnetic circular dichroism (MCD) spectroscopy and TD-DFT calculations are used to analyze the electronic structure and optical properties of low-symmetry acenaphthoporphyrins with AAAB, ABAB and AABB structures. Evidence for dual fluorescence caused by tautomerism has been identified in the emission spectra of the AAAB and ABAB compounds. The sign sequences observed for the Q and B bands in the MCD spectra have been used to validate the results of the TD-DFT calculations. An anomalous +/- sign sequence is observed in the B band region with ascending energy similar to that reported previously for metal tetraphenyltetraacenaphthoporphyrin complexes.

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