scholarly journals Luminescence, Energy Transfer, and Upconversion Mechanisms of Y2O3Nanomaterials Doped with Eu3+,Tb3+, Tm3+,Er3+, and Yb3+Ions

2007 ◽  
Vol 2007 ◽  
pp. 1-10 ◽  
Author(s):  
TranKim Anh ◽  
Paul Benalloul ◽  
Charles Barthou ◽  
Lam thiKieu Giang ◽  
Nguyen Vu ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Doping Concentration ◽  
Spherical Shape ◽  
X Ray Diffraction ◽  
X Ray ◽  
Decay Times ◽  
Structure Phase ◽  
High Resolution Tem ◽  
Average Size ◽  
20 Nm

Luminescence, energy transfer, and upconversion mechanisms of nanophosphors (Y2O3 : Eu3+,Tb3+,Y2O3 : Tm3+,Y2O3 : Er3+,Yb3+) both in particle and colloidal forms were studied. The structure, phase, and morphology of the nanopowders and nanocolloidal media were determined by high-resolution TEM and X-ray diffraction. It was shown that the obtained nanoparticles have a round-spherical shape with average size in the range of 4 to 20 nm. Energy transfer was observed forY2O3 : Eu3+,Tb3+colloidal and powders, upconversion transitions were observed for bothY2O3 : Er3+andY2O3 : Er3+,Yb3+nanophosphors. The dependence of photoluminescence (PL) spectra and decay times on doping concentration has been investigated. The infrared to visible conversion of emission inY2O3 : Er3+,Yb3+system was analyzed and discussed aiming to be applied in the photonic technology.

Effect of Trace Fe3+ on Luminescent Properties of CaWO4: Pr3+ Phosphors

2016 ◽  
Vol 71 (1) ◽  
pp. 21-25 ◽  
Author(s):  
Ke Wang ◽  
Xu Feng ◽  
Wenlin Feng ◽  
Shasha Shi ◽  
Yao Li ◽  
...  
Keyword(s):  
Doping Concentration ◽  
Luminescent Properties ◽  
Solid State Reaction Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Energy Transfers ◽  
Decay Times ◽  
Lifetime Testing ◽  
Testing Techniques ◽  
The Mean

AbstractFe3+ undoped and doped CaWO4: Pr3+ phosphors have been successfully synthesised by using the solid-state reaction method. The products were characterised by powder X-ray diffraction (XRD), photoluminescence (PL) and fluorescence lifetime testing techniques, respectively. The mean crystallite size (50.7 nm) of CaWO4: Pr3+ is obtained from powder XRD data. PL spectra of both Fe3+ undoped and doped CaWO4: Pr3+ phosphors exhibit excitation peaks at 214, 449, 474, and 487 nm under monitor wavelength at 651 nm, and emission peaks at 532, 558, 605, 621, 651, 691, 712, and 736 nm under blue light (λem=487 nm) excitation. The effect of trace Fe3+ on luminescence properties of CaWO4: Pr3+ phosphor is studied by controlling the doping concentration of Fe3+. The results show that radioactive energy transfers from luminescence centre Pr3+ to quenching centre Fe3+ occurred in Fe3+ doped CaWO4: Pr3+ phosphors. With the increasing concentration of Fe3+, the energy transfer from Pr3+ to Fe3+ is enhanced, and the emission intensity of CaWO4: Pr3+ will be lower. The decay times (5.22 and 4.99 μs) are obtained for typical samples Ca0.995WO4: Pr3+0.005 and Ca0.99275WO4: Pr3+0.005, Fe3+0.00225, respectively. This work shows that nonferrous phosphors can improve the luminescent intensity of the phosphors.

Nanocrystallization of gas atomized Cu47Ti33Zr11Ni8Si1 metallic glass

2006 ◽  
Vol 21 (3) ◽  
pp. 597-607 ◽  
Author(s):  
S. Venkataraman ◽  
S. Scudino ◽  
J. Eckert ◽  
T. Gemming ◽  
C. Mickel ◽  
...  
Keyword(s):  
Metallic Glass ◽  
Primary Crystallization ◽  
Nanocrystalline Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Transmission Electron ◽  
High Resolution Tem ◽  
20 Nm ◽  
Annealing Experiments

Cu47Ti33Zr11Ni8Si1 metallic glass powder was prepared by gas atomization. Decomposition in the amorphous alloy and primary crystallization has been studied by differential scanning calorimetry (DSC), x-ray diffraction (XRD), and transmission electron microscopy (TEM). The glassy powder exhibits a broad DSC exotherm prior to bulk crystallization. Controlled annealing experiments reveal that this exotherm corresponds to a combination of structural relaxation and nanocrystallization. A uniform featureless amorphous contrast is observed in the TEM prior to the detection of nanocrystals of 4–6 nm in size. High-resolution TEM studies indicate that this nanocrystalline phase has a close crystallographic relationship with the γ–CuTi phase having a tetragonal structure. The product of the main crystallization event is also nanocrystalline, hexagonal Cu51Zr14, having dimensions of 20 nm. However, there is no evidence for possible amorphous phase separation prior to the nanocrystallization events.

Effects of Nano-Sized NiF2 Addition in Bi1.4Pb0.6Sr2Ca2Cu3O10+δ Superconductor

2014 ◽  
Vol 895 ◽  
pp. 87-90 ◽  
Author(s):  
Muhammad Hafiz ◽  
Roslan Abd-Shukor
Keyword(s):  
Electron Microscope ◽  
Critical Temperature ◽  
Scanning Electron Microscope ◽  
Electrical Transport ◽  
Diffraction Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Average Size ◽  
20 Nm ◽  
Scanning Electron

The effects of NiF2addition on the superconducting and transport properties of Bi1.4Pb0.6Sr2Ca2Cu3O10+δ(Bi-2223) were studied. Bi-2223 superconductor samples were prepared via conventional nitrate coprecipitation method, and 0.01 wt% - 0.05 wt% of NiF2nanoparticles with average size of 20 nm were added into the samples. The critical temperature (Tc) of each sample was measured by using the four-point probe method. Furthermore, phase formation and the microstructure of the samples were identified using x-ray diffraction method (XRD) and scanning electron microscope (SEM) respectively. The optimumTcwas observed for the sample with 0.04 wt% addition of NiF2. Results of electrical transport measurement are presented.

Synthesis and Characterization of TTAB Coated Silver (Ag) Nanoparticles

2011 ◽  
Vol 264-265 ◽  
pp. 530-534
Author(s):  
M.M. Alam ◽  
M. Harun ◽  
Momtazul Islam
Keyword(s):  
Silver Nanoparticles ◽  
Ag Nanoparticles ◽  
Silver Clusters ◽  
Ammonium Bromide ◽  
X Ray Diffraction ◽  
Preferential Growth ◽  
X Ray ◽  
Average Size ◽  
20 Nm

Silver nanoparticles protected by Tetradecyltrimethyl Ammonium Bromide (TTAB) were prepared in a one-phase electrochemical system. Electrochemical procedure, based on the dissolution of a metallic anode in an appropriate solvent, has been used to get silver nanoparticles. It is possible to get different particle size by changing the current density. The optical properties of the silver Nanoparticles were investigated by UV-Vis and Photoluminescence (PL) Spectroscopy. Absorption peak were found 424 nm which confirm the presence of Ag nanoparticles. The structural properties of the samples were carried out by scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements. XRD confirmed the preferential growth of Ag nanoparticles whose average size is ≈ 20 nm in the <111> orientation as well as purity of silver clusters.

Optical Properties of Si Nanoclusters with Passivated Surfaces

1996 ◽  
Vol 431 ◽  
Author(s):  
L. N. Dinh ◽  
L. L. Chase ◽  
M. Balooch ◽  
W. J. Siekhaus ◽  
F. Wooten
Keyword(s):  
Blue Shift ◽  
Buffer Gas ◽  
X Ray Diffraction ◽  
X Ray ◽  
Synthesis Conditions ◽  
Pl Spectra ◽  
Transmission Electron ◽  
Si Nanocrystals ◽  
Decay Times ◽  
Average Size

AbstractSi nanoclusters with average size of a few nanometers have been synthesized by thermal vaporization of Si in an Ar buffer gas, and passivated with oxygen or atomic hydrogen. High resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) revealed that these nanoclusters were crystalline. All samples showed strong infrared and/or visible photoluminescence (PL) with varying decay times from nanoseconds to microseconds depending on synthesis conditions. Absorption mainly in the Si cores was observed by photoluminescence excitation (PLE) spectroscopy. The visible components of PL spectra were noted to blue shift and broaden as the size of the Si nanocrystals (nc-Si) was reduced, and there were differences in PL spectra for hydrogen and oxygen passivated nc-Si. Our data can be explained best by a model involving absorption between quantum confined states in the Si cores and emission by surface/interface states.

scholarly journals Development of FeOOH nanoarrays using magnetic cations

2013 ◽  
Vol 11 (3) ◽  
pp. 358-363 ◽  
Author(s):  
Perla Garcia-Casillas ◽  
Carlos Martinez-Pérez ◽  
Claudia González ◽  
Héctor Camacho-Montes ◽  
Santos Martel Estrada ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Fourier Transform ◽  
Synthesis Method ◽  
X Ray Diffraction ◽  
Cobalt Ions ◽  
X Ray ◽  
Average Size ◽  
20 Nm ◽  
Scanning Electron

AbstractAbstract In this work, FeOOH arrays were obtained using two different magnetic cations. The nanoparticles were grouped into a package having different orientations through the van der Waals interaction with the magnetic cations. With Fe2+, the FeOOH nanoparticles have a rod shape with a 30-nm diameter and approximately 1-micron length, and are aligned in a star structure. With Co2+, a somatoidal shape was observed, with 20-nm diameter and 150-nm length and a pathway structure to the array. The chemical synthesis method was used to obtain the nanoarrays. The morphology and the average size of the nanorods and nanowires were determined using Field Emission Scanning Electron Microscopy (FESEM). Fourier Transform Infrared Spectroscopy (FTIR) was used to study the interaction between the nanorods and the cobalt ions. The phases of the material were identified using X-ray Diffraction. Graphical abstract

Synthesis of Cobalt Ferrite Nanowires Using FeOOH as a Template

2009 ◽  
Vol 151 ◽  
pp. 245-251 ◽  
Author(s):  
Jose G. Camacho Meza ◽  
Carlos A. Martínez ◽  
Humberto Monreal Romero ◽  
Perla E. García
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Cobalt Ferrite ◽  
X Ray Diffraction ◽  
Cobalt Ions ◽  
X Ray ◽  
The Fourier Transform ◽  
Average Size ◽  
20 Nm ◽  
Scanning Electron

In this work, cobalt ferrite nanowires were chemically synthesized using FeOOH array a template. The FeOOH nanoarray was obtained by the hydrolysis and precipitation of Fe+3, from FeCl3.4 H2O. The cobalt ion (Co+2) was added in order to make it interact with FeOOH nanorods of 20 nm of diameter and 150 nm of length. These nanorods are grouped into packages having different orientations due to the interaction with the cobalt ions. The arrays were calcinated at 700 and 800 °C to obtain cobalt ferrite nanowires with 70 nm of diameter and some micrometers of length. The morphology and the average size of the nanorods and nanowires were determined using Field Emission Scanning Electron Microscopy (FESEM). The Fourier Transform Infrared Spectroscopy (FTIR) was used to study the interaction between the nanorods and the cobalt ions. The phases of the material were identified using X-ray Diffraction.

Controlled Synthesis of Hierarchical Flower-Like CuS Spheres by a Facile Microwave Hydrothermal Method

2012 ◽  
Vol 512-515 ◽  
pp. 265-268 ◽  
Author(s):  
Hui Qi ◽  
Jian Feng Huang ◽  
Li Yun Cao ◽  
Jian Peng Wu
Keyword(s):  
Electron Microscopy ◽  
Cetyltrimethylammonium Bromide ◽  
Controlled Synthesis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Microwave Hydrothermal ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
Average Size ◽  
20 Nm

–Hierarchical flower–like CuS spheres have been synthesized by a facile microwave hydrothermal (MH) method using cetyltrimethylammonium bromide (CTAB) as the surfactant. The as–prepared CuS crystallites under different CTAB contents were characterized by X–ray diffraction (XRD), field–emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). Results show that the CTAB–assisted CuS particles have hierarchical flower–like microstructures that were assembled by thin nanoflakes with thickness of 10~20 nm. The corresponding HRTEM images reveal that these nanoflakes are composed of many nanoparticles with average size of about 7 nm. Moreover, when increasing the CTAB contents from 0 g⁄mL to 0.02 g⁄mL, the as–prepared CuS particles were found to have better dispersion stability with decreased average sizes of the hierarchical flower–like spheres. Comparing with the bulk CuS particles, the related UV–vis absorption spectrum of the as–prepared crystallites exhibits an obvious red shift with the absorption peak at 739 nm.

scholarly journals Investigation and Modeling of the Electrical Conductivity of Graphene Nanoplatelets-Loaded Doped-Polypyrrole

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1034
Author(s):  
Oladipo Folorunso ◽  
Yskandar Hamam ◽  
Rotimi Sadiku ◽  
Suprakas Sinha Ray ◽  
Neeraj Kumar
Keyword(s):  
Electrical Conductivity ◽  
Structural Changes ◽  
Spherical Shape ◽  
Graphene Nanoplatelets ◽  
Conductivity Measurements ◽  
X Ray Diffraction ◽  
X Ray ◽  
Thermogravimetric Analyzer ◽  
Energy Storage Applications ◽  
Electrical Conductivity Data

In this study, a hybrid of graphene nanoplatelets with a polypyrrole having 20 wt.% loading of carbon-black (HGPPy.CB20%), has been fabricated. The thermal stability, structural changes, morphology, and the electrical conductivity of the hybrids were investigated using thermogravimetric analyzer, differential scanning calorimeter, X-ray diffraction analyzer, scanning electron microscope, and laboratory electrical conductivity device. The morphology of the hybrid shows well dispersion of graphene nanoplatelets on the surface of the PPy.CB20% and the transformation of the gravel-like PPy.CB20% shape to compact spherical shape. Moreover, the hybrid’s electrical conductivity measurements showed percolation threshold at 0.15 wt.% of the graphene nanoplatelets content and the curve is non-linear. The electrical conductivity data were analyzed by comparing different existing models (Weber, Clingerman and Taherian). The results show that Taherian and Clingerman models, which consider the aspect ratio, roundness, wettability, filler electrical conductivity, surface interaction, and volume fractions, closely described the experimental data. From these results, it is evident that Taherian and Clingerman models can be modified for better prediction of the hybrids electrical conductivity measurements. In addition, this study shows that graphene nanoplatelets are essential and have a significant influence on the modification of PPy.CB20% for energy storage applications.

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