scholarly journals Pinned Luminescence Emission and Absorbance Band from Ultrasmall Ball-Milled Cd0.3Zn0.7Se Nanocrystals

2017 ◽  
Vol 2017 ◽  
pp. 1-6
Author(s):  
Ibrahim Bagudo Muh’d ◽  
Zainal A. Talib ◽  
Zulkarnain Zainal ◽  
Josephine Ying Chi Liew
Keyword(s):  
Size Distribution ◽  
Surface States ◽  
Emission Spectra ◽  
Particle Sizes ◽  
Photoluminescence Intensity ◽  
Single Population ◽  
Transmission Electron ◽  
Distribution Shifts ◽  
Ultrasmall Particles ◽  
Absorbance Band

We report the pinned absorbance and emission spectra of Cd0.3Zn0.7Se nanocrystals synthesized via mechanical alloying. The first emission peaks of Cd0.3Zn0.7Se nanocrystals milled for 5 and 10 h are observed at 3.36 eV, while the absorbance spectra of those milled for 10 and 20 h are observed at 4.47 eV. The emission peaks of nanocrystals milled for 5, 10, and 20 h have broad emissions centered at 2.90, 2.88, and 2.92 eV, respectively. Transmission electron microscopy histogram shows that each nanocrystal size distribution has a single population maxima of <2 nm. In addition, the center of each size distribution shifts toward the ultrasmall particles upon continuous milling. Particle sizes (d) of 0.73 nm are calculated from the first excitonic peaks of the pinned absorbance bands through the semiempirical sizing equation. The continuous reduction in particle sizes increases the surface-to-volume ratios of the nanocrystals. This increase eventually results in an increase in the surface states that translate into low photoluminescence intensity of pinned emission.

Evolution of pyrophyllite particle sizes during dry grinding

Clay Minerals ◽  
2000 ◽  
Vol 35 (2) ◽  
pp. 423-432 ◽  
Author(s):  
P. Uhlík ◽  
V. Šucha ◽  
D. D. Eberl ◽  
L'. Puškelová ◽  
M. Čaplovičová
Keyword(s):  
Size Distribution ◽  
Thickness Distribution ◽  
Particle Sizes ◽  
Transmission Electron ◽  
Lognormal Size Distribution ◽  
Dry Grinding ◽  
Time And Energy ◽  
Grinding Time ◽  
Crystallite Thickness ◽  
Number Of Particles

AbstractThe Bertaut-Warren-Averbach (BWA) technique and high-resolution transmission electron microscopy (HRTEM) were used to characterize the products of dry-ground pyrophyllite. Mean crystallite thickness and crystallite thickness distributions were measured for each sample using the BWA technique. Mean crystallite thickness decreases during the treatment with respect to grinding time and energy applied per unit mass. The BWA data were checked by HRTEM measurements and good fits were obtained for samples having small mean particle thicknesses. Samples with thicker particles could not be measured properly by HRTEM because the number of particles counted from images is statistically insufficient. The shape of the crystallite and the particle-size distribution were used to determine the mechanism of pyrophyllite particle degradation. Particles initially having a lognormal size distribution are first delaminated randomly, then some are delaminated preferentially, thereby producing polymodal thickness distributions. Finally all particles undergo delamination yielding a lognormal thickness distribution.

scholarly journals Influence of Bi3+ content on photoluminescence of InNbO4:Eu3+,Bi3+ for white light-emitting diodes

2017 ◽  
Vol 35 (2) ◽  
pp. 435-439 ◽  
Author(s):  
An Tang ◽  
Liduo Gu ◽  
Fengxiang Shao ◽  
Xidong Liu ◽  
Yongtao Zhao ◽  
...  
Keyword(s):  
Size Distribution ◽  
White Light ◽  
Light Emitting Diodes ◽  
Emission Spectra ◽  
Photoluminescence Intensity ◽  
Excitation Spectra ◽  
Light Emitting ◽  
Co Doping ◽  
Molecular Fluorescence ◽  
White Light Emitting Diodes

Abstract A series of red-emitting phosphors InNbO4:Eu3+,Bi3+ was prepared by a high temperature solid-state reaction. The structure, size distribution and luminescence properties of the phosphors were respectively characterized by X-ray diffraction (XRD), laser particle size and molecular fluorescence spectrometer. The XRD results indicate that the phase-pure samples have been obtained and the crystal structure of the host has not changed under the Eu3+ and Bi3+ co-doping. The test of size distribution shows that the phosphor has a normal size distribution. The excitation spectra illustrate that the dominant sharp peaks are located at 394 nm (7F0→5L6) and 466 nm (7F0→5D2). Meanwhile, the emission spectra reveal that the phosphors excited by the wavelength of 394 nm or 466 nm have an intense red-emission line at 612 nm owing to the 5D0→7F2 transition of Eu3+. Bi3+ doping has not changed the peak positions except the photoluminescence intensity. The emission intensity is related to Bi3+ concentration, and it is up to the maximum when the Bi3+-doping concentration is 4 mol%. Due to good photoluminescence properties of the phosphor, the InNbO4:0.04Eu3+,0.04Bi3+ may be used as a red component for white light-emitting diodes.

EFFECT OF STRONTIUM DOPING ON NANOSTRUCTURE AND CHROMATICITY OF Y2O3:Eu COMPOUNDS

2011 ◽  
Vol 25 (22) ◽  
pp. 2949-2956 ◽  
Author(s):  
ALI MOHAMMADI ◽  
YADOLAH GANJKHANLOU ◽  
MAHMOOD KAZEMZAD ◽  
ABDOLMAJID BAYANDORI MOGHADDAM ◽  
FEREIDOUN ALIKHANI HESSARI ◽  
...  
Keyword(s):  
Emission Spectra ◽  
Photo Luminescence ◽  
Combustion Method ◽  
Urea Solution ◽  
Photoluminescence Intensity ◽  
X Ray Diffraction ◽  
Solution Combustion ◽  
Solution Combustion Method ◽  
X Ray ◽  
Transmission Electron

In this work, various nano-sized samples of Y 2 O 3, Y 2 O 3 :Eu and Y 2 O 3 :Eu , Sr were prepared by urea solution combustion method. Then the resultant nanopowders were investigated by means of X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR) and photo-luminescence emission spectra. Furthermore, the CIE color coordinate of samples were calculated from photoluminescence emission spectra. Results showed that by doping of strontium, the photoluminescence intensity and chromaticity of Y 2 O 3: Eu phosphor was enhanced while crystallite size was decreased.

Study of the Luminescence of Eu-Doped Nanocrystalline Si/SiO2 Systems Prepared by RF Co-Sputtering

1999 ◽  
Vol 581 ◽  
Author(s):  
G.A. Nery ◽  
A. Mahfoud ◽  
L.F. Fonseca ◽  
H. Liu ◽  
O. Resto ◽  
...  
Keyword(s):  
Particle Size ◽  
Size Distribution ◽  
Particle Sizes ◽  
Photoluminescence Intensity ◽  
Unanswered Question ◽  
Si Nanoparticle ◽  
Si Nanoparticles ◽  
Annealing Effects ◽  
The Eu ◽  
Nanocrystalline Si

ABSTRACTWe prepared Eu-doped films of Si nanoparticles embedded in SiO2 using pellets of Eu2O3 by sputtering. We studied their photoemission, transmission and fluorescence to obtain data about their composition and particle size and the Eu interaction characteristics. We were able to incorporate Eu(III) into the Si nanoparticle / SiO2 host. We also found we obtained Eu(II) in the process. We found a lowering of photoluminescence intensity with lowering of temperature. An as yet unanswered question is the reason for the intense whitish luminescence found in some regions of the samples. Some involvement with Eu(II) is suspected. Eu(IIl) related peaks were only observed where the size distribution peak of the nanoparticles was lower than 1.3nm. Whitish luminescence was related to peak sizes ranging from 1.1nm to 1.4nm. Annealing the samples had clear effects upon their photoluminescence, but did not necessarily involve changes in particle sizes, nor were these size changes necessary to increase luminescence. The Eu doping has a tendency to halt the annealing effects on size and, when changes did occur, the particles generally became smaller.

A High Resolution Study of Alumina Supported Iridium Catalysts

1980 ◽  
Vol 38 ◽  
pp. 202-203
Author(s):  
C. Stoeckert ◽  
B. Etherton ◽  
M. Beer ◽  
J. Gryder
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Metal Particles ◽  
Optical Transfer Function ◽  
Particle Sizes ◽  
Iridium Catalysts ◽  
Transmission Electron ◽  
Optical Transfer ◽  
Conventional Transmission Electron Microscope ◽  
Resolution Study

The interpretation of the activity of catalysts requires information about the sizes of the metal particles, since this has implications for the number of surface atoms available for reaction. To determine the particle dimensions we used a high resolution STEM1. Such an instrument with its simple optical transfer function is far more suitable than a conventional transmission electron microscope for the establishment of particle sizes. We report here our study on the size and number distribution of Ir particles supported on Al2O3 and also examine simple geometric models for the shape of Ir particles.

A Cross-Method Comparison of Sub-10 nm Nanoparticle Size Distribution

2019 ◽  
Author(s):  
Ye Yang ◽  
Suiyang Liao ◽  
Zhi Luo ◽  
Runzhang Qi ◽  
Niamh Mac Fhionnlaoich ◽  
...  
Keyword(s):  
Size Distribution ◽  
Analytical Ultracentrifugation ◽  
Statistical Significance ◽  
Method Comparison ◽  
Size Determination ◽  
Size Dependent ◽  
X Ray Scattering ◽  
Transmission Electron ◽  
Gold Nps ◽  
Reliable Representation

Accurate nanoparticle (NP) size determination is essential across research domains, with many functions in nanoscience and biomedical research being size-dependent. Although transmission electron microscopy (TEM) is capable of resolving a single NP down to the sub-nm scale, the reliable representation of entire populations is plagued by challenges in providing statistical significance, predominantly due to limited sample counts, suboptimal preparation procedures and operator bias during image acquisition and analysis. Meanwhile alternative techniques exist, but reliable implementation requires a detailed understanding of appendant limitations. Herein, conventional TEM is compared to the size determination of sub-10 nm gold NPs in solution by small-angle X-ray scattering and analytical ultracentrifugation. Form-free Monte Carlo fitting of scattering profiles offers access to a direct representation of the core size distribution while ultracentrifugation sedimentation velocity analysis provides information of the hydrodynamic size distribution. We report a comparison of these three methods in determining the size of quasi-monodisperse, polydisperse and bimodal gold nanoparticles of 2 – 7 nm and discuss advantages and limitations of each technique.

scholarly journals The Domain and Microstructure of Resin-Bonded Magnets

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2849
Author(s):  
Marcin Jan Dośpiał
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Size ◽  
Size Distribution ◽  
Domain Structure ◽  
Grain Size Distribution ◽  
Exchange Interactions ◽  
Force Microscopy ◽  
Transmission Electron ◽  
Scanning Electron

This paper presents domain and structure studies of bonded magnets made from nanocrystalline Nd-(Fe, Co)-B powder. The structure studies were investigated using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Mössbauer spectroscopy and X-ray diffractometry. On the basis of performed qualitative and quantitative phase composition studies, it was found that investigated alloy was mainly composed of Nd2(Fe-Co)14B hard magnetic phase (98 vol%) and a small amount of Nd1.1Fe4B4 paramagnetic phase (2 vol%). The best fit of grain size distribution was achieved for the lognormal function. The mean grain size determined from transmission electron microscopy (TEM) images on the basis of grain size distribution and diffraction pattern using the Bragg equation was about ≈130 nm. HRTEM images showed that over-stoichiometric Nd was mainly distributed on the grain boundaries as a thin amorphous border of 2 nm in width. The domain structure was investigated using a scanning electron microscope and metallographic light microscope, respectively, by Bitter and Kerr methods, and by magnetic force microscopy. Domain structure studies revealed that the observed domain structure had a labyrinth shape, which is typically observed in magnets, where strong exchange interactions between grains are present. The analysis of the domain structure in different states of magnetization revealed the dynamics of the reversal magnetization process.

scholarly journals Effect of Morphologically Controlled Hematite Nanoparticles on the Properties of Fly Ash Blended Cement

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 1003
Author(s):  
Pantharee Kongsat ◽  
Sakprayut Sinthupinyo ◽  
Edgar A. O’Rear ◽  
Thirawudh Pongprayoon
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Size Distribution ◽  
Cement Hydration ◽  
Blended Cement ◽  
Spherical Shape ◽  
Particle Sizes ◽  
Fe2o3 Nanoparticles ◽  
Structure And Properties ◽  
Hematite Nanoparticles

Several types of hematite nanoparticles (α-Fe2O3) have been investigated for their effects on the structure and properties of fly ash (FA) blended cement. All synthesized nanoparticles were found to be of spherical shape, but of different particle sizes ranging from 10 to 195 nm depending on the surfactant used in their preparation. The cement hydration with time showed 1.0% α-Fe2O3 nanoparticles are effective accelerators for FA blended cement. Moreover, adding α-Fe2O3 nanoparticles in FA blended cement enhanced the compressive strength and workability of cement. Nanoparticle size and size distribution were important for optimal filling of various size of pores within the cement structure.

scholarly journals Upconversion Luminescence of Silica–Calcia Nanoparticles Co-doped with Tm3+ and Yb3+ Ions

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 937
Author(s):  
Katarzyna Halubek-Gluchowska ◽  
Damian Szymański ◽  
Thi Ngoc Lam Tran ◽  
Maurizio Ferrari ◽  
Anna Lukowiak
Keyword(s):  
Energy Transfer ◽  
Near Infrared ◽  
Upconversion Luminescence ◽  
Sol Gel ◽  
Emission Spectra ◽  
Transmission Electron ◽  
Characteristic Emission ◽  
Diffraction Patterns ◽  
Size Of Particles ◽  
Average Size

Looking for upconverting biocompatible nanoparticles, we have prepared by the sol–gel method, silica–calcia glass nanopowders doped with different concentration of Tm3+ and Yb3+ ions (Tm3+ from 0.15 mol% up to 0.5 mol% and Yb3+ from 1 mol% up to 4 mol%) and characterized their structure, morphology, and optical properties. X-ray diffraction patterns indicated an amorphous phase of the silica-based glass with partial crystallization of samples with a higher content of lanthanides ions. Transmission electron microscopy images showed that the average size of particles decreased with increasing lanthanides content. The upconversion (UC) emission spectra and fluorescence lifetimes were registered under near infrared excitation (980 nm) at room temperature to study the energy transfer between Yb3+ and Tm3+ at various active ions concentrations. Characteristic emission bands of Tm3+ ions in the range of 350 nm to 850 nm were observed. To understand the mechanism of Yb3+–Tm3+ UC energy transfer in the SiO2–CaO powders, the kinetics of luminescence decays were studied.

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