scholarly journals Near UV-Blue Excitable Green-Emitting Nanocrystalline Oxide

2011 ◽  
Vol 2011 ◽  
pp. 1-7 ◽  
Author(s):  
C. E. Rodríguez-García ◽  
N. Perea-López ◽  
G. A. Hirata
Keyword(s):  
Broad Band ◽  
Emission Peak ◽  
Electronic Transitions ◽  
Excitation Band ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Pl Emission ◽  
Intense Broad Band ◽  
Nanocrystalline Oxide

Green-emitting Eu-activated powders were produced by a two-stage method consisting of pressure-assisted combustion synthesis and postannealing in ammonia. The as-synthesized powders exhibited a red photoluminescence (PL) peak located at  nm when excited with  nm UV. This emission peak corresponds to the5D0→7F2transition in Eu3+. After annealing in ammonia, the PL emission changed to an intense broad-band peak centered at  nm, most likely produced by 4f65d1→4f7electronic transitions in Eu2+. This green-emitting phosphor has excitation band in the near UV-blue region (–450 nm). X-ray diffraction analysis reveals mainly the orthorhombic EuAlO3and Al2O3phases. Transmission electron microscopy observations showed that the grains are formed by faceted nanocrystals (~4 nm) of polygonal shape. The excellent excitation and emission properties make these powders very promising to be used as phosphors in UV solid-state diodes coupled to activate white-emitting lamps.

scholarly journals Cubic InGaN Grown by MOCVD

1999 ◽  
Vol 4 (S1) ◽  
pp. 239-243
Author(s):  
J.B. Li ◽  
Hui Yang ◽  
L.X. Zheng ◽  
D.P. Xu ◽  
Y.T. Wang
Keyword(s):  
Room Temperature ◽  
Emission Peak ◽  
Buffer Layers ◽  
Cubic Phase ◽  
Yellow Luminescence ◽  
X Ray Diffraction ◽  
High Quality ◽  
X Ray ◽  
Cubic Gan ◽  
Pl Emission

We report on the growth of high-quality cubic phase InGaN on GaAs by MOCVD. The cubic InGaN layers are grown on cubic GaN buffer layers on GaAs (001) substrates. The surface morphology of the films are mirror-like. The cubic nature of the InGaN films is obtained by X-ray diffraction (XRD) measurements. The InGaN layers show strong photoluminescence (PL) at room temperature. Neither emission peak from wurtzite GaN nor yellow luminescence is observed in our films. The highest In content as determined by XRD is about 17% with an PL emission wavelength of 450 nm. The FWHM of the cubic InGaN PL peak are 153 meV and 216 meV for 427 nm and 450 nm emissions, respectively. It is found that the In compositions determined from XRD are not in agreement with those estimated from PL measurements. The reasons for this disagreement are discussed.

scholarly journals Green synthesis and characterization of cuprous oxide nanoparticles in presence of a bio-surfactant

2014 ◽  
Vol 32 (4) ◽  
pp. 702-708 ◽  
Author(s):  
M. Behera ◽  
G. Giri
Keyword(s):  
Green Synthesis ◽  
Photoelectron Spectroscopy ◽  
Broad Band ◽  
X Ray Diffraction ◽  
Oh Groups ◽  
X Ray ◽  
Transmission Electron ◽  
Fcc Lattice ◽  
Perennial Shrub ◽  
A Charge

AbstractHerein, we report a facile green synthesis of Cu2O nanoparticles (NPs) using copper sulfate as precursor salt and hydrazine hydrate as reducing agent in presence of bio-surfactant (i.e. leaves extract of arka — a perennial shrub) at 60 to 70 °C in an aqueous medium. A broad band centered at 460 nm in absorption spectrum reveals the formation of surfactant stabilized Cu2O NPs. X-ray diffraction pattern of the surfactant stabilized NPs suggests the formation of only Cu2O phase in assistance of a bio-surfactant with the crystallite size of ∼8 nm. A negative zeta potential of −12 mV at 8.0 pH in surfactant stabilized Cu2O NPs hints non-bonding electron transfer from O-atom of saponin to the surface of NP. Red-shift in the vibrational band (Cu-O stretching) of Cu2O from 637 cm−1 to 640 cm−1 in presence of bio-surfactant suggests an interfacial interaction between NPs and O-atoms of -OH groups of saponin present in the plant (i.e. Calotropis gigantean) extract. From X-ray photoelectron spectroscopy spectra, a decrease in binding energy of both 2p3/2 and 2p1/2 bands in Cu2O with saponin molecules as compared to bulk Cu atom reveals a charge transfer interaction between NP and saponin surfactant molecules. Transmission electron microscopy images show crystalline nature of Cu2O NPs with an fcc lattice.

scholarly journals Outstanding Photoluminescence in Pr3+-Doped Perovskite Ceramics

Micromachines ◽  
2018 ◽  
Vol 9 (9) ◽  
pp. 419
Author(s):  
Jiameng Zhang ◽  
Yanan Hao ◽  
Meihua Bi ◽  
Guoyan Dong ◽  
Xiaoming Liu ◽  
...  
Keyword(s):  
Emission Spectra ◽  
Green Emission ◽  
Emission Peak ◽  
Ferroelectric Ceramics ◽  
X Ray Diffraction ◽  
Green Band ◽  
Conventional Solid State Reaction ◽  
X Ray ◽  
Application Range ◽  
Pl Emission

Ba (Zr0.2Ti0.8) O3-50% (Ba0.7Ca0.3) TiO3 (BZT-0.5BCT) ceramics with different doping contents of Pr3+ were prepared by the conventional solid-state reaction. The phase structure and crystallinity of the fabricated ceramics were investigated by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. Photoluminescence (PL) emission spectra were measured to analyze the PL characteristics. The strong intensities of a green band at 489 nm and a red band at 610 nm were observed. The maximum emission intensity of the PL spectrum was achieved in the BZT-0.5BCT ceramic with 0.2% mol of Pr3+ ions. Furthermore, the PL spectra of BZT-0.5BCT ceramics were found to be sensitive to polarization of the ferroelectric ceramics. Compared with the unpoled ceramics, the green emission increased about 42% and a new emission peak at 430 nm appeared for the poled ceramics. With excellent intrinsic ferroelectricity and an enhanced PL property, such material has potential to realize multifunctionality in a wide application range.

Simplified Synthesis and Luminous Mechanism of Eu2+-Doped α-Si3N4 Nanowires with Strong Green Luminescent Properties

2017 ◽  
Vol 727 ◽  
pp. 635-641 ◽  
Author(s):  
Rui Su ◽  
Zhi Feng Huang ◽  
Fei Chen ◽  
Qiang Shen ◽  
Lian Meng Zhang
Keyword(s):  
Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
Broad Band ◽  
Luminescent Properties ◽  
X Ray Diffraction ◽  
X Ray ◽  
Broad Band Emission ◽  
Band Emission ◽  
Nitridation Process ◽  
Transmission Electron

Ultra-long, single crystal, Eu-doped α-Si3N4 nanowires were prepared by a simple approach involving nitriding Eu-doped cryomilled nanocrystalline Si powder in NH3 flow at 1350 °C for 4 h. Phases, chemical composition and microcosmic feature of cryomilled powders and as-prepared nanowires were tested by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), respectively. The results suggested that Eu was successfully introduced into Si lattice after the cryomilling process and then entered into the lattice of α-Si3N4 during the nitridation process. The as-synthesized Eu-doped α-Si3N4 nanowires had highly uniform dimension with 20~30 nm in diameter and ~100 μm in length. The room temperature photoluminescence (PL) spectrum of as-synthesized nanowires showed a broad band emission center at 570 nm which was attributed to the transition from 4f65d to 4f7 in Eu2+. The transition from Eu3+ to Eu2+ during nitridation process was tested by X-ray photoelectron spectroscopy (XPS).

Piezoelectric Material for High Efficiency Ultrasonic Siren

2006 ◽  
Vol 514-516 ◽  
pp. 225-229
Author(s):  
Elena Dimitriu ◽  
Alin Iuga
Keyword(s):  
Electron Microscopy ◽  
High Efficiency ◽  
Sintered Material ◽  
Broad Band ◽  
Radial Mode ◽  
X Ray Diffraction ◽  
X Ray ◽  
Acoustical Emission ◽  
Transmission Electron ◽  
Dielectric And Piezoelectric Properties

A PZT-type material, doped with niobium and lithium was prepared by the ceramic technique. The microstructure of the sintered material at 1280oC was performed by scanning electron microscopy (SEM), transmission electron microscopy and by X-ray diffraction. Dielectric and piezoelectric properties were measured. The good planar properties of the material made it possible to obtain ceramic disks with a strong radial mode. Two such disks, glued together, with opposed polarisation constitute a bimorf element, which successfully converts the radial mode into a flexural one. At the center of the bimorf a conical acoustical impedance adapter is fixed in order to increase the frontal acoustical emission of the device. This ultrasonic device provides a broad – band, high acoustical emission, and is suitable to work as a high efficiency ultrasonic siren. It can be used in intruder alarm devices, ultrasonic telemeters.

Preparation of hexagonal cerium oxide nanoflakes by a surfactant-free route and its optical property

2007 ◽  
Vol 22 (11) ◽  
pp. 3006-3013 ◽  
Author(s):  
X. Yu ◽  
P. Ye ◽  
L. Yang ◽  
S. Yang ◽  
P. Zhou ◽  
...  
Keyword(s):  
Cerium Oxide ◽  
Visible Region ◽  
Blue Shift ◽  
Emission Peak ◽  
X Ray Diffraction ◽  
X Ray ◽  
Strong Reflection ◽  
Mean Size ◽  
The Mean ◽  
Pl Emission

Hexagonal cerium oxide nanoflakes have been synthesized by using a surfactant-free route. Transmission electcron microscopy (TEM), x-ray diffraction (XRD), infrared spectroscopy (FTIR), thermogravimetric and differential thermal analysis (TG-DTA), Brunauer–Emmett–Teller adsorption isotherm (BET), photoluminescence (PL), and ultraviolet–visible (UV–VIS) were used to characterize the sample. The mean size of the nanoflakes is about 30 nm and the specific surface is about 70.08 m2·g−1 when annealed at 400 °C. The acidity and superfluous NH4NO3 play a key role on the formation of nanoflakes in which there exists Ce (IV) and very little Ce (III). The nanoflakes exhibit a wide PL emission peak among 350–400 nm, strong absorption ranged from 200–450 nm, and strong reflection in the visible region. As the sizes of as-prepared samples decrease, a clear blue shift in the absorbing edge is observed. The linear relationship between ΔEg and D is shown in a log–log plot. The as-prepared cerium oxide nanoflakes can be widely used as UV absorbent and polishing materials.

SYNTHESIS AND PHOTOLUMINESCENCE PROPERTIES OF MICRON-ALUMINA

2014 ◽  
Vol 21 (02) ◽  
pp. 1450031
Author(s):  
SHIHUA ZHAO ◽  
ZHENG WANG ◽  
MINGQUAN WANG ◽  
YUTING CUI ◽  
QUANLIN LIU
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electronic Transitions ◽  
Photoluminescence Properties ◽  
X Ray Diffraction ◽  
Preparation Methods ◽  
X Ray ◽  
Transmission Electron ◽  
Xrd Patterns ◽  
Many Particles

Micron-alumina is expected to be of new properties and applications owing to its different morphology structures, which is prepared by the conventional preparation methods. X-ray diffraction (XRD) patterns present that the micron-alumina has poly-crystalline structure. Scanning electron microscopy (SEM) shows that the micron-alumina looks like a bouquet of flowers and its surface is covered with much micron-strips. Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) show that the micron-alumina is composed of many particles, which has polycrystalline structure. PL spectra display that emission peak of the micron-alumina centers at 301 nm, which attributes to the F + centers. A schematic drawing for electronic transitions in the excitation and emission processes is proposed.

Phosphine-Free Synthesis and Photoluminescence Properties of ZnSe:Cu/ZnSe/ZnS Core/Shell Nanocrystals

2012 ◽  
Vol 549 ◽  
pp. 12-16 ◽  
Author(s):  
Jin Zhong Niu ◽  
Gui Min Tian ◽  
Li Li Zheng ◽  
Yong Guang Cheng ◽  
Shuang Mei Zhu ◽  
...  
Keyword(s):  
Emission Peak ◽  
Core Shell ◽  
Size Distributions ◽  
Photoluminescence Properties ◽  
X Ray Diffraction ◽  
X Ray ◽  
Zinc Blende ◽  
Transmission Electron ◽  
Structures And Properties ◽  
Znse Nanocrystals

High quality zinc blende ZnSe nanocrystals were successfully synthesized using an environmentally friendierly phosphine-free method. Using pre-synthesized ZnSe nanocrystals as core to dope Cu2+ ions, we obtained ZnSe:Cu/ZnSe and ZnSe:Cu/ZnSe/ZnS core/shell nanocrystals. Absorption spectruscopy, photoluminescence (PL) spectruscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM) were used to characterize the structures and properties of as-synthesized three kinds of nanocrystals. The results demonstrated that nanocrystals had well dispersion and narrow size-distributions, and the PL emission peak of as-synthesized ZnSe:Cu/ZnSe/ZnS core/shell nanocrystals could be easily tuned from 480 nm to 520 nm by using different sized ZnSe cores.

Synthesis, Characterization and Optical Property of KLaF4:Ce3+ Nano Particle

2015 ◽  
Vol 778 ◽  
pp. 183-186
Author(s):  
Yan Xia Han ◽  
Qian Nan Li ◽  
Hai Yun Shen ◽  
Qiu Hua Yang
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Emission Peak ◽  
Precipitation Method ◽  
Nano Particle ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Co Precipitation ◽  
Luminescent Spectrum

Ce3+doped cubic KLaF4system was synthesized by co-precipitation method. The sample was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-Vis spectrophotometer and fluorescence spectrophotometer. The result indicated the nanoparticle diameter of KLaF4:Ce3+was 12.5 nm. The KLaF4:Ce3+had a stronger absorption at 250 nm, which could be explained by d elecronic transition of Ce3+. The maximum emission peak of KLaF4:Ce3+was 355 nm in its luminescent spectrum, and emission band of Ce3+also belonged to 5d→4f transition.

Thermally Evaporated In2O3 Nanoloquats with Tunable Broad-Band Emissions

2008 ◽  
Vol 8 (9) ◽  
pp. 4395-4398
Author(s):  
Tsung-Shine Ko ◽  
Tien-Chang Lu ◽  
Chia-Pu Chu ◽  
Hao-Chung Kuo ◽  
Shing-Chung Wang
Keyword(s):  
Electron Microscopy ◽  
Tuning Range ◽  
Broad Band ◽  
Oxygen Flow ◽  
Light Illumination ◽  
X Ray Diffraction ◽  
Flow Rates ◽  
X Ray ◽  
Transmission Electron ◽  
White Light Illumination

We describe synthesis of In2O3 nanoloquats grown by thermal evaporation under different oxygen flow rates and temperatures. Gold nanoparticles were used the catalysts and were dispersed on the silicon wafer to assist growth of In2O3 nanoloquats. The nanostructures of In2O3 nanoloquats were characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The photoluminescence study reveals that In2O3 nanoloquats could emit different broad-band luminescence peaks in the range of 410∼620 nm by tuning different oxygen flow rates and temperatures. The wide tuning range in the emission peaks of In2O3 nanoloquats has potential in applications of white light illumination.

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