A Critical Investigation on the Existence of Selective Microwave Absorption in the Synthesis of CdSe Quantum Dots

2014 ◽  
Vol 67 (9) ◽  
pp. 1180 ◽  
Author(s):  
Mojtaba Mirhosseini Moghaddam ◽  
C. Oliver Kappe
Keyword(s):  
Quantum Dots ◽  
Microwave Absorption ◽  
Transmission Electron Microscopy Data ◽  
Microwave Assisted Synthesis ◽  
Cdse Quantum Dots ◽  
X Ray Diffraction ◽  
Heating And Cooling ◽  
Transmission Electron ◽  
Microscopy Data ◽  
Heating Mode

The existence of selective microwave absorption phenomena in the synthesis of CdSe quantum dots has been investigated. These types of microwave effects involving selective microwave absorption by specific reagents have recently been proposed in the microwave-assisted synthesis of various nanoparticles. In the present study, the microwave synthesis of CdSe quantum dots was investigated according to a protocol published by Washington and Strouse to clarify the presence of selective microwave heating. Importantly, control experiments involving conventional conductive heating were executed under otherwise (except for the heating mode) identical conditions, ensuring the same heating and cooling profiles, stirring rates, and reactor geometries. Comparison of powder X-ray diffraction, UV-vis, photoluminescence, and transmission electron microscopy data of the obtained CdSe quantum dots reveals that identical types of nanoparticles are obtained independently of the heating mode. Therefore, no evidence for a selective microwave absorption phenomenon could be obtained.

Initial Dynamic Susceptibility of Maghemite Nanoparticles Dispersed in Surface-Treated Polymeric Template

2021 ◽  
Vol 21 (11) ◽  
pp. 5694-5697
Author(s):  
A. F. R. Rodriguez ◽  
R. F. Lacerda ◽  
L. E. Maggi ◽  
Hory Mohammadpour ◽  
Mohammad Niyaifar ◽  
...  
Keyword(s):  
Ex Situ ◽  
Transmission Electron Microscopy Data ◽  
Dynamic Susceptibility ◽  
Maghemite Nanoparticles ◽  
X Ray Diffraction ◽  
Chemical Treatments ◽  
Dynamical Susceptibility ◽  
Transmission Electron ◽  
Microscopy Data ◽  
Polymeric Template

Magnetic nanocomposites based on maghemite nanoparticles supported (ex situ route) on styrene- divinilbenzene (Sty-DVB) copolymer templates were produced and characterized for their structure and morphology. The as-produced nanocomposites were further chemically-treated with different oxidant agents and surface-coated with stearic acid. X-ray diffraction and transmission electron microscopy data show that the incorporated nanoparticles are preserved despite the aggressive chemical treatments employed. From the dynamical susceptibility measurements performed on the nanocomposites, the values of the saturation magnetization (76 emu/g) and the effective magnetic anisotropy (1.7 × 104 J/m3) were obtained, in excellent agreement with the values reported in the literature for maghemite. This finding strongly supports the preservation of the magnetic properties of the supported nanosized maghemite throughout the entire samples’ processing.

Effect of the Pulse Laser Radiation on the Stabilization of the ZrO2 and HFO2 High-Temperature Phases

2015 ◽  
Vol 245 ◽  
pp. 200-203 ◽  
Author(s):  
Maxim Alexandrovich Pugachevskii ◽  
Viktor Igorevich Panfilov
Keyword(s):  
High Temperature ◽  
Transmission Electron Microscopy Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
Good Thermal Stability ◽  
Quantitative Content ◽  
Electron Microscopy Data ◽  
Cubic Phases ◽  
Transmission Electron ◽  
Microscopy Data

The conditions of formation of the ZrO2 and HfO2 high-temperature (tetragonal and cubic) phases in the ablated nanoparticles were investigated. X-ray diffraction and transmission electron microscopy data demonstrate that laser intensities above 109 W/m2 ensure the formation of the ZrO2 high-temperature phases, while intensities above 5·109 W/m2 do the formation of the HfO2 high-temperature phases. Quantitative content of the high-temperature phases in layers of the ablated nanoparticles increases with raising the intensity. The obtained nanoparticles exhibit good thermal stability.

Microstructure characteristics of non-monodisperse quantum dots: on the potential of transmission electron microscopy combined with X-ray diffraction

CrystEngComm ◽  
2020 ◽  
Vol 22 (21) ◽  
pp. 3644-3655
Author(s):  
Stefan Neumann ◽  
Christina Menter ◽  
Ahmed Salaheldin Mahmoud ◽  
Doris Segets ◽  
David Rafaja
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Quantum Dots ◽  
Cdse Quantum Dots ◽  
X Ray Diffraction ◽  
X Ray ◽  
Microstructure Characteristics ◽  
Scale Bridging ◽  
Transmission Electron ◽  
Hot Injection

Capability of TEM and XRD to reveal scale-bridging information about the microstructure of non-monodisperse quantum dots is illustrated on the CdSe quantum dots synthesized using an automated hot-injection method.

scholarly journals Optical and Structural Investigation of CdSe Quantum Dots Dispersed in PVA Matrix and Photovoltaic Applications

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Pallabi Phukan ◽  
Dulen Saikia
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Quantum Dots ◽  
Hexagonal Wurtzite Structure ◽  
Xrd Analysis ◽  
Cdse Quantum Dots ◽  
X Ray Diffraction ◽  
Morphological Studies ◽  
Transmission Electron ◽  
Particle Size Determination

CdSe quantum dots (QDs) dispersed in polyvinyl alcohol (PVA) matrix with their sizes within the quantum dot regime have been synthesized via a simple heat induced thermolysis technique. The effect of the concentrations of the cadmium source on the optical properties of CdSe/PVA thin films was investigated through UV-Vis absorption spectroscopy. The structural analysis and particle size determination as well as morphological studies of the CdSe/PVA nanocomposite thin films were done with the help of X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD analysis reveals that CdSe/PVA nanocomposite thin film has a hexagonal (wurtzite) structure. A prototype thin film solar cell of CdSe/CdTe has been synthesized and its photovoltaic parameters were measured.

Preparation of Helical Monosubstituted Polyacetylene@CdSe Quantum Dots Composite and its Application for Low Infrared Emissivity

2014 ◽  
Vol 1044-1045 ◽  
pp. 88-91
Author(s):  
Xiao Hai Bu ◽  
Yu Ming Zhou ◽  
Man He ◽  
Tao Zhang ◽  
Hu Chuan Wang
Keyword(s):  
Quantum Dots ◽  
Optically Active ◽  
Helical Conformation ◽  
Cdse Quantum Dots ◽  
Infrared Emissivity ◽  
X Ray Diffraction ◽  
Cdse Qds ◽  
Transmission Electron ◽  
Ft Ir ◽  
Ester Linkage

Helical monosubstituted polyacetylene@CdSe quantum dots (HPA@CdSe QDs) nanocomposites were fabricated by grafting helical HPA polymers onto the surface of semiconductor QDs through ester linkage. Optically active HPA derived from chiral serine was polymerized by a rhodium zwitterion catalyst, and evidently proved to adopt a predominately single-handed helical conformation. The HPA@QDs nanocomposites were characterized by Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The results indicate that the HPA matrix exhibits an enhancement in thermal stability after hybridization with CdSe QDs, while the QDs can maintain their original crystalline structure during the grafting process. The infrared emissivity property of the HPA@QDs nanocomposites at 8-14 μm was further investigated. These data demonstrated that the HPA@QDs composite film with doped CdSe QDs possesses an infrared emissivity value of 0.393, which was much lower than pristine HPA and QDs. This might be attributed to the incorporation of optically active helical HPA and semiconductor QDs in a hybrid phase and their strengthened interfacial interaction.

SIZE-DEPENDENT PHOTOLUMINESCENCE AND ELECTROLUMINESCENCE OF COLLOIDAL CdSe QUANTUM DOTS

2013 ◽  
Vol 12 (02) ◽  
pp. 1350013 ◽  
Author(s):  
S. C. DEY ◽  
S. S. NATH
Keyword(s):  
Quantum Dots ◽  
Blue Shift ◽  
Diffraction Spectrum ◽  
Cdse Quantum Dots ◽  
X Ray Diffraction ◽  
Chemical Route ◽  
X Ray ◽  
Light Emitting Devices ◽  
Transmission Electron ◽  
Vis Spectroscopy

Here we adopt a convenient green chemical route for synthesis of CdSe quantum dots, their characterization by UV/Vis absorption spectroscopy, X-ray diffraction study and transmission electron microscopy. We carry out photoluminescence and electroluminescence spectroscopy to investigate the variation in electro-optical property with size. By UV/Vis spectroscopy, blue shift is revealed and bandgap is also calculated. X-ray diffraction spectrum reveals cubic structure and transmission electron micrographs show quantum dots of different size distributions (in the range 2–8 nm). Both the luminescence spectroscopies reveal green-orange luminescence depending upon the size distribution and indicate the possibility of using CdSe quantum dots as light emitting devices with better compatibility and faster response.

scholarly journals Effect of annealing temperature on the structural, morphological and optical properties of TiO2 nanotubes and their composites with CdSe Quantum dots

2019 ◽  
Vol 17 (2) ◽  
Author(s):  
Tani Vats ◽  
Shailesh N. Sharma
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Quantum Dots ◽  
Optical Properties ◽  
Tio2 Nanotubes ◽  
Annealing Temperature ◽  
Cdse Quantum Dots ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron

In the present work we have synthesized Titanium dioxide (TiO2) nanotubes using hydrothermal method, and studied the effect of annealing temperature on the crystalinity of the nanotubes. The nanotubes obtained were annealed at 400o C and 600o C. In order to elucidate the changes caused by the annealing temperature transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) were used. The composites of titania nanotubes and CdSe quantum dots were prepared using bifunctional linker, mercaptopropionic acid. The nanocomposites were characterized using TEM and XDR. The optical propierties of the modified TiO2 nanotubes and their composites with CdSe (for potential solar cell applications) were characterized by UV-Vis absorption spectra and photoluminescence (PL) spectra.

Domain structure of CoIr nanoalloys

2017 ◽  
Vol 32 (S1) ◽  
pp. S155-S159
Author(s):  
Evgeny Yu. Filatov ◽  
Svetlana V. Cherepanova ◽  
Ilia V. Kochetygov ◽  
Yury V. Shubin ◽  
Sergey V. Korenev
Keyword(s):  
Domain Structure ◽  
Transmission Electron Microscopy Data ◽  
Model Parameters ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Hcp Structure ◽  
Face Centered ◽  
Microscopy Data ◽  
Xrd Patterns

X-ray diffraction (XRD) pattern of nanosized equimolar solid solution CoIr prepared by thermolysis of [Co(NH3)6][Ir(C2O4)3] contains peaks characteristic of both face-centered cubic (fcc) and hexagonal close-packed (hcp) structure. Moreover, 101 peak of hcp modification is substantially wider than 100 and 002 peaks, 102 and 103 are very broad and almost invisible. Peak 200 of fcc structure is wider than the other peaks of this modification and slightly shifted toward lower angles. It was shown by simulation of XRD patterns that particles of CoIr alloy are nanoheterogeneous and consist of lamellar domains having fcc and hcp structures. The best fit was obtained for the following model parameters: an average crystallites size is about 10 nm, average thicknesses of the fcc and hcp domains are 1.7 and 1.1 respectively. The presence of domain structure was confirmed by transmission electron microscopy data.

Synthesis, Characterization, and Microwave Absorption Properties of SrFe12O19 Ferrites and FeNi3 Nanoplatelets Composites

2010 ◽  
Vol 148-149 ◽  
pp. 893-896 ◽  
Author(s):  
Ze Yang Zhang ◽  
Xiang Xuan Liu ◽  
You Peng Wu
Keyword(s):  
Electron Microscopy ◽  
Microwave Absorption ◽  
Composite Coatings ◽  
Sol Gel ◽  
X Ray Diffraction ◽  
Absorption Properties ◽  
Filling Fraction ◽  
Microwave Absorption Properties ◽  
Phase Reduction ◽  
Transmission Electron

M-typical SrFe12O19 ferrites and FeNi3 nanoplatelets were successfully prepared by the sol-gel method and solution phase reduction method, respectively. The crystalline and morphology of particles were studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The composite coatings with SrFe12O19 ferrites and FeNi3 nanoplatelets in polyvinylchloride matrix were prepared. The microwave absorption properties of these coatings were investigated in 2-18GHz frequency range. The results showed that the M-typical SrFe12O19 ferrites and FeNi3 nanoplatelets were obtained and they presented irregular sheet shapes. With the increase of the coating thickness, the absorbing peak value moves to the lower frequency. The absorbing peak values of the wave increase along with the increasing of the content of FeNi3 nanoplatelets filling fraction. When 40% SrFe12O19 ferrites is doped with 20% mass fraction FeNi3 nanoplatelets to prepare composite with 1.5mm thickness, the maximum reflection loss is -24.8 dB at 7.9GHz and the -10 dB bandwidth reaches 3.2GHz.

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