scholarly journals Structural and optical investigation of CdSe quantum dots

2013 ◽  
Vol 8 (2) ◽  
pp. 83-88
Author(s):  
Neupane Dipesh
Keyword(s):  
Quantum Dots ◽  
Large Scale ◽  
Room Temperature ◽  
Spherical Shape ◽  
Cdse Quantum Dots ◽  
Optical Investigation ◽  
X Ray ◽  
Transmission Electron ◽  
Engineering And Technology ◽  
Average Size

CdSe semiconducting Quantum dots were prepared by a chemical method at a room temperature. X-ray powder diffraction and transmission electron microscope measurements conformed a hexagonal cubic crystalline phase of Cdse semiconducting Quantum dots of about 15 nm average size with nearly spherical shape. The absorption and photoluminescence spectra of the CdSe quantum dots were strongly shown blue shifted due to size quantization. The present study describes a simultaneous and highly reproducible large scale synthesis of highly luminescent CdSe Quantum dots. Kathmandu University Journal of Science, Engineering and Technology Vol. 8, No. II, December, 2012, 83-88 DOI: http://dx.doi.org/10.3126/kuset.v8i2.7329

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 Formation of ZnO/Zn0.5Cd0.5Se Alloy Quantum Dots in the Presence of High Oleylamine Contents

Nanomaterials ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 999
Author(s):  
Yi-An Chen ◽  
Kuo-Hsien Chou ◽  
Yi-Yang Kuo ◽  
Cheng-Ye Wu ◽  
Po-Wen Hsiao ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Quantum Dots ◽  
Particle Size ◽  
X Ray Diffraction ◽  
One Pot ◽  
X Ray ◽  
Transmission Electron ◽  
Average Size ◽  
Alloy Quantum Dots ◽  
First Time

To the best of our knowledge, this report presents, for the first time, the schematic of the possible chemical reaction for a one-pot synthesis of Zn0.5Cd0.5Se alloy quantum dots (QDs) in the presence of low/high oleylamine (OLA) contents. For high OLA contents, high-resolution transmission electron microscopy (HRTEM) results showed that the average size of Zn0.5Cd0.5Se increases significantly from 4 to 9 nm with an increasing OLA content from 4 to 10 mL. First, [Zn(OAc)2]–OLA complex can be formed by a reaction between Zn(OAc)2 and OLA. Then, Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) data confirmed that ZnO is formed by thermal decomposition of the [Zn(OAc)2]–OLA complex. The results indicated that ZnO grew on the Zn0.5Cd0.5Se surface, thus increasing the particle size. For low OLA contents, HRTEM images were used to estimate the average sizes of the Zn0.5Cd0.5Se alloy QDs, which were approximately 8, 6, and 4 nm with OLA loadings of 0, 2, and 4 mL, respectively. We found that Zn(OAc)2 and OLA could form a [Zn(OAc)2]–OLA complex, which inhibited the growth of the Zn0.5Cd0.5Se alloy QDs, due to the decreasing reaction between Zn(oleic acid)2 and Se2−, which led to a decrease in particle size.

Synthesis and Characterization of SiO2@Y2MoO6:Eu3+ Core–Shell Structured Spherical Phosphors by Sol–Gel Process

2016 ◽  
Vol 16 (4) ◽  
pp. 3914-3920 ◽  
Author(s):  
G. Z Li ◽  
F. H Liu ◽  
Z. S Chu ◽  
D. M Wu ◽  
L. B Yang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Annealing Temperature ◽  
Uv Light ◽  
Sol Gel ◽  
Spherical Shape ◽  
Core Shell ◽  
X Ray ◽  
Transmission Electron ◽  
Sol Gel Process ◽  
Average Size

SiO2@Y2MoO6:Eu3+ core–shell phosphors were prepared by the sol–gel process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectra (EDS), transmission electron microscopy (TEM), photoluminescence (PL) spectra as well as kinetic decays were used to characterize the resulting SiO2@Y2MoO6:Eu3+ core–shell phosphors. The XRD results demonstrated that the Y2MoO6:Eu3+ layers on the SiO2 spheres crystallized after being annealed at 700 °C and the crystallinity increased with raising the annealing temperature. The obtained core–shell phosphors have spherical shape with narrow size distribution (average size ca. 640 nm), non-agglomeration, and smooth surface. The thickness of the Y2MoO6:Eu3+ shells on the SiO2 cores could be easily tailored by varying the number of deposition cycles (70 nm for four deposition cycles). The Eu3+ shows a strong PL emission (dominated by 5D0–7F2 red emission at 614 nm) under the excitation of 347 nm UV light. The PL intensity of Eu3+ increases with increasing the annealing temperature and the number of coating cycles.

scholarly journals Surface Modified Ni Nanoparticles Produced by the Electrical Explosion of Wire

2015 ◽  
Vol 233-234 ◽  
pp. 513-516 ◽  
Author(s):  
A.P. Safronov ◽  
Galina V. Kurlyandskaya ◽  
S.M. Bhagat ◽  
I.V. Beketov ◽  
A.M. Murzakaev ◽  
...  
Keyword(s):  
Room Temperature ◽  
Electrical Explosion ◽  
Resonant Absorption ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Parameters ◽  
Transmission Electron ◽  
Average Size ◽  
Surface Modified ◽  
Made In

Spherical nickel nanoparticles were prepared by the electrical explosion of wire. The as-prepared nanoparticles were modified immediately after fabrication at room temperature in order to provide tunable surface properties with focus on the development of composites filled with nanoparticles. Following liquid modificators were used: hexane, toluene and the solution of polystyrene in toluene. In one case the surface modification by carbon was made in gas phase as a result of hydrocarbon injection. The average size of the nanoparticles was about 50 nm and unit cell parameters were close to 0.351 nm. Detailed characterization was done by X-ray diffraction, transmission electron microscopy, and magnetization measurements. Sphericity was also checked using microwave resonant absorption.

Synthesis of SrTiO3 Nanoparticles by a Simple Sonochemical Method

2012 ◽  
Vol 424-425 ◽  
pp. 949-952
Author(s):  
Yu Jiang Wang ◽  
Lin Lin Yang ◽  
Yong Gang Wang
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Powder Diffraction ◽  
Room Temperature ◽  
Spherical Shape ◽  
Sonochemical Method ◽  
X Ray ◽  
Transmission Electron ◽  
Ultrasonic Time ◽  
Pure Phase

SrTiO3 nanoparticles were successfully synthesized by a sonochemical method at room temperature. The as-prepared powders were characterized by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM), and exhibited a pure phase SrTiO3 with a perovskite structure about 20nm in size with uniform and nearly spherical shape. It is found that the size of the obtained nanoparticles increased with prolonging the ultrasonic time.

FLUORESCENCE STUDY OF CdSe QUANTUM DOTS SUSPENDED IN LIQUID PARAFFIN

NANO ◽  
2010 ◽  
Vol 05 (06) ◽  
pp. 357-359 ◽  
Author(s):  
S. C. DEY ◽  
R. DAS ◽  
S. S. NATH ◽  
R. BHATTACHERJEE
Keyword(s):  
Quantum Dots ◽  
Liquid Paraffin ◽  
Green Light ◽  
Cdse Quantum Dots ◽  
Fluorescence Study ◽  
Optical Source ◽  
Chemical Route ◽  
Transmission Electron ◽  
Vis Spectroscopy ◽  
Average Size

Here we report a safer, easier, and quicker chemical route for synthesis of CdSe quantum dots (QDs), followed by their characterizations by UV/vis Spectroscopy (UV/vis), X-ray diffraction study (XRD), High Resolution Transmission Electron Microscopy (HRTEM) and fluorescence (FL) spectroscopy. The average size of the quantum dots is 7.5 nm. Fluorescence study reveals that CdSe quantum dots emit green light when excited by optical source of wavelength of 550 nm or less.

One-Step Synthesis of CdSe Quantum Dots by Using Hydrazine Hydrate Reduction of Selenium Dioxide

2018 ◽  
Vol 71 (7) ◽  
pp. 524 ◽  
Author(s):  
Rongfang Wang ◽  
Xingming Wei ◽  
Jun Xie ◽  
Bomei Wang ◽  
Xiaotong He
Keyword(s):  
Quantum Dots ◽  
Hydrazine Hydrate ◽  
Selenium Dioxide ◽  
Water Soluble ◽  
Molar Ratio ◽  
Cdse Quantum Dots ◽  
Cdse Qds ◽  
Original Solution ◽  
Transmission Electron ◽  
Average Size

Hydrazine hydrate was used as a novel reducing agent for the synthesis of water soluble and stable cadmium selenide (CdSe) quantum dots (QDs). The as-prepared CdSe quantum dots were investigated by X-ray powder diffraction, high-resolution transmission electron microscopy, photoluminescence, and UV-vis absorption spectroscopy analyses. The results show that the as-prepared CdSe QDs possess a cubic crystal structure and an average size of 2 nm. The effects of the pH of the original solution, thioglycollic acid (TGA)/Cd2+ molar ratio (nTGA/nCd2+), and the Cd/Se molar ratio on the luminescence properties of CdSe QDs were also systematically analysed.

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 Gas Phase Growth of Wurtzite ZnS Nanobelts on a Large Scale

2013 ◽  
Vol 2013 ◽  
pp. 1-4 ◽  
Author(s):  
Jing Wang ◽  
Yang Jiao ◽  
Yang Liu ◽  
Zhenglin Zhang ◽  
Fengyu Qu ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Large Scale ◽  
Room Temperature ◽  
Thermal Evaporation ◽  
Deep Level ◽  
Green Emission ◽  
X Ray Diffraction ◽  
Phase Growth ◽  
X Ray ◽  
Transmission Electron

We showed large-scale synthesis of ZnS nanobelts by simply thermal evaporation of ZnS powder in the presence of Au catalysts at 1020°C. Scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD) analyses demonstrated that the as-obtained ZnS nanobelts possess hexagonal wurtzite structures. The nanobelts have lengths ranging from tens to hundreds of micrometers, thicknesses of tens of nanometers, and widths ranging from hundreds of nanometers to the order of micrometers. The growth process was proposed on the basis of known vapor-liquid-solid (VLS) mechanism. Room temperature photoluminescence measurements showed that the as-synthesized ZnS nanostructures had a strong green emission bands at a wavelength of 427 nm, which can be attributed to deep-level emissions induced by defects or impurities.

scholarly journals Precursor concentration and temperature controlled formation of polyvinyl alcohol-capped CdSe-quantum dots

2010 ◽  
Vol 1 ◽  
pp. 119-127 ◽  
Author(s):  
Chetan P Shah ◽  
Madhabchandra Rath ◽  
Manmohan Kumar ◽  
Parma N Bajaj
Keyword(s):  
Quantum Dots ◽  
Polyvinyl Alcohol ◽  
Room Temperature ◽  
Near Infrared ◽  
Deep Trap ◽  
Optical Absorption Spectroscopy ◽  
Band Edge Emission ◽  
Cdse Quantum Dots ◽  
Trap States ◽  
Transmission Electron

Polyvinyl alcohol-capped CdSe quantum dots, with a size within their quantum confinement limit, were prepared in aqueous solution at room temperature, by a simple and environmentally friendly chemical method. The size of the CdSe quantum dots was found to be dependent on the concentrations of the precursors of cadmium and selenium ions, as well as on the aging time and the reaction temperature; all of which could be used conveniently for tuning the size of the particles, as well as their optical properties. The synthesized quantum dots were characterized by optical absorption spectroscopy, fluorescence spectroscopy, X-ray diffraction, atomic force microscopy and transmission electron microscopy. The samples were fluorescent at room temperature; the green fluorescence was assigned to band edge emission, and the near-infrared fluorescence peaks at about 665 and 865 nm were assigned to shallow and deep trap states emissions, respectively. The quantum dots were fairly stable up to several days.

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