Enhancement of Luminescence Behaviour of Colloidal ZnO Quantum Dots Coated with SiO2 Irradiated by Ni+7 Ion

2020 ◽  
Vol 12 (2) ◽  
pp. 278-283
Author(s):  
Dipankar Chakdar ◽  
Abubakkar Siddik ◽  
Nikita Ghosh ◽  
Gautam Gope ◽  
Prabir Kumar Haldar
Keyword(s):  
Quantum Dots ◽  
Ion Irradiation ◽  
Ion Beam ◽  
Particle Diameter ◽  
Photo Luminescence ◽  
Chemical Route ◽  
Transmission Electron ◽  
Large Numbers ◽  
Zno Quantum Dots ◽  
Average Size

ZnO quantum dots of average size 10 nm are embedded in a matrix (polyvinyl alcohol (PVA)) following chemical route. They are irradiated by 100 MeV Ni7+ ion beam with fluences 1 × 1011, 3 × 1011, 1 × 1012 and 3 × 1012 ions/cm2. The optical absorption edge of irradiated quantum dots reveal negligible red shift with an increase in fluences with respect to that of unirradiated (virgin) ones. This fact clearly indicates no significant change in particle diameter under ion irradiation and is confirmed by high resolution transmission electron microscopy (TEM). AFM study also reveals the r.m.s surface roughness of the particles. It has also been observed that irradiated quantum dots produce similar type of photo luminescence and electroluminescence like virgin samples but the emission intensity increases remarkably after irradiation due to creation of large numbers oxygen vacancies by the ion beam.

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.

Ligand-Stabilized ZnO Quantum Dots: Molecular Dynamics and Experimental Study

2017 ◽  
Vol 70 (10) ◽  
pp. 1110 ◽  
Author(s):  
Rohul Hayat Adnan ◽  
Kai Lin Woon ◽  
Narong Chanlek ◽  
Hideki Nakajima ◽  
Wan Haliza Abd. Majid
Keyword(s):  
Molecular Dynamics ◽  
Quantum Dots ◽  
Emission Peak ◽  
Excitation Wavelength ◽  
Quantum Size ◽  
Transmission Electron ◽  
Zno Quantum Dots ◽  
Average Size ◽  
Semi Empirical ◽  
Zno Qds

Different aminoalcohol ligands, monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA) were employed to passivate the surface of ZnO quantum dots (ZnO QDs). High-resolution transmission electron microscopy (HRTEM) imaging revealed that the higher branched aminoalcohols produced smaller sized ZnO QDs. The average size for ZnO/MEA, ZnO/DEA, and ZnO/TEA were found to be 3.2, 2.9, and 2.4 nm. TEA ligands were effective in producing stable, monodisperse ZnO QDs compared with DEA and MEA ligands. Molecular dynamics and semi-empirical calculations suggested that TEA and DEA ligands interact strongly with the partial charge of ZnO dangling bonds and have a large molar volume to hinder the diffusion of precursors through the ligands to the surface of ZnO resulting in a smaller particle size as compared with MEA ligands. As the size of ZnO QDs decreases from ZnO/MEA to ZnO/TEA, the absorption edge and emission peak maximum blue-shifts to a shorter wavelength due to the quantum size effect. The bandgap of ZnO/MEA, ZnO/DEA, and ZnO/TEA was determined to be 3.97, 4.07, and 4.23 eV, and the emission peak was found to be 472, 464, and 458 nm when excited using a 325 nm excitation wavelength, respectively.

scholarly journals ZnSe Quantum Dots through a Facile one Pot Synthesis Process

2015 ◽  
Vol 34 ◽  
pp. 73-78
Author(s):  
Irtiqa Syed ◽  
Santa Chawla
Keyword(s):  
Quantum Dots ◽  
Band Gap ◽  
Quantum Confinement Effect ◽  
Hexagonal Phase ◽  
Fluorescence Decay ◽  
Synthesis Process ◽  
One Pot ◽  
One Pot Synthesis ◽  
Transmission Electron ◽  
Average Size

A novel one pot synthesis approach in oleic acid medium was employed to obtain monophasic ZnSe quantum dots (QD) of average size 3.7nm. The QDs were well crystalline in hexagonal phase as revealed by x-ray diffraction and high resolution transmission electron microscopy (HRTEM) studies. The ZnSe QDs exhibit sharp emission peak in the blue (465nm) with 385picosecond fluorescence decay time. The theoretical band gap corresponding to 3.7nm ZnSe QDs matched well with the measured 3.11eV band gap of synthesized QDs which thus showed quantum confinement effect.

scholarly journals Tuning of Localized Surface Plasmon Resonance in Copper-Copper Oxide Core-Shell Quantum Dots for the Application in Biosensors

2020 ◽  
Author(s):  
Prabhash Prasannan Geetha ◽  
Ajith Ramachandran ◽  
Swapna S. Nair
Keyword(s):  
Quantum Dots ◽  
Surface Plasmon Resonance ◽  
Copper Oxide ◽  
Surface Plasmon ◽  
Plasmon Resonance ◽  
Particle Diameter ◽  
Noble Metal Nanoparticles ◽  
Localized Surface Plasmon ◽  
Core Shell ◽  
Chemical Route

Surface Plasmon Resonance (SPR) is an attracting property of certain transition metals when they are synthesized in nano-range giving rise to promising optical applications. However, most SPR and associated applications are limited to the noble metal nanoparticles, which limits their potential due to high production cost. We report surface plasmon resonance in copper-copper oxide core-shell quantum dots synthesized via chemical route studied by using UV-Visible spectrophotometry. Tuning of the plasmonic resonance with respect to the particle diameter is achieved by an inexpensive all chemical route. Photoluminescence measurements also support the data. This size reduction leads to remarkable changes in its optical response as compared to the bulk metal. The results point towards applications of these materials in tunable SPR based biosensors.

Amortization and Recrystallization of 6H-SiC by ion Beam Irradiation

1994 ◽  
Vol 339 ◽  
Author(s):  
V. Heera ◽  
R. Kögler ◽  
W. Skorupa ◽  
J. Stoemenos
Keyword(s):  
Ion Irradiation ◽  
Ion Beam ◽  
Surface Region ◽  
Ion Beam Irradiation ◽  
Surface Layers ◽  
Near Surface ◽  
Transmission Electron ◽  
Amorphous Surface ◽  
Amorphous Sic

ABSTRACTThe evolution of the damage in the near surface region of single crystalline 6H-SiC generated by 200 keV Ge+ ion implantation at room temperature (RT) was investigated by Rutherford backscattering spectroscopy/chanelling (RBS/C). The threshold dose for amorphization was found to be about 3 · 1014 cm-2, Amorphous surface layers produced with Ge+ ion doses above the threshold were partly annealed by 300 keV Si+ ion beam induced epitaxial crystallization (IBIEC) at a relatively low temperature of 480°C For comparison, temperatures of at least 1450°C are necessary to recrystallize amorphous SiC layers without assisting ion irradiation. The structure and quality of both the amorphous and recrystallized layers were characterized by cross-section transmission electron microscopy (XTEM). Density changes of SiC due to amorphization were measured by step height measurements.

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.

scholarly journals Hydrothermal synthesis of ZnO quantum dot/KNb3O8 nanosheet photocatalysts for reducing carbon dioxide to methanol

2017 ◽  
Vol 8 ◽  
pp. 2264-2270 ◽  
Author(s):  
Xiao Shao ◽  
Weiyue Xin ◽  
Xiaohong Yin
Keyword(s):  
Electron Microscopy ◽  
Quantum Dots ◽  
Uv Light ◽  
Formation Rate ◽  
X Ray Diffraction ◽  
Methanol Production ◽  
X Ray ◽  
Transmission Electron ◽  
Methanol Formation ◽  
Zno Quantum Dots

ZnO quantum dots and KNb3O8 nanosheets were synthesized by a two-step hydrothermal method for the photocatalytic reduction of CO2 to methanol where isopropanol is simultaneously oxidized to acetone . The as-prepared photocatalysts were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and UV–vis absorption spectroscopy (UV–vis). The photocatalytic activity of the materials was evaluated by formation rate of methanol under UV light irradiation at ambient temperature and pressure. The methanol formation rate of pure KNb3O8 nanosheets was found to be 1257.21 μmol/g/h, and after deposition of 2 wt % ZnO quantum dots on the surface of KNb3O8 nanosheets, the methanol production rate was found to increase to 1539.77 μmol/g/h. Thus, the ZnO quantum dots obviously prompted separation of charge carriers, which was explained by a proposed mechanism for this photocatalytic reaction.

Studies on Optical Properties of CdS/ZnO Quantum Dots Prepared by Sol-Gel Method

2011 ◽  
Vol 364 ◽  
pp. 129-133 ◽  
Author(s):  
Liyana Mohd Lawi Ruhana ◽  
Taqiyuddin Mawardi Ayob Muhammad ◽  
Radiman Shahidan ◽  
Irman Abdul Rahman ◽  
Bohari M. Yamin
Keyword(s):  
Quantum Dots ◽  
Sol Gel ◽  
Emission Spectra ◽  
Blue Shift ◽  
Mixture Ratio ◽  
Gel Method ◽  
Sol Gel Method ◽  
Transmission Electron ◽  
Zno Quantum Dots ◽  
Zno Qds

CdS/ZnO quantum dots (QDs) were prepared at a temperature of 293 K by the sol-gel method with Triethanolamine (TEA) as a capping agent. The effect of CdS/ZnO mixture ratio of 1:9, 1:1 and 9:1 on the optical absorption and fluorescence spectra were investigated by UV-Vis and Fluorescence spectroscopy. By increasing ZnO composition, a blue-shift of absorption edge and emission spectra were observed. The band gap for 1:9, 1:1 and 9:1 were found to be 4.13, 3.93 and 3.11 eV, respectively. The morphology of the CdS/ZnO QDs for each mixing ratio was obtained by transmission electron microscope (TEM). The size of the QDs was found to be in the range of 5-10 nm with some agglomerated particles.

STRUCTURAL AND OPTICAL PROPERTIES OF SINGLE CRYSTALLINE BISMUTH NANOPARTICLES IN POLYMER

2013 ◽  
Vol 22 ◽  
pp. 654-659 ◽  
Author(s):  
LUTFUL KABIR ◽  
SWAPAN K. MANDAL
Keyword(s):  
Optical Properties ◽  
Absorption Spectrum ◽  
Structural And Optical Properties ◽  
Chemical Route ◽  
Plasmon Band ◽  
Single Crystalline ◽  
Bismuth Nanoparticles ◽  
Transmission Electron ◽  
Average Size ◽  
Bi Nanoparticles

We report here the structural and optical properties of Bi nanoparticles in polymer (polypyrrole) matrix. The nanoparticles are synthesized following a wet chemical route. The X-ray diffraction data clearly shows the growth of single crystalline Bi nanoparticles within the host polymer. The microstructure of the Bi nanoparticles obtained by transmission electron microscopy (TEM) reveals clearly the formation of spherical shaped nanoparticles of average size∼27 nm with a narrow size distribution. The optical absorption spectrum exhibits a distinct peak at 278 nm which is attributed to the surface plasmon band of Bi nanoparticles. The absorption spectrum is found to be described well following Mie theory.

scholarly journals Effects of the Surface on Displacement Cascades Produced by Heavy-Ion Irradiation of Ni3Al and Cu3Au

1996 ◽  
Vol 439 ◽  
Author(s):  
S. Müller ◽  
M. L. Jenkins ◽  
C. Abromeit ◽  
H. Wollenberger
Keyword(s):  
Ion Irradiation ◽  
Incident Angle ◽  
Ion Beam ◽  
Heavy Ion ◽  
Small Population ◽  
Dislocation Loops ◽  
Near Surface ◽  
Ion Energy ◽  
Heavy Ion Irradiation ◽  
Transmission Electron

AbstractStereo transmission electron microscopy has been used to characterise the distribution in depth of disordered zones and associated dislocation loops in the ordered alloys Ni3Al and Cu3Au after heavy ion irradiation, most extensively for Ni3Al irradiated with 50 keV Ta+ ions at a temperature of 573 K. The Cu3Au specimen was irradiated with 50 keV Ni+ ions at an incident angle of 45° at a temperature of 373 K. In Ni3Al the defect yield, i.e. the probability for a disordered zone to contain a loop was found to be strongly dependent on the depth of the zone in the foil, varying from about 0.7 for near-surface zones to about 0.2 in the bulk. The sizes and shapes of disordered zones were only weakly dependent on depth, except for a small population of zones very near the surface which were strongly elongated parallel to the incident ion beam. In Cu3Au the surface had a smaller but still significant effect on the defect yield. The dependence of the tranverse disordered zone diameter d on ion energy E for Ta+ irradiation of NiA was found to follow a relationship d = k1, E1/α with k, = 2.4 ± 0.4 and α = 3.3 ± 0.4. A similar relationship with the same value of α is valid for a wide variety of incident ion/target combinations found in the literature.

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