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.

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

The Enhancement of Band Edge Emission from ZnS/Zn(OH)2 Quantum Dots

2000 ◽  
Vol 642 ◽  
Author(s):  
Hatim Mohamed El-Khair ◽  
Ling Xu ◽  
Xinfan Huang ◽  
Minghai Li ◽  
Xiaofeng Gu ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Surface Passivation ◽  
Band Edge ◽  
Band Edge Emission ◽  
Trap States ◽  
Edge Emission ◽  
Surface Trap ◽  
Quantum Size ◽  
Transmission Electron

ABSTRACTWurtzite structure monodisperse ZnS quantum dots (QDs) of 1 to 5 nm diameter, synthesized by colloidal chemical method, were confirmed by transmission electron microscopy (TEM) images and electron diffraction (ED) patterns. Enhanced blue shifted band edge emission from Zn(OH)2 capped ZnS QDs with decreasing size has been observed, which indicates the role of inorganic surface passivation and hence supports the quantum size effect. Detectable far-red shifted emission from bare ZnS QDs has been observed when QDs precursors and stabilizer dispersed in solvents with different polarities. This emission is attributed to the surface trap states of different energies.

L-cysteine functionalized graphene quantum dots for sub-ppb detection of As (III)

2021 ◽  
Author(s):  
Md. Farhan Naseh ◽  
Neelam Singh ◽  
Jamilur R. Ansari ◽  
Ashavani Kumar ◽  
Tapan Sarkar ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Quantum Dots ◽  
Room Temperature ◽  
Graphene Quantum Dots ◽  
Optical Characterization ◽  
Functionalized Graphene ◽  
Transmission Electron ◽  
Sensitivity And Selectivity ◽  
Structural Characterizations

Abstract Here, we report functionalized graphene quantum dots (GQDs) for the optical detection of arsenic at room temperature. GQDs with the fluorescence of three fundamental colors (red, green, and blue) were synthesized and functionally capped with L-cysteine (L-cys) to impart selectively towards As (III) by exploiting the affinity of L-cys towards arsenite. The optical characterization of GQDs was carried out using UV-Vis absorption spectroscopy, Fourier transform infrared spectroscopy, and fluorescence spectrometry and the structural characterizations were performed using transmission electron microscopy. The fluorescence results showed instantaneous quenching in intensity when the GQDs came in contact with As (III) for all test concentrations over a range from 0.025 ppb to 25 ppb, which covers the permissible limit of arsenic in drinking water. The experimental results suggested excellent sensitivity and selectivity towards As (III).

InAs Quantum Dots in AlAs/GaAs Short Period Superlattices: Structure, Optical Characteristics and Laser Diodes

2001 ◽  
Vol 707 ◽  
Author(s):  
Vadim Tokranov ◽  
M. Yakimov ◽  
A. Katsnelson ◽  
K. Dovidenko ◽  
R. Todt ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Room Temperature ◽  
Threshold Current ◽  
Threshold Current Density ◽  
Inas Quantum Dots ◽  
Transmission Electron ◽  
Short Period ◽  
Short Period Superlattices ◽  
Emitting Lasers ◽  
Cladding Layers

ABSTRACTThe influence of two monolayer - thick AlAs under- and overlayers on the formation and properties of self-assembled InAs quantum dots (QDs) has been studied using transmission electron microscopy (TEM) and photoluminescence (PL). Single sheets of InAs QDs were grown inside a 2ML/8ML AlAs/GaAs short-period superlattice with various combinations of under- and overlayers. It was found that 2.4ML InAs QDs with GaAs underlayer and 2ML AlAs overlayer exhibited the lowest QD surface density of 4.2x1010 cm-2 and the largest QD lateral size of about 19 nm as compared to the other combinations of cladding layers. This InAs QD ensemble has also shown the highest room temperature PL intensity with a peak at 1210 nm and the narrowest linewidth, 34 meV. Fabricated edge-emitting lasers using triple layers of InAs QDs with AlAs overlayer demonstrated 120 A/cm2 threshold current density and 1230 nm emission wavelength at room temperature. Excited state QD lasers have shown high thermal stability of threshold current up to 130°C.

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 Erratum: “Narrow luminescence lines from self-assembled CdSe quantum dots at room temperature” [Appl. Phys. Lett. 78, 297 (2001)]

2001 ◽  
Vol 78 (23) ◽  
pp. 3749-3749
Author(s):  
Z. H. Zheng ◽  
K. Okamoto ◽  
H. C. Ko ◽  
Y. Kawakami ◽  
Sg. Fujita
Keyword(s):  
Quantum Dots ◽  
Room Temperature ◽  
Cdse Quantum Dots ◽  
Self Assembled

Enhancement of Photoluminescence from Organic and Inorganic Surface Passivated ZnS Quantum Dots

2001 ◽  
Vol 667 ◽  
Author(s):  
Hatim Mohamed El-Khair ◽  
Ling Xu ◽  
Mingha Li ◽  
Yi Ma ◽  
Xinfan Huang ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Organic Coating ◽  
Band Edge ◽  
Band Edge Emission ◽  
Trap States ◽  
Edge Enhancement ◽  
Edge Emission ◽  
Inorganic And Organic

ABSTRACTZnS quantum dots (QDs) chemically synthesized in PVP stabilizing medium have been coated with Zn(OH)2, SiO2and polystyrene (PS) shells as inorganic and organic passivation agents. to synthesize ZnS/Zn(OH)2, ZnS/SiO2and ZnS/PS QDs. PL properties of inorganically passivated ZnS/Zn(OH)2 and ZnS/SiO2 had reported band edge enhancement of 8-10 times, while organically passivated ZnS/PS QDs exhibit tremendous enhancement of band edge emission as much as 10-15 times,. Therefore inorganic and organic coating can passivate trap states of different energies on the surface of ZnS QDs.

Vapour Sensitivity of InP Surface Quantum Dots

2014 ◽  
Vol 605 ◽  
pp. 177-180 ◽  
Author(s):  
Roberta de Angelis ◽  
Mauro Casalboni ◽  
Liliana D’Amico ◽  
Fabio de Matteis ◽  
Fariba Hatami ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Room Temperature ◽  
Near Infrared ◽  
Surface Recombination ◽  
Surface States ◽  
Infrared Emission ◽  
Polar Solvents ◽  
Solvent Type ◽  
Near Infrared Emission ◽  
Inp Surface

We studied the effect of solvent vapours on the photoluminescent emission of self-assembled InP surface quantum dots (SQDs). Their room temperature near infrared emission undergoes a fully reversible intensity enhancement when the dots were exposed to vapours of polar solvents since polar molecules are likely to be adsorbed onto intrinsic surface states and thus reducing non radiative surface recombination. The shape and position of the emission band does not change. The observed effect is dependent on solvent type and concentration with linear law over a limited concentration range.

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