Temperature and strain effects on core bandgap and diameter of bare CdSe core and CdSe/ZnS heterostructure core/shell quantum dots

2018 ◽  
Author(s):  
M. Rezaul Karim ◽  
Hilmi Ünlü
Keyword(s):  
Quantum Dots ◽  
Core Shell ◽  
Cdse Core ◽  
Strain Effects

scholarly journals Strain Effects on the Band Gap and Diameter of CdSe Core and CdSe/ZnS Core/Shell Quantum Dots at Any Temperature

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Md. Rezaul Karim ◽  
Mesut Balaban ◽  
Hilmi Ünlü
Keyword(s):  
Quantum Dots ◽  
Band Gap ◽  
Compressive Strain ◽  
Fluorescence Emission ◽  
Core Shell ◽  
Average Particle ◽  
Cdse Core ◽  
Strain Effects ◽  
The Core ◽  
Core Band

We present the results of an experimental study about strain effects on the core band gap and diameter of spherical bare CdSe core and CdSe/ZnS core/shell quantum dots (QDs) synthesized by using a colloidal technique at varying temperatures. Structural characterizations were made by using X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) techniques. Optical characterizations were made by using UV-Vis absorption and fluorescence emission spectroscopies. The XRD analysis suggests that the synthesized bare CdSe core and CdSe/ZnS core/shell QDs have zinc blende crystal structure. HRTEM results indicate that the CdSe core and CdSe/ZnS QDs have average particle sizes about 3.50 nm and 4.84 nm, respectively. Furthermore, compressive strain causes an increase (decrease) in the core band gap (diameter) of spherical CdSe/ZnS core/shell QDs at any temperature. An elastic strain-modified effective mass approximation (EMA) predicts that there is a parabolic decrease (increase) in the core band gap (diameter) of QDs with temperature. The diameter of spherical bare CdSe core and CdSe/ZnS core/shell QDs calculated by using the strain-modified EMA, with core band gap extracted from absorption spectra, are in excellent agreement with the HRTEM data.

Resistive Switching in CdTe/CdSe Core–Shell Quantum Dots Embedded Chitosan-Based Memory Devices

2021 ◽  
Author(s):  
Zolile Wiseman Dlamini ◽  
Sreedevi Vallabhapurapu ◽  
Olamide Abiodun Daramola ◽  
Potlaki Foster Tseki ◽  
Rui Werner Macedo Krause ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Resistive Switching ◽  
Core Shell ◽  
Cdse Core ◽  
Active Layers ◽  
Ag Electrodes ◽  
Exponential Decrease ◽  
Conductive Bridge ◽  
Bipolar Memory ◽  
State Resistance

In this paper, we report on the resistive switching (RS) and conduction mechanisms in devices consisting of CdTe/CdSe core–shell quantum dots embedded chitosan composites active layer. Two devices with active layers sandwiched between (1) Al and Ag, and (2) ITO and Ag electrodes were studied. Both devices exhibited bipolar memory behavior with [Formula: see text] V and [Formula: see text][Formula: see text]V, for the Al-based device, while [Formula: see text] V and [Formula: see text][Formula: see text]V were observed for the ITO-based device, enabling both devices to be operated at low powers. However, the switching mechanisms of both devices were different, i.e., RS in Al device was attributed to conductive bridge mechanism, while space-charge-limited driven conduction filament attributed the switching mechanism of the ITO device. Additionally, the Al-based device showed long retention ([Formula: see text][Formula: see text]s) and a reasonable large ([Formula: see text]) ON/OFF ratio. Additionally, for this device, we also observed sweeping cycle-induced reversal of voltage polarity of the [Formula: see text] and [Formula: see text]. In contrast, we observed that increasing sweeping cycles resulted in an exponential decrease of the OFF-state resistance of the ITO-based device.

Photoluminescence properties of CdTe∕CdSe core-shell type-II quantum dots

2006 ◽  
Vol 99 (12) ◽  
pp. 123521 ◽  
Author(s):  
C. H. Wang ◽  
T. T. Chen ◽  
K. W. Tan ◽  
Y. F. Chen ◽  
C. T. Cheng ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Core Shell ◽  
Type Ii ◽  
Photoluminescence Properties ◽  
Cdse Core ◽  
Shell Type

Insight into Strain Effects on Band Alignment Shifts, Carrier Localization and Recombination Kinetics in CdTe/CdS Core/Shell Quantum Dots

2015 ◽  
Vol 137 (5) ◽  
pp. 2073-2084 ◽  
Author(s):  
Lihong Jing ◽  
Stephen V. Kershaw ◽  
Tobias Kipp ◽  
Sergii Kalytchuk ◽  
Ke Ding ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Band Alignment ◽  
Core Shell ◽  
Carrier Localization ◽  
Strain Effects ◽  
Recombination Kinetics ◽  
Insight Into

Micro-Photoluminescence Study of Bio-conjugated CdSe/ZnS Nanocrystals

2013 ◽  
Vol 1617 ◽  
pp. 157-162
Author(s):  
L. Borkovska ◽  
N. Korsunska ◽  
T. Stara ◽  
O. Kolomys ◽  
V. Strelchuk ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Thermal Annealing ◽  
Interleukin 10 ◽  
Half Width ◽  
Core Shell ◽  
Cdse Core ◽  
Photoluminescence Study ◽  
Pl Spectra ◽  
Band Position ◽  
Zns Nanocrystals

ABSTRACTThe effect of bio-conjugation of CdSe/ZnS core-shell quantum dots (QDs) with Interleukin 10 (IL-10) antibodies on the aging of photoluminescence (PL) spectra of the QDs was investigated. The aging occurred upon storage of QDs for about 2 years or thermal annealing at 190 oC for up to 12 hours at atmospheric ambience and consisted in “blue” shifting the PL band position, increasing a PL band half-width and decreasing the PL intensity. The bio-conjugation is found to promote PL aging. The aging upon storage is attributed to the oxidation that decreases the QD core dimension, while the aging upon thermal annealing can be due to both oxidation and alloying of CdSe core and ZnS shell.

Photoluminescence transformation of core/shell CdSe/ZnS quantum dots at the conjugation to biomolecules

2012 ◽  
Vol 1376 ◽  
Author(s):  
T. V. Torchynska ◽  
I. Ch. Ballardo Rodríguez ◽  
Ye. Shcherbyna
Keyword(s):  
Quantum Dots ◽  
High Energy ◽  
Core Shell ◽  
Polymer Interfaces ◽  
Cdse Core ◽  
Exciton Emission ◽  
Pl Spectra ◽  
Pl Spectrum ◽  
The Comparative Study ◽  
Color Emission

AbstractThe paper presents the results of PL spectrum analysis of CdSe/ZnS QDs covered by PEG polymer with and without bioconjugation to bio-molecules .– the Osteopontin antibodies. Commercial CdSe/ZnS QDs used in the study are characterized by the color emission with the maximum at 640 nm (1.96 eV) at 300K. It is shown that PL spectra of nonconjugated QDs can be presented as a superposition of PL bands related to exciton emission in the CdSe core (1.96 eV) and some high energy PL bands (in the spectral range 2.37 .– 3.00 eV). The comparative study of PL spectrum at high (300K) and low (10K) temperatures has testified that high energy PL bands deal with electronhole emission via interface states at the CdSe/ZnS/polymer interfaces.It is revealed that the QD bioconjugation to the anti Osteopontin antibody is accompanied by the change dramatically in PL spectra. Main features of PL spectrum transformstions deal with decreasing the PL intensity of interface related PL bands and the rise of intensity of CdSe core related PL bands. The explanation of mentioned effects has been proposed on the base of re-charging of interface related states at the bioconjugation process.

scholarly journals Thermally induced atomic reconstruction of PbSe/CdSe core/shell quantum dots into PbSe/CdSe bi-hemisphere hetero-nanocrystals

2011 ◽  
Vol 21 (31) ◽  
pp. 11556 ◽  
Author(s):  
Dominika Grodzińska ◽  
Francesca Pietra ◽  
Marijn A. van Huis ◽  
Daniel Vanmaekelbergh ◽  
Celso de Mello Donegá
Keyword(s):  
Quantum Dots ◽  
Core Shell ◽  
Cdse Core ◽  
Thermally Induced
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