Enhanced Multiexciton Emission Property in Gradient Alloy Core/Shell CdZnSeS/ZnS Quantum Dots: Balance between Surface Passivation and Strain-Induced Lattice Defect

2021 ◽  
Author(s):  
Hongyu Yang ◽  
Lei Zhang ◽  
Ying Tang ◽  
Wenbin Xiang ◽  
Xiaoyong Wang ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Surface Passivation ◽  
Lattice Defect ◽  
Emission Property ◽  
Core Shell

Balancing Electron Transfer and Surface Passivation in Gradient CdSe/ZnS Core–Shell Quantum Dots Attached to ZnO

2013 ◽  
Vol 4 (11) ◽  
pp. 1760-1765 ◽  
Author(s):  
Mohamed Abdellah ◽  
Karel Žídek ◽  
Kaibo Zheng ◽  
Pavel Chábera ◽  
Maria E. Messing ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Electron Transfer ◽  
Surface Passivation ◽  
Core Shell

Characterization of Shell Material on Colloidal CdSe/ZnS Quantum Dots

2004 ◽  
Vol 818 ◽  
Author(s):  
Zhiheng Yu ◽  
Li Guo ◽  
Hui Du ◽  
Todd Krauss ◽  
John Silcox
Keyword(s):  
Quantum Dots ◽  
Surface Passivation ◽  
Core Shell ◽  
Shell Material ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Chemical Distribution ◽  
Electron Energy Loss

AbstractScanning transmission electron microscopy (STEM) coupled with electron energy loss spectroscopy (EELS) was used to determine the distribution of ZnS shell material on colloidal core-shell CdSe/ZnS quantum dots (QDs). A sub-nm electron probe was placed at various locations on core-shell QDs to ascertain the chemical distribution of the shell material. While a definite shell of ZnS was detected surrounding the CdSe core, the integrated EELS signals from positions around the QD suggest the distribution of the shell material may not be uniform. A non-uniform shell implies a reduced quality of the QD surface passivation.

scholarly journals Combining HR-TEM and XPS to elucidate the core–shell structure of ultrabright CdSe/CdS semiconductor quantum dots

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Florian Weigert ◽  
Anja Müller ◽  
Ines Häusler ◽  
Daniel Geißler ◽  
Dieter Skroblin ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Quantum Yield ◽  
Photoelectron Spectroscopy ◽  
Surface Passivation ◽  
Semiconductor Quantum Dots ◽  
Optical Measurements ◽  
Core Shell ◽  
Shell Nanoparticles ◽  
X Ray ◽  
The Core

AbstractControlling thickness and tightness of surface passivation shells is crucial for many applications of core–shell nanoparticles (NP). Usually, to determine shell thickness, core and core/shell particle are measured individually requiring the availability of both nanoobjects. This is often not fulfilled for functional nanomaterials such as many photoluminescent semiconductor quantum dots (QD) used for bioimaging, solid state lighting, and display technologies as the core does not show the application-relevant functionality like a high photoluminescence (PL) quantum yield, calling for a whole nanoobject approach. By combining high-resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS), a novel whole nanoobject approach is developed representatively for an ultrabright oleic acid-stabilized, thick shell CdSe/CdS QD with a PL quantum yield close to unity. The size of this spectroscopically assessed QD, is in the range of the information depth of usual laboratory XPS. Information on particle size and monodispersity were validated with dynamic light scattering (DLS) and small angle X-ray scattering (SAXS) and compared to data derived from optical measurements. In addition to demonstrating the potential of this novel whole nanoobject approach for determining architectures of small nanoparticles, the presented results also highlight challenges faced by different sizing and structural analysis methods and method-inherent uncertainties.

scholarly journals Synthesis and Optical Properties of Thiol Functionalized CdSe/ZnS (Core/Shell) Quantum Dots by Ligand Exchange

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Huaping Zhu ◽  
Michael Z. Hu ◽  
Lei Shao ◽  
Kui Yu ◽  
Reza Dabestani ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Ligand Exchange ◽  
Surface Passivation ◽  
Emission Spectra ◽  
Trioctylphosphine Oxide ◽  
Core Shell ◽  
Initial Surface ◽  
Cdse Core ◽  
Surface Modified

The colloidal photoluminescent quantum dots (QDs) of CdSe (core) and CdSe/ZnS (core/shell) were synthesized at different temperatures with different growth periods. Optical properties (i.e., UV/Vis spectra and photoluminescent emission spectra) of the resulting QDs were investigated. The shell-protected CdSe/ZnS QDs exhibited higher photoluminescent (PL) efficiency and stability than their corresponding CdSe core QDs. Ligand exchange with various thiol molecules was performed to replace the initial surface passivation ligands, that is, trioctylphosphine oxide (TOPO) and trioctylphosphine (TOP), and the optical properties of the surface-modified QDs were studied. The thiol ligand molecules in this study included 1,4-benzenedimethanethiol, 1,16-hexadecanedithiol, 1,11-undecanedithiol, biphenyl-4,4′-dithiol, 11-mercapto-1-undecanol, and 1,8-octanedithiol. After the thiol functionalization, the CdSe/ZnS QDs exhibited significantly enhanced PL efficiency and storage stability. Besides surface passivation effect, such enhanced performance of thiol-functionalized QDs could be due to cross-linked assembly formation of dimer/trimer clusters, in which QDs are linked by dithiol molecules. Furthermore, effects of ligand concentration, type of ligand, and heating on the thiol stabilization of QDs were also discussed.

Surface passivation assisted lasing emission in the quantum dots doped cholesteric liquid crystal resonating cavity with polymer template

RSC Advances ◽  
2014 ◽  
Vol 4 (95) ◽  
pp. 52804-52807 ◽  
Author(s):  
Lin-Jer Chen ◽  
Chia-Rong Lee ◽  
Chung-Liang Chu
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Liquid Crystal ◽  
Surface Passivation ◽  
Cholesteric Liquid Crystal ◽  
Core Shell ◽  
Polymer Template

A copolymer has been used as a template for enhanced optical properties of core–shell CdS/ZnSe quantum dots doped cholesteric liquid crystal.

High-Temperature Synthesis of CdSe-Based Core/Shell, Core/Shell/Shell, and Core/Graded-Shell Nanoplatelets for Stable and Efficient Narrowband Emitters

2019 ◽  
Author(s):  
Aurelio A. Rossinelli ◽  
Henar Rojo ◽  
Aniket S. Mule ◽  
Marianne Aellen ◽  
Ario Cocina ◽  
...  
Keyword(s):  
Quantum Dots ◽  
High Temperature ◽  
Equilibrium Shape ◽  
Size Variation ◽  
Crystal Defects ◽  
Atomic Scale ◽  
Quantum Yields ◽  
Core Shell ◽  
Compositional Gradient ◽  
High Quality

<div>Colloidal semiconductor nanoplatelets exhibit exceptionally narrow photoluminescence spectra. This occurs because samples can be synthesized in which all nanoplatelets share the same atomic-scale thickness. As this dimension sets the emission wavelength, inhomogeneous linewidth broadening due to size variation, which is always present in samples of quasi-spherical nanocrystals (quantum dots), is essentially eliminated. Nanoplatelets thus offer improved, spectrally pure emitters for various applications. Unfortunately, due to their non-equilibrium shape, nanoplatelets also suffer from low photo-, chemical, and thermal stability, which limits their use. Moreover, their poor stability hampers the development of efficient synthesis protocols for adding high-quality protective inorganic shells, which are well known to improve the performance of quantum dots. <br></div><div>Herein, we report a general synthesis approach to highly emissive and stable core/shell nanoplatelets with various shell compositions, including CdSe/ZnS, CdSe/CdS/ZnS, CdSe/Cd<sub>x</sub>Zn<sub>1–x</sub>S, and CdSe/ZnSe. Motivated by previous work on quantum dots, we find that slow, high-temperature growth of shells containing a compositional gradient reduces strain-induced crystal defects and minimizes the emission linewidth while maintaining good surface passivation and nanocrystal uniformity. Indeed, our best core/shell nanoplatelets (CdSe/Cd<sub>x</sub>Zn<sub>1–x</sub>S) show photoluminescence quantum yields of 90% with linewidths as low as 56 meV (19.5 nm at 655 nm). To confirm the high quality of our different core/shell nanoplatelets for a specific application, we demonstrate their use as gain media in low-threshold ring lasers. More generally, the ability of our synthesis protocol to engineer high-quality shells can help further improve nanoplatelets for optoelectronic devices.</div>

Enhanced Photocurrent Generation in Proton‐Irradiated “Giant” CdSe/CdS Core/Shell Quantum Dots

2019 ◽  
Vol 29 (46) ◽  
pp. 1904501 ◽  
Author(s):  
Chao Wang ◽  
David Barba ◽  
Gurpreet S. Selopal ◽  
Haiguang Zhao ◽  
Jiabin Liu ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Core Shell ◽  
Photocurrent Generation
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