Synthesis and Characterization of the Core-Shell CdTe/ZnS Quantum Dots

2009 ◽  
Vol 60-61 ◽  
pp. 165-169 ◽  
Author(s):  
Shi Chao Xu ◽  
Cui Cui Yao ◽  
Ji Mei Zhang ◽  
Zhao Dai ◽  
Guo Zheng ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Colloidal Particles ◽  
Resonance Energy ◽  
Quantum Yields ◽  
Diagnostic Process ◽  
Core Shell ◽  
The Core ◽  
Average Size ◽  
Cdte Core

Core-shell quantum dots are colloidal particles consisting of a semiconductor core and a shell material as an outer coating layer. It can be utilized to develop sensitive methods for the detection of specific biological entities, such as microbial species, their transcription products, and single genes etc. The goal of current research is to synthesize CdTe and core-shell CdTe/ZnS quantum dots (QDs) with an improved process, and to investigate their properties. Well-dispersed CdTe core was prepared in aqueous phase with using 3-mercaptopropionic acid (MPA) as stabilizer under conditions of pH 9.1, temperature of 100 °C, refluxing for 6h, and mol ratio of Cd2+/Te2-/MPA is 1:0.5:2.4. Average size of 8 nm CdTe core was conformed via transmission electron microscopy (TEM). Core-shell CdTe/ZnS QDs were then synthesized to improve the optical properties and biocompatibility of CdTe core. Various conditions were researched to obtain the core-shell QDs with the best optical properties, such as quantum yields, fluorescence intensity etc. The results indicated that the core-shell qualified CdTe/ZnS was prepared under conditions of pH 9.0, temperature of 45 °C, refluxing for 1h, and mol ratio of CdTe/S2-/Zn2+ is 4/1/1. CdTe/ZnS with average size of 10 nm were achieved and conformed via TEM. Moreover, red shift of a maximum emission wavelength from 547 nm of CdTe to 587 of CdTe/ZnS was observed via fluorescence spectrum (FS), which inferred the growth of QDs and formation of ZnS shells. The achieved ZnS shell make CdTe core less toxic and more biocompatible, it will be useful in biological labeling, diagnostic process and biosensing system based on fluorescence resonance energy transition (FRET).

An Enhanced Luminescent CdTe/ZnS Core-Shell Quantum Dot: Synthesis, Characterization, and its Optical Properties

2011 ◽  
Vol 217-218 ◽  
pp. 212-215 ◽  
Author(s):  
Shi Chao Xu ◽  
Yue Qian Yang ◽  
Yan Shan Liu ◽  
Heng Miao ◽  
Mei Dong ◽  
...  
Keyword(s):  
Optical Properties ◽  
Fluorescence Intensity ◽  
Resonance Energy ◽  
Energy Transition ◽  
Core Material ◽  
Quantum Yields ◽  
Core Shell ◽  
Optimum Conditions ◽  
Tem Method ◽  
Average Size

The core-shell CdTe/ZnS quantum dots were prepared with an improved process in aqueous phase. CdTe QDs were synthesized under conditions of pH 9.1, 96 °C, refluxing for 5h, and which was used as core material; ZnS was formed as shell material to enhance the optical properties. Optical properties were characterized with fluorescence spectrum (FS), and morphology of QDs was investigated via transmission electron microscopy (TEM) method. Moreover, composition and formation of CdTe/ZnS core-shell QDs was characterized via x-ray diffraction (XRD) method. Optimum conditions were investigated to obtain the qualified CdTe/ZnS core-shell QDs, the results indicated QDs with high quantum yields and fluorescence intensity were achieved under conditions of pH 9.0, 45 °C, refluxing for 1h, and v/v/v ratio of CdTe/Na2S/ZnSO4 is 4/1/1. The TEM data indicated that average size of 5 nm CdTe core was prepared, and CdTe/ZnS core-shell QDs with average size of 11 nm were achieved under the optimum conditions. ca 30nm of red shift of a maximum emission wavelength from ca 530 nm (CdTe) to 560 nm (CdTe/ZnS) was observed via FS under the optimum conditions, which inferred the growth of QDs and formation of ZnS shells. Furthermore, the enhanced fluorescence intensity of CdTe/ZnS core-shell QDs was detected and over two times of fluorescence intensity was increased after formation of ZnS shell. The obtained QDs will have great potential application in biological researches and biosensing system based on fluorescence resonance energy transition (FRET).

Synthesis of Type-I CdTe Core and Type-II CdTe/CdS Core/Shell Quantum Dots by a Hydrothermal Method and Their Optical Properties

2017 ◽  
Vol 90 (1) ◽  
pp. 52-58 ◽  
Author(s):  
Taichi Watanabe ◽  
Kohji Takahashi ◽  
Kunio Shimura ◽  
Hang-Beom Bu ◽  
Kim Hyeon-Deuk ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Hydrothermal Method ◽  
Core Shell ◽  
Type I ◽  
Type Ii ◽  
Cdte Core

scholarly journals Phonon Characterization, Structural and Optical Properties of Type-II CdSe/CdTe core/shell and Type-II/type-I CdSe/CdTe/ZnS core/shell/shell Quantum Dots

2020 ◽  
Vol 36 (3) ◽  
Author(s):  
Nguyen Xuan Ca ◽  
Nguyen Thi Hien
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Excitation Power ◽  
Cubic Phase ◽  
Core Shell ◽  
Type I ◽  
Type Ii ◽  
X Ray Diffraction ◽  
Cdte Core ◽  
Observation Results

The CdSe, type-II CdSe/CdTe core/shell and type-II/type-I CdSe/CdTe/ZnS core/shell/shell  quantum dots (QDs) were successfully synthesized in a noncoordinating solvent. The phonon characterizations, optical properties and structures of the synthesized QDs were characterized by Raman scattering (RS) spectra, photoluminescence (PL) spectroscopy, PL-decay lifetime, absorption spectroscopy (Abs), and X-ray diffraction (XRD). The growth of QDs was monitored by using RS, which demonstrated the formation of correct of the core/shell and core/shell/shell structures. Observation results from XRD reveal that all QDs crystallize in the cubic phase with zinc-blende structure. The typical characteristics of spatially indirect recombination for type-II QDs were observed through Abs and PL spectroscopy. The ZnS shell significantly enhanced the PL quantum yeild (QY), the optical durability, the chemical stability and separating CdSe/CdTe QDs from the surroundings. The effect of excitation power on the PL properties of the CdSe core,  CdSe/CdTe and CdSe/CdTe/ZnS QDs has been investigated.

scholarly journals The Performance of Active Coated Nanoparticles Based on Quantum-Dot Gain Media

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Sawyer D. Campbell ◽  
Richard W. Ziolkowski
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Quantum Dot ◽  
Relative Size ◽  
Core Shell ◽  
The Core ◽  
Coated Nanoparticles ◽  
Dot Gain ◽  
Band Gap Structure ◽  
Gain Media

Quantum-dots (QDs) provide an exciting option for the gain media incorporated in active coated nanoparticles (CNPs) because they possess large gain coefficients resulting from their extreme confinement effects. The optical properties of core/shell QDs can be tuned by changing the relative size of the core/shell, that is, by effectively changing its band gap structure. Similarly, the resonance of a CNP can be adjusted by changing the relative sizes of its layers. It is demonstrated here that by optimally locating the QDs inside a resonant CNP structure it is possible to greatly enhance the intrinsic amplifying behavior of the combined QD-CNP system.

scholarly journals Optical Properties, Synthesis, and Potential Applications of Cu-Based Ternary or Quaternary Anisotropic Quantum Dots, Polytypic Nanocrystals, and Core/Shell Heterostructures

Nanomaterials ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 85 ◽  
Author(s):  
Xue Bai ◽  
Finn Purcell-Milton ◽  
Yuri Gun’ko
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Stokes Shift ◽  
Current Status ◽  
Quantum Yields ◽  
Core Shell ◽  
Luminescent Solar Concentrators ◽  
Wide Range ◽  
Synthesis Properties ◽  
Potential Applications

This review summaries the optical properties, recent progress in synthesis, and a range of applications of luminescent Cu-based ternary or quaternary quantum dots (QDs). We first present the unique optical properties of the Cu-based multicomponent QDs, regarding their emission mechanism, high photoluminescent quantum yields (PLQYs), size-dependent bandgap, composition-dependent bandgap, broad emission range, large Stokes’ shift, and long photoluminescent (PL) lifetimes. Huge progress has taken place in this area over the past years, via detailed experimenting and modelling, giving a much more complete understanding of these nanomaterials and enabling the means to control and therefore take full advantage of their important properties. We then fully explore the techniques to prepare the various types of Cu-based ternary or quaternary QDs (including anisotropic nanocrystals (NCs), polytypic NCs, and spherical, nanorod and tetrapod core/shell heterostructures) are introduced in subsequent sections. To date, various strategies have been employed to understand and control the QDs distinct and new morphologies, with the recent development of Cu-based nanorod and tetrapod structure synthesis highlighted. Next, we summarize a series of applications of these luminescent Cu-based anisotropic and core/shell heterostructures, covering luminescent solar concentrators (LSCs), bioimaging and light emitting diodes (LEDs). Finally, we provide perspectives on the overall current status, challenges, and future directions in this field. The confluence of advances in the synthesis, properties, and applications of these Cu-based QDs presents an important opportunity to a wide-range of fields and this piece gives the reader the knowledge to grasp these exciting developments.

scholarly journals Ge/Si core/shell quantum dots in alumina: tuning the optical absorption by the core and shell size

Nanophotonics ◽  
2017 ◽  
Vol 6 (5) ◽  
pp. 1055-1062 ◽  
Author(s):  
Nikolina Nekić ◽  
Jordi Sancho-Parramon ◽  
Ivančica Bogdanović-Radović ◽  
Jörg Grenzer ◽  
René Hübner ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Blue Shift ◽  
Core Shell ◽  
Shell Size ◽  
Experimental Realization ◽  
Sputtering Deposition ◽  
The Core ◽  
Theoretical Predictions ◽  
The Matrix

AbstractGe/Si core/shell quantum dots (QDs) recently received extensive attention due to their specific properties induced by the confinement effects of the core and shell structure. They have a type II confinement resulting in spatially separated charge carriers, the electronic structure strongly dependent on the core and shell size. Herein, the experimental realization of Ge/Si core/shell QDs with strongly tunable optical properties is demonstrated. QDs embedded in an amorphous alumina glass matrix are produced by simple magnetron sputtering deposition. In addition, they are regularly arranged within the matrix due to their self-assembled growth regime. QDs with different Ge core and Si shell sizes are made. These core/shell structures have a significantly stronger absorption compared to pure Ge QDs and a highly tunable absorption peak dependent on the size of the core and shell. The optical properties are in agreement with recent theoretical predictions showing the dramatic influence of the shell size on optical gap, resulting in 0.7 eV blue shift for only 0.4 nm decrease at the shell thickness. Therefore, these materials are very promising for light-harvesting applications.

Sequential Structural Degradation of Red Perovskite Quantum Dots and Its Prevention by Introducing Iodide at a Stable Gradient Concentration into the Core–Shell Red Perovskite Quantum Dots

Nanoscale ◽  
2022 ◽  
Author(s):  
Hanleem Lee ◽  
Cuc Kim Trinh ◽  
Mo Geun So ◽  
Chang-Lyoul Lee
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Core Shell ◽  
Next Generation ◽  
Structural Degradation ◽  
The Core ◽  
Perovskite Quantum Dots ◽  
Structural Instabilities

Perovskite quantum dots (QDs) have been extensively studied as emissive materials for next-generation optoelectronics due to their outstanding optical properties; however, their structural instabilities, specifically those of red perovskite QDs,...

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>

scholarly journals Light-Scattering Simulations from Spherical Bimetallic Core–Shell Nanoparticles

Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 359
Author(s):  
Francesco Ruffino
Keyword(s):  
Optical Properties ◽  
Light Scattering ◽  
Bimetallic Nanoparticles ◽  
Dominant Role ◽  
Scattered Light ◽  
Specific Interaction ◽  
Surface Enhanced Raman Spectroscopy ◽  
Localized Surface Plasmon ◽  
Core Shell ◽  
The Core

Bimetallic nanoparticles show novel electronic, optical, catalytic or photocatalytic properties different from those of monometallic nanoparticles and arising from the combination of the properties related to the presence of two individual metals but also from the synergy between the two metals. In this regard, bimetallic nanoparticles find applications in several technological areas ranging from energy production and storage to sensing. Often, these applications are based on optical properties of the bimetallic nanoparticles, for example, in plasmonic solar cells or in surface-enhanced Raman spectroscopy-based sensors. Hence, in these applications, the specific interaction between the bimetallic nanoparticles and the electromagnetic radiation plays the dominant role: properties as localized surface plasmon resonances and light-scattering efficiency are determined by the structure and shape of the bimetallic nanoparticles. In particular, for example, concerning core-shell bimetallic nanoparticles, the optical properties are strongly affected by the core/shell sizes ratio. On the basis of these considerations, in the present work, the Mie theory is used to analyze the light-scattering properties of bimetallic core–shell spherical nanoparticles (Au/Ag, AuPd, AuPt, CuAg, PdPt). By changing the core and shell sizes, calculations of the intensity of scattered light from these nanoparticles are reported in polar diagrams, and a comparison between the resulting scattering efficiencies is carried out so as to set a general framework useful to design light-scattering-based devices for desired applications.

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