scholarly journals Time-Resolved Photoluminescence Spectroscopy Evaluation of CdTe and CdTe/CdS Quantum Dots

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Zhimin Yuan ◽  
Ping Yang ◽  
Yongqiang Cao
Keyword(s):  
Quantum Dots ◽  
High Stability ◽  
Room Temperature ◽  
Thioglycolic Acid ◽  
Cds Quantum Dots ◽  
Time Resolved ◽  
Pl Spectra ◽  
Cdte Qds ◽  
Cds Qds ◽  
Time Resolved Photoluminescence

CdTe and CdTe/CdS quantum dots (QDs) were prepared in aqueous solutions using thioglycolic acid as a stabilizing agent. The photoluminescence (PL) wavelength of the QDs depended strongly on the size of CdTe cores and the thickness of CdS shells. Being kept at room temperature for 130 days, the PL wavelength of CdTe and CdTe/CdS QDs was red-shifted. However the red-shifted degree of CdTe QDs is larger than that of CdTe/CdS QDs. The size of CdTe QDs and the thickness of CdS play important roles for the red-shift of PL spectra of CdTe/CdS QDs. In contrast, the full width at half maximum of PL spectra of CdTe and CdTe/CdS QDs almost remained unchanged. This is ascribed to the effects of Cd2+ and TGA in solutions on the growth of CdTe and CdTe/CdS QDs. This associated with the variation of surface state of the QDs during store. The results demonstrate that CdTe/CdS core/shell QDs have high stability compared with CdTe QDs due to a CdS shell.

scholarly journals Enhanced electron spin rotation in CdS quantum dots

2015 ◽  
Vol 17 (38) ◽  
pp. 25278-25282 ◽  
Author(s):  
Yasuaki Masumoto ◽  
Hikaru Umino ◽  
Jianhui Sun ◽  
Eri Suzumura
Keyword(s):  
Quantum Dots ◽  
Electron Spin ◽  
Faraday Rotation ◽  
Room Temperature ◽  
Spin Rotation ◽  
Cds Quantum Dots ◽  
Time Resolved ◽  
Cds Qds

We studied the spin rotation of electrons in CdS quantum dots (QDs) and CdS QDs with charge acceptors by means of time-resolved Faraday rotation (TRFR) at room temperature.

Effect of Cores on Photoluminescence of Hybrid SiO2-Coated CdTe Quantum Dots

2020 ◽  
Vol 20 (9) ◽  
pp. 5478-5485
Author(s):  
Cong Xie ◽  
Yubin Zhao ◽  
Yuxiang Song ◽  
Yingjie Liu ◽  
Yaya Wang ◽  
...  
Keyword(s):  
Quantum Dots ◽  
High Stability ◽  
Sol Gel ◽  
Quantum Yields ◽  
Core Shell ◽  
Aqueous Synthesis ◽  
Pl Spectra ◽  
Cdte Qds ◽  
Sol Gel Process ◽  
20 Nm

Compared with conventional semiconductor quantum dots, hybrid SiO2 coated CdTe QDs exhibited high stability, long fluorescent lifetime, high photoluminescence quantum yields, and well biocompatibility. In this paper, CdTe QDs with tunable PL from green to red emitting were prepared by an aqueous synthesis. A sol–gel process resulted in CdTe QDs coated with a hybrid SiO2 shell contained CdS-like clusters to obtain red-shifted PL spectra, increased PL efficiency and high stability. The clusters were formed by the reaction of Cd2+ and S2− ions generated via the decomposition of thioglycolic acid. The clusters around CdTe cores created a core–shell structure which is very similar with traditional semiconductor core–shell QDs. After being coated with a hybrid SiO2 shell, the PL of green-emitting naked CdTe QDs was red-shifted largely (~30 nm) while the PL of yellowemitting CdTe QDs revealed a small red-shifted (~20 nm). Furthermore, The PL of red-emitting naked CdTe QDs was red-shifted much small (less than 10 nm). This phenomenon is ascribed to the change of band gap of CdTe cores with sizes. The red-shift of PL spectra is attributed to the CdS-like clusters around the core rather than the thickness of the hybrid SiO2 shell.

scholarly journals Time-Resolved Spectroscopy of InGaN

2000 ◽  
Vol 5 (S1) ◽  
pp. 803-809
Author(s):  
Milan Pophristic ◽  
Frederick H. Long ◽  
Chuong Tran ◽  
Ian T. Ferguson
Keyword(s):  
Quantum Dots ◽  
Time Scale ◽  
Room Temperature ◽  
Average Distance ◽  
Time Resolved ◽  
Light Emitting ◽  
Potential Fluctuations ◽  
Stretched Exponential ◽  
Time Resolved Photoluminescence ◽  
Kinetics Of

We have used time-resolved photoluminescence (PL), with 400 nm (3.1 eV) excitation, to examine InxGa1−xN/GaN light-emitting diodes (LEDs) before the final stages of processing at room temperature. We have found dramatic differences in the time-resolved kinetics between dim, bright and super bright LED devices. The lifetime of the emission for dim LEDs is quite short, 110 ± 20 ps at photoluminescence (PL) maximum, and the kinetics are not dependent upon wavelength. This lifetime is short compared to bright and super bright LEDs, which we have examined under similar conditions. The kinetics of bright and super bright LEDs are clearly wavelength dependent, highly non-exponential, and are on the nanosecond time scale (lifetimes are in order of 1 ns for bright and 10 ns for super bright LED at the PL max). The non-exponential PL kinetics can be described by a stretched exponential function, indicating significant disorder in the material. Typical values for β, the stretching coefficient, are 0.45 − 0.6 for bright LEDs, at the PL maxima at room temperature. We attribute this disorder to indium alloy fluctuations.From analysis of the stretched exponential kinetics we estimate the potential fluctuations to be approximately 75 meV in the super bright LED. Assuming a hopping mechanism, the average distance between indium quantum dots in the super bright LED is estimated to be 20 Å.

Time-Resolved Spectroscopy of InGaN

1999 ◽  
Vol 595 ◽  
Author(s):  
Milan Pophristic ◽  
Frederick H. Long ◽  
Chuong Tran ◽  
Ian T. Ferguson
Keyword(s):  
Quantum Dots ◽  
Time Scale ◽  
Room Temperature ◽  
Average Distance ◽  
Time Resolved ◽  
Light Emitting ◽  
Potential Fluctuations ◽  
Stretched Exponential ◽  
Time Resolved Photoluminescence ◽  
Kinetics Of

AbstractWe have used time-resolved photoluminescence (PL), with 400 nm (3.1 eV) excitation, to examine InxGa1−xN/GaN light-emitting diodes (LEDs) before the final stages of processing at room temperature. We have found dramatic differences in the time-resolved kinetics between dim, bright and super bright LED devices. The lifetime of the emission for dim LEDs is quite short, 110 ± 20 ps at photoluminescence (PL) maximum, and the kinetics are not dependent upon wavelength. This lifetime is short compared to bright and super bright LEDs, which we have examined under similar conditions. The kinetics of bright and super bright LEDs are clearly wavelength dependent, highly non-exponential, and are on the nanosecond time scale (lifetimes are in order of 1 ns for bright and 10 ns for super bright LED at the PL max). The non-exponential PL kinetics can be described by a stretched exponential function, indicating significant disorder in the material. Typical values for β, the stretching coefficient, are 0.45 – 0.6 for bright LEDs, at the PL maxima at room temperature. We attribute this disorder to indium alloy fluctuations.From analysis of the stretched exponential kinetics we estimate the potential fluctuations to be approximately 75 meV in the super bright LED. Assuming a hopping mechanism, the average distance between indium quantum dots in the super bright LED is estimated to be 20 Å.

Enhanced electrochemiluminescence of CdS quantum dots capped with mercaptopropionic acid activated by EDC for Zika virus detection

The Analyst ◽  
2021 ◽  
Author(s):  
Hui-Jun Zhang ◽  
Jin Zhu ◽  
Ning Bao ◽  
Shou-Nian Ding
Keyword(s):  
Quantum Dots ◽  
Zika Virus ◽  
Virus Detection ◽  
Cds Quantum Dots ◽  
Mercaptopropionic Acid ◽  
Sandwich Type ◽  
Cds Qds

The mechanism of enhanced ECL of MPA@CdS QDs by EDC activation was investigated, and a sandwich-type ECL immunosensor has been designed for Zika virus detection.

scholarly journals Effect of dopant concentration and the role of ZnS shell on optical properties of Sm3+ doped CdS quantum dots

RSC Advances ◽  
2021 ◽  
Vol 11 (14) ◽  
pp. 7961-7971
Author(s):  
N. D. Vinh ◽  
P. M. Tan ◽  
P. V. Do ◽  
S. Bharti ◽  
V. X. Hoa ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Dopant Concentration ◽  
Core Shell ◽  
Cds Quantum Dots ◽  
Cds Qds

The role of samarium (Sm) dopant on the structural, morphological, and optical properties of CdS QDs and CdS/ZnS core/shell QDs was methodically reported.

scholarly journals Photooxidation and Photobleaching of Single CdSe/ZnS Quantum Dots Probed by Room-Temperature Time-Resolved Spectroscopy

2001 ◽  
Vol 105 (35) ◽  
pp. 8281-8284 ◽  
Author(s):  
Wilfried G. J. H. M. van Sark ◽  
Patrick L. T. M. Frederix ◽  
Dave J. Van den Heuvel ◽  
Hans C. Gerritsen ◽  
Ageeth A. Bol ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Room Temperature ◽  
Time Resolved ◽  
Time Resolved Spectroscopy ◽  
Temperature Time

scholarly journals Влияние условий роста и уровня легирования на кинетику люминесценции слоев Ge : Sb, выращенных на кремнии

2020 ◽  
Vol 54 (7) ◽  
pp. 685
Author(s):  
Д.В. Юрасов ◽  
Н.А. Байдакова ◽  
А.Н. Яблонский ◽  
А.В. Новиков
Keyword(s):  
Doping Level ◽  
Room Temperature ◽  
Carrier Lifetime ◽  
Growth Conditions ◽  
Published Data ◽  
Rapid Thermal Anneal ◽  
Time Resolved ◽  
Light Emitting ◽  
Pl Intensity ◽  
Time Resolved Photoluminescence

Light-emitting properties of Ge-on-Si(001) layers doped by Sb were studied by stationary and time-resolved photoluminescence (PL) at room temperature. It was obtained that the PL intensity of n-Ge/Si(001) structures is maximized when the doping level is close to the equilibrium solubility of Sb in Ge (~1019 cm-3) which is in accordance with the previously published data. Time-resolved studies of the direct-related PL signal have shown that both the donor density and the growth conditions of doped layer, in particular, the growth temperature influence the PL kinetics. It was obtained that the increase of doping level leads to the decrease of the characteristic carrier lifetime. Moreover, usage of low growth temperatures which is needed to form the doped n-Ge layers also results in shortening of the carrier lifetime as compared with Ge layers grown at high temperatures. It was found that rapid thermal anneal at proper conditions could partially compensate the above mentioned detrimental effects and lead to the increase of both the PL intensity and carrier lifetime.

scholarly journals Optical and Structural Properties of CdS Quantum Dots Synthesized Using (MW-CBD) Technique

2020 ◽  
pp. 44-52
Author(s):  
Ahmed Ahmed S. Abed ◽  
Sattar J. Kasim ◽  
Abbas F. Abbas
Keyword(s):  
Thin Films ◽  
Quantum Dots ◽  
Room Temperature ◽  
Energy Gap ◽  
Cds Nanoparticles ◽  
Cds Quantum Dots ◽  
Optical Energy Gap ◽  
Glass Substrates ◽  
High Adhesion ◽  
Uv Visible

In the present study, the microwave heating method was used to prepare cadmium sulfide quantum dots CdSQDs films. CdS nanoparticles size average obtained as (7nm). The morphology, structure and composition of prepared CdSQDs were examined using (FE-SEM), (XRD) and (EDX). Optical properties of CdSQDs thin films formed and deposited onto glass substrates have been studied at room temperature using UV/ Visible spectrophotometer within the wavelength of (300-800nm), and Photoluminescence (PL) spectrum. The optical energy gap (Eg) which estimated using Tauc relation was equal (2.6eV). Prepared CdS nanoparticles thin films are free from cracks, pinholes and have high adhesion to substrate.

scholarly journals Citric Acid Capped CdS Quantum Dots for Fluorescence Detection of Copper Ions (II) in Aqueous Solution

Nanomaterials ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 32 ◽  
Author(s):  
Zhezhe Wang ◽  
Xuechun Xiao ◽  
Tong Zou ◽  
Yue Yang ◽  
Xinxin Xing ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Quantum Dots ◽  
Citric Acid ◽  
Limit Of Detection ◽  
Copper Ions ◽  
High Sensitivity ◽  
Fluorescence Sensor ◽  
Cds Quantum Dots ◽  
Detection Range ◽  
Cds Qds

Citric acid capped CdS quantum dots (CA-CdS QDs), a new assembled fluorescent probe for copper ions (Cu2+), was synthesized successfully by a simple hydrothermal method. In this work, the fluorescence sensor for the detection of heavy and transition metal (HTM) ions has been extensively studied in aqueous solution. The results of the present study indicate that the obtained CA-CdS QDs could detect Cu2+ with high sensitivity and selectivity. It found that the existence of Cu2+ has a significant fluorescence quenching with a large red shifted (from greenish-yellow to yellowish-orange), but not in the presence of 17 other HTM ions. As a result, Cu2S, the energy level below the CdS conduction band, could be formed at the surface of the CA-CdS QDs and leads to the quenching of fluorescence of CA-CdS QDs. Under optimal conditions, the copper ions detection range using the synthesized fluorescence sensor was 1.0 × 10‒8 M to 5.0 × 10‒5 M and the limit of detection (LOD) is 9.2 × 10‒9 M. Besides, the as-synthesized CA-CdS QDs sensor exhibited good selectivity toward Cu2+ relative to other common metal ions. Thus, the CA-CdS QDs has potential applications for detecting Cu2+ in real water samples.

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