Selective Microwave Absorption by Trioctyl Phosphine Selenide: Does It Play a Role in Producing Multiple Sized Quantum Dots in a Single Reaction?

2009 ◽  
Vol 21 (13) ◽  
pp. 2770-2776 ◽  
Author(s):  
Aaron L. Washington, ◽  
Geoffrey F. Strouse
Keyword(s):  
Quantum Dots ◽  
Microwave Absorption ◽  
Phosphine Selenide ◽  
Single Reaction

A Critical Investigation on the Existence of Selective Microwave Absorption in the Synthesis of CdSe Quantum Dots

2014 ◽  
Vol 67 (9) ◽  
pp. 1180 ◽  
Author(s):  
Mojtaba Mirhosseini Moghaddam ◽  
C. Oliver Kappe
Keyword(s):  
Quantum Dots ◽  
Microwave Absorption ◽  
Transmission Electron Microscopy Data ◽  
Microwave Assisted Synthesis ◽  
Cdse Quantum Dots ◽  
X Ray Diffraction ◽  
Heating And Cooling ◽  
Transmission Electron ◽  
Microscopy Data ◽  
Heating Mode

The existence of selective microwave absorption phenomena in the synthesis of CdSe quantum dots has been investigated. These types of microwave effects involving selective microwave absorption by specific reagents have recently been proposed in the microwave-assisted synthesis of various nanoparticles. In the present study, the microwave synthesis of CdSe quantum dots was investigated according to a protocol published by Washington and Strouse to clarify the presence of selective microwave heating. Importantly, control experiments involving conventional conductive heating were executed under otherwise (except for the heating mode) identical conditions, ensuring the same heating and cooling profiles, stirring rates, and reactor geometries. Comparison of powder X-ray diffraction, UV-vis, photoluminescence, and transmission electron microscopy data of the obtained CdSe quantum dots reveals that identical types of nanoparticles are obtained independently of the heating mode. Therefore, no evidence for a selective microwave absorption phenomenon could be obtained.

Electrostatic self-assembly synthesis of ZnFe2O4 quantum dots (ZnFe2O4@C) and electromagnetic microwave absorption

2019 ◽  
Vol 179 ◽  
pp. 107417 ◽  
Author(s):  
Zhenguo Gao ◽  
Binghui Xu ◽  
Mingliang Ma ◽  
Ailing Feng ◽  
Yi Zhang ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Microwave Absorption ◽  
Self Assembly

Graphene quantum dots interfacial-decorated hierarchical Ni/PS core/shell nanocapsules for tunable microwave absorption

2020 ◽  
Vol 848 ◽  
pp. 156529 ◽  
Author(s):  
Nan Lyu ◽  
Jiaheng Wang ◽  
Hongjiang Shen ◽  
Zhiyong Bao ◽  
Yong Zhang ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Microwave Absorption ◽  
Graphene Quantum Dots ◽  
Core Shell ◽  
Tunable Microwave

Analyzing reactions of single mechanoenzyme molecules by light microscopy

1992 ◽  
Vol 50 (1) ◽  
pp. 426-427
Author(s):  
Jeff Gelles
Keyword(s):  
Image Processing ◽  
Reaction Mechanisms ◽  
Transient State ◽  
Nanometer Scale ◽  
Reaction Intermediates ◽  
Enzyme Molecule ◽  
Directed Movement ◽  
Enzyme Molecules ◽  
Individual Enzyme ◽  
Single Reaction

Mechanoenzymes are enzymes which use a chemical reaction to power directed movement along biological polymer. Such enzymes include the cytoskeletal motors (e.g., myosins, dyneins, and kinesins) as well as nucleic acid polymerases and helicases. A single catalytic turnover of a mechanoenzyme moves the enzyme molecule along the polymer a distance on the order of 10−9 m We have developed light microscope and digital image processing methods to detect and measure nanometer-scale motions driven by single mechanoenzyme molecules. These techniques enable one to monitor the occurrence of single reaction steps and to measure the lifetimes of reaction intermediates in individual enzyme molecules. This information can be used to elucidate reaction mechanisms and determine microscopic rate constants. Such an approach circumvents difficulties encountered in the use of traditional transient-state kinetics techniques to examine mechanoenzyme reaction mechanisms.

Nanostructure of semiconductor quantum dots in a borosilicate glass matrix by complementary use of HREM and AEM

1990 ◽  
Vol 48 (4) ◽  
pp. 728-729
Author(s):  
M.J. Kim ◽  
L.C. Liu ◽  
S.H. Risbud ◽  
R.W. Carpenter
Keyword(s):  
Quantum Dots ◽  
Borosilicate Glass ◽  
Glass Matrix ◽  
Optical Switching ◽  
Response Times ◽  
Fast Response ◽  
Processing Technique ◽  
Internal Stresses ◽  
Electron Hole ◽  
Spatial Dimensions

When the size of a semiconductor is reduced by an appropriate materials processing technique to a dimension less than about twice the radius of an exciton in the bulk crystal, the band like structure of the semiconductor gives way to discrete molecular orbital electronic states. Clusters of semiconductors in a size regime lower than 2R {where R is the exciton Bohr radius; e.g. 3 nm for CdS and 7.3 nm for CdTe) are called Quantum Dots (QD) because they confine optically excited electron- hole pairs (excitons) in all three spatial dimensions. Structures based on QD are of great interest because of fast response times and non-linearity in optical switching applications.In this paper we report the first HREM analysis of the size and structure of CdTe and CdS QD formed by precipitation from a modified borosilicate glass matrix. The glass melts were quenched by pouring on brass plates, and then annealed to relieve internal stresses. QD precipitate particles were formed during subsequent "striking" heat treatments above the glass crystallization temperature, which was determined by differential thermal analysis.

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