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.

Development of Low Size Dispersion, High Volume Fraction and Strong Quantum Confined CdSxSe1-x Quantum Dots Embedded in Borosilicate Glass Matrix and Study of their Optical Properties

2007 ◽  
Vol 31 ◽  
pp. 161-163 ◽  
Author(s):  
A. Verma ◽  
P.K. Bhatnagar ◽  
P.C. Mathur ◽  
S. Nagpal ◽  
P.K. Pandey ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Borosilicate Glass ◽  
Quantum Confinement ◽  
Glass Matrix ◽  
Volume Fraction ◽  
High Volume ◽  
High Volume Fraction ◽  
Annealing Duration ◽  
Colored Glass ◽  
Size Dispersion

Quantum Dots (QDs) of CdSxSe1-x embedded in borosilicate glass matrix (BGM) have been grown using colored glass filter (RG695). Double-Step (DS) annealing method was adopted in which nucleation is achieved at a lower temperature (475°C) without any crystallization. To obtain crystallization on these nucleation centers, the annealing temperature is raised to 575°C at which the nucleation rate is negligible. QDs of various average radii and volume fractions are grown by varying the annealing duration from 3 to 11hrs. QDs corresponding to higher annealing duration are found to have low size dispersion (SD) and high volume fraction but weak quantum confinement, while, the QDs corresponding to lower annealing durations have high quantum confinement due to their much lower radii as compare to Bohr exciton radius, their SD is high and volume fraction low. For nonlinear optical applications the SD must be low and volume fraction should be high. Attempt has been made to optimize the two parameters. Further it has been concluded that there is no contribution of the band edge recombination to the PL and the origin of the PL is due to shallow traps existing in the volume of the QDs. Studies of absorption and PL have also been made on the samples aged for 18, 24 and 36 months. It is found that the effect of aging is to increase the absorption coefficient, reduce the shallow trap centers and reduce the SD.

Donor–acceptor copolymers containing bithiophene and dithiophenylthienothiadiazole units with fast electrochromic response

2019 ◽  
Vol 7 (28) ◽  
pp. 8575-8584 ◽  
Author(s):  
Věra Cimrová ◽  
Drahomír Výprachtický ◽  
Veronika Pokorná
Keyword(s):  
Optical Switching ◽  
Response Times ◽  
Fast Response ◽  
Donor Acceptor

New copolymers exhibit interesting electrochromic behaviour with fast response times and they are of interest for optical switching.

Study of optical absorption and photoluminescence of quantum dots of CdS formed in borosilicate glass matrix

2009 ◽  
Vol 79 (6) ◽  
pp. 065601 ◽  
Author(s):  
Jitender Kumar ◽  
A Verma ◽  
P K Pandey ◽  
P K Bhatnagar ◽  
P C Mathur ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Optical Absorption ◽  
Borosilicate Glass ◽  
Glass Matrix

Copper Quantum Dots Formation in a Borosilicate Glass

2015 ◽  
Vol 32 ◽  
pp. 66-70
Author(s):  
Jian Zhang ◽  
Jia Wei Sheng
Keyword(s):  
Quantum Dots ◽  
Borosilicate Glass ◽  
Glass Matrix ◽  
Optical Devices ◽  
Cu Nanoparticles ◽  
Characteristic Absorption Band ◽  
Mean Size ◽  
New Type ◽  
Thermal Annealing Process ◽  
The Mean

This Borosilicate glass offers superior properties to the ordinary silicate glass. Metallic quantum dots embedded in glass are promising materials which can be used in modern optical devices. However, the introduction of metallic quantum dots into borosilicate glass has not been studied. We investigated the formation of copper quantum dots in Cu-doped borosilicate glass matrix using thermal annealing process. The reductant SnO included in borosilicate glass played an important role in the formation of the metallic quantum dots. Specifically, Cu quantum dots were formed only when SnO content reached at least 0.5 wt% after borosilicate glass was heated at 600 °C for 60min, which was evidenced by the detection of the characteristic absorption band at about 560nm originated from the surface plasmon resonance of Cu nanoparticles. The optimal concentration of SnO was found to be 1.5 wt% and the mean size for the heating-induced Cu quantum dots was calculated to be ~1.7 nm. Our data offer a simple approach to prepare the metallic quantum dots in borosilicate glass matrix and suggest a new type of metallic quantum dots for applications where superior durability, chemical and heat resistance are required.

scholarly journals Coupling Metallic Nanostructures to Thermally Responsive Polymers Allows the Development of Intelligent Responsive Membranes

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
J. Rubén Morones-Ramírez
Keyword(s):  
Optical Switching ◽  
Response Times ◽  
Composite Membranes ◽  
Fast Response ◽  
Polymer Chains ◽  
Metal Nanoparticle ◽  
Porous Membranes ◽  
Specific Chemical ◽  
Responsive Polymers ◽  
Responsive Membranes

Development of porous membranes capable of controlling flow or changing their permeability to specific chemical entities, in response to small changes in environmental stimuli, is an area of appealing research, since these membranes present a wide variety of applications. The synthesis of these membranes has been mainly approached through grafting of environmentally responsive polymers to the surface walls of polymeric porous membranes. This synergizes the chemical stability and mechanical strength of the polymer membrane with the fast response times of the bonded polymer chains. Therefore, different composite membranes capable of changing their effective pore size with environmental triggers have been developed. A recent interest has been the development of porous membranes responsive to light, since these can achieve rapid, remote, noninvasive, and localized flow control. This work describes the synthesis pathway to construct intelligent optothermally responsive membranes. The method followed involved the grafting of optothermally responsive polymer-metal nanoparticle nanocomposites to polycarbonate track-etched porous membranes (PCTEPMs). The nanoparticles coupled to the polymer grafts serve as the optothermal energy converters to achieve optical switching of the pores. The results of the paper show that grafting of the polymer andin situsynthesis of the metallic particles can be easily achieved. In addition, the composite membranes allow fast and reversible switching of the pores using both light and heat permitting control of fluid flow.

Compact and efficient gas diffusion electrodes based on nanoporous alumina membranes for microfuel cells and gas sensors

The Analyst ◽  
2020 ◽  
Vol 145 (1) ◽  
pp. 122-131 ◽  
Author(s):  
Wanda V. Fernandez ◽  
Rocío T. Tosello ◽  
José L. Fernández
Keyword(s):  
Response Times ◽  
Hydrogen Oxidation ◽  
Fast Response ◽  
Gas Diffusion ◽  
Limiting Current ◽  
Gas Diffusion Electrodes ◽  
Nanoporous Alumina ◽  
Alumina Membranes ◽  
Current Densities ◽  
Microfuel Cells

Gas diffusion electrodes based on nanoporous alumina membranes electrocatalyze hydrogen oxidation at high diffusion-limiting current densities with fast response times.

Excitonic quasimolecules containing of two quantum dots

2016 ◽  
pp. 4024-4028 ◽  
Author(s):  
Sergey I. Pokutnyi ◽  
Wlodzimierz Salejda
Keyword(s):  
Quantum Dots ◽  
Binding Energy ◽  
Exchange Interaction ◽  
Coulomb Interaction ◽  
Silicate Glass ◽  
Glass Matrix ◽  
Silicate Glass Matrix

The possibility of occurrence of the excitonic  quasimolecule formed of spatially separated electrons and holes in a nanosystem that consists  of  CuO quantum dots synthesized in a silicate glass matrix. It is shown that the major contribution to the excitonic quasimolecule binding energy is made by the energy of the exchange interaction of electrons with holes and this contribution is much more substantial than the contribution of the energy of Coulomb interaction between the electrons and holes.

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