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1

Quantum dots for temperature sensing

Doskaliuk Natalia, Lukan Yuliana, Khalavka Yuriy

Scientiae Radices

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2023

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Vol. 2, Iss. 2

93--111

EN

Quantum dots are three-dimensional nanoparticles of semiconductors with typical sizes ranging from 2 to 10 nm. Due to the quantum confinement effect the energy gap increase with the size decreasing resulting in size-depended and fine-tunable optical characteristics. Besides this, the energy structure of a quantum dot with a certain size is highly sensitive to environmental conditions. These specific properties open a wide range of applications starting from optical and optoelectronic devices and ending with biosensing and life science. Temperature is one of those parameters influencing strongly on the optical properties of semiconductor nanocrystals, which make them promising materials for temperature sensing, more often using a fluorescent response. Compared to the conventional organic dyes already applied in this field, quantum dots exhibit a set of advantages, such as high quantum yield and photostability, long fluorescence lifetime, higher Stokes shift, and ability to surface functionalization with targeted organic molecules aimed to provide them biocompatibility. In this review, we briefly discuss the properties of II-VI and assumingly less toxic I-III-VI quantum dots, mechanisms of temperature-induced fluorescence response, and the feasibility of their practical application in the field of thermal sensing.

2

Versatile semiconductor quantum dots: synthesis, bioconjugation strategies and application

Poddar M., Khurana S., Bose S., Nayak R.

Archives of Materials Science and Engineering

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2023

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Vol. 121, nr 1

25--32

EN

Purpose: The present work aimed to synthesize organic and inorganic quantum dots (QDs) and discuss their bioconjugation strategies. Design/methodology/approach: We have prepared 3 different QDs, organic (Carbon [CQDs]) and inorganic (Cadmium Sulphide [CdS] and Zinc Mercury Selenide [ZnHgSe]) quantum dots (QDs) and bioconjugation through in-situ and ex-situ route. These QDs have been characterized through UV-Vis spectroscopy and photoluminescence (PL) emission spectra. Their surface functional groups have been identified through Fourier-transform infrared (FTIR) spectroscopy. The bioconjugated quantum dots were tested through PL emission shift, Agarose electrophoresis, and Bradford assay technique. Findings: Successful synthesized QDs, and their bioconjugation has been confirmed through the previously listed characterization techniques. There are distinct differences in their emission peak, FTIR spectroscopy, and Bradford assay, which confirms their successful bioconjugation. Research limitations/implications: These bioconjugated QDs are difficult to filter from their unconjugated counterpart. Bioconjugation steps are extremely crucial. Practical implications: These QDs could be utilized for highly effective biolabelling and bioimaging in-vivo as well as in-vitro applications. Originality/value: The synthesis has been majorly modified, and the bioconjugation has been prepared in a novel method. There is limited reported work with this much description of the differences in conjugated and unconjugated QDs.

3

Charakteryzacja morfologii powierzchni warstwy fotoanody oraz warstwy kropek kwantowych na podłożu porowatym w ogniwach fotowoltaicznych III generacji

Kwaśnicki Paweł, Grąz Katarzyna, Gronba-Chyła Anna

Inżynieria Materiałowa

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2022

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Vol. 43, nr 3

9--13

PL

W pracy przedstawiono wyniki badań mających na celu określenie stopnia upakowania struktur niskowymiarowych w postaci kropek kwantowych (QDs) dla podłoży mezoporowatych. Wykorzystanie kropek kwantowych w fotowoltaice pozwala na poprawę efektywności konwersji oraz poszerzenie spektrum absorpcyjnego. Wyzwaniem technologicznym jest zarówno proces depozycji QDs, jak i znalezienie odpowiedniej metody określenia kluczowych parametrów, w tym stopnia upakowania, jednorodności rozmieszczenia QDs czy ich parametrów przestrzennych. W pracy przedstawiono wyniki badań z wykorzystaniem skaningowej mikroskopii elektronowej oraz pomiarów przy użyciu spektroskopii Ramana.

EN

This paper presents the results of a study to determine the packing of low-dimensional structures in the form of quantum dots (QDs) for mesoporous substrates. The use of quantum dots in photovoltaics allows for improved conversion efficiency and broadening of the absorption spectrum. The technological challenge is both the deposition process of the QDs and finding a suitable method to determine key parameters including the degree of packing, homogeneity of QDs distribution or their spatial parameters. In this paper, results from scanning electron microscopy and measurements using Raman spectroscopy are presented.

4

Kubit fizyczny

Romaniuk Ryszard

Elektronika : konstrukcje, technologie, zastosowania

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2021

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Vol. 62, nr 3

20--27

PL

Kubit fizyczny, na potrzeby niniejszych rozważań, można zdefiniować jako izolowany obiekt kwantowy o dwóch statystycznie superponowanych stanach kwantowych, który posiada potencjał aplikacyjny (funkcjonalny) jako kubit logiczny. Czas koherencji kubitu fizycznego (czas życia, czas istnienia w stanie superpozycji) musi być odpowiednio długi, aby umożliwić zastosowania praktyczne. Czas życia kubitu w stanie koherencji jest określony przez procesy dekoherencji środowiskowej. Kubit (logiczny) w obszarze kwantowej teorii informacji jest elementarną jednostką informacji kwantowej, analogiem do skalarnego bitu. W odróżnieniu od unormowanej skalarnej wartości bitu 0 lub 1, kubit jest wektorem unormowanym (ale nie w dwuwymiarowej przestrzeni Euklidesa) w dwuwymiarowej przestrzeni Hilberta o bazie ortonormalnej {|0>, |1>}, q=α|0>+β|1>, gdzie α, β są unormowanymi |α²|+|β²|=1 liczbami zespolonymi i statystycznymi amplitudami stanów kwantowych. W notacji Diraca |0>=[1,0], |1>=[0,1]. Pomiar powoduje kolaps koherentnego stanu kwantowego będącego statystyczną superpozycją stanów składowych do stanu dyskretnego z prawdopodobieństwami |α²| dla stanu |0>, i |β²| dla stanu |1>. Tak zdefiniowany logicznie kubit musi być wykonany fizycznie na realizowalnych, stabilnych, dwupoziomowych obiektach kwantowych. Jako kubity fizyczne stosuje się np. cząstki o spinie ½, elektron, polaryzację pojedynczego fotonu, izolowane pojedyncze atomy neutralne i jony, ale także kubity syntetyczne jak kolorowe centra wakancyjne w kryształach, kropki kwantowe, oraz emergencje kwantowe jak kwazicząstki i kwantowe pobudzenia kolektywne np. plazmoniczne.

EN

The physical qubit, for the purposes of these considerations, can be defined as an isolated quantum object with two statistically superposed quantum states, which has an application (functional) potential as a logical qubit. The coherence time of the physical qubit (lifetime, lifetime in superposition) must be long enough to allow for practical applications. The lifetime of a qubit in a coherence state is determined by the processes of environmental decoherence. The (logical) qubit in the field of quantum information theory is an elementary unit of quantum information, analogous to a scalar bit. Unlike a normalized scalar bit value of 0 or 1, a qubit is a normed vector (but not in a two-dimensional Euclid space), in a two-dimensional Hilbert space with an orthonormal basis {|0>,|1>}, q = α | 0> + β | 1>, where α, β are normalized |α²|+|β²|=1 complex numbers and statistical amplitudes of quantum states. In Dirac notation, |0>=[1,0], |1>=[0,1]. The measurement causes a collapse of a coherent quantum state which is a statistical superposition of the component states to the discrete state with the probabilities |α²| for the state |0>, and |β²| for state |1>. Such a logically defined qubit must be physically realized on stable, two-level quantum objects. Physical qubits are e.g. spin ½ particles, electrons, single photon polarization, isolated neutral atoms, and ions, but also synthetic qubits such as coloured vacancy centres in crystals, quantum dots, and quantum emergencies such as quasiparticles and quantum collective stimulations, e.g. plasmonic.

5

Characterization techniques of sandwich-type TiO₂/QD composites for low-cost quantum dots' solar cell

Kwaśnicki Paweł, Jarzębski Maciej, Kardasz P., Inglot M.

Opto-Electronics Review

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2019

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Vol. 27, No. 2

105--112

EN

There is a high impact of the solar cells on energy manufacturing. For several years the energy efficiency was limited due to base-materials' structural and technological limits. High increase of energy harvesting of solar cells has been observed since the first solar cell based on dye-sensitized colloidal TiO₂ films occurred. One of the most promising solutions are used quantum dots (QD) for light energy conversion. In this paper, we described the use of selected characterization techniques for sandwich-type TiO₂/QD composites for a low-cost quantum dots' solar cell in the point of view of mass manufacturer of solar cells and research and development laboratory. Moreover, the increasing role of Raman spectroscopy and mapping for the TiO₂/QD was presented and compared with other necessity techniques for solar cell investigations such as ellipsometry, atomic force microscopy (AFM), and secondary ion mass spectrometry (SIMS).

6

Synthesis and optical properties of CdSe/CdS core/shell nanocrystals

Gadalla A., Abd El-Sadek M. S., Hamood R.

Materials Science Poland

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2019

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Vol. 37, No. 2

149--157

EN

This paper attempts to describe an effective method for producing a composite of quantum dots consisting of CdSe (core) with CdS (shell). This nanoparticles composite was synthesized from modified organometallic precursors. The sizes of the nanoparticles were estimated from X-ray diffraction data using Debye-Scherer formula and compared with high resolution electron microscopy (HRTEM) and optical spectra. The shape of CdSe/CdS NPs is nearly spherical and revels that the CdS shell with the thickness ~0.6 nm almost fully covers the CdSe core (higher contrast). Using UV-Vis spectroscopy, a systematic red shift in the absorption and emission spectra was observed after the deposition of CdS which confirms the shell growth over the CdSe core. In the CdSe/CdS core/shell structure, the holes are confined to the core, while the electrons are delocalized as a result of similar electron affinities of the core and the shell. The increased time of synthesis resulted in shell thickness increase. The observed properties of prepared CdSe/CdS QDs demonstrate the capability of the nanocomposite for using in the optoelectronics and photonics devices.

7

Modelling of electronic and optical properties of Cu2SnS3 quantum dots for optoelectronics applications

Ahamed M. Irshad, Kumar K. Sathish

Materials Science Poland

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2019

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Vol. 37, No. 1

108--115

EN

Copper tin sulfide (Cu2SnS3) is a unique semiconductor, whose nanocrystals have attracted researchers’ attention for its tunable energy bandgap and wavelength in visible and near infrared range. Quantum dots which are fabricated from this material are highly suitable for optoelectronics and solar cell applications. This paper discusses the tunable energy bandgap, exciton Bohr radius and wavelength range of wurtzite structure of Cu2SnS3quantum dots to assess the opportunity to use them in optoelectronics applications. The considerations show that the mole fraction of copper increases as energy bandgap decreases and tunable energy bandgap of this quantum dot material is inversely proportional to the wavelength.

8

Disorder-induced natural quantum dots in InAs/GaAs nanostructures

Babiński A.

Opto-Electronics Review

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2018

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Vol. 26, No. 1

73--79

EN

Properties of excitons confined to potential fluctuations due to indium distribution in the wetting layer which accompany self-assembled InAs/GaAs quantum dots are reviewed. Spectroscopic studies are summarized including time-resolved photoluminescence and corresponding single-photon emission correlation measurements. The identification of charge states of excitons is presented which is based on results of a theoretical analysis of interactions between the involved carriers. The effect of the dots’ environment on their optical spectra is also shown.

9

Facile synthesis of preformed mixed nano-carbon structure from low rank coal

Manoj B., Raj A. M., Chirayil G. T.

Materials Science Poland

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2018

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Vol. 36, No. 1

14--20

EN

Coal is a natural energy resource which is mainly used for energy production via combustion. Coal has nanocrystals embedded in it, formed during the coalification process, and is an ideal precursor for nano-carbon dots and diamonds. Herein, we report a facile top-down method to synthesise nanodots and diamonds of the size of 5 nm to 10 nm from three different types of coal by simple chemical leaching. TEM analysis revealed the formation of a mixture of carbon dots, graphene layers, and quantum dots in bituminous coal and sub-bituminous coal. Raman analysis confirmed the existence of synthesized nanodiamond and nano-carbon mixed phase with defects associated with it. It is concluded that graphene quantum dots, nanodiamonds, graphene sheets and carbon dots present in coal can be extracted by simple chemical treatment. These structures can be tuned to photoluminescent material for various optoelectronic applications or energy harvesting devices like super capacitors.

10

Kropki kwantowe jako sensory w opakowaniach

Khachatryan K., Khachatryan G., Janik M.

Laboratorium - Przegląd Ogólnopolski

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2018

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nr 4

42--46

PL

Głównymi funkcjami opakowań do żywności są utrzymywanie jakości produktów spożywczych podczas przechowywania i transportu oraz wydłużenie ich okresu przydatności do spożycia poprzez kontrolowanie przenikania wilgoci, gazów i innych lotnych składników. Jednym z ważnych czynników wpływających na walory smakowe i świeżość wybranych produktów spożywczych jest kwasowość. Zmiana właściwości kwasowozasadowych zachodzi m.in. pod wpływem czynników zewnętrznych, temperatury i warunków przechowywania. Celami pracy były synteza biodegradowalnego kompozytu na bazie półsyntetycznego polisacharydu zawierającego kropki kwantowe (ang. Quantum Dots – QDs) CdS i badanie wpływu kwasowości na właściwości optyczne otrzymanego materiału.

EN

The main function of food packaging is maintaining the quality of food products during their storage and transport and increasing their shelf life by controlling the penetration of moisture and gases. One of the important factors affecting the taste and freshness of selected food products is their acidity. Changes in acid-base properties take place due to the influence of external factors, temperature and storage conditions. The aims of this study have been to synthetize a biodegradable composite based on a semi-synthetic polysaccharide containing CdS quantum dots (QDs) and to analyse the influence of acidity on the optical properties of the obtained material.

11

The mixed FEM for analysis of quantum-dot systems based on gradient theory

Sladek Jan, Sladek Vladimir, Repka Miroslav, Hrcek Slavomir

Computer Methods in Materials Science

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2018

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Vol. 18, No. 3

81--89

EN

The QD nanostructures are analyzed under a thermal load. The dimensions of the QDs are of the same order as the material length scale. Therefore, the gradient elasticity theory should be applied to account for the size-dependent behavior of such nano-sized QDs. Since governing equations contain higher order derivatives than in conventional approaches the C1-elements are required for approximation of primary fields in the FEM. The mixed FEM are developed here, where C0 continuous interpolation is applied independently for displacement and displacement gradients. The kinematic constraints between strains and displacements are satisfied by collocation at some cleverly chosen internal points in elements. A unit cell of Indium Arsenide QD in a finite sized Gallium Arsenide (GaAs) substrate is analysed.

12

Struktury tunelowe studnia kwantowa-kropki kwantowe jako ośrodek czynny laserów telekomunikacyjnych

Rudno-Rudziński W.

Przegląd Elektrotechniczny

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2017

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R. 93, nr 8

20--23

PL

Kropki kwantowe mają wiele zalet jako laserowy materiał aktywny, jednak wykorzystanie ich w laserach telekomunikacyjnych wymaga uzyskania bardzo szybkiej modulacji emisji, trudnej do osiągnięcia w układzie czysto kropkowym, z powodu znacznej populacji gorących nośników. Możliwym rozwiązaniem jest zastosowanie hybrydowych struktur tunelowych, w których studnia kwantowa, oddzielona cienką barierą od warstwy kropek, służy jako rezerwuar nośników dostarczanych bezpośrednio do stanu podstawowego. W artykule zaprezentowane są różne układy materiałowe, w których zrealizowany został schemat tunelowy, umożliwiające uzyskanie emisji w zakresie podczerwieni telekomunikacyjnej. Uzupełniajace się techniki spektroskopii optycznej wykorzystane zostały do zbadania własności struktur pod kątem ich zastosowań w laserach. Przedstawione są również wyzwania na drodze do uzyskania lasera wykorzystującego szybkie i wydajne tunelowanie ze studni do kropek.

EN

Quantum dots (QD) offer many advantages as active material for lasers, however in order to take advantage of them in telecom lasers it is necessary to assure high modulation speed, difficult to achieve in purely QD system due to high population of hot carriers. One of feasible solutions is to use hybrid structures, where a quantum well, separated by a thin barrier from QD layer, serves as a reservoir of carriers supplied directly to the ground state. The article presents several material systems used to realise tunnel injection scheme, enabling emission in the telecom infrared range. Complementary optical spectroscopic techniques are employed to investigate the properties of structures in view of laser applications. There are also presented challenges on the way to obtain a laser based on fast and efficient tunneling.

13

Neurotransmitters detection using a fluorescence-based sensor with graphene quantum dots

Baluta S., Cabaj J., Malecha K.

Optica Applicata

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2017

|

Vol. 47, nr 2

225--231

EN

In the paper, the development and performance of an optical sensor for detection of neurotransmitters (dopamine) is presented. The concentration of dopamine is measured basing on fluorescence quenching of graphene quantum dots. In the sensor, the dopamine molecules coat the graphene quantum dots surface – in result, the quenching of fluorescence occurs due to the Förster resonance energy transfer. The changes in fluorescence correspond to specific concentrations of the neurotransmitter in tested samples, so it is possible to accurately determine the concentration of dopamine in the sample.

14

Excitonic quasimolecule consisting of two semiconductor quantum dots

Pokutnyi S.I., Salejda W.

Optica Applicata

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2016

|

Vol. 46, nr 4

629--637

EN

The effect of a significant increase in the binding energy of the singlet ground state of an excitonic quasimolecule consisting of two CdS quantum dots, in comparison with the binding energy of a biexciton in a single crystal of CdS (almost by two orders of magnitude), has been found.

15

Sensing application of an optical fiber dip coated with L-Cystein ethyl ester hydrochloride capped ZnTe quantum dots

Sundaray M., Das C., Tripathy S. K.

Materials Science Poland

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2016

|

Vol. 34, No. 3

665--668

EN

Optical fiber in conjunction with ZnTe quantum dots (QDs) is investigated for sensing application. ZnTe QDs, are synthesized by a simple chemical bottom up approach. Quantum dots are capped with L-Cystein ethyl ester hydrochloride (LEEH), to increase their stability. Then LEEH capped ZnTe QDs, whose size is estimated as 2.29 nm by effective mass approximation (EMA), are dip-coated on a cladding removed optical fiber. Different concentrations of alcohol and ammonia are used to investigate the sensing behavior. It is found that sensitivity of the sensor increases with the use of QDs for both alcohol and ammonia.

16

Quantum dots and their immunochemical applications

Malik A., Kurczewski M., Majak I.

Biotechnology and Food Science

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2016

|

Vol. 80, nr 2

137--149

EN

Quantum dots (QDs) are nanometre size semiconductor crystals which possess unique physical and chemical properties. In recent years they were widely used as signal enhancers in biological analysis, mainly because of their high quantum yield, photostability and long-lasting photoluminescence. Compared to common organic fluorophores QDs exhibit wider absorption spectra (QDs absorb photons when excitation energy exceeds the bandgap), narrow emission wavelengths and high Stoke’s shift which allow usage of several different-coloured QDs in single multiplex assays. QDs’ synthesis can be conducted by top-down or bottomup approach. Both methods of synthesis may lead to surface imperfections which may negatively affect QDs’ optical properties. To avoid this problem surface passivation is required. The most widely used passivation method is to cover the QD’s core with material having larger band gap (ZnS). QDs can be widely used in different applications due to the ease of surface functionalization by means of organic and inorganic molecules (polymers, dendrimers, proteins, antibodies and etc.) by many different approaches like ligand-exchange, silanization, amphiphilic combination and other mechanisms. Functionalized QDs have been used for various purposes in in-vitro and in-vivo imaging, drug delivery, therapeutics and other. However this review is mainly focused on immunochemical applications of QDs such as immunohistochemistry, FLISA, FRET, immunosensors etc. QD-based immunological assays are being used for detection of pathogens, toxins, proteins, metal ions (Hg2+) and allergens. Based on growing rate of QDs’ applications it can be concluded that in the coming years their number is going to increase.

17

Investigation on photoluminescence quenching of CdSe/ZnS quantum dots by organic charge transporting materials

Qu Y., Zhang L., An L., Wei H.

Materials Science Poland

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2015

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Vol. 33, No. 4

709--713

EN

The effect of different organic charge transporting materials on the photoluminescence of CdSe/ZnS core/shell quantum dots has been studied by means of steady-state and time-resolved photoluminescence spectroscopy. With an increase in concentration of the organic charge transporting material in the quantum dots solutions, the photoluminescence intensity of CdSe/ZnS quantum dots was quenched greatly and the fluorescence lifetime was shortened gradually. The quenching efficiency of CdSe/ZnS core/shell quantum dots decreased with increasing the oxidation potential of organic charge transporting materials. Based on the analysis, two pathways in the photoluminescence quenching process have been defined: static quenching and dynamic quenching. The dynamic quenching is correlated with hole transporting from quantum dots to the charge transporting materials.

18

Nanocząstki jako luminescencyjne znaczniki biologiczne

Cichos J., Karbowiak M

LAB Laboratoria, Aparatura, Badania

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2015

|

R. 20, nr 1

22--26

19

Oscylacje elektronowe w układzie złożonym z kropek kwantowych oraz doprowadzeń - analiza numeryczna

Tchórzewski P.

Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska

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2014

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nr 2

20--23

PL

W niniejszej pracy analizowane jest zjawisko oscylacji elektronowych w układzie, który składa się z dwóch kropek kwantowych oraz dwóch doprowadzeń. Elementy te są ze sobą sprzężone szeregowo. Model matematyczny rozważanego systemu opiera się na metodzie równania ruchu dla odpowiednich funkcji korelacyjnych. W obliczeniach uwzględniono oddziaływania kulombowskie pomiędzy elektronami zlokalizowanymi na kropkach kwantowych oraz spin elektronu. Zbadany został wpływ wybranych parametrów układu na czasową zależność prawdopodobieństwa obsadzenia poziomów energetycznych kropek kwantowych.

EN

Electron oscillations phenomena in a system composed of two quantum dots and two leads coupled in series has been analysed. The mathematical model of the discussed system is based on the equation of motion method for appropriate correlation functions. The Coulomb interactions between electrons localised on quantum dots and electron spin have been take into account in the calculations. The influence of the selected system parameters on a time-dependent probability of quantum dot energy level occupation has been researched.

20

ZnS Cu-doped quantum dots

Ziółczyk P., Miller E., Przybyt M.

Biotechnology and Food Science

|

2014

|

Vol. 78, nr 1

53--69

EN

The paper presents a survey of literature on the structure and optical properties of ZnS and copper ion-doped ZnS quantum dots. The effect of other metal dopants on the spectral properties of ZnS:Cu quantum dots was also considered. The influence of such parameters as dopant concentration, temperature of the synthesis and compounds which form or modify the additional layer on dots on spectral properties of the quantum dots was described. Examples of application of ZnS:Cu quantum dots are also given.