1,096 research outputs found
General specification of the HTS, copper, QD surface and QD volume resonators.
No full text<p>General specification of the HTS, copper, QD surface and QD volume resonators.</p
Engineering the Band Alignment in QD Heterojunction Films via Ligand Exchange
No full textColloidal quantum dots (QDs) allow great flexibility in the design of optoelectronic devices, thanks to their size-dependent optical and electronic properties and the possibility to fabricate thin films with solution-based processing. In particular, in QD-based heterojunctions, the band gap of both components can be controlled by varying the size of the QDs. However, control over the band alignment between the two materials is required to tune the dynamics of carrier transfer across a heterostructure. We demonstrate that ligand exchange strategies can be used to control the band alignment of PbSe and CdSe QDs in a mixed QD solid, shifting it from a type-I to a type-II alignment. The change in alignment is observed in both spectroelectrochemical and transient absorption measurements, leading to a change in the energy of the conduction band edges in the two materials and in the direction of electron transfer upon photoexcitation. Our work demonstrates the possibility to tune the band offset of QD heterostructures via control of the chemical species passivating the QD surface, allowing full control over the energetics of the heterostructure without requiring changes in the QD composition.ChemE/Opto-electronic Material
Hybrid Quantum Well/Quantum Dot Structure for Broad Spectral Bandwidth Emitters
Full text linkThis thesis details a hybrid quantum well (QW)/quantum dot (QD) active element for an application in broadband source.
First of all, a literature review on the fundamentals of optical coherence tomography (OCT) and superluminescent light emitting diodes is provided in Chapter 1. Basic principles of QD formation using molecular beam epitaxy and several experimental techniques are reviewed in Chapter 2.
The first vertically integrated hybrid QW/QD structure for application in broadband light sources is proposed in Chapter 3. Spontaneous emission from both the QW and the QDs resulted in a full width half maximum (FWHM) of 250nm being demonstrated.
In Chapter 4, experimental results on the modal gain and lasing characteristic of hybrid QW/QD laser are described. Due to the contribution from the QD ground state and first excited state, and the lowest energy transition of the QW, the modal gain at room temperature is extended to 300nm. The values for modal gain are further confirmed by simultaneous three state lasing.
The first hybrid QW/QD superluminescent diode is discussed in Chapter 5. High order QW transitions are observed at high current densities. As a result, a 3dB emission spectrum of FWHM linewidth of 289nm centered at ~1200nm with a corresponding power of 2.4mW is achieved.
The origin of high order QW transitions is discussed in Chapter 6. New device designs utilizing a larger number of QD layers with higher areal density and larger state separation is reported in Chapter 7. Chapter 8 summarizes the whole thesis
Quotient Disruption (QD): New Metric of Intelligence
No full textThis is a theoretical framework in cognitive science and strategic modeling. The author is not a medical professional.
En français :
Ce document présente un cadre théorique en sciences cognitives et modélisation stratégique. L'auteur n'est pas un professionnel de santé.
Résumé : Le Quotient de Disruption (QD) et la Loi de l'Inversion
Ce projet introduit le Quotient de Disruption (QD), modélisé par la loi de puissance :
QD=Qs(Qi)^∆
L'exposant ∆ est défini comme le produit de coefficients psychophysiologiques (Q_e, Q_m, Q_f). Contrairement aux modèles psychométriques linéaires classiques, cette formalisation intègre une phase d'inversion critique (∆< 0). Dans cet état (panique, fatigue extrême, auto-sabotage), le potentiel intellectuel (Qi) devient le diviseur de sa propre efficacité. Ce modèle mathématique explique ainsi l'implosion cognitive et la paralysie analytique des hauts potentiels face à des systèmes de friction intense.
English Version
Abstract: The Disruption Quotient (QD) and the Law of Power Inversion
This project introduces the Disruption Quotient (QD), modeled by the power law:
QD=Qs(Qi)^∆
The exponent ∆ is defined as the product of psychophysiological state coefficients (Q_e, Q_m, Q_f). Unlike traditional linear psychometric models, this formalization incorporates a critical inversion phase (∆< 0). In this state (e.g., acute panic, sleep deprivation, or self-sabotage), intellectual potential (Qi) becomes the divisor of its own efficiency. This mathematical model provides a rigorous explanation for cognitive implosion and analytical paralysis observed in high-potential individuals under conditions of intense systemic friction
Intracellular trafficking of PR9/QD complexes.
No full text<p>(A) Trafficking of PR9/QD complexes toward early endosomes. Cells were treated with PR9/QD complexes for 30 min to 5 h and stained with anti-human early endosome antigen 1 protein (EEA1) antibody. Overlaps of green fluorescent QDs and red fluorescent early endosomes are yellow in merged GFP and RFP images. (B) Trafficking of PR9/QD complexes toward lysosomes. Cells were treated with PR9/QD complexes for 30 min to 5 h and stained with LysoTracker DND-99 and Hoechst 33342. (C) Trafficking of PR9/QD complexes toward the nucleus. A549 cells were treated with PR9/QD complexes for 30 min to 5 h and stained with Hoechst 33342. (D) Time course of colocalization of PR9/QD complexes with lysosomes. (E) Time course of colocalization of PR9/QD complexes with nuclei. Significant differences at <i>P</i><0.05 (*) and <i>P</i><0.01 (**) are indicated. Data are presented as mean ± SD from seven independent experiments. Cell morphology is shown as bright-field images. All fluorescent (A) and confocal images (B and C) are shown at a magnification of 600×.</p
Extradiol oxidative cleavage of catechols by ferrous and ferric complexes of 1,4,7-triazacyclononane: Insight into the mechanism of the extradiol catechol dioxygenases
No full textThe major oxygenation product of catechol by dioxygen in the presence of FeCl2 or FeCl3, 1,4,7-triazacyclononane (TACN), and pyridine in methanol is the extradiol cleavage product 2-hydroxymuconic semi-aldehyde methyl ester (Lin, G.; Reid, G.; Bugg, T. D. I-I. J. Chem. Sec. Chem. Commun. 2000, 1119-1120). Under these conditions, extradiol cleavage of a range of 3- and 4-substituted catechols with electron-donating substituents is observed. The reaction shows a preference in selectivity and rate for iron(II) rather than iron(III) for the extradiol cleavage, which parallels the selectivity of the extradiol dioxygenase family. The reaction also shows a high selectivity for the macrocyclic ligand, TACN, over a range of other nitrogen-and oxygen-containing macrocycles. Reaction of anaerobically prepared iron-TACN complexes with dioxygen gave the same product as monitored by UV/vis spectroscopy. KO2 is able to oxidize catechols with both electron-donating and electron-withdrawing substituents, implying a different mechanism for extradiol. cleavage. Saturation kinetics were observed for catechols, which fit the Michaelis-Menten equation to give k(cat)(app) = 4.8 x 10(-3) s(-1) for 3-(2' ,3'-dihydroxyphenyl)propionic acid. The reaction was also found to proceed using monosodium catecholate in the absence of pyridine, but with different product ratios, giving insight into the acid/base chemistry of extradiol cleavage. In particular, extradiol cleavage in the presence of iron(II) shows a requirement for a proton donor, implying a role for an acidic group in the extradiol dioxygenase active site
Quantum dot solar cells and electrochemical doping of QD films
No full textQuantum dots (QDs) are nano-crystal semiconductors (1-100 nm) in which charge carriers (electrons and holes) are confined in all 3 dimensions by potential barriers that cause them to behave differently from conventional bulk semiconductors. QD research in the past decade has progressed rapidly, allowinga deeper understanding of the physics behind the functioning and the effective synthesis of such materials. The wide spread opto-electronic applications of such QD semiconductors in LEDs, lasers, electrochemistry and solar cells with the potential to outperform traditional bulk semiconductors has fuelled inspired research in this field.Quantum dot solar cells (QDSC) are solution-based third generation solar cells that possess the potential to overcome the Shockley-Queisser limit using multiple exciton generation (MEG). The large Bohr radius, wide bandgap tunability and large light absorption coefficients of PbS QDs have made them the most common material used in the absorber layer of such solar cells and shall also be the material used in this thesis. PbS QDs are used in conjunction with an n-type metal oxide to form a heterojunction that enhances charge separation at the interface. ZnO and TiO2 are common metal oxides used for this purpose while different synthesis methods of the same metal has been observed to show different results. While different research groups have used different metal oxide layers, there has been no systematic study on the interaction of the metal oxide layer synthesized by different methods with the absorber layer. Such a study could help improve understanding of the heterojunction interface and shallbe briefly looked into in this thesis. Another area of improvement in device performance is the depletion region across the heterojunction. Varying the doping of the n-type material affects the depletion width which has been explored in the past by adding impurity atoms to the metal oxide. However, theemergence of an alternate method to dope ZnO electrochemically has triggered an interesting novel pathway to integrate doped materials into solar cells. In this thesis, we have successfully fabricated PbS QD solar cells for the first time in TU Delft at the Synthesis lab of the Applied Sciences faculty withpower conversion efficiencies exceeding 5%. Additionally, a systematic study on the absorber layer and the metal oxide layer was also carried out to optimize the device performance and set protocols for any future work. Finally, electrochemical doping of the PbS absorber layer was attempted to developa precise doping mechanism for QD films.Electrical Engineering | Sustainable Energy Technolog
Self-organization of the InGaAs/GaAs quantum dots superlattice
No full textThe mechanism of self-organization of quantum dots (QDs) during the growth of InGaAs/GaAs multilayers on GaAs (1 0 0) was investigated with cross-sectional transmission electron microscopy (XTEM), and double-crystal X-ray diffraction (DCXD). We found that the QDs spacing in the first layer can affect the vertical alignment of QDs. There seems to exist one critical lateral QD spacing, below which merging of QDs with different initial size is found to be the dominant mechanism leading to perfect vertical alignment. Once the critical value of QDs spacing is reached, the InGaAs QDs of the first layer are simply reproduced in the upper layers. The X-ray rocking curve clearly shows two sets of satellite peaks, which correspond to the QDs superlattice, and multi-quantum wells (QW) formed by the wetting layers around QDs
Modeling of Si-QD Solar Cell in MATLAB
Full text linkIn this paper, the modeling and analysis of single bi-layer Si-QD solar cell is addressed. The modeling of solar cell is done in MATLAB. The photo currents are calculated for various Si-QD diameters like 2.5, 3, 3.5 and 4 nm and SiO2 barrier layer thicknesses like 2.5, 2 and 1.5 nm. It has been observed that with the Si-QD diameter, the photo-current increases. On the other hand, photo-current varies conversely with barrier layer thickness due low carrier tunneling probability through barrier.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3100
Transmission electron microscopy (TEM) images of PR9/QD complexes.
No full text<p>(A) Images of PR9/QD complexes and PR9/QD-transduced cells. PR9 peptide was mixed with QDs at a molecular ratio of 60 (left). Cells were treated with PR9/QD complexes; arrows indicate the location of PR9/QD complexes (middle and right). (B–F) Images of PR9/QD-transduced cells. CCP = clathrin-coated pit, EE = early endosome, ER = endoplasmic reticulum, Ly = lysosome, Ma = macropinosome, MP = membrane protrusion, Mt = mitochondrium, N = nucleus, PM = plasma membrane, V = vesicle.</p
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