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Littérature scientifique sur le sujet « Doped Nanocrystals »

Auteur : Grafiati

Publié le 9 mars 2023

Mis à jour le 10 mars 2023

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Articles de revues sur le sujet "Doped Nanocrystals"

Della Gaspera, Enrico, Noel W. Duffy, Joel van Embden, Lynne Waddington, Laure Bourgeois, Jacek J. Jasieniak et Anthony S. R. Chesman. « Plasmonic Ge-doped ZnO nanocrystals ». Chemical Communications 51, n^o 62 (2015) : 12369–72. http://dx.doi.org/10.1039/c5cc02429c.

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Zhang, Xinhai, Qiuling Chen et Shouhua Zhang. « Ta2O5 Nanocrystals Strengthened Mechanical, Magnetic, and Radiation Shielding Properties of Heavy Metal Oxide Glass ». Molecules 26, n^o 15 (26 juillet 2021) : 4494. http://dx.doi.org/10.3390/molecules26154494.

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In this study, for the first time, diamagnetic 5d0 Ta5+ ions and Ta2O5 nanocrystals were utilized to enhance the structural, mechanical, magnetic, and radiation shielding of heavy metal oxide glasses. Transparent Ta2O5 nanocrystal-doped heavy metal oxide glasses were obtained, and the embedded Ta2O5 nanocrystals had sizes ranging from 20 to 30 nm. The structural analysis of the Ta2O5 nanocrystal displays the transformation from hexagonal to orthorhombic Ta2O5. Structures of doped glasses were studied through X-ray diffraction and infrared and Raman spectra, which reveal that Ta2O5 exists in highly doped glass as TaO6 octahedral units, acting as a network modifier. Ta5+ ions strengthened the network connectivity of 1–5% Ta2O5-doped glasses, but Ta5+ acted as a network modifier in a 10% doped sample and changed the frame coordination units of the glass. All Ta2O5-doped glasses exhibited improved Vicker’s hardness, magnetization (9.53 × 10−6 emu/mol), and radiation shielding behaviors (RPE% = 96–98.8%, MAC = 32.012 cm2/g, MFP = 5.02 cm, HVL = 0.0035–3.322 cm, and Zeff = 30.5) due to the increase in density and polarizability of the Ta2O5 nanocrystals.

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Chen, Yi Chuan, Yue Hui Hu, Xiao Hua Zhang, Feng Yang, Hai Jun Xu, Xin Hua Chen et Jun Chen. « Structure and Properties of Doped ZnO Nanopowders Synthesized by Methanol Alcoholysis Method ». Advanced Materials Research 287-290 (juillet 2011) : 1406–11. http://dx.doi.org/10.4028/www.scientific.net/amr.287-290.1406.

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Pured ZnO, Al doped ZnO and Al-In co-doped ZnO nanopowders were synthesized by the methanol alcoholysis method at 130 °C. Structure, morphology and optical properties of ZnO nanopowders were characterized using X-ray diffraction, Transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and Photoluminescence (PL) spectra. The results show that ZnO nanopowders can be obtained in methanol solution at low temperature (130 °C). TEM images show that Al doped ZnO nanocrystals grow along the [002] axis quicker than other axes. FTIR spectra show that ZnO nanocrystals synthesized by the methanol alcoholysis include a little organic impurity. PL spectrums reveal that pure ZnO and doped ZnO nanocrystals have a blue band emission at 440 nm and a green band emission at 520 nm and 530 nm, respectively. Compared with the pure ZnO nanocrystal, the Al doping improves the luminescent properties.

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Ishigaki, Takamasa, Ji Guang Li et Yusuke Moriyoshi. « Thermal Plasma Processing of Functional Ceramic Materials ». Advances in Science and Technology 45 (octobre 2006) : 281–84. http://dx.doi.org/10.4028/www.scientific.net/ast.45.281.

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Fe- and Eu-doped TiO2 nanocrystals were synthesized via Ar/O2 thermal plasma oxidation of liquid precursor mists. The use of mists ensures atomic level mixing of the elements and high supersaturation of the evaporated species upon plasma oxidation, which favors nanocrystal formation upon condensation. Iron-doped TiO2 nanopowders with controlled iron to titanium atomic ratios (RFe/Ti) ranging from 0 to 20%, were synthesized by oxidative pyrolysis of liquid-feed metallorganic precursors containing titanium tetra-n-butoxide (TTBO) and ferrocene. Europium doped TiO2 luminescent nanocrystals were also synthesized via RF thermal plasma oxidation of liquid precursor mists containing TTBO and europium nitrate.

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Dong, Hehe, Yinggang Chen, Yan Jiao, Qinling Zhou, Yue Cheng, Hui Zhang, Yujie Lu, Shikai Wang, Chunlei Yu et Lili Hu. « Nanocrystalline Yb:YAG-Doped Silica Glass with Good Transmittance and Significant Spectral Performance Enhancements ». Nanomaterials 12, n^o 8 (8 avril 2022) : 1263. http://dx.doi.org/10.3390/nano12081263.

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In this study, Yb:YAG-nanocrystal-doped silica glass with high transmission and excellent spectral properties was successfully prepared using a modified sol–gel method. The X-ray diffraction (XRD), micro-Raman spectroscopy, electron paramagnetic resonance (EPR), transmission electron microscopy (TEM), and high-resolution TEM (HR-TEM) analyses confirmed that the Yb:YAG nanocrystals, with their low content, homogeneous distribution, and small crystal size, directly crystallized into the silica glass network without annealing treatment. In contrast with conventional microcrystalline glass having large particles (>0.1 μm) and a large particle content, nanocrystalline glass with a homogeneous distribution and sizes of ~22 nm had higher optical transmittance and better spectral properties. Compared with Yb3+ doped silica glass without nanocrystals, the Yb:YAG-nanocrystal-doped silica glass had a 28% increase in absorption cross-section at 975 nm and a 172% enhanced emission cross-section at 1030 nm without any changes in the spectral pattern of the Yb3+ ions in the silica glass. Meanwhile, the Yb:YAG-doped silica glass with large size and high optical quality was easily prepared. Therefore, the Yb:YAG-nanocrystal-doped silica glass is expected to be a promising near-infrared laser material.

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Kang, Myung Jong, Na Hyeon An et Young Soo Kang. « Magnetic and Photochemical Properties of Cu Doped Hematite Nanocrystal ». Materials Science Forum 893 (mars 2017) : 136–43. http://dx.doi.org/10.4028/www.scientific.net/msf.893.136.

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In this report, the magnetic and photochemical properties of Cu doped hematite nanocrystal was investigated intensively. The Cu doped hematite nanocrystals were prepared by hydrothermal method, changing the molar ratio of Cu precursors. The XRD and XPS techniques are used for revealing crystal and chemical state of Cu doped hematite nanocrystal. Raman spectroscopy was also used for confirming Cu atoms replacing Fe position in Cu doped hematite crystal. The UV-vis and UPS were used for assigning electronic band position for photocatalytic properties. Cu doped hematite showed the enhanced photocatalytic properties within photodegradation of methyl orange. Finally, by checking magnetic hysteresis loops of Cu doped hematites with VSM, it was revealed that the magnetic property of Cu doped hematite nanocrystal was increased after doping Cu into hematite nanocrystal, get the distortion of magnetic sub-lattices.

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JACOBY, MITCH. « DOPED NANOCRYSTALS ». Chemical & ; Engineering News 83, n^o 28 (11 juillet 2005) : 9. http://dx.doi.org/10.1021/cen-v083n028.p009.

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Norris, D. J., A. L. Efros et S. C. Erwin. « Doped Nanocrystals ». Science 319, n^o 5871 (28 mars 2008) : 1776–79. http://dx.doi.org/10.1126/science.1143802.

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JAVAN, MASOUD BEZI. « ELECTRONIC AND OPTICAL PROPERTIES OF NITROGEN DOPED SiC NANOCRYSTALS : FIRST PRINCIPLES STUDY ». International Journal of Modern Physics B 27, n^o 13 (15 mai 2013) : 1350053. http://dx.doi.org/10.1142/s0217979213500537.

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A typical nitrogen doped spherical SiC nanocrystal with a diameter of 1.2 nm ( Si 43 C 44 H 76) using linear combination atomic orbital (LCAO) in combination with pseudopotential density functional calculation have been studied. Our selected SiC nanocrystal has been modeled taking all the cubic bulk SiC atoms contained within a sphere of a given radius and terminating the surface dangling bonds with hydrogen atoms. We have examined nine possible situations in which nitrogen has a high probability for replacement in the lattice or placed between atoms in the nanocrystal. We have found that the silicone can substitute with a nitrogen atom in each layer as the constructed nanocrystals remain thermodynamically stable. Also the nitrogen atom can be placed between the free atomic spaces as the more thermodynamically stable position of the nitrogen is between the topmost layers. Also the optical absorption and refractive index energy dispersions of the pure and various stable doped SiC nanocrystals were studied.

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Sung, Yun-Mo, Woo-Chul Kwak, Woong Kim et Tae Geun Kim. « Enhanced ripening behavior of Mg-doped CdSe quantum dots ». Journal of Materials Research 23, n^o 7 (juillet 2008) : 1916–21. http://dx.doi.org/10.1557/jmr.2008.0238.

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Pure CdSe and Mg-doped CdSe nanocrystal quantum dots were synthesized into the zinc-blende structure at a low temperature by the inverse micelle technique using paraffin oil and oleic acid as surface capping agents. The ripening behavior of the nanocrystals was monitored using the red shift in ultraviolet (UV)-visible light absorption peaks, and their size variation was estimated using the so-called, quantum confinement theory. The Lifshitz–Slyozov–Wagner (LSW) kinetics analyses were performed based on the variation in size according to the ripening temperature and time period. The activation energy (Q) and reaction rate constant (Ko) were determined for the ripening reaction using Arrhenius-type plots. The kinetics analyses reveal that the volume diffusion through the liquid-phase solution is the governing mechanism for the ripening of both nanocrystals. The Mg-doped CdSe nanocrystals showed enhanced ripening kinetics due to the low activation energy for the volume diffusion.

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Thèses sur le sujet "Doped Nanocrystals"

Sutton, Rebecca Suzanne. « Dual-emitting Cu-doped ZnSe/CdSe nanocrystals ». Thesis, Kansas State University, 2015. http://hdl.handle.net/2097/19047.

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Master of Science
Department of Chemistry
Emily McLaurin
Cu-doped ZnSe/CdSe core/shell nanocrystals were synthesized using the growth doping method. Upon shell growth, the nanocrystals exhibit dual emission. The green luminescence peak is assigned as band edge emission and the broad, lower energy red peak is due to Cu dopant. Although, the oxidation state of Cu in the nanocrystals is debated, the emission is explained as recombination of a hole related to Cu²⁺ with an electron from the conduction band. The emission changed in the presence of dodecanethiol. Generally, the band edge emission intensity decreases and the Cu emission intensity increases. One explanation is the thiol acts as a hole trap, preventing hole transfer to the conduction band. Samples were obtained with varying amounts of Cd²⁺. In the presence of larger amounts of Cd²⁺, the nanocrystals had “thicker shells”, and both the band edge and Cu emission were less sensitive to thiol. The sensitivity likely decreased because the shelled, larger nanocrystals have fewer surface defects resulting in more available electrons.

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PINCHETTI, VALERIO. « Advanced Spectroscopy of Interface Engineered, Doped and “Electronically” Doped Colloidal Semiconductor Nanocrystals ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2018. http://hdl.handle.net/10281/199097.

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I nanocristalli colloidali a semiconduttore (NC) sono materiali processabili da soluzione che, dalla loro scoperta 30 anni fa, hanno attirato l’attenzione in campo scientifico e tecnologico per le loro proprietà ottiche ed elettriche. Infatti, i NC hanno un ampio range di potenziali applicazioni, che vanno dalle sorgenti luminose, alle celle solari, al bioimaging fino all’informazione quantistica. Ciò è dovuto alla profonda conoscenza e controllo delle loro proprietà elettroniche che si è raggiunto. Infatti, queste ultime si possono modificare controllando la dimensione, la composizione ma anche formando eterostrutture o introducendo impurezze, cioè drogando i NC. A causa dell’ampia varietà di NC che si possono sintetizzare, molti dubbi sui processi fotofisici sottostanti le proprietà ottiche macroscopiche rimangono ancora irrisolti. Dunque, mi sono focalizzato sullo studio di tre sotto-classi di NC: 1) a interfaccia ingegnerizzata; 2) drogati e 3) drogati elettronicamente. Dopo un breve ‘stato dell’arte’ della scienza dei NC colloidali (Capitolo 1), nel secondo Capitolo riporto una studio dettagliato dell’interazione fra i portatori di carica eccitati e l’interfaccia ingegnerizzata dei Dot-in-Bulk core/shell NC, che sono caratterizzati da emissione di fotoluminescenza (PL) sia dagli stati di core che da quelli di shell. Tramite misure di PL ultraveloce, dimostro che la caratteristica struttura all’interfaccia è la motivazione ultima da cui scaturisce la capacità di avere una doppia emissione radiativa, aggiungendo un ulteriore parametro nella chimica dei NC con il quale è possibile modificare le loro proprietà ottiche. Nel Capitolo 3, propongo una nuova strategia di sintesi che permetta di avere NC contenenti tutti un esatto numero di atomi droganti, evitando la distribuzione Poissoniana tipica dei contemporanei metodi di drogaggio. A questo scopo, uso cluster metallici monodispersi come semi di nucleazione per la sintesi dei NC e tramite analisi elementali ed ottiche mostro che effettivamente ogni NC sintetizzato contiene un solo cluster metallico e quindi un numero preciso di impurezze. Il drogaggio può essere considerato ‘isovalente’ nel caso in cui l’impurezza abbia lo stesso stato di ossidazione del semiconduttore, o ‘elettronico’ nel caso questa introduca una carica netta nella matrice ospitante. Il drogante isovalente più noto per i NC II-VI è il Mn2+. La sua configurazione elettronica d5 è caratterizzata da proprietà magnetiche uniche che, in strutture confinate quanticamente porta alla formazione di polaroni. Nel Capitolo 4, mostro come la formazione di polaroni tocca l’energia degli eccitoni tramite misure di PL risonante, ottenendo anche una stima precisa dell’intensità di campo magnetico generata solo dagli ioni Mn2+. Nel Capitolo 5, mostro come la risposta magnetica tipica del Mn2+ si può ottenere anche con l’argento, che è un drogante elettronico in quanto può assumere solo lo stato di ossidazione +1. L’argento però introduce uno stato nel gap energetico del semiconduttore ospitante che partecipa alla ricombinazione radiativa diventando, in modo transiente, un Ag2+ paramagnetico. Tramite misure di dicroismo circolare magnetico, dimostro che NC drogati con impurezze non magnetiche di argento possono assumere comportamenti paramagnetici attivati otticamente. Infine, nel Capitolo 6 ho focalizzato l’attenzione sui NC non tossici di CuInS2. I processi fotofisici alla base del meccanismo di emissione sono ancora dibattuti. A questo scopo, ho eseguito misure di PL risolta in temperatura e di spettroelettrochimica per studiare le dinamiche intrinseche ed estrinseche di questa classe di NC colloidali di ultima generazione.
Semiconductor colloidal nanocrystals (NCs) are solution-processable materials that have focused scientific and technological attention thanks to their tunable optical and electrical properties. Colloidal NCs have indeed wide applicative perspectives that span from light-emitting diodes, to lasers, from solar cells to luminescent solar concentrators, from bioimaging to quantum information. Such a large range of potential NCs technologies is warranted by the unique knowledge and control that has been achieved over the years about their electronic properties. Specifically, the optical and electric properties of these nanomaterials have been tuned by either controlling their size, composition and shape, or producing multicomponent heterostructures and introducing few atoms of a different chemical element, i.e. doping the NCs. Because of the vast gamut of possibilities that colloidal NCs offer, many questions on the elusive charge carrier dynamics underlying the macroscopic observations are still unanswered. In this picture, my work points toward three different sub-classes of NCs: i) interface engineered NCs; ii) doped NCs and iii) ‘electronic’ doped NCs. After a brief review about the ‘state of the art’ of the colloidal NC science (Chap. 1), in Chap. 2 I show a detailed investigation on the interaction between the photoexcited charge carriers and the engineered interface of Dot-in-Bulk core/shell NC, which are featured by radiative recombination from both the core and shell states. I demonstrate that their uncommon dual emission is due to the peculiar interface structure between the compositional domains and that a fine tuning of the optical properties can be also achieved by modifying the interfacial potential profile. In Chap. 3, I propose a novel synthetic approach to overcome the intrinsic Poisson distribution characteristic of the up-to-date NC doping strategies that are based on stochastic distribution of impurity ions in the NC ensemble. To this aim, I use monodispersed metal cluster as seeds for the NC nucleation in the synthesis reaction flask. By mean of combined optical and elemental analysis, I show that the copper clusters composed of exactly four atoms are indeed embedded in the semiconductor matrix, giving monodispersed doped NCs. Semiconductor doping can be further distinguished in ‘isovalent’ doping, in which the impurity has the same oxidation state of the host compound, and ‘electronic’ doping, given by ions which introduce a net charge in the surrounding matrix. The most known ‘isovalent’ dopant for II-VI NCs is Mn2+. Its d5 configuration is featured by unique magnetic properties that, in quantum confined nanomaterials lead to the formation of magnetic polarons. In Chap. 4, I reveal how polaron formation affects the exciton energy by mean of resonant PL measurements, offering a precise estimation of the intensity of the internal magnetic field generated by the Mn2+ spins. In Chap. 5, I report how the magnetic response typical of Mn2+ is reproduced by introducing silver, which is an electronic dopant for II-VI semiconductors, since it can only assume the +1 oxidation state. However, it introduces an electronic level in the forbidden energy gap of the host semiconductor that participates to the radiative recombination and therefore transiently switches to the paramagnetic +2 state. By mean of magnetic circular dichroism experiments I demonstrate that in NCs doped with nonmagnetic silver dopants, the paramagnetic response is completely optically activated. Finally, in Chap. 6 I focused the attention on non toxic, ternary CuInS2 colloidal NCs. The photophysical processes underlying their emission mechanism are, however, still under debate. To address this gap, I carried out temperature-controlled photoluminescence and spectro-electrochemical experiments to unravel the intrinsic and extrinsic charge carrier dynamics of this last-generation class of colloidal N

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Kriegel, Ilka. « Near-infrared plasmonics with vacancy doped semiconductor nanocrystals ». Diss., Ludwig-Maximilians-Universität München, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-164558.

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Plasmonics with heavily doped semiconductor nanocrystals (NCs) is an emerging field in NC science. However, impurity doping of NCs remains far from trivial and is, as yet, dominated by a low chemical control over the incorporated dopant atoms. An appealing alternative is vacancy doping, where the formation of vacancies in the structure is responsible for an increased carrier density and elegantly circumvents the issues related to impurity doping. Due to high carrier densities of around 10^21cm^(-3) localized surface plasmon resonances (LSPRs) in the near infrared (NIR) are expected, and as such highlighted to close the gap between conventionally doped NCs and noble metal nanoparticles. Copper chalcogenide NCs, namely copper sulfide (Cu2-xS), copper selenide (Cu2-xSe), and copper telluride (Cu2-xTe), are an attractive example of vacancy doped semiconductor NCs, with spectra dominated by intense NIR resonances. Within this study thorough experimental evidence has been given to prove the plasmonic nature of those NIR resonances. By presenting typical plasmonic characteristics, such as refractive index sensitivity of the LSPR, its intrinsic size dependence, plasmon dynamics, or interparticle plasmon coupling, the LSPRs in copper chalcogenide NCs have unambiguously been identified. The chemical nature of vacancy doping turns out to deliver an additional, highly attractive means of control over the LSPR in vacancy doped copper chalcogenide NCs. Through chemical tailoring of the copper vacancy density via controlled oxidation and reduction, as shown in this study, a reversible tuning of the LSPR over a wide range of frequencies in the NIR (1000-2000 nm) becomes feasible. This highlights copper chalcogenide NCs over conventional plasmonic materials. Notably, the complete suppression of the LSPR uncovers the excitonic features present only in the purely semiconducting, un-doped NCs and reveals the unique option to selectively address excitons and highly tunable LSPRs in one material (bandgap Eg~1.2 eV). As such, copper chalcogenide NCs appear to hold as an attractive material system for the investigation of exciton plasmon interactions. Indeed, a quenching of the excitonic transitions in the presence of the developing LSPR is demonstrated within this work, with a full recovery of the initial excitonic properties upon its suppression. A theoretical study on the shape dependent plasmonic properties of Cu2-xTe NCs reveals a deviation from the usual Drude model and suggests that the carriers in vacancy doped copper chalcogenide NCs cannot be treated as fully free. On the other hand, the Lorentz model of localized oscillators appears to account for the weak shape dependence, as observed experimentally, indicating an essential degree of localization of the carriers in vacancy doped copper chalcogenide NCs. Taken together, this work delivers a huge step toward the complete optical and structural characterization of plasmonic copper chalcogenide NCs. The advantages of semiconductor NC chemistry have been exploited to provide access to novel plasmonic shapes, such as tetrapods that have not been feasible to produce so far. A precise size, shape and phase control presents the basis for this study, and together with a thorough theoretical investigation delivers important aspects to uncover the tunable plasmonic properties of vacancy doped copper chalcogenide NCs.

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Nordin, Muhammad N. « Magneto optical study of undoped and doped PbS nanocrystals ». Thesis, University of Surrey, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.606691.

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Magneto optical studies of colloidal PbS nanocrystals (NCs) have been undertaken to determine their fundamental properties. Measurements including absorption, photoluminescence (PL) and PL lifetime decay are presented along with their dependence upon temperature, magnetic field, and magnetic dopant concentration for undoped and doped PbS NCs. Temperature dependence of undoped PbS NCs, recorded from 300 K down to 3 K, displays a Stoke shift increasing from ~7 5 meV to ~125 meV which is fitted using a three-level rate equation model, supported by PL lifetime decay measurements, that indicate energy separation of ~ 6.0 ± 0.3 meV between the two optically active levels within PbS NCs. Magneto optical studies of undoped PbS NCs at low temperature using a field sweep from -7 Tesla to 7 Tesla are presented. Analysis of the magneto-PL data yields a degree of circular polarization (DCP) of 33% at 7 T and 2 K. Further analysis predicts an excitonic g-factor, gu for the -4 nm diameter PbS NCs of ....().54 by taking account of random orientation of PbS NCs. Using this value of g~x the expected Zeeman splitting at 7T ,ΔEzeeman , is calculated to be ~0.22 meV. Optical studies of PbS NCs with TIFffCNQ molecule showed modification of the PL spectra and PL lifetime. It is proposed that the quenching effect on the PL of PbS-TTF in the range of 900 nm to 1300 nm is due to a charge transfer mechanism . The PL obtained from PbS-TCNQ solutions display a second emission peak centred at ~700 nm which is directly related to the TCNQ concentration. A study of the optical properties of Mn-implanted PbS NCs was undertaken and compared with that of undoped PbS NCs. The PL spectra of all Mn-implanted PbS NCs showed a significant red shift of the PL peak compared to undoped PbS NCs. Based on fitting of a Brillouin function to the difference in the temperature dependent Stokes shift between the Mn-implanted and undoped PbS NCs an effective exchange field of ~81 T is predicted.

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Lounis, Sebastien Dahmane. « The influence of dopant distribution on the optoelectronic properties of tin-doped indium oxide nanocrystals and nanocrystal films ». Thesis, University of California, Berkeley, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3686398.

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Colloidally prepared nanocrystals of transparent conducting oxide (TCO) semiconductors have emerged in the past decade as an exciting new class of plasmonic materials. In recent years, there has been tremendous progress in developing synthetic methods for the growth of these nanocrystals, basic characterization of their properties, and their successful integration into optoelectronic and electrochemical devices. However, many fundamental questions remain about the physics of localized surface plasmon resonance (LSPR) in these materials, and how their optoelectronic properties derive from their underlying structural properties. In particular, the influence of the concentration and distribution of dopant ions and compensating defects on the optoelectronic properties of TCO nanocrystals has seen little investigation.

Indium tin oxide (ITO) is the most widely studied and commercially deployed TCO. Herein we investigate the role of the distribution of tin dopants on the optoelectronic properties of colloidally prepared ITO nanocrystals. Owing to a high free electron density, ITO nanocrystals display strong LSPR absorption in the near infrared. Depending on the particular organic ligands used, they are soluble in various solvents and can readily be integrated into densely packed nanocrystal films with high conductivities. Using a combination of spectroscopic techniques, modeling and simulation of the optical properties of the nanocrystals using the Drude model, and transport measurements, it is demonstrated herein that the radial distribution of tin dopants has a strong effect on the optoelectronic properties of ITO nanocrystals.

ITO nanocrystals were synthesized in both surface-segregated and uniformly distributed dopant profiles. Temperature dependent measurements of optical absorbance were first combined with Drude modeling to extract the internal electrical properties of the ITO nanocrystals, demonstrating that they are well-behaved degenerately doped semiconductors displaying finite conductivity at low temperature and room temperature conductivity reduced by one order of magnitude from that of high-quality thin film ITO.

Synchrotron based x-ray photoelectron spectroscopy (XPS) was then employed to perform detailed depth profiling of the elemental composition of ITO nanocrystals, confirming the degree of dopant surface-segregation. Based on free carrier concentrations extracted from Drude fitting of LSPR absorbance, an inverse correlation was found between surface segregation of tin and overall dopant activation. Furthermore, radial distribution of dopants was found to significantly affect the lineshape and quality factor of the LSPR absorbance. ITO nanocrystals with highly surface segregated dopants displayed symmetric LSPRs with high quality factors, while uniformly doped ITO nanocrystals displayed asymmetric LSPRs with reduced quality factors. These effects are attributed to damping of the plasmon by Coulombic scattering off ionized dopant impurities.

Finally, the distribution of dopants is also found to influence the conductivity of ITO nanocrystal films. Films made from nanocrystals with a high degree of surface segregation demonstrated one order of magnitude higher conductivity than those based on uniformly doped crystals. However, no evidence was found for differences in the surface electronic structure from one type of crystal to the other based on XPS and the exact mechanism for this difference is still not understood.

Several future studies to further illuminate the influence of dopant distribution on ITO nanocrystals are suggested. Using synchrotron radiation, detailed photoelectron spectroscopy on clean ITO nanocrystal surfaces, single-nanoparticle optical measurements, and hard x-ray structural studies will all be instructive in elucidating the interaction between oscillating free electrons and defect scattering centers when a plasmon is excited. In addition, measurements of temperature and surface treatment-dependent conductivity with carefully controlled atmosphere and surface chemistry will be needed in order to better understand the transport properties of ITO nanocrystal films. Each of these studies will enable better fundamental knowledge of the plasmonic properties of nanostructures and improve the development of nanocrystal based plasmonic devices.

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Clark, Maurice Tzeng Y. « Growth and characterization of nitrogen doped nanocrystalline diamond films ». Auburn, Ala., 2006. http://hdl.handle.net/10415/1313.

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Kriegel, Ilka [Verfasser], et Jochen [Akademischer Betreuer] Feldmann. « Near-infrared plasmonics with vacancy doped semiconductor nanocrystals / Ilka Kriegel. Betreuer : Jochen Feldmann ». München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2013. http://d-nb.info/1046503316/34.

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Chen, Xiaobo. « Synthesis and Investigation of Novel Nanomaterials for Improved Photocatalysis ». Case Western Reserve University School of Graduate Studies / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=case1117575871.

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ROSINA, IRENE. « Exploiting Cation Exchange Reactions in Doped Colloidal NIR Semiconductor Nanocrystals : from synthesis to applications ». Doctoral thesis, Università degli studi di Genova, 2020. http://hdl.handle.net/11567/1019427.

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Colloidal quantum dots (CQDs) have tunable optical properties through manipulation of their size, shape, and surface chemistry. Among pholuminescent QDs, near-infrared (NIR) emitting ones are of particular interest since they can be used in several applications, from the labeling in living tissues, to the integration in commercial optoelectronic devices, like photovoltaics for solar energy conversion or photodetectors from visible to the near-infrared and mid-infrared. In addition, the exciting promise of CQDs is that is associated with easy and low-cost device fabrication process. In fact, solution-based techniques like spin-coating, dip coating and ink-jet printing are typically used for solution CQDs readily to be used in large-area processing techniques. Thus, to obtain an ink solution of nanocrystals (NCs) ready to be used in device fabrication process, in this thesis, cation exchange (CE) reactions have been used as a convenient tool to finely transform NCs directly in solution or deposited as thin films. These reactions allow to substitute a fraction or all “host” metal cations of pre-synthesized NCs with new “guest” cations while preserving both NCs’ size, shape and, typically, crystal structure. Depending on the miscibility of the reactant and product materials, and on the kinetics of the CE reaction, different types of nanostructures can be accessed ranging from alloy NCs, doped systems, dimers, core@shell (or core@graded-shell) heterostructures even with elaborated architectures (i.e., quantum wells, multiple-cores@shell). Unlike ion substitution in solids, cation exchange at nanoscale results in fast reaction rate and an easy modulation of the thermodynamics through selective ion coordination in solution. This study provides an overview of the CE on semiconductor NCs, in particular on II-VI, I-III-VI2 and III-VI compounds. We first explore the exchange between cadmium chalcogenides and mercury ions to produce Cd1-xHgxTe CQDs which can be potentially employed in NIR photodetectors and photovoltaic devices. Our developed synthesis is a result of a wide systematic investigation process, in which we varied specific physical parameters, such as the reaction temperature, the feed molar ratio of the precursor and the solvent. More specifically, these aspects were studied to have control on the size, shape, surface composition and crystalline phase after mild conditions of annealing into stable connected crystals. This peculiarity could be exploited to boost the photogenerated charges diffusion in polycrystalline photoconducting films fabricated by means of an ink of NCs solution. Additionally, another aspect studied was the surface passivation of Cd1-xHgxTe colloidal NCs, in order to understand how to optimize the charge transfer efficiency among the nanocrystals. The carrier transport in QD devices differs fundamentally from band transport in bulk semiconductors. In nanocrystal film it is of fundamental relevance to improve the mobility of the photogenerated charges. Noteworthy, the granularity of the system and the consequent coupling between adjacent dots can produce additional physical parameters, as charge recombination. The carrier diffusion length can be limited by trapping sites1. To overcome these limitations, post-synthetic strategies that couple the high quality NCs solutions with ideal properties (band gap, absorption, monodispersivity) and high-quality films (quantum dot packing, passivation, and absorptive/conductive properties) are necessary. Indeed, to improve the inter-NCs conductivity in a NC film, ligand exchange and stripping procedures are widely used, with the aim of replacing insulating surfactants with more conductive species. These procedures have some drawbacks, for example metal cations can desorb from the surface of the NCs during the stripping. On the contrary, here we will show how our nano heterostructures (NHCs) enable to avoid the post-process ligand stripping and to perform the final annealing step in milder conditions. Above these considerations, CE can be exploited to address NCs solution through surface uniformity from the nano- to the macroscopic scale. This is the first step toward electronic coupling between the separate building blocks of nanocrystals. Apart from III-V QDs, we shifted our research activity on valid alternative material which do not contain toxic heavy metals such as Cd, Pb, As or Hg, and that offer a high flexibility for tuning band gap in the NIR window. In chapter 5, the results about the study of a III-V system are reported. Thus, we studied InP system, which is probably the only one that could provide a compatible emission color range similar to that of Cd-based QDs but without intrinsic toxicity. Nevertheless, the synthesis of III-V NCs, due to their covalent-bond character, is limited by long reaction times or an uncontrollably fast nucleation that may lead to the formation of amorphous or bulk compounds. The role of our work is to explore the reported InP synthesis and to further improve the luminescent properties of these systems Here we study the effect of different parameter (molar concentration in reaction mixture, the use of different phosphorous precursors) to enhance the control over the particle size and size distribution. After that, we studied different Sulphur source precursors to obtain InP@ZnS core@shell NCs with high quantum Yield (QY). In the last chapter, we describe also I-III-VI2 system as CuInS2 for photoluminescence modulation. In this Chapter Copper Indium Sulfide nanocrystals are prepared using a single-step heating up method relying on the low thermal stability of ter- dodecanethiol used as stabilizing agent, solvent, and sulfur precursors. The obtained particles exhibit an emission varying from 710 to 940 nm. This range depends on the extent of the heating time (pre-heating) before the threshold temperature of 230°C for the growth process of ternary semiconductor NCs such as of CIS nanocrystals. Afterwards we report on the procedure for the growth of a ZnS shell, which enables a blueshift of the PL emission wavelength with respect to those of their parent CIS, due to the widening of the band gap for the entrance of zinc ions into the CIS structures.

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Archer, Paul I. « Building on the hot-injection architecture : giving worth to alternative nanocrystal syntheses / ». Thesis, Connect to this title online ; UW restricted, 2007. http://hdl.handle.net/1773/8520.

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Livres sur le sujet "Doped Nanocrystals"

Yang, Heesun. Syntheses and applications of Mn-doped II-VI semiconductor nanocrystals. 2003.

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Yu, Lixin. Development of Luminescence Properties of Eu3+-doped Nanosized Materials. Nova Science Publishers, Incorporated, 2011.

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Chapitres de livres sur le sujet "Doped Nanocrystals"

Borrelli, N. F. « Photonic Applications of Semiconductor-Doped Glasses ». Dans Semiconductor Nanocrystals, 1–51. Boston, MA : Springer US, 2003. http://dx.doi.org/10.1007/978-1-4757-3677-9_1.

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Roschuk, Tyler, Jing Li, Jacek Wojcik, Peter Mascher et Iain D. Calder. « Lighting Applications of Rare Earth-Doped Silicon Oxides ». Dans Silicon Nanocrystals, 487–506. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2010. http://dx.doi.org/10.1002/9783527629954.ch17.

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Fujii, Minoru. « Optical Properties of Intrinsic and Shallow Impurity-Doped Silicon Nanocrystals ». Dans Silicon Nanocrystals, 43–68. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2010. http://dx.doi.org/10.1002/9783527629954.ch3.

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Kumar, J., S. Ramasubramanian, R. Thangavel et M. Rajagopalan. « On the Optical and Magnetic Properties of Doped-ZnO ». Dans ZnO Nanocrystals and Allied Materials, 309–29. New Delhi : Springer India, 2013. http://dx.doi.org/10.1007/978-81-322-1160-0_15.

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Panse, Christian, Roman Leitsmann et Friedhelm Bechstedt. « Nanomagnetism in Transition Metal Doped Si Nanocrystals ». Dans High Performance Computing in Science and Engineering, Garching/Munich 2009, 541–52. Berlin, Heidelberg : Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-13872-0_45.

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Zhou, Shu, Xiaodong Pi, Yi Ding, Firman Bagja Juangsa et Tomohiro Nozaki. « Silicon nanocrystals doped with boron and phosphorous ». Dans Silicon Nanomaterials Sourcebook, 341–66. Boca Raton, FL : CRC Press, Taylor & Francis Group, [2017] | Series : Series in materials science and engineering : CRC Press, 2017. http://dx.doi.org/10.4324/9781315153544-17.

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Zhang, Fan. « Upconversion Luminescence of Lanthanide Ion-Doped Nanocrystals ». Dans Photon Upconversion Nanomaterials, 73–119. Berlin, Heidelberg : Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-662-45597-5_3.

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Matsuda, Yoshinobu, Akinori Hirashima, Kenji Mine, Takuhiro Hashimoto, Daichi Matsuoka, Masanori Shinohara et Tatsuo Okada. « Deposition of Aluminum-Doped ZnO Films by ICP-Assisted Sputtering ». Dans ZnO Nanocrystals and Allied Materials, 125–48. New Delhi : Springer India, 2013. http://dx.doi.org/10.1007/978-81-322-1160-0_6.

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Bryan, J. Daniel, et Daniel R. Gamelin. « Doped Semiconductor Nanocrystals : Synthesis, Characterization, Physical Properties, and Applications ». Dans Progress in Inorganic Chemistry, 47–126. Hoboken, NJ, USA : John Wiley & Sons, Inc., 2005. http://dx.doi.org/10.1002/0471725560.ch2.

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Peng, W. Q., S. C. Qu, G. W. Cong et Z. G. Wang. « Structural and Optical Investigation of Mn-Doped ZnS Nanocrystals ». Dans Materials Science Forum, 1795–98. Stafa : Trans Tech Publications Ltd., 2005. http://dx.doi.org/10.4028/0-87849-960-1.1795.

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Actes de conférences sur le sujet "Doped Nanocrystals"

Mei, Guang, Scott Carpenter, L. E. Felton et P. D. Persans. « Size dependence of quantum Stark effect in CdSxSe1-x nanocrystals ». Dans OSA Annual Meeting. Washington, D.C. : Optica Publishing Group, 1991. http://dx.doi.org/10.1364/oam.1991.wt5.

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We report experimental electromodulation results on various sized CdS x Se1- x nanocrystals doped in a glass matrix. The samples were made by heat treatment and annealing of as-received filter glass from Schott. The size of the nanocrystals can be controlled from 40 to 200Å in diameter by annealing time. Transmission electron microscopy and absorption measurements were performed to get the size and volume fraction of semiconductor nanocrystals in the sample. Raman experiments indicated that the samples are CdS0.44Se0.56 and that the composition does not change with nanocrystal size. Electromodulation experiments were performed, and two strong peaks from the quantum-confined excitons were observed.

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Choi, Dongsun, Juhee Son, Mihyeon Park, Joonhyung Lim, Yun Chang Choi et Kwang Seob Jeong. « Intraband Energy State Study in Self-Doped Quantum Dots ». Dans Internet NanoGe Conference on Nanocrystals. València : Fundació Scito, 2021. http://dx.doi.org/10.29363/nanoge.incnc.2021.042.

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Nataraj, Latha, Aaron Jackson, Lily Giri, Clifford Hubbard et Mark Bundy. « Doped group-IV semiconductor nanocrystals ». Dans 2013 IEEE International Nanoelectronics Conference (INEC). IEEE, 2013. http://dx.doi.org/10.1109/inec.2013.6466028.

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Chen, Jiabao, Gengfeng Wu, Jing Tang, Bing Xu et Xiaowei Sun. « Eu-doped CsPbBr3 perovskite nanocrystals ». Dans 2021 4th International Conference on Advanced Electronic Materials, Computers and Software Engineering (AEMCSE). IEEE, 2021. http://dx.doi.org/10.1109/aemcse51986.2021.00050.

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Thantu, N., J. S. Melinger, D. McMorrow et B. L. Justus. « Femtosecond Nonlinear Optical Response of CuBr and CuCI Nanocrystals in Glass in the Optically Transparent Region ». Dans Nonlinear Optics : Materials, Fundamentals and Applications. Washington, D.C. : Optica Publishing Group, 1996. http://dx.doi.org/10.1364/nlo.1996.nthe.18.

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Because large third-order refractive nonlinearities, γ, are expected, much study on nanocrystal doped glasses has focused on the nonlinear optical properties at or near the single photon resonance.1 Although γ is smaller in the single-photon transparent region, its temporal response is expected to be pulse-width limited. More importantly, since the potential use of these materials as optical devices depends on the figure-of-merit ratio proportional to γ/(ατ or (βτ), where α and β are the linear and nonlinear absorption coefficients, respectively, and τ is the response time, a possibly larger figure of merit in the transparent region warrants studies far from the absorption edge. Recent studies2,3,4 performed on photodarkening CuBr nanocrystal doped glasses in the transparent region indicate a sizable two-photon enhanced nonlinearity which should scale with the concentration of CuBr nanocrystals in the glass. Time-resolving the nonlinear optical response3 with 60 fs, 620 nm optical pulses revealed a nearly pulse-width limited response followed by a subpicosecond decay. The CuBr and CuCI nanocrystals with the band edge in the 370-400 nm region are single-photon-transparent to the 620 nm light, but are two-photon-resonant at this wavelength or at 800 nm, the wavelength of interest in this study.

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Kawazoe, Tadashi, Tetsuya Yamamoto, Lev G. Zimin et Yasuaki Masumoto. « Persistent spectral hole-burning in CuBr nanocrystals ». Dans Spectral Hole-Burning and Related Spectroscopies : Science and Applications. Washington, D.C. : Optica Publishing Group, 1994. http://dx.doi.org/10.1364/shbs.1994.wd51.

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Persistent hole-burning phenomena in ion-doped glass and organic-molecule-doped organic glass have been well known. In recent years semiconductor nanocrystals have been studied extensively because of their novel optical properties such as large optical nonlinearities, and their possibility for applications, such as lasers, ultrafast optical devices, and so on. However, so far "persistent spectral hole-burning (PSHB)" phenomenon in semiconductor nanocrystals has never been reported until the PSHB phenomenon was observed in CdSe and CuCl nanocrystals in our laboratory. Therefore, we may be able to find the other semiconductor nanocrystals which show persistent hole-burning phenomenon. In this publication, we report the persistent hole-burning phenomenon in CuBr semiconductor nanocrystals embedded in glass. Our experiment shows the spectral hole in CuBr nanocrystals remains for more than 8 hours without any detectable relaxation.

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Bacher, Gerd. « Magnetically doped nanocrystals : from functionality to devices ». Dans Spintronics XIII, sous la direction de Henri-Jean M. Drouhin, Jean-Eric Wegrowe et Manijeh Razeghi. SPIE, 2020. http://dx.doi.org/10.1117/12.2568478.

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Kalachev, Alexey A., et Daria D. Vlasova. « Long-lived photon echo in doped nanocrystals ». Dans SPIE Proceedings, sous la direction de Vitaly V. Samartsev. SPIE, 2008. http://dx.doi.org/10.1117/12.801683.

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Jayadevan, K. P., et Shubhada S. Kerkar. « Microstructural characteristics of boron doped TiO2 nanocrystals ». Dans PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS : ICAM 2019. AIP Publishing, 2019. http://dx.doi.org/10.1063/1.5130221.

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Zou, Shou-Jyun, et Shun-Jen Cheng. « Magnetism of magnetic ion doped semiconductor nanocrystals ». Dans SPIE NanoScience + Engineering, sous la direction de Henri-Jean Drouhin, Jean-Eric Wegrowe et Manijeh Razeghi. SPIE, 2013. http://dx.doi.org/10.1117/12.2023623.

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Rapports d'organisations sur le sujet "Doped Nanocrystals"

Kelley, DAVID. Ligand-Controlled Energetics and Charge Transfer in Pure and Doped Nanocrystals. Office of Scientific and Technical Information (OSTI), février 2021. http://dx.doi.org/10.2172/1766125.

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