Tesis sobre el tema "ZnO nanocrystal"
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Chieh-Yi, Kuo. "Fabrication and Optical Properties of ZnO Nanocrystal/GaN Quantum Well Based Hybrid Structures". Thesis, Linköpings universitet, Tunnfilmsfysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-81675.
Texto completoEricsson, Leif KE. "Growth and Characterization of ZnO Nanocrystals". Doctoral thesis, Karlstads universitet, Institutionen för ingenjörsvetenskap och fysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-27156.
Texto completoBaksidestext The understanding of the surfaces of materials is of crucial importance to all of us. Considering nanocrystals (NCs), that have a large surface to bulk ratio, the surfaces become even more important. In the work in this thesis ZnO NCs were studied. The fundamental properties of ZnO surfaces were studied using distributions of ZnO NCs on SiO2/Si surfaces. Annealing at 650 °C in UHV cleaned the surfaces of the ZnO NCs enough for sharp LEEM imaging and chemical characterization while no sign of de-composition was found. A flat energy band structure for the ZnO/SiO2/Si system was proposed after 650 °C. Increasing the annealing temperature to 700 °C causes a de-composition of the ZnO that induce a downward band bending on the surfaces of ZnO NCs. Flat ZnO NCs with predominantly polar surfaces were grown using a microwave assisted process. Tuning the chemistry in the growth solution the growth was restricted to only plate-shaped crystals, i.e. a very uniform growth. The surfaces of the NCs were characterized using AFM, revealing a triangular reconstruction of the ZnO(0001) surface not seen without surface treatment at ambient conditions before. Following cycles of sputtering and annealing in UHV, we observe by STM a surface reconstruction interpreted as 2x2 with 1/4 missing Zn atoms.
Dias, Eva. "The photophysics of CdSe/ZnS/CdSe core/barrier/shell nanocrystals: light harvesting, single nanocrystal blinking, and optical gain". Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=107729.
Texto completoCette thèse explore les propriétés photophysique du coeur/barrière/coquille des nanocrystaux de CdSe/ZnS/CdSe par une combinaison de spectroscopies à l'état d'équilibre et en temps résolu. Il est intéréssant de noter que ces matériaux présentent de la photoluminescence (PL) provenant du coeur CdSe et de la coquille CdSe qui pourrait être exploitée dans une variété d'applications comme l'émission de lumière blanche et gain optique. Des mesures à l'état d'équilibre ont illustré le couplage entre les deux phases de CdSe. On a démontré que la coquille de CdSe influence les propriétés optique du coeur de CdSe. En effect, la coquille de CdSe fonctionne comme collecteur de lumière, augmentant la luminosité du coeur de CdSe comparé aux nanocrystaux nus de CdSe. Les spectres de nanocrystaux simples de CdSe/ZnS/CdSe révèlent que les deux phases CdSe montrent de l'intermittence PL et de la diffusion spectrale. Aucune corrélation n'a été observée dans la diffusion spectrale des deux phases de CdSe à l'échelle de mesure. Par contre, les largeurs de raie de PL du simple nanocrystal suggère que la diffusion spectrale des deux phases de CdSe diffèrent à des échelles de temps plus courtes. Par spectroscopie ultrarapide d'absorption transitoire, on a démontré que les nanocrystaux de CdSe/ZnS/CdSe font preuve de gain optique amélioré sur les nanocrystaux de CdSe nus. La largeur de raie des émissions stimulées des nanocrystaux de CdSe/ZnS/CdSe était plus élargie que celle des nanocrystaux de CdSe à cause de la présence de la coquille de CdSe. On a aussi démontré que les nanocrystaux de CdSe/ZnS/CdSe ont des plus basses énergies de liaisons de biexciton que les nanocrystaux de CdSe, contribuant à une amélioration de performance de gain. De plus, des caractéristiques de blanchiment à haute énergie dans les spectres d'absorption transitoire indiquent que les populations d'excitons demeurent à des états d'énergie plus élevés, permettant une émission double en couleur.
Wang, Jianpu. "Optoelectronic properties and memory effects of ZnO nanocrystals". Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611743.
Texto completoLee, Kwang Jik. "Study of stability of ZnO nanoparticles and growth mechanisms of colloidal ZnO nanorods". Texas A&M University, 2005. http://hdl.handle.net/1969.1/4303.
Texto completoДоброжан, Олександр Анатолійович, Александр Анатольевич Доброжан, Oleksandr Anatoliiovych Dobrozhan, Станіслав Ігорович Кахерський, Станислав Игорович Кахерский, Stanislav Ігорович Kakherskyi, Роман Миколайович Пшеничний et al. "Cтруктурні та субструктурні характеристики нанокристалів і плівок ZnO для використання у сонячній енергетиці". Thesis, Дніпровський національний університет імені Олеся Гончара, 2020. https://essuir.sumdu.edu.ua/handle/123456789/80943.
Texto completoZhou, Shengqiang. "Transition metal implanted ZnO: a correlation between structure and magnetism". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1209998012687-36583.
Texto completoUrgessa, Zelalem Nigussa. "Growth and characterization of ZnO nanorods using chemical bath deposition". Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1021124.
Texto completoTu, Wei-Lun Scharf Thomas W. "Processing, structure, and tribological property interrelationships in sputtered nanocrystalline ZnO coatings". [Denton, Tex.] : University of North Texas, 2009. http://digital.library.unt.edu/ark:/67531/metadc12207.
Texto completoZhou, Shengqiang. "Transition metal implanted ZnO: a correlation between structure and magnetism". Doctoral thesis, Technische Universität Dresden, 2007. https://tud.qucosa.de/id/qucosa%3A23718.
Texto completoLander, Sanna. "Rapid microwave assisted growth of ZnO nanocrystals: effects of heating power and zinc precursor". Thesis, Karlstads universitet, Institutionen för ingenjörsvetenskap och fysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-33269.
Texto completoNannen, Ekaterina [Verfasser], Gerd [Akademischer Betreuer] Bacher y Roland [Akademischer Betreuer] Schmechel. "All-inorganic White Light Emitting Devices Based on ZnO Nanocrystals / Ekaterina Nannen. Gutachter: Gerd Bacher ; Roland Schmechel". Duisburg, 2012. http://d-nb.info/1027669174/34.
Texto completoChen, Wei. "Zn–based chalcogenide 1D semiconductor nanocrystals: synthesis and applications". Thesis, Curtin University, 2020. http://hdl.handle.net/20.500.11937/81226.
Texto completoAnwar, Monib. "Effect of X-ray Irradiation on the Blinking of CdSe/ZnS Nanocrystals". Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-227966.
Texto completoTu, Wei-Lun. "Processing, Structure, and Tribological Property Interrelationships in Sputtered Nanocrystalline ZnO Coatings". Thesis, University of North Texas, 2009. https://digital.library.unt.edu/ark:/67531/metadc12207/.
Texto completoNygren, Kristian. "Solar cells based on synthesized nanocrystalline ZnO thin films sensitized by chlorophyll a and photopigments isolated from spinach". Thesis, Linköping University, Department of Physics, Chemistry and Biology, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-55032.
Texto completoThe principles of dye-sensitized solar cells were studied and are outlined in this thesis. An overview of the basic steps needed to create a DSC isfollowed by detailed experimental information on how to assemble the solar cells that were fabricated in this project. They were based on synthesizednanocrystalline ZnO thin films sensitized by chlorophyll a as well as isolated photopigments from spinach leaves. The nanocrystals werestudied using XRD, and it was confirmed that three different methods of synthesis resulted in ZnO crystals of a few nanometers. The solar cellswere assembled with Au electrodes in a sandwich configuration and their photovoltaic properties were measured. Overall light-to-electricity conversionwas low with the highest efficiency being 0.21 %. An astonishingly low efficiency of 0.0003 % was noted for a thin film which was not thermallytreated, and it is suggested that heat-treatment is of great importance. It was also found that photopigments from spinach can be extractedeasily and used as molecular sensitizer without any demanding purification steps.
Silva, Alessandra dos Santos. "Estudo de propriedades físicas de nanocristais de ZnTe e Zn1-xAxTe (A = Mn; Co) no sistema vítreo P2O5 ZnO Al2O3 BaO PbO". Universidade Federal de Uberlândia, 2015. https://repositorio.ufu.br/handle/123456789/15620.
Texto completoIn this work, Zn1-xAxTe (A = Mn, Co) diluted magnetic semiconductors (DMS) nanocrystal (NCs) were successfully grown in the P2O5 ZnO Al2O3 BaO PbO glass system synthesized by the method of Fusion-Nucleation, after subjecting to appropriate thermal annealing. Various experimental techniques were used in this study in order to get a comprehensive understanding of the optical, morphological, structural and magnetic properties these NCs. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) images revealed the size of both of Zn1-xMnxTe and Zn1-xCoxTe NCs. From the vibrating sample magnetometer (VSM) technique, there was growth behavior of magnetization and magnetic susceptibility as a function of the Mn concentration in the samples containing Zn1-xMnxTe NCs. At lower Mn concentrations, the sp electrons of ZnTe host semiconductor interact with the d electrons of Mn2+ ions, resulting in the sp-d exchange interaction, which causes a small increase in susceptibility. At higher Mn concentrations, the d-d exchange interaction between Mn atoms dominates over the sp-d exchange interaction, resulting in an abrupt increase in susceptibility. The EPR spectra, in addition to prove the results exhibited the well-known sextet hyperfine lines of Mn2+ ions, since samples with low Mn concentrations revealed the presence of Mn2+ ions within and near the surface of the ZnTe NCs. From the optical absorption spectra (OA) and photoluminescence (PL), analyzed on the basis of crystal field theory (CFT) as well as of the diffraction X-ray (XRD), Raman scattering (RS) and electron microscopy transmission (TEM) techniques, the substitutional incorporation of Mn2+ ions was confirmed up to its solubility limit (x = 0.100) ZnTe NCs. Above this concentration, can observe the formation of manganese oxide NCs such as MnO and MnO2, since the nucleation rate for the formation of these NCs is greater than that of Zn1-xMnxTe NCs, at high concentrations. Furthermore, from the PL spectra, it was found that it is possible to tune the emission of energy related to transition 4T1(4G) → 6A1(6S) of Mn2+ ions, of the spectral orange region to the near infrared, depending on Mn concentration. This is possible due to the variation of the local crystal field, where these ions are inserted. From the OA spectra, analyzed on the basis of CFT, it showed that Co2+ ions are substitutionally incorporated in tetrahedral sites of ZnTe NCs, due to its characteristics transitions in visible and near infrared spectral region. This evidence has been enhanced from MFM images, since NCs doped with magnetic ions, magnetically respond when induced by the magnetization of the probe.
Neste trabalho, nanocristais semicondutores magnéticos diluídos (SMD) de Zn1-xAxTe (A = Mn; Co) foram crescidos com sucesso no sistema vítreo P2O5 ZnO Al2O3 BaO PbO, sintetizado pelo método de Fusão-Nucleação, após submetê-lo a tratamento térmico apropriado. Várias técnicas experimentais foram utilizadas neste estudo a fim de obter um entendimento compreensivo das propriedades ópticas, morfológicas, estruturais e magnéticas desses NCs. Imagens de microscopia eletrônica de transmissão (MET) e microscopia de força atômica (MFA) revelaram o tamanho tanto de NCs de Zn1-xMnxTe quanto de Zn1-xCoxTe. A partir da técnica de magnetometria de amostra vibrante (MAV), verificou-se o crescimento da magnetização e o comportamento da susceptibilidade magnética, em função da concentração de Mn, em amostras contendo NCs de Zn1-xMnxTe. Em baixas concentrações de Mn, os elétrons sp do semicondutor hospedeiro ZnTe, interagem com os elétrons d dos íons Mn2+, resultando na interação de troca sp-d, que provoca um pequeno aumento na susceptibilidade magnética. Já, em concentrações mais elevadas de Mn, a interação de troca d-d entre átomos de Mn domina a interação de troca sp-d, o que resulta em um aumento abrupto da susceptibilidade. Os espectros RPE, além de comprovar esses resultados, exibiram o bem conhecido sexteto de linhas hiperfinas de íons Mn2+, uma vez que amostras com baixas concentrações de Mn revelaram a presença de íons Mn2+ no interior e próximos à superfície dos NCs de ZnTe. A partir dos espectros de absorção óptica (AO) e fotoluminescência (FL), analisados com base na teoria do campo cristalino (TCC), bem como das técnicas de difração de raios-X (DRX), espalhamento Raman (ER) e microscopia eletrônica de transmissão (MET), confirmou-se a incorporação substitucional de íons Mn2+ até seu limite de solubilidade nominal (x = 0,100) em NCs de ZnTe. Acima dessa concentração, observa-se a formação de NCs de óxido de manganês, tais como MnO e MnO2, uma vez que a taxa de nucleação para a formação desses NCs é maior que a de NCs de Zn1-xMnxTe, em altas concentrações. Além disso, a partir dos espectros FL, verificou-se que é possível sintonizar a energia de emissão relacionada à transição 4T1(4G) → 6A1(6S) de íons Mn2+, da região espectral laranja ao infravermelho próximo, em função da concentração de Mn. Isso é possível devido à variação do campo cristalino local, onde esses íons estão inseridos. A partir dos espectros AO, analisados com base na TCC, evidenciou-se que íons Co2+ são incorporados substitucionalmente em sítios tetraédricos de NCs de ZnTe, devido às suas transições características na região espectral do visível e infravermelho próximo. Essa evidência foi reforçada a partir de imagens de MFM, uma vez que os NCs, dopados com íons magnéticos, respondem magneticamente quando induzidos pela magnetização da sonda.
Doutor em Física
Hering, Vitor Renaux. "Interação entre proteínas fluorescentes e nanocristais de CdSe/ZnS". Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/46/46131/tde-15082007-074551/.
Texto completoProteins belonging to the GFP family were used to characterize their interaction with fluorescent CdSe/ZnS nanocrystals and to verify the occurrence of resonance energy transfer (FRET) among these elements. Two donor-acceptor pairs were established, one having a protein as donor and the other having a nanocrystal as donor. In both cases the donor suffers quenching of its fluorescence after the formation of a complex with the acceptor. The complex formation is dependent on pH and is due to electrostatic interaction. It was possible to prove the occurrence of FRET between CdSe/ZnS nanocrystals emitting green fluorescence as donors and the protein HcRed1 as acceptor, through the detection of sensitized emission and anisotropy reduction. Apparent donor-acceptor distances were determined from efficiency measurements and Förster distances. The obtained distances agreed with the protein and nanocrystal dimensions
Shen, Yaoming. "Photoluminescence spectral study of single CdSe/ZnS Colloidal Nanocrystals in Poly(methyl methacrylate) and Quantum Dots molecules". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2008. http://wwwlib.umi.com/cr/ucsd/fullcit?p3304209.
Texto completoTitle from first page of PDF file (viewed June 17, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 91-99).
Smirnova, T. N., J. Stumpe, О. V. Sakhno, L. M. Kokhtych y P. V. Yezhov. "Stimulated emission of CdSe/ZnS nanocrystals in polymer dfb structure obtained by holographic ordering of polymer nanocomposite". Thesis, Видавництво СумДУ, 2011. http://essuir.sumdu.edu.ua/handle/123456789/20586.
Texto completoChevallier, Théo. "Photoluminescence et couplage plasmonique des nanocristaux d'AgInS2-ZnS". Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAY092/document.
Texto completoAgInS2-ZnS nanocrystals are promising materials for the development of non-toxic, highly efficient nano-phosphors. Their size and strong absorption allow them to exploit nano-optical effects potentially enhancing both their absorption and emission processes. This work presents a method combining quantum yield measurements with time resolved emission spectroscopy allowing for the study of both radiative and non-radiative properties of each recombination pathways. Modifying the size, surface chemistry, and core structure of the nanocrystals, we construct a global model explaining the role of their composition and emphasizing the critical aspect of their surface. New strategies are identified to increase the internal quantum yield of these materials. Combining these approaches, it is now possible to expect 90% efficiencies. In a second step, a simulation method was developed to predict the nano-optical effects induced by a plasmonic nanostructure on a given phosphor. We applied this method on core/shell/shell (metal/insulator/AgInS2-ZnS) nanostructures and theoretically determined optimal configurations of the system. A particularly efficient nanostructure achieving coupling on both absorbed and emitted light is identified. Hybrid plasmonic nanostructures are synthesized. Their performances are in accordance with both our understanding of the fluorescence mechanisms of AgInS2-ZnS nanocrystals and the predictions made via simulation
Santos, Yane Honorato. "Síntese e caracterização de nanocristais de ZnO suportados e não suportados em diatomita e aplicação fotocatalítica". Universidade Federal de Sergipe, 2017. https://ri.ufs.br/handle/riufs/6076.
Texto completoCurrently there are many studies involving Nanocrystals (NC) incorporated into different types of matrices, including, matrices with porous surface. However, little information is known about the incorporation of NC in Diatomite matrix, and there is a lack of studies on the use of this material. In this context, zinc oxide (ZnO) semiconductor nanoparticles were prepared using two sol-gel methods, microwave and autoclave, at 100 ºC and 180 ºC, respectively. The nanocrystals of ZnO obtained by microwaves were incorporated into a matrix of diatomite (DE) in natura and modified. The modifiers used were APTES (3- aminopropyltriethoxysilane) and MPTS (3-Mercaptopropyltrimetoxysilane) for the study. The material DE/ ZnO, in which ZnO was synthesized with mercaptoethanol (ZnO: ME), was applied for the degradation of Methylene Blue (AM) dye, while ZnO, synthesized with diethyleneglycol (ZnO: DEG), was used for degradation of Rhodamine 6G dye (R6G) by photocatalysis. The results of UV-vis and FTIR spectra show that synthesis carried out by heating under adsorption method is more efficient for the incorporation of ZnO in Diatomite matrix. The FTIR spectra showed that the use of modifiers had no significant influence on the structure. According to the UV-Vis spectra, the DE / ZnO material was successful for application to AM photocatalysis and follows a pseudo-first order kinetics. The ZnO:DEG material used for degradation of R6G obtained higher efficiency due to the wide absorption in the UV-Vis of the photocatalyst material.
Atualmente existem diversos estudos envolvendo Nanocristais (NC) incorporados em matrizes de diferentes tipos, incluindo matrizes com uma superfície porosa. Entretanto, pouco se conhece sobre a incorporação de NC em matriz de Diatomita, além de ser limitado a presença de estudos sobre aplicação desse material. Neste contexto, foram preparadas nanopartículas semicondutoras de óxido de Zinco (ZnO) utilizando dois métodos sol-gel, por micro-ondas e autoclave, numa temperatura de 100 ºC e 180 ºC, respectivamente. Os nanocristais de ZnO obtidos por micro-ondas foram incorporados em matriz de Diatomita (DE) in natura e modificada. Foram utilizados os modificadores APTES (3-Aminopropiltrietoxissilano) e MPTS (3- Mercaptopropiltrimetoxissilano) para o estudo. O material de DE/ZnO, no qual o ZnO foi sintetizado com mercaptoetanol (ZnO:ME), foi aplicado para a degradação do corante Azul de Metileno (AM), enquanto o ZnO, sintetizado com dietilenoglicol (ZnO:DEG), não incorporado foi utilizado para degradação do corante Rodamina 6G (R6G) por fotocatálise. Os resultados de UV-Vis e FTIR mostram que a síntese realizada pelo método de adsorção sob aquecimento é mais eficiente para a incorporação de ZnO na matriz de Diatomita. Os espectros de FTIR mostraram que a utilização de modificadores não exerceu influência significativa na estrutura da DE. Segundo os espectros de UV-Vis, o material de DE/ZnO foi bem-sucedido para aplicação em fotocatálise de AM e segue uma cinética de pseudo-primeira ordem. O material de ZnO:DEG utilizado para degradação de R6G obteve maior eficiência devido a ampla absorção no UV-Vis do material fotocatalisador.
Ageh, Victor. "Processing, Structure and Tribological Property Relations of Ternary Zn-Ti-O and Quaternary Zn-Ti-Zr-O Nanocrystalline Coatings". Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc699894/.
Texto completoKim, Changsu. "Optical, laser spectroscopic, and electrical characterization of transition metal doped ZnSe and ZnS nano- and microcrystals". Birmingham, Ala. : University of Alabama at Birmingham, 2009. https://www.mhsl.uab.edu/dt/2009r/kim.pdf.
Texto completoTitle from PDF title page (viewed Feb. 3, 2010). Additional advisors: Renato Camata, Derrick Dean, Chris M. Lawson, Andrei Stanishevsky, Sergey Vyazovkin. Includes bibliographical references (p. 133-140).
Biadala, Louis. "Propriétés optiques de nanocristaux de CdSe/ZnS individuels à basse température". Phd thesis, Université Sciences et Technologies - Bordeaux I, 2010. http://tel.archives-ouvertes.fr/tel-00654493.
Texto completoMao, Baodong. "Synthesis and Property Characterization of Novel Ternary Semiconductor Nanomaterials". Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1334065821.
Texto completoLemarchand, Alex. "Synthèse par chimie douce et étude structurale de nanocristaux d'oxydes métalliques". Thesis, Limoges, 2018. http://www.theses.fr/2018LIMO0110/document.
Texto completoThe aim of this work was to synthesize small size (~1-3 nm) metal oxide nanocrystals namely titanium dioxide (TiO2), tin dioxide (SnO2) and zinc oxide (ZnO), and to study their structure. Syntheses were conducted via non-aqueous or even strictly non-hydrolytic sol-gel methods under kinetic control. The structural characterization was mainly carried out by X-Ray diffraction methods, transmission electronic microscopy and the study of pair distribution functions, obtained by X Ray total scattering, coupled with atomic scale modelling methods. In the case of TiO2, anatase nanocrystals were obtained with sizes ranging between 4 nm and 8 nm. The molar ratio of the oxygen donor with respect to titanium was shown to be an important parameter to control the nanoparticle size. In peculiar conditions we have been able to isolate an intermediate phase characterized by very small sized and poorly crystallized nanoparticles which the structure can be assimilated to a disordered brookite structure. Concerning SnO2, rutile-type nanocrystals were synthesized with sizes ranging between 2 nm and 4 nm. The use of an ether as oxygen donor led to the simultaneous formation of an organic polymeric phase and of primary nanoparticles characterized by an intermediate structure close but still different from the rutile-type structure. Moreover, the use of benzyl-type solvents in the presence of tin tetrachloride led to the formation of water in the system. Lastly, for ZnO, we have shown that using an organic base to induce the formation of the metal oxide network in a methanolic solution of zinc acetate in the presence of a strong complexing agent of the zinc allowed us to obtain wurtzite nanocrystals of ultrasmall sizes around 1 nm. Even for the smallest sizes, the nanoparticles exhibit a structure very close to that of wurtzite with an increasing disorder of the cationic network
Trenkmann, Ines. "Mikroskopie und optische Spektroskopie an heterogenen Nano- und Mikrostrukturen: Halbleiter-Nanokristalle, molekulare Farbstofffilme und funktionalisierte Hybridstrukturen". Doctoral thesis, Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-175178.
Texto completoGrimes, Logan. "DEVELOPENT OF A PHOSPHOLIPID ENCAPSULATION PROCESS FOR QUANTUM DOTS TO BE USED IN BIOLOGIC APPLICATIONS". DigitalCommons@CalPoly, 2014. https://digitalcommons.calpoly.edu/theses/1237.
Texto completoChi-HengChen y 陳佶亨. "ZnO-based Light Emitting Device with sputtering ZnO nanocrystal". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/78770327860966603623.
Texto completoParamesh, Gadige. "Investigations into the Structural and Physical Properties of Li2O-M2O-2B2O3 (M=Li, Na & K), BaO-TiO2-B2O3 and 2Bi2O3-B2O3 Glass Systems". Thesis, 2013. http://etd.iisc.ernet.in/2005/3356.
Texto completoChitara, Basant. "Properties And Applications Of Semiconductor And Layered Nanomaterials". Thesis, 2012. http://hdl.handle.net/2005/2288.
Texto completoLiu, Kun-ho y 劉昆和. "Growth process and physical characteristics of Zn-ZnO nanocrystals via thermal reduction". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/10340217199073828599.
Texto completo國立交通大學
材料科學與工程系
91
Novel hierarchical polygon prismatic nano-structures of wurtzite Zn-ZnO have been successfully grown on silicon by thermal vapor transport and condensation method. Generally, the crystalline phase and control of the seeds at the nucleating stage are critical for directing the intrinsic shapes of nanocrystals at the initial time. Thus, in this work, the organic solvent with zinc chemical compound was first coated and used as seeds on the patterned substrate. Subsequently, it was grown by thermal vapor transport with ZnO powder at 250°C (substrate) in Ar atmosphere. The samples were characterized using X-ray diffraction, scanning and transmission electron microscopy, and photoluminescence spectroscopy. The as-synthesized Zn-ZnO polygon prismatic nano-structure consisted of hexagonal metallic nuclei (Zn) covered with an oxidation outer thin film (ZnO). Depending on different working temperature and reaction atmosphere, Zn- ZnO polygon prismatic structure having various morphologies can be developed. In order to recognize the growth mechanism of Zn-ZnO polygon prismatic structure and temperature effect, different heat-treatment were designed to observe the morphology and crystallization of Zn-ZnO polygon prismatic structure. The possible formation mechanism for the Zn-ZnO polygon prismatic crystal structure is identified and proposed as the Zn-ZnO mineral bridge mechanism. The non-perfect Zn-ZnO polygon prismatic structure shows weakly UV emission and strongly deep-level emission. However, the PL properties and crystallization of Zn-ZnO polygon prismatic nanocrystals could be improved by suitable post-treatment.
李振銘. "Surface enhanced Raman scattering of ZnO Nanocrystals". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/01952674869145511890.
Texto completo國立彰化師範大學
光電科技研究所
101
This thesis is devoted to the study of surface enhanced Raman scattering of ZnO nanocrystals. The ZnO nanocrystals were synthesized by a sol-gel method. Their sizes were controlled by the pH value and temperature of synthetic solutions. The results of transmission electron microscope analysis showed that the particle sizes ranged between 2.5 and 4.9 nm. The synthesized ZnO nanocrystals were further used to grown ZnO/Ag aggregated nanostructures. The results of Raman measurement of these nanostructures showed that the signal intensity of ZnO was significantly enhanced by a factor of 1000 as the concentration of silver nitrate was 1.0 mM. The E2-low Raman signal shifted as the ZnO particle size decreased. A relationship between particle size and signal shift was obtained. It agreed well with the theoretical prediction.
林昌麒. "Growth and Physical Properties of ZnO Nanocrystals". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/29261328384528619304.
Texto completo國立彰化師範大學
光電科技研究所
95
The purpose of the current study was to find out the most suitable conditions for the even-synthesized and highly-stabilized ZnO powder through various treatments. The various treatments manipulated in the study were through Sol-Gel method to synthesize ZnO Nanocrystals in different heating rates, synthesizing time, and the adding amount of capping agent (PVP).Moreover, techniques such as XRD, SEM, TEM, PL were also included in the study to measure the structures, surface state, and optic properties of ZnO Nanocrystal.According to the results of XRD, the samples were with the Wurtzite structures, with the particle size ranging between 3 ~ 4 nm. As for SEM, the results showed that the ZnO secondary particles were aggregated particles, with the particle size ranging from 200 ~ 500 nm. The pictures of TEM also proved that the real size of secondary particles ranged between 3 ~ 4 nm, and they were gathered by ZnO Nanocrystals. Its exact size was in accordance with the one calculated by X-ray diffraction. In the PL measurement, crystals were unstable under the excite of He-Cd laser, and the PL property would changed and emission effectiveness was lowered as time went by. Both the quality of X-ray diffraction and emission effectiveness had significant promotion after the change of process variables such as the addition of capping agent, which redeemed its surface state.In the study of PL spectrum, the impurity bound exciton of ZnO QDS( ~ 7.5 nm) was found out to be 18.31meV, while the activation energy of it was 94.5meV. In addition, three equations, Vashni, O'Donnell, and Pässler were employed to fit the different bandgaps in different temperature of quantum dots, blocks, and nanoparticles. Therefore, the found parameters may provide help to the further studies on ZnO.
Viswanatha, Ranjani. "Growth Kinetics And Electronic Properties Of Semiconducting Nanocrystals In The Quantum Confined Regime". Thesis, 2006. http://hdl.handle.net/2005/403.
Texto completo徐意娟. "High-pressure raman study of wide-band gap ZnO-and GaN-nanocrystals". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/57435623963996277757.
Texto completoRakshit, Sabyasachi. "Resonance Energy Transfer Using ZnO Nanocrystals And Magnetism In The Mixed Metal Layered Thiophosphates, Mn1-xFexPS3(0≤x≥1)". Thesis, 2009. http://etd.iisc.ernet.in/handle/2005/2156.
Texto completoLin, Xi-Cong y 林熙琮. "Synthesis and Optical Properties of Mn2+ Doped ZnS Nanocrystals". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/33984445122788205353.
Texto completo國立彰化師範大學
光電科技研究所
94
Mn2+ doped ZnS nanocrystals were synthesized by chemical method. The structure, morphology and optical properties of these nano-particles were studied by the means of X-ray diffraction (XRD), transmission electron microscope (TEM), photoluminescence (PL) and photoluminescence excitation (PLE) measurements. The XRD patterns showed the structure of the ZnS:Mn nanocrystals is zinc-blende. From the XRD and TEM results, the size of these narocrystals was estimated at about 3 ~4 nm. From the PL spectra, two emission peaks were observed. One is the orange emission (about 590 nm) which is due to the 4T1-6A1 characteristic transition in the Mn2+ ions, the other is the broad blue emission (from 410~500 nm) which can be attributed to the S vacancies in the ZnS nanocrystals. The PL spectra also showed that the emission intensity of samples increases as the Mn2+ concentration increases up to 4 % and then decreases. The surfactant effect on the luminescence intensity was also studied. It was found that the adding of surfactant in the synthesis process can increase the luminescence intensity efficaciously. The energy gap of the ZnS:Mn nanocrystals was determined by the PLE spectra. It was found to increase as the crystal size decreases. This blue shift of the PLE peaks is due to the quantum confinement effect of nanocrystals. Irradiation-induced luminescence enhancement effect was observed. The luminescence intensity of fresh samples was increased under irradiation by 325 nm He-Cd laser beam. From the temperature-dependent PL spectra, a blue shift of the Mn2+ ions emission peaks was observed as the temperature increased. This phenomenon could be attributed to the variation of crystal-field strength. The temperature dependence of the PL spectra of samples with surfactant was different to that without surfactant. The luminescence intensity of samples with surfactant increases as the temperatire increases. However, for the samples without surfactant, the luminescence intensity deccreaes as the temperature increases.
Lin, Jian-Hao y 林建豪. "Study of luminescent mechanisms of silicon nanocrystals embedded in SiOX matrix、ZnO and In2Se3 semiconductors". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/85295411427980655551.
Texto completoYang, Nai-Hao y 楊乃豪. "Spontaneous growth and mechanism of stress-induced ZnO nanocrystals in ambient atmosphere at room temperature". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/06289895388974558473.
Texto completo國立清華大學
材料科學工程學系
102
One-dimensional oxide-based nanostructures have been intensively studied because of their excellent optoelectronic properties. Due to the drawbacks of vapor-phase or aqueous solution growth, including complex processes, high synthesis temperatures, expensive precursors, and also preceding patterned seeding or subsequent patterning processes, there is an urgent need to grow patterned nanostructures by a simple and direct process at low temperatures. In the present study, stress-induced growths of one-dimensional single-crystalline ZnO and TiO2 nanostructures directly from ZnO and TiO2 films, respectively, in an ambient atmosphere at room temperature were developed by indentation or scratching without the use of any reaction precursors. Under large applied stresses oxide bonds broke assisted by hydrolysis in the presence of moisture, and subsequently were reconstructed (defined as a bond breaking-hydrolysis-reconstruction mechanism) leading to the spontaneous growth of one-dimensional nanocrystals. The direct growth at controlled locations provides an opportunity for the simple preparation of patterned nanostructures of oxide-based materials.
Lu, Yi-Hsuan y 路逸宣. "A Facile Green Antisolvent Approach to Cu2+-doped ZnO Nanocrystals with Visible-Light-Responsive Photoactivities". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/57993268221076207765.
Texto completo國立交通大學
材料科學與工程學系所
102
With the particular optoelectronic characteristics and excellent physicochemical properties, ZnO nanocrystals have been applied to extensive fields. However, the large band gap of ZnO (~3.35eV) prohibits it from effective light absorption under sunlight irradiation, which further limits its applicability in relevant photoelectric processes. To render visible light absorption thus becomes an essential task for the further advancement of ZnO. In this work, an environmentally benign antisolvent method has been developed to prepare transition metal ion-doped ZnO nanocrystals. A room-temperature ionic liquid, known as deep eutectic solvent (DES), was used as the solvent to dissolve ZnO powders. Upon the introduction of ZnO-containing DES into a bad solvent which shows no solvation to ZnO (e.g. water), ZnO was precipitated and grown due to the dramatic decrease of solubility. By adding transition metal ions such as Cu2+, Ni2+ and Co2+ in the bad solvent, the growth of ZnO in antisolvent process was accompanied by metal ion doping, resulting in the formation of metal ion-doped ZnO nanocrystals. The thus-obtained metal ion-doped ZnO showed additional absorption band in visible range (400-800 nm), attributable to the doped ions which invoke the interband transitions within the energy gap of ZnO to enable photoresponse to visible light. The doped ions may generate dopant states to trap charge carriers in the charge transfer process, leading to a depressed photoconversion efficiency for ZnO. Photoelectrochemical water splitting experiments showed that the photoactivity of the Cu2+-doped ZnO achieved the highest at the Cu2+ concentration of 2.0 at%, above which the photocatalytic performance was declined as a result of the significant charge carrier trapping at the dopant states. Furthermore, owing to the significant sp-d interaction between Cu2+ and ZnO, the Cu2+-doped ZnO samples exhibited obvious hysteresis loop at 300K with the saturated magnetization increasing with the increase of Cu2+ concentration.
黃國賓. "Applications of combining iron disulfide nanocrystals with P3HT, PCBM for inorganic/organic hybrid photovotaic device, and with ZnO nanocrystals for all-inorganic hybrid photovoltaic". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/31038130056779427529.
Texto completoChang, Chun-Jung y 張峻榮. "ZnO nanocrystals incorporating PEIE/polyfluorene electrolyte as electron transport layers for cesium-containing perovskite light-emitting devices". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/5bkvhq.
Texto completo國立交通大學
照明與能源光電研究所
107
In this work, we demonstrate inverted perovskite light-emitting devices (PeLEDs) based on ZnO nanocrystals (NCs) and cesium lead bromide (CsPbBr3) film as the electron transport and emission layers, respectively. A polyethyleneimine ethoxylated (PEIE) and/or an ionic polyfluorene electrolyte containing trimethylammonium hexafluorophosphate groups (namely P2-PF6) were introduced between ZnO NCs and CsPbBr3 film to enhance electron injection. The introduction of the PEIE/P2-PF6 bilayer can effectively improve CsPbBr3 coverage and morphology, thereby reducing current leakage in PeLEDs. Meanwhile, the improved CsPbBr3 film showed better photoluminescence, owing to anti-quenching capability of the PEIE/P2-PF6 and prolonged carrier lifetime. Herein, the PeLEDs with the structure ITO/ZnO NCs/ PEIE/P2-PF6/CsPbBr3 film/poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenyl amine) (TFB)/Au were fabricated, employing TFB as the hole transport layer. The PeLED based on the PEIE/P2-PF6 showed a turn-on voltage of 2.8 V, a max luminance of 3,927 cd/m2 and max current efficiency of 0.2 cd/A that was significantly higher than those without PEIE/P2-PF6 bilayer.
鄭綿綿. "Stochastic reorientaion processes of defect-free surface-stabilized ferroelectric liquid crystal with and without doping of ZnO nanocrystals". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/59386089246203271952.
Texto completo國立交通大學
光電工程系所
97
The fluctuation-dissipation theorem unveils the importance of thermal molecular motion which always exists, even in thermal equilibrium, as a fluctuation. However, the underlying information of thermal fluctuation which appears to be random noise is a huge question mark that had been overlooked for years. This thesis study focuses on the discussion about the dynamics of molecular fluctuations in a specific condensed matter- the ferroelectric liquid crystals (FLC) with and without doping of nanocrystal ZnO. The dynamics of orientation director fluctuations is governed by the material properties of the liquid crystal. In this thesis, we first derive the relation between the scattered light intensity and fluctuations of the FLC director which, through some reasonable assumption, could be described as a stochastic equation of motion. After performing autocorrelation technique to the scattered light signals, we have come to realize that the internal fluctuation is characterized by a correlation function of relevant physical quantities of the FLC system fluctuating in thermal equilibrium. The measurement results lead to the fact of improved molecular alignment and faster response time in the SSFLC cell doped with ZnO nanocrystals.
Lin, Tai-Wei y 林泰瑋. "Synthesis of ZnO tetrapod nanocrystals on FTO glass substrate by furnace method and their application of dye-sensitized solar cells". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/67505275597859558614.
Texto completo國立臺灣海洋大學
光電科學研究所
98
Zinc oxide (ZnO) nano-tetrapods were deposited on FTO glass substrate at 500 ℃ by furnace method. The samples were used to combine with N-719 or N3 dyes to fabricate two kinds of dye-sensitized solar cells (DSSCs). Under the optimal conditions, an AM1.5 power conversion efficiency of 0.40% was achieved for N3 immersed DSSC and 0.68% was achieved for N-719 immersed DSSC, respectively. SEM images showed that we successfully grew the ZnO nano-tetrapods on FTO glass substrate at 500℃. The X-ray diffraction patterns confirm that the ZnO tetrapods are quasi-aligned predominantly with (002) orientation. The photoluminescence (PL) spectra of the ZnO tetrapods exhibit the near band-edge emission at 3.2 eV with no discernible defect emission, and this confirmed that our ZnO tetrapods are of good crystallinity. The ZnO nano-tetrapods grown at 500 ℃ have larger surface area than the simple one dimensional nanostructures, and then offer the lager area for dye adsorptions. With the larger surface area and higher crystalline quality, the DSSCs based on our ZnO nano-tetrapods show the good overall conversion efficiency.
Chen, Hsiang-Yun. "Energy Transfer Dynamics and Dopant Luminescence in Mn-Doped CdS/ZnS Core/Shell Nanocrystals". Thesis, 2012. http://hdl.handle.net/1969.1/148167.
Texto completoChen, Yi-Han y 陳弈翰. "Effect of Zn Content on Optical Properties of ZnxCd1-xSe Nanocrystals". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/5zu2ve.
Texto completo國立虎尾科技大學
材料科學與綠色能源工程研究所
99
In the recent two decades, II-VI semiconductor nanocrystals (NCs) have been researched widely due to their controllable emission wavelength and high theoretical quantum yield (QY). The optical properties of the binary NCs are the main stream in the past, however, ternary alloying process become more and more important because the different color-emitting NCs can be prepared not only by changing the particle size but composition in recent years. In this study, one-step synthesis route is used and a series of high quality ZnxCd1-xSe (x=0, 0.2, 0.5, 0.8 and 1) alloyed NCs are prepared by changing the molar ratios of ZnO and CdO. The effect of Zn content and the mechanism of QY decay are discussed. The results show that emission wavelength of NCs are shifted from 510 (x=0) to 545 nm (x=0.8) and particle size are 3.1±0.32, 3.1±0.27, 3.2±0.31, and 3.3±0.28 nm with increasing Zn content, however, ZnSe NCs cannot be prepared under this condition. In addition, the QYs of samples are 64, 89, 81, and 45 %, respectively. The result reveals that the emission wavelength of NCs is increased with increasing the amount of Zn under the same particle size. It means that the nonlinear optical properties can be observed and the red shift phenomenon is not caused by the particle size. In order to confirm the effect of Zn, the actual element compositions are measured by ICP-AES. The result shows that the actual compositions of samples are CdSe, Zn0.03Cd0.97Se, Zn0.11Cd0.89Se, Zn0.38Cd0.62Se, respectively. We can conclude that the red shift of emission position is caused by composition rather than particle size. Furthermore, QY can be promoted by partial replaced Cd with Zn and a high QY can be obtained under lower Zn content. When prolonging reaction time to 5 min, an obvious blue shift of emission wavelength is observed and a lower QY can be obtained. When the samples are aging for two months, the average particle sizes is 4.2±0.53, 5.8±1.26, 4.3±0.56, and 4.2±0.57 nm and QYs is 15, 30, 18, and 9 %, respectively. However, the emission position for all aging samples is not changed compared with as-prepared samples. The QYs decrease with increasing time due to surfactant, which capped on the surface of NCs, is flopped. Besides, the particle size distribution becomes wider, which is caused by Ostwald ripening effect.
Hazarika, Abhijit. "Photophysical Properties of Manganese Doped Semiconductor Nanocrystals". Thesis, 2015. http://etd.iisc.ernet.in/2005/3675.
Texto completoHuynh, Uyen Nguyen Phuong. "Hybrid Photovolvoltaic Devices Based on Nanocrystals and Conducting Metallopolymers Using the Seeded Growth Method". Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-08-3917.
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