Thèses : « Doped Nanostructures »

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Martin, Shashi A. « Computation of conductance for ballistic nanostructures ». Virtual Press, 1994. http://liblink.bsu.edu/uhtbin/catkey/917024.

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Future electronic devices having dimensions on the nanometer scale will rely on the resultant quantum effects for their operation. In this project, these quantum effects were investigated through the theoretical modeling and computer simulation of a confined twodimensional electron gas in a semiconductor heterostructure. Assuming hardwall boundaries and sharp geometrical features, the nanostructure conductance has been calculated by finding transverse eigenvalues and eigenfunctions, computing hopping integrals for a one-dimensional tight binding lattice, determining the Greens' propagators, and then finally evaluating the transmittance. From the transmittance, the conductance was determined.A structured and modular computer program in FORTRAN was developed to investigate the effects of geometrical modifications on the conductance of ballistic nanochannels. The program has been designed in such a way that the user need only supply the nanostructure specifications to an input data file. The program then uses this data file to perform the calculations. A separate, user-friendly program has been developed to form the data file. The program is such that additions and modifications can be easily made in the future.
Department of Physics and Astronomy

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Hamza, Taha Mohamed. « Doped ZnO nanostructures for Mid Infrared plasmonics ». Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEC051/document.

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L'objectif de ce travail est de réaliser des substrats pour l’effet SEIRA (surface enhanced IR absorption) pour mesurer de faibles volumes de gaz ambiants possédant une signature moléculaire de 3,3 μm à 5,1 μm en exploitant la forte amplification de champ électrique due à la résonance plasmon de surface localisés. A cette fin, nous avons démontré la modulation des résonances de plasmon de surface localisées MIR (LSPR) dans les nanocristaux de ZnO dopés (NCs) dopés à Ga ou Al ainsi que dans des nanofils (NWs) de ZnO dopés Ga (GZO) et dans des nanofils coeur/coquille de ZnO/GZO. En ce qui concerne l’accordabilité de MIR LSPR dans les NC, nous avons modulé la résonance plasmon de surface dans des NC de ZnO dopés Ga et Al, de 3 à 5 μm en faisant varier la teneur en Al et en Ga de 3 à 9 at.%. L’incorporation des dopants s’est révélée homogène jusqu’à 6%. Au-delà (9%), l’incorporation était fortement hétérogène, révélant que la limite de solubilité était atteinte. Les NC présentent une faible activation des impuretés. L'activation était aussi faible que 8%. Les LSPR présentaient également un fort élargissement (largeur-à-mi-hauteur FWHM). Pour accroitre l'activation des dopants, nous avons synthétisés les NC dans des conditions pauvres en O et en passivant les NC synthétisés dans des conditions riches en O (en les isolant dans des matrices telles que Al2O3 et SiO2). Nous avons ainsi augmenté l'activation de 8% à 20% pour les deux stratégies. De plus, l'incorporation des NC dans les matrices a réduit l'élargissement spectral de moitié (de 2200 cm-1 pour les NC déposés à 1100 cm-1 pour les NC noyés en matrice). En correspondance, les effets d’auto-assemblage des nanocristaux sur leur LSPR ont été modélisés par simulation FDTD. Cela a fourni des indications quant aux mécanismes responsable de l’élargissement inhomogènes des LSPR de nanocristaux de GZO. Outre les nanoparticules, nous avons étudié des nanofils ZnO dopés Ga (GZO) et coeur/coquille (ZnO/GZO) synthétisés par CVD d’organométalliques . La première conclusion importante est que le gallium produit un fort effet surfacatnt lors de la croissance MOCVD de GZO. Au lieu de former des nanofils de section hexagonale, l’introduction de Ga modifie nettement l’énergie de surface des faces latérales et conduit à al formation de structures de type « sapins de Noël ». Ce constat est aussi valable pour les coquilles de GZO déposées sur coeur de ZnO. Dans ce cas, les coquilles démouillent et forment des structures hiérarchiques en branches. Concernant les propriétés optiques de ces objets, les mesures de FTIR-photo acoustiques ont démontré une signature d’absorption reliée à la présence de Ga et pouvant être accordée selon la teneur en Ga. Cette absorption reproduit le comportement d’une résonance plasmon de surface. Cette résonance a pu être accordée de 1600 à 1900 cm-1
The scope of this thesis is about developing SEIRA (surface enhanced IR absorption) platform to probe low volumes of environmental gases that possess molecular signature from 3.3 μm to 5.1 μm leveraging the high field amplification of localised surface plasmon resonance (LSPR). To realise SEIRA, we demonstrated tuning MIR LSPR in Al or Ga doped ZnO nanocrystals (NCs) as well as in GZO or core-shell (ZnO/GZO) nanowires (NWs). Regarding tuning MIR LSPR in NCs, we demonstrated tunable MIR LSPR in Ga and Al doped ZnO NCs from 3 to 5 μm varying the Al or Ga content from 3 to 9 at.%. The incorporation of dopant was homogeneous up to 6%. At 9% dopant concentration, the incorporation was inhomogeneous, revealing the solubility limit has been reached. However, the NCs exhibited low activation of impurities. The activation was as low as 8%. The LSPR were characterised by large broadening as well. In order to enhance the dopant activation, we synthesized the NCs in O-poor conditions as well as passivated the NCs fabricated in O-rich condictions (by isolating and embedding them in matrices such as Al2O3 and SiO2 matrices). Both strategies improved the dopant activation from 8% up to 20%. Moreover, for assemblies of NCs dispersed in matrices, the broadening (FWHM) of the LSPR was reduced by half (from 2200 cm-1 in as-deposited NCs to 1100 cm-1 in embedded NCs). Correspondingly, the effect of the self-assembly of the nanocrystals on their LSPR was modeled by FDTD simulation and provided hindsight into the mechanisms responsible for the heterogeneous broadening of the LSPR. Finally, we have studied Ga-doped ZnO (GZO) and core-shell (ZnO/GZO) NW synthesized by MOCVD. The first important conclusion is that Ga plays a major surfactant role during the MOCVD growth of GZO. Instead of leading to hexagonal NWs, the introduction of Ga during the synthesis led to faceted “Christmas-tree” like architectures. The same observation held for core-shell ZnO-GZO nanowires; in the latter case, the GZO shell resulted in a dewetting branched architecture. Regarding their optical properties, photo-acoustic FTIR measurements revealed an absorption feature related to the Ga content, likely to be assigned to a plasmonic effect. This resonance could be tuned from 1600 to 1900 cm

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Marchesini, Matteo. « Plasmon decay dynamics in hybrid metal/doped-semiconductor nanostructures ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23223/.

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The study of interactions between plasmonic nanomaterials and dielectrics is a thriving field of research, which in recent years proved that such nanostructures can be applied in a wide range of applications, from sensing to catalysts. These are all based on the nanoscale surface interactions happening between the nanomaterials and their surrounding environment. In this thesis, the possible interaction between plasmonic nanoparticles and the V doping states in the Anatase (TiO_2) bandgap, rather than in their undoped counterpart, is studied. The aim is to better understand the dynamics of these phenomena, and obtaining insights on the V states position in the TiO_2 bandgap. The work done encompasses all the steps needed to achieve the experimental results: from the preparation and characterisation of the samples, to the simulations of the phenomena involved, until the actual measurements of their optical properties and the discussion of the results. The findings achieved are not decisive in explaining the dynamics involved, but preliminary interpretations could be formulated. Moreover, the specific investigations displayed in this thesis have never been done before in literature, and the work performed might be used in the future as a starting point for more thorough and deep studies of these phenomena.

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Fung, Man-kin, et 馮文健. « Fabrications of tin-doped indium oxide nanostructures and their applications ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B47849459.

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Tin-doped indium oxide (ITO) has been widely used for various optoelectronic devices such as display panels, light-emitting diodes and solar cells due to its unique optical and electrical properties. Thin ITO films can be fabricated by a number of methods such as molecular beam epitaxy (MBE), laser ablation, dc sputtering, e-beam deposition, vapor phase deposition, electrochemical deposition and hydrothermal method. Apart from the conventional thin film form, one dimensional ITO nanorods or nanowires are attracting much research interest due to their high aspect ratio and large surface to volume ratio. For instance, a network made of ITO nanowires can exhibit high transparency (over 95 %) and high flexibility without losing its conducting property as reported recently. This network can be potentially used for flexible photovoltaic devices. In this study, ITO nanorods or nanowires were fabricated using the vapor deposition, dc sputtering and e-beam deposition. The use of short ITO nanorods (100 nm) on glass and commercial ITO substrates as bottom electrodes improving the charge collection of bulk heterojunction organic solar cells had been demonstrated. The morphology of the ITO nanostructures was studied by scanning electron microscope (SEM) and transmission electron microscope (TEM). The crystal structure and growth direction were studied by x-ray diffraction (XRD) and selected area electron diffraction (SAED), respectively. Optical properties were examined using transmission and photoluminescence measurements. The performance of the organic solar cells was examined using the I-V characteristics and external quantum efficiency (EQE) measurements. The growth mechanism of the ITO nanowires using different fabrication methods was discussed. The effects of the substrate temperature, oxygen content, choice of substrate and evaporation rate on the morphology, transmittance and sheet resistivity were investigated. When short ITO nanorods were incorporated into the bulk heterojunction organic solar cells, a significant improvement of the power conversion efficiency (PCE) was observed. The higher efficiency of the studied solar cells was attributed to the improved charge collection.
published_or_final_version
Physics
Doctoral
Doctor of Philosophy

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Sharifi, Tiva. « Efficient electrocatalysts based on nitrrogen-doped carbon nanostructures for energy applications ». Doctoral thesis, Umeå universitet, Institutionen för fysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-100676.

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Carbon nanostructures have emerged as a key material in nanotechnology and continuously find new areas of applications. Particularly, they are attractive due to their excellent properties as support for catalyst nanostructures leading to highly efficient composite materials for various electrochemical applications. The interest in these structures is further increased by the possibility to alter their electronic and structural properties by various methods. Heteroatom doping of carbon nanostructures is one of the approaches which may induce intrinsic catalytic activity in these materials. In addition, such introduction of guest elements into the hexagonal carbon skeleton provides strong nucleation sites which facilitate the stabilization of nanostructures on their surface. In this thesis we present detailed studies on the nitrogen incorporation into carbon nanostructures, particularly carbon nanotubes and reduced graphene oxide. Due to the high impact of nitrogen configuration on the intrinsic electrocatalytic properties of carbon nanostructures, we investigated the nitrogen functionalities using X-ray photoelectron spectroscopy and Raman spectroscopy. Based on our achievements we could assign the most electrocatalytic active nitrogen site in nitrogen-doped carbon nanotubes (NCNTs) for catalytic oxygen reduction reaction (ORR) which is an important reaction in energy conversion systems such as fuel cells. We then used nitrogen-doped carbon nanostructures as a key component to manufacture hybrid material, where the nitrogen doped nanostructures has a role of both stabilizing the nanostructures and to work as conductive additive to assist the charge transfer from the other constituents suffering from inherently poor conductivity. Our hybrid material comprising transition metal oxides (Fe2O3 and Co3O4) anchored on nitrogen-doped carbon nanostructure were used to both manufacture an exotic type of graphene nanoscrolls, as well as studied and evaluated as an electrocatalyst in various electrochemical reactions. We show that the self-assembled electrodes exhibited better performance and higher stability compared to when the same material was loaded on common current collectors such as fluorine tin oxide (FTO) coated glass and glassy carbon electrode, with both higher current densities, more efficient charge transfer and lower overpotentials for oxygen evolution and hydrogen evolution reactions, the two important processes in a water splitting device. Our NCNTs-based electrodes showed further excellent performance in lithium ion batteries with high cyclability and capacity. The thesis gives insight into processes, materials, and methods that can be utilized to manufacture an efficient water splitting device, based on earth-abundant self-assembled materials. It further represents a significant advancement of the role of nitrogen in heteroatom-doped nanostructures, both regarding their intrinsic catalytic activity, as well as their role for stabilizing nanostructures.

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Chey, Chan Oeurn. « Synthesis of ZnO and transition metals doped ZnO nanostructures, their characterization and sensing applications ». Doctoral thesis, Linköpings universitet, Fysik och elektroteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-113237.

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Nanotechnology is a technology of the design and the applications of nanoscale materials with their fundamentally new properties and functions. Nanosensor devices based on nanomaterials provide very fast response, low-cost, long-life time, easy to use for unskilled users, and provide high-efficiency. 1-D ZnO nanostructures materials have great potential applications in various sensing applications. ZnO is a wide band gap (3.37 eV at room temperature) semiconductor materials having large exciton binding energy (60 meV) and excellent chemical stability, electrical, optical, piezoelectric and pyroelectric properties. By doping the transition metals (TM) into ZnO matrix, the properties of ZnO nanostructures can be tuned and its room temperature ferromagnetic behavior can be enhanced, which provide the TM-doped ZnO nanostructures as promising candidate for optoelectronic, spintronics and high performance sensors based devices. The synthesis of ZnO and TM-doped ZnO nanostructures via the low temperature hydrothermal method is considered a promising technique due to low cost, environmental friendly, simple solution process, diverse 1-D ZnO nanostructures can be achieved, and large scale production on any type of substrate, and their properties can be controlled by the growth parameters. However, to synthesize 1-D ZnO and TM-doped ZnO nanostructures with controlled shape, structure and uniform size distribution on large area substrates with desirable properties, low cost and simple processes are of high interest and it is a big challenge at present. The main purpose of this dissertation aims to develop new techniques to synthesize 1-D ZnO and (Fe, Mn)-doped ZnO nanostructures via the hydrothermal method, to characterize and to enhance their functional properties for developing sensing devices such as biosensors for clinical diagnoses and environmental monitoring applications, piezoresistive sensors and UV photodetector. The first part of the dissertation deals with the hydrothermal synthesis of ZnO nanostructures with controlled shape, structure and uniform size distribution under different conditions and their structural characterization. The possible parameters affecting the growth which can alter the morphology, uniformity and properties of the ZnO nanostructures were investigated. Well-aligned ZnO nanorods have been fabricated for high sensitive piezoresistive sensor. The development of creatinine biosensor for clinical diagnoses purpose and the development of glucose biosensor for indirect determination of mercury ions for an inexpensive and unskilled users for environmental monitoring applications with highly sensitive, selective, stable, reproducible, interference resistant, and fast response time have been fabricated based on ZnO nanorods. The second part of the dissertation presents a new hydrothermal synthesis of (Fe, Mn)-doped-ZnO nanostructures under different preparation conditions, their properties characterization and the fabrication of piezoresistive sensors and UV photodetectors based devices were demonstrated. The solution preparation condition and growth parameters that influences on the morphology, structures and properties of the nanostructures were investigated. The fabrication of Mn-doped-ZnO NRs/PEDOT:PSS Schottky diodes used as high performance piezoresistive sensor and UV photodetector have been studied and Fe-doped ZnO NRs/FTO Schottky diode has also been fabricated for high performance of UV photodetector. Finally, a brief outlook into future challenges and relating new opportunities are presented in the last part of the dissertation.

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Wang, LiQiu. « Quantitative three dimensional atomic resolution characterisation of non-stoichiometric nanostructures in doped bismuth ferrite ». Thesis, University of Glasgow, 2013. http://theses.gla.ac.uk/4364/.

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Over the last decade, the lead-free, environmentally-friendly multiferroic material, BiFeO3 (BFO), has once again received tremendous attention from researchers, not only for its fundamental properties, but also for its potential applications such as novel devices that can be written by an electric field and read by a magnetic field. However, one of the most important limitations for applications is the high leakage current in pure materials. Doping has proved to be an effective way to reduce the leakage current caused by the electron hopping between Fe2+ and Fe3+. In this work, a series of Nd3+ and Ti4+ co-doped BFO compositions have been studied using a combination of atomic resolution imaging and electron energy loss spectroscopy in STEM, especially concentrating on nanostructures within the Bi0.85Nd0.15Fe0.9Ti0.1O3 composition, as nanostructures can play an important role in the properties of a crystal. Two types of novel defects – Nd-rich nanorod precipitates and Ti-cored anti-phase boundaries (APBs) are revealed for the first time. The 3D structures of these defects were fully reconstructed and verified by multislice frozen phonon image simulations. The very formation of these defects was shown to be caused by the excess doping of Ti into the material and their impact upon the matrix is discussed. The nanorods consist of 8 atom columns with two Nd columns in the very center forming the Nd oxide. Density functional theory calculation reveals that the structures of the nanorod and its surrounding perovskites are rather unusual. The Nd in the core is seven coordinated by oxygen while the coordination of B site Fe3+ at its surroundings are just five-coordinated by oxygen due to the strain between the nanorod and the surrounding perovskite. The APB is nonstoichiometric and can be treated as being constructed from two main structural units - terraces and steps. Within the terraces, Ti4+ occupy the centre of the terrace with Ti/Fe alternately occupying either side of the terrace. As for the step, this is constructed from iron oxide alone with a structure similar to g-Fe2O3, and Ti is completely absent. Quantitative analysis of the structure shows the APB is negatively charged and this results in electric fields around the APBs that induce a local phase transformation from an antiferroelectric phase to a locally polarised phase in the perovskite matrix. Based on this thorough investigation of these defects, a new ionic compensation mechanism was proposed for reducing the conductivity of BiFeO3 without the complications of introducing non-stoichiometric nanoscale defects.

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Turner, Carrina Jayne. « Electrochemical deposition, characterisation and photovoltaic application of undoped and aluminium doped zinc oxide nanostructures ». Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/7122.

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Zinc oxide (ZnO) is an n-type II-VI semiconductor with a reported band gap of 3.2-3.6 eV [1, 2, 3] and electrical resistivity of ~ 50 Ωcm [4]. Ideal for use in devices such as Photovoltaics (PVs), Light Emitting Diodes (LEDs) and detectors, ZnO has the advantage that it can be electrochemically deposited. This enables the quick and cheap controlled growth of ZnO nanostructures, which can potentially enhance performance in electronic applications over thin films. ZnO doping with a group III element e.g. Aluminium, can increase ZnO conduction by several orders of magnitude whilst having only a subtle effect on its optical properties, therefore further enhancing device performance. For the first time, this thesis presents a unique in-depth study into the potentiostatic electrochemical deposition of well defined zinc oxide nanostructures (nanorods and platelets), their controlled aluminium doping and application in PV devices. This work addresses the mechanism of doping and examines the relationship between the opto-electronic properties, composition, structure, morphology and growth. The results show that arrays of crystalline wurtzite ZnO nanorods with strong (002) preferential orientation can be deposited on ITO and Au using a 1 mM Zn(NO3)2 system. Doping has been successfully carried out using Al(NO3)3 with a doping mechanism confirmed for the first time. This study shows that doped nanorods contain < 5 at. % Al3+, where Al3+ is incorporated in the ZnO lattice as interstitial and/or substitutional ions. This results in a subtle increase in the band gap, and is believed to increase the ZnO conduction by several orders of magnitude. The application of these nanorod arrays in PV devices has improved device efficiency by ~ 1080 %. Furthermore, platelets have been successfully deposited using a 5 mM Zn(NO3)2 system. A critical dopant content ~ 5 at. % Al3+ has been found, above which there is a transition in the doping mechanism towards spontaneous Al2O3 formation in addition to interstitial and substitutional Al3+ ion locations. This results in a gradual decrease in the optical band gap towards that of undoped ZnO. This mechanism occurs in platelets, where at. % Al3+ > 5 %. Platelet formation is associated with small quantities of impurities such as Al2O3, ZnCl2, Zn(ClO4)2 Zn5(OH)8Cl2.H2O and Au3Zn, arising from deposition conditions. Both impurities and dopants result in increased ZnO polycrystallinity and decreased ZnO (002) preferential orientation. The performance of PV devices with nanorod arrays has been shown to be better than previously reported equivalent thin film devices. This work illustrates the significance of electrochemical deposition as a technique for cheap and quick, controlled mass production of high quality tailor-made ZnO semiconductor nanostructures.

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Pijeat, Joffrey. « Anthracenylporphyrin based building blocks for the bottom-up fabrication of nitrogen-doped graphene nanostructures ». Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS346/document.

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La synthèse de graphène par approche « bottom-up » fait l’objet de nombreux travaux de recherche ayant pour but de contrôler les propriétés électroniques et optiques de ce matériau par la fabrication de nanostructures avec une précision atomique. D’autre part, le contrôle de dopant dans le graphène permettant d’en moduler les propriétés suscite un grand intérêt et dans ce contexte l’utilisation de porphyrines avec un taux d’azote contrôlé est attrayante. Par leurs ressemblances structurelles, les porphyrines π-étendues peuvent être considérées comme des nanoparticules de graphène dopées à l’azote (GQDs) présentant de fortes propriétés infrarouge tandis que les briques de construction à base de porphyrines peuvent être utilisées pour la synthèse sur surface de deux type de nanoarchitectures de graphene appélées nanorubans (GNRs) et nanomèches (GNMs). Cette thèse a pour objectif de développer la synthèse de porphyrines à base d’anthracenes et de les utiliser comme précurseurs pour la fabrication de nanostructures. La première partie de cette thèse est dédiée à la synthèse organique de différentes anthracenylporphyrines et à l’étude de leurs assemblages sur surface dans la chambre d’un microscope à effet tunnel. La seconde partie est dédiée à l’étude de formation de porphyrines π-étendues via une méthode pyrolyse flash pouvant activer thermiquement des réactions de couplage par déhydrogenation entre des hydrocarbures aromatiques polyycliques (PAHs) et des porphyrines. La dernière partie est dédiée à la modification post synthétique d’une tetrabromoanthracenylporphyrine par addition de PAHs via la réaction de couplage de Suzuki-Miyaura et à la caractérisation des propriétés optiques de ces porphyrines nouvellement formées
The synthesis of graphene via bottom-up approach is a hot topic of research that aims to control the electronic and optical properties of this material by the fabrication of atomically precised nanostructures. Moreover, the control of dopant in graphene is of great interest to modulate the properties of the material. In this context, the contribution of porphyrins with a controlled content of nitrogen is attractive in this context. Because of structural similarities with graphene quantum dots (GQDs), π-extented porphyrins can be regarded as nitrogen-doped GQD with promising NIR properties. Porphyrins are convenient building blocks for the synthesis on surface of nanoarchitectures of graphene called nitrogen-doped Graphene Nanoribbons (GNRs) and Graphene NanoMeshes (GNMs). This thesis aims to develop the synthesis of symmetrical and robust porphyrins with anthracenes and to use them as precursors for the fabrication of nanostructures. The first part of this thesis is dedicated to the organic synthesis of variety of anthracenylporphyrins and the study of their assemblies on surface in a chamber of a Scanning Tunneling Microscope. The second part is dedicated to the study of formation of π-extended porphyrins via a method of flash pyrolysis able to thermally activate dehydrogenative coupling reactions between Polycyclic Aromatic Hydrocarbons (PAHs) and porphyrins. The last part is dedicated to the post synthetic modification of a tetrabromoanthracenylporphyrin with additional PAHs via Suzuki-Miyaura coupling and the characterization of the optical properties of the resulting porphyrins

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Zhao, Yanyan. « Synthesis and characterisation of metal (Fe, Ga, Y) doped alumina and gallium oxide nanostructures ». Thesis, Queensland University of Technology, 2008. https://eprints.qut.edu.au/20529/1/Yanyan_Zhao_Thesis.pdf.

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It is well known that nanostructures possess unique electronic, optical, magnetic, ferroelectric and piezoelectric properties that are often superior to traditional bulk materials. In particular, one dimensional (1D) nanostructured inorganic materials including nanofibres, nanotubes and nanobelts have attracted considerable attention due to their distinctive geometries, novel physical and chemical properties, combined effects and their applications to numerous areas. Metal ion doping is a promising technique which can be utilized to control the properties of materials by intentionally introducing impurities or defects into a material. γ-Alumina (Al2O3), is one of the most important oxides due to its high surface area, mesoporous properties, chemical and thermal properties and its broad applications in adsorbents, composite materials, ceramics, catalysts and catalyst supports. γ-Alumina has been studied intensively over a long period of time. Recently, considerable work has been carried out on the synthesis of 1D γ-alumina nanostructures under various hydrothermal conditions; however, research on the doping of alumina nanostructures has not been forthcoming. Boehmite (γ-AlOOH) is a crucial precursor for the preparation of γ-Alumina and the morphology and size of the resultant alumina can be manipulated by controlling the growth of AlOOH. Gallium (Ga) is in the same group in the periodic table as aluminum. β-Gallium (III) oxide (β-Ga2O3), a wide band gap semiconductor, has long been known to exhibit conduction, luminescence and catalytic properties. Numerous techniques have been employed on the synthesis of gallium oxide in the early research. However, these techniques are plagued by inevitable problems. It is of great interest to explore the synthesis of gallium oxide via a low temperature hydrothermal route, which is economically efficient and environmentally friendly. The overall objectives of this study were: 1) the investigation of the effect of dopants on the morphology, size and properties of metal ion doped 1D alumina nanostructures by introducing dopant to the AlOOH structure; 2) the investigation of impacts of hydrothermal conditions and surfactants on the crystal growth of gallium oxide nanostructures. To achieve the above objectives, trivalent metal elements such as iron, gallium and yttrium were employed as dopants in the study of doped alumina nanostructures. In addition, the effect of various parameters that may affect the growth of gallium oxide crystals including temperature, pH, and the experimental procedure as well as different types of surfactants were systematically investigated. The main contributions of this study are: 1) the systematic and in-depth investigation of the crystal growth and the morphology control of iron, gallium and yttrium doped boehmite (AlOOH) under varying hydrothermal conditions, as a result, a new soft-chemistry synthesis route for the preparation of one dimensional alumina/boehmite nanofibres and nanotubes was invented; 2) systematic investigation of the crystal growth and morphology and size changes of gallium oxide hydroxide (GaOOH) under varying hydrothermal conditions with and without surfactant at low temperature; We invented a green hydrothermal route for the preparation of α-GaOOH or β-GaOOH micro- to nano-scaled particles; invented a simple hydrothermal route for the direct preparation of γ-Ga2O3 from aqueous media at low temperature without any calcination. The study provided detailed synthesis routes as well as quantitative property data of final products which are necessary for their potential industrial applications in the future. The following are the main areas and findings presented in the study: • Fe doped boehmite nanostructures This work was undertaken at 120ºC using PEO surfactant through a hydrothermal synthesis route by adding fresh iron doped aluminium hydrate at regular intervals of 2 days. The effect of dopant iron, iron percentage and experimental procedure on the morphology and size of boehmite were systematically studied. Iron doped boehmite nanofibres were formed in all samples with iron contents no more than 10%. Nanosheets and nanotubes together with an iron rich phase were formed in 20% iron doped boehmite sample. A change in synthesis procedure resulted in the formation of hematite large crystals. The resultant nanomaterials were characterized by a combination of XRD, TEM, EDX, SAED and N2 adsorption analysis. • Growth of pure boehmite nanofibres/nanotubes The growth of pure boehmite nanofibres/nanotubes under different hydrothermal conditions at 100ºC with and without PEO surfactant was systematically studied to provide further information for the following studies of the growth of Ga and Y doped boehmite. Results showed that adding fresh aluminium hydrate precipitate in a regular interval resulted in the formation of a mixture of long and short 1D boehmite nanostructures rather than the formation of relatively longer nanofibres/nanotubes. The detailed discussion and mechanism on the growth of boehmite nanostructure were presented. The resultant boehmite samples were also characterized by N2 adsorption to provide further information on the surface properties to support the proposed mechanism. • Ga doped boehmite nanostructures Based on this study on the growth of pure boehmite nanofibre/nanotubes, gallium doped boehmite nanotubes were prepared via hydrothermal treatment at 100ºC in the presence of PEO surfactant without adding any fresh aluminium hydrate precipitate during the hydrothermal treatment. The effect of dopant gallium, gallium percentage, temperature and experimental procedure on the morphology and size of boehmite was systematically studied. Various morphologies of boehmite nanostructures were formed with the increase in the doping gallium content and the change in synthesis procedure. The resultant gallium doped boehmite nanostructures were characterized by TEM, XRD, EDX, SAED, N2 adsorption and TGA. • Y doped boehmite nanostructures Following the same synthesis route as that for gallium doped boehmite, yttrium doped boehmite nanostructures were prepared at 100ºC in the presence of PEO surfactant. From the study on iron and gallium doped boehmite nanostructures, it was noted both iron and gallium cannot grow with boehmite nanostructure if iron nitrate and gallium nitrate were not mixed with aluminium nitrate before dissolving in water, in particular, gallium and aluminium are 100% miscible. Therefore, it’s not necessary to study the mixing procedure or synthesis route on the formation of yttrium doped boehmite nanostructures in this work. The effect of dopant yttrium, yttrium percentage, temperature and surfactant on the morphology and size of boehmite were systematically studied. Nanofibres were formed in all samples with varying doped Y% treated at 100ºC; large Y(OH)3 crystals were also formed at high doping Y percentage. Treatment at elevated temperatures resulted in remarkable changes in size and morphology for samples with the same doping Y content. The resultant yttrium doped boehmite nanostructures were characterized by TEM, XRD, EDX, SAED, N2 adsorption and TGA. • The synthesis of Gallium oxide hydroxide and gallium oxide with surfactant In this study, the growth of gallium oxide hydroxide under various hydrothermal conditions in the presence of different types of surfactants was systematically studied. Nano- to micro-sized gallium oxide hydroxide was prepared. The effect of surfactant and synthesis procedure on the morphology of the resultant gallium oxide hydroxide was studied. β-gallium oxide nanorods were derived from gallium oxide hydroxide by calcination at 900ºC and the initial morphology was retained. γ-gallium oxide nanotubes up to 65 nm in length, with internal and external diameters of around 0.8 and 3.0 nm, were synthesized directly in solution with and without surfactant. The resultant nano- to micro-sized structures were characterized by XRD, TEM, SAED, EDX and N2 adsorption. • The synthesis of gallium oxide hydroxide without surfactant The aim of this study is to explore a green synthesis route for the preparation of gallium oxide hydroxide or gallium oxide via hydrothermal treatment at low temperature. Micro to nano sized GaOOH nanorods and particles were prepared under varying hydrothermal conditions without any surfactant. The resultant GaOOH nanomaterials were characterized by XRD, TEM, SAED, EDX, TG and FT-IR. The growth mechanism of GaOOH crystals was proposed.

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Zhao, Yanyan. « Synthesis and characterisation of metal (Fe, Ga, Y) doped alumina and gallium oxide nanostructures ». Queensland University of Technology, 2008. http://eprints.qut.edu.au/20529/.

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It is well known that nanostructures possess unique electronic, optical, magnetic, ferroelectric and piezoelectric properties that are often superior to traditional bulk materials. In particular, one dimensional (1D) nanostructured inorganic materials including nanofibres, nanotubes and nanobelts have attracted considerable attention due to their distinctive geometries, novel physical and chemical properties, combined effects and their applications to numerous areas. Metal ion doping is a promising technique which can be utilized to control the properties of materials by intentionally introducing impurities or defects into a material. γ-Alumina (Al2O3), is one of the most important oxides due to its high surface area, mesoporous properties, chemical and thermal properties and its broad applications in adsorbents, composite materials, ceramics, catalysts and catalyst supports. γ-Alumina has been studied intensively over a long period of time. Recently, considerable work has been carried out on the synthesis of 1D γ-alumina nanostructures under various hydrothermal conditions; however, research on the doping of alumina nanostructures has not been forthcoming. Boehmite (γ-AlOOH) is a crucial precursor for the preparation of γ-Alumina and the morphology and size of the resultant alumina can be manipulated by controlling the growth of AlOOH. Gallium (Ga) is in the same group in the periodic table as aluminum. β-Gallium (III) oxide (β-Ga2O3), a wide band gap semiconductor, has long been known to exhibit conduction, luminescence and catalytic properties. Numerous techniques have been employed on the synthesis of gallium oxide in the early research. However, these techniques are plagued by inevitable problems. It is of great interest to explore the synthesis of gallium oxide via a low temperature hydrothermal route, which is economically efficient and environmentally friendly. The overall objectives of this study were: 1) the investigation of the effect of dopants on the morphology, size and properties of metal ion doped 1D alumina nanostructures by introducing dopant to the AlOOH structure; 2) the investigation of impacts of hydrothermal conditions and surfactants on the crystal growth of gallium oxide nanostructures. To achieve the above objectives, trivalent metal elements such as iron, gallium and yttrium were employed as dopants in the study of doped alumina nanostructures. In addition, the effect of various parameters that may affect the growth of gallium oxide crystals including temperature, pH, and the experimental procedure as well as different types of surfactants were systematically investigated. The main contributions of this study are: 1) the systematic and in-depth investigation of the crystal growth and the morphology control of iron, gallium and yttrium doped boehmite (AlOOH) under varying hydrothermal conditions, as a result, a new soft-chemistry synthesis route for the preparation of one dimensional alumina/boehmite nanofibres and nanotubes was invented; 2) systematic investigation of the crystal growth and morphology and size changes of gallium oxide hydroxide (GaOOH) under varying hydrothermal conditions with and without surfactant at low temperature; We invented a green hydrothermal route for the preparation of α-GaOOH or β-GaOOH micro- to nano-scaled particles; invented a simple hydrothermal route for the direct preparation of γ-Ga2O3 from aqueous media at low temperature without any calcination. The study provided detailed synthesis routes as well as quantitative property data of final products which are necessary for their potential industrial applications in the future. The following are the main areas and findings presented in the study: • Fe doped boehmite nanostructures This work was undertaken at 120ºC using PEO surfactant through a hydrothermal synthesis route by adding fresh iron doped aluminium hydrate at regular intervals of 2 days. The effect of dopant iron, iron percentage and experimental procedure on the morphology and size of boehmite were systematically studied. Iron doped boehmite nanofibres were formed in all samples with iron contents no more than 10%. Nanosheets and nanotubes together with an iron rich phase were formed in 20% iron doped boehmite sample. A change in synthesis procedure resulted in the formation of hematite large crystals. The resultant nanomaterials were characterized by a combination of XRD, TEM, EDX, SAED and N2 adsorption analysis. • Growth of pure boehmite nanofibres/nanotubes The growth of pure boehmite nanofibres/nanotubes under different hydrothermal conditions at 100ºC with and without PEO surfactant was systematically studied to provide further information for the following studies of the growth of Ga and Y doped boehmite. Results showed that adding fresh aluminium hydrate precipitate in a regular interval resulted in the formation of a mixture of long and short 1D boehmite nanostructures rather than the formation of relatively longer nanofibres/nanotubes. The detailed discussion and mechanism on the growth of boehmite nanostructure were presented. The resultant boehmite samples were also characterized by N2 adsorption to provide further information on the surface properties to support the proposed mechanism. • Ga doped boehmite nanostructures Based on this study on the growth of pure boehmite nanofibre/nanotubes, gallium doped boehmite nanotubes were prepared via hydrothermal treatment at 100ºC in the presence of PEO surfactant without adding any fresh aluminium hydrate precipitate during the hydrothermal treatment. The effect of dopant gallium, gallium percentage, temperature and experimental procedure on the morphology and size of boehmite was systematically studied. Various morphologies of boehmite nanostructures were formed with the increase in the doping gallium content and the change in synthesis procedure. The resultant gallium doped boehmite nanostructures were characterized by TEM, XRD, EDX, SAED, N2 adsorption and TGA. • Y doped boehmite nanostructures Following the same synthesis route as that for gallium doped boehmite, yttrium doped boehmite nanostructures were prepared at 100ºC in the presence of PEO surfactant. From the study on iron and gallium doped boehmite nanostructures, it was noted both iron and gallium cannot grow with boehmite nanostructure if iron nitrate and gallium nitrate were not mixed with aluminium nitrate before dissolving in water, in particular, gallium and aluminium are 100% miscible. Therefore, it’s not necessary to study the mixing procedure or synthesis route on the formation of yttrium doped boehmite nanostructures in this work. The effect of dopant yttrium, yttrium percentage, temperature and surfactant on the morphology and size of boehmite were systematically studied. Nanofibres were formed in all samples with varying doped Y% treated at 100ºC; large Y(OH)3 crystals were also formed at high doping Y percentage. Treatment at elevated temperatures resulted in remarkable changes in size and morphology for samples with the same doping Y content. The resultant yttrium doped boehmite nanostructures were characterized by TEM, XRD, EDX, SAED, N2 adsorption and TGA. • The synthesis of Gallium oxide hydroxide and gallium oxide with surfactant In this study, the growth of gallium oxide hydroxide under various hydrothermal conditions in the presence of different types of surfactants was systematically studied. Nano- to micro-sized gallium oxide hydroxide was prepared. The effect of surfactant and synthesis procedure on the morphology of the resultant gallium oxide hydroxide was studied. β-gallium oxide nanorods were derived from gallium oxide hydroxide by calcination at 900ºC and the initial morphology was retained. γ-gallium oxide nanotubes up to 65 nm in length, with internal and external diameters of around 0.8 and 3.0 nm, were synthesized directly in solution with and without surfactant. The resultant nano- to micro-sized structures were characterized by XRD, TEM, SAED, EDX and N2 adsorption. • The synthesis of gallium oxide hydroxide without surfactant The aim of this study is to explore a green synthesis route for the preparation of gallium oxide hydroxide or gallium oxide via hydrothermal treatment at low temperature. Micro to nano sized GaOOH nanorods and particles were prepared under varying hydrothermal conditions without any surfactant. The resultant GaOOH nanomaterials were characterized by XRD, TEM, SAED, EDX, TG and FT-IR. The growth mechanism of GaOOH crystals was proposed.

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Corral, Jessica Olga. « Preparation of rare-earth (Eu3+, Tb3+, and Yb3+) doped Y2O3 luminescent ceramics by the use of reverse micelles ». abstract and full text PDF (free order & ; download UNR users only), 2004. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1434067.

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13

Check, Michael Hamilton. « Synthesis and Characterization of Low Dimensionality Carbon Nanostructures ». University of Dayton / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1386089389.

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Long, Phan The. « Synthesis and characterization of Mn-Doped ZnO sprintronic materials : Polycrystalline ceramics, thin films, and nanostructures ». Thesis, University of Bristol, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492507.

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Recent theoretical calculations have predicted that ZnO doped with Mn exhibits room-temperature ferromagnetism. This has attracted intensive interest, because of its prospective applications in spintronic devices. However, experimental studies on Mndoped ZnO materials have revealed that their magnetic properties vary from the ferromagnetic through antiferromagnetic and spin-glass to the paramagnetic. This makes the question of the origin of ferromagnetism in Mn-ZnO materials become more complicated.

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SARTORETTI, ENRICO. « Doped ceria nanostructures for the oxidation of pollutants : investigations into the role of defect sites ». Doctoral thesis, Politecnico di Torino, 2021. http://hdl.handle.net/11583/2910076.

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BOMFIM, JUNIOR FRANCISCO A. « Producao e caracterizacao de vidros de oxidos de metais pesados dopados com terras-raras e nanoparticulas metalicas ». reponame:Repositório Institucional do IPEN, 2009. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9433.

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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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17

Skolem, Lotte Maria Beate. « Biosynthesis and characterization of Ti-doped silica-based Nanostructures formed by the Diatoms Pinnularia sp. and Coscinodiscus wailesii ». Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for bioteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-14143.

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The metabolic insertion of titanium into the biosilica frustules of the pennate diatom Pinnularia sp. and the centric diatom Coscinodiscus wailesii was explored in the present study. A total of five titanium incorporation experiments were conducted on Pinnularia, in addition to five control experiments. Titanium dissolved in HCl was co-delivered with silicate dissolved in NaOH to silicate replete and silicate deplete Pinnularia cultures over a 10 hour delivery period. Cell number, silicate and titanium concentration, Quantum Yield, Instantaneous Chlorophyll Fluorescence and pH was measured regularly throughout the experiments. The diatoms were left to consume the delivered silicate/titanium for 62 hours after delivery was completed before they were harvested and rinsed to remove the organic material. The resulting biosilica frustules were analyzed with (Scanning) Transmission Electron Microscopy to investigate the frustule structure, Inductively Coupled Plasma Mass Spectrometry to measure the elemental composition of the frustules and Energy Dispersive Spectroscopy to determine the location of the elements in the frustules. Quantum Yield measurements were conducted to obtain information about the Pinnularia photo system condition, and high Quantum Yield values were interpreted as an indication of a good overall physiological state of the cell. It was found that a combination of high Quantum Yield values and silicate depleted cultures produced the highest titanium content in the Pinnularia frustules (1.3 wt% relative to silicon). Furthermore, EDS analysis revealed that titanium was not evenly distributed throughout the biosilica frustule. The relative titanium content in the Pinnularia frustules was higher in the biosilica at the base of the large pores covering the frustule surface than in the biosilica between the pores. This was in accordance with findings reported in literature. The observed inhomogeneous distribution trend was found to apply also to phosphorous and iron present in the titanium-doped frustules. This observation has not been previously reported.Cell aggregation of the Pinnularia cultures was observed upon silicate/titanium addition. Based on results from control experiments there was reason to believe that the aggregation was triggered by titanium, but the explanation for this cellular response as well as its effect on titanium uptake and incorporation was not determined. Three titanium incorporation experiments were conducted in the proof on concept study on Coscinodiscus . Titanium dissolved in HCl and silicate dissolved in NaOH was co-delivered with a pipette once a day for three, five and seven days. On the day following the final addition, the diatoms were harvested and rinsed before they were analyzed in the same manner as Pinnularia. The experiments on Coscinodiscus revealed that metabolic insertion of titanium into the frustule biosilica was possible, but due to the small maximal titanium content achieved (0.03 wt% relative to silicon) and the slow growth rate, Coscinodiscus was not considered an optimal choice of diatom species for titanium incorporation purposes.It was not possible to rule out whether the frustule structure in any of the two species had been altered or impaired as a consequence of titanium exposure. Structural flaws were observed in frustules with and without titanium incorporated. A faint irregular pattern on the nanoscale was observed in Pinnularia frustules containing titanium. No such pattern was observed in titanium free frustules.The amount of boron measured in the frustule biosilica was higher than the regular dopant concentration in boron-doped silicon. The boron content in Pinnularia was found to be on average 0.1 wt% or 0.28 atomic % relative to Si, while the average in Coscinodiscus was nearly twice as high. Without further manipulation, this high boron natural boron concentration makes diatom frustules unusable for doped semiconductor purposes.Future work should involve reproduction of the obtained results with more replicates, as well as larger culture volumes and, in the case of Coscinodiscus in particular, longer time scale. Titanium uptake and incorporation studies should if possible be performed on single Coscinodiscus cells. Multiple continuous silicate starvation and titanium/silicate delivery cycles should be tested to determine if it is possible to incorporate titanium into a larger fraction of the culture population, as well as to increase the maximum amount of titanium incorporated into one frustule.Aggregation of Pinnularia diatoms should be further investigated to determine reason for the observed reaction, the effects on titanium uptake/incorporation and possible strategies to prevent it from occurring. Pinnularia frustules unexposed to titanium should be inspected in order to determine if the iron and phosphorous distribution pattern observed in the titanium-doped frustules is present in titanium-free frustules as well.A completely artificial culture medium and plastic cultivation containers should be applied to explore how the boron content of diatom frustules can be tailored by controlled delivery of boron to the culture medium.

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LINHARES, HORACIO M. da S. M. D. « Síntese de nanocristais de KYsub(3)Fsub(10) pelo método de co-precipitação visando aplicações ópticas ». reponame:Repositório Institucional do IPEN, 2014. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10622.

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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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James, Derak. « New approaches to chalcogenide materials for thermoelectrics| Lead telluride-based nanostructures and facile synthesis of tetrahedrite and doped derivatives ». Thesis, Wayne State University, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3735125.

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The overall purpose of this work is to address several of the roadblocks to use of thermoelectric materials for generation of electricity, namely inefficient processing of materials and low performance, commonly rated by the figure of merit, ZT=T?2?/?tot. The ZT includes ? as the Seebeck coefficient, ? as electrical resistivity, T as the average temperature, and ?tot as total thermal conductivity. ?tot is the sum of electronic charge carrier (?C) and lattice (?L) contributions to thermal conductivity. Attempts to increase ZT in the literature to values >1 have focused on decreasing the thermal conductivity via nanostructuring or optimizing the electrical conductivity and Seebeck coefficient by doping. In this work, two separate approaches are taken to tackle these issues: (1) Target higher ZT by assembling lead telluride (PbTe) nanoparticles from a multi-gram synthesis utilizing ligand stripping techniques or deliberately including discrete lead sulfide (PbS) NCs. (2) Develop a rapid, convenient synthesis of tetrahedrite (Cu12Sb4S13). Approach (1): Nanostructuring of PbTe and PbTe?PbS. Nanostructured PbTe and nanocomposites of PbTe?PbS are hypothesized to increase ZT by lowering thermal conductivity, while ligand stripping of PbTe NCs by sulfide or iodide is expected to increase ZT because it has been demonstrated to increase electrical conductivity in thin films of PbS. A new synthesis is in demand because mixing PbTe and PbS NCs requires that the PbTe be dispersible, and literature syntheses of such NCs suffer from small yields (<200 mg). Thus, applications of dispersible PbTe NCs are largely limited to thin films. The ZT values of these thin films are not reported due to difficulty in quantifying thermal conductivity. In the dissertation research, nanostructured PbTe pellets are prepared by hot-pressing PbTe NCs after either mixing with PbS NCs by incipient wetness, or ligand stripping with sulfide salt, iodide salt, or both. The PbTe NCs themselves are prepared in multi-gram quantities by hot-injection methods in solution. The NCs are characterized for crystallinity by powder X-ray Diffraction (XRD). The size and morphology of the NCs are probed via Transmission Electron Microscopy (TEM), and their composition is determined by Energy Dispersive Spectroscopy (EDS). The thermoelectric properties are studied on hot-pressed pellets of each sample. Approach (2): Developing a facile route to tetrahedrite and doped derivatives. Tetrahedrite is exciting the thermoelectric community due to its lack of rare or toxic elements, the tunability of its electronic properties by doping, the ability to dope by ball-milling with the plentiful natural mineral, and the ability to achieve a ZT of unity. However, the natural mineral is unsuitable on its own due to an excess of natural dopant, and reported tetrahedrite syntheses require heating at high temperature 650 ?C in a three day process followed by two weeks of heating at 450 ?C. This work establishes a new synthesis amenable to industrial production that reduces the heating time from over 2 weeks to 2 days for simultaneous batch production at moderate temperature (155 ?C for one day and 430 ?C for 30 min, cooling naturally). The tetrahedrite powder is prepared from chloride-free metal salts and thiourea by solvothermal methods and characterized by XRD for crystallinity. The composition is determined by Inductively Coupled Plasma analysis. Products from multiple batches are mixed by ball-milling alone or combined with the natural mineral as a means to dope with Zn2+ as a solid solution. The resulting powder is then hot-pressed to pellet form for thermoelectric characterization. The tetrahedrite is also doped in-situ by zinc over a range of 0.79 to 1.40 mol equivalents using chloride-free metal salts.

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Slostowski, Cédric. « Synthèse solvothermale supercritique de nanostructures d'oxyde de cérium ». Phd thesis, Université Sciences et Technologies - Bordeaux I, 2012. http://tel.archives-ouvertes.fr/tel-00954292.

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La synthèse contrôlée de nanoparticules constitue toujours un enjeu majeur en science des matériaux (pour des applications telles que la catalyse par exemple) et la voie "fluides supercritiques" permet de répondre en partie à ce challenge. Dans ce contexte, ce travail de thèse a été consacré à l'élaboration de nanostructures d'oxyde de cérium aux caractéristiques contrôlées (tailles, morphologies, propriétés de surface,...) par synthèse solvothermale supercritique. A partir de l'étude de l'influence des paramètres opératoires du procédé sur les caractéristiques physico-chimiques des nanomatériaux obtenus, des mécanismes de formation et de fonctionnalisation de surface ont été proposés. D'un point de vue applicatif, ces poudres ont été caractérisées qualitativement et quantitativement vis-à-vis de la capture réversible du CO2.

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SALUM, DEBORA C. « Marcadores à base de terras raras para detecção de estrogênios sinalizadores em fluídos biológicos ». reponame:Repositório Institucional do IPEN, 2014. http://repositorio.ipen.br:8080/xmlui/handle/123456789/23652.

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Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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22

Zhang, Xinyu, Li An, Jie Yin, Pinxian Xi, Zhiping Zheng et Yaping Du. « Effective Construction of High-quality Iron Oxy-hydroxides and Co-doped Iron Oxy-hydroxides Nanostructures : Towards the Promising Oxygen Evolution Reaction Application ». NATURE PUBLISHING GROUP, 2017. http://hdl.handle.net/10150/623197.

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Rational design of high efficient and low cost electrocatalysts for oxygen evolution reaction (OER) plays an important role in water splitting. Herein, a general gelatin-assisted wet chemistry method is employed to fabricate well-defined iron oxy-hydroxides and transitional metal doped iron oxyhydroxides nanomaterials, which show good catalytic performances for OER. Specifically, the Co-doped iron oxy-hydroxides (Co0.54Fe0.46OOH) show the excellent electrocatalytic performance for OER with an onset potential of 1.52 V, tafel slope of 47 mV/dec and outstanding stability. The ultrahigh oxygen evolution activity and strong durability, with superior performance in comparison to the pure iron oxyhydroxide (FeOOH) catalysts, originate from the branch structure of Co0.54Fe0.46OOH on its surface so as to provide many active edge sites, enhanced mass/ charge transport capability, easy release oxygen gas bubbles, and strong structural stability, which are advantageous for OER. Meanwhile, Co-doping in FeOOH nanostructures constitutes a desirable four-electron pathway for reversible oxygen evolution and reduction, which is potentially useful for rechargeable metal-air batteries, regenerative fuel cells, and other important clean energy devices. This work may provide a new insight into constructing the promising water oxidation catalysts for practical clean energy application.

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Matter, Paul H. « Electrocatalytic and fuel processing studies for portable fuel cells ». Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1149037376.

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Intronati, Guido Alfredo. « Relaxation de spin dans les semi-conducteurs dopés et dans les nanostructures à base de semi-conducteurs ». Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-01067064.

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Dans cette thèse nous considérons un semi-conducteur de GaAs dopé, où nous étudions la relaxation du spin du côté métallique de la transition metal-isolant. Nous considérons deux types différents d'interaction de spin-orbite. Le premier d'entre eux est associé aux impuretés et l'autre est de type Dresselhaus. La dynamique du spin est traitée à travers une formulation analytique basée sur la diffusion du spin de l'électron, et un calcul numérique de la durée de vie du spin.Ensuite, nous considérons une boîte quantique hébergée dans un nanofil de matériau InAs (avec une structure cristalline de type wurtzite), afin d'étudier l'effet de l'interaction spin-orbite sur les états propres du système. Nous développons ici une solution analytique pour la boîte quantique en incluant l'interaction spin-orbite (de type Dresselhaus propre à la structure wurtzite). Nous avons calculé le facteur g effectif, ainsi que la relaxation du spin dûe aux phonons acoustiques, en utilisant les potentiels d'interaction electron-phonon propres à la structure wurtzite.

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HUET, SARAH D. P. « Estudo de interações hiperfinas em nanopartículas de Fesub(3)Osub(4) e Fesub(3)Osub(4) dopadas com gadolínio pela espectroscopia de correlação angular perturbada ». reponame:Repositório Institucional do IPEN, 2014. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10616.

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IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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Vargas, Hernandez Jesus. « Structural and Morphological modification of TiO2 doped metal ions and investigation of photo-induced charge transfer processes ». Thesis, Le Mans, 2017. http://www.theses.fr/2017LEMA1018/document.

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Le travail de thèse porte sur les méthodes de synthèse de nanostructures de dioxyde de titane et de leurs études physicochimiques afin de préciser les corrélations entre la morphologie, le dopage métallique, les caractéristiques structurales avec l'efficacité photocatalytique. Le grand intérêt pour les nanomatériaux TiO2 réside dans la mise au point de nouvelles sources d'énergie ou la conservation de l’environnement par des processus photocatalytiques. Cependant, la limitation principale de TiO2 est du au large gap électronique (eV ~3,2) du polymorphe Anatase. Ainsi, un des objectifs importants pour l'amélioration de l’efficacité des nanomatériaux TiO2 est d'augmenter leur photoactivité en décalantla création de paires d'électron-trou de l’UV à la gamme du visible. D'ailleurs, on a montré que l'utilisation de nanostructures 1D de TiO2 (nanotubes) a amélioré la collection de charges, en favorisant leur transport dans les structures 1D, qui par conséquent réduit au minimum la recombinaison et prolonge les durées de vie des électrons.La première partie de ce travail est dédiée à la synthèse des nanopoudres TiO2 dopées par des ions métalliques (Ag, Cu, Eu) préparés par sol-gel. Même avec différents éléments de dopage qui apparemment peuvent adopter le même état de valence (2+) (Cu2+, Ag2+, Eu2+), différents comportements ont été démontrés pour l'incorporation efficace de ces ions dans la structure de TiO2. L'anomalie entre les rayons ioniques des différents éléments utilisés module le rapport du dopage substitutionnel. Ceci est en effet réalisé pour Cu2+ mais dans moins d'ampleur pour Ag2+ tandis que les ions d'europium forment une ségrégation de phase Eu2Ti2O7. La dégradation de colorants de bleu de méthylène (MB) a étéaméliorée légèrement avec les échantillons dopés Ag. La raison a été attribuée aux clusters métalliques Ag qui ont été en effet mis en évidence à travers leur bande d’absorption plasmonique. La deuxième partie porte sur des couches minces de TiO2 dopés (Cu, Ag, et Eu) qui ont été élaborés par sol-gel et spin-coating et dipcoating. Les paramètres optimaux ont été obtenus pour réaliser les films cristallins mais présentant une organisation mésoporeuse qui dépend également du processus de dopage. Des études de Photocatalyse ont été également réalisées et l'efficacité des films ont été comparées en fonction des éléments dopants. La troisième partie de la thèse est liée à la modification morphologique des nanoparticules pour former des nanotubes à l'aide de la méthode hydrothermale sous pression contrôlée. Un plan d'expérience basé sur la méthode Taguchi a été utilisé pour la détermination des paramètres optimaux.Les nanotubes TiO2 augmentent la surface spécifique en comparaison avec les nanoparticules. La dégradation de bleu deméthylène par les nanotubes a montré une efficacité photocatalytique plus élevée qu’avec les nanopoudres TiO2 pures etdopés Ag
The thesis work is focused on the synthesis methods of titanium dioxide nanostructures and their physico-chemical studies in order to point out the correlations between the morphology, metal doping, structural features with the photocatalytic efficiency. The great interest on TiO2 nanomaterials deals with new sources of energy or in the environment preservation through the photocatalytic properties. However, the main limitations is due to the wide band gap (~3.2 eV) of the anatase polymorph. Thus, a major objective for improvement of the performance of TiO2 nanomaterials is to increase theirphotoactivity by shifting the onset of the electron-hole pairs creation from UV to the visible range. Moreover, it was found that using onedimensional (1-D) TiO2 (nanotubes) improved the charge collection by 1D nanostructures which consequently minimizes the recombination and prolongate the electron lifetimes. The first part of this work is focused on the synthesis of TiO2 nanopowders doped with metallic ions (Ag, Cu, Eu) prepared by Solgel. Even with different doping elements which apparently can adopt the same valence state (2+) such as (Cu2+, Ag2+,Eu2+), different behaviors were demonstrated for the effective incorporation of these ions in the host structure of TiO2. The discrepancy between ionic radii of the different used elements modulates the ratio of the substitutional doping. This is indeed achieved for Cu2+ but in less extent for Ag2+ while Europium ions form segregated phase as Eu2Ti2O7. The experiments on the degradation of methylene blue (MB)dyes have shown slight improvement with Ag-doped samples. The reason was tentatively attributed to the Ag clusters which were indeed demonstrated through their plasmon optical band. The second part of the work concerns thin films of TiO2 doped (Cu, Ag, and Eu) which were elaborated by spin coating and dip coating. The optimal parameters were obtained to achieve crystalline films but presenting mesoporous organisation which also depends on the doping process. Photocatalysis investigations were also realized and the efficiency of the films compared as function of the doping elements.The third part of the thesis is related to the morphological modification from nanoparticles to nanotubes by using the hydrothermal method with controlled pressure. An experimental design based on Taguchi Method was employed for the determination of the optimal parameters. TiO2 nanotubes increase the surface area in comparison with TiO2nanoparticles. TiO2 nanotubes were tested for the methylene blue degradation and show a higher photocatalytic efficiency than TiO2 nanopowders and TIO2 doped with Ag

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PAGANINI, PAULA P. « Síntese e caracterização de nanopartículas de óxido misto de estanho/titânio dopadas com lantanídeos para marcação biológica ». reponame:Repositório Institucional do IPEN, 2012. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10182.

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Made available in DSpace on 2014-10-09T12:35:42Z (GMT). No. of bitstreams: 0
Made available in DSpace on 2014-10-09T14:03:56Z (GMT). No. of bitstreams: 0
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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Huang, Yi. « Local Infrared Spectroscopy of Highly Doped Semiconductors Structures Based on Scattering-type Nanoscopy and Photoinduced Force Microscopy ». Thesis, Troyes, 2018. http://www.theses.fr/2018TROY0027.

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Dans cette thèse, les propriétés plasmoniques de nanostructures d’InAsSb fortement dopées (HDSC : Highly doped Semiconductor) sont étudiées par nanoscopie de champ proche dans l’infrarouge moyen. Après une introduction sur les matériaux plasmoniques dans l’infrarouge, nous présentons les outils de caractérisation associés. Ici, deux types d'échantillons sont étudiés, des réseaux 1D et des réseaux 2D d’HDSC. Ces échantillons sont caractérisés par microscopie de champ proche optique à sonde diffusante (s-SNOM) et par une technique plus récente de microscopie à force photoinduite (PiFM). Les aspects fondamentaux et instrumentaux de ces deux approches nanoscopiques sont présentés. Pour les réseaux HDSC, les deux techniques de nano-imagerie spectroscopiques sont mises en œuvre au voisinage de la fréquence plasma, où la fonction diélectrique avoisine zéro (ENZ : Epsilon-Near-Zero material). Les réponses obtenues par ces deux techniques sont alors comparées et discutées. Pour les réseaux bidimensionnels, l'analyse est réalisée par la microscopie à sonde diffusante, sensible à la phase, qui révèle l’existence d’un mode d’arête extrêmement confiné, comme prédit par les simulations électromagnétiques
In this thesis, highly doped semiconductor (HDSC) InAsSb nanostructures have been investigated by near-field nanoscopy in the mid-infrared range. First, infrared plasmonic materials are introduced as well as well as the characterization tools used in this thesis. Herein, two types of nanostructured HDSC samples are studied: HDSC 1D gratings and HDSC 2D array. To characterize the HDSC samples, both phase-sensitive scattering type nanoscopy (s-SNOM) and the more recent Photoinduced Force Microscopy (PiFM) are used. The fundamental aspects of these two microscopies are presented and detailed instrumental information is provided. For HDSC 1D gratings, both techniques are used for spectroscopic nano-imaging in the vicinity of the plasma frequency, where the material behaves as an epsilon-near-zero (ENZ) material. The two responses are compared and discussed in terms of model. For HDSC 2D array, the investigation is carried out by s-SNOM. Both localized plasmonic resonance and ENZ properties are observed and compared with analytical simulations. The signature of a highly localized surface plasmon resonance confined on the edge mode is observed in the experimental images, in agreement with electromagnetic simulations

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Weatherspoon, Michael Raymond. « Conformal sol-gel coatings on three-dimensional nanostructured templates ». Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/28157.

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Thesis (M. S.)--Materials Science and Engineering, Georgia Institute of Technology, 2008.
Committee Chair: Sandhage, Kenneth; Committee Member: Barefield, Kent; Committee Member: Bunz, Uwe; Committee Member: Carter, Brent; Committee Member: Tannenbaum, Rina.

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Dotsenko, V. P., I. V. Berezovskaya, N. I. Poletaev, Yu A. Doroshenko, B. I. Zadneprovski, N. P. Efryushina et E. V. Zubar. « Synthesis of Ce3+ -doped Terbium Aluminum Garnet Phosphors from Nanostructured Oxides ». Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/34810.

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The paper describes the synthesis of Ce3+ -doped terbium aluminum garnet (TAG) phosphors with the use of nanostructured oxides of aluminum and rare earths. Aluminum oxide nanoparticles were obtained by gaseous-disperse synthesis and characterized by X-ray diffraction, differential thermal analysis and scanning electron microscopy. The preparation of cerium-doped terbium oxide nanopowders and luminescent properties of the Тb3(1-x)Ce3xAl5O12 phosphors are also discussed. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34810

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Müller, Vesna. « Mesoporous transparent conducting films of antimony doped tin oxide as nanostructured electrodes ». Diss., Ludwig-Maximilians-Universität München, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-158995.

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Katembo, Kainda Jr. « Preparation of nitrogen doped nanostructured TiO2 and ITS applications to photocatalytic disinfection ». DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2010. http://digitalcommons.auctr.edu/dissertations/2416.

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Benhaliliba, M., C. E. Benouis et Y. S. Ocak. « Nanostructured Al doped Sn02 films grown onto ITO substrate via spray pyrolysis route ». Thesis, Видавництво СумДУ, 2011. http://essuir.sumdu.edu.ua/handle/123456789/20530.

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We report on nanostructured films of Al doped tin oxide grown by facile spray pyrolysis route, and their physical properties are investigated. The sprayed films are grown onto ITO substrate at 300°C from (SnCl4, 5H2O)as precursor. The content of Al is kept at 3 % in the solution. Structural, optical, electrical and surface properties are investigated. X-rays pattern reveals polycrystalline structure and SnO2 phase occurence. The visible transmitance exceeds 85%, the band gap is 3.7 eV.Nanotips are observed by 3D atomic force microscope (AFM) picture. The films exhibits very low resistivity found to be 9.85 10-5􀂟.cm, a high electron concentration around 1021cm-3, and low mobility 20 cm2/Vs. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/20530

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Cripps, Chala Ann. « Synthesis and characterization of cobalt ferrite spinel nanoparticles doped with erbium ». Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/30855.

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Biswas, Sutapa. « Magnetism and Associated Exchange Bias Effects in Mn2Ni1+xGa1-x Heusler Alloys and Selected Fe Doped Derivatives ». Miami University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=miami1596051931485739.

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Gautier, Pierrick. « Electrodépôt de ZnO nanostructuré sur électrodes de diamant dopé bore ». Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLV141/document.

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Le dépôt de ZnO sur diamant est actuellement assuré par des méthodes physiques (ALD, sputtering, CVD) coûteuses et complexes à mettre en oeuvre. La réalisation de ces dépôts de ZnO peut également être effectuée via des procédés plus doux tels que le procédé électrochimique qui représente une alternative intéressante car peu coûteux, et facile à mettre en oeuvre. L’électrodépôt de ZnO a été très largement étudié sur divers substrats, notamment pour des applications dans le domaine du photovoltaïque. Toutefois, seule une étude a été réalisée concernant l’électrodépôt de ZnO sur diamant alors que de nombreuses applications découlent de telles structures : dispositifs à ondes acoustiques de surface (SAW), photo-détecteurs UV ou bien biocapteurs. L’objectif de la thèse réside ainsi dans l’étude de l’électrodépôt de ZnO sur substrat diamant dopé bore en se basant sur le procédé mis en évidence par le groupe de Lincot dans les années 1990. Cette technique consiste à réduire, en présence d’ions Zn2+, l’oxygène dissous pour former des hydroxydes et a fortiori ZnO par réaction des hydroxydes et des ions Zn2+.Le diamant étant un substrat complexe en raison notamment de son grand gap (5,4 eV), un important dopage est nécessaire pour pouvoir l’étudier dans le domaine de l’électrochimie. Dans un premier temps, les conditions d’électrodépôt de ZnO sur diamant (température, potentiel électrique) ont été déterminées avant d’envisager l’étude de l’influence de divers paramètres expérimentaux. Par la suite, l’influence de la composition du bain a été étudiée puisque les concentrations et la nature des précurseurs de zinc et de l’électrolyte support ont été étudiées, permettant de former toute une variété de structures de ZnO sur diamant. Enfin, la dernière partie de la thèse s’est focalisé sur l’influence de la chimie de surface du diamant sur la morphologie, la structure et l’adhérence des dépôts de ZnO formés. L’état de surface initialement hydrogéné du diamant a été modifié en utilisant des traitements électrochimiques conduisant à la formation de groupements oxydés
Currently, ZnO deposition on diamond is obtained by physicals methods (ALD, sputtering, CVD) which are expensive and difficult to implement. The realization of these ZnO deposits can also be made by softer methods such as electrodeposition which represents an interesting alternative because of its low cost. ZnO electrodeposition has been already studied on several substrates especially for photovoltaic devices. However, only one study has been realized concerning ZnO electrodeposition on diamond while many applications derived from these structures: surface acoustic wave sensors, UV photodetectors, and biosensors. The aim of this work is the study of ZnO electrodeposition on boron doped diamond by following the process highlighted by Lincot et al in 1990s. This process is based on the oxygen reduction reaction leading to the formation of hydroxides which react with Zn2+ cations to form ZnO. Diamond is a complex substrate which presents a large gap of 5.4 eV requiring an important doping to allow its use in electrochemistry. At first, ZnO electrodeposition conditions (temperature, electrical potential) have been determined. The influence of deposition bath has then been studied by varying nature and concentrations on zinc precursor and electrolyte support. Results indicate the possibility to obtain different ZnO/diamond structures by varying theses parameters. Finally, the influence of the surface termination of diamond on ZnO structures, shape and adherence has been investigated by modifying the H-terminated surface on O-terminated surface by using electrochemical treatments

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Yeoh, Wai Kong. « Processing and characterisation of nano carbon doped MgB2 in form of wire and bulk ». Access electronically, 2006. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20061121.122622/index.html.

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Huang, Xuezhen. « Fabrication and optical properties of (I) erbium-doped nanowires containing germanium and/or zinc oxide and (II) porous germanium nanowires ». [Fort Worth, Tex.] : Texas Christian University, 2010. http://etd.tcu.edu/etdfiles/available/etd-04282010-134727/unrestricted/Huang.pdf.

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Булавінець, Тетяна Олександрівна. « Фотодинамічні властивості наноструктур в умовах плазмонного резонансу для біомедичних застосувань ». Diss., Національний університет "Львівська політехніка", 2020. https://ena.lpnu.ua/handle/ntb/56113.

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Ren, Dawei. « Anti-adhesive Si-and F-doped DLC coatings and micro-nanostructured surfaces for medical implants ». Thesis, University of Dundee, 2015. https://discovery.dundee.ac.uk/en/studentTheses/859a4e15-0770-431e-8853-ccade9a67b6c.

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The development of biomaterials mainly focuses on the improvement of their biocompatibility. The aim of this research was to develop a range of DLC coatings and micro-nanostructured surfaces with anti-bacterial properties for biomedical applications. In this study a DLC coating and Si- and F- doped DLC coatings with various Si and F contents were prepared by a radio frequency plasma-enhanced chemical vapor deposition (rf-PECVD) technology. Under water contact angle method was used to characterize the surface properties of these DLC type coatings, and bacterial adhesion assess were performed by fluorescence microscopy to evaluate their anti-bacterial ability. The results showed that the DLC coatings can effectively decrease the bacterial adhesion, which reduced the bacterial adhesion by 65%, compared with uncoated stainless steel. The extended DLVO theory was used to explain the bacterial adhesion mechanism. Quartz Crystal Microbalance technology (QCM-D), which is a simple, efficient, reliable, real time and information-rich method for measuring bacterial adhesion and related assesses, was used to measure and record the bacterial adhesion process with time. The frequency change curves and dissipation factor change curves of bacterial adhesion onto the coatings were obtained. The electrochemical corrosion tests showed that the doped DLC coatings has excellent anti-corrosion properties and can protect stainless steel from corrosion. In this study the effects of material topography on bacterial adhesion were investigated both theoretically and experimentally. The interaction energies between bacteria (E.coli) and micro-nanostructure were computed by extended DLVO theory. The results showed that 350nm scale surface structure has the highest interaction energy and should be able to minimize the bacterial adhesion. To verify this finding, a series of surface micro/nano-structures (350-1000nm) were produced on PDMS samples by a soft lithography method. The bacterial adhesion assays were performed with the micro/nano-structured PDMS surfaces. The bacterial adhesion results were consistent with our theoretical prediction. In addition the sterile urine encrustation experiments were also performed with the micro/nano-structured PDMS surfaces. The experimental showed that the micro-nano-structured surfaces significantly reduced or delay the urine encrustation formation on the surfaces.

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Vilasi, Pauline. « Synthèse de nouveaux catalyseurs nanostructurés par dépôts physiques à base de pérovskite de lanthane ». Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCA041.

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Ce travail de thèse est issu d’une collaboration entre les laboratoires de recherche FEMTO-ST de l’université technologique de Belfort-Montbéliard et IRCELYON de l’université Claude Bernard à Villeurbanne. Les objectifs de cette étude portent sur la faisabilité d’élaborer par pulvérisation cathodique magnétron des films minces de cobaltite de lanthane nanostructurés. En effet, ces films présentent des propriétés catalytiques intéressantes pour l’oxydation des composés organiques volatiles comme le propène (C3H6) ou le monoxyde de carbone (CO) qui constituent la principale source de pollution de l’air. Il sera montré dans un premier temps que les cobaltites de lanthane de formule LaCoO3 ne sont pas efficaces pour ce type d’application. La composition chimique de ce matériau sera donc modifiée en y incorporant de l’argent de manière à faire varier les propriétés physico-chimiques des films et d’augmenter leurs performances catalytiques. La morphologie des films est directement impactée par l’introduction de Ag puisqu’elle évolue d’un système dense à un système « nanofilaire ». Une autre série de dépôts sera également élaborée et testée en catalyse constituée de cobaltites de lanthane dopées avec de l’argent mais aussi du cérium. On retiendra alors que les films de LaCoO3 + Ag sont plutôt efficaces et prometteurs puisqu’ils présentent des performances catalytiques se rapprochant de celles du platine (catalyseur de référence). Néanmoins, bien que les films aient toujours cette morphologie nanofilaire, les compositions chimiques des films élaborés à base de LaCoO3 + Ag + Ce doivent être optimisées afin d’augmenter leurs activités catalytiques
This work was made in the frame of a scientific research relationships between the laboratory FEMTO-ST of the Technological University of Belfort-Montbéliard and the laboratory IRCELYON of the Claude Bernard University of Villeurbanne. This study aims at characterizing the feasibility of nanostructured lanthanum cobaltite thin films via magnetron sputtering. Indeed, it is well known these materials have interesting catalytic properties regarding the oxidation of volatile organic compounds such as propene (C3H6) or carbon monoxide (CO), the latter being the main source of air pollution. First, it has been shown that lanthanum cobaltites of formula LaCoO3 are not efficient for this type of application. The chemical composition of this material was then modified by incorporating silver so as to vary the physicochemical properties of the films and increase their catalytic performance. In consequence, the morphology of the films was directly impacted by the introduction of Ag since it evolved from a dense system to a "nanowire" system. Another series of deposits based on cobaltite modified by both silver and cerium additions have been also developed and tested during catalytic tests. It should be noted that the Ag containing thin films of LaCoO3 are rather efficient and then promising since they have catalytic performances close to those of platinum (the reference catalyst). Concerning the Ag and Ce containing perovskite films, although they still have this peculiar nanowired morphology, their chemical compositions have to be optimized in order to increase their catalytic activities

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Nxumalo, Edward Ndumiso. « Synthesis of nitrogen doped carbon nanotubes using ferrocenes ». Thesis, 2011. http://hdl.handle.net/10539/10541.

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Ph. D., Faculty of Science, University of the Witwatersrand, 2011
Nitrogen doped carbon nanotubes (N-CNTs) have become a topic of increased importance in the study of carbonaceous materials. This arises from the physical and chemical properties that are created when N is embedded into a CNT. These properties include modified chemical reactivity, modified conductivity and changed mechanical, electronic and magnetic properties. This thesis covers the analysis of the catalytic growth of N-CNTs under well defined conditions and the optimization of reaction conditions to produce N-CNTs. Herein, a range of methodologies have been devised to synthesize N-CNTs. One of the procedures used in this work uses a floating catalyst in which an organometallic complex is decomposed in the gas phase in the presence of a nitrogen containing reactant to give the N-CNTs. This thesis focuses on the use of ferrocene and ring substituted ferrocenes in the formation of N-CNTs and other shaped carbon nanostructures. It talks of the effects that physical parameters such as temperature, pressure, gas flow rates and the type and concentration of N source have on the N-CNT type, size and yields as well as the nitrogen content incorporated into the tubes that are produced using the organometallic complexes. Proposed growth models for N-CNT synthesis are also reported. This work reveals that the N-CNTs produced are less stable (thermal gravimetric analysis measurements), less graphitic and more disordered (transmission electron microscope measurements) than their undoped counterparts. The ratio of the Raman D- and G-band intensities increase with the nitrogen concentration used during the CNT growth. Furthermore, the transmission electron microscopy (TEM) studies reveal that the CNTs are multi-walled, and that the diameters of the N-CNTs can be controlled by systematically varying the concentrations of the nitrogen source. Furthermore, X-ray photoelectron spectroscopy (XPS) and CHN analysis demonstrate that substitutional N is indeed present in the CNTs mainly as pyridinic and pyrrolic xiii N (and is sp2 and sp3 coordinated). The TEM analysis also revealed that when ferrocenylaniline and ferrocene/aniline reactions are compared at similar Fe/N molar ratios, higher N doping levels are achieved when ferrocenylaniline is the catalyst. Investigations of surface and interior imaging of N-CNTs was carried out by high resolution TEM (HRTEM) and identification of N-rich regions were performed by Energy filtered TEM (EFTEM). We also investigated the solid state pyrolysis of ferrocenylmethylimidazole or a mixture of ferrocene (FcH)/methylimidazole at 800 oC at different ratios in sealed quartz tubes. TEM studies showed bamboo compartments are present in the CNTs. An investigation of the bamboo structures revealed that three methylimidazole structural isomers led to tubes with different individual bamboo compartment distances and different morphologies including different N contents. It was observed that when diverse N containing hydrocarbons were used the amount of N in the nitrogen containing reagent is more important than the source and type of the N atoms used as revealed by trends in the morphology of the N-CNTs produced. We have also studied the effect of arylferrocene ring substituents on the synthesis of CNTs and other shaped carbon nanomaterials in subsequent chapters. Magnetic properties of different N doped carbon structures produced in the earlier chapters were investigated using electron spin resonance (ESR) spectroscopy. Most importantly, we observed a large g-factor shift in samples of N-CNTs from that of the free electron. Further, the shift is temperature dependant. A facile method for attaching Au nanoparticles to the surface of pristine N-CNTs and functionalized N-CNTs has been developed. The Au nanoparticles incorporated in the N-CNTs have a wide range of diameters (10 – 35 nm) and possess different shapes. The method offers certain advantages, such as providing Au nanoparticles in good yields and ease of use. The Au/N-CNT nanohydrids are being employed in catalytic reactions e.g. the oxidation of styrene.

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Ghadimi, Nafise. « CVD synthesis of nitrogen doped carbon nanotubes using iron pentacarbonyl as catalyst ». Thesis, 2012. http://hdl.handle.net/10539/11348.

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M.Sc., Faculty of Science, University of the Witwatersrand, 2011
In this dissertation, the synthesis of nitrogen doped carbon nanotubes (N-CNTs) was performed successfully, using a floating catalyst chemical vapour deposition (CVD) method. Fe(CO)5 was utilized as the catalyst and acetonitrile and toluene as nitrogen and carbon sources respectively. Two different procedures were used to add reagents to the reactor: an injection method and a bubbling method. The effect of nitrogen concentration and physical parameters such as reaction temperature, gas flow rate on the morphology, crystallinity and thermal stability of the tubes was studied. The synthesized materials were characterized by means of Raman spectroscopy, TGA and TEM analyses. The presence of nitrogen was confirmed by the presence of the bamboo formations in the tubes by TEM. A comparison of the data from the numerous reactions revealed that N-CNTs can be made from Fe(CO)5 and acetonitrile. Further the main conclusions achieved using the injection method were: i) the maximum number of tubes with bamboo structure were made using on acetonitrile concentration of 15%, ii) The best growth temperature to make N-CNTs was 850 oC, iii) An increase in acetonitrile concentration decreased the yield of NCNTs and iv) Tubes with the narrowest outer diameters were made using an acetonitrile concentration of 15%.

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Hong, Meng-Hsiang, et 洪孟祥. « Characterization and Applications of Doped CdS Nanostructures ». Thesis, 2015. http://ndltd.ncl.edu.tw/handle/hujh52.

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碩士
國立中正大學
光機電整合工程研究所
103
Gallium (Ga) -doped cadmium sulfide (CdS) nanowires (NWs) were successfully grown by chemical vapor deposition (CVD) method. We could not only improve the conductivity of the CdS NWs, but also control the electrical properties of CdS NWs by different doping amounts. X-ray photoelectron spectroscopy (XPS) analysis and photoluminescence (PL) analysis verified that gallium has been incorporated into CdS NWs with the atomic percentages of 1.59%, 2.45%, and 3.59 %, when 0.1 g, 0.2 g, and 0.3 g Ga were used as the doping source, respectively. We further investigated the carrier transport properties of the Ga-doped CdS NWs, the results showed that the conductivities of NWs increased with the Ga doping source. Furthermore, the mobilities of CdS nanodevice with different Ga doping levels were significantly distinctive. We used CdS NWs to fabricate the CdS/Cu2S core-shell n-p hetrostructure with photolithography and cation exchange technique. Finally, the photovoltaic properties of 0.1 g Ga-doped CdS/Cu2S core-shell n-p hetrostructure were examined under the AM 1.5 G solar simulator, the short-circuit current (Isc), open-circuit voltage (Voc), fill factor (FF), and power conversion efficiency (PCE) were determined to be 0.152 nA, 0.245V, 44.5%, and 0.4045%, respectively.

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Lin, Wei-Chen, et 林韋辰. « Growth and Characterization of Antimony Doped ZnO Nanostructures ». Thesis, 2015. http://ndltd.ncl.edu.tw/handle/8737rf.

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碩士
中國文化大學
化學工程與材料工程學系奈米材料碩士班
103
In this work, pure ZnO, Sb-doped ZnO nanostructures have been synthesized by thermal CVD. The morphology of nanostructures was analyzed by field emission scanning electron microscope (FESEM). It is shown that the appearance of nanostructures is nanowires with diameter ranging between 40 and 100 nm and with lengths extending up to several microns. High resolution transmission electron microscopy (HRTEM) micrographs and selection area electron diffraction (SAD) patterns of ZnO nanowires clearly show that they are single-crystalline with a growth direction of [0001]. The structure and component were characterizes by means of X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and Mircro-Raman Spectroscopy. The properties of ZnO and Sb-doped nanowires were investigated by photoluminescence (PL),and I-V curve. The pure ZnO nanowires gave UV emission from 382 nm but the emission of Sb-doped ZnO nanowires red shift to 389 nm.The resistance of the nanowires decreasing is the result of antimony doping.

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46

TSENG, CHIEN-YOA, et 曾建堯. « Preparation and Characterization of Ga-doped ZnO Nanostructures ». Thesis, 2018. http://ndltd.ncl.edu.tw/handle/7uuhke.

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碩士
逢甲大學
材料科學與工程學系
106
Ga-doped ZnO nanoneedle arrays have been successfully grown on the glass and silicon substrates with pre-coated ZnO seed film by a facile wet chemical method at the low reaction temperature. Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), UV-visible spectroscopy, and electronics measurement system have been used to characterize the grown Ga-doped ZnO nanostructures. The concentration of gallium nitrate plays a critical role in controlling the doping concentration and morphology of Ga-doped ZnO nanostructures. The appropriate Ag sputtering durations and Ga-doped ZnO nanoneedle arrays have been optimized to yield the greatest surface-enhanced Raman scattering effect in the rhodamine 6G molecule. The Ga-doped ZnO nanoneedle arrays with Ag-sputtering duration of 30 s shows a stronger enhancement and a lower detection limit (Rhodamine 6G 10-9 M and Amoxicillin 10-10 M).

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47

Fang, Chiung-Wan, et 方瓊菀. « Growth and characterization of aluminum、antimony doped ZnO nanostructures ». Thesis, 2009. http://ndltd.ncl.edu.tw/handle/34342371055085124579.

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博士
國立中興大學
應用數學系所
97
Thermal evaporation is often applied to synthesize the highly crystalline nanostructures. The method is simple and straightforward, enabling its integration with the doping process. Therefore, we will synthesize ZnO nanostructures using thermal evaporation. In this study, zinc oxide (ZnO) nanostructures such as nanowires, nanobelts and nanorods have been synthesized on silicon、Al2O3 and stainless steel substrates by thermal evaporation. The growth mechanism、structure、photoelectric properties and field emission of ZnO nanostructures were investigated. This growth mechanism was governed by vapor-solid (VS). ZnO nanostructures were successfully synthesized by thermal evaporation method at 650℃. X-ray diffraction (XRD) confirmed that ZnO nanostructures are single crystal wurtzite structure. Furthermore, ZnO-doped Al and ZnO-doped Sb nanostructures were synthesized by pre-depositing with an Al thin layer on substrates and Zn powder mixed Sb powder with Zn-Al has a eutectic, respectively. Properties of the ZnO nanostructures were investigated. We report a simple method whereby an Al film was pre-deposited on Si substrate by DC sputtering with Zn powder acting as the vapor source. ZnO:Al nanostructures were synthesized on silicon substrate at 650℃. High resolution transmission emission microscopy (HR-TEM) and XRD confirmed that ZnO:Al nanostructures are single crystal wurtzite structure and grown along [001] direction. It also confirmed good crystal property of ZnO:Al nanostructures. High angle annular dark field (HAADF)、Raman and energy dispersive X-ray spectroscopy (EDS) showed that the Al element was highly scattered and dispersed throughout the ZnO nanostructures. Therefore, by pre-deposited an Al layer on the substrate can help the metal Al dopant into the ZnO nanostructures. Synthesis of ZnO:Sb nanostructures used Zn powder mixed Sb powder with Zn-Al has a eutectic at binary phase. The single-crystalline of ZnO:Sb nanostructures were synthesized at 600℃ on stainless steel and Al2O3 substrates. ZnO:Sb singal nanostructures were grown along the [100] axis. The dimensions of the ZnO:Sb nanostructures are about 10-30 nm in diameter and up to several ten microns in length. Raman and EDS displayed that the metal Sb was dopant into the ZnO crystal through Zn-Sb alloy-evaporation deposition. Using UV photocurrent measurement, it also showed that light current to dark current ratio of ZnO:Sb nanostructures was about 48.8. Photoluminescence (PL) measurement showed a blue-shift emission peak was found in ZnO:Al nanostructures (382nm) in contrast to that of ZnO nanostructures (385nm). The same way revealed that the ZnO:Sb and ZnO nanostructures have a blue band emission at 376 nm and 378 nm, respectively. The result also showed that a blue-shift emission peak was found in ZnO:Sb compare to ZnO nanostructures. The field emission properties of ZnO:Al and ZnO:Sb compare to ZnO nanostructures were also investigated, respectively. The turn-on field of ZnO:Al and ZnO nanostructures on silicon substrate were found to be 3.8 and 5 V/μm, respectively; the current density was 1 μA/cm2. The thresholds field for ZnO:Al and ZnO nanostructures were estimated around 25 and 47 V/μm, respectively; the current density was 1 mA/cm2. About the measurement of ZnO:Sb and ZnO nanostructures on stainless steel substrate were found to be 3.85 and 15.5 V/μm, respectively, the current density was 1μA/cm2. The thresholds field for ZnO:Sb and ZnO nanostructures were estimated around 11.8 and 26.7 V/μm, respectively; the current density was 1mA/cm2. In this thesis, the influences of Al and Sb doped into the ZnO crystal were investigated by FE, UV, PL and gas sensor. In addition, the improvements of ZnO nanostructures on the structural were discussed. All the results indicated the quality of our ZnO nanostructures is good. A process which is simple and easy to scale-up has been employed to synthesize the ZnO:Al, ZnO:Sb and ZnO nanostructures. Accordingly it is a potentially useful process for fabricating FEDs devices.

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48

Su, Wei-Sung, et 蘇韋菘. « Cu doped ZnO nanostructures prepared by solid state diffusion ». Thesis, 2013. http://ndltd.ncl.edu.tw/handle/97575360838158832734.

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碩士
國立高雄大學
化學工程及材料工程學系碩士班
101
In this study, we prepared ZnO NRs (NRs) and NWs (NWs) by chemical vapor depositions (CVD) or hydrothermal method first, respectively, then coated Cu nanoshells with various thicknesses, and followed by annealing treatments with different atmosphere, duration, and pressure. We independently controlled Cu concentration and diameter of Cu doped ZnO (CZO) nanostructures by using the solid state diffusion methods and investigated the physical properties of CZO nanostructures. In the first part, we prepared CZO nanostructures (NSs) by CVD grown ZnO NWs and thermal diffusion of Cu. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show the bead-like Cu: ZnO NWs grow along the <0002> direction and the average diameter of neck and bead parts are 5 and 25 nm, respectively. When the diameters of ZnO NWs are smaller than 50 nm, the CZO nanostructures will become the periodic bead-like structures after the annealing treatment. High resolution TEM and XRD (X-ray diffraction) show the d-spacing of (0002) planes decreases and the diffraction peaks of (0002) plane shift to higher angle after the Cu diffusion. XPS (X-ray photoelectron spectrum) shows the main ions doped in ZnO is Cu2+, consistent with the data of XRD and TEM since radius of Cu2+ is smaller than Zn2+. PL (photoluminescence) and CL (cathodoluminescence) measurements show that CZO nanostructures exhibit strong and broad band visible light convoluted with purple, blue, green, and yellow emissions. Besudes, the near-edge emission red shifted after the annealing compared with undoped ZnO NWs. In the work, we propose a strain-assisted growth mechanism of the CZO periodic nanostructures. The prepared Cu doped ZnO NSs show strong and broad band visible emission, which are promising for optoelectronic applications. In the second part, we prepared ZnO NRs by hydrothermal routes, coated Cu nanoshells with various thicknesses, and followed by annealing treatments in different conditions. SEM images show there are many bulks generated on the surface of NRs, which increased with the thicknesses of Cu nanoshells. XRD patterns show the signal of CuO increase with pressure or thickness of Cu, but (0002) planes of ZnO are still the main diffraction peaks of the sample. Besides, the (0002) diffraction peaks of CZO NRs shift to lower angles and then finally recover with the increasing the Cu thickness, but that is still lower than angle of undoped ZnO NWs. Notably, this shift direction of (0002) diffraction peak is just opposite to those prepared by CVD grown ZnO NWs. XPS shows the main ions doped in ZnO is Cu+, consistent with the decrease of d-spacing, obtained from XRD and TEM. In addition, the diffraction peaks of CuO disappear in a pressure of 1.1 torr when annealing time increase from 4 to 12 hours, which exhibits the Cu ions can be completely doped in ZnO in suitable condition. CL measurements show the near band edge emission disappears after the doping of Cu, and the visible emission shifts from yellow to blue light. In this research, we synthesize CZO nanostructures by two different methods. The main dopants in CZO nanostructures prepared by CVD-ZnO/Cu diffusion and hydrothermal-ZnO/Cu diffusion processes are Cu2+ and Cu+, respectively. The different valences of Cu in ZnO are ascribed to distinct original intrinsic defects in the CVD-ZnO and hydrothermal-ZnO nanostructures. The valence of Cu ions can be controlled by the two integrated routes, which can change the physical properties of the CZO nanostructures.

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49

Hui-WenShen et 沈卉紋. « Growth and Electrical Properties of Indium Doped ZnO Nanostructures ». Thesis, 2011. http://ndltd.ncl.edu.tw/handle/77454926687277165849.

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50

Shih-PingKao et 高世萍. « Preparation and physical properties of Sb doped ZnO nanostructures ». Thesis, 2011. http://ndltd.ncl.edu.tw/handle/61187167841416387392.

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