Дисертації з теми "Dimensional Nanostructure"
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Fedorenko, Viktoriia. "Atomic layer deposition on three dimensional silicon substrates for optical biosensors applications." Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTT183/document.
Повний текст джерелаThis thesis manuscript presents the investigations and potential applications as a (bio)sensor platform of the conform thin layers of ZnO and/or Al2O3/ZnO nanolaminates, deposited by atomic layer deposition (ALD) on the various substrates. First, a study of the optical properties of ZnO thin films (20 and 50 nm) deposited by ALD technique on the large areas of ordered silicon nanowires (SiNWs), produced by combining nanosphere lithography and metal-assisted chemical etching, was performed. These methods allowed the morphology and the organization control of SiNWs on a large area. The detailed study of structural and optical properties of core-shell SiNWs/ZnO heterostructure was done by utilizing XRD, SEM, reflectance and photoluminescence spectroscopy, respectively. Integration of SiNWs arrays as core and ZnO as shell can have a strong impact on the development of sensing elements with improved properties. In the further investigations, ZnO films formed by ALD as an optical biosensor platform for the detection of Grapevine virus A-type proteins (GVA-antigens) were represented. The GVA-antigen detection was performed using the changes in the GVA related PL band behavior. The biosensor selectivity has been proved. The possibility to detect GVA-antigens without additional labels has been demonstrated. Thus, label free and sensitive photoluminescence based biosensor for GVA-antigens has been developed. Another part of our study is a specific control of protein anchoring by the development of multifunctional surface with large-scale array of polystyrene spheres (PSS), which produced by nanosphere lithography and further blocking the unspecific adsorption of protein on the surface of the PSS by PEG SAMs. The epifluorescence microscopy was used to confirm that after immersion of sample on target protein (avidin and anti-avidin) solution, the latter are specifically located on polystyrene sphere. These results are meaningful for exploration of devices based on large-scale nanoarray of PS spheres and can be used for detection of target proteins or simply to pattern a surface with specific proteins. Our research also includes the tuning of structural properties and the enhancement of electronic and optical properties of 1D PAN ZnO/Al2O3 nanolaminates designed by atomic layer deposition (ALD) and electrospinning. The structural and optical properties of Al2O3/ ZnO determined from the XPS, TEM, FTIR, XRD and PL analysis. The enhancement of electronic and optical properties would allow application in different fields such sensors and biosensors
Zhou, Zhengzhi. "Synthesis of one-dimensional nanostructure materials." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29703.
Повний текст джерелаCommittee Chair: Deng,Yulin; Committee Member: Hsieh, Jeffery S.; Committee Member: Nair, Sankar; Committee Member: Singh, Preet; Committee Member: Yao, Donggang. Part of the SMARTech Electronic Thesis and Dissertation Collection.
Piccotti, Diego. "Two-Dimensional Nanostructure Arrays for Plasmonic Nanolasers." Doctoral thesis, Università degli studi di Padova, 2019. http://hdl.handle.net/11577/3423324.
Повний текст джерелаNell'ultima decina di anni, l'interesse per i nanolaser plasmonici è cresciuto siccome sono uno tra i modi più promettenti per la miniaturizzazione dei laser. Infatti, questi dispositivi possono superare il limite di confinamento fisico della luce, grazie alla cavità virtuale data dalle nanostrutture plasmoniche che sostituiscono la convenzionale cavità ottica macroscopica. Inoltre, questi dispositivi plasmonici possono supportare modalità di funzionamento ad alta velocità, bassa soglia di emissione laser e una direzionalità ben definita. Per questa ragione, durante questo progetto, ci siamo concentrati sulla progettazione, la sintesi e la caratterizzazione di nanolasers plasmonici basati su array di nanocupole di oro e array di nanodischi di argento. Al fine di sintetizzare reticoli di nanoparticelle con un ordine elevato, abbiamo utilizzato la Nanosphere Lithography (NSL), una tecnica economica e ad alta produttività basata sull'autoassemblaggio di nanosfere di polistirene. Grazie alla versatilità della NSL, abbiamo sviluppato diversi protocolli di nanofabbricazione, combinando la NSL con i processi di Reactive Ion Etching (RIE) e deposizione fisica da vapore (PVD). Successivamente, abbiamo studiato le proprietà ottiche dei campioni sintetizzati, ricostruendo la struttura a bande ottica lungo le direzioni di alta simmetria dello spazio reciproco. Abbiamo selezionato due adeguati emettitori coloranti, la Pyridine 2 e lo Styryl 9M, al fine di accoppiare la loro emissione con le modalità ottiche dei reticoli nanostrutturati, sulla base delle informazioni della struttura a bande ottica. Inoltre, per ottimizzare le proprietà plasmoniche e l'amplificazione del campo locale delle nanostrutture metalliche, delle simulazioni numeriche sono state effettuate tramite il software COMSOL Multiphysics. L'interazione tra il colorante e la struttura plasmonica ha generato un'emissione amplificata. In particolare, nel reticolo di nanocupole di oro accoppiato alla piridina 2 disciolta in etanolo, un'amplificazione dell'emissione si presenta a720nm con un comportamento a soglia a 0.9 mJ/cm^2 . Inoltre, è stata ottenuta un'emissione direzionale a 17° con una divergenza angolare di 3° che avviene lungo l'anomalia di Rayleigh. Confrontando i risultati dei reticoli di nanocupole di oro con quelli dei reticoli di nanocupole di silice, abbiamo concluso che i modi di reticolo danno un contributo alla direzionalità dell'emissione, mentre i modi plasmonici forniscono una riduzione della soglia laser superando così la perdita di energia. Il reticolo esagonale di nanodischi di argento mostra un comportamento simile a quello con le nanocupole di oro: abbiamo trovato una soglia laser a 1.6 mJ/cm^2 , con anche una simile FWHM. In questo caso, questo fascio è diretto a 65° e presenta una divergenza angolare di circa 14° . Inoltre, abbiamo studiato anche un nanolaser con un mezzo di guadagno a stato solido per l'interesse nelle applicazioni e nell'integrazione di dispositivi su chip. Il colorante laser Styryl 9M è incorporato in un film di PMMA e accoppiato con un reticolo di nanocupole di oro. Questo sistema a stato solido presenta un'emissione amplificata a 795 nm con una soglia di 1.2 mJ/cm^2 e una FWHM di circa 26 nm. Questo campione manifesta anche un'emissione direzionale a 24° con una divergenza angolare di 6° . Ulteriori ricerche hanno dimostrato la possibilità di eliminare il substrato, creando un dispositivo autoportante, che presenta un'emissione amplificata con proprietà simili a quella con il substrato. Infine, per discernere la natura spontanea o stimolata dell'emissione, abbiamo misurato la coerenza del raggio emesso. Tramite un interferometro di Michelson dedicato, la lunghezza di coerenza è stimata a circa 29 um per i reticoli di nanocupole d'oro sopra la soglia. Questo risultato ha dimostrato che è possibile ottenere un'emissione coerente, a bassa soglia e altamente direzionale, accoppiando un colorante fluorescente adeguato con una cavità virtuale opportunamente progettata e realizzata da una reticolo ordinato di nanostrutture plasmoniche.
Cha, S. N. "Nano scale devices based on one dimensional nanostructure." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597380.
Повний текст джерелаLee, Jae Woo. "Electrical characterization and modeling of low dimensional nanostructure FET." Thesis, Grenoble, 2011. http://www.theses.fr/2011GRENT070/document.
Повний текст джерелаAt the beginning of this thesis, basic and advanced device fabrication process which I haveexperienced during study such as top-down and bottom-up approach for the nanoscale devicefabrication technique have been described. Especially, lithography technology has beenfocused because it is base of the modern device fabrication. For the advanced device structure,etching technique has been investigated in detail.The characterization of FET has been introduced. For the practical consideration in theadvanced FET, several parameter extraction techniques have been introduced such as Yfunction,split C-V etc.FinFET is one of promising alternatives against conventional planar devices. Problem ofFinFET is surface roughness. During the fabrication, the etching process induces surfaceroughness on the sidewall surfaces. Surface roughness of channel decreases the effectivemobility by surface roughness scattering. With the low temperature measurement andmobility analysis, drain current through sidewall and top surface was separated. From theseparated currents, effective mobilities were extracted in each temperature conditions. Astemperature lowering, mobility behaviors from the transport on each surface have differenttemperature dependence. Especially, in n-type FinFET, the sidewall mobility has strongerdegradation in high gate electric field compare to top surface. Quantification of surfaceroughness was also compared between sidewall and top surface. Low temperaturemeasurement is nondestructive characterization method. Therefore this study can be a propersurface roughness measurement technique for the performance optimization of FinFET.As another quasi-1 D nanowire structure device, 3D stacked SiGe nanowire has beenintroduced. Important of strain engineering has been known for the effective mobility booster.The limitation of dopant diffusion by strain has been shown. Without strain, SiGe nanowireFET showed huge short channel effect. Subthreshold current was bigger than strained SiGechannel. Temperature dependent mobility behavior in short channel unstrained device wascompletely different from the other cases. Impurity scattering was dominant in short channelunstrained SiGe nanowire FET. Thus, it could be concluded that the strain engineering is notnecessary only for the mobility booster but also short channel effect immunity.Junctionless FET is very recently developed device compare to the others. Like as JFET,junctionless FET has volume conduction. Thus, it is less affected by interface states.Junctionless FET also has good short channel effect immunity because off-state ofjunctionless FET is dominated pinch-off of channel depletion. For this, junctionless FETshould have thin body thickness. Therefore, multi gate nanowire structure is proper to makejunctionless FET.Because of the surface area to volume ratio, quasi-1D nanowire structure is good for thesensor application. Nanowire structure has been investigated as a sensor. Using numericalsimulation, generation-recombination noise property was considered in nanowire sensor.Even though the surface area to volume ration is enhanced in the nanowire channel, devicehas sensing limitation by noise. The generation-recombination noise depended on the channelgeometry. As a design tool of nanowire sensor, noise simulation should be carried out toescape from the noise limitation in advance.The basic principles of device simulation have been discussed. Finite difference method andMonte Carlo simulation technique have been introduced for the comprehension of devicesimulation. Practical device simulation data have been shown for examples such as FinFET,strongly disordered 1D channel, OLED and E-paper
Tran, Hoang Anh. "One-Dimensional Nanostructure and Sensing Applications: Tin Dioxide Nanowires and Carbon Nanotubes." PDXScholar, 2016. http://pdxscholar.library.pdx.edu/open_access_etds/2689.
Повний текст джерелаHarfenist, Steven A. "Structure and characterization of passivated inorganic nanocrystals and three dimensional nanocrystal arrays." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/30776.
Повний текст джерелаPatel, Mumukshu D. "Three-Dimensional Carbon Nanostructure and Molybdenum Disulfide (MoS2) for High Performance Electrochemical Energy Storage Devices." Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc1062842/.
Повний текст джерелаZHANG, JIE. "INVESTIGATIONS OF OXIDE AND SULFIDE BASED LOW DIMENSIONAL NANO STRUCTURES FOR CONDUCTOMETRIC GAS SENSORS, MEMRISTORS AND PHOTODETECTORS." OpenSIUC, 2015. https://opensiuc.lib.siu.edu/dissertations/1086.
Повний текст джерелаMcCune, Mallarie DeShea. "Fundamental study of the fabrication of zinc oxide nanowires and its dye-sensitized solar cell applications." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44725.
Повний текст джерелаLiu, Erming. "Synthesis of one-dimensional nanocomposites based on alumina nanofibres and their catalytic applications." Thesis, Queensland University of Technology, 2011. https://eprints.qut.edu.au/48323/1/Erming_Liu_Thesis.pdf.
Повний текст джерелаYiu, Wing-ching James. "Synthesis of one-dimensional tungsten oxide nano-structures by thermal evaporation." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B32047770.
Повний текст джерелаYiu, Wing-ching James, and 姚穎貞. "Synthesis of one-dimensional tungsten oxide nano-structures by thermalevaporation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B32047770.
Повний текст джерелаHuang, Wenyu. "Fundamental studies of the interaction between femtosecond laser and patterned monolayer plasmonic nanostructures." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/24786.
Повний текст джерелаCommittee Chair: El-Sayed, Mostafa A.; Committee Member: Perry, Joseph W.; Committee Member: Srinivasarao, Mohan; Committee Member: Whetten, Robert L.; Committee Member: Zhang, Z. John.
Mayers, Brian T. "Synthetic approaches to one-dimensional nanostructures /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/8685.
Повний текст джерелаKirkham, Melanie. "The role of the catalyst in the growth of one-dimensional nanostructures." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31687.
Повний текст джерелаCommittee Co-Chair: Snyder, Robert L.; Committee Co-Chair: Wang, Zhong Lin; Committee Member: Garmestani, Hamid; Committee Member: Summers, Christopher; Committee Member: Wilkinson, Angus. Part of the SMARTech Electronic Thesis and Dissertation Collection.
Hong, Kunquan. "Synthesis of one-dimensional tungsten oxide nanostructures." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/HKUTO/record/B39558551.
Повний текст джерела洪昆權 and Kunquan Hong. "Synthesis of one-dimensional tungsten oxide nanostructures." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B39558551.
Повний текст джерелаWhite, Richard. "Synthesis and characterisation of three-dimensional nanostructures." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612473.
Повний текст джерелаMayhew, Eric Kenji. "THERMAL CHARACTERIZATION OF ONE-DIMENSIONAL CARBON NANOSTRUCTURES." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1370033766.
Повний текст джерелаXu, Ke Lewis Nathan Saul Heath James R. "Nonlinear electrical properties of one-dimensional nanostructures /." Diss., Pasadena, Calif. : California Institute of Technology, 2009. http://resolver.caltech.edu/CaltechETD:etd-06012009-021047.
Повний текст джерелаBell, Kimberley F. "Electric force microscopy of one dimensional nanostructures." Thesis, Swansea University, 2010. https://cronfa.swan.ac.uk/Record/cronfa42694.
Повний текст джерелаBohorquez, Ballen Jaime. "Thermal transport in low dimensional semiconductor nanostructures." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/dissertations/798.
Повний текст джерелаMosley, David W. "Two-dimensional polymer synthesis : towards a two-dimensional replicating system for nanostructures." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33652.
Повний текст джерелаVita.
Includes bibliographical references
The general concept of a replicating monolayer system is introduced as a new method of nanostructure synthesis. One possible implementation of a 2-D replicating system is pursued which uses a diacetylene moiety for cross-linking and amide hydrogen bonding for molecular recognition between replicates and templates. The synthesis of several monomers for amide hydrogen-bonded adlayer formation is described. The assembly and crosslinking of diacetylene monomers on an underlying amide-capped self- assembled monolayer (SAM) was studied on unpatterned thermally evaporated gold films. Raman and Fourier-transform infrared spectroscopies, as well as ellipsometry and contact angle data, indicate that amide hydrogen bonding interactions are sufficient to organize an adlayer of diacetylene-containing molecules on the underlying SAM which can be polymerized with ultraviolet light. In order to obtain gold substrates suitable for cross-linking of bis(diacetylene) monomers, new methods of producing ultraflat gold surfaces were developed.
(cont.) A solid- state bonding technique using only gold was developed, yielding ultraflat gold surfaces, with root-mean-square roughnesses of -0.5 nm, on glass slides which are free of impurities from epoxies or other bonding agents. The patterning and cross-linking of poly(diacetylene) adlayers on ultraflat gold surfaces was investigated by atomic force microscopy (AFM). Soft lithography was suitable for adlayer structures down to about 500 nm. Electron beam lithography for patterning of polymerizable adlayers was demonstrated for the first time. The polymerized adlayer patterns were significantly more difficult to remove from the gold surface than unpolymerized adlayer patterns, indicating cross-linking. Studies to remove adlayer patterns as intact 2-D polymers failed, due either to poor cross-linking or robustness of the resulting 2-D polymers. In another approach to nanostructure synthesis, the synthesis of monofunctionalized gold nanoparticles by a solid phase synthetic route was described. This represents a versatile method of producing monofunctionalized nanoparticles, which can be used to produce and study more elaborate nanoparticle structures.
by David W. Mosley.
Ph.D.
Perotto, Giovanni. "TWO DIMENSIONAL SELF ASSEMBLY OF NANOSPHERES, A VERSATILE METHOD FOR NANOFABRICATION." Doctoral thesis, Università degli studi di Padova, 2010. http://hdl.handle.net/11577/3422011.
Повний текст джерелаIl campo delle nanotecnologie è uno dei più innovativi e multidisciplinari della ricerca moderna. Sempre pi`u numerose diventano le tecniche per manipolare la materia su scala nanometrica, modificando così le proprietà fisico, chimiche e morfologiche a livelli mai raggiunti prima. Alla nano scala la manipolazione morfologica è accompagnata dal cambiamento delle proprietà che smettono di essere intrinseche della materia ma diventano dipendenti da altri fattori come la forma, la dimensione e l’ambiente in cui le nanostrutture sono immerse. Uno dei casi più eclatanti è il colore dell’oro e dell’argento quando sono sottoforma di particelle nanometriche. L’oro, ad esempio, può essere di colore rosso-vino, verde, blu e nero, semplicemente cambiando la forma o l’ambiente attorno ad esso. Manipolando la materia opportunamente possono comparire nuove proprietà come la trasmissione della luce attraverso aperture che sono molto più piccole della lunghezza d’onda della luce, dando la possibilità di ottenere il controllo della propagazione della luce ad un livello molto intimo. Si può capire quindi come per poter sfruttare le enormi potenzialità offerte dalle nanotecnologie sia importante avere tecnologie di fabbricazione che permettano un preciso controllo nella produzione di oggetti nanometrici o con strutture nanometriche. Le tecnologie al momento disponibili che permettono di creare strutture con precisione molto elevata (pochi nanometri) sono tecnologie ”seriali” come l’Electron Beam Lithography o il Focused Ion Beam. Queste tecniche sono limitate alla produzione di un oggetto alla volta e quindi comportano costi elevati e lunghi tempi. Le tecnologie ”parallele” derivano dall’industria dei semiconduttori e sono tecniche litografiche che hanno come limite la risoluzione della luce utilizzata ( 200nm). In questo lavoro di tesi si cercherà di dare risposta alla domanda di tecniche di fabbricazione di strutture nanometriche utilizzando una tecnica che abbia le seguenti caratteristiche: • quickness • low cost • ability to synthesize very small nanostructures • reproducibility • easy implementation Si è scelto di utilizzare la capacità della materia di organizzarsi spontaneamente in strutture ordinate. In particolare si è sfruttata la tendenza di nanoparticelle sferiche di polistirene ad impaccarsi in strutture compatte ed ordinate costituendo dei ”cristalli colloidali”. Un singolo strato di nanosfere autoassemblate è una struttura interessante perchè presenta dei pori tra le particelle di forma e dimensioni ben definite, che possono essere modificate cambiando le dimensioni delle sfere che costituiscono il cristallo bidimensionale. Verrà illustrato un metodo semplice e rapido per ottenere questi monostrati di particelle ordinate e per poterli depositare su vari substrati. Questi cristalli bidimensionali verranno utilizzati per depositare una matrice ordinata di nanoparticelle plasmoniche, con un ottimo controllo sulla loro forma e dimensioni, consentendo di realizzare particelle con proprietà su misura per l’applicazione desiderata. Verranno anche studiate applicazioni di queste nanoparticelle come sensori di molecole e per amplificare il segnale Raman grazie all’effetto SERS. Verrà inoltre studiato l’aumento di temperatura di queste nanoparticelle quando vengono illuminate da un laser risonante con la loro risonanza di plasma di superficie. Per applicazioni spettroscopiche applicate a sistemi biologici il cambiamento di temperatura può avere effetti rilevanti in un ambiente complesso come quello biologico. In seguito verrà dimostrato come questi cristalli colloidali bidimensionali possono essere utilizzati per creare altre classi di nanostrutture, come ad esempio una matrice di buchi nanometrici in un film metallico. Queste strutture sono studiate da quando è stato scoperta la loro capacità di far trasmettere attraverso strutture che sono molto minori del limite di diffrazione per le lunghezze d’onda trasmesse. Una sintesi che si basa sulle nanosfere autoassemblate può essere interessante per queste strutture grazie alla sua intrinseca flessibilità. Si possono infatti cambiare in modo molto semplice i parametri geometrici che caratterizzano la matrice di buchi quali le dimensioni dei buchi e il periodo degli stessi. Un’altra tipologia di nanostrutture che verrà realizzata sono film sottili nanostrutturati di TiO2. La titania è un semiconduttore di grande interesse tecnologico in molti campi diversi: dalla catalisi, alla conversione di energia ai sensori di gas. Verranno fabbricati, con la stessa tecnologia, dei film con una porosità ordinata e delle superfici nanostrutturate con un motivo a incavi. Infine verrà dimostrata la possibilità di utilizzare i cristalli colloidali 2D accoppiati con una tecnologia molto utilizzata dall’industria dei semiconduttori quale l’impiantatore ionico. Pattern nanometrici verranno realizzati su silicio utilizzando le nanoparticelle autoassemblate come maschera per il fascio ionico.
Qiu, Yongfu. "Controlled growth and characterization of one-dimensional nano-structured materials /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?NSNT%202008%20QIU.
Повний текст джерелаYi, Ge. "Single-crystal superconducting Pb nanowires and nanostructures." Thesis, University of Bristol, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266955.
Повний текст джерелаAhmad, S. T. "Low dimensional hybrid ferromagnetic AlGaAs/GaAs semiconductor nanostructures." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.595379.
Повний текст джерелаOng, Luvena Le-Yun. "Self-assembly of three-dimensional nucleic acid nanostructures." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/106741.
Повний текст джерелаCataloged from PDF version of thesis.
Includes bibliographical references (pages 137-148).
Patterning complex 3D features at the nanoscale offers potential applications for a wide range of fields from materials to medicine. While numerous methods have been developed to manipulate nanoscale materials, these methods are typically limited by their difficulty in creating arbitrary 3D patterns. Self-assembly of nucleic acids has emerged as a promising method for addressing this challenge due to the predictability and programmability of the material and its structure. While a diversity of DNA nanostructures have been designed by specifying complementarity rules between strands, creation of 3D nanostructures requires careful design of strand architecture, and patterns are often limited to a volume of 25 x 25 x 25 nm³ Here, we address the challenges in structural DNA nanotechnology by developing a modular DNA "brick" approach. These bricks are short, single-stranded oliogomers that can self-assemble in a single-pot reaction to a prescribed 3D shape. Using this modular approach, we demonstrate high efficiency in 3D design by generating 100 distinct, discrete 3D structures from a library of strands. We also created long-range ordering of channels, tunnels, and pores by growing micron-sized 3D periodic crystals made from DNA bricks. Finally, we applied this approach to control over 30,000 unique component strands to selfassemble into cuboids measuring over 100 nm in each dimension. These structures were further used to pattern highly complex cavities. Together, this work represents a simple, modular, and versatile method for 3D nanofabrication. This unique patterning capability of DNA bricks may enable development of new applications by providing a foundation for intricate and complex control of an unprecedented number of independent components.
by Luvena Le-Yun Ong.
Ph. D. in Medical Engineering and Medical Physics
Knittel, Andreas. "Micromagnetic simulations of three dimensional core-shell nanostructures." Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/333186/.
Повний текст джерелаPark, Jungkyu. "THERMAL TRANSPORT IN NOVEL THREE DIMENSIONAL CARBON NANOSTRUCTURES." Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1455101197.
Повний текст джерелаCottam, Ben Francis. "The synthesis of one-dimensional titanium oxide nanostructures." Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/11985.
Повний текст джерелаCheng, Chun. "Fabrication and characterization of one dimensional ZnO nanostructures /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?NSNT%202009%20CHENG.
Повний текст джерелаDuong, Binh. "PROCESSING AND ANALYSIS OF ONE-DIMENSIONAL CARBON NANOSTRUCTURES." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/205414.
Повний текст джерелаMei, Jun. "Optimization of two-dimensional nanostructures for rechargeable batteries." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/135045/1/Jun%20Mei%20Thesis.pdf.
Повний текст джерелаMavundla, Sipho Enos. "One-Dimensional nanostructured polymeric materials for solar cell applications." Thesis, University of the Western Cape, 2010. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_1088_1305888911.
Повний текст джерелаThis work entails the preparation of various polyanilines with different morphologies and their application in photovoltaic solar cells. Zinc oxide (ZnO) with one-dimensional and flower-like morphology was also prepared by microwave irradiation and used as electron acceptors in photovoltaics devices. The morphological, structural, spectroscopic and electrochemical characteristics of these materials were determined by scanning electron microscopy (SEM), X-Ray diffraction (XRD), Raman, Fourier-transformed infrared spectroscopy (FTIR), ultraviolet and visible spectroscopy (UV-Vis), photoluminescence(PL), thermal gravimetric analysis (TGA) and cyclic voltammetry (CV) experiments. Devices fabricated from these materials were characterized under simulated AM 1.5 at 800 mW.
Wen, Xiaogang. "Organized one dimensional nanomaterials : from preparations to applications /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202005%20WEN.
Повний текст джерелаBocharova, Vera. "Electrically Conductive Low Dimensional Nanostructures: Synthesis, Characterisation and Application." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1231161926227-23379.
Повний текст джерелаCameron, Craig G. "Natural and artificial fluorescence on 3-dimensional bioorganic nanostructures." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53451.
Повний текст джерелаLiu, Chang-Chih, and 劉長治. "Design and Analysis of One Dimensional Nanostructure." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/52550389399345600840.
Повний текст джерела義守大學
電子工程學系碩士班
94
Schrodinger equation is the quantum mechanics foundation,in which involves a specific potential energy function,But actual problem potential energy function is suitable complex,therefore we needed to develop the numerical method solve schrodinger equation.Transfer Matrix Method can solve any potential energy function in schrodinger equation to be able to energy level and wave function.Again analyzes potential energy of the physics significance,then can analyzes schrodinger equation of physical property.
Wu, Chii-Wai, and 吳啟偉. "Two-Dimensional Nanostructure Fabrication by Langmuir-Blodgett Technique." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/34630809638247326891.
Повний текст джерела中原大學
應用物理研究所
94
In this thesis, we introduce the principle and application of the Langmuir-Blodgett technique. By this method, we fabricate the ordered Polystyrene 2D structure, and discuss the relation between the surface pressure and the area of the LB-film in the process of forming the 2D structure. The surface pressure increases as compressing the bipolar molecules on the air/water interface continuously. As the separation distance between molecules decreasing, the surface pressure goes through two phase transitions (2D-gas to 2D-liquid and 2D-liquid to 2D-solid). If PS micro-balls have the similar behavior on the air/water interface, such two phase transitions should be observed. In the case of 1�慆 in diameter, we observe two phase transitions successfully. In the 150nm and 250nm cases, we only discover one phase transition (2D-gas to2D-liquid). As the phase transition occurs, the ratio of separation distance to micro-ball diameter (D/R value) is less than unity. This phenomenon is possibly due to the non-uniformity caused by the thermal fluctuation. More over, we try to disperse silver nano-powder into HPLC grade chloroform to get the suspension with ultrasonic cleaner. However, the concentration of the suspension is far thinner than 1mg/ml, so it is difficult to apply in this LB technique.
Cheng, Hsien-Lung, and 鄭憲隆. "One-dimensional silicon nanostructure for hydrogen gas sensor." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/82604143772786903888.
Повний текст джерела國立臺灣科技大學
電子工程系
100
There are many technologies to fabricate one-dimensional silicon nanostructure. The silicon nanostructures were used for many applications. For example, the silicon nanostructures have high reflection property in solar cell. In the electron field emission, the silicon nanostructures possess the higher aspect ratio and numerous emission sites. For sensor researching, it has higher surface area to volume ratio that can improve the sensitivity. We fabricated the one dimension silicon nanostructure for hydrogen sensor. In this research, we synthesized different morphology of silicon nanostructure using wet electroless etching technique. The field emission scanning electron microscopy (FE-SEM) was used to observe the surface morphology of silicon nanostructure. The micro-Raman and Fourier transform infrared (FT-IR) was used to investigate the bonding of silicon nanostructure. Finally, we carried out the electrical analyze of gas sensor system with hydrogen sensing. In this study, we use the two-step wet electroless etching technique to form the straw-like silicon nanowire. It can be observed that some different layers in SEM photographs. The top layer was straw-like silicon nanowire, and the middle layer was straight aligned silicon nanowire, and the bottom layer was silicon base which is the bulk silicon. The straw-like silicon nanowire was found the the bonding of Si-O-Si about 1173cm-1 in FT-IR spectrum. And it also observed some red shift in Raman spectrum. Because of the higher surface area to volume ratio and Si-O-Si bonding, the performance of this straw-like structure hydrogen sensor was improved. Moreover, this hydrogen gas sensor was also modified with Pt nanoparticles, which can enhance the ratio of hydrogen gas dissolve into the metal-semiconductor interface. Finally we tried to make the porous structure with high density and high aspect ratio also by wet electroless etching technique. This porous possessed the high surface area which had the superior sensitivity.
Yu, Ze-Yi, and 余則易. "One-dimensional growth of potassium titanate nanostructure and its photoluminescence." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/zm9237.
Повний текст джерела國立東華大學
物理學系
100
Potassium titanate (M2TinO2n+1,M=K,n=6) has been taken as an exemplar system to disclose conditions for directly forming one-dimensional (1D) oxide nanostructures on titanium substrates with modifiable optical properties. Morphology and spatial distribution of the surface-layer oxides were found to depend on the temperature and duration of anneals, whereas the potassium-containing oxides were confined in a thin surface layer. Results of XRD and Raman scattering showed the phase formation scenarios of anatase, rutile, and potassium hexatitanate. Transmission electron microscopy was performed to reveal the 1D nanostructures as monoclinic K2Ti6O13 single crystals extending along <010>. Ring-like patterns observed in selected-area electron diffraction reflected the fact thatthe 1D nanocrystals derived from a multi-crystalline precursor exhibiting hexatitanate-similarlattice d-spacings. A growth model was proposed for the K2Ti6O13 crystals, signifying the role of the early-stage crystallizationwhich dominates the following 1D growth. Photoluminescence spectra showed a broad peak within the range of 2-3 eV, wherein the intensity maximum systematically shifted due to competitive contributions from the phases of anatase, rutile and potassium hexatitanate.
Ajayi, Obafunso. "Optical Studies of Excitonic Effects at Two-Dimensional Nanostructure Interfaces." Thesis, 2017. https://doi.org/10.7916/D87H1K4K.
Повний текст джерелаChing-YiHsieh and 謝靜宜. "Development of three-dimensional DNA nanostructure for anti-bacteria strategy." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/fb9224.
Повний текст джерела國立成功大學
口腔醫學研究所
103
The rapid development of nanomedicine based on theranostic has gradually evolved into practical clinical applications. Recently, researchers have reported that certain inorganic nanomaterial may induce cytotoxicity and biological dysfunction. DNA is an intrinsic biological macromolecule thus their nanostructures were regarded as excellent carriers with low toxicity and high biocompatibility. In my study, I would like to develop an advanced theranostic platform based on a self-assembled DNA nanostructure as scaffold with targeting aptamer and carrying antibiotics. Antimicrobial molecules (Actinomycin D, AMD) will be attached to minor groove of DNA double helix through hydrogen bond. The DNA nanostructure system serves as carriers for targeting delivery of AMD to attack bacteria. Currently, the DNA nanostructure system has been assembled and was confirmed by DNA agarose gel electrophoresis. Cryo-electron microscopy (cryo-EM) and three-dimensional (3D) reconstruction technique showed the DNA nanostructure system was a hollow spherical structure. In addition, we found a single DNA nanostructure could carry 2409.47 AMD molecules when saturated. We further found that the anti-bacteria ability of our system had a higher efficacy than free AMD. In the aptamer binding assays, we demonstrated the aptamer target specifically to Streptococcus mutans.
Lin, Chih-Cheng, and 林志誠. "Synthesis of one dimensional zinc oxide nanostructure and their applications." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/63578305590107406547.
Повний текст джерела國立中正大學
化學工程所
96
In this thesis, we prepared high purity and uniform one-dimensional zinc oxide nanostructures by thermal evaporation and thermal decomposition methods. The research includes the studies of the structure of these materials and explores their applications. Fundamentals of one-dimensional zinc oxide nanomaterials were reviewed in chapter 1. The structure of these one-dimensional zinc oxide nanomaterials and their field emission, photocatalytic activity and UV photodetector applications were systemaically studied and reported in chapter 2-4. In chapter 2, one-dimensional ZnO nanostructures were fabricated on a tin-doped indium oxide (ITO) glass substrate by thermal evaporation of Zn powder at 400 oC. ZnO nanocones, ZnO nanorods, and ZnO nanowires can be synthesized with a catalyst-free ITO glass, a Pt-coated ITO glass, and an Au-coated ITO glass, respectively. The XRD and TEM investigations show that ZnO nanostructures possess good crystallinity with growth direction along the c-axis of the crystal plane. Field emission studies reveal ZnO nanorod arrays with a turn-on voltage of 3.4 V/μm at a current density of 10 μA/cm2. This study finds that morphology and growth direction of the ZnO nanostructures affect the field emission property. In chapter 3, high-purity single crystal ZnO nanowires were synthesized by the thermal decomposition of zinc acetate dihydrate at 300 oC in air without the presence of catalyst. The zinc acetate dihydrate was characterized by thermogravimetry-differential scanning calorimetry and mass spectrometry (TG-DSC-MS) to determine its thermal decomposition and crystallization temperature. The ZnO nanowires were generated by a dehydration, vaporization/decomposition, and deposition/formation process. In addition, the ZnO nanowires showed a relatively good photocatalytic activity in the degradation of NOx. The NO concentration decreased from 1 ppm to 0.1 ppm. In chapter 4, high purity, vertically aligned ZnO nanowires were synthesized uniformly on a tin-doped indium oxide (ITO) glass substrate. The ZnO nanowire arrays with a uniform diameter distribution of 30~50 nm and a length of about 5 μm were formed by the thermal decomposition of zinc acetate at 300 oC in air. The study of growth mechanism found that it is a vapor-solid (VS) growth mechanism with a sequence of the processes including dehydration, vaporization, decomposition and oxidation of the zinc acetate, deposition of ZnO clusters for the formation of the seeds and finally selectively epitaxial growth of the ZnO nanowires. The photocurrent characteristics and UV photoresponse of the ZnO nanowire photodetectors were investigated. Under illumination using the UV light with a wavelength of 365 nm, photo-generated current was measured at 15 μA at a bias of 2 V. The fabrication method is a simple, catalyst-free and cost-effective (low temperature, one chemical agent used only) for the growth of high quality ZnO nanowire arrays. The study on the optical properties and the UV photodetector device found that the as-produced ZnO nanowires are of great potential on the applications of photodetector/sensor in the UV region. In addition, the turn-on field for the ZnO nanowires growth at 300 oC was found about 3.5 V/μm at current density of 10 μA/cm2. The emission current density from the ZnO nanowires growth at 300 oC reached 1 mA/cm2 at an applied field of 7.0 V/μm.
Yao, I.-Chuan, and 姚奕全. "Synthesis of One Dimensional Zinc Oxide Nanostructure and their Applications." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/45832147009795458547.
Повний текст джерела國立交通大學
材料科學與工程學系
100
One-dimensional nanostructers are a new class of advanced materials that have been receiving a lot of research interest in the last decade due to their superior physical and chemical properties. Among one-dimensional materials, zinc oxide (ZnO) is one of the most important materials and has attracted much interest in recent years, due to its unique optical, electrical, and piezoelectric properties and versatile applications. In this dissertation, we propose new methods or technologies to improve the applications of 1D ZnO nanostructure. Macrostructure of the samples was characterized by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The optical and electrical properties were investigated by photoluminescence (PL) and current–voltage (I–V) characterization. The main focus of this dissertation can be divided into four parts. In first part, we demonstrate a simple method to fabricate ZnO nanotip array, which exhibit low turn-on field, high field enhancement factor and stable field emission properties at 25-100 ℃. The good field emission properties are attributed to reduced oxygen vacancy concentration and small tip angle of ZnO emitters, which shows good potential for developing field emission and light emiting devices. In the second part, we provide another interesting route of fabricating ZnO-SnO2 core-shell nanowires for gas sensor applications. The ZnO-SnO2 core-shell nanowires exhibited good hydrogen sensor performance, such as the sensitivity is up to 89% against 200 ppm hydrogen at 250℃. Such high sensitivity was believed to be controlled by the nanoscale SnO2 layer, which was determined from pinch-off and fully conductive state. The ZnO-SnO2 core-shell nanostructures made by two-step chemical growth have high potential for gas sensor application. In the third part, vertical well-aligned and uniform ZnO nanorods were successfully prepared on low cost and flexible PET polymer substrate by aqueous solution method under various growth conditions. The photocurrents can be repeatly and reproducibly switched by modulating UV exposure with power densities of 25-70 μW/cm2. The fast response time (100 sec) and rapid recovery time (120 sec) are achieved in UV turn-on/off switching measurements. Owing to the mechanical flexibility, nondestructive properties, high reliability and multilevel photoresponse, the well-aligned ZnO nanorods grown on transparent and flexible PET polymer substrates have high potential for UV photodetector applications. In the fourth part, vertically well-aligned and uniform Ga¬-doped ZnO (GZO) nanorod thin films were successfully grown on Au/Ti/SiO2/p-Si substrates, which used to make resistive switching memory devices. Such memory devices can be reversibly switched between ON and OFF states, with a stable resistance ratio of 10 times, narrow dispersion of ON and OFF voltages, and good endurance performance of over 100 cycles. The resistive switching mechanism in this design is related to the formation and rupture of conducting filaments consisting of oxygen vacancies, occurred at interfaces between GZO nanorods (grain boundaries). Results show that the resulting compact GZO nanorod thin films have a high potential for resistive memory applications.
Shen, Kuo-Jen, and 沈國任. "The growth of Zinc Oxide material with one-dimensional nanostructure." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/15042977028347438424.
Повний текст джерела國立成功大學
化學工程學系碩博士班
94
Abstract Three main subjects on the growth of Zinc oxide with one-dime nsional nanostructure have be studied. The first part is the effect of vapor species in controlling ZnO nanoarchitectures. The second one is the influence of substrates upon the vertical aligned ZnO nanowires. The last section is the effect of electrical field on the direction growth of ZnO NW. At first, the architectures of ZnO nanomaterials could be controlled by varying the composition of O2 gas and substrate temperature during growths. At higher O2 concentration, ZnO nanowires growing along [0001] were synthesized. At lower O2 concentration, ZnO nanobelts growing along [0001] or were synthesized. The width of ZnO nanobelts increased with the reduction of O2 concentration. Photo- lumen escence(PL) spectra measurement indicated that ZnO nanobelts contained a lower concentration of structure defects than ZnO nanowires. During the substrate temperature decreased to 550℃, the morphology of ZnO became thin-film structure. However, the substrate temperature increased to 900℃, the densities of ZnO nanowires decreased. Regardless of temperature increased or decreased, ZnO nanowires grow along [0001]. PL spectra analysis indicated that ZnO nanowire, fabricated at high temperature, contained a lower concentration of structure defects Secondly, the vertical aligned ZnO nanowires could be controlled by varying the conditions and substrates during growth. At different conditions, the vertical aligned ZnO nanowire grown on the surface of Si substrates containing Au catalyst. The major factor is the ZnO buffer layer formed on Si substrate. Then, growing the vertical aligned ZnO nanowires on the different substrates, including Si substrates containing Au catalyst, c-plane sapphire containing Au catalyst, and Al-doped ZnO thin film glass substrate. Beside, nanowire grew in specific direction on the c-plane sapphire containing Au catalyst. The vertical aligned ZnO nanowires was also grew on the other substrates. The variation of morphology was caused by lattice mismatch. Furthermore, we also studied the influence of different seed layer on the nanostructure of ZnO of ZnO nanowire. Obviously, the nanowire tip was sharp when the ZnO nanoparticle as the seed layer ; when the Au nanoparticle as seed layer, the nanowire tip was formed hexagonal. We deduced that the growth rate of different crystal surfaces were main parameter on the formation of ZnO nanostructure. The last part is to study the effect of electrical field on the growth direction of ZnO nanowires. In this study, dielectrophoresis force was used align nanowires, fabricated by furnace, between inter-digital electr- odes. When E-field increased to 8.8 Vp-p and the frequency increased to 1MHz, the alignment of NWs become obviously. But, when the aligned ZnO nanowires were applied on the manufacture of transistor, the electrical behavior ZnO nanowires and electrode was schottky contact , and the transistor characteristics could not be observed. In order to directional growth ZnO nanowires, an electrical field was applied on the inter-digital electrodes during ZnO nanowires growth. When the electrical field was applied between the inter-digital electrodes, the growth of ZnO nanowire focused on the edge of electrodes. Although the densities of ZnO nanowires on the edge of electrodes were decreased, when the magnitude of electrical field were decreased, many nucleation sites were existed on the edge of electrodes. After growth , we used the aligned ZnO nanowires to fabricate transistor. The results of transistor characteristics shown that the electrodes and nanowires was ohimc contact. However, the gate voltage still could not be controlled.
Huang, Sung-Chien, and 黃松建. "Growth of one dimensional GaN nanostructure by using chemical vapor deposition." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/vb63vv.
Повний текст джерела國立臺灣科技大學
化學工程系
95
Gallium nitride(GaN) nanostructure were grown by metalorganic chemical vapor deposition using trimethylgallium(TMGa) as source material for Ga, and Ge nanowire、ZnO nanorod、Si(111) with 1 nm of Au as substrates. Si(111) coated with 1 nm Au was acted as a substrate. Heating the substrate until its temperature was 800℃ would form a sheet-like nanostructures. In the other hand, heating the substrates until its temperature was 550℃ would form a rod-like nanostructures. Well-aligned GaN nanorod structure were formed by increasing the feed ratio of Ⅴ/Ⅲ to 15000. GaN nanodots were formed on Ge nanowire substrate. Core-shell structure of GaN/ZnO nanorod、GaN/Ge nanowire were formed by atomic layer epitaxy(ALE) technique. The selective growth process of GaN nanorod on ZnO nanorod, which was coated with SiO2 and acted as substrate, was failed due to high temperature(850℃) and high NH3 concentration.
"Pseudo-one-dimensional Zn-Fe-O nanostructure arrays: controlled fabrication, magnetic properties and photocatalytic applications." 2013. http://library.cuhk.edu.hk/record=b6116186.
Повний текст джерела垂直排列的ZnO納米線陣列首先生長在不同的襯底上,然后进一步被用作其他納米結構陣列的生長模板。ZnO納米線不僅僅起到骨架定型的作用,最終還可以为后續納米結構提供原料组分。通過控制ZnO和氯化鐵溶液的反應時間,在煅燒后,我們可以製備ZnO/鐵酸鋅(ZnFe₂O₄)納米線纜陣列,以及化學/非化學計量的ZnFe₂O₄、ZnFe₂O₄/α-三氧化二鐵(α-Fe₂O₃)和α-Fe₂O₃納米管陣列。ZnFe₂O₄和α-Fe₂O₃納米管陣列都表現出了對可見光的吸收,它們的帶隙經估算分別是2.3 eV和1.7 eV。
通過電子能量損失譜(EELS),可以得到ZnFe₂O₄納米管陣列的一些細節的結構信息。我們分別研究了兩個不同系列(溫度和化學計量)的ZnFe₂O₄納米管。研究發現,樣品的磁性和它們的晶體結構有著非常緊密的關係。首先,對於溫度系列的樣品,當樣品的燒結溫度從600 °C降到400 °C時,更多的三價鐵離子(Fe³⁺)佔據了尖晶石結構中的A位置(四面體位置)而並非它們本應佔據的平衡B位置(八面體位置)。這種偏離了正常尖晶石結構的情況使得A和B位置上的Fe³⁺的超交換作用增加,進而增加了樣品的阻隔溫度(TB),磁各向異性常數(K),3K和300 K下的飽和磁化強度(MS)和3K下的矯頑力(HC)。同時使3K和300K下的MS的比值變小。其次,對於化學計量系列的樣品,通過比較在同一燒結溫度下製備的化學計量和非化學計量的ZnFe₂O₄納米管,我們發現在鐵鋅比大於2的納米管中,Fe³⁺佔據A和B位置的比例和化學計量的樣品是类似的。這些多出的Fe³⁺也會增加超交換作用,從而導致較大的TB, K, MS(3K和300 K),HC(3K)和較小的MS(3 K)/MS(300 K)比值。最後,作為非化學計量的極端情況,α-Fe₂O₃納米管在小的外加磁場下表現出了典型的Morin相變,在大的外加磁場下出現了場致spin-flop轉變。
另一方面,我們發現,當使用羅丹明B(RhB)作為指示劑時,ZnO/ZnFe₂O₄納米線纜陣列表現出了優於纯ZnO和纯ZnFe₂O₄納米管陣列的可見光降解活性,但是它們的降解路徑各不相同。ZnO由於染料敏化機制而具有可見光降解能力,但是其降解活性最差。ZnO/ZnFe₂O₄納米線纜陣列和ZnFe₂O₄納米管陣列的基本降解原理是相同的,那就是,利用有可見光活性的ZnFe₂O₄中的光生電子和空穴所生成的活性自由基降解RhB。但是,ZnO/ZnFe₂O₄納米線纜陣列的降解能力明顯優於ZnFe₂O₄納米管陣列,這是由於ZnO與ZnFe₂O₄之間的II型能帶匹配顯著地促進了光生電子和空穴的分離。
In the present thesis, several kinds of pseudo-one-dimensional Zn-Fe-O nanostructure arrays with tunable chemical compositions, crystal structures and morphologies are successfully synthesized via a simple wet-chemical ZnO-nanowire-array templating method.
Vertically-aligned ZnO nanowire arrays are firstly fabricated on several different substrates and then serve as templates for other nanostructured arrays growth. The ZnO nanowires not only act as morphology-defining skeleton but also contribute chemically to the final composition of the nanostructures. By controlling the reaction time between ZnO and FeCl₃ solution, ZnO/ZnFe₂O₄ nanocable arrays, stoichiometric ZnFe₂O₄ nanotube arrays, nonstoichiometric ZnFe₂O₄ nanotube arrays, ZnFe₂O₄/α-Fe₂O₃ nanotube arrays and α-Fe₂O₃ nanotube arrays can be synthesized in a controlled manner after calcination. Both ZnFe₂O₄ and α-Fe₂O₃ nanotube arrays exhibit visible light absorption and their bandgap are estimated to be ~2.3 eV and ~1.7 eV, respectively.
The detailed structural information of the ZnFe₂O₄ nanotube arrays are obtained by electron energy loss spectroscopy (EELS). In particular, EELS are carried out for two different series (i.e., temperature and stoichiometric series). The magnetic properties of these samples are found to closely correlate to their structural characteristics. Firstly, with the decrease of the calcination temperature from 600 °C to 400 °C, more Fe³⁺ions occupy A sites (tetrahedral sites in spinel structure) rather than their equilibrium B sites (octahedral sites in spinel structure). The deviation from the normal spinel structure leads to the enhancement of superexchange interactions between Fe³⁺ions in A and B sites, and thus results in an increase in blocking temperature (TB), magnetic anisotropic constant (K), saturation magnetization (MS, at 3 K and 300 K), coercivity (HC, at 3 K) and a decrease in MS(3 K)/MS(300 K) ratios. Secondly, by comparing stoichiometric and nonstoichiometric ZnFe₂O₄ nanotubes calcinated at the same temperature, we found that the nonstoichiometric nanotubes (Fe:Zn > 2) shows similar ratios of Fe³⁺in A and B sites to that of the stoichiometric one. The extra Fe³⁺in the crystal also enhances the superexchange interactions of Fe³⁺, which results in larger TB, K, MS(at 3 K and 300 K) and HC(at 3 K), and smaller MS(3 K)/MS(300 K) ratio. Lastly, α-Fe₂O₃ nanotubes, as an extreme case of the nonstoichiometric sample, show typical Morin-transition characterization under small external field, and field-induced spin-flop transition at large external field.
On the other hand, we found that the visible-light-driven photodegradation activities of ZnO/ZnFe₂O₄ nanocable arrays are superior to those of the ZnO nanowire arrays and ZnFe₂O₄ nanotube arrays using RhB as the probe molecules. All the three nanostructures show degradation of RhB molecules under visible light irradiation, but they take different degradation pathways. The degradation of RhB in the presence of ZnO nanowire arrays is attributed to the dye-sensitized mechanism, and the photodegradation activity is the worst. ZnO/ZnFe₂O₄ nanocable arrays and ZnFe₂O₄ nanotube arrays have the same degradation mechanism, that is, reactive radicals produced by photogenerated electron-hole pairs in the visible-light-active ZnFe₂O₄ are responsible for the photodegradation of RhB. However, the nanocable arrays show much higher degradation capability. This is owing to the type II band alignment between ZnO and ZnFe₂O₄, which greatly promotes the separation of photogenerated electronsand holes in ZnFe₂O₄.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Guo, Xuan = 準一維鋅-鐵-氧納米結構陣列 : 控制製備, 磁學性質以及光催化方面的應用 / 郭璇.
Thesis (Ph.D.) Chinese University of Hong Kong, 2013.
Includes bibliographical references (leaves 107-117).
Abstracts also in Chinese.
Guo, Xuan = Zhun yi wei xin-tie-yang na mi jie gou zhen lie : kong zhi zhi bei, ci xue xing zhi yi ji guang cui hua fang mian de ying yong / Guo Xuan.