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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Synthesis, Characterization, and Self-Assembly of Size Tunable Gold Nanorods

Park, Kyoungweon 20 November 2006 (has links)
The successful applications of nanoparticles require the ability to tune their properties by controlling size and shape at the nanoscale. In metal nanomaterial research, the optical properties have been of interest especially because of the applications to medical diagnostics and nanooptics. It is important to prepare nanoparticles of well-defined shape and size for properly characterizing the optical properties. We describe improved seed mediated synthesis of gold nanorods (GNRs) producing a high yield of NRs with low polydispersity and few byproducts. The efficient separation of GNRs from mixture of shapes is achieved by understanding the hydrodynamics of nanoparticles undergoing centrifugation. The optical properties of resulting refined GNRs are compared to predictions of existing theories, and the main parameters affecting them are discussed. GNRs with well defined aspect ratios are introduced into a polyvinyl alcohol matrix by means of solution-casting techniques. The film is drawn to induce the uniaxial alignment of GNRs to be used as color polarizing filters. We prepare GNR polarizing filter with different peak positions ranging from visible to near infra red by using different aspect ratio of NRs. To utilize GNRs to make nanoscale devices, spatial organization is required. We characterize the self-assembly of GNRs observed on a TEM grid. The drying process is accompanied by complex hydrodynamic and thermodynamic events, which create rich range of patterns observed. Being anisotropic in shape, the rods can form liquid crystal (LC) assemblies above a certain concentration. We observed LC phase of GNRs by resorting to an evaporation of aqueous NR solution. The convective flow caused by the solvent evaporation carries NRs from the bulk solution to solid-liquid-air interface, which makes the solution locally very concentrated driving the phase transition of NRs. We calculate the order parameter from various assemblies observed, and compare the observed phase behavior to the one expected on the basis of theory.
52

Design and fabrication of new 3D energy harvester with nano-ZnO rods

Li, Cheng-chi 21 August 2012 (has links)
This study presents a new way for new 3D energy harvesting energy with vertically aligned nanorods arrays. ZnO nanoparticles array on Au/Cr/Si substrate are directly patterned by electrospray. First, gel solutions with zinc acetate, monoethanolamine and 2-methoxyethanol as the precursor by sol-gel technology were formulated. Then, the solutions were stirred to become clear and homogeneous liquid. Second, the precursor solutions were prepared by electrospray, where a Taylor cone was formed to produce ZnO nanoparticles. Then the ZnO nanoparticles were annealed as seed layers for nanorods. By varying the property of the ZnO solution, needle with collector distance, applied voltage, annealing temperature and molar ratio were discussed. After annealing, the orientation of the ZnO nanorods depend on the crystalline orientation of ZnO nanoparticles. The ZnO nanorods were obtained at a temperature of 90 ¢XC by aqueous solution method. The experimental parameters of lengths, diameters, and pH level of the reaction medium of the Zno nanorod were observed and controlled. The physical structures of ZnO were characterized by X-ray diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM) analyses. The results show that the ZnO nanoparticles become more intensity with increasing in annealing temperature. The SEM analysis reveals that the ZnO nanorods have diameters about 100-400 nm and length about 200-1200 nm. Finally, Pt electrode atop as Schottky contacts were packed to fabricate nanogenerator with ZnO nanorods. Then the nanogenerator was driven by ultrasonic wave vibration. The wave drives the electrode up and down to vibrate the nanorods, and its voltage and current were also characterized. The measurement results show the maximum power is 0.004х10-8 W during the operation frequency of 42 kHz.
53

Sensitive And Quantitative Determination Of Cysteine By Surface Enhanced Raman Spectrometry Based On Their Induced Aggregates Of Gold And Silver Nanostructures

Yuksel, Recep 01 September 2011 (has links) (PDF)
ABSTRACT SENSITIVE AND QUANTITATIVE DETERMINATION OF CYSTEINE BY SURFACE ENHANCED RAMAN SPECTROMETRY BASED ON THEIR INDUCED AGGREGATES OF GOLD AND SILVER NANOSTRUCTURES Y&uuml / ksel, Recep M.Sc., Department of Chemistry Supervisor: Prof. Dr. M&uuml / rvet Volkan September 2011, 76 pages The synthesis of noble metal nanostructures are an active research area and controlling the shape and the size is a challenging task. In this study, nanostructures with different morphologies were prepared using wet chemical synthesis techniques in the aqueous solutions. Gold and silver nanospheres were produced by reducing and capping agent trisodium citrate. Gold nanorods were synthesized by chemical reduction of HAuCl4 by ascorbic acid in the presence of cetyltrimethylammonium bromide (CTAB), AgNO3, and gold nanoseeds (in 1.5 nm diameter) and gold silver core shell nanorods were prepared by addition of silver atoms on the surface of gold nanorods in the presence of CTAB. Parameters that were critical to obtain homogeneous nanostructures were optimized. The characterization of the nanoparticles was performed by UV-VIS spectrometry, High Resolution - Transition Electron Microscopy (HR-TEM), Field Emission - Scanning Electron Microscopy (FE-SEM) and Energy Dispersive X-ray Spectroscopy (EDX). Besides, their electromagnetic enhancement properties were demonstrated through SERS measurement of cysteine. Self-assembly or assisted assembly of nanorods or nanospheres into organized arrays allows the realization of their collective properties that arise from the coupling of the optical and electronic properties of the neighbouring individual nanoparticles. In this study cysteine molecule was used as a linker molecule. The controlled addition of cysteine into the gold nanorod solution resulted in their preferential binding to the two ends of the gold nanorods and the formation of gold nanochains. In the usage of gold nanospheres on the other hand, cooperative hydrogen bonding of the cysteine molecules, resulted in the formation of gold nanoclusters. The assembly formation was demonstrated by UV&ndash / vis spectrometry and FE-SEM. Cysteine is a thiol group containing amino acid and deficiency of cysteine results in serious health problems. Therefore, determination of cysteine is an important issue. Herein we report two strategies for the quantitative determination of micromolar concentrations of cysteine by exploiting the interplasmon coupling in Au nanoparticles. One of them is a recently published colorimetric method and the other is a novel SERS method.
54

Synthesis and Optical Properties of ZnO Nanostructures

Yang, Li-Li January 2008 (has links)
<p>One-dimensional ZnO nanostructures have great potential applications in the fields of optoelectronic and sensor devices. Therefore, it is really important to realize the controllable growth of one-dimensional ZnO nanostructures and investigate their properties. The main points for this thesis are not only to successfully realize the controllable growth of ZnO nonawires, nanorods and quantum dots (QDs), and also investigate the structure and optical properties in detail by the methods of scan electron microscope(SEM), transmission electron microscope(TEM), resonant Raman, photoluminescence(PL) and low-temperature time resolved PL spectrum.</p><p>to grown ZnO nanorod arrays (ZNAs) on Si substrates. Firstly, the effects of ZnO nanoparticles, pH value of chemical solution, angel θ between substrate and beaker bottom on the structures of the samples were symmetrically investigated and the optimized growth condition to grow ZNAs can be concluded as follows: seed layer of ZnO nanoparticles, pH=6 and <em>θ</em>=70°. On the basis of these, the diameter of ZNAs was well controlled from 150nm~40nm through adjusting the diameter and density of the ZnO nanoparticles pretreated on the Si substrates. The experimental results indicated that both diameter and density of ZnO nanoparticles on the substrates determined the diameter of ZNAs. But when the density is higher than the critical value of 2.3×10<sup>8</sup>cm<sup>-2</sup>, the density will become the dominant factor to determine the diameter of ZNAs.</p><p>One the other hand, the optical properties of ZNAs were investigated in detail. The Raman and photoluminescence (PL) results showed that after an annealing treatment around 500oC in air atmosphere, the crystal structure and optical properties became much better due to the decrease of surface defects. The resonant Raman measurements excited by 351.1nm not only revealed that the surface defects play a significant role in the as-grown sample, but also suggested that the strong intensity increase of some Raman scatterings was due to both outgoing resonant Raman scattering effect and deep level defects scattering contribution for ZnO nanorods annealed from 500°C to 700°C. It is the first time to the best of our knowledge that the Raman measurements can be used to monitor the change of surface defects and deep level defects in the CBD grown ZnO nanorods. We have also presented, for the first time, a time resolved PL study in CBD grown ZnO nanorods with different diameters. The results show that the decay time of the excitons in the nanorods strongly depends on the diameter of the nanorods. The altered decay time is mainly due to the surface recombination process. The effective time constant related to the surface recombination velocity was deduced. A thermal treatment under 500°C will suppress the surface recombination channel, resulting in an improvement of the optical quality for the ZnO nanorods.</p><p>This thesis not only provides the effective way to control the size of ZNAs, but also obtains some beneficial results in aspects of their optical properties, which builds theoretical and experimental foundation for much better and broader applications of one-dimensional ZnO nanostructures.</p>
55

Ground state depletion microscopy for imaging the interactions between gold nanoparticles and fluorescent molecules

Blythe, Karole Lynn 27 February 2013 (has links)
Ground state depletion with individual molecule return (GSDIM) super-resolution microscopy is used to interrogate the location of individual fluorescence bursts from two different nanoparticle-fluorophore systems. The first system consists of fluorophore-labeled DNA molecules on gold nanowire surfaces. In this system carboxytetramethyl rhodamine-labeled double-stranded DNA molecules were bound to the surface of gold nanowires via gold-thiol linkages. The second system focuses on mesoporous silica coated nanorods with dye embedded into the silica coating. The dye molecule, Rhodamine 6G, was incorporated into the silica shell during the nanorod coating procedure. Individual fluorescence bursts were spatially localized using point spread function fitting and used to reconstruct the image of the underlying nanowire or nanorod. / text
56

Band Edge Energetics and Charge Transfer Processes in Semiconductor-Metal Heterostructured Nanorods as Photocatalysts and Metal Oxide Electrode-Organic Semiconductor Interfaces in Organic Photovoltaics

Ehamparam, Ramanan January 2015 (has links)
Energetics, charge selectivity and interfacial charge transfer kinetics affect the efficiency of solar electric energy conversion and solar photochemical formation of fuels. The research described herein focuses on understanding and controlling the energetics, charge selectivity, and interfacial charge transfer processes in organic photovoltaics, as well as new generation semiconductor-semiconductor and metal-semiconductor heterostructured nanorods (NRs) as photocatalysts. Waveguide and transmission based spectroelectrochemistries, photoemission spectroscopies, and impedance spectroscopy were used to characterize the frontier orbital energies, charge selectivity and interfacial charge transfer kinetics in heterostructured NRs and organic photovoltaics. CdSe NRs tipped with Au nanoparticles and CdSe seeded CdS NRs tipped with Pt nanoparticles were used to study the effect of compositional asymmetry and catalytic sites on band edge energies of NRs. We used UV photoemission spectroscopy (UPS) and waveguide and transmission-based spectroelectrochemistry of NR monolayers/multilayers on conductive substrates to estimate valence/conduction band energies. Potential-modulated attenuated total reflectance (PM-ATR) spectroscopy was utilized to measure the apparent heterogeneous rate constants of reversible electron injection into NR films on indium tin oxide (ITO). We conclude from these measurements that metal tipping, which is designed to enhance the photocatalytic activity of semiconductor NRs, altered band edge energies and enhanced electronic coupling to conductive substrates, in ways that are predicted to influence their efficiency as photoelectrocatalysts. Monolayers of functionalized phosphonic acid ruthenium phthalocyanines (RuPcPA) tethered to ITO as a model organic photovoltaic donor/electrode interface were studied to understand the aggregation and orientation dependent charge transfer kinetics and energetics of these systems. The effect of surface roughness on the orientation of RuPcPA was theoretically modeled and compared to the experimental results. Electrochemical and spectroelectrochemical studies revealed the presence of only monomeric species on ITO. Impedance spectroscopy (IS) and PM-ATR were used to measure charge transfer rate constants. Further, frontier orbital energies of RuPcPA modified ITO were measured using UPS, and the results indicated favorable energetics for hole collection at the RuPcPA/ITO interface for OPV applications. The effect of "UV-light soaking" on the performance of organic photovoltaic devices employing metal oxide (MO) electron selective interlayers (ESL) was addressed using sputtered zinc oxide (ZnO) ESL films. This study provides a coherent methodology for differentiating between the proposed origins of the s-shaped current-voltage (J-V) responses in the literature for organic photovoltaics using MO ESLs. We use IS and UPS to demonstrate that the energetic barrier for charge extraction at the ZnO/active layer interface leads to the observed s-shape response in OPVs using ZnO ESLs. Furthermore, this study provides clear guidelines for minimizing the s-shaped J-V response and the effect of UV light on the performances of OPV devices using ZnO ESLs. We have developed solution electrochemical protocols to characterize nanometer-scale porosity and electronic properties of both solution-deposited and sputtered ZnO thin films used as interlayers for electron-harvesting contacts in inverted organic solar cells on ITO substrates. These electrochemical experiments were performed in order to evaluate the hole-blocking abilities of these ZnO ESLs as well as their effective "pinhole density," thus demonstrating a strong correlation to their OPV performances. These electrochemical experiments can be used to characterize and optimize ESLs rapidly, before OPV device fabrication.
57

Von Gold Plasmonen und Exzitonen : Synthese, Charakterisierung und Applikationen von Gold Nanopartikeln / Of gold plasmons and excitons : synthesis, characterization and applications of gold nanoparticles

Bomm, Jana January 2012 (has links)
In dieser Arbeit wurden sphärische Gold Nanopartikel (NP) mit einem Durchmesser größer ~ 2 nm, Gold Quantenpunkte (QDs) mit einem Durchmesser kleiner ~ 2 nm sowie Gold Nanostäbchen (NRs) unterschiedlicher Länge hergestellt und optisch charakterisiert. Zudem wurden zwei neue Synthesevarianten für die Herstellung thermosensitiver Gold QDs entwickelt werden. Sphärische Gold NP zeigen eine Plasmonenbande bei ~ 520 nm, die auf die kollektive Oszillation von Elektronen zurückzuführen ist. Gold NRs weisen aufgrund ihrer anisotropen Form zwei Plasmonenbanden auf, eine transversale Plasmonenbande bei ~ 520 nm und eine longitudinale Plasmonenbande, die vom Länge-zu-Durchmesser-Verhältnis der Gold NRs abhängig ist. Gold QDs besitzen keine Plasmonenbande, da ihre Elektronen Quantenbeschränkungen unterliegen. Gold QDs zeigen jedoch aufgrund diskreter Energieniveaus und einer Bandlücke Photolumineszenz (PL). Die synthetisierten Gold QDs besitzen eine Breitbandlumineszenz im Bereich von ~ 500-800 nm, wobei die Lumineszenz-eigenschaften (Emissionspeak, Quantenausbeute, Lebenszeiten) stark von den Herstellungs-bedingungen und den Oberflächenliganden abhängen. Die PL in Gold QDs ist ein sehr komplexes Phänomen und rührt vermutlich von Singulett- und Triplett-Zuständen her. Gold NRs und Gold QDs konnten in verschiedene Polymere wie bspw. Cellulosetriacetat eingearbeitet werden. Polymernanokomposite mit Gold NRs wurden erstmals unter definierten Bedingungen mechanisch gezogen, um Filme mit optisch anisotropen (richtungsabhängigen) Eigenschaften zu erhalten. Zudem wurde das Temperaturverhalten von Gold NRs und Gold QDs untersucht. Es konnte gezeigt werden, dass eine lokale Variation der Größe und Form von Gold NRs in Polymernanokompositen durch Temperaturerhöhung auf 225-250 °C erzielt werden kann. Es zeigte sich, dass die PL der Gold QDs stark temperaturabhängig ist, wodurch die PL QY der Proben beim Abkühlen (-7 °C) auf knapp 30 % verdoppelt und beim Erhitzen auf 70 °C nahezu vollständig gelöscht werden konnte. Es konnte demonstriert werden, dass die Länge der Alkylkette des Oberflächenliganden einen Einfluss auf die Temperaturstabilität der Gold QDs hat. Zudem wurden verschiedene neuartige und optisch anisotrope Sicherheitslabels mit Gold NRs sowie thermosensitive Sicherheitslabel mit Gold QDs entwickelt. Ebenso scheinen Gold NRs und QDs für die und die Optoelektronik (bspw. Datenspeicherung) und die Medizin (bspw. Krebsdiagnostik bzw. -therapie) von großem Interesse zu sein. / In this thesis, the synthesis and optical characterization of spherical gold nanoparticles (NP) with diameters larger than ~ 2 nm, gold quantum dots (QDs) with diameters smaller than ~ 2 nm and gold nanorods (NRs) with different lengths are presented. In addition, a novel one-pot synthesis for the preparation of thermosensitive gold QDs is introduced. Gold NP solutions appear red colored due to their strong absorption in the visible range at ~ 520 nm. This absorption band is a result of surface plasmon resonance, which is caused by the coherent oscillation of conduction band electrons induced by an electromagnetic field. In contrast to spherical gold NPs, gold NRs show two surface plasmon bands due to their anisotropic shape, a transverse plasmon band at ~ 520 nm and a longitudinal plasmon band depending on the aspect ratio (length-to-width-ratio) of the gold NRs. If the size of the gold NPs decreases to values below ~ 2 nm, quantum-size confinement occurs and the surface plasmon band disappears. Additionally, the overlap between conduction band and valence band disappears, discrete electronic levels arise and a band gap is created. As a consequence of quantum confinement, the gold QDs show photoluminescence (PL) upon UV-irradiation. The gold QDs synthesized via the one-pot synthesis exhibit a broadband luminescence between 500 nm and 800 nm. The luminescence properties (emission peak, quantum yield, lifetime) strongly depend on the synthetic parameters like reaction temperature, stoichiometry and the surface ligand. Gold NRs and gold QDs were incoroporated into different polymers (e.g. cellulose triacetate). Polymer nanocomposite films showing optical anisotropy are obtainded by stretching polymer films containing gold NRs uniaxial in a tensile test machine. In addition to the optical characterization of gold NRs and QDs, their thermal behavior in solution as well as in different nanocomposites is studied. A shortening of the gold NRs or a transformation into spherical gold NP is observed, if the polymer nanocomposites containing gold NRs are heated above a temperature of 200 °C. The PL of the synthesized gold QDs strongly depends on the ambient temperature. An increase of PL quantum yield (QY) and PL lifetime occur, if the solutions are cooled. The best PL QY of 16.6 % was observed for octadecyl mercaptan capped gold QDs at room temperature, which could be improved to 28.6 % when cooling the solutions to -7 °C. Furthermore, optically anisotropic security labels containing gold NRs and thermosensitive security devices containing gold QDs are developed. Due to their unique optical properties, gold NRs and QDs are interesting candidates for optoelectronical as well as data storage devices and medical applications like biomedical imaging or cancer therapy.
58

Hibridinių nanodarinių formavimas ir tyrimas / Formation and investigation of hybryd nanostructures

Treideris, Marius 02 November 2011 (has links)
Pastarąjį dešimtmetį, intensyviai vystantis nanotechnologijoms, ženkliai išaugo technologinių metodų, įgalinančių suformuoti darinius, kuriuose elementų dydžiai būtų tarp 1 ir 100 nm, paieška. Šiai specifinei nanostruktūrinių medžiagų grupei skiriamas ypatingas dėmesys dėl naujų fizikinių reiškinių ir ypač - praktinių taikymų, kuriuos atveria šie dariniai. Šiame darbe aptariamos elektrocheminės technologijos, skirtos kontroliuojamos morfologijos porėtojo silicio formavimui. Suformuoti hibridiniai por-Si dariniai su metalais. Sukurta biomolekulių įterpimo į porėtuosius silicio darinius technologija bei tirta biomolekulių sąveika su kietakūniais padėklais. Nagrinėjami GaP nanodarinių formavimo elektrocheminio ėsdinimo būdu dėsningumai bei jų taikymo galimybės dujų sensoriuose. Įsisavinta nanoporėtųjų dielektrinių terpių ir hibridinių nanodarinių formavimo technologija bei tirtos jų savybės. / Over the past decade, the intensive development of nanotechnology was made to increase significantly the number of methods to form the structures of a size between 1 and 100 nm. It should be emphasized that nanostructured materials are interesting both because of perspectives in practical applications and new physical phenomena. In this work the electrochemical technique for the control of morphology of porous silicon matrix developed. Hybrid por-Si structures with metals were made. The method for infiltration of biomolecules into the porous silicon structures was developed and the interaction between silicon and bio-molecules was investigated. GaP nanostructures were formed by electrochemical etching and the possibilities of their application for gas sensors were estimated. Nanoporous and Fe-doped silica films on Si were made and the developed structures were characterized by their structural, optical or magnetic properties.
59

Formation and investigation of hybryd nanostructures / Hibridinių nanodarinių formavimas ir tyrimas

Treideris, Marius 02 November 2011 (has links)
Over the past decade, the intensive development of nanotechnology was made to increase significantly the number of methods to form the structures of a size between 1 and 100 nm. It should be emphasized that nanostructured materials are interesting both because of perspectives in practical applications and new physical phenomena. In this work the electrochemical technique for the control of morphology of porous silicon matrix developed. Hybrid por-Si structures with metals were made. The method for infiltration of biomolecules into the porous silicon structures was developed and the interaction between silicon and bio-molecules was investigated. GaP nanostructures were formed by electrochemical etching and the possibilities of their application for gas sensors were estimated. Nanoporous and Fe-doped silica films on Si were made and the developed structures were characterized by their structural, optical or magnetic properties. / Pastarąjį dešimtmetį, intensyviai vystantis nanotechnologijoms, ženkliai išaugo technologinių metodų, įgalinančių suformuoti darinius, kuriuose elementų dydžiai būtų tarp 1 ir 100 nm, paieška. Šiai specifinei nanostruktūrinių medžiagų grupei skiriamas ypatingas dėmesys dėl naujų fizikinių reiškinių ir ypač - praktinių taikymų, kuriuos atveria šie dariniai. Šiame darbe aptariamos elektrocheminės technologijos, skirtos kontroliuojamos morfologijos porėtojo silicio formavimui. Suformuoti hibridiniai por-Si dariniai su metalais. Sukurta biomolekulių įterpimo į porėtuosius silicio darinius technologija bei tirta biomolekulių sąveika su kietakūniais padėklais. Nagrinėjami GaP nanodarinių formavimo elektrocheminio ėsdinimo būdu dėsningumai bei jų taikymo galimybės dujų sensoriuose. Įsisavinta nanoporėtųjų dielektrinių terpių ir hibridinių nanodarinių formavimo technologija bei tirtos jų savybės.
60

Mechanical Characterization and Electrochemical Sensor Applications of Zinc Oxide Nanostructures

Fulati, Alimujiang January 2010 (has links)
Nanotechnology is emerging to be one of the most important scientific disciplines that physics, chemistry and biology truly overlap with each other. Over the last two decades science and technology have witnessed tremendous improvement in the hope of unveiling the true secrets of the nature in molecular or atomic level. Today, the regime of nanometer is truly reached. ZnO is a promising material due to the wide direct band gap (3.37 eV) and the room temperature large exciton binding energy (60 meV). Recent studies have shown considerable attraction towards ZnO nanostructures, particularly on one-dimensional ZnO nanorods, nanowires, and nanotubes due to the fact that, for a large number of applications, shape and size of the ZnO nanostructures play a vital role for the performance of the devices. The noncentrosymmetric property of ZnO makes it an ideal piezoelectric material for nanomechanical devices. Thus, mechanical characterization of one dimensional ZnO nanostructures including strength, toughness, stiffness, hardness, and adhesion to the substrate is very important for the reliability and efficient operation of piezoelectric ZnO nanodevices. Moreover, owing to the large effective surface area with high surface-to-volume ratio, the surface of one dimensional ZnO nanowires, nanorods, and nanotubes is very sensitive to the changes in surface chemistry and hence can be utilized to fabricate highly sensitive ZnO electrochemical sensors. This thesis studies mechanical properties and electrochemical sensor applications of ZnO nanostructures. The first part of the thesis deals with mechanical characterization of vertically grown ZnO nanorods and nanotubes including buckling, mechanical instability, and bending flexibility. In paper I, we have investigated mechanical instability and buckling characterization of vertically aligned single-crystal ZnO nanorods grown on Si, SiC, and sapphire substrates by vapor-liquid-solid (VLS) method. The critical loads for the ZnO nanorods grown on Si, SiC, and sapphire were measured and the corresponding buckling and adhesion energies were calculated. It was found that the nanorods grown on SiC substrate have less residual stresses and are more stable than the nanorods grown on Si and sapphire substrates. Paper II investigates nanomechanical tests of bending flexibility, kinking, and buckling failure characterization of vertically aligned single crystal ZnO nanorods/nanowires grown by VLS and aqueous chemical growth (ACG) methods. We observed that the loading and unloading behaviors during the bending test of the as-grown samples were highly symmetrical and the highest point on the bending curves and the first inflection and critical point were very close. The results also show that the elasticity of the ZnO single crystal is approximately linear up to the first inflection point and is independent of the growth method. In Paper III, we quantitatively investigated the buckling and the elastic stability of vertically well aligned ZnO nanorods and ZnO nanotubes grown on Si substrate by nanoindentation technique. We found that the critical load for the nanorods was five times larger than the critical load for nanotubes. On the contrary, the flexibility for nanotubes was five times larger than nanorods. The discovery of high flexibility for nanotubes and high elasticity for nanorods can be utilized for designing efficient piezoelectric nanodevices. The second part of this thesis investigates electrochemical sensor applications of ZnO nanorods, nanotubes , and nanoporous material. In paper IV, we utilized functionalized ZnO nanorods on the tip of a borosilicate glass capillary coated with ionophore-membrane to construct intracellular Ca2+ selective sensor. The sensor exhibited a Ca2+-dependent electrochemical potential difference and the response was linear over a large dynamic concentration range, which enabled this sensor to measure Ca2+ concentrations in human adipocytes or in frog oocytes. The results were consistent with the values of Ca2+ concentrations reported in the literature. In paper V, ZnO nanotubes and nanorods were used to create pH sensor devices. The developed ZnO pH sensors display good reproducibility, repeatability, and long-term stability. The ZnO pH sensors exhibited a pH-dependent electrochemical potential difference over a large dynamic pH range. We found that the ZnO nanotubes provide sensitivity as high as twice that of the ZnO nanorods. The possible reasons of enhanced sensitivity were explained. Paper VI investigates an improved potentiometric intracellular glucose biosensor based on the immobilization of glucose oxidase on the ZnO nanoporous material. We demonstrated that using ZnO nanoporous material as a matrix material for enzyme immobilization improves the sensitivity of the biosensor as compared to using ZnO nanorods. In addition, the fabrication method of the intracellular biosensor was simple and excellent performance in sensitivity, stability, selectivity, reproducibility, and anti-interference was achieved.

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