The development of electronics has been growing at a fast rate in recent years. More and more ideas have been searched and are increasing at a faster rate. However, there is more detail work in the nanolevel or nanostructure yet to be understood. Thus, more and more semiconductor physicists have move to the new field of study in nanostructures. Nanostructures are the future of electronic devices. By understanding nanostructure electronic devices, electronics is the key for the progress of any modern equipment and advancement. This comes about when electronic transport of a nanostructure is thoroughly understood. Thus, future electronic devices can utilize the development of conductance through components having dimensions on the nanometer scale.The objective of the proposed research project is to study electronic transport in a ring with an infinite potential barrier at the center and a modulated external potential in one of the arms. The relative phase between the two paths in this structure can be controlled by applying electrostatic potential in one of the arms. One can compare these types of systems with optical interferometers, where the phase difference between the two arms is controlled by changing the refractive index of one arm through the electro-optic effect. By modulating the potential in one arm of the ring, we will study the interference effect on conductance. The method of finding the conductance of a nanostructure will be using the recursive Green's function method. This includes finding transverse eigenvalues, eigenfunctions, and hopping integrals to determine Green's propagators. A FORTRAN 77 computer program is used for numerical calculations.These remarkable ultra-small and ultra-clean quantum systems are currently achieved due to significant technological advancement in fabrication. For ultra-small quantum devices, the theoretical understanding of device performance must be based on quantum carrier transport of confined electrons and holes in the channel. This theoretical research will lead to the understanding of the effects of geometry and impurities on transport of the carriers in the nanochannels. / Department of Physics and Astronomy

The synthesis, structure and physical properties of a series of Mnx(Co, Mg)₁ˍxFe₂O₄, (Mg, Sr)₀.₂ Mn₀.₁Co₀.₇Fe₂O₄ and Mg₀.₅Mn₀.₅(RE)₀.₁Fe₁.₉O₄ (where RE are rare earth elements) nanoferrites have been studied. These compounds were synthesized at low reaction temperature of about 200 ⁰C using the glycol-thermal method. The starting materials were high-purity metal chlorides or nitrates which were precipitated by NH₄OH and KOH respectively. In addition, MnxCo₁₋xFe₂O₄ (x = 0, 0.5 and 1) samples were produced directly from high-purity metal oxides by high-energy ball milling technique. Single-phase cubic spinel structure and nanoparticle structure of the synthesized samples were confirmed by X-ray diffraction (XRD) and transmission electron microscope (TEM). The results show that the produced powders of the asprepared samples have average grain sizes ranging from 7 to 16 nm. Filtering the precipitates by Whatman glass microfiber filters (GF/F) appears to be important in obtaining the small particle sizes. We suspect higher stability of the MnxCo₁₋xFe₂O₄ at x = 0 and 0.5 where complete symmetry in the proportion of the atoms on tetrahedral (A) and octahedral (B) sites would tend to favour larger nanoparticles. The evolutions of the magnetic properties as a function of composition, annealing temperature under air and argon atmospheres or measuring temperature have been investigated by ⁵⁷Fe Mössbauer spectroscopy, vibration sample magnetometer (VSM) and superconducting quantum interference device (SQUID). Significant changes in magnetic properties are observed across the composition ranges studied. The Mössbauer spectra indicate ferrimagnetic, superparamagnetic and paramagnetic behaviours of the compounds. The results show evidence of transformation from single-domain to multi-domain structure with thermal annealing in our samples. Temperature dependence of magnetization shows differences between field cooling (FC) and zero field cooling (ZFC) which we attribute to spin-freezing and thermal relaxation for typical nanoparticles. Significant increase in coercive field with reduction in measuring temperature is obtained in Co- based compounds. Mn₀.₅Co₀.₅Fe₂O₄, Sr₀.₂Mn₀.₁Co₀.₇Fe₂O₄ and Mg₀.₂Mn₀.₁Co₀.₇Fe₂O₄ have large coercive fields of 1.45, 3.02 and 10.70 kOe at 4 K compared to 0.17, 0.05 and 0.05 kOe at room temperature respectively. Variation of coercive fields (Hc) with measuri ing temperature for MnxCo₁₋xFe₂O₄ (x = 0.1 and 0.05), (Mg, Sr)₀.₂Mn₀.₁Co₀.₇Fe₂O₄ nanoferrites follow the Kneller's law for uniaxial non-interacting single domain particles of the form Hc(T) = Hc(0)[1-( T/Tβ)α]. The observed temperature dependences are consistent with α = 1/2. We also find evidence of the departure from this law at lower temperature. The temperature dependence of the saturation magnetizations were observed to vary with temperature according to the modified Bloch's law Ms(T) = Ms(0)[1 - ( T/T₀)ᵝ] where β is at least 1.5. This is attributed to the confinement effects of the spin-wave spectrum for magnetic clusters. The equation appears to fit the saturation magnetization data over the entire temperature range with values of β from 2.1 to 2.4 for the samples studied. These results are consistent with the nanoparticle nature of the compounds. In Mg₀.₅Mn₀.₅(RE)₀.₁Fe₁.₉O₄ nanoferrites, the grain sizes, lattice parameters and saturation magnetizations increase with RE substitution which we attribute to larger RE ions substituting smaller Fe ions. The results show evidence of superparamagnetic behaviour of the nanoparticles. The highest grain size and magnetizations are obtained for the Gd substituted sample. We find strong correlation between the saturation magnetizations, grain sizes and microstrains with de Gennes factor G. The correlation with grain sizes and microstrains appear to be unique and characteristic of the nanoparticle nature of the compounds. Bulk samples in the form of pellets were also produced from the as-prepared samples of MnxCo₁₋xFe₂O₄ for resistivity measurements. The temperature dependence of the electrical resistivity for samples sintered from 600 - 1100 ⁰C under argon atmosphere were studied using the four-probe method from room temperature to about 110 ⁰C. Two possible mechanisms for resistivity involving Tˉ¹ and Tˉ¹/² dependences were investigated which we associated with semiconducting and inter-grain conductivity respectively. The Tˉ¹/² dependence is found to fit the data better and predicts higher activation energies. The resistivity was observed to be sensitive to the surface of the pellet being probed and the annealing temperature. / Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2012.

A novel way of producing nanostructures in the past decade has been through the use of an anodized alumina template. This template has dense, self-ordered nanometric pores that grow in the oxide as the aluminum is being anodized. This technique is a fairly new method of processing nanostructures, and much study and research is presently being done to understand the formation mechanisms of the highly ordered pores. Ultra-pure aluminum foil and pure aluminium single crystal plates were anodized to create porous anodized alumina, and using it as a template to electro-deposit Nickel nanostructures. The effects different anodizing parameters have on oxide creation were studied, and the results obtained from studying the effects of substrate purity and texture of the anodized aluminum substrate on the morphology of the alumina template, through the use of X-ray diffraction and scanning electron microscopy. / Nickel nanowires were prepared by DC electrodeposition inside the porous alumina template with a gold-palladium coating serving a conductive base. The nanowires have a diameter of 65 nm, and their length depends on the deposition time. The nanowires can uphold a position perpendicular to the substrate by partially dissolving the alumina template. They also have a tendency to gather together once the template is partially removed.

A very interesting class of nanoparticles extensively used for bio-applications is that of hydrogel particles, also called nanogels. There is an increasing interest in the design of hydrogel nanoparticles that have biofunctionality for applications in cell targeting, drug delivery, and biomedicine. The dissertation focuses on developing synthetic strategies for making diverse hydrogel nanoparticles customized to have desirable properties for various bio-applications. We have also investigated the potential of such nanoparticles as coatings for biomedical implants. Chapter 1 gives a brief introduction to hydrogel nanoparticles and the properties that make them attractive for various applications. The details of the syntheses of well defined, stable nanoparticles, commonly used in literature, are described in Chapter 2. Chapter 3 describes our synthesis of hollow sub-50 nm nanogels, which are otherwise difficult to synthesize based on the strategy discussed in Chapter 2. Chapter 4 also demonstrates how simple strategies borrowed from organic chemistry help in producing nanogels with multiple functionalities that are otherwise difficult to obtain, which also is an important advance over the synthetic methods discussed in Chapter 2. Chapter 5 describes how a general strategy based on photoaffinity labeling can yield materials with many applications ranging from optical materials, drug delivery, to biosensing. The latter part of the dissertation describes applications of various nanogels in biology especially as coatings that can control inflammation caused by biomaterials. Chapter 6 describes a method to functionalize flexible biomaterials with the nanogels, thus enabling in vivo investigations of the nanogels as potential coatings for controlling inflammation. Chapter 7 describes the biological studies performed (in collaboration with Garcia Group in the School of Mechanical Engineering at Georgia Tech) on various nanogels, aimed towards obtaining the most functional and efficient materials for implant applications. Chapter 8 describes application of hollow nanogels for covalently immobilizing biomolecules. This chapter also demonstrates how simple non-functional materials can be made unique and functional by means of traditional organic reactions. Finally, in order to broaden the applications of nanogel based materials.

<p>The main aim of this study was to develop a novel strategy for harnessing the properties of electroconductive polymers in sensor technology by using polymeric nanostructured blends in the preparation of high performance sensor devices.</p>

This study focuses on the effect of different experimental conditions including conventional hydrothermal synthesis and supercritical carbon dioxide (SCCO2) methods on materials characteristics in terms of particle morphology and pore geometry. Three types of mesoporous silicas were investigated by different synthesis methods, that is, MCM- 41, SBA-15 and -16. These materials were used as a target molecule due to its high volatility and strong antimicrobial characteristics. / Thesis (PhDAppliedScience)--University of South Australia, 2008.

Thesis (M.S.)--Missouri University of Science and Technology, 2008. / Degree granted by Missouri University of Science and Technology, formerly known as University of Missouri--Rolla. Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 2, 2008) Includes bibliographical references.

Thesis (M.S.)--University of Nevada, Reno, 2006. / "August, 2006." Includes bibliographical references (leaves 69-71). Online version available on the World Wide Web.

Thesis (Ph. D.)--University of North Texas, Aug., 2007. / Title from title page display. Includes bibliographical references.

Thesis (M.S.)--University of Alabama at Birmingham, 2008. / Description based on contents viewed Feb. 5, 2008; title from title screen. Includes bibliographical references (p. 65-68).