Nanoparticles have generated much excitement as a result of their often unique properties, inherently dependent on nanoparticle material, shape and size. Virtually all conceivable nanoparticle applications will require excellent control over how nanoparticles are assembled and linked to other components. When several nanoparticles are brought together, the assembly structure is crucial in determining their newly emergent properties. However, the synthetic chemistry techniques required to control nanoparticle functionalisation and assembly are still under-developed, with complex biological or supramolecular systems being the current best approaches. There remains a need for simple, generalisable strategies for molecular-level control over nanoparticle functionalisation and assembly. This thesis presents the development of a toolkit of nanoparticle building blocks, which may be assembled in a predictable and controlled way, governed by simple and easily optimised abiotic molecular systems. Efficient, size-controlled, direct synthesis of functionalised gold nanoparticle building blocks with control over size and dispersity is developed. ¹⁹F NMR spectroscopy studies provide a fundamental understanding of the implications of confinement at the nanoparticle surface for molecular reactivity. Two self-assembly strategies, each resulting in structures of high order and predictability, are presented. First, the reversible nature of dynamic covalent boronic ester formation is exploited to induce reversible nanoparticle self-assembly. Links between molecular details and resulting morphology are demonstrated and rationalised. A second strategy exploits multivalent non-covalent interactions, resulting in ‘planet–satellite' structures displaying high order, stability and predictability. This thesis demonstrates that relatively simple molecular systems present a viable, and ultimately more flexible, alternative to existing methods of directing precise, predictable control of nanoparticle functionalisation and assembly. Advancing a molecular-level understanding of the underlying processes enables a high level of control. Future application of this molecular approach to dynamic nanomaterial control will lead to more complex and sophisticated nanostructures, helping nanotechnology progress towards its undoubtedly revolutionary full potential.

University of Macau / Institute of Chinese Medical Sciences

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No description available.

Thesis (Ph.D.)--University of Delaware, 2007. / Principal faculty advisor: Ismat S. Shah, Dept. of Materials Science. Includes bibliographical references.

Using a variety of techniques including femtosecond transient absorption spectroscopy, optical absorption, atomic force microscopy, the hot electron cooling dynamics of lithographically prepared gold nanoarrays, the effect of the surrounding environment, and the phonon oscillations of gold and silver nano-arrays were investigated. The cooling dynamics of gold nanoarrays on a glass substrate were found to be different from those of either colloidal nanodots in colloidal solution or films on glass substrate. The electron-phonon component of the electronic relaxation in the arrays was found to be longer than that in the dots or the films. The spatially isolated nanoarray particles experience a significantly different environment than the gold nanodots in solution, thus the long phonon-phonon component resulting from the coupling of particles to the medium, is not observed. The catalytic effectiveness of platinum nanoparticles for the hydrogenation of propene was investigated. The system with platinum particles was found to have a slightly lower activation energy than other systems in the literature. The effect of encapsulating the platinum particles in alumina was also investigated and it was found that the activation energy for the reaction was even lower. The effect of adding platinum, palladium, and rhodium particles to the proton exchange membrane of polymer electrolyte fuel cells, on the output power of the cells was also investigated. The effects of pH and precursor salt concentration, and particle composition were also investigated.

A new fabrication process of organic and inorganic nanoparticles and cups by electrospraying blended polymer-sol-gel solutions followed by calcination has been investigated. Because of low viscosity and high surface tension of blended polymersol- gel solutions, an electrostatically extruded continuous liquid jet from the spray source became tiny droplets with diameter of less than 1µm in transit. They were collected as dried formats at the counter electrode. These are then calcinated to eliminate polymers as well as cross-link sol-gel material. Silica nanocups have been fabricated using the above technique and the probable methods to control their morphology by varying the ionic concentration have been investigated. Experiments with biodegradable polymers, like Poly Lactic Acid (PLA) and polyvinylpyrrolidine (PVP) to fabricate nanoparticles using the above technique, have also been carried out. The potential use of such biodegradable particles in drug delivery has been demonstrated. This method can encapsulate drug in the particles without the need of any stabilizer which can cause unwanted effect on the drug. The effect of solvents, polymer concentration and deposition distance on morphology and diameter of particles was also investigated on PLA particles. This process is a simple and efficient approach for producing nanocomposite cups that cannot be made by an aggregation method and also nano/micro particles which may find their use in drug delivery and filtration media. Finally, a new technique to sort the particles based on their dimensions is demonstrated. Because of interactions between charged droplets and a non-linear electrostatic field, nanoparticles with different dimensions are deposited at different locations. By using this principle, silica nanocups have been sorted into three groups with mean diameters of 0.31 µm, 0.7 µm and 1.1µm and a standard deviation of 20%.

Includes bibliographical references (p. 154-160).

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.