Graduation date: 1978

Sob o olhar nanotecnológico, a dimensionalidade passa a ser um fator preponderante nas propriedades dos materiais. O ouro metálico com dimensões reduzidas para a escala nanométrica passa a exibir um comportamento peculiar em termos de sua estrutura eletrônica e reatividade. No trabalho realizado busca-se um melhor entendimento das propriedades das nanopartículas de ouro através de um abordagem química, com foco nas interações superficiais e suas correlações com fenômenos de agregação. No campo mais fundamental, foram realizados estudos visando entender a influência de ligantes de diferentes comprimentos de cadeia nos processos de agregação e de fusão de nanopartículas, utilizando-se para tal ligantes de interesse para a química supramolecular: pirazina, 4,4\'-bipiridina, 1,2-bis (4-piridil)etano e 1,4-bis[(4-piridil)etenil]benzeno. Além disso, foram realizados estudos que permitiram a obtenção de nanopartículas de ouro passivadas com o complexo [Fe(CN)5(4-pySH)]3-,gerando um bloco de contrução interessante para a geração de materiais nanoestruturados a partir de ligações do tipo azul da Prússia. Por fim, estudos da interação de nanopartículas de ouro como o suporte inorgânico hidrotalcita foram realizados, possibilitando a geração de um material colorido composto de nanopartículas de ouro suportadas na superfície da matriz inorgânica. O material exibe ainda efeitos de mudança de coloração com o aumento da temperatura, correlacionados com o estado de agregação das nanopartículas metálicas. / Under the nanotechnological point of view, the dimensionality comes into play when one is dealing with many properties from the materials. Bulk gold with dimensions reduced to the nanometric scale shows singular reactivity and electronic properties. In the present work a further knowledge of the gold nanoparticles properties is sought from a chemical approach, through the investigation of surface interactions and their correlations with aggregation phenomena. Studies aiming a further understanding on the influence of different length ligands in the aggregation and fusional processes were performed with the ligands: pyrazine, 4,4\'-bipyridine, 1,2-bis(4-pyridyl)ethane and 1,4-bis[(4- pyridyl)ethenyl]benzene. Furthermore, the investigation of nanoparticles surface interaction with the ligands 2 and 4-mercaptopyridine and their complexes with pentacianoferrate was also investigated allowing the obtainment of building block potentially useful for the generation of nanostructured materials through Prussian blue-like bonds. Finally, the obtainment of a new material based on surface interactions of gold nanoparticles on the inorganic support hydrotalcite was possible. The material exhibits peculiar thermochromic properties with colors dependent on the aggregation state of the nanoparticles.

Sob o olhar nanotecnológico, a dimensionalidade passa a ser um fator preponderante nas propriedades dos materiais. O ouro metálico com dimensões reduzidas para a escala nanométrica passa a exibir um comportamento peculiar em termos de sua estrutura eletrônica e reatividade. No trabalho realizado busca-se um melhor entendimento das propriedades das nanopartículas de ouro através de um abordagem química, com foco nas interações superficiais e suas correlações com fenômenos de agregação. No campo mais fundamental, foram realizados estudos visando entender a influência de ligantes de diferentes comprimentos de cadeia nos processos de agregação e de fusão de nanopartículas, utilizando-se para tal ligantes de interesse para a química supramolecular: pirazina, 4,4\'-bipiridina, 1,2-bis (4-piridil)etano e 1,4-bis[(4-piridil)etenil]benzeno. Além disso, foram realizados estudos que permitiram a obtenção de nanopartículas de ouro passivadas com o complexo [Fe(CN)5(4-pySH)]3-,gerando um bloco de contrução interessante para a geração de materiais nanoestruturados a partir de ligações do tipo azul da Prússia. Por fim, estudos da interação de nanopartículas de ouro como o suporte inorgânico hidrotalcita foram realizados, possibilitando a geração de um material colorido composto de nanopartículas de ouro suportadas na superfície da matriz inorgânica. O material exibe ainda efeitos de mudança de coloração com o aumento da temperatura, correlacionados com o estado de agregação das nanopartículas metálicas. / Under the nanotechnological point of view, the dimensionality comes into play when one is dealing with many properties from the materials. Bulk gold with dimensions reduced to the nanometric scale shows singular reactivity and electronic properties. In the present work a further knowledge of the gold nanoparticles properties is sought from a chemical approach, through the investigation of surface interactions and their correlations with aggregation phenomena. Studies aiming a further understanding on the influence of different length ligands in the aggregation and fusional processes were performed with the ligands: pyrazine, 4,4\'-bipyridine, 1,2-bis(4-pyridyl)ethane and 1,4-bis[(4- pyridyl)ethenyl]benzene. Furthermore, the investigation of nanoparticles surface interaction with the ligands 2 and 4-mercaptopyridine and their complexes with pentacianoferrate was also investigated allowing the obtainment of building block potentially useful for the generation of nanostructured materials through Prussian blue-like bonds. Finally, the obtainment of a new material based on surface interactions of gold nanoparticles on the inorganic support hydrotalcite was possible. The material exhibits peculiar thermochromic properties with colors dependent on the aggregation state of the nanoparticles.

The entire sixteen element scattering matrix for two parallel dielectric fibers over an angular range of θ = 5°-170° as measured from the forward θ = 0 direction has been experimentally measured using the polarization modulation technique. Experimental results were in good agreement with theory for light scattering from two parallel fibers. Measurements were made for both endside and broadside illuminations at normal incidence for fibers at various separations from 2 μm to 70 μm. Laser wavelengths used were 632.8 nm and 441.2 nm, and fiber radii were 0.400±0.002 μm, 0.370±0.002 μm, 0.428±0.002 μm, and 0.406±0.002 μm. Special care was taken to measure the fiber radii, fiber separation, and to establish the parallelism between the two fibers. Electrostatic attraction between the fibers prevented the investigation for separation below 2 μm. A vibration detection device based on two-fiber light scattering has also been suggested.

No description available.

by Lee Hon Shing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 105-106). / Text in English; abstracts in English and Chinese. / by Lee Hon Shing. / Acknowledgements --- p.i / Abstract --- p.ii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter Chapter 2 --- Theory --- p.4 / Chapter 2.1 --- Radiation pressure on a microdroplet --- p.5 / Chapter 2.2 --- Mie scattering theory --- p.8 / Chapter 2.3 --- Laser levitation of a microdroplet --- p.11 / Chapter Chapter 3 --- Dual wavelength experiment --- p.14 / Chapter 3.1 --- Introduction --- p.15 / Chapter 3.2 --- Experiment --- p.16 / Chapter 3.2.1 --- Dual wavelength experiment --- p.16 / Chapter 3.2.2 --- Measurement of the levitating laser beam waist --- p.20 / Chapter 3.2.3 --- Measurement of the levitating laser beam profile --- p.22 / Chapter 3.3 --- Data analysis and results --- p.25 / Chapter 3.3.1 --- Deducing the size of a microdroplet by exploiting Ib(t) and Ig(t) --- p.27 / Chapter 3.3.2 --- Intensity as functions of size parameter --- p.32 / Chapter 3.3.3 --- Vertical position as a function of size parameter --- p.39 / Chapter 3.3.4 --- Comparison between experimental and theoretical results --- p.43 / Chapter 3.3.5 --- Broadening of MDRs --- p.55 / Chapter 3.3.6 --- Fine correction factor --- p.60 / Chapter Chapter 4 --- Deformation of a laser-levitated water microdroplet --- p.63 / Chapter 4.1 --- Introduction --- p.64 / Chapter 4.2 --- Experiment --- p.65 / Chapter 4.2.1 --- Dual wavelength experiment --- p.65 / Chapter 4.2.2 --- Double-slit experiment --- p.65 / Chapter 4.3 --- Data analysis and results --- p.68 / Chapter 4.3.1 --- """Cross-talk"" in dual wavelength experiment" --- p.69 / Chapter 4.3.2 --- MDR-induced oscillation of a laser-levitated water mircodroplet in dual wavelength experiment --- p.74 / Chapter 4.3.3 --- MDR-induced oscillation of a laser-levitated water mircodroplet in double-slit experiment --- p.81 / Chapter Chapter 5 --- Step-function levitation force experiment --- p.85 / Chapter 5.1 --- Introduction --- p.86 / Chapter 5.2 --- Step-function levitation force experiment --- p.87 / Chapter 5.3 --- Data analysis and results --- p.90 / Chapter 5.3.1 --- Deducing the size of the microdroplet by its vertical position --- p.91 / Chapter 5.3.2 --- Intensity curves of the step-function levitation force experiment --- p.95 / Chapter Chapter 6 --- Conclusion and future outlook --- p.99 / Chapter 6.1 --- Conclusion --- p.99 / Chapter 6.2 --- Future outlook --- p.101 / Appendix A --- p.103 / Appendix B --- p.104 / References --- p.105

Fu Pengpeng. / Thesis submitted in: August 2002. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 98-98). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgement --- p.iii / Table of Contents --- p.vii / List of Figures --- p.xii / List of Tables --- p.xiii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Background --- p.1 / Chapter 1.2 --- A Simple 2-D Mie Scattering Model --- p.2 / Chapter 1.3 --- Topics in the Following Chapters --- p.7 / Chapter 2 --- Beam-shape Coefficients for 2-D Monochromatic Laser Beam --- p.9 / Chapter 2.1 --- General Case --- p.9 / Chapter 2.2 --- Plane Wave Case --- p.13 / Chapter 2.3 --- General Case of An Arbitrary Beam --- p.15 / Chapter 3 --- "Modified Explicit Asymptotic Formulas for the Positions, Widths of Resonances in 2-D Mie Scattering" --- p.17 / Chapter 3.1 --- Introduction --- p.17 / Chapter 3.1.1 --- Positions --- p.19 / Chapter 3.1.2 --- Widths --- p.20 / Chapter 3.2 --- Positions of Resonances --- p.21 / Chapter 3.2.1 --- Derivation --- p.21 / Chapter 3.2.2 --- Numerical Comparison --- p.28 / Chapter 3.2.3 --- Separation --- p.30 / Chapter 3.2.4 --- Conclusion --- p.32 / Chapter 3.3 --- LineWidth --- p.32 / Chapter 3.3.1 --- TE Mode --- p.34 / Chapter 3.3.2 --- TM Mode --- p.36 / Chapter 3.3.3 --- Conclusion --- p.38 / Chapter 3.4 --- Conclusion --- p.39 / Chapter 4 --- Effects of Surface Perturbation of 2-D Mie Scattering --- p.42 / Chapter 4.1 --- Experimental Background --- p.42 / Chapter 4.2 --- Theoretical Derivation --- p.44 / Chapter 4.3 --- Numerical Results --- p.57 / Chapter 5 --- Conclusions and Discussions --- p.79 / Appendix --- p.81 / Chapter A --- Approximate Solution to One Matrix Equation with Pertur- bation --- p.82 / Chapter B --- Airy Functions --- p.87 / Chapter C --- Bessel Functions --- p.89 / Chapter C.1 --- Basic Properties of the Bessel Functions --- p.89 / Chapter C.2 --- Numerical Evaluation of The Bessel Functions --- p.91 / Bibliography --- p.94

Single particle TIRM experiments measure particle-surface separation distance by tracking scattered intensities. The scattered light is generated by an evanescent wave interacting with a levitating microsphere. The exponential decay of the evanescent wave, normal to the surface, results in scattered intensities that vary with separation distance. Measurement of the separation distance allows us to calculate the total potential energy profile acting on the particles. These experiments have been shown to exhibit nanometer spatial resolution and the ability to detect potentials on the order of kT with no external treatment of the particle. We find that the separation distance is a function of the decay of the evanescent wave and the size of the sphere. Different sizes of spheres, located the same distance from the surface, exhibit varying scattered intensity distributions. Single particles have been studied extensively but multiple particle experiments are needed for studies of more complex systems and surfaces. Increasing the number of colloidal particles in a TIRM experiment greatly increases the complexity of the system. Calculation of separation distances and potentials over a large group of microspheres requires that the spheres display a uniform stuck-particle intensity distribution. But, for large numbers of particles, this is not the case. In some instances, stuck-particle intensities can vary more than an order of magnitude. This research involves creating a mathematical model to study scattered intensity distributions for a large size range of polystyrene microspheres. The model is based on basic Mie theory. We compare the theoretically simulated results to the experimentally obtained results and find that scattered intensity variations in multiple particle TIRM experiments are attributed to particle polydispersity (particle size variation). This is a very important result because we know that if we can maintain a relatively uniform particle size distribution, then we will see a relatively uniform stuck-particle intensity distribution. The model can then be used to select a size range of microspheres that will exhibit a more uniform distribution so as to increase the sensitivity and feasibility of multiple particle TIRM.

An ultrasound spectrometer was designed, constructed and used to measure the frequency dependence of forward-scattered ultrasound from biological specimens. A piezoelectric transducer was continuously tuned through the frequency range of 150 to 400 MHz, producing ultrasound of the same frequency. Pulse modulation of the input signal permitted a frequency resolution of 2 MHz. The received pulse was detected at various temporal positions of its amplitude, thereby allowing measurement of the interference of the scattered and unscattered ultrasound radiation. Because of system nonlinearities all received signals were calibrated with respect to the attenuation of ultrasound in water over the system frequency range. The attenuation of water over the frequency range of 150 to 400 MHz was consequently measured and the values agreed very well with figures given in the literature. Forward-scattering experiments were performed with both physical objects and biological specimens. Sapphire spheres and plastic cylinders exhibited the expected Mie scattering resonant structure. Planar glass plates showed the commonly observed Fabry-Perot resonant structure. Measurement of the resonant frequencies agreed well with theoretically-predicted values. The biological specimens consisted of various cell suspensions of densities on the order of 100 million cells per milliliter. Because of the high cell densities necessary for signal measurement, only signal attenuation was measured. No resonant structure was observed. Synchronized growth colonies of mouse leukemia cells were investigated at both the plateau and log stages of cell growth. The attenuation of melanoma cells was measured with and without melanin. Also, various lines of tumor cells were investigated. For all of these cell suspensions, the attenuation in dB/mm increased linearly with the logrithm of frequency. Though the slope of the attenuation-frequency curves varied from cell line to cell line, the variation for the same cells under different biological conditions was not appreciable. For all of the above cell lines, no attenuation fell out of the range of 5 to 55 dB/mm.

No description available.