In order to truly understand the process-property behavior of polymer systems it is essential to identify the three dimensional structure of the materials fabricated. For heterogeneous polymer systems such as nanoparticle filled systems, determination of the three dimensional optical properties are particularly difficult. Such information is essential, however, if the behavior of these systems are to be understood and formalized. The purpose of the present research was to develop methods for measuring the optical characteristics of heterogeneous polymer systems nondestructively, in order to characterize their three dimensional behavior. The thesis contains three parts: Part A: Study of an Oriented Uniformly Distributed System: Stretched Isotactic Polypropylene- nano Carbon Black Films (IPP-CB). Three nondestructive optical methods: optical waveguide coupling, Fourier Transform Infrared (FTIR) spectroscopy and x-ray diffraction, were used to investigate the effect of the carbon black on the phase behavior and orientation of the films. It was found that the carbon black has little effect on the crystal form and crystallinity, but has a significant effect on the three dimensional orientation behavior of the polypropylene in the IPP-CB systems. Part B: Study of a non-Uniformly Distributed System: Compression Molded Poly (Methyl Methacrylate) with Nano Indium Tin Oxide (PMMA-ITO) The PMMA-ITO sample is an un-oriented and non-uniformly mixed system which has a grain structure. A unique Break Point Waveguide Method was developed to deal with this problem. It was found that both the refractive index and the extinction coefficient increased with ITO concentration and the samples were three dimensionally random. Part C: Development of Computational Improvements in System Operations Four methods were developed to improve the accuracy of the waveguide methods. They are the Bootstrap Method, the Two-Line Method, the Big Area Method and the Modified Knee method. In conclusion, the three dimensional optical characteristics of two different kinds of heterogeneous polymer systems, oriented uniformly distributed IPP-CB films and non-uniformly distributed PMMA-ITO composites, are obtained and their structures evaluated. Further, several new methods were developed to improve the accuracy of the current optical waveguide methods.

Doctor of Philosophy / Department of Biological & Agricultural Engineering / Ronaldo G. Maghirang / Nanostructured particles possess unique chemical and physical properties, making them excellent candidates for air purification, smoke clearing, and obscuration. This research was conducted to investigate the aerodynamic, charging, and infrared (IR) extinction properties of nanostructured particles. Specific objectives were to: (1) measure the size distribution and concentration of aerosolized nanostructured particles; (2) evaluate their IR extinction properties; (3) determine their relative chargeability; and (4) numerically model their transport in enclosed rooms. The size distribution and concentration of two nanostructured particles (NanoActive® MgO and MgO plus) were measured in an enclosed room. The particles differed in size distribution and concentration; for example, the geometric mean diameters of NanoActive® MgO and MgO plus were 3.12 and 11.1 [Mu]m, respectively. The potential of nanostructured particles as IR obscurants was determined and compared with other particles. Four groups of particles were considered: nanostructured particles (NanoActive® MgO plus, MgO, TiO[subscript2]); nanorods (MgO, TiO[subscript2]); conventional particles (NaHCO[subscript3] and ISO fine test dust); and common obscurants (brass, graphite, carbon black). The extinction coefficients of the nanostructured particles were generally significantly smaller than those of the other particles. Graphite flakes had the greatest mass extinction coefficient (3.22 m[superscript2]/g), followed by carbon black (1.72 m[superscript2]/g), and brass flakes (1.57 m[superscript2]/g). Brass flakes had the greatest volume extinction coefficient (1.64 m[superscript2]/cc), followed by NaHCO[subscript3] (0.93 m[superscript2]/cc), and ISO fine test dust (0.91 m[superscript2]/cc). The relative chargeability of nanostructured particles was also investigated. Selected particles were passed through a Teflon tribocharger and their net charge-to-mass ratios were measured. Tribocharging was able to charge the particles; however, the resulting charge was generally small. NanoActive® TiO[subscript2] gained the highest net charge-to-mass ratio (1.21 mC/kg) followed by NanoActive® MgO (0.81 mC/kg) and ISO fine test dust (0.66 mC/kg). The transport of NanoActive® MgO plus and hollow glass spheres in an enclosed room was simulated by implementing the discrete phase model of FLUENT. In terms of mass concentrations, there was reasonable agreement between predicted and measured values for hollow glass spheres but not for NanoActive® MgO plus. In terms of number concentration, there was large discrepancy between predicted and measured values for both particles.

Cette thèse est consacrée à l’étude de films minces ouverts de cristaux liquides colonnaires sur un substrat solide. Ces matériaux, capables de s’auto-organiser en de larges domaines orientés, sont généralement obtenus à partir de molécules discotiques dérivées de colorants aromatiques. Ces différentes caractéristiques, associées à une bonne mobilité de charges, permettent d'envisager l'utilisation des cristaux liquides colonnaires en film mince dans des dispositifs photovoltaïques. Afin de bénéficier de leurs bonnes propriétés optoélectroniques, les cristaux liquides colonnaires doivent être déposés en film mouillant, d’épaisseur inférieure à 100 nm, et leur orientation contrôlée. Ainsi, pour des applications photovoltaïques, un alignement homéotrope (colonnes normales au substrat) est requis. Inversement, l’orientation planaire uniaxe (colonnes parallèles au substrat), est quant à elle requise pour une utilisation de ces composés dans les polariseurs ou dans les transistors organiques à effet de champ. Dans ce travail, différentes méthodes permettant de contrôler l’alignement de films minces ouverts de cristaux liquides colonnaires ont été développées, permettant d’obtenir aussi bien un ancrage homéotrope par traitement thermique spécifique, qu’un ancrage planaire uniaxe par dépôt préalable d’une couche de téflon. Le contrôle de l’orientation a ainsi permis d’une part de produire un film mince (e ? 50 nm) mouillant en ancrage homéotrope ouvrant la voie vers des cellules solaires organiques efficaces, et d’autre part de déterminer l’ensemble des propriétés optiques (indices complexes anisotropes) de ces matériaux cristallins liquides colonnaires. La dynamique du démouillage et l’état d’équilibre d’un film mince ouvert de cristal liquide colonnaire ont également été étudiés. Les résultats expérimentaux révèlent la formation de gouttelettes anisotropes et la présence d’un film nanométrique lors du démouillage de ce film mince / This thesis deals with columnar liquid crystal studied in the geometry of open supported thin films. Columnar liquid crystals are usually made of disk-shaped molecules derived from aromatic dyes. They are efficient charge transporters with the added capacity to self-assemble in large oriented domains. Consequently, such materials may be used in photovoltaic devices. In order to benefit from their good uniaxial charge mobility, their organization has to be controlled in uniform oriented thin films in the range of thicknesses of typically 100 nm. Homeotropic alignment (columns normal to the interface) is required for solar cells whereas uniaxial planar anchoring (columns parallel to the interface) is needed for applications such as polarizers or organic field effect transistor. Different methods to monitor the alignment in open thin films have been developed in this work, which make possible to achieve either homeotropic anchoring by a specific thermal treatment, or uniaxial planar orientation using a Teflon layer. Based on these orientation skills, a uniform ultra-thin film, free of dewetting and homeotropically oriented, is achieved (down to 50 nm thick) opening the way towards efficient solar cells, and a complete study of the optical properties has been performed (with the determination of the anisotropic complex indices) for different columnar liquid crystals. The dynamics of dewetting and the equilibrium state of a thin supported film have also been investigated. Experimental results show the formation of anisotropic droplets and reveal a nanometric film during dewetting.

The objective of this study is to examine core-shell type plasmonic metamaterials aimed at the development of materials with unique electromagnetic properties. The building blocks of metamaterials under study consist of gold as a metal component, and silica and precipitated calcium carbonate (PCC) as the dielectric media. The results of this study demonstrate important applications of the core-shells including scattering suppression, airborne obscurants made of fractal gold shells, photomodification of the fractal structure providing windows of transparency, and plasmonics core-shell with a gain shell as an active device. Plasmonic resonances of the metallic shells depend on their nanostructure and geometry of the core, which can be optimized for the broadband extinction. Significant extinction from the visible to mid-infrared makes fractal shells very attractive as bandpass filters and aerosolized obscurants. In contrast to the planar fractal films, where the absorption and reflection equally contribute to the extinction, the shells' extinction is caused mainly by the absorption. This work shows that the Mie scattering resonance of a silica core with 780 nm diameter at 560 nm is suppressed by 75% and only partially substituted by the absorption in the shell so that the total transmission is noticeably increased. Effective medium theory supports our experiments and indicates that light goes mostly through the epsilon-near-zero shell with approximately wavelength independent absorption rate. Broadband extinction in fractal shells allows as well for a laser photoburning of holes in the extinction spectra and consequently windows of transparency in a controlled manner. Au fractal nanostructures grown on PCC flakes provide the highest mass normalized extinction, up to 3 m^2/g, which has been demonstrated in the broad spectral range. In the nanoplasmonic field active devices consist of a Au nanoparticle that acts as a cavity and the dye molecules attached to it via thin silica shell as the active medium. Such kind of devices is considered as a nano-laser or nano-amplifier. The fabricated nanolasers were studied for their photoluminescence kinetic properties. It is shown that the cooperative effects due to the coupling of dye molecules via Au nanoparticle plasmons result in bi-exponential emission decay characteristics in accord with theory predictions. These bi-exponential decays involve a fast superradiant decay, which is followed by a slow subradiant decay. To summarize, this work shows new attractive properties of core-shell nanoparticles. Fractal Au shells on silica cores prove to be a good scattering suppressor and a band pass filter in a broadband spectral range. They can also be used as an obscurant when PCC is used as the core material. Finally, gold nanoparticles coated with silica with dye results in bi-exponential decays.

No description available.

Aerosols are small, micrometer-sized particles, whose optical effects coupled with their impact on cloud properties is a source of large uncertainty in climate models. While their radiative forcing impact is largely of a cooling nature, there can be significant variations in the degree of their impact, depending on the size and the nature of the aerosols. The radiative and optical impact of aerosols are, first and foremost, dependent on their concentration or number density (an extensive parameter) and secondly on the size and nature of the aerosols (intensive, per particle, parameters). We employed passive (sunphotmetry) and active (backscatter lidar) measurements to retrieve extensive optical signals (aerosol optical depth or AOD and backscatter coefficient respectively) and semi-intensive optical signals (fine and coarse mode OD and fine and coarse mode backscatter coefficient respectively) and compared the optical coherency of these retrievals over a variety of aerosol and thin cloud events (pollution, dust, volcanic, smoke, thin cloud dominated). The retrievals were performed using an existing spectral deconvolution method applied to the sunphotometry data (SDA) and a new retrieval technique for the lidar based on a colour ratio thresholding technique. The validation of the lidar retrieval was accomplished by comparing the vertical integrations of the fine mode, coarse mode and total backscatter coefficients of the lidar with their sunphotometry analogues where lidar ratios (the intensive parameter required to transform backscatter coefficients into extinction coefficients) were (a) computed independently using the SDA retrievals for fine mode aerosols or prescribed for coarse mode aerosols and clouds or (b) computed by forcing the computed (fine, coarse and total) lidar ODs to be equal to their analog sunphotometry ODs. Comparisons between cases (a) and (b) as well as the semi-qualitative verification of the derived fine and coarse mode vertical profiles with the expected backscatter coefficient behavior of fine and coarse mode aerosols yielded satisfactory agreement (notably that the fine, coarse and total OD errors were <~ sunphotometry instrument errors). Comparisons between cases (a) and (b) also showed a degree of optical coherency between the fine mode lidar ratios.

*‘Pasja’ (Brassica campestris x napus) and kale (Brassica oleracea var. acephala L.) were grown at Lincoln, Canterbury, New Zealand in 2008 with different levels of phosphorus (P) fertiliser. Banded or broadcast P fertiliser was applied at 0, 20, 40 and 60 kg P/ha at establishment. Total dry matter (DM) production, the proportion of the leaf and stem and leaf area development were measured over time and related to the biophysical environment. For ‘Pasja’, final DM increased with P rate from 3730 kg DM/ha to ~4900 kg DM/ha at 60 kg P/ha. For kale the increase was from 8710 kg DM/ha for the control to ~11000 kg DM/ha for all P treatments. The leaf to stem ratio declined from 22-31 at 17 days after emergence to 10.4 at the final harvest for ‘Pasja’, which meant the crop was effectively made up mainly of leaf (~90%). The ratio for kale declined from 2.7 at 24 days after emergence to 0.64 at the final harvest. The leaf to stem ratio for both species did not respond to either the method of application or rate of P. Seedling DM accumulation increased with applied P over the first 10 to 17 DAE for ‘Pasja’ and kale respectively. The crops went from shoot growth priority to root growth. The phyllochron of both species was unaffected by P application but responded linearly to the temperature above 0°C. For ‘Pasja’ the phyllochron was 60°Cd compared with 109°Cd for kale. As a consequence ‘Pasja’ developed its canopy and reached critical leaf area index (LAIcrit) earlier than kale. Leaf area index (LAI) for the control crops of both species was lower than for P fertiliser treatments with a maximum of 3.6 for ‘Pasja’ and 3.8 for kale. There was no difference in leaf area indices among the P fertiliser treatments for ‘Pasja’, while kale LAI differed with the rate of P application up to 40 kg P/ha. Total accumulated intercepted solar radiation (RIcum) was 8 and 11% greater for ‘Pasja’ and kale crops respectively when P was applied compared with the control. Thus, the difference in total dry matter yield due to P application was attributed to the difference in RIcum. Neither the method of application or rate of P applied affected the radiation use efficiency (RUE) of either crop. For ‘Pasja’ the RUE was 1.1 g DM/MJ PAR and for kale 1.33 g DM/MJ PAR. Based on this research, it was concluded that P application increased RIcum as a result of increased LAI. The difference in total DM yield was attributed to differences in RIcum. It is recommended that farmers growing ‘Pasja’ and kale under similar conditions to this experiment should apply 40 kg P/ha for ‘Pasja’ and band 20 kg P/ha for kale. *‘Pasja’ is considered both as a species and cultivar in this document as it marketed as such in New Zealand. Technically ‘Pasja’ is a leaf turnip.

Nanomaterials are playing an increasing role in novel technologies, and it is important to develop optical methods to characterize them in situ.  To that end, backside absorbing layer microscopy (BALM) has emerged as a powerful tool, being capable to resolve sub-nanometer height profiles, with video-rate acquisition speeds and a suitable geometry to couple live experiments.  In the internship, several techniques involving BALM were developed, and applied to study optical and electrical properties of the transition metal dichalcogenide (TMD) monolayer MoS2, a type of 2-dimensional (2D) crystalline semiconductor.  A simulations toolkit was created in MATLAB to model BALM, a workflow to reliably extract linear intensities from the CMOS detector was realized, and 2D MoS2 was synthesized by chemical vapor deposition followed by transfer to appropriate substrates.  BALM data of the 2D MoS2 was acquired and combined with simulations, giving a preliminary result for its complex refractive index at 5 optical wavelengths.  In addition, the first steps towards coupling BALM with a gate biased 2D MoS2 field-effect transistor were explored.  To complement BALM measurements, the grown samples were also characterized by conventional optical microscopy, scanning electron microscopy, atomic force microscopy, photoluminescence spectroscopy, and Raman spectroscopy.  This work provides new additions to an existing platform of BALM techniques, enabling novel BALM experiments with nanomaterial systems.  In particular, it introduces a new alternative for local extraction of optical parameters and for probing of electrical charging effects, both of which are vital in the research and development of nano-optoelectronics.