Made available in DSpace on 2014-12-17T14:07:15Z (GMT). No. of bitstreams: 1 MaraTST_DISSERT.pdf: 2071273 bytes, checksum: 9636b6602dd1a469f78b17d077ba757f (MD5) Previous issue date: 2013-03-04 / In recent decades have seen a sharp growth in the study area of nanoscience and nanotechnology and is included in this area, the study of nanocomposites with self-cleaning properties. Since titanium dioxide (TiO2) has high photocatalytic activity and also antimicrobial, self-cleaning surfaces in your application has been explored. In this study a comparison was made between two synthesis routes to obtain TiO2 nanoparticles by hydrothermal method assisted by microwave. And after analysis of XRD and SEM was considered the best material for use in nanocomposites. It was deposited nanocomposite film of poly (dimethyl siloxane) (PDMS) with 0.5, 1, 1.5 and 2% by weight of nanoparticles of titanium dioxide (TiO2) by the spraying method. The nanocomposite was diluted with hexane and the suspension was deposited onto glass substrate, followed by curing in an oven with forced air circulation. The photocatalytic activity of the nanocomposite impregnated with methylene blue was evaluated by UV- vis spectroscopy from the intensity variation of absorption main peak at 660nm with time of exposure to the UV chamber. Changes in the contact angle and microhardness were analyzed before and after UV aging test. The effect of ultraviolet radiation on the chemical structure of the PDMS matrix was evaluated by spectrophotometry Fourier transform infrared (FTIR).The results indicated that the addition of TiO2 nanoparticles in the coating PDMS gave high photocatalytic activity in the decomposition of methylene blue, an important characteristic for the development of self-cleaning coatings / Nas ?ltimas d?cadas tem-se observado um crescimento acentuado no estudo da ?rea de nanoci?ncia e nanotecnologia em que inclui-se nessa ?rea, o estudo de nanocomp?sitos com propriedades autolimpantes. Desde que o di?xido de tit?nio (TiO2) apresenta alta atividade fotocatal?tica e tamb?m, atividade antimicrobiana, sua aplica??o em superf?cies autolimpantes tem sido amplamente explorada. Neste trabalho foi feito uma compara??o entre duas rotas de s?ntese para obten??o de nanopart?culas de TiO2 pelo m?todo hidrot?rmico assistido por micro-ondas. Ap?s an?lise de DRX e MEV foi analisado o melhor material para aplica??o em nanocomp?sitos. Foram depositados filmes de nanocomp?sito de poli(dimetil siloxano) (PDMS) com 0,5, 1, 1,5 e 2% em massa de nanopart?culas de di?xido de tit?nio (TiO2) pelo m?todo de aspers?o. O nanocomp?sito foi dilu?do em hexano e a suspens?o foi depositada sobre l?minas de vidro, seguida de cura em estufa com circula??o for?ada de ar. A atividade fotocatal?tica do nanocomp?sito impregnado com azul de metileno foi avaliada pela t?cnica de espectroscopia de UV-V?sivel, a partir da varia??o da intensidade de absor??o do pico principal a 660 nm com o tempo de exposi??o em c?mara UV. Altera??es no ?ngulo de contato e na microdureza foram analisadas antes e ap?s o ensaio de envelhecimento UV. O efeito da radia??o ultravioleta na estrutura qu?mica da matriz de PDMS foi avaliado por espectrofotometria no infravermelho por transformada de Fourier (FTIR). Os resultados indicaram que a adi??o das nanopart?culas de TiO2 em PDMS conferiram ao revestimento boa atividade fotocatal?tica na decomposi??o do azul de metileno, caracter?stica importante para o desenvolvimento de revestimentos autolimpantes

abstract: This study analyzes the thermoelectric phenomena of nanoparticle suspensions, which are composed of liquid and solid nanoparticles that show a relatively stable Seebeck coefficient as bulk solids near room temperature. The approach is to explore the thermoelectric character of the nanoparticle suspensions, predict the outcome of the experiment and compare the experimental data with anticipated results. In the experiment, the nanoparticle suspension is contained in a 15cm*2.5cm*2.5cm glass container, the temperature gradient ranges from 20 °C to 60 °C, and room temperature fluctuates from 20 °C to 23°C. The measured nanoparticles include multiwall carbon nanotubes, aluminum dioxide and bismuth telluride. A temperature gradient from 20 °C to 60 °C is imposed along the length of the container, and the resulting voltage (if any) is measured. Both heating and cooling processes are measured. With three different nanoparticle suspensions (carbon nano tubes, Al2O3 nanoparticles and Bi2Te3 nanoparticles), the correlation between temperature gradient and voltage is correspondingly 8%, 38% and 96%. A comparison of results calculated from the bulk Seebeck coefficients with our measured results indicate that the Seebeck coefficient measured for each suspension is much more than anticipated, which indicates that the thermophoresis effect could have enhanced the voltage. Further research with a closed-loop system might be able to affirm the results of this study. / Dissertation/Thesis / M.S. Mechanical Engineering 2010

abstract: This study investigates the effect of the virgin granular activated carbon (GAC) on the properties of synthesized iron (hydr)oxide nanoparticles impregnated GAC (Fe-GAC) media and its ability to remove arsenate and organic trichloroethylene (TCE) from water. Fe-GAC media were synthesized from bituminous and lignite-based virgin GAC via three variations of a permanganate/Fe(II) synthesis method. Data obtained from an array of characterization techniques indicated that differences in pore size distribution and surface chemistry of the virgin GAC favor different reaction paths for the iron (hydr)oxide nanoparticles formation. Batch equilibrium isotherm testing (120 µg-As/L; 6 mg-TCE/L, 10 mM NaHCO3 at pH = 7.2 ± 0.1 and pH = 8.2 ± 0.1) showed arsenic removal capability was increased as a result of iron (nanoparticles) impregnation, while TCE removal properties were decreased in Fe-GAC media. This tradeoff was displayed by both lignite and bituminous Fe-GAC but was most pronounced in lignite-based Fe-GAC having the highest Fe content (13.4% Fe) which showed the most favorable Freundlich adsorption and intensity parameters for arsenic of Ka = 72.6 (µg-As/g-FeGAC)(L/µg-As)1/n, 1/n = 0.6; and least favorable adsorption for TCE of Ka = 0.8 (mg-TCE/g-FeGAC)(L/mg-TCE)1/n, 1/n = 4.47. It was concluded that iron content was the main factor contributing to enhanced arsenic removal and that this was affected by base GAC properties such as pore size distribution and surface functional groups. However high Fe content can result in pore blockage; reduction in available adsorption sites for organic co-contaminants; and have a significant effect on the Fe-GACs overall adsorption capacity. / Dissertation/Thesis / M.S. Technology 2010

Plasmon coupling is known to cause distance dependent red-shifts of the characteristic plasmon resonance and localize strong electric fields to the gap between individual nanoparticles. These effects form the basis of nanoscale plasmonic sensors designed by creating specic structures of coupled nanoparticles. The simplest of these structures, a nanoparticle dimer, can easily be assembled through molecular self-assembly, resulting in a structure called a plasmon ruler. These plasmon rulers are crucial tools for the measurement of nanoscale distances, but the impact of the molecular linker on the plasmonic response of the coupled system remains insufficiently understood. In this dissertation, plasmons rulers composed of 40 nm gold nanoparticles are utilized to systematically investigate the potential effects of one molecular linker, DNA, on the strength of the plasmon coupling at a variety of interparticle separations. The strength of the plasmon coupling is determined based on the shifting of the plasmon resonance, which, at separations below 2.7 nm, is significantly blue-shifted when compared to expected values from electromagnetic simulations and experiments without DNA linkers. This deviation indicates a reduced charge accumulation on the nanoparticles in the gap region and is ascribed to DNA-mediated charge transfer. Enhancements to the charge transfer capabilities of the DNA were also investigated, through the deposition of interstitial palladium nanocrystals on the DNA linkers. The deposition of these nanocrystals results in a variety of structural changes to the plasmon rulers, associated with blue- and red-shifts of the plasmon resonance relative to electromagnetic simulations without gap material and experimental spectra of structures without molecular or metallic linkers. The relative blue-shift of the resonance results from a variety of scenarios, including short interparticle separations bridged by DNA or palladium nanocrystals, the build-up of palladium nanocrystals within the gap, or the incorporation of discrete palladium nanoparticles in the DNA linkers. The underlying mechanisms of the observed spectral shifts are analyzed. The red-shifted resonances resulted from a significant build-up of palladium nanocrystals in the gap, effectively linking the gold nanoparticles and forming a hybrid nanorod-like structure.

Concise syntheses of the natural products brosimones A and B have been achieved using sequential dehydrogenative Diels-Alder (DHDA) cycloadditions. The syntheses employ either Pt/C-cyclopentene or DDQ to effect dehydrogenation of prenylchalcone substrates in combination with silver nanoparticles (AgNP’s) to promote subsequent Diels-Alder cycloadditions. A concise, biomimetic approach to sorbiterrin A has been developed employing consecutive Michael additions of a 4-hydroxypyrone to a sorbicillinol derivative and silver nanoparticle-mediated bridged aldol/dehydration to construct the [3.3.1] ring system. The relative stereochemistry of sorbiterrin A was unambiguously confirmed by X-ray crystallographic analysis. Metal-catalyzed, double Claisen rearrangement of a bis-allyloxyflavone has been utilized to enable a concise synthesis of the hydrobenzofuro[3,2-b]chromenone core structure of the natural products sanggenon A and sanggenol F. In addition, catalytic, enantioselective [4+2] cycloadditions of 2’-hydroxychalcones have been accomplished using B(OPh)3/BINOL complexes. Asymmetric syntheses of the flavonoid Diels-Alder natural products sanggenons C and O have been achieved employing a stereodivergent reaction of a racemic mixture (stereodivergent RRM) involving [4+2] cycloaddition. Diaporine is a natural product containing a novel epoxyquinol dimer framework. An efficient annulation involving pyrone addition to a quinone has been developed for rapid assembly of the γ-naphthopyrone core structure. Dimerization was achieved through a Pd(II)-mediated dehydrogenative coupling. A natural product and precursor to diaporine, aurofusarin, was synthesized in excellent yield through an oxidation and demethylation sequence. In addition, diastereoselective epoxidation of aurofusarin was achieved using a phase transfer catalytic system.

Assisted reproductive technology (ART) has been rapidly expanding since the birth of Louise Brown, the first test tube baby, in 1978. Although an increasingly complex array of laboratory skills and procedures have been developed for infertility treatments, the success rate of ART remains low. In an attempt to make ART safer and more efficient, international medical practice is trending towards single embryo transfers and the use of innovative, sophisticated technologies to identify promising gametes and embryos with the highest potential to generate a pregnancy. Laser technology is increasingly being used to accomplish these aims. The application of lasers for ART has been successfully employed in clinical practice for some time now and is continually the subject of investigative research in order to generate new methods to improve operations. Moreover, lasers serve as a powerful tool at the forefront of investigative research in the reproductive sciences, assisting in broadening our understanding of reproductive and developmental biology. Nevertheless, there is a paucity of literature pertaining to the safe standardisation of such laser procedures with evidence at the molecular level. The primary aim of this thesis was to optimise applications of laser technology for clinical ART and research applications in the reproductive sciences. This thesis utilised the mouse embryo model to investigate potential deleterious effects of different laser treatment applications, both by the operator and hardware manufacturer. Safe and unsafe laser operator parameters were elucidated by assessing deleterious effects to the plasma membrane integrity, blastocyst survival rate, DNA fragmentation levels, and changes in gene expression of key developmental genes. The effect of altering the laser hardware to lower the power output was evaluated and it was determined that if a lower power laser is used to deliver a set amount of energy over a longer period of time, a smaller amount of damage is incurred. Work in this thesis also established a new method in which laser technology can be used as a research tool for the reproductive sciences, by creating a novel stimuli-responsive laser-activated nanoparticle delivery system with spatial control and increased efficiency in a mammalian cell model. The field of reproductive science continues to benefit greatly from laser application clinically to improve infertility treatments, and in research, to elucidate mechanisms underlying infertility, with a hope of increasing our understanding and eventually developing new treatment options.

abstract: Plasmon resonance in nanoscale metallic structures has shown its ability to concentrate electromagnetic energy into sub-wavelength volumes. Metal nanostructures exhibit a high extinction coefficient in the visible and near infrared spectrum due to their large absorption and scattering cross sections corresponding to their surface plasmon resonance. Hence, they can serve as an attractive candidate for solar energy conversion. Recent papers have showed that dielectric core/metallic shell nanoparticles yielded a plasmon resonance wavelength tunable from visible to infrared by changing the ratio of core radius to the total radius. Therefore it is interesting to develop a dispersion of core-shell multifunctional nanoparticles capable of dynamically changing their volume ratio and thus their spectral radiative properties. Nanoparticle suspensions (nanofluids) are known to offer a variety of benefits for thermal transport and energy conversion. Nanofluids have been proven to increase the efficiency of the photo-thermal energy conversion process in direct solar absorption collectors (DAC). Combining these two cutting-edge technologies enables the use of core-shell nanoparticles to control the spectral and radiative properties of plasmonic nanofluids in order to efficiently harvest and convert solar energy. Plasmonic nanofluids that have strong energy concentrating capacity and spectral selectivity can be used in many high-temperature energy systems where radiative heat transport is essential. In this thesis，the surface plasmon resonance effect and the wavelength tuning ranges for different metallic shell nanoparticles are investigated, the solar-weighted efficiencies of corresponding core-shell nanoparticle suspensions are explored, and a quantitative study of core-shell nanoparticle suspensions in a DAC system is provided. Using core-shell nanoparticle dispersions, it is possible to create efficient spectral solar absorption fluids and design materials for applications which require variable spectral absorption or scattering. / Dissertation/Thesis / M.S. Mechanical Engineering 2012

Philosophiae Doctor - PhD / In this thesis, I present the electrochemical studies of three dendrimeric polypropylene imine (PPI) nanomaterials and their applications as a platform in the development of a novel label free DNA nanobiosensor based on electrochemical impedance spectroscopy. Cyclic voltammetry (CV), differentia pulse voltammetry (DPV), square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS) techniques were used to study and model the electrochemical reactivities of the nanomaterials on glassy carbon electrode (GCE) as the working electrode. / South Africa

xx, 242 p. : ill. (some col.) / Applications of ligand-protected nanoparticles have increased markedly in recent years, yet their controlled synthesis remains an under-developed field. Nanoparticle syntheses are highly specialized in their execution and often possess significant limitations. For example, the synthesis of thiol-stabilized gold nanoparticles (AuNPs) with core diameters greater than 5.0 nm is difficult to achieve using existing methods. This dissertation describes the development of a synthetic strategy for thiolate-stabilized AuNPs over a wide range of core sizes using alkyl thiosulfates (Bunte salts) as ligand precursors. The use of Bunte salts permits the synthesis of larger AuNPs than can be achieved using thiols by allowing the AuNP cores to grow to larger diameters before the formation of the thiolate ligand shell. Chapter II details the development of a direct synthesis strategy using Bunte salts as ligand precursors that produces AuNPs with diameters up to 20 nm. Chapter III describes an investigation of the ligand shell formation that occurs during these syntheses. The ligand shell formation involves the adsorption of the Bunte salt to the AuNP surface, where it is converted to the thiolate. This conversion requires an excess of sodium borohydride in the synthesis of >5 nm AuNPs, but not for the synthesis of smaller AuNPs. This synthetic strategy was adapted for use in flow reactors to attain simultaneous AuNP synthesis and characterization. Chapter IV demonstrates that thiol-stabilized AuNPs can be synthesized in a microfluidic device with product monitoring provided by UV-vis absorbance spectroscopy. The development of a capillary flow reactor that permits the incorporation of new monitoring techniques is presented in Chapter V. The incorporation of Small-Angle X-ray Scattering (SAXS) analysis provides quantitative <italic>in situ</italic> determinations of AuNP diameter. The combination of synthetic control and monitoring makes capillary flow reactors powerful tools for optimization of NP syntheses and monitoring NP growth. In Chapter VI, the capillary flow reactor is used in an investigation of AuNP core growth. We also review AuNP growth mechanisms and show how to differentiate these using SAXS and UV-vis analysis. In these studies, AuNP growth is unexpectedly shown to involve a coalescence mechanism. This dissertation includes previously published and co-authored material. / Committee in charge: Victoria De Rose Chairperson; James E. Hutchison, Advisor; Catherine Page, Member; Darren W. Johnson, Member; Miriam Deutsch, Outside Member

The aim of this master thesis is to focus on a various methods of the conjugation of palladium nanoparticles of different shapes on the protein. The main point was to use both covalent and non-covalent conjugation of palladium nanoparticles on the protein and to use the functional conjugates to find out their stability in time.