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Thesis (M.Sc. (Physics)) -- University of Limpopo, 2017 / The undoped ZnO nanoparticles, In or Co single doped ZnO nanoparticles and the In and Co combinational doped ZnO nanoparticles were synthesised through sol-gel technique. The samples were characterised using XRD, TEM, FTIR, Raman spectroscopy, UV-Vis, PL and also tested for the gas sensing applications. XRD patterns revealed that the synthesised samples were of ZnO hexagonal wurtzite structure. The lattice parameters and the bond length of all the undoped and doped ZnO samples were determined and found to be similar to that of the Bulk ZnO. The average particle size of the undoped and doped ZnO nanoparticles were calculated and found to reduce with an introduction of dopants while increasing with an increase in temperature. The strain of all the prepared samples were also determined and observed to be in an inverse relation to the particle size. TEM images showed that the synthesised samples were spherically shaped and that was in agreement with XRD results, while the EDS results showed that In and Co were successfully doped into the ZnO nanoparticles. Raman and FTIR spectroscopy indicated that the prepared samples were indeed ZnO nanoparticles which confirmed the XRD results. The UV-Vis results showed a red-shift in the energy band gap with an introduction of dopants and that was related to the reduction of the particle size, this results were consistent with the PL results. Gas sensing results showed that doping Co and In into the ZnO nanoparticles has an effect into ZnO properties. Combinational-doping of In and Co was found to increase the response to the gases CH4, CO, NH3 and H2 as compared to the undoped and singly doped ZnO nanoparticle sensors. The response\recovery time was found to be affected with introduction of In and Co. Improvements were also observed in the operating temperature and the selectivity of the single doped and co-doped ZnO nanoparticles towards different gases used in this study. / University of Limpopo IBSA National Research Foundation (NRF)

Many oncolytic virotherapies have shown great advantages for rapid, rational design through recombinant DNA technology to facilitate the targeting of a broad spectrum of malignancies. Newcastle disease virus (NDV), an avian paramyxovirus, is naturally tumor-selective and inherently oncolytic. Our approach is to develop NDV-based nanoparticles (VBNP) for oncolytic virotherapy. VBNPs are non-infectious and non-replicating and are relatively safe. We obtained VBNPs by co-expressing matrix (M), hemagglutinin (HN), and fusion (F) proteins of NDV in avian/ mammalian cells. The budding characteristics, size and morphology of VBNPs were similar to authentic virions. As a proof of concept, we engineered the apoptin (VP3) gene of chicken anemia virus in VBNPs and specifically targeted them to folate-receptor bearing tumor cells by surface conjugation to folate. The VBNPs killed tumor cells by apoptosis and induced proinflammatory and chemotactic cytokines. The VBNPs, although not curative, were able to limit the progression of xenotransplanted fibrosarcoma and malignant glioma tumors and provided a survival advantage in nude mice. We also engineered NDV M based particles with nipah virus surface glycorporteins to target ephrin B receptors. NDV based nipah Virus BNPs (NiV-ndBNP) were morphologically similar to authentic NiV virions. NiV glycoproteins were incorporated into the NDV M based particles, despite poor sequence homology in the transmembrane domain and cytoplasmic tails of glycoproteins. Our results suggest that VBNPs could be used to deliver small molecules, tumor antigens, anti-tumor/ reporter genes and also aid in generating tumor specific immunity by rational design. / Master of Science

Yes / Peptide-enabled nanoparticle (NP) synthesis routes can create and/or assemble functional nanomaterials under environmentally friendly conditions, with properties dictated by complex interactions at the biotic/abiotic interface. Manipulation of this interface through sequence modification can provide the capability for material properties to be tailored to create enhanced materials for energy, catalysis, and sensing applications. Fully realizing the potential of these materials requires a comprehensive understanding of sequence-dependent structure/function relationships that is presently lacking. In this work, the atomic-scale structures of a series of peptide-capped Au NPs are determined using a combination of atomic pair distribution function analysis of high-energy X-ray diffraction data and advanced molecular dynamics (MD) simulations. The Au NPs produced with different peptide sequences exhibit varying degrees of catalytic activity for the exemplar reaction 4-nitrophenol reduction. The experimentally derived atomic-scale NP configurations reveal sequence-dependent differences in structural order at the NP surface. Replica exchange with solute-tempering MD simulations are then used to predict the morphology of the peptide overlayer on these Au NPs and identify factors determining the structure/catalytic properties relationship. We show that the amount of exposed Au surface, the underlying surface structural disorder, and the interaction strength of the peptide with the Au surface all influence catalytic performance. A simplified computational prediction of catalytic performance is developed that can potentially serve as a screening tool for future studies. Our approach provides a platform for broadening the analysis of catalytic peptide-enabled metallic NP systems, potentially allowing for the development of rational design rules for property enhancemen / Air Force Office for Scientific Research (Grant #FA9550-12-1-0226, RRN; AFOSR LRIR) and DOE-BES grant DE-SC0006877, fellowship support from the National Research Council Research Associateship

Yes / Developing new methods to treat heart diseases is always a focus for basic research and clinical applications. Existing drugs have strong side-effects and also require lifetime administration for patients. Recent attempts of using nanoparticles (NPs) in treating atherosclerosis in animals and some heart diseases such as heart failure and endocarditis have provided hopes for better drug delivery and reducing of drug side-effects. In this mini-review, we summarize the present applications of using gold nanoparticles (GNPs) as a new drug delivery system in diseased hearts and of the assessment of toxicity in using GNPs. We suggest that conjugating existing clinical drugs with GNPs is a favorable choice to provide “new and double-enhanced” potentiality to those existing drugs in treating heart diseases. Other applications of using NPs in the treatment of heart diseases including using drugs in nano-form and coating drugs with a surface of relevant NP are also discussed.

Surface modification of colloidal nanoparticles is essential for broadening the scope of nanotechnology. In this dissertation, we discuss novel approaches to functionalize the surface of nanoparticles to tailor their properties for applications including radical polymerization inhibitors, supported heterogeneous catalysts, and building blocks for plasmonic devices. First, we investigate the interaction of hydrogen-terminated silicon nanoparticles (H-SiNPs) with Karstedt's catalyst and report a room‑temperature synthesis of Pt-coated SiNPs with highly tunable Pt loading. Analysis of the Pt on-Si ensemble reveals surface-bound Pt(II) on SiNPs which can undergo ligand exchange. Upon calcination, Pt-loaded SiNPs catalyze the hydrogenation of phenyl acetylene, and the SiNP scaffold enables efficient recovery and reuse of the catalyst. Conditions that favor the reductive elimination of the catalyst and efficient hydrosilylation of olefins are also discussed. Next, we report H-SiNPs as inhibitors for anerobic thermal autopolymerization of methacrylates. Prior to use, these solid-state inhibitors can be easily removed from the methacrylic monomers by low-speed centrifugation, offering great advantage to the traditionally used phenols and quinones. Analysis of SiNPs isolated after heating in methacrylates reveals the grafting of ester groups. As such, thermal hydrosilylation is presented as a powerful yet facile route to attach ester and allyl ester groups onto the surface of SiNPs. Finally, we report a method to rapidly and uniformly assemble gold nanoparticles (AuNPs) and their clusters on cm‑scale unmodified substrates. Cetyltrimethylammonium (CTAC) capped AuNPs were conjugated to a sparse coating of poly(ethylene glycol) and extracted into dichloromethane. The clustered patterns were deposited on hydroxyl terminated surfaces from stable dispersions using centrifugal force. The degree of clustering on substrates was tuned by varying a single parameter, the concentration of CTAC in the deposition dispersion. This approach bridges the gap between methods for depositing isolated AuNPs (typically using electrostatic interactions) and AuNP clusters (using covalent or electrostatic binders) and enables large-scale uniform deposition of isolated AuNPs, as well as clusters with tunable size. The non‑covalent assembly onto the substrate provided a means for depositing AuNPs into nanowells in topographically patterned substrates: after uniform deposition onto these substrates, the AuNPs on the surface were selectively removed using mechanical rubbing. This facile approach enabled large-scale selective deposition of AuNPs into patterned substrates that are attractive as SERS substrates and refractive index sensors.

In order to create more sensitive and accurate gas sensors, we have studied the interactions of gas mixtures on metal oxide nanoparticle decorated porous silicon interfaces. The nanoparticles control the magnitude and direction of electron transduction from the interaction of analyte gases to an extrinsic porous silicon semiconductor. These interactions can be predicted by the Inverse Hard Soft Acid Base (IHSAB) principle. Moreover, the metal oxide nanoparticles can be functionalized with nitrogen and sulfur, modifying the oxide’s band structure. These modifications are demonstrated to change analyte interactions in line with the IHSAB concept and allow for light enhanced sensors. Further we looked at how the analyte gases interact with other analyte gases on the surface of these sensors. Studying these systems does two things, first the research will lead to cheaper, more accurate gas sensors, and second it helps explore the role of nanoparticles in modifying the interactions between bulk materials (porous silicon) and molecules (analyte gases).

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: In an attempt to produce active catalysts for the oxidation of alkanes, hydrophobic dendritic micelle encapsulated gold nanoparticles were prepared. Dendrimers are well suited as templates for the encapsulation of metal nanoparticles as they can control the size and distribution of the particles. Using hydrophobic dendritic micelles it was found that the mode of encapsulation is driven by the solubility of the metal ions and not complexation of these ions, as is the case with conventional dendrimers. The dendritic micelles also provide the possibility of producing the dendrimer encapsulated nanoparticles in organic solvents, simplifying the encapsulation process as well as their subsequent application in catalysis. With this in mind, two types of dendritic micelles were synthesized. The first type, based on commercially available DAB PPI dendrimers, contained a diaminobutane core while the second type, containing a PAMAM interior architecture, has a cyclam core. Three generations of DAB PPI dendrimers were modified on their periphery with palmitoyl chloride to give the alkyl chain terminated hydrophobic DAB PPI dendritic micelles. The PAMAM-type cyclam-cored dendrimers were synthesized from the core outwards to produce two generations of cyclam-cored amine-terminated dendrimers. Their periphery could then be modified with palmitoyl chloride to produce two generations of alkyl chain terminated hydrophobic cyclam-cored dendritic micelles. The dendritic micelles were used as templates for the encapsulation of gold nanoparticles and these were fully characterized by UV/Vis spectroscopy and HR-TEM. Au13, Au31 and Au55 nanoparticles were encapsulated in each dendrimer template by varying the dendrimer to gold ratio. HR-TEM results indicate relatively uniform particles with an average particle size falling in the range of 4-6 nm. Finally, the dendrimer encapsulated nanoparticles (DENs) were applied as catalysts in the oxidation of n-octane. To the best of our knowledge DENs have not been applied as catalysts in the oxidation of linear alkanes. High substrate conversions, falling in the range of 70-90%, were achieved with all of the catalysts. Longer reaction times and lower catalyst loadings resulted in higher conversions with the optimum condition determined to be 0.1 mol% catalyst and 72 hours reaction time. It was also concluded that the nanoparticle size has a bigger influence on the conversion than the nature and generation of the dendrimer template. Overall the gold DENs show great potential as oxidation catalysts. / AFRIKAANSE OPSOMMING: In die poging om aktiewe katalisators vir die oksidasie van alkane te produseer is goud nanopartikels in die binne ruimtes van hidrofobiese dendritiese miselle ge-enkapsuleer. Dendrimere is geskikte template vir die enkapsulering van metaal nanopartikels a.g.v die feit dat dit die grootte en distribusie van die partikels kan beheer. Deur gebruik te maak van hidrofobiese dendritiese miselle verander die wyse van enkapsulering van kompleksering van metaal ione (die geval in konvensionele dendrimere) na oplossing gedrewe enkapsulering. Dendritiese miselle bied ook die moontlikheid om die dendrimer-ge-enkapsuleerde nanopartikels in organiese oplosmiddels voor te berei wat die enkapsulerings proses sowel as die toepassing in katalise vergemaklik. Met hierdie in gedagte is twee verskillende tipe dendritiese miselle gesintetiseer. Die eerste tipe, gebasseer op kommersieel beskikbare DAB PPI dendrimere, bevat ‘n diaminobutaan kern, terwyl die tweede tipe, bestaande uit ‘n PAMAM binne-struktuur, ‘n siklaam kern bevat. Drie generasies van DAB PPI dendrimere was gemodifieer op die periferie met palmitoïelchloried om alkiel ketting getermineerde hidrofobiese DAB PPI dendritiese miselle te produseer. Die PAMAM siklaam kern bevattende dendrimere was gesintetiseer van die kern uitwaarts om twee generasies amien getermineerde dendrimere te produseer. Dit was toe moontlik om die periferie met palmitoïelchloried te modifieer om twee generasies van alkiel getermineerde siklaam kern bevattende hidrofobiese dendritiese miselle op te lewer. Die dendritiese miselle was gebruik as template vir die enkapsulasie van goud nanopartikels en volledig gekarakteriseer deur UV/Vis spektroskopie en HR-TEM. Au13, Au31 and Au55 nanopartikels was ge-enkapsuleer in elk van die dendrimeer template deur die verhouding van dendrimeer tot goud te wissel. HR-TEM resultate dui aan dat die partikels goed versprei is met ‘n gemiddelde partikel grootte tussen 4-6 nm. Die dendrimeer ge-enkapsuleerde goud nanopartikels (DENs) was as katalisators in die oksidasie van n-oktaan toegepas. Volgens ons kennis is DENs nog nie toegepas as katalisators in die oksidasie van lineêre alkane nie. Hoë substraat omskakelings, tussen 70 en 90%, was deur al die katalisators bereik. ‘n Langer reaksie tyd en laer katalisator konsentrasies het hoër omsettings tot gevolg gehad. Die optimale kondisies sluit ‘n 0.1 mol% katalisator konsentrasie en 72 uur reaksie tyd in. Die gevolgtrekking was gemaak dat die nanopartikel grootte ‘n groter invloed op die substraat omsetting het as die aard en generasie van die dendrimeer templaat. Alles in ag geneem, wys die goud DENs groot potensiaal as oksidasie katalisators.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

The increasing use of engineered nanoparticles such as silver nanoparticles (AgNPs) has focused more attention on the transport of nanoparticles in natural and engineered systems. Despite a substantial number of studies on the transport of nanoparticles in groundwater flow conditions, other conditions such as those in granular media filtration in water treatment plant have not been fully explored. This study was designed to investigate the transport of AgNPs in granular media filtration with a relatively high filtration velocity (~2 m/hr) and a low influent AgNP concentration (~100 [mu]g/L). Effects of several physical and chemical parameters on the transport and attachment of AgNPs were examined, focusing on the colloidal filtration theory and particle-particle interaction, respectively. Regarding the transport of AgNPs, four physical parameters (filter depth, filtration velocity, filter media size, and AgNP size) were varied at a fixed chemical condition. Positively charged branched polyethylenimine (BPEI) capped AgNPs were chosen to examine the transport of AgNPs under electrostatically favorable attachment conditions. The effects of filter depth, filtration velocity, and filter media size on transport of AgNPs were adequately described by the well-known colloidal filtration model. However, deviation from the model prediction was apparent as the AgNP size became smaller, implying a possible variation of nanoparticle properties in the smaller size such as 10 nm. In the AgNP attachment study, negatively charged citrate- and polyvinylpyrrolidone (PVP)-capped AgNPs were employed to examine the chemical effects on particle (AgNP)-particle (filter media) interaction. When the ionic strength and ion type in the background water were varied, the attachment of citrate AgNPs followed the DLVO theory. Ca- or Mg-citrate complexation was found to lead to charge neutralization, resulting in a greater AgNP deposition onto the filter media. However, PVP AgNPs were only marginally affected by the electrostatic effect, demonstrating a stronger stabilizing effect by PVP than citrate. When natural organic matter (NOM) was introduced in the background water, the deviation from the DLVO theory was considered primarily due to the steric interaction by NOM coating onto particles. Different amounts of AgNP deposition for different types of NOM suggest the variation of steric effects according to the molecular weight of NOM. The deposition of humic acid-coated AgNPs was similar regardless of the capping agent, indicating the possible displacement of the capping agent by NOM. The electrostatic and steric interactions affected the detachment of AgNPs as well as the attachment of AgNPs. The amount of detachment depended on the depth and width of the secondary energy minimum. Also, the detachment was enhanced with NOM coating, probably due to a weak attachment by the steric effect. However, the hydrodynamic force employed in this study was insufficient to yield a remarkable detachment. Overall, the retention profile was a relatively vertical line (i.e., equal deposition with depth) when the AgNP aggregation was prevented by the electrostatic or steric repulsion, implying homogeneous AgNP capture throughout the filter bed. On the other hand, ripening (the capture of particles by attraction to previously retained particles) was favored at the top of the filter bed when the AgNP aggregation was allowable. / text