In this study, advanced techniques in the synthesis of germanium nanoparticles have been investigated. Based on physical and chemical production methods, including stain etching, liquid-phase pulsed laser ablation, sol-gel synthesis and two benchtop colloidal synthesis techniques, germanium nanoparticles with various surface terminations were formed. Out of those, colloidal synthesis by benchtop chemistry (named CS1) were found to be the most promising synthesis route in terms of yield and stability of the as-prepared Ge qdots and its luminescence with almost no oxides present. For the characterisation of Ge nanoparticles, Raman spectroscopy, Photoluminescence (PL) spectroscopy, Transmission electron microscopy (TEM) with energy dispersive X-ray spectroscopy (EDX) and selective area electron diffraction (SAED) techniques were utilised before conducting X-ray absorption spectroscopy (XAS) measurements. The structure and morphology of Ge quantum dots formed using colloidal synthesis routes were found to fit best to the model of a nanocrystalline core surrounded by disordered Ge layers. Optically-detected X-ray absorption studies have enabled us to establish a direct link between nanoparticles structure and the source of the luminescence. The most important outcome of this study is that it provides a direct experimental route linking synthesis conditions and properties of nanosized Ge quantum dots. Furthermore, using annealing, we can control surface termination even further, as well as change particle size and possibly produce metastable phases.

Gao Jun. / "November 1998." / Thesis (Ph.D.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Since a few years, nanomaterials are more and more used in industrial process. In order to protect the population and the environment from the consequences of an accidental release into the atmosphere, the risk assessment allowed to identify the accidental scenario in transport, manipulation and storage of those products. The accidental leakage of the conveying pipe may lead to a massive release of nanoparticles. In order to evaluate the consequences of this type of accident, our study focuses on the prediction of particles properties dispersed into the air, for example the particle number concentration and the particle diameter distribution. The first step of the study consists in the analyse of physical phenomena related to nanoparticles in order to choose the most predominant physical phenomena to model. The relevant physical phenomena in the present configuration are the agglomerate complex shape, the drag force on agglomerates, the agglomerate breakage by gas, the agglomerate collision and the agglomeration. After that, the modelling of physical phenomena chosen is developed in CFD tool Code\_Saturne. For each physical phenomenon, a simulation test case is realized in order to verify the development in CFD tool. A good agreement between CFD tool Code\_Saturne and 0D tool from Scilab and model in the literature is obtained. Also in the present study, new model for the collision probability of agglomerates is proposed. This new model is validated with the numerical experiment. After that, the numerical tool developed is applied in a simulation of an accidental pipe leakage. The field near the leakage is simulated by Code\_Saturne. The results from Code\_Saturne is used as the input data for ADMS tool, a simulation tool for the particle dispersion in large scale. The results show that the particles are dispersed more than 1 km from the release source, which is in agreement with the distance observed. In perspective, the influences of different parameters as the wind field and the particle properties, on the agglomerate size and number distribution can be tested. An experiment of the microparticle jet is realized at INERIS in order to be able to assess the nanoparticle jet experiment in the laboratory scale.

Leung, Siu Ling. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 60-62). / Abstracts in English and Chinese. / Table of Contents / ACKNOWLEDGEMENT --- p.4 / List of Figures --- p.8 / Chapter 1. --- Introduction --- p.11 / Chapter 1.1 --- Background --- p.11 / Chapter 1.2 --- Project Objective --- p.12 / Chapter 1.3 --- Organization of the Thesis --- p.13 / Chapter 2. --- Literature Review --- p.14 / Chapter 2.1 --- Overview of the Colloidal Gold --- p.14 / Chapter 2.2 --- Dielectrophoresis (DEP) --- p.14 / Chapter 2.2.1 --- CM factor of Single Shell Model --- p.16 / Chapter 2.3 --- Double Layer and AC Electroosmosis --- p.18 / Chapter 2.3.1 --- Double Layer --- p.18 / Chapter 2.3.2 --- AC Electroosmosis --- p.19 / Chapter 2.4 --- Electrothermal Body Force --- p.19 / Chapter 3. --- Theoretical Analysis of DEP Manipulation --- p.21 / Chapter 3.1 --- Particle Manipulation by DEP Force --- p.21 / Chapter 3.2 --- Electric Induced Fluid Flow --- p.22 / Chapter 3.2.1 --- Double Layer and AC Electroosmosis --- p.22 / Chapter 3.2.2 --- Electrothermal Body Force --- p.24 / Chapter 3.3 --- DEP Manipulation against Fluid Flow --- p.25 / Chapter 4. --- Fabrication of AuNP based Sensors --- p.28 / Chapter 4.1 --- Fabrication of Arrays of Microelectrodes --- p.28 / Chapter 4.2 --- Formation of AuNP based Pearl Chains across Microelectrodes --- p.30 / Chapter 4.2.1 --- Formation Circuit --- p.30 / Chapter 4.2.2 --- Microspotting System --- p.31 / Chapter 4.2.3 --- Results and Discussion --- p.32 / Chapter 5. --- Exploring the Critical Parameters in Controlling AuNP Pearl Chain Formation (PCF) --- p.35 / Chapter 5.1 --- Exploring the Optimum Frequencies --- p.35 / Chapter 5.1.1 --- Analyzing the observation of pearl chain formation under specific frequency ranges --- p.36 / Chapter 5.1.2 --- Conclusion on the Optimum Frequency for PCF --- p.40 / Chapter 5.2 --- Exploring the Optimum Voltages --- p.41 / Chapter 5.3 --- Influence of the Particle size on the Formation Rate --- p.43 / Chapter 6. --- Characteristics of the AuNP based Pearl Chain --- p.44 / Chapter 6.1 --- I-V Characteristics --- p.44 / Chapter 6.2 --- Thermal Sensitivities --- p.45 / Chapter 7. --- Application of the AuNP based Sensor - Airflow Sensor --- p.48 / Chapter 7.1 --- Experimental Setup --- p.48 / Chapter 7.2 --- Experimental Results --- p.49 / Chapter 7.2.1 --- Sensor Response to Air --- p.49 / Chapter 7.2.2 --- Sensor Response to Nitrogen Gas --- p.50 / Chapter 7.2.3 --- Control Experiment --- p.51 / Chapter 7.3 --- Discussions --- p.53 / Chapter 7.3.1 --- Relationship between the Measured Electric Response and Temperature --- p.54 / Chapter 7.3.2 --- Pressure-Temperature Relationship of the Sensor --- p.55 / Chapter 8. --- Conclusion --- p.57 / Chapter 9. --- Future Work --- p.58 / Chapter 9.1 --- DEP Manipulation of 2nm diameter gold nanoparticles --- p.58 / References --- p.60 / List of Publications --- p.63 / APPENDIX-I / The Clausius-Mossoti (CM) Factor --- p.64 / Chapter I-1 --- The CM factor of homogeneous dielectric spheres --- p.64 / Chapter I-2 --- The CM factor of a single shell sphere --- p.65 / APPENPIX-II / Estimating the Minimum Voltage for Electrolysis by the Nernst Equation [39] --- p.67 / Chapter II-l --- Gibb´ةs Free Energy and the Nernst Equation --- p.67 / Chapter II-2 --- Minimum Voltage Required for Electrolysis of Water with Different pH --- p.67 / Appendix-III / Temperature-Voltage Relationship of the K-type Thermocouple [40] --- p.69 / Appendix-IV / Mathlab Program --- p.70 / Chapter IV-1. --- Fluid velocity induced by AC electroosmosis --- p.70 / Chapter IV-2. --- Voltage drop across the double layer --- p.70 / Chapter IV-3. --- Fluid velocity induced by electrothermal force --- p.71 / Chapter IV-4. --- CM Factor Simulation --- p.72 / Chapter IV-5. --- Particle velocity induced by DEP force --- p.73

MSc., Faculty of Science, University of the Witwatersrand, 2011 / This dissertation discusses the synthesis method known as laser pyrolysis. The theory on laser pyrolysis has been inferred since 1975, but it is insufficient in predicting the products that can be formed. This is due to the use of a laser, which leads to indecisive reaction pathways from precursor to product. In this work, the laser wavelength and power are varied to initiate a starting point in understanding the complex nature of the laser–precursor interaction, in addition to studying the resulting nanomaterial that is formed by the corresponding laser pyrolysis parameters. The results are justified based on linear and nonlinear optical processes, as well as photophysical and photochemical processes. Experiments to produce tungsten trioxide nanowires were conducted, but similar products could not be achieved, due to the difficulty in emulating ‘sensitive’ variables such as gas pressure and flow rates. However, it was discovered for the first time using this method that six-sided tungsten oxide “stars” can be grown.

Bismuth nanoparticles (Bi NPs) for use as an X-ray contrast material have gained significant traction in recent years due to the high atomic number and generally accepted biological tolerance of bismuth. However, to be considered a viable candidate for use in this application, water solubility is a necessity, which poses a challenge, since bismuth tends to readily oxidize. For this reason, research into the direct aqueous synthesis of Bi NPs is still in its infancy and can be very difficult, as described in Chapter 1. The remaining chapters of the thesis describe the direct aqueous synthesis of Bi NPs starting from a water-soluble bismuth tartrate (Bix(D-TA)y) precursor. Syntheses were carried out in an aerobic environment using a variety of pH and temperature conditions, from biologically compatible and inexpensive chemical reagents. Chapter 2 describes initial studies that sought to use glucose as the reducing agent and its oxidation product, gluconic acid, as the surface-stabilizing species. These studies showed glucose to be ineffective as a reducing agent for bismuth, as reactions progressed slowly and resulting particles lacked size and shape uniformity. The addition of a co-reductant, borane morpholine, was observed to result in an increased reaction rate, which yielded particles that exhibited improved size and shape uniformity. However, due to lack of surface stabilization, resulting particles were often observed to undergo oxidative dissolution upon quenching of the reaction. To better stabilize particle surfaces, glucose was replaced with 300 MW poly(ethylene glycol) (PEG 300). This change resulted in an overall decrease in the rate of reaction. The majority of syntheses using PEG as a surfactant resulted in Bi NPs that were equally unstable, as particle colloids were often observed to dissolve when quenching the reaction. For samples in which oxidative dissolution did not occur, the resulting Bi NPs were observed to be crystalline, aggregated nanostructures lacking any size or shape uniformity. For samples that underwent immediate oxidative dissolution and were afterwards left in a closed container absent of light for ~96 hours at room temperature, regrowth of Bi NPs was observed, where particle growth was thought to occur through a seed-mediated pathway. Through this seed-mediated growth method, resulting Bi NPs were observed to have significantly improved size and shape uniformity, as well as aqueous colloidal stability. Chapter 3 describes additional syntheses that yielded highly stable and relatively size uniform aqueous Bi NPs, which were prepared by chemical reduction of the same Bix(D-TA)y precursor. In these studies, hexamethylenediamine (HMD) was used as the surface-stabilizing agent in place of PEG 300. Analysis via FTIR revealed the presence of the ligand tartrate, which facilitated a simple acid/base titration method of particle isolation. With the addition of HCl, particle colloids would flocculate, allowing for ease of separation from the reaction medium by centrifugation. The Bi NPs could then be re-dispersed in aqueous solution with the addition of NaOH.

acase@tulane.edu / 1 / hong zhang

1 / Bing Shan

Purpose: The purpose of this study was to investigate possible effects of different microemulsion structure-types and types of monomer used on the formation of poly(alkylcyanoacrylate) nanoparticles, the entrapment into and release of insulin from these formulations as well as the bioactivity of the insulin upon intragastric delivery of the insulin-loaded nanoparticles dispersed in the microemulsion template. Methods: For two different microemulsion systems consisting of water, isopropyl myristate and either sugar-based surfactants or a macrogol glyceride-based surfactant-mixture, pseudo-ternary phase diagrams were established. Microemulsion samples therein were identified and characterised with polarising light microscopy, viscosity and conductivity measurements, differential scanning calorimetry, cryo-field emission scanning electron microscopy and self-diffusion nuclear magnetic resonance to determine the microemulsion structure-type. Nanoparticles were prepared from various microemulsion templates by interfacial polymerisation using ethyl (2) cyanoacrylate and butyl (2) cyanoacrylate. Particle size distribution and surface charge were measured using photon correlation spectroscopy and electrophoretic mobility. The morphology of the particles was characterised by scanning and transmission electron microscopy. Insulin was used as a model protein and the amount entrapped into and released from the particles was determined using a reverse phase HPLC assay. A diabetic rat model was employed to examine the bioactivity of different nanoparticle-microemulsion formulations with blood glucose and serum insulin as parameters measured by a proprietary glucometer and enzyme-linked immunosorbent assays, respectively. Results: The microemulsion system based on sugar-surfactants only formed solution-type microemulsions which could not all satisfactorily be used as a polymerisation template in the presence of insulin. The system however also showed an environmentally responsive gelling behaviour which may be suitable for depot delivery. The macrogol glyceride-based microemulsion system resulted in microemulsions with a continuous transition from water-in-oil to oil-in-water droplet-types via the bicontinuous structure-type. Microemulsion samples of each structure-type could serve as nanoparticle templates and resulted in particles with similar properties. Entrapment efficiency of insulin into the nanoparticles was template and monomer dependent. However, insulin was found to interfere with the polymerisation leading to a high variability in entrapment and release kinetics of these drug delivery systems. The degree of interference depended on the type of monomer and the size of the aqueous pseudo-phase of the microemulsion template. The interpretation of the results was further complicated by a possible competitive polymerisation initiation of insulin with the surfactant-mixture. Upon intragastric administration of the insulin-loaded nanoparticles dispersed in the oil-in-water microemulsion template a significant reduction in blood glucose could be achieved for up to 30 hours. However, no significant serum insulin concentration was detectable. Conclusions: Structurally different microemulsion templates resulting in nanoparticles with similar properties may offer increased formulation flexibility, in that a microemulsion template can be chosen which best solubilises the drug. Thus the microemulsions investigated in this thesis may serve as nanoparticle templates for designing entrapment processes for peptides and proteins with a simple one-step preparation by interfacial polymerisation. However, only if one was able to optimise and control the factors leading to the high entrapment and release variability these nanoparticles on the basis of microemulsions might be promising carriers for the oral delivery of peptide and protein bioactives.

Monolayer protected nanoparticles (MPNs) display fascinating size-dependent electronic, optical and catalytic properties. They are promising candidates to be used as building blocks with which to construct new generation nanoarchitectures and nanodevices for sensing, electronic and optoelectronic applications. The aggregation and dispersion of colloidal nanoparticles is one of the key issues closely related to their potential applications. Our knowledge of the colloid stability of nanoparticle dispersions with small sizes is still in its infancy, however, thymine is one of the bases in DNA, and is a pH sensitive and chromatic molecule. In the present study, thymine-functionalized self-assembled monolayer protected gold nanoparticles were synthesized. Their morphology and surface structure were characterized using TEM, UV-vis, FTIR, DSC-TGA and XPS techniques. The colloid stability of thymine-capped gold nanoparticle dispersions as a function of the type and concentration of monovalent salt, pH and particle size in alkaline aqueous solution were investigated. The manipulation of colloid stability with light was further explored. The results and conclusions are summarized inthis thesis.