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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

The clean preparation of nanocomposite materials : a supercritical route

Morley, Kelly Sarah January 2003 (has links)
No description available.

Surface Roughening Enhancement on Sapphire

Chan, Min-Chao 27 July 2010 (has links)
We discuss the self-assembled Ni nanoparticles as the etching mask process and produce patterned sapphire substrate in this study. In the Ni nanoparticles formation process, we focus on two major factors which make the Ni films transform into Ni ball, (1)annealing temperature, (2) film thickness. In the experiment, we deposit 2000Ǻ SiO2 on sapphire substrate, and use the E-gun to deposit 100~200Ǻ Ni film. After the Ni film deposition, we use the rapid thermal annealing at 900oC standing for 60sec, and make the Ni film transform into Ni spherical calotte which is resulting from the Ni film cohesive force. In the SiO2 etching process, we use CF4, 20sccm as reactive gas and the Ni calotte as etching mask to form SiO2 nanopillars. Then, we mixed Cl2 and SiCl4 reactive gas, 5sccm and 20sccm, and use SiO2 nanopillars as the etching mask in the dry etching process to form patterned sapphire substrate. We obtain the optimum rapid thermal annealing for self-assembled Ni calotte at 100, 200Ǻ Ni film. We got the patterned sapphire substrate nanopillars at density of 1.59x109cm-2, average height ~64.3nm, average diameter ~106nm, and density of 6.20x108cm-2, average height ~160nm, average diameter ~193nm for 100, and 200Ǻ Ni film process condition, respectively. We use 160nm sapphire nanopillars to increase 18.0-10.3% scattering light for 350~450nm blue light LED application.

Engineering Nanoparticle-Protein Associations for Protein Crystal Nucleation and Nanoparticle Arrangement

Benoit, Denise 06 September 2012 (has links)
Engineering the nanoparticle - protein association offers a new way to form protein crystals as well as new approaches for arrangement of nanoparticles. Central to this control is the nanoparticle surface. By conjugating polymers on the surface with controlled molecular weights many properties of the nanoparticle can be changed including its size, stability in buffers and the association of proteins with its surface. Large molecular weight poly(ethylene glycol) (PEG) coatings allow for weak associations between proteins and nanoparticles. These interactions can lead to changes in how proteins crystallize. In particular, they decrease the time to nucleation and expand the range of conditions over which protein crystals form. Interestingly, when PEG chain lengths are too short then protein association is minimized and these effects are not observed. One important feature of protein crystals nucleated with nanoparticles is that the nanoparticles are incorporated into the crystals. What results are nanoparticles placed at well-defined distances in composite protein-nanoparticle crystals. Crystals on the size scale of 10 - 100 micrometers exhibit optical absorbance, fluorescence and super paramagnetic behavior derivative from the incorporated nanomaterials. The arrangement of nanoparticles into three dimensional arrays also gives rise to new and interesting physical and chemical properties, such as fluorescence enhancement and varied magnetic response. In addition, anisotropic nanomaterials aligned throughout the composite crystal have polarization dependent optical properties.

Magnetic induction heating of superparamagnetic nanoparticles for applications in the energy industry

Davidson, Andrew Marshall 23 April 2013 (has links)
A novel method of delivering thermal energy efficiently for flow assurance and for improved heavy oil production/transport is described. The method, an improved form of magnetic induction heating, uses superparamagnetic nanoparticles that generate heat locally when exposed to a high frequency magnetic field oscillation, via a process known as Neel relaxation. This concept is currently used in biomedicine to locally heat and ablate cancerous tissues. Dependence of the rate of heat generation by commercially available, single-domain Fe3O4 nanoparticles of ~10 nm size, on the magnetic field strength and frequency was quantified. Experiments were conducted for nanoparticles dispersed in water, in hydrocarbon liquid, and embedded in a thin, solid film dubbed “nanopaint”. For a stationary fluid heat generation increases linearly with loading of nanoparticles. The rate of heat transfer from the nanopaint to a flowing fluid was up to three times greater than the heat transfer rate to a static fluid. Dispersion models indicated that the thermal conductivity of the dispersing fluid did not greatly influence the heat transfer results, whereas differences in size between hydrophilic and hydrophobic nanoparticles did. The model of static fluid in a nanopainted tube verified that the nanoparticle loading in the paint was ~30wt% and the nanopaint thickness was 600 µm. The model of flowing fluid in a nanopainted tube showed that internal mixing in the system, even at laminar flow rates, improved heat transfer to the center of the flowing fluid. A waveguide model verified the feasibility of using steel hydrocarbon transport pipelines as a means to guide electromagnetic energy to target heating locations along the pipeline if the energy is transmitted at frequencies above the cutoff frequency. Heating of nanopaint with external magnetic field application has immediate potential impact on oil and gas sector, because such coating could be applied to inner surfaces of pipelines and production facilities. A nanoparticle dispersion could also be injected into the reservoir zone or gravel pack near the production well, so that a thin, adsorbed layer of nanoparticles is created on pore walls. With localized inductive heating of those surfaces, hydrate formation or wax deposition could be prevented; and heavy oil production/transport could be improved by creating a ‘slippage layer’ on rock pore walls and inner surfaces of transport pipes. / text

Determination of nanoparticle size and surface charge in suspension by an electroacoustic method

Wroczynskyj, Yaroslav 08 January 2015 (has links)
An apparatus intended to measure the pressure oscillations generated by nanoparticle suspensions in response to an AC electric field was designed and made operational. Electroacoustic measurements were performed on nanoparticle systems covering a range of particle sizes and zeta-potentials, determined using typical particle characterization techniques. The results of the electroacoustic experiments were mapped to the hydrodynamic size and zeta-potentials of the various nanoparticle systems. It was determined that while the electroacoustic technique can be used successfully to measure the motion of nanoparticles in response to an AC electric field, additional improvements to the electroacoustic apparatus are required to allow for a more rigorous mapping of electroacoustic measurements to particle hydrodynamic size and zeta-potential.

Synthesis of Silver Nanowires by TiO2 Nanoparticles

Wang, Ching-Wen 23 June 2008 (has links)
¡@Silver nanowires prepared by the the reduction of AgNO3 at low temperature with thermocatalystic biphase (anatase and brookite phases) TiO2 nanoparticles are described. Furthermore, the possible mechanism to grow silver nanowires without the help of the Ag seed and capping reagent is proposed. ¡@Firstly, the amorphous TiO2 nanoparticles prepared by sol-gel method were spin-coated on the silicon wafer to form amorphous TiO2 matrix. Then an aqueous AgNO3 (1 &#x00B5;L 0.7 M) solution was dropped on the amorphous TiO2 matrix. Following the heat treatment at 200 ¢XC for 8 h, the silver nanowires (length~10 &#x00B5;m, line width~100 nm) were grown on the silicon wafer. We found that amorphous phase of TiO2 was changed to the anatase and brookite phases during the thermal reduction of the aqueous solution of AgNO3. ¡@Silver nanowires were characterized as f.c.c. structure by XRD. The TiO2 particles play an important role in providing electrons and holes for redox reaction and nucleation. With the controlling of the heating temperature and the amount of AgNO3, the silver nanowires were selectively grown in one dimension with large energetic surface. A combination of HR-TEM imaging and selected area electron diffraction reveals that the growing direction for the Ag wires is <011>.

Development of novel additives for analysis of proteins by capillary electrophoresis

Lin, Chin-yu 18 July 2008 (has links)
The simultaneous separation of anionic and cationic proteins has been achieved by addition of high concentration of poly(diallyldimethylammonium chloride) (PDDAC) in capillary electrophoresis. A capillary was filled with PDDAC so that it would act as ion-pair reagents in the separation of anionic proteins. On the other hand, the PDDAC can also be used as coating additives for the analysis of cationic proteins. Increasing the concentration of PDDAC in the separation buffer had the ability to improve the separation efficiency, change the electrophoretic mobility, and alter the separation selectivity; however, this was not true in the case of analyzing proteins by using the PDDAC larger than 1.6%. By both using a buffer containing 1.6% PDDAC and applying pH-stepwise techniques, 13 proteins with a wide range of pI (4.7¡V11.1) and molecular masses (6.5¡V198.0 kDa) could be separated within 30 min in a single run. In addition to this separation, we observed notonly more peaks from alph-chymotrypsinogen A and aprotinin but also the bovine serum albumin (BSA) dimer and trimer. The second part describes a method for enrichment and separation of acidic and basic proteins using the centrifugal ultrafiltration followed by polyelectrolyte-filled capillary electrophoresis. In order to improve stacking and separation efficiencies of proteins, the separation buffer containing 1.6% poly(diallyldimethylammonium chloride) was added with gold nanoparticles (AuNPs), poly(ethylene oxide), cetyltrimethyl ammonium bromide, and poly(vinyl alcohol). As a result, the use of AuNPs as additives exhibited better efficiency in separation, stacking and analysis time. Even for large-volume samples (110 nL), the separation efficiencies of acidic and basic proteins remained greater than 104 and 105 plates/m, respectively. To further enhance detection sensitivity, protein samples were enriched using the centrifugal ultrafiltration, followed by our proposed stacking method. As a result, the detection sensitivity was improved up to 314-fold as compared with normal hydrodynamic injection. Additionally, the limits of detection at a signal-to-noise of 3 for most proteins are down to nanomolar range. We have validated the application of our method by means of analyses of 50 nM lysozyme in saliva samples. The proposed method was also successfully applied to the analyses of egg-white proteins, which have large differences in molecular weight and pI.

The study of photo-controlled light absorption of gold nanoparticle

Shih, Ching-jen 26 August 2009 (has links)

Effect of nanoparticles on the properties of masonry mortars and assemblages at a cold temperature

Kazempour, Hooman January 2014 (has links)
Cold weather masonry construction is a major concern for contractors as they either have to implement heating practices for laying and curing masonry systems or postpone the construction to warmer periods. This can lead to loss of productivity rate and delays in construction schedules with associated extra costs. This thesis explores a novel approach for mitigating the adverse effects of cold weather on masonry construction in early fall periods through the application of nano-alumina (NA) and nano-silica (NS) in mortar joints. The assessment criteria were based on the fresh properties, hardened properties and microstructural features of mortar mixtures and mechanical behaviour of concrete masonry prisms at early and later ages. Various test results show that NS can be successfully used to minimize the adverse effects of cold temperature on mortar joints by speeding up the hydration of cement, shortening the setting time, and increasing the strength up to 72 h.

Octaarginine Labelled 30 nm Gold Nanoparticles as Agents for Enhanced Radiotherapy

Latimer, Caitlin 03 December 2013 (has links)
Traditional radiation therapy is limited by the radiotoxic effects on surrounding healthy tissues. This project investigated the use of a gold nanoparticle (AuNP) conjugated to a cell-penetrating peptide (CPP) to increase tumour cell death during radiotherapy by maximizing the cellular import of the gold nanoparticles. ~8300 octaarginine CPPs were coupled per 30 nm AuNP through poly(ethylene glycol) spacers (AuNP-PEG-CPP). The CPPs enhanced the internalization of the AuNPs into three human breast cancer cell lines by a factor &gt;2 as compared to untargeted AuNPs. Cells were treated with AuNP-PEG-CPP for 24 hours, prior to radiotherapy and their long-term proliferation was assessed in clonogenic assays. The increased internalization of AuNPs by the CPPs resulted in greater cell death following exposure to 300 kVp radiotherapy, by a dose enhancement factors between 1.3 and 2.1 depending on the cell line. These findings illustrate the potential of using AuNP-CPPs to enhance radiotherapy in patients.

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