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- Fornara, Andrea, 1980-
(författare)
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Magnetic nanostructured materials for advanced bio-applications
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the recent years, nanostructured magnetic materials and their use in biomedical and biotechnological applications have received a lot of attention. In this thesis, we developed tailored magnetic nanoparticles for advanced bio-applications, such as direct detection of antibodies in biological samples and stimuli responsive drug delivery system. For sensitive and selective detection of biomolecules, thermally blocked iron oxide nanoparticles with specific magnetic properties are synthesized by thermal hydrolysis to achieve a narrow size distribution just above the superparamagnetic limit. The prepared nanoparticles were characterized and functionalized with biomolecules for use in a successful biosensor system. We have demonstrated the applicability of this type of nanoparticles for the detection of Brucella antibodies as model compound in serum samples and very low detection limits were achieved (0.05 mg/mL). The second part is concerning an in-depth investigation of the evolution of the thermally blocked magnetic nanoparticles. In this study, the formation of the nanoparticles at different stages during the synthesis was investigated by high resolution electron microscopy and correlated to their magnetic properties. At early stage of the high temperature synthesis, small nuclei of 3.5 nm are formed and the particles size increases successively until they reach a size of 17-20 nm. The small particles first exhibit superparamagnetic behavior at the early stage of synthesis and then transform to thermally blocked behavior as their size increases and passes the superparamagnetic limit. The last section of the Thesis is related to the development of novel drug delivery system based on magnetically controlled release rate. The system consists of hydrogel of Pluronic FP127 incorporating superparamagnetic iron oxide nanoparticles to form a ferrogel. The sol to gel formation of the hydrogel could be tailored to be solid at body temperature and thus have the ability to be injected inside living biological tissues. In order to evaluate the drug loading and release, the hydrophobic drug indomethacin was selected as a model compound. The drug could be loaded in the ferrogel owning to the oil in water micellar structure. We have studied the release rate from the ferrogel in the absence and presence of magnetic field. We have demonstrated that the drug release rate can be significantly enhanced by use of external magnetic field decreasing the half time of the release to more than 50% (from 3200 to 1500 min) upon the application of the external magnetic field. This makes the developed ferrogel a very promising drug delivery system that does not require surgical implant procedure for medical treatment and gives the possibility of enhancing the rate of release by external magnetic field.
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| 2. |
- Wang, Xiaodi, 1981-
(författare)
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Ionic Conducting Composite as Electrolyte forLow Temperature Solid Oxide Fuel Cells
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Solid oxide fuel cells (SOFCs) are considered as one of the most promising powergeneration technologies due to their high energy conversion efficiency, fuel flexibilityand reduced pollution. The current SOFCs with yttria-stabilized zirconia (YSZ)electrolyte require high operation temperature (800-1000 °C), which not only hinderstheir broad commercialization due to associated high cost and technologicalcomplications. Therefore, there is a broad interest in reducing the operating temperatureof SOFCs. The key to development of low-temperature SOFCs (LTSOFCs) is to explorenew electrolyte materials with high ionic conductivity at such low temperature (300-600 °C).Recently, ceria-based composite electrolyte, consisting of doped cerium oxide mixedwith a second phase (e.g. Na2CO3), has been investigated as a promising electrolyte forLTSOFCs. The ceria-based composite electrolyte has shown a high ionic conductivityand improved fuel cell performance below 600 °C. However, at present the developmentof composite electrolyte materials and their application in LTSOFCs are still at an initialstage. This thesis aims at exploring new composite systems for LTSOFCs with superiorproperties, and investigates conductivity behavior of the electrolyte. Two compositesystems for SOFCs have been studied in the thesis.In the first system, a novel concept of non-ceria-salt-composites electrolyte, LiAlO2-carbonate (Li2CO3-Na2CO3) composite electrolyte, was investigated for SOFCs. TheLiAlO2-carbonate electrolyte exhibited good conductivity and excellent fuel cellperformances below 650 oC. The ion transport mechanism of the LiAlO2-carbonatecomposite electrolyte was studied. The results indicated that the high ionic conductivityrelates to the interface effect between oxide and carbonate.In the second system, we reported a novel core-shell samarium-doped ceria(SDC)/Na2CO3 nanocomposite which is proposed for the first time, since the interface isdominant in the nanostructured composite materials. The core-shell nanocompositeparticles are smaller than 100 nm with amorphous Na2CO3 shell. The nanocompositeelectrolyte was applied in LTSOFCs and showed excellent performance. Theconductivity behavior and charge carriers have been studied. The results indicated that H+conductivity in SDC/Na2CO3 nanocomposite is predominant over O2- conductivity with1-2 orders of magnitude in the temperature range of 200-600 °C. It is suggested that theinterface in composite electrolyte supplies high conductive path for proton, while oxygenions are most probably transported by the SDC nano grain interiors. Finally, a tentativemodel “swing mechanism” was proposed for explanation of superior proton conduction.
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| 3. |
- Li, Shanghua, 1981-
(författare)
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Engineering nanomaterials with enhanced functionality
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with the engineering of novel nanomaterials, particularly nanocomposites and nanostructured surfaces with enhanced functionalities. The study includes two parts; in the first part, an in situ sol-gel polymerization approach is used for the synthesis of polymer-inorganic hybrid material and its exceptional transparent UV-shielding effect has been investigated. In the second part, electrodeposition process has been adapted to engineer surfaces and the boiling performance of the fabricated nanostructured surfaces is evaluated. In the first part of the work, polymer-inorganic hybrid materials composed of poly(methylmethacrylate) (PMMA) and zinc compounds were prepared by in situ sol-gel transition polymerization of zinc complex in PMMA matrix. The immiscibility of heterophase of solid organic and inorganic constituents was significantly resolved by an in situ sol-gel transition polymerization of ZnO nanofillers within PMMA in the presence of dual functional agent, monoethanolamine, which provided strong secondary interfacial interactions for both complexing and crosslinking of constituents. In the second part of the work, nanoengineering on the surface of copper plates has been performed in order to enhance the boiling heat transfer coefficient. Micro-porous surfaces with dendritic network of copper nanoparticles have been obtained by electrodeposition with dynamic templates. To further alter the grain size of the dendritic branches, the nanostructured surfaces underwent a high temperature annealing treatment. Comprehensive characterization methods of the polymer-inorganic hybrid materials and nanoengineered surfaces have been undertaken. XRD, 1H NMR, FT-IR, TGA, DSC, UV-Vis, ED, SEM, TEM and HRTEM have been used for basic physical properties. Pool boiling tests were performed to evaluate the boiling performance of the electrodeposited nanostructured micro-porous structures. The homogeneous PZHM exhibited enhanced UV-shielding effects in the entire UV range even at very low ZnO content of 0.02 wt%. Moreover, the relationship between band gap and particle size of incorporated ZnO by sol-gel process was in good agreement with the results calculated from the effective mass model between bandgap and particle size. The fabricated enhanced surface has shown an excellent performance in nucleate boiling. At heat flux of 1 W/cm2, the heat transfer coefficient is enhanced over 15 times compared to a plain reference surface. A model has been presented to explain the enhancement based on the structure characteristics.
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