UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.
More information is available at Theses and Dissertations at University of Maryland Libraries.
Browse
2 results
Search Results
Item DEVELOPMENT OF ANALYTICAL METHODS FOR CHARACTERIZATION OF NANOPARTICLES FOR BIO-MEDICAL AND ENVIRONMENTAL APPLICATION BY ION MOBILITY-ICP-MS(2017) Tan, Jiaojie; Zachariah, Michael R.; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The development of nanotechnology necessitates appropriate tools for nanoparticle characterization to assure product quality, evaluate safety and facilitate manufacturing. The properties of interest particularly relevant to nanomedicine and environmental ecotoxicology include size, shape, aggregation, concentration, dissolution, surface chemistry, and composition etc. Engineered nanoparticles in a complex matrix, at realistic concentration are two of the major challenges for analytical scientist. Potential transformation of pristine engineered nanomaterials when put in contact with either biological or environmental media further complicate the analytical task. In this dissertation, I aim to optimize and extend the application of novel hyphenated instruments consisting of differential mobility analysis (DMA) and inductively coupled plasma-mass spectrometry (ICP-MS) for real time size classification and elemental detection in biomedical and environmental fields. I have applied DMA-ICP-MS in quantitatively characterizing anti-tumor drug delivery platform to assist design and performance evaluation. Optimal balance among drug loading, stability and release performance was achieved and evaluated by DMA-ICP-MS. I have further developed a novel analytical methodology including DMA and ICP-MS operating in single particle mode (i.e. spICP-MS). I successfully demonstrated and validated the method for accurate and simultaneous size, mass and concentration measurement by NIST reference materials. DMA-spICP-MS was shown with the capability to characterize nanoparticle aggregation state and surface coating. In addition, this technique was shown to be useful for real-world samples with high ionic background due to its ability to remove dissolved ions yielding a cleaner background. Given this validated DMA-spICP-MS method, I applied it to quantifying the geometries of seven gold nanorod samples with different geometries. It was demonstrated that DMA-spICP-MS can achieve fast quantification of both length and diameter with accuracy comparable with TEM analysis. This method provided the capability to separate nanorods from spheres quantifying the geometry for each population. Finally, an interesting open and high-order rosette protein structure was investigated by electrospray-DMA. The staining procedure was optimized and effect of electrospray process on protein particle structure was evaluated. Protein particle after electrospray was largely maintained. Mobility simulation by MOBCAL showed close matches with experimental data and enabled peak assignment to various particle assembly structures.Item QUANTIFYING PARTICLE PROPERTIES FROM ION-MOBILITY MEASUREMENTS(2012) Li, Mingdong; Zachariah, Michael R.; Chemical Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Nanoparticles have received considerable interest due to the wide variety of potential applications in biomedical, optical, and electronic fields. However, our capabilities for quantitatively charactering these materials, for example in number concentration or shape are limited. The objective of this work is to develop experimentally verified theories to quantify particle properties from aerosol based ion-mobility measurement. The use of aerosol tools is predicated on the idea that these methods offer the best chance for quantification, due to a better understanding of the physics of ion transport in the gas phase. Nevertheless this does not preclude us from using these techniques to characterize particles in liquids as will be show in the first part of this work which resolves problems associated with generating an aerosol from colloidal suspensions. In this dissertation I resolve the problem of artificial "droplet induced aggregation" during electrospray which can corrupt the eventual determination of particle size. I develop an experimentally verified statistical based model, to determine and correct this undesired artifact. Furthermore, I have found that this nominally undesired artifact can be used in a beneficial way that allows one to determine the absolute number concentration of nanoparticles in solution, without the need for calibration particles. Mobility is one of the most important and fundamental properties of a particle. However most particle characterization approaches interpret the results of mobility measurement in the context of spherical particle transport. I have undertaken to systematically explore the mobility properties of non-spherical particles. In this dissertation I develop a theory to quantify the effect of orientation on the mobility and the dynamic shape factor of charged axially symmetric particles in an electric field. The experimental results of well-defined doublets of NIST traceable size standard 127nm, 150nm, 200nm and 240nm PSL spheres are shown to be in excellent agreement with the expected values based on my theory. More general new theories of the mobility of nonspherical particles are also proposed and compared with current theories. I also propose a new instrument, a pulsed differential mobility analyzer (PDMA), to obtain shape information by measuring the electrical mobility under different electric fields.