Browsing by Subject "Iron oxide"
Now showing 1 - 5 of 5
Results Per Page
Sort Options
Item Characterizing energy transfer using an infrared camera from a reacting nano-composite thermite embedded in a steel target(2009-05) Crane, Charles A.; Pantoya, Michelle; James, Darryl; Rivero, Iris V.A method to study energy transfer from a reacted thermite placed on a steel target substrate was presented as a function of thermite composition. A high speed infrared camera captured a temporally evolving thermal distribution through the substrate, while the thermite, which was placed in a v-notch, self propagated. Two thermite compositions were studied: Boron with Iron (III) Oxide (B-Fe2O3) and Aluminum with Iron (III) Oxide (Al-Fe2O3). A numerical model was developed to predict temperatures near the v-notch in order to estimate the amount of energy transferred into the steel by using a control volume energy balance. Results quantified the percent of the overall energy available from the chemical reaction that was conducted through the substrate and was compared to energy lost. The B-Fe2O3 reaction was more efficient in transferring energy into the steel, 46% of its heat of reaction, than Al-Fe2O3, 10% of its heat of reaction, based largely on the lower contribution of losses by radiation and convection. The Al-Fe2O3 reaction produced more gas by chemistry, 10% by mass, which transported more energy away from the v-notch region as compared to the non gas producing B-Fe2O3. The reaction times for Al-Fe2O3 propagation rate were roughly two to three times faster than the B-Fe2O3 which lowered the heating rate of the substrate. Much work had been performed that examine the combustion behaviors from a reacting thermite, but there are very few studies that attempt to quantify the energy transfer from a reacting thermite to a target. This diagnostic approach and numerical analysis was the first step towards quantifying energy transferred from a thermite into a target, and lost to the environment.Item Magneto-plasmonic nanoparticle platform for detection of rare cells and cell therapy(2014-08) Wu, Chun-Hsien, active 21st century; Sokolov, Konstantin V. (Associate professor); Dunn, Andrew; Emelianov, Stanislav; Yeh, Hsin-Chih; Zal, TomaszMagnetic and plasmonic properties combined in a single nanostructure provide a synergy that is advantageous in a number of biomedical applications, such as contrast enhancement in multimodal imaging, simultaneous capture and detection of circulating tumor cells, and photothermal therapy of cancer. These applications have stimulated significant interest in development of magneto-plasmonic nanoparticles with optical absorbance in the near-infrared region and a strong magnetic moment. In this dissertation, we addressed this need to create a novel immunotargeted magneto-plasmonic nanoparticle platform. The nanostructures were synthetized by self-assembly of primary 6 nm iron oxide core-gold shell particles, resulting in densely packed spherical nanoclusters. The close proximity of the primary particles in the nanoclusters generates a greatly improved response to an external magnetic field and strong near-infrared plasmon resonances. A procedure for antibody conjugation and PEGylation to the hybrid nanoparticles was developed for biomedical applications which require molecular and biocompatible targeting. Furthermore, we presented two biomedical applications based on the immunotargeted hybrid nanoparticle platform, including circulating tumor cell (CTC) detection and cell-based immunotherapy of cancer. In the CTC detection assays, rare cancer cells were specifically targeted by antibody-conjugated nanoparticles and efficiently separated from normal blood cells by a magnetic force in a microfluidic chamber. The experiments in whole blood showed capture efficiency greater than 90% for a variety of cancers. We also explored photoacoustic imaging to detect nanoparticle-labeled CTCs in whole blood. The results showed excellent sensitivity to delineate the distribution of hybrid nanoparticles on the cancer cells. Thus, these works paves the way for a novel CTC detection approach which utilizes immunotargeted magneto-plasmonic nanoclusters for a simultaneous magnetic capture and photoacoustic detection of CTCs. In another application, we introduced a novel approach to label cytotoxic T cells using the magnetic nanoparticles with an expectation to enhance T cell recruitment in tumor under external magnetic stimulus. A series of in vitro experiments demonstrated highly controllable manipulation of labeled T cells. Thus, these results highlight the promise of using our nanoparticle platform as a multifunctional probe to manipulate and track immune cells in vivo and further improve the efficacy of cell-based cancer immunotherapy.Item Photoswitching the donating and catalytic properties of N-heterocyclic carbenes and the design of functional co-polymers for stabilization of iron oxide nanoparticles(2013-05) Neilson, Bethany Margaret; Bielawski, Christopher W.In an effort to develop broadly applicable photoswitchable catalysts, we have reported a method for modulating N-heterocyclic carbene (NHC) donicity using light by incorporating a photochromic diarylethene (DAE) into the backbone of a NHC scaffold. UV irradiation of 4,5-dithienylimidazolone or an analogous NHC-Ir(CO)₂Cl complex effected a photocyclization between the two thiophene rings, which led to a change in the electron donating ability of the NHC scaffold. Subsequent exposure to visible light reversed the photocyclization reaction. The concept of photo-modulating NHC donicity in this manner enabled photoswitchable NHC organocatalysis. The catalytic activity of a DAE-annulated imidazolium pre-catalyst in transesterification and amidation reactions was successfully switched between the active and nearly inactive states ([kappa]vis/[kappa]UV = 100) upon alternate UV ([lambda]irr = 313 nm) or visible ([lambda]irr > 500 nm) irradiation. The photoswitchable NHC organocatalysis was later extended to facilitating ring-opening polymerizations of cyclic esters, the rates of which were controlled via external light stimuli. Additionally, a photochromic dithienylethene-annulated N-heterocyclic carbene (NHC)-Rh(I) complex was synthesized and enabled photoswitching of the catalytic activity in series of hydroboration reactions. All of the examples demonstrate extremely rare instances of photomodulating a catalyst's activity by tuning its electronic properties. Furthermore, by taking advantage of the versatility of NHCs in both organo- and organometallic catalysis, we have developed novel photoswitchable catalysts for a variety of applicable transformations. Nanoparticles that can be transported in subsurface reservoirs at high salinities and temperatures are expected to have a major impact on enhanced oil recovery and electromagnetic imaging. We have developed an approach that will facilitate nanopaticle transport through porous media at high salinity by adsorbing or grafting rationally designed co-polymers on platform nanoparticles. Notably, co-polymers of acrylic acid with either 2-acrylamido-2-methylpropanesulfonate or styrenesulfonate have been electrostatically adsorbed or covalently grafted onto iron oxide nanoclusters. The presence of sulfonate groups on the iron oxide surface enabled long-term colloidal stability of the particles in extremely concentrated brine (8% wt. NaCl + 2% wt. CaCl₂) at elevated temperatures (90 °C) and minimized their adsorption on model mineral surfaces.Item Reaction controlled kinetic assembly of small gold nanoclusters with high NIR extinction(2011-08) Willsey, Brian William; Johnston, Keith P., 1955-; Milner, Thomas ENanoclusters with sizes of ~50nm with high NIR extinction at wavelengths beyond 800 nm are of interest in various fields including biomedical optical imaging, microelectronics, plasmonic sensors, and catalysis. Herein we report gold nanoclusters with hydrodynamic diameters of ~50 nm composed of ~10 nm primary particles. The kinetically controlled assembly of clusters occurs simultaneously with the reaction to synthesize the primary particles. The clustering is induced by attractive van der Waals forces that dominate over the steric and electrostatic repulsive forces present. Stability is provided using a single, biocompatible polysaccharide in either carboxymethyl dextran or dextran. High NIR shifts of the surface Plasmon resonance are achieved through close interparticle spacings of primary particles, deviations in morphology from that of a sphere of primaries, and the surface roughness that results from the clustering process. The cluster size is mediated by controlling the relative nucleation and growth rates of primary particles using a moderate reducing agent in NH2OH and glucose at pH 8.7. It will be shown that cluster size is also dependent on Au concentrations in solution. Maintaining low Au concentrations will allow for smaller clusters. In particular, the small size and high NIR extinction at longer wavelengths (800-1100 nm) makes these particles of interest for optical imaging applications in biology, as particles with a hydrodynamic diameter of ~50 nm have long blood lifetimes.Item Textured thin metal shells on metal oxide nanoparticles with strong NIR absorbance and high magnetization for imaging and therapy(2010-12) Ma, Li, doctor of chemical engineering; Feldman, Marc David; Johnston, Keith P., 1955-; Milner, Thomas E.; Sokolov, Konstantin V.; Mullins, C. B.; Hwang, Gyeong S.The ability of sub 100 nm nanoparticles to target and modulate the biology of cells will enable major advancements in cellular imaging and therapy in cancer and atherosclerosis. A key challenge is to load an extremely high degree of targeting, imaging, and therapeutic functionality into small, yet stable particles. A general mechanism is presented for thin autocatalytic growth on nanoparticle substrates (TAGS), as demonstrated for a homologous series of < 5 nm textured Au coatings on < 42 nm iron oxide cluster cores. Very low Au supersaturation levels are utilized to prevent commonly encountered excessive autocatalytic growth that otherwise produce thick shells. The degree of separation of nucleation to form the seeds from growth is utilized to control the morphology and uniformity of the thin Au coatings. The thin and asymmetric Au shells produce strong near infrared (NIR) absorbance with a cross section of ~10⁻¹⁴ m², whereas the high magnetic content per particles provides strong r2 spin-spin magnetic relaxivity of 200 mM⁻¹s⁻¹. TAGS may be generalized to a wide variety of substrates and high energy coatings to form core-shell nanoparticles of interest in a variety of applications as diverse as catalysis and bionanotechnology. High uptake of the nanoclusters by macrophages is facilitated by the dextran coating, producing intense NIR contrast both in cell culture and an in vivo rabbit model of atherosclerosis. A novel conjugation technique further allows covalent binding of anti-epidermal growth factor receptor (EGFR) monoclonal antibody (Ab) to the nanoclusters for highly selective targeting to EGFR over expressing cancer cells. AlexaFluor 488 tagged Ab nanocluster conjugates were prepared to correlate the number of conjugated Abs with the hydrodynamic diameter. The high targeting efficacy was evaluated by dark field reflectance imaging and atomic absorbance spectrometry (AAS). Colocalization of the nanoparticles by dual mode in-vitro imaging with dark field and fluorescence microscopy demonstrates the Abs remained attached to the Au surfaces. The extremely high curvature of the Au shells with features below 5 nm influence the spacing and orientations of the Abs on the surface, which has the potential to have a marked effect on biological pathways within cells. These targeted small multifunctional nanoclusters may solve some key molecular imaging challenges for cancer and atherosclerosis.