Materials Chemistry Commons^™

Continuous Stationary Phase Gradients For Planar And Column Chromatography, Veeren Dewoolkar

Theses and Dissertations

Surfaces that exhibit a gradual change in their chemical and/or physical properties are termed as surface gradients. Based on the changes in properties they are classified either as physical or chemical gradients. Chemical gradients show variations in properties like polarity, charge, functionality concentration and have found potential applications in fields of biology, physics, biosensing, catalysis and separation science. In this dissertation, surface gradients have been prepared using controlled rate infusion (CRI).

CRI is a simple method in which a surface gradient is formed by carrying out the infusion of organoalkoxysilane in a time-dependent fashion using a set infusion rate. Depending …

Fabrication Of Multifunctional Nanostructured Porous Materials, Ahmed A. Farghaly

Theses and Dissertations

Nanostructured porous materials generally, and nanoporous noble metals specifically, have received considerable attention due to their superior chemical and physical properties over nanoparticles and bulk counterparts. This dissertation work aims to develop well-established strategies for the preparation of multifunctional nanostructured porous materials based on the combination of inorganic-chemistry, organic-chemistry and electrochemistry. The preparation strategies involved one or more of the following processes: sol-gel synthesis, co-electrodeposition, metal ions reduction, electropolymerization and dealloying or chemical etching. The study did not stop at the preparation limits but extended to investigate the reaction mechanism behind the formation of these multifunctional nanoporous structures in order …

Systematic Postsynthetic Modification Of Nanoporous Organic Frameworks And Their Performance Evaluation For Selective Co2 Capture, Timur Islamoglu

Theses and Dissertations

Porous organic polymers (POPs) with high physicochemical stability have attracted significant attention from the scientific community as promising platforms for small gas separation adsorbents. Although POPs have amorphous morphology in general, with the help of organic chemistry toolbox, ultrahigh surface area materials can be synthesized. In particular, nitrogen-rich POPs have been studied intensively due to their enhanced framework-CO₂ interactions. Postsynthetic modification (PSM) of POPs has been instrumental for incorporating different functional groups into the pores of POPs which would increase the CO₂ capture properties. We have shown that functionalizing the surface of POPs with nitro and amine groups …

Laser Vaporization Controlled Condensation And Laser Irradiation In Solution For The Synthesis Of Supported Nanoparticle Catalysts, Vitaly Kisurin Mr.

Theses and Dissertations

Solid catalyst supports of SiOx-RGO (Reduced Graphene Oxide) and UiO-67 (Universitet i Oslo) have been successfully synthesized and were loaded with palladium nanoparticles to test for a series of heterogeneous reactions. The SiOx/RGO catalysts were synthesized through laser ablation of silicon and graphite oxide micron powder and UiO-67 metal-organic framework (MOF) was synthesized through mixing of precursors with DMF/HCl solution and washing the resultant powder from impurities. The SiOx/RGO supports were later impregnated with palladium precursors which were then subject to Microwave Irradiation (MWI). The UiO-67 framework was impregnated with palladium precursors and was irradiated with pulsed Nd:YAG 532 nm …

Synthesis, Surface Functionalization, And Biological Testing Of Iron Oxide Nanoparticles For Development As A Cancer Therapeutic, Stanley E. Gilliland Iii

Theses and Dissertations

Iron oxide nanoparticles are highly researched for their use in biomedical applications such as drug delivery, diagnosis, and therapy. The inherent biodegradable and biocompatible nanoparticle properties make them highly advantageous in nanomedicine. The magnetic properties of iron oxide nanoparticles make them promising candidates for magnetic fluid hyperthermia applications. Designing an efficient iron oxide nanoparticle for hyperthermia requires synthetic, surface functionalization, stability, and biological investigations. This research focused on the following three areas: optimizing synthesis conditions for maximum radiofrequency induced magnetic hyperthermia, designing a simple and modifiable surface functionalization method for specific or broad biological stability, and in vitro and in …

Heteroatom-Doped Nanoporous Carbons: Synthesis, Characterization And Application To Gas Storage And Separation, Babak Ashourirad

Theses and Dissertations

Activated carbons as emerging classes of porous materials have gained tremendous attention because of their versatile applications such as gas storage/separations sorbents, oxygen reduction reaction (ORR) catalysts and supercapacitor electrodes. This diversity originates from fascinating features such as low-cost, lightweight, thermal, chemical and physical stability as well as adjustable textural properties. More interestingly, sole heteroatom or combinations of various elements can be doped into their framework to modify the surface chemistry. Among all dopants, nitrogen as the most frequently used element, induces basicity and charge delocalization into the carbon network and enhances selective adsorption of CO₂. Transformation of …

Colloidal Synthesis And Optical Characterizations Of Semiconductor Nanocrystals From Nontoxic Elements, Minh Q. Ho

Theses and Dissertations

To date, the search efforts have shifted from the toxic II-VI, III-V and IV-VI semiconductors to more environmentally friendly materials. Among Group II-V semiconductors, Zn₃P₂ has shown to be a more benign option, similar to Group IV (Ge, Si) materials, for future applications in photovoltaics and optoelectronics. This work is dedicated to the development of wet-chemical synthetic routes of (1) Zn₃P₂ and (2) Group IV (Ge, Si, Si_1-xGe_x) nanocrystals with precise control over composition, crystal structure, size and dispersity by adjusting different reaction parameters such as temperature, time and solvent …

Diazaborole Linked Porous Polymers: Design, Synthesis, And Application To Gas Storage And Separation, Zafer Kahveci

Theses and Dissertations

The synthesis of highly porous organic polymers with predefined porosity has attracted considerable attention due to their potential in a wide range of applications. Porous organic polymers (POPs) offer novel properties such as permanent porosity, adjustable chemical nature, and noteworthy thermal and chemical stability. These remarkable properties of the POPs make them promising candidates for use in gas separation and storage. The emission of carbon dioxide (CO₂) from fossil fuel combustion is a major cause of global warming. Finding an efficient separation and/or storage material is essential for creating a cleaner environment. Therefore, the importance of the POPs …

Modified Seed Growth Of Iron Oxide Nanoparticles In Benzyl Alcohol: Magnetic Nanoparticles For Radio Frequency Hyperthermia Treatment Of Cancer, Stanley E. Gilliland Iii

Theses and Dissertations

Iron oxide nanoparticles have received sustained interest for biomedical applications as synthetic approaches are continually developed for precise control of nanoparticle properties. This thesis presents an investigation of parameters in the benzyl alcohol synthesis of iron oxide nanoparticles. A modified seed growth method was designed for obtaining optimal nanoparticle properties for magnetic fluid hyperthermia. With a one or two addition process, iron oxide nanoparticles were produced with crystallite sizes ranging from 5-20 nm using only benzyl alcohol and iron precursor. The effects of reaction environment, temperature, concentration, and modified seed growth parameters were investigated to obtain precise control over properties …

Fabrication And Characterization Of High Surface Area Gold Electrodes, Madhura S. Damle

Theses and Dissertations

High surface area gold electrodes are very good substrates for biosensors, catalysis and drug delivery. Their performance is characterized by good sensitivity, low detection limit and high signal. As a result, extensive research is being carried out in this field using different approaches of fabrication to generate high surface area porous electrodes of different morphology, pore size and structure. The morphology of the electrodes can be changed based on whether the approach involves a template or not, types of metal deposition, method and time of dealloying etc. The deposition of metal can be carried out using various approaches such as …

Advanced Radiometry For High Discrimination Explosive Fireball Discrimination, Steven E. Slagle

Theses and Dissertations

The high explosive fireball phenomenological model for the mid wave infrared spectrum, developed by AFIT, performs classification from spectral signatures was modified to use radiometric intensities. Five bands were sequentially fit to derive the five physical fit parameters describing the fireball's temperature, size, soot absorption coefficient within 16% and emissions from the H₂O and CO₂ concentrations within 333% of the spectral model. This was improved by changing the model's band sizes, center, and fitting methods where all five fit parameters were matched to within 17% of spectral model. This demonstrated that a combination of radiometric intensities could …

Investigation Of Electrical And Optical Properties Of Bulk Iii-V Ternary Semiconductors, Travis C. Gomez

Theses and Dissertations

Bulk grown III-V ternary semiconductors of In_0.08Ga_0.92Sb and In_0.15Ga_0.85As were investigated through Hall-effect and photoluminescence measurements to determine carrier concentration, mobility, sheet resistivity, and luminescence spectrum. In the past, epitaxial layers of ternary compounds have been grown on binary compound substrates, and thus very limited lattice matched ternary alloys were available. Recently, bulk grown ternary substrates have been developed, and it has presented a renewed interest in using these substrates to grow high quality ternary compounds for use in many next generation optoelectronic devices. The results of photoluminescence (PL) study for the …

Nondestructive Evaluation Of Aircraft Composites Using Terahertz Time Domain Spectroscopy, Christopher D. Stoik

Theses and Dissertations

Terahertz (THz) time domain spectroscopy (TDS) was assessed as a nondestructive evaluation technique for aircraft composites. Material properties of glass fiber composite were measured using both transmission and reflection configuration. The interaction of THz with a glass fiber composite was then analyzed, including the effects of scattering, absorption, and the index of refraction, as well as effective medium approximations. THz TDS, in both transmission and reflection configuration, was used to study composite damage, including voids, delaminations, mechanical damage, and heat damage. Measurement of the material properties on samples with localized heat damage showed that burning did not change the refractive …

Single -Walled Carbon Nanotubes Separation And Redox Chemistry And Their Applications For Optical Biosensing And Scaffold Materials, Xiaomin Tu

Theses and Dissertations

Single-walled carbon nanotubes (SWNTs) have drawn great attention worldwide for their unique electronic, mechanical and optical properties. This dissertation details studies of some of the most important areas including: (1) Single-stranded DNA (ssDNA) assisted separation of SWNTs using high performance liquid chromatography; (2) Optical sensitivity and kinetic studies of redox reaction of ssDNA functionalized SWNTs with hydrogen peroxide (H 2 O 2 ); (3) Effects of Ag + on the redox reaction of ssDNA-encased SWNTs with hydrogen peroxide; (4) Single-walled carbon nanotube based optical sensors for DNA detection; and (5) SWNTs as scaffolds for promoting stem cell differentiation into bone …

Investigation Of The Platinum-Rich Portion Of The Platinum-Tantalum Phase Diagram, Bob Dean Browning

Theses and Dissertations

The Pt-Ta binary system was investigated at two isotherms;1000°C and 1500°C, and at eleven alloy compositions in the range of 50 to 100 atomic percent platinum. The alloys were examined by x-ray diffraction and metallography. Three intermetallic compounds, Pt₂Ta, Pt₃Ta, and Pt₄Ta were found to exist in this composition range. The Pt₄Ta intermetallic appeared only at the 1500°C isotherm. Platinum dissolved tantalum substitutionally to 90 atomic percent at 1500 °C and to approximately 80 atomic percent at 1000 °C.