Date of Degree
PhD (Doctor of Philosophy)
Larsen, Sarah C.
First Committee Member
Gillan, Edward G.
Second Committee Member
Tivanski, Alexei V.
Third Committee Member
Stone, Elizabeth A.
Fourth Committee Member
Cwiertny, David M.
Mesoporous silica has shown great potential as an adsorbent for environmental contaminants and as a host for imaging and therapeutic agents. Mesoporous silica materials have a high surface area, tunable pore sizes and well defined surface properties which are governed by the surface hydroxyl groups. Surface modification of the mesoporous silica can tailor the adsorption properties for a specific metal ion or a small drug molecule by providing better sites for chelation or electrostatic interactions.
Iron oxide / mesoporous silica core shell materials couple the favorable properties of both the iron oxide and mesoporous silica materials. The core-shell materials have higher adsorption properties compared to the parent material. With magnetic iron oxide nanoparticle cores, an additional magnetic property is introduced that can be used as magnetic recovery or separation. Heavy metals such as Chromium (Cr) and Arsenic (As) discharged from residential and environmental sources pose a serious threat to human health as well as groundwater pollution.
In this thesis, iron oxide nanoparticles and nanofibers were coated with mesoporous silica and functionalized with (3-aminopropyl)triethoxysilane (APTES) using the post synthesis grafting method. The parent and the functionalized magnetic silica samples were characterized using powder X-ray diffraction (pXRD), thermal gravimetric analysis (TGA), Fourier Transform Infrared (FTIR) spectroscopy and nitrogen adsorption desorption isotherms for surface area and pore volumes. These materials were evaluated for Cr(III) and As(III)/As(V) adsorption from aqueous solutions in the optimum pH range for the specific metal. The aminopropyl functionalized magnetic mesoporous silica displayed the highest adsorption capacity for Cr(III) and Cu(II) of all the materials evaluated in this study. The high heavy metal adsorption capacity was attributed to a synergistic effect of iron oxide nanoparticles and amine functionalization on mesoporous silica as well as a judicious choice of pH. Modified magnetic mesoporous silica material was also found to have high adsorption capacity for high and low pH aqueous solutions of Uranium (VI).
Tuning the loading and release of a small drug molecule (5-FU) onto these iron oxide/ mesoporous silica core-shell materials was also investigated. The polarity of the solvent used to load 5-FU onto the host had an impact not only on the loading but also on the release percentage of 5-FU. The synthesis of a novel core-shell material with a hematite nanofiber core and a SBA type mesoporous silica shell was also explored.
Mesoporous silica is an inorganic silicate material with pores ranging from 2-50 nm. The porosity results in very large surface areas which make these materials ideally suited as hosts for functional molecules such as small drug molecules or as adsorbents for environmental contaminants. Using chemical modification schemes, mesoporous silica can be tailored for adsorption of specific guest molecules or contaminants.
Nanocomposites are materials in the 100 nm size range which combine the properties of two materials. In this work, iron oxide nanoparticles and nanofibers were used as a core material and a shell of mesoporous silica was added to form a core-shell nanocomposite. These materials couple the favorable properties of both iron oxide and mesoporous silica, including the high adsorption properties and porosity of mesoporous silica and the magnetic properties of the iron oxide core. It has higher adsorption properties compared to the parent materials.
These materials were evaluated for Chromium and Arsenic adsorption as well as Uranium removal from aqueous solutions. The aminopropyl functionalized magnetic mesoporous silica displayed the highest adsorption capacity for Chromium(III) and it was attributed to a synergistic effect of iron oxide nanoparticles and amine functionalization on mesoporous silica as well as a judicious choice of pH.
Tuning the loading and release of a small chemotherapeutic drug molecule (5-FU) onto these iron oxide/ mesoporous silica core-shell materials was also investigated. The polarity of the loading solvent had an impact not only on the loading but also on the release percentage of 5-FU. The synthesis of a novel core-shell material with a hematite nanofiber core and a SBA type mesoporous silica shell was also explored.
Core/shell, Drug Delivery, Heavy Metals, Iron Oxide, Mesoporous Silica, Nanocomposites
xxv, 289 pages
Includes bibliographical references (pages 270-289).
Copyright © 2016 Shani Nirasha Egodawatte
Egodawatte, Shani Nirasha. "Environmental and biomedical applications of iron oxide/ mesoporous silica core-shell nanocomposites." PhD (Doctor of Philosophy) thesis, University of Iowa, 2016.