Date of Award
Doctor of Philosophy (PhD)
Molecular Science and Nanotechnology
In this dissertation, four nanoparticle reaction schemes were developed as substrates for halochromic dyes or nucleic acids. The reaction schemes include the use of two substrates: silica nanoparticles and halloysite nanotubes. The protocols can incorporate silica (SiO2) nanoparticles and halloysite aluminosilicate (AlO2SiO2) nanotubes due to the presence of silane groups on the surface of either substrate. The reaction schemes are presented along with detailed protocols which were written to facilitate both reproducibility and to serve as an aid to further study and for easy modification of the protocol to suit a researcher's needs. The data is discussed in the materials section to annotate the stages of synthesis as well as the response of the nanoparticles to varying conditions of pH in both a broad range and a near neutral range.
The first particle scheme was designed to create a particle to measure pH using neutral red, a halochromic ionophore with sensitivity to near neutral pH values. Neutral red has a primary amine which is not required for its halochromic response but is suitable for covalent binding to an aldehyde. The particle synthesis involved functionalization of the inorganic silica surface with an amine. This amine was then covalently bound to a dialdehyde, glutaraldehyde, creating an imine and resulted in a terminal aldehyde functional group on the surface of the particle. The final step of the synthesis was to bind neutral red by its primary amine to the aldehyde functional group. This created a pH sensitive nanoparticle. The particles were stable and did not exhibit leaching or loss of dye. The particles were sensitive to near neutral pH and observation of UV-vis spectra they could be used to discern changes in pH at a large range by observation of the spectral bands of the protonated and deprotonated states of the halochromic dye.
The second particle developed was a derivation of the first particle. Instead of using a dialdehyde to link two amines, a silane coupling agent was used to provide aldehydes to the surface of the particles. The aldehyde functional group was then linked to the amine functional group of the halochromic dye, neutral red. This protocol produced stable nanoparticles with pH sensitivity, was steps shorter, required fewer reagents, which reduced the cost of development and increased the facility of the protocol.
The third particle developed used an organosilane cross linking agent to produce nanoparticles made of covalently bound silica and the halochromic dyes, neutral red and Nile blue. The particles were highly responsive to changes in pH. Analysis of UV-vis spectral data showed a broad sensitivity to pH by changes in the spectral bands.
The fourth particle developed used the reaction scheme from the second particle. The surface of the inorganic particles was functionalized with aldehyde groups. The aldehyde modified particles were then shown to have the ability to covalently bind nucleic acids and nitrogenous bases.
The synthesis of these particles is presented along with the supporting data. Further areas of study and possible future work are discussed.
Johnston, William, "" (2019). Dissertation. 836.