| Popis: |
This dissertation contains the following sections. Chapter 1 contains a detailed description of the theory of thin layer chromatography (TLC). Chapter 2 describes the benefits and practical considerations of elevated temperatures in liquid chromatography (LC). The porous graphitic carbon (PGC) I modified as part of my work is often used in elevated temperature LC. Chapter 3 shows a thermodynamic analysis of chromatographic retention at elevated temperature, and Chapter 4 contains a closer look at the van 't Hoff equation in LC and how it can be used in retention modeling. In Chapter 5, I describe a new procedure for microfabricating TLC plates that avoids the volume/feature distortions that occurred in our first microfabrication. The primary advance of this work was the priming of the carbon nanotube (CNT) forests with chemical vapor deposition (CVD) carbon and atomic layer deposition (ALD) alumina, which permitted effective ALD-like deposition of SiO2. Chapter 6 describes advancements in the microfabrication process of TLC, which excluded the use of the CVD carbon and Al2O3 coating as described in Chapter 5. The use of ozone, to lightly oxidize the CNT surface, primed the material for direct ALD deposition. Chapter 7 gives a detailed surface analysis of the microfabrication process up to and including the CNT forest. It was noticed that a channeling effect was present during Rutherford backscattering analysis of the CNTs. Additionally, characterization of CNTs using time-of-flight secondary ion mass spectrometry in the negative ion mode showed an odd-even effect for a homologous series of carbon, where the even moieties had a stronger signal. Chapter 8 describes the functionalization of PGC with di-tert-amyl peroxide (DTAP) and its effect on increasing the chromatographic performance as seen by a reduction in the tailing factors of test analytes. Chapter 9 -- 13 are detailed X-ray photoelectron analyses of the thin films and CNTs used in producing microfabricated TLC plates. |
