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Title:Control of micro- and nanostructure: I. polymer gas chromatography microcolumns and II. applications of ultrasound
Author(s):Hinman, Jordan J
Director of Research:Suslick, Kenneth S.
Doctoral Committee Chair(s):Suslick, Kenneth S.
Doctoral Committee Member(s):Gewirth, Andrew A.; Murphy, Catherine J.; Zimmerman, Steven C.
Department / Program:Chemistry
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Gas Chromatography
Sacrificial Template
Sonochemistry: Ultrasonic spray pyrolysis
Abstract:This thesis is comprised of two parts united by the general theme of making materials with micro- and nanostructural features. Being able to control the size and shape of materials is useful and important for a variety of different applications, including analytical materials, composites, and catalysts. The first part of this thesis describes the development of a new method to produce gas chromatography (GC) microcolumns with a polymer substrate. The second part of this thesis concerns the use of ultrasonic nebulization of solutions and suspensions both to produce unique nanostructured materials and to aid the study of nanomaterials. The first chapter introduces GC and GC capillary microcolumns. A brief history of the development of GC is given, along with some of the important concepts and equations that are relevant to the work presented here. Additionally, a brief review of the development and use of GC microcolumns is given. This includes the development of etched silicon microcolumns, strategies to improve microcolumn efficiency, strategies to apply the stationary phase to capillary columns, and the development of microcolumns with a polymer substrate. The latter part of the chapter details the production and performance of Rankin and Suslick’s disposable epoxy microcolumn. In Chapter 2, the ongoing problem of producing GC microcolumn channels with a circular cross-section is addressed by the development of a method utilizing a sacrificial fiber as a template for the microcolumn channel. It was found that polylactic acid fiber treated with a tin(II) oxalate catalyst performed well as a template for microcolumns as long as 1 m. Additionally, a method to apply a polydimethylsiloxane stationary phase by coating the sacrificial fiber prior to embedding it in the substrate epoxy is described. Microcolumns tested for the separation of alkane mixtures had an efficiency as high as 1800 plates m-1, but the microcolumns did not perform well at elevated temperatures. Further developments in polymer GC microcolumns prepared with a sacrificial fiber template are described in Chapter 3. The problem of temperature stability and substrate inertness is addressed by changing from an epoxy to a thermoset polyolefin based on the ring opening metathesis polymerization of polydicyclopentadiene using Grubbs’ catalyst. Furthermore, as a departure from traditional GC microcolumns, a three-dimensional helical configuration is used that removes the use of tight turns necessary for two-dimensional configurations, and it is demonstrated that the new configuration contributes to an improvement in separation efficiency. In contrast to coating the sacrificial fiber with the stationary phase, a dynamic coating method is used to apply the microcolumn stationary phase. The microcolumns demonstrate the ability to separate a sample of alkanes with an efficiency of 2300 plates m-1, and it is also shown that they can separate other analytes as well as performing separations at 100 °C. Additive manufacturing has become a production technique of interest in many fields, including chromatography. Chapter 4 describes the use of a commercially available reprap fused filament fabrication 3D printer to make a capillary GC microcolumn. The chapter discusses important design elements and challenges with using a 3D printer to make airtight capillary channels. Spiral and serpentine column designs were made and tested. The microcolumns were printed using PLA as the substrate material and coated with OV-101. In a separation of a mixture of alkanes, one serpentine microcolumn design had a separation efficiency of 700 plates m-1. The second part of the thesis begins in the fifth chapter. Chapter 5 gives a brief introduction and review of the use of ultrasound to make nanostructured materials. The first part of the chapter discusses the chemical effects of ultrasound, focusing on how ultrasonic cavitation can be used to produce nanomaterials. The second part of the chapter discusses the physical effects of ultrasound, including the formation of emulsions, sonofragmentation, and using ultrasound to nebulize liquids for spray pyrolysis. In Chapter 6 ultrasonic spray pyrolysis is used to produce metal borate microsopheres. Magnesium and calcium borate microspheres were produced as hollow spheres with very thin, smooth shells. Nickel and cobalt borate microspheres were also produced, and they exhibited slightly different morphology with rougher surfaces. The nickel and cobalt microspheres show some activity as catalysts for the oxygen evolution reaction. Potential applications for hollow microspheres are also discussed. The final chapter of the thesis demonstrates the use of ultrasonic spray techniques for the preparation of gold nanorod samples for transmission electron microscopy. The new ultrasonic technique is an alternative to drop-casting that deposits the nanoparticle suspension as a microspherical droplets. Due to the relative uniformity of ultrasonically generated droplets, it is also possible to adjust the concentration of the nanoparticle solution to control the average number of particles per droplet. It is demonstrated that this technique can be used to prepare samples on graphene-coated TEM grids. Additionally, the concentration of a nanoparticle solution can be estimated through the average number of nanoparticles per cluster, although other factors such as the surface chemistry of the nanoparticles may contribute to uncertainty in concentration estimation.
Issue Date:2018-07-05
Rights Information:Copyright 2018 Jordan Hinman
Date Available in IDEALS:2018-09-27
Date Deposited:2018-08

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