The introduction of ionization under ambient conditions has greatly simplified mass spectrometric analysis. Over past decade, ambient ionization mass spectrometry (MS) methods have revolutionized the way complex samples are analyzed under environmental conditions without requiring, in most cases, any sample pretreatment. Ambient ionization MS gained popularity among other analytical techniques due to its simplicity and its suitability for analysis of small and large molecules. However, ambient ionization methods can suffer from low accuracy and sensitivity due to matrix effects and interferences within complex samples, as well as from poor ionization efficiency. Matrix effects in ambient ionization are usually caused by ion suppression and may depend on different factors, e.g. matrix-to-analyte concentration ratios, proton affinities of analyte and matrix species. To overcome these challenges, in this thesis we present a new approach where a probe is used both as a direct sampling device and as an efficient ambient ionization source. This approach leverages high surface area gold electrodes, fabricated through low-cost bench-top fabrication methods and functionalized using self-assembled alkyl thiol monolayers, as functional conductive sampling probes (FCSPs) for the extraction and concentration of analytes from a sample solution. FCSPs loaded with the targeted analytes were then used to demonstrate a new and highly efficient ionization approach, called Primary Ion Mass Spectrometry Source (PIMSS). In this approach, following capture, the bound analytes are directly desorbed into the mass spectrometer, where ionization is achieved solely through the extraction voltage applied to the probe. 3D-printing was used to design an interface to couple FCSPs to the mass spectrometer. In this work, we discuss a detailed method development and optimization stage and present capabilities of the proposed assay. / Thesis / Master of Science (MSc)

The goal of this work was to quantify the mechanical properties of cellulose nanocrystal (CNC)-based thin films using a polystyrene (PS) structuring approach. This structuring approach was used to biaxially wrinkle CNC-polymer and all-CNC films, in order to assess how changes in the film fabrication process affected the elastic modulus of these films. All films were prepared on pre-stressed PS substrates and structured by heating them above the glass transition temperature of PS, which caused the substrates to shrink and the films to wrinkle biaxially. CNC-polymer films were prepared using the layer-by-layer approach, where three parameters were modified to obtain films of varying compositions: 1) type of polymer (xyloglucan, XG, or polyethyleneimine, PEI), 2) polymer concentration (0.1 wt% or 1 wt%), and 3) film thickness (i.e., number of deposited bilayers). After these films were structured, their elastic moduli were calculated to be 70 ± 2 GPa for CNC-XG0.1, 72 ± 2 GPa for CNC-PEI0.1, and 32.2 ± 0.8 GPa for CNC-PEI1.0 films, indicating that the mechanical properties of CNC-polymer films changed with film composition. This structuring method was also found to provide a humidity-independent measurement of the modulus due to the irreversible nature of the wrinkling. Next, to prepare all-CNC films, CNC suspensions were evaporated under conditions designed to control the film thickness (using 0.005 wt% – 8 wt% CNC suspensions) and CNC nanoparticle orientation (chiral nematic, isotropic, or uniaxial). Suspensions were dried slowly under vacuum, quickly by heating, or by spin-coating to form films with chiral nematic, isotropic, or uniaxial (radial) CNC orientations, respectively. Following structuring, these wrinkled films showed unique morphologies that changed with nanoparticle orientation, suggesting that their mechanical properties are dependent on the CNC orientation within the films. The work presented in this thesis implies that the mechanical properties of films fabricated from hygroscopic bio-based nanomaterials can be assessed in a humidity-independent way by using the structuring method presented. Quantifying the mechanical properties of these films is critical to assess the potential applications of CNCs, where CNC-based materials may be used in developing paper-based electronics, extracellular matrix mimics, and plant cell wall mimics. / Thesis / Master of Science (MSc)