The work presented in this Thesis explores the properties and potential applications of superhydrophobic supports created using electroless deposition of rough silver onto copper wires which were then cut to expose hydrophilic tips. Small aqueous sample droplets were dispensed onto these supports and their Raman spectra were probed either directly or after drying to increase the concentration. It was found that the best way to dispense the droplets, (typically < 1 ul), was to use a pipette whose needle was itself superhydrophobic. When droplets of aqueous glucose, sucrose or mixtures of these were dried they formed viscous dome-shaped deposits in which the sugars were sufficiently concentrated to allow normal Raman measurements to be carried out. With melamine solutions and tear fluid the deposits were dry solids. Detection limits for sucrose, glucose and melamine were found to be 5 x 10-4 M, 2.5 X 10.3 M and 1 X 10.6 M, respectively. The concentration through evaporation approach was combined with surface enhanced Raman spectroscopy (SERS) by drying down droplets containing analyte plus Ag colloid onto the tips of the SHP supports or by making the tips themselves SERS-active by dipping them into AgN03(aq). These methods were tested with exhaled breath condensate (EBC) and adenosine triphosphate (ATP) solutions. The SHP supports could also be used simply as small sample holders, this was tested using colloid droplets to allow SERS of analytes to be recorded without evaporation. The small volumes of material used meant that the absolute detection limits of t he analytes which were investigated were ext remely low. For DNA the det ection limit was 75.9 ng, which is the amount of DNA found in 12 cells. For DPA the detection limit was the amount of material found in 18 spores but PLS calibration of the data allowed quantitation at < 10 spore levels.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:673794 |
| Date | January 2014 |
| Creators | Cheung, Melody |
| Publisher | Queen's University Belfast |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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