The Detection of Elemental Mercury by Gold Nanoparticles
ProQuest, 2007 - 662 pages
In the past decade, as mercury pollution has come under increasing scrutiny by public policy analysts and environmental regulators, nanoscale science and engineering has emerged as an enabling technology and driven tremendous technological change in the field of sensors. In this thesis, use is made of the unique optical properties of gold nanoparticles to develop an environmental sensor capable of detecting elemental mercury at sub ppm levels in aquatic and atmospheric environments. The electron confinement and inner field enhancement that occurs in gold nanoparticles give rise to a strongly absorbing Lorentzian type surface plasmon resonance (SPR) band in the visible spectrum that makes them particularly suited to this application. Several types of gold particle, varying in size, shape, stability, and surface constitution, are investigated and exposed to mercury whilst in solution, i.e., in colloidal form, and immobilized to the surface of transparent quartz substrates using organosilane functional molecules, e.g., aminopropyl-trimethoxysilane (APTMS). UV-vis spectroscopy and TEM imaging are used to characterize changes to the morphology of the gold particles after exposure to mercury, and shifts in the SPR maximum position (wavelength and absorbance) are used to quantify the amount of mercury present.
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600 Wavelength nm Absorbance at 550 absorption spectra aggregation amount of mercury anhydrous APTES APTMS modified quartz blue-shift Bohren and Huffman calculated carrier stream chemical colloidal gold colloidal gold solution colloidal solution condensation cuvette dehydroxylated derivatization process detection dielectric function diluted sample discrete dipole approximation DMAP gold Drude model elemental mercury equation evaporation chamber exposed to elemental exposure to mercury extinction gas phase gold nanoparticles gold particles HWHM hydrolysis hydroxylated illustrated in figure imaginary components immobilized increase laser mercury atoms mercury in air methoxy Mie theory mins minutes modified quartz substrate MPTES NaBH4 nanotechnology NaSCN optical properties organosilanes particle concentration particles/mL photon energy rinsed saturated shown in figure silane silane molecules silanol silica sodium borohydride sodium citrate sodium thiocyanate solvent spectrum SPR band SPR maximum SPR wavelength substrate surfaces surface plasmon resonance technique temperature UV-vis absorption UV-vis spectra UV-vis spectrometer Vansant vapor phase vacuum vapor pressure