Fluorescence is the process by which a molecule absorbs light energy of a given wavelength and emits most of that energy as light of a longer wavelength. The rest of the energy is lost via non-photon emitting processes. Because fluorescence spectroscopy is both an absorption and emission process, it can be more selective than UV/visible absorption spectroscopy.
Robert Adam Kinney
The Photocatalyzed Decomposition of Methanol to Formaldehyde and Molecular Hydrogen
Abstract: The photocatalytic capabilities of tetrakis(m-diphosphito)diplatinate(II) (Pt2), Pt2/HgII, and Pt2/TlIII were determined with respect to the decomposition of methanol to formaldehyde and molecular hydrogen. The relationships between reaction time, d10 metal concentration, and formaldehyde concentration were examined to elucidate the primary catalytic species in each system, as well as to completely determine the formaldehyde generating processes that occur during the reaction. It was found that Pt2 acts photocatalytically on methanol to form formaldehyde. Addition of the d10 metals HgII and TlIII to methanolic Pt2 results in the formation of the photocatalytic species Pt2HgI and Pt2TlI, respectively. These species are in equilibrium with Pt2, meaning both contribute to the formation of formaldehyde during the reaction. Furthermore, Pt2TlI has a slower reaction rate relative to Pt2. A third process, the ligand to metal charge-transfer in the d10-solvato species, also results in formation of formaldehyde at a 1:1 molar ratio. The three processes combine to give the total formaldehyde yield for the system. Based on the observed degradation of the Pt2TlI photocatalyst over time, it is proposed that similar behavior occurs for the Pt2 system, except over a longer time frame. Such degradation does not occur for the Pt2HgI species. Rather, Pt2 is regenerated, as Hg0 is observed to form. Finally, preliminary studies on a hydrogen detection assay utilizing derivitization of Vaska’s complex were conducted. Early results suggest the method can reproducibly detect hydrogen, but the experimental setup needs to be refined to minimize atmospheric oxygen interference. The results of control experiments demonstrate that detection of hydrogen is possible with good sensitivity.