We have developed a portable breath acetone analyzer using cavity ringdown spectroscopy (CRDS). The instrument was initially tested by measuring the absorbance of breath gases at a single wavelength (266 nm) from 32 human subjects under various conditions. A background subtraction method, implemented to obtain absorbance differences, from which an upper limit of breath acetone concentration was obtained, is described. The upper limits of breath acetone concentration in the four Type 1 diabetes (T1D) subjects, tested after a 14 h overnight fast, range from 0.80 to 3.97 parts per million by volume (ppmv), higher than the mean acetone concentration (0.49 ppmv) in non-diabetic healthy breath reported in the literature. The preliminary results show that the instrument can tell distinctive differences between the breath from individuals who are healthy and those with T1D. On-line monitoring of breath gases in healthy people post-exercise, post-meals and post-alcohol-consumption was also conducted. This exploratory study demonstrates the first CRDS-based acetone breath analyzer and its potential application for point-of-care, non-invasive, diabetic monitoring.
The fundamental photophysical properties of three symmetrically substituted 3,9-perylene analogues were examined in a diverse range of solvents. All three compounds exhibited solvent-dependent fluorescence quantum yield, which was lower than that of perylene or its diimides. Whilst the absence of a large excited state dipole moment suggests that there is no preferential charge accumulation in one side of the molecules, the data suggest that intramolecular electron transfer occurs and that such an event causes additional photochemical mechanisms in chlorinated compounds where the fluorescence quantum yield is lower than in all other solvents and the values of the fluorescence decay change significantly. The dyes could be an interesting new class of fluorescence tags for labeling biomolecules and as dyes for organic photovoltaic materials.
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