ULTRAVIOLET-VISIBLE FLUORESCENCE SPECTROSCOPY OF SELECTED POLYAROMATIC HYDROCARBONS AND ORGANOMETALLICS ON HEXAGONAL GRAPHITE AND BORON-NITRIDE

Several organic and organometallic compounds including polynuclear aro matic hydrocarbons (PAHs), anthracene, pyrene, and coronene and the or ganometallics zinc etioporphyrin and zinc phthalocyanine, adsorbed on the basal planes of highly ordered pyrolytic graphite (HOPG), a semime tal, and highly ordered pyrolytic boron nitride (HOPBN), an insulator, were studied using ultraviolet-visible fluorescence spectroscopy to e xamine surface interactions. The organometallics showed definite subst rate effects with fluorescence quenching on HOPG but not HOPBN, which is consistent with the different electronic properties of these two su bstrates, but which seems not to have been previously reported for the se molecules. Zinc etioporphyrin also showed a red shift and spectral distortion on HOPG. The PAHs, as expected from the literature, showed no substrate-specific effects.