Selective Fluorescence Quenching of Polycyclic Aromatic Hydrocarbons by Aliphatic Amines

Abstract

The ability of primary, secondary, and tertiary mono- and diamines to serve as fluorescence quenchers for polycyclic aromatic hydrocarbons (PAHs) has been evaluated in acetonitrile and methanol. In general, the efficiency of quenching increases with the electron-donating ability of the amine and with the number of amine groups. The selectivity for nonalternant PAHs relative to the alternant isomers appears to decrease as the quenching efficiency increases. Nevertheless, all of the amines exhibit greater selectivity than 1,2,4-trimethoxybenzene, a previously characterized selective quencher for nonalternant PAHs. The experimentally measured rate constants for dynamic quenching show good agreement to those predicted by Rehm-Weller electron-transfer theory in the solvent acetonitrile. In contrast, the rate constants in methanol are anomalously low and do not conform well to Rehm-Weller theory. Presumably this is due to explicit hydrogen bonding between the solvent and quencher, which decreases the concentration of the free amine that is available for fluorescence quenching.

Fluorescence studies of pyrene-labelled, pH-responsive diblock copolymer micelles in aqueous solution

“…Presumably this trend reflects the fact that quenching occurs at high pH as the deprotonated tertiary amine groups come into contact with the fluorescent label. (Tertiary amines are known to be efficient fluorescence quenchers [52,53].) Although we cannot, with confidence, assign the three exponential terms to specific physical species, valuable information can nonetheless be derived from the data by calculating an average fluorescence lifetime,…”

“…The current data do not follow this trend. Deprotonation of the tertiary amine units occurs at high pH [38], which presumably then act as efficient contact quenchers [52,53] of the excited state of the pyrene label. As the degree of deprotonation increases with increasing pH, this leads to a higher quenching efficiency and a resultant decrease in ht f i. Consequently, the current lifetime data are somewhat inconclusive as regards the conformation of the block copolymer.…”

“…Since tertiary amines are known [52,53] to be efficient fluorescence quenchers, a reduction in t f would be expected. To prove the hypothesis that the amine units quench the fluorescence of the labelled block copolymer triethylamine was added (at various concentrations) to py-PDEA 30 ePDMA 130 (0.004 g/l) in aqueous solution: a significant degree of quenching was indeed observed with a k q value of ca.…”

Investigation of common fluorophores for the detection of nitrated explosives by fluorescence quenching

“…The selected fluorophores have lower toxicity than pyrene to reduce health and waste disposal concerns that may arise from their routine use. The fluorophores have conjugated, electron-rich structures with significant electron-donating capabilities to facilitate ion-pair formation during the quenching process [16,48]. Another relevant selection criterion is a high quantum efficiency, which allows high sensitivity to be achieved with a low fluorophore concentration.…”

Physicochemical Properties of Protoporphyrin IX by Metal Ions in Acetonitrile-Water Mixture Solution

“…Quenching processes involve a chemical interaction of the fluorophore and quencher. 22,23 One such process is static quenching, whereby a nonfluorescent ground-state complex is formed between a groundstate fluorophore and quencher. Another important quenching mechanism is collisional or dynamic quenching, which involves the collision and subsequent formation of a transient complex between an excited state fluorophore and a ground-state quencher.…”