Room-temperature phosphorescence of 6-bromo-2-naphthol included in β-cyclodextrin in the presence of cyclohexane

The formation constant for a 1:1 binary complex between 6-bromo-2-naphthol (6B2N) and β-cyclodextrin (CD) in aqueous solution was determined by both absorptimetric and fluorimetric methods. Room-temperature phosphorescence (RTP) was induced by adding small amounts of different apolar liquids as the third component, with cyclohexane producing the strongest enhancement effect. Microcrystals formed in the ternary system seem to be necessary for obtaining phosphorescence emission. The deoxygenation by flowing nitrogen does not improve the RTP signals, while the addition of sodium sulfite as chemical deoxygenant produces quenching of the signals. The calibration graph for 6-bromo-2-naphthol in the presence of β-CD and cyclohexane was linear for the range of concentrations between 0.04 and 1 μg ml−1, with a detection limit of 0.04 μg ml−1.