Fluorescence of 6-Methoxyquinoline, Quinine, and Quinidine in Aqueous Media

Quinine doped hybrid sol–gel coatings for wave guiding and optical applications

“…Quinine is known to exhibit intense fluorescence with emission in the blue region of the spectrum upon excitation with UV light [20,[32][33][34][35]. Figure 6 presents the photoluminescence spectrum of silica with different quinine concentrations (l-15%wt).…”

Determination of the photoluminescence quantum yield of dilute dye solutions (IUPAC Technical Report)

“…The absolute Φ f of some of these commercially available dyes were only very recently re-measured [36,38,40,42,44], thereby also providing a complete purity analysis. Popular standards include quinine sulfate with all its problematic features-complicated ground-state chemistry [70,71], dependence of emission band position on excitation wavelength [72]-together with fluorescein and rhodamine 6G and rhodamine 101 recommended for the vis region [36,38,41,44]. The wavelength dependence of Φ f of quinine sulfate was only recently re-measured, thereby underlining its potential as quantum yield standard [42].…”

Fluorescence studies of some protonated cinchona alkaloids in polymers

“…The pK values for quinine, quinidine and 6-methoxy quinoline are 4.34, 4.34 and 5.13 and corresponding pK* are 9.7, 9.9 and 11.6, respectively [2]. An exhaustive temperature dependent fluorescence study of quinine sulfate (QS), quinidine and 6-methoxy quninoline (6 MQ) in acidic aqueous solution was carried out by Pant et al [24,27] and they suggested that around 160 K, a rapid relaxation process (charge transfer from methoxy group to the quinoline ring) other than the solvent relaxation occurs.…”

“…Later, many workers questioned its utility as fluorescence standard for quantum yield [18][19][20] and decay time measurements [21][22][23][24]. Since then, many studies on the fluorescence features as well as conformation of cinchona alkaloids have been reported [1][2][3][4][5][6][7][8][9].…”

“…Cinchona alkaloids are photolabile and photo-induced modifications in their case have long been known [1][2][3][4][5][6][7][8][9]. Besides wellknown importance in drug industries [10][11][12], cinchona alkaloids are endowed with numerous interesting applications in various fields, e.g.…”