Acridine fluorescence lifetime

However, a study of a few dyes of higher fluorescence quantum yield in polymer microparticles did not show any change in the fluorescence lifetime even though the modification of the fluorescence spectra was observed [4]. In this work, a new molecule (9-amino acridine hydrochloride hydrate, 9AAHH) is reported in which we have observed the effect of MDR in both, the steady state spectra and the fluorescence lifetimes. The dephasing time of 9AAHH in polymer matrix at room temperature have been determined from this study. 

Fluorescence lifetime measurements are an important aspect of photophysical research. In the past few months the phase-shift measurement technique has become more widely used. This is largely due to the successful achievement of a multifrequency modulation apparatus. An apparatus made from commercially available components has been described and shown to have an accuracy of 10 ps. The performance was checked using mixtures of acridine and quinine sulphate and least-squares-ht procedures. A series of papers from the Illinois group give very detailed account of the state of the art and show the power of the method. The colour delay error arising from the wavelength error in photodetectors can be determined and fluorescence decay times can be obtained with an accuracy of a few picoseconds. ... 

A number of colloidal systems containing dyes have been investigated. The fluorescence lifetime of acridine orange has been measured in the SOS premicellar region. A short lifetime of less than 3ns is found for the monomer but the emission lifetime increases with dimer formation and SDS concentration. Quenching of 7-ethoxycoumarins by inorganic ions in, dye solubilizates in... 

The fluorescence lifetimes of acridine adsorbed on SG200A are given in Table 2, The fluorescence decay data of adsorbed acridine can be reasonably fitted as the two-component decay, except for the samples of the lowest coverage which have a shorter lifetime. The situation is quite similar to the case of adsorbed acridone and the short-lifetime component seems to originate from acridine molecules left on the silica gel surface without any... 

Fluorescence spectroscopy provides evidence for hydrogen bonding of catecholamines, resorcinolamines, and related compounds with phosphate and other anionic species in water. Siegmund and Bendig have measured the absorption and fluorescence spectra of acridine, A -methylacridine, and A -phenyl-acridine at 298 K in 35 solvents. The polarity of the excited states and intersystem crossing efficiency are related to solvent properties. Absorption and fluorescence spectra, fluorescence lifetimes, and fluorescence quantum yields for 5,10-dimethyl-5,10-dihydrophenazine (10), 9,14-dimethyl-9,14-dihydrodibenzo[fl,c]phenazine... 

Table 16 Dependence of fluorescence lifetime of acridine upon several parameters...

The mean fluorescence lifetime may also be determined by continuous intensity measurements, if the exciting light intensity is modulated at a high frequency. Fluorescence is excited by light modulated sinusoidally at a known frequency (ajln Hz). The emission is a forced response to the excitation, and is therefore modulated at the same frequency, but with a phase shift, due to the time-lag between absorption and emission. The intensities of the two beams are monitored by photomultipliers. The difference in phase (0) between the two intensities is determined electronically. The lifetime r is given by cox = tan<. The modulation frequency must be made comparable to the decay rate, e.g., around 30 MHz for a mean lifetime of 30 ns. Such frequencies can be achieved by using a hydrogen lamp actuated by a suitably modulated current source. Commercial equipment is available. The method has been applied to quinine sulphate, fluorescein, and acridine, for example, with a precision of 1-2%. It is especially useful for very short (sub-nanosecond) lifetimes. 

Heavy atom enhancement of intersystem crossing has been used to determine the mechanism of acridine photoreduction in ethanol.115 It was found that addition of sodium iodide decreased the fluorescence intensity and the rate of disappearance of acridine to the same extent, confirming that the singlet state is responsible for photoreduction. From the increase in triplet state absorption upon addition of iodide it was found that Of for acridine was 0.76. Thus the short singlet lifetime (0.8 nsec) of acridine is due to rapid inter-system crossing to unreactive triplet states. 

In their study of the fluorescence of acridine in hexane induced by a 0.1 mJ, 355-nm laser pulse, Barbara et. al. (26) demonstrated the sensitivity of this technique for the measurement of Tr and Tp. The best fit of the data, in this case, is a risetime, tr, which Is pulse-width limited and a decay lifetime, Tp, of 38 ps. These data which are illustrated in Figure 6 indicate that risetimes as short as 3 ps can be accurately determined, and decay lifetimes can be fitted with an accuracy of M0%. 

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