Time-resolved luminescence quenching

Time-resolved luminescence quenching measurements using the probe Tb(pyridine-2,6-dicarboxylic acid)i and the quencher bromophenol blue show the existence of micellar clusters in AOT-based w/o microemulsions. The fast exchange appearing over several microseconds was attributed to intracluster quenching, whereas the slow exchange on the millisecond time scale was attributed to intercluster exchange [243]. 

For each solution in the Cr + G series, Table 8.2 (1) measure the UV-vis spectrum to obtain the absorbance A at Aex, and (2) measure an emission spectrum and obtain the integrated emission intensity, I. Also, prepare a solution having [G] the same as the last in your series (Table 8.2), but with no chromium complex. This will serve as a control sample. Save your sample solutions for time-resolved luminescence quenching if you are conducting these experiments (see below). Save all UV-vis and luminescence spectra files that you acquire—they may be useful for data analysis. 

The most important applications of luminescence probing in microemulsions involve the deactivation dynamics or excitation energy transfer properties of the excited states. With a brief flash of light a population of excited species is created in the sample, and the subsequent deactivation is observed over time. The decay of the excited probe, and the fluorescence spectrum, may depend on the interactions with the environment, which reveal useful information. In time-resolved luminescence quenching (TRLQ), however, it is the interaction of the probe with another added component, a quencher, that is studied. This method is dealt with here. For micellar systems, several publications have already discussed it in both experimental and theoretical detail [1-6]. 

The main technique used to look at exchange processes in equilibrium systems employs labeled surfactants, particularly with ESR spectroscopy. Fox s ESR study [92] of a paramagnetic surfactant in micellar solution was the first of its kind, and yielded a solution-micelle monomer exchange rate of 10 s" at room tanperature for 2,2,6,6-tetramethylpiperidine-oxidedodecyldimethylammonium bromide. These techniques, along with time-resolved luminescence quenching, have shown that the entry of surfactant molecules into micelles is near-diffusion controlled, whereas loss from micelles is rate limiting, and hence kinetically controlled [93]. A decade later (1981), Bolt and Turro [94] were able to find the separate exit and reentry rate constants for 10-(4-bromo-l-naphthoyl)decyltrimethylammonium bromide as 3.2 x 10 s and 5.7 x 10 mok s", respectively. 

As studies of surfactant self-assemblies developed during 1970 to 1980, other methods, such as time-resolved luminescence quenching (and the related methods of flash photolysis and pulse radiolysis), nuclear magnetic resonance (NMR),... 

TEL time-resolved luminescence TRLQ time-resolved luminescence quenching FP flash photolysis TROS time-resolved optical spectroscopy. 

Clustering of aggregates order of ms Time-resolved luminescence quenching 117-119... 

Time-resolved luminescence quenching has been used to investigate the exchange rates of solubilizates in the cluster regime of AOT/water/oil systems, Intermicellar exchange... 

Almgren M, Mays H (1999) Time-resolved luminescence quenching in microemulsions. In Kumar P, Mittal, KL (eds) Handbook of microemulsion science and technology. CRC Press,... 

---