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Solubilization of Probe Molecules

Various spectroscopic techniques and probes have been used to investigate solubilization of probe molecules, mostly using UV/visible spectroscopy, fluorescence spectroscopy, ESR spectroscopy [64, 74, 217, 287] and NMR-spectro-scopy [367-369]. Fluorescence spectroscopy is particularly versatile [370], as various static and dynamic aspects can be covered by studying excitation and emission spectra, excimer or exciplex formation, quantum yields, quenching, fluorescence life-times, fluorescence depolarization, energy transfer etc. [Pg.34]

Pyrene derivatives are the widest used probes for qualitative solubilization [365] by virtue of the solvatochromic shifts of the absorption bands [255], the excimer formation [145,186], the polarity dependent quantum yields [197] and fluorescence life-times [185-187, 196, 197, 202, 215, 292], and the pyrene fluorescence fine structure [65, 74,78,103,112,167, 224, 363, 371] the intensity ratio of the fluorescence bands I at 372 nm and III at 383 nm is a convenient measure for the polarity of the environment of the pyrene label ( py -scale I/III values increase with polarity, cf. Fig. 27). As, however, the fluorescence of pyrene is very sensitive to the experimental set-up [372], absolute I/III values reported by different groups are difficult to compare. [Pg.34]

The following will focus on studies exploring the nature of the solubilization sites. Studies concerning dynamics in polymeric micelles , the overall shape and aggregation numbers are included in Sects. 3.5 and 4.2. [Pg.34]

The simplest information obtained by qualitative solubilization is the existence (or the absence) of hydrophobic microdomains, using probes which are sensitive to the polarity of the environment. Such solubilization experiments are [Pg.34]

If the probes are slightly water-soluble, an additional problem arises from partitioning of the probes between the aqueous and the micellar phase . Thus sometimes the assumed CMC s, because of changing I/III values of pyrene fluorescence [213, 353], may be apparent only because of the unfavourable partition of the solubilizate between the aqueous and the micellar phase at low soap concentrations [154, 292]. [Pg.35]


Basically, the aggregation of the hydrophobic tails in polysoaps is assumed to take place intramolecularly. In particular the solubilization of probe molecules has been employed to verify the intramolecular aggregation, demonstrating the lack of an equivalent of the critical micelle concentration CMC up to extreme dilutions [50, 51, 53,65,72,76-78,106,112,113,126,145,186,196,197,245,343, 361]. Even more convincing proof was obtained by using covalently fixed probe molecules [152], because the problems of the probe s partition between the... [Pg.43]


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