Fluorescence blob model

Keywords Pyrene aggregates and excimer Associative thickeners Fluorescence Blob Model Model free analysis Fluorescence Surfactants... 

Duhamel J (2006) Polymer chain dynamics in solution probed with a fluorescence Blob model. Acc Chem Res 39 953-960... 

The complexity observed in polymer fluorescence decay kinetics is further exacerbated when fluorescent polyelectrolytes are dissolved in aqueous media [29,30,33,35,37,43,120,122,128-132] segregation of the macromolecular structure into hydrophobic and hydrophilic-rich domains results in differing degrees of water penetration which further complicates the time-resolved fluorescence [26]. Within this context, more recent attempts to describe time-resolved polymer photophysical data include use of the blob model [133,134], which accounts for the range of environments encountered in heterogeneous systems by invoking a distribution of rate constants for excimer formation. 

As far as the excimer decay kinetics of PAA in aqueous media is concerned, de Melo and coworkers [122,130,131] have investigated the time-resolved fluorescence from a series of samples modified with various amounts of pyrene and naphthalene, respectively. Even when the aromatic content was as low as 2mol%, excimer formation was evident in the steady-state spectra. The fluorescence decays were complex irrespective of the label and were best modeled by a triple-exponential function (as in Eq. 2.8) both when emission was sampled in the monomer and excimer regions. In contrast to the distribution of rate constants in the blob model [133,134], the authors favored a scheme that describes the decay kinetics in terms of discrete rate constants. The data were also consistent with previous schemes [124-127] that account for the presence of two distinct types of monomer in addition to that of excimer in macromolecular systems one monomer enjoys kinetic isolation and is unable to form excimers, whereas the second is able to participate in excimer formation within its fluorescence lifetime. The authors [130] concluded from both steady-state and time-resolved data that PAA undergoes a conformational change from a compact form in acidic solution to an open coil at high pH. Furthermore, as the... 

Over the past 15 years, the Huorescence Blob Model (FBM) in 1999 [36] and the Model Free Analysis (MFA) in 2005 [37] were introduced to, first, deal with the distribution of excimer rate constants that led to the multiexponential character of the fluorescence decays acquired with Py-WSPs and, second, provide a robust analytical framework to analyze the monomer and excimer fluorescence decays globally to yield reliable / gg values. The aim of this chapter is to describe the mathematic rationale underlying the application of the FBM and MFA to retrieve /agg firom the decay analysis and present experimental examples describing the implementation of these robust analytical tools. 

Mathew A, Siu H, Duhamel J (1999) A Blob model to study chain folding by fluorescence. Macromolecules 32 7100-7108... 

Siu H, Duhamel J (2004) Global analysis of the fluorescence decays of a pyrene-labelled polymer using a blob model. Macnnnolecules 37 9287-9289... 

---