Identifiability of Models for Fluorescence Quenching in Aqueous Micellar Systems

Abstract

The first deterministic identifiability analysis is presented for four commonly used kinetic models of fluorescence quenching of an excited probe in aqueous micelles: A) model with immobile quenchers, B) model with mobile quenchers, C) an extension of model B in which exchange of quenchers both via the aqueous phase and during micelle collisions is taken into account, and D) model with probe migration. It is shown that these specific models for fluorescence decay of an excited probe solubilized in a micelle and quenched by molecules or ions that are Poisson-distributed over the micelles, resulting in the generalized four-parameter equation f(t)=A(1) exp{-A(2)t-A(3)[1-A(4)t]}, are uniquely identifiable in terms of four descriptive A parameters. Moreover, each model also can be uniquely identified in terms of the underlying rate constants and micellar concentration or mean micellar aggregation number. This means that these parameters can be extracted in a unique way from time-resolved fluorescence quenching experiments on a probe in micelles. For each model the recommended analysis approach is given.

Highly Photoluminescent Sulfide Clusters Confined in Zeolites

“…This effect can be probably due to a self-quenching effect caused by Poisson distribution of sulfur clusters within the matrix, where the increase of sulfur content leads to the annihilation of excited-state species of S 2 − . 48,49 EQE values obtained in samples having S/Cl < 1.17, measured at 345 nm excitation, display the same qualitative trend as that when 385 nm was used as excitation wavelength. Excitation at 345 nm is the optimal wavelength to excite red/ NIR emitting species; however, it can also excite the orange emitting centers, giving rise to the observed EQE trend.…”

“…This value decreases with increasing S/Cl nominal molar ratios, reaching a value below 10% at S/Cl = 4.5. This effect can be probably due to a self-quenching effect caused by Poisson distribution of sulfur clusters within the matrix, where the increase of sulfur content leads to the annihilation of excited-state species of S 2 – . , EQE values obtained in samples having S/Cl < 1.17, measured at 345 nm excitation, display the same qualitative trend as that when 385 nm was used as excitation wavelength. Excitation at 345 nm is the optimal wavelength to excite red/NIR emitting species; however, it can also excite the orange emitting centers, giving rise to the observed EQE trend.…”

Supramolecular dynamics

“…This case will not be discussed in detail here since it is not applicable to host-guest systems. The mathematical treatment 33 and a theoretical analysis on how to identify the several mechanisms for guest and quencher binding to micelles 33,34 can be found in the literature.…”

Identifiability of models for time-resolved fluorescence with underlying distributions of rate constants

“…[33][34][35][36][37][38] However, only two reports have been published on the identification of models for fluorescence decays with an underlying distribution of decay rates as observed for an excited probe quenched by molecules or ions that are Poisson-distributed over the micelles. 39,40 In this paper we investigate the deterministic identification of several uncommon models for fluorescence decay with underlying distributions of rate constants which lead to nonexponential fluorescence δ-response functions i(t ). The decay functions considered here are the stretched exponential or Kohlrausch function, the Becquerel function, the Förster type energy transfer function, decay functions associated with exponential, Gaussian and uniform distributions of rate constants, a decay function with extreme sub-exponential behavior, the Mittag-Leffler function and Heaviside's function.…”