Fluorescence in Organized Assemblies

Abstract

This article provides an overview of the general properties of organized assembly (ordered media) systems, such as aqueous surfactant and bile salt micelles, lipid (liposomes) and surfactant vesicles, and cyclodextrins (CDs), and summarizes their utilization to enhance the performance of analytical fluorescence measurements. In many instances, organic molecules and metal complex species when included within a CD cavity or solubilized and bound to surfactant aggregates exhibit enhanced fluorescence, improving detectability of such analytes. The altered microenvironment within the organized medium can impede the interfering action of other species (inorganic or organic) present in the sample matrix, which often improves the selectivity of the analytical method. These benefits of improved sensitivity and selectivity arise from the compartmentalization, isolation, and shielding of the excited singlet state of the guest analyte from quenching and nonradiative decay processes, as well as preventing side reactions that otherwise can occur in bulk solution (or sample matrix). Organic solvents or time‐consuming extraction steps can also be avoided, owing to the increased solubility of nonpolar organic or inorganic reagents and/or analyte molecules in water in the presence of the organized medium, allowing the use of an aqueous medium to perform the procedure. The possibility of conducting reactions and forming fluorescent organic or metal chelates in micellar (or other organized) media that are not observed in a bulk homogeneous solvent system serves to expand the scope of possible chemistries for design/development of new, unique, and improved fluorescent assays. Examples of fluorescent methods for determination of both organic and inorganic analytes are provided, which serve to illustrate the advantages and benefits accrued from the use of the micelles, vesicles, liposomes, or CDs in such procedures, along with experimental considerations and cautions in utilizing organized media.

Accumulation of phenolics in natural and micropropagated plantlets of Thymus pseudopulegioides Klokov & Des.-Shost. with their antioxidant potentials

“…Below 0.1% it was less efficient to extract RA up to 0.05%, whereas maximum RA was extracted at 0.1% and its yield remained constant up to 0.4%. After this point any increase in Triton X-114 concentration remained ineffective, but other minor phenolics were being extracted from wild samples, in particular, as reported elsewhere (Memon et al, 2008). Obviously, Triton X-114 is capable of extracting small-sized phenolics at higher percentages; however, it is efficient at 0.1% for RA.…”

Application of PARAFAC to determination of distribution constants and spectra of fluorescent solutes in micellar solutions

“…[M] gives a linear plot whose slope is approximately equal to K eq . A recent review article 17 points out that it may not be surprising for solute to have markedly different spectroscopic characteristics (e.g., quantum yields, absorption coefficients and spectral shapes). Given these different characteristics in the two phases, the scores of the solutes in two phases will not be antisymmetric, since eqn ( 8) and ( 9) do not hold valid.…”

Spectrofluorimetric determination of the antineoplastic agent lomustine based on the sensitizing effect of β‐cyclodextrin

“…Upon complexation with CDs, many analyte molecules exhibit enhanced luminescence efficiencies compared to that observed in bulk water . The included solute molecule experiences a less polar and more rigid local microenvironment .…”