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This article provides an overview of the general properties of organized assembly (ordered media) systems such as aqueous surfactant and bile salt micelles, lipid and surfactant vesicles (liposomes) 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. This gives rise to improved detectability of such analytes. The altered microenvironment within the organized medium is capable of impeding the interfering action of other species (inorganic or organic) present in the sample matrix. This often can improve 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 prevent side reactions that otherwise can occur in bulk solution (or sample matrix). In addition, organic solvents or time‐consuming extraction steps can be avoided owing to the increased solubility of the nonpolar organic or inorganic reagents and/or analyte molecules in water in the presence of the organized medium; allowing for 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 chemistries that one can consider using to design/develop new, unique and improved fluorescent assays. Numerous representative 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. Some experimental considerations and cautions to keep in mind when utilizing organized media are also delineated. An extensive reference section is provided so that the interested reader can easily refer to such for more detailed information on these systems and topics.
This article provides an overview of the general properties of organized assembly (ordered media) systems such as aqueous surfactant and bile salt micelles, lipid and surfactant vesicles (liposomes) 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. This gives rise to improved detectability of such analytes. The altered microenvironment within the organized medium is capable of impeding the interfering action of other species (inorganic or organic) present in the sample matrix. This often can improve 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 prevent side reactions that otherwise can occur in bulk solution (or sample matrix). In addition, organic solvents or time‐consuming extraction steps can be avoided owing to the increased solubility of the nonpolar organic or inorganic reagents and/or analyte molecules in water in the presence of the organized medium; allowing for 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 chemistries that one can consider using to design/develop new, unique and improved fluorescent assays. Numerous representative 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. Some experimental considerations and cautions to keep in mind when utilizing organized media are also delineated. An extensive reference section is provided so that the interested reader can easily refer to such for more detailed information on these systems and topics.
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.
Light, Scattering I Micelles I Photochemistry I Rheology Aqueous micellar solutions containing cetyltrimethylammonium bromide (CTAB) and solubilized 3 4 1 -bene carboxylic acid (3-SC) or 4-stilbene carboxylic acid (4-SC) known to exhibit photorheological effects were investigated via (i) oscillatory shear viscometry, (ii) static and dynamic light scattering and (iii) electrically induced birefringence. The presence of 3-SC and 4-SC induces the formation of swollen micelles as revealed from light scattering data. The viscosity increase observed upon in situ photoisomerization of 3-SC and 4-SC is accompanied by a further increase in micelle size as shown by light scattering data. Only solutions containing 3-SC at concentration ratios c~~~/ c~-~~ 5 6.5 show non-Newtonian flow such as shear thinning, thixotropy and viscoelasticity, which are indicative of the presence of anisometric micelles. Photoisomerization induces non-Newtonian features in systems containing 4-SC and increases these features in 3-SC solutions. Two shear stress relaxation mechanisms are resolved from relaxation spectra.
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