Microwave-assisted sensing of tetracycline using europium-sensitized luminescence fibers as probes

In this paper, we describe a facile approach—using silicate fibers immobilized with Eu(III) ions [Eu(III) fibers] as affinity probes—to rapidly sense tetracycline (TC) in complex samples. The fabrication of the Eu(III) fibers is straightforward: Simply immerse a silicate fiber into a glass tube containing Eu(III) and irradiate with microwaves (power, 900 W) for 30 s. The Eu(III) fibers selectively trap TC from aqueous samples via chelation of the β-diketone functional group of TC with the Eu(III) center. Because the Eu(III)–TC complexes on the fibers are luminescent, as a result of intermolecular energy transfer from the TC moieties to the Eu(III) centers, they can be detected directly using a fluorophotometer. To accelerate the sensing process, we also used microwave irradiation (for only 15 s) to trap the TC molecules from the sample solutions onto the Eu(III) fibers. Furthermore, only a small volume (< 10 μL) of sample solution is required for these analyses. This approach allows TC to be detected in aqueous samples, with a detection limit of 50 nM.     

Semi-quantitative determination of cationic surfactants in aqueous solutions using gold nanoparticles as reporter probes

Concentrations of cationic surfactants in aqueous solutions have been estimated on the basis of changes in the color of gold nanoparticles, used as reporter probes. We have shown that the colors of gold nanoparticles with anionic protective groups on their surfaces shift from red to indigo/purple and then back to red in a range of cationic surfactant solutions in which concentrations vary from very low to above the theoretical CMCs. The color changes occur near the theoretical CMCs, presumably because the presence of surfactant micelles in the solution prevents the gold nanoparticles from aggregating. We have used gold nanoparticles as reporter probes to determine the concentrations of cationic surfactants in products such as hair conditioners, which often contain large amounts of alkyltrimethylammonium halides. Although this approach can only provide an estimate, it can be performed simply by addition of a given amount of gold nanoparticles to a series of diluted solutions, without the need for instruments or labor-intensive procedures. Figure Photographs of a series of diluted hair conditioner solutions with added gold nanoparticles

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