Spectrofluorimetric determination of picogram level Pb(II) using a dimercaptothiadiazole fluorophore

Highly Selective Detection of Iodide in Biological, Food, and Environmental Samples Using Polymer-Capped Silver Nanoparticles: Preparation of a Paper-Based Testing Kit for On-Site Monitoring

This work describes a facile synthesis of polymer-capped silver nanoparticles at room temperature. Chitosan oligosaccharide lactate-capped silver nanoparticles (COL-AgNPs) show the surface plasma resonance (SPR) band at 400 nm. The color of the COL-AgNPs was observed to be brownish yellow. The synthesized COL-AgNPs are stable for 5 months. The COL-AgNPs were characterized by UV-vis, X-ray diffraction, high-resolution transmission electron microscopy (HR-TEM), mass, and Fourier transform infrared spectral techniques. The obtained COL-AgNPs are monodispersed, and the range of the particle diameter was calculated to be 16.37 ± 0.15 nm by HR-TEM. We have utilized the COL-AgNPs as a probe to sense iodide (I^-). The SPR band of COL-AgNPs was decreased after the addition of iodide, and the color of the solution changed to colorless. Based on the decreases in SPR band absorbance, the concentration of iodide was calculated. The detection limit was found to be 108.5 × 10^-9 M (S/N = 3). Other interferences (825- and 405-fold) did not interfere with the detection of 1.48 × 10^-6 M iodide. The sensing mechanism was also discussed. Finally, we have successfully applied our sensing system for the detection of iodide in tap water, river water, pond water, blood serum, urine, and food samples. Good recoveries are obtained with spiked iodide in the real samples. Importantly, we have developed a paper-based kit using wax-printed paper for the on-site monitoring of iodide. The developed paper-based kit absorbance was validated with the microplate reader. To the best of our knowledge, this is the first report that used six different real samples for the detection of iodide and development of the paper-based kit for on-site monitoring.

Highly selective and sensitive coumarin-triazole-based fluorometric 'turn-off' sensor for detection of Pb2+ ions

Exposure to even very low concentrations of Pb²⁺ is known to cause cardiovascular, neurological, developmental, and reproductive disorders, and affects children in particular more severely. Consequently, much effort has been dedicated to the development of colorimetric and fluorescent sensors that can selectively detect Pb²⁺ ions. Here, we describe the development of a triazole-based fluorescent sensor L5 for Pb²⁺ ion detection. The fluorescence intensity of chemosensor L5 was selectively quenched by Pb²⁺ ions and a clear color change from colorless to yellow could be observed by the naked eye. Chemosensor L5 exhibited high sensitivity and selectivity towards Pb²⁺ ions in phosphate-buffered solution [20 mM, 1:9 DMSO/H₂ O (v/v), pH 8.0] with a 1:1 binding stoichiometry, a detection limit of 1.9 nM and a 6.76 × 10⁶  M^-1 binding constant. Additionally, low-cost and easy-to-prepare test strips impregnated with chemosensor L5 were also produced for efficient of Pb²⁺ detection and proved the practical use of this test.

Economically viable sensitive and selective luminescent sensor for the determination of Au(iii) in environmental samples

An economically viable luminescent sensor for Au(iii) (detection limit of 1.0 pg L⁻¹) was described in this paper using the 2,5-dimercapto-1,3,4-thiadiazole (DMT) fluorophore.

Fe(3+)-selective fluorescent probe based on aminoantipyrine in aqueous solution

A novel and simple Schiff base composed with 9-anthraldehyde and 4-aminoantipyrine was synthesized and characterized as a fluorescent probe. In the presence of Fe(3+), the fluorescent intensity has a dramatic enhancement over other examined metal ions in aqueous solution. The method of Job's plot indicated the formation of 1:1 complex between probe and Fe(3+), and the possible binding mode of the system was also proposed. Moreover, other examined metal ions had no effect on the detection of Fe(3+).