Highly Sensitive Adsorption and Detection of Iodide in Aqueous Solution by a Post-Synthesized Zirconium-Organic Framework

Effective methods of detection and removal of iodide ions (I^-) from radioactive wastewater are urgently needed and developing them remains a great challenge. In this work, an Ag⁺ decorated stable nano-MOF UiO-66-(COOH)₂ was developed for the I^- to simultaneously capture and sense in aqueous solution. Due to the uncoordinated carboxylate groups on the UiO-66-(COOH)₂ framework, Ag⁺ was successfully incorporated into the MOF and enhanced the intrinsic fluorescence of MOF. After adding iodide ions, Ag⁺ would be produced, following the formation of AgI. As a result, Ag⁺@UiO-66-(COOH)₂ can be utilized for the removal of I^- in aqueous solution, even in the presence of other common ionic ions (NO₂^-, NO₃^-, F^-, SO₄^2-). The removal capacity as high as 235.5 mg/g was calculated by Langmuir model; moreover, the fluorescence of Ag⁺@UiO-66-(COOH)₂ gradually decreases with the deposition of AgI, which can be quantitatively depicted by a linear equation. The limit of detection toward I^- is calculated to be 0.58 ppm.

Electrosynthesis of Layered Organo-Manganese Dioxide Framework-Doped with Cobalt for Iodide Sensing

Aqueous Mn²⁺ ions were anodized at 70 °C with Co²⁺ in the presence of cationic surfactant, cetyltrimethylammonium (CTA). X-ray diffraction (XRD) analysis revealed that the deposited film possesses a layered structure of MnO₂, the interlayer of which is occupied with the assembled CTA molecules. Inclusion of Co ions in the MnO₂ film was evidenced by X-ray photoelectron spectroscopy (XPS). They were located in the MnO₂ framework, not in the interlayer. The thus-obtained film, CTA-intercalated Co-framework-doped layered MnO₂ (CTA/Co-MnO₂), was applied as an electrochemical sensor toward iodide (I^-), a hydrophobic anion. The organic phase between MnO₂ layers could extract I^- ions from solution, providing a better sensitivity than a film consisting of layered MnO₂ with hydrated alkali metals. On the other hand, the Co-doped layers of MnO₂ achieved faster electron transfer kinetics for the oxidation of I^-, which resulted in a drastic reduction in response time compared to the nondoped CTA/MnO₂.

A mercuric ensemble based on a cycloruthenated complex as a visual probe for iodide in aqueous solution

A new water-soluble cycloruthenated complex Ru(bthiq)(dcbpy)2(+) (1, Hbthiq=1-(2-benzo[b]thiophenyl)isoquinoline, dcbpy=4,4'-dicarboxylate-2,2'-bipyridine) was designed and synthesized to form its mercuric ensemble (1-Hg(2+)) to achieve visual detection of iodide anions. The binding constant of 1-Hg(2+) is calculated to be 2.40×10(4)M(-1), which is lower than that of HgI2. Therefore, the addition of I(-) to the aqueous solution of 1-Hg(2+)lead to significant color changes from yellow to deep-red by the release of 1. The results showed that iodide anions could be easily detected by the naked eyes. The detection limit of iodide anion is calculated as 0.77μM. In addition, an easily-prepared test strip of 1-Hg(2+) was obtained successfully to detect iodide anions.

A selective iodide ion sensor electrode based on functionalized ZnO nanotubes

In this research work, ZnO nanotubes were fabricated on a gold coated glass substrate through chemical etching by the aqueous chemical growth method. For the first time a nanostructure-based iodide ion selective electrode was developed. The ZnO nanotubes were functionalized with miconazole ion exchanger and the electromotive force (EMF) was measured by the potentiometric method. The iodide ion sensor exhibited a linear response over a wide range of concentrations (1 × 10⁻⁶ to 1 × 10⁻¹ M) and excellent sensitivity of −62 ± 1 mV/decade. The detection limit of the proposed sensor was found to be 5 × 10⁻⁷ M. The effects of pH, temperature, additive, plasticizer and stabilizer on the potential response of iodide ion selective electrode were also studied. The proposed iodide ion sensor demonstrated a fast response time of less than 5 s and high selectivity against common organic and the inorganic anions. All the obtained results revealed that the iodide ion sensor based on functionalized ZnO nanotubes may be used for the detection of iodide ion in environmental water samples, pharmaceutical products and other real samples.