Electrochemical sensors for the determination of Zn2+ ions based on pendant armed macrocyclic ligand

Synthesis and Characterization of 1H-Imidazole-4,5-dicarboxylic Acid-Functionalized Silver Nanoparticles: Dual Colorimetric Sensors of Zn2+ and Homocysteine

A colorimetric assay has been developed for Zn²⁺ and homocysteine (Hcy) detection using functionalized silver nanoparticles (AgNPs). AgNPs have been synthesized using silver nitrate, where sodium citrate is used as a stabilizing agent and NaBH₄ as a reducing agent. Then, the nanoparticles (citrate@AgNPs) were functionalized with 1H-imidazole-4,5-dicarboxylic acid (IDCA). UV-visible and FTIR spectra suggested that IDCA was functionalized on the surface of citrate@AgNPs through the N atom of the imidazole ring. The IDCA-functionalized silver nanoparticles (IDCA@AgNPs) simultaneously detected Zn²⁺ and Hcy from aqueous solution and showed different responses to the two analytes (Zn²⁺ and Hcy) based on the aggregation-induced color change of IDCA@AgNPs. They showed the color change from yellow to red, which was easily discriminated by visual inspection as well as UV-visible spectroscopy. The surface plasmon resonance absorbance values of Zn²⁺ and Hcy are 485 and 512 nm, respectively, when Zn²⁺ and Hcy react with IDCA@AgNPs. IDCA@AgNPs showed linearity with Zn²⁺ and Hcy concentrations, with the detection limit of 2.38 μM and 0.54 nM, respectively (S/N = 3). The IDCA@AgNPs showed excellent selectivity toward Zn²⁺ and Hcy compared to the different metal ions and amino acids, respectively. Optimal detection was achieved toward Zn²⁺ and Hcy in the pH range 3-10. In addition, IDCA@AgNPs were used to detect Zn²⁺ and Hcy from lake water, showing low interference.

A luminescent Cd(ii) coordination polymer as a multi-responsive fluorescent sensor for Zn2+, Fe3+ and Cr2O72− in water with fluorescence enhancement or quenching

A luminescent Cd(ii) coordination polymer can act as a multi-responsive sensor for efficiently detecting Zn²⁺, Fe³⁺ and Cr₂O₇²⁻ ions.

Potentiometric multi-walled carbon nanotube Zn-sensor based on a naphthalocyanine neutral carrier: experimental and theoretical studies

Naphthalocyanine derivative is incorporated in carbon paste electrode and examined as a neutral carrier for zinc selective electrode.

Solid contact Zn2+ -selective electrode with low detection limit and stable and reversible potential

A new solid contact Zn2+ polyvinylchloride membrane sensor with 2-(2-Hydroxy-1-naphthylazo)-1,3,4 -thiadiazole as an ionophore has been prepared. For the electrode construction, ionic liquids, alkylmethylimidazolium chlorides are used as transducer media and as a lipophilic ionic membrane component. The addition of ionic liquid to the membrane phase was found to reduce membrane resistance and determine the potential of an internal reference Ag/AgCl electrode. The electrode with the membrane composition: ionophore: PVC: o-NPOE: ionic liquid in the percentage ratio of (wt.) 1:30:66:3, respectively, exhibited the best performance, having a slope of 29.8 mV decade−1 in the concentration range 3×10−7–1×10−1 M. The detection limit is 6.9×10−8 M. It has a fast response time of 5–7 s and exhibits stable and reproducible potential. It has a fast response time of 5–7 s and exhibits stable and reproducible potential, which does not depend on pH in the range 3.8–8.0. The proposed sensor shows a good and satisfactory selectivity towards Zn2+ ion in comparison with other cations including alkali, alkaline earth, transition and heavy metal ions. It was successfully applied for direct determination of zinc ions in tap water and as an indicator electrode in potentiometric titration of Zn2+ ions with EDTA.

A multi-pH-dependent, single optical mesosensor/captor design for toxic metals

The fabrication of low-cost, simple nanodesigns with sensing/capture functionality has been called into question by the toxicity and non-degradability of toxic metals, as well as the persistent threat they pose to human lives. In this study, a single, pH-dependent, mesocaptor/sensor was developed for the optical and selective removal of toxic ions from drinking water and physiological systems such as blood.

Halogen-free ionic liquid as an additive in zinc(II)-selective electrode: surface analyses as correlated to the membrane activity

Two conventional Zn(II) polyvinyl chloride (PVC) membrane electrodes have been prepared and characterized. They were based on dibenzo-24-crown-8 (DBC) as a neutral carrier, dioctyl phthalate (DOP) as a plasticizer, and potassium tetrakis (p-chlorophenyl) borate, KTpClPB or the halogen-free ionic liquid, tetraoctylammonium dodecylbenzene sulfonate [TOA][DBS] as an additive. The use of ionic liquid has been found to enhance the selectivity of the sensor. For each electrode, the surfaces of two membranes were investigated using X-ray photoelectron, ion-scattering spectroscopy and atomic force microscopy. One of the two membranes was conditioned by soaking it for 24 h in a 1.0×10(-3) M Zn(NO(3))(2) solution and the second was soaked in bi-distilled water for the same interval (24 h). Comparing the two surfaces indicated the following: (a) the high selectivity in case of using [TOA][DBS] as an additive is due to the extra mediation caused by the ionic liquid and (b) the working mechanism of the electrode is based on phase equilibrium at the surface of the membrane associated with ion transport through the bulk of the membrane.