New optical sensor based on the immobilization of a triazene ligand in PVC membrane for Hg(II) ion

Abstract

This paper describes the development and creation of a new sensitive optical sensor that is quite selective to Hg(II) ions in aqueous solution. The sensing element, the newly synthesized methyl 2-[3-(3-methylphenyl)-2-triazen-1-yl]benzoate, incorporated into a plasticized poly(vinyl chloride) membrane, is able to determine Hg(II) ion with a high selectivity over a wide dynamic range from 5.0-115.1 μg L -1 at pH 7.5 with a lower detection limit of 0.67 µg L -1 . The response of the optode membrane to Hg(II) was fully reversible and revealed a very good selectivity towards Hg(II) ion from a wide variety of other metal ions in solution. The overall performance characteristics of the sensor were evaluated and good reversibility, wide dynamic range, long life span, long-term response stability and high reproducibility were found. The proposed optical sensor gives proper results in applications including direct determination of the Hg(II) ion in real environmental samples.

An overview of sensors and sensing materials for heavy metals in aqueous environments

“…[ 118 ] This section examines a variety of dopants, including plasticizers and organic molecules, metal nanoparticles, and inorganic salts, that have been added to polymeric sensing materials to improve their sensing properties, including sensitivity and selectivity, in an aqueous environment for heavy metals. [ 65,70,73 ]…”

“…[113] This is due to the minimization of the strain of the metal-ligand complex. [70] This minimization of strain explains why neutral oxygen-containing functional groups may have a higher selectivity to larger metal ions, whereas increasing the distance (more carbons) between ketones results in a preference for smaller metal ions. [61] Sulphur-based functional groups, such as thiols, also bind well to metal ions.…”

“…[118] This section examines a variety of dopants, including plasticizers and organic molecules, metal nanoparticles, and inorganic salts, that have been added to polymeric sensing materials to improve their sensing properties, including sensitivity and selectivity, in an aqueous environment for heavy metals. [65,70,73] Plasticizers and small organic molecules Plasticizers are small organic molecules that are commonly added to polymeric materials to improve their processability; however, the addition of these molecules significantly affects other properties. Plasticizers can affect the selectivity, sensitivity, and response time of a sensing material.…”

“…For example, at higher pH, metal ions, such as mercury, may form hydroxides, which can reduce their complexation with sensing materials and thus reduce a sensor's effectiveness. [70] In addition, the degree to which heavy metal cations complex with organic materials is affected by the pH of the environment. [71,72] Additional challenges are also present when using a polymeric sensing material.…”

“…Li et al [4] Hg +2 Polystyrene-co-Poly (N-vinyl pyrrolidone)-graphene oxide 0.9 ppm min --Conductivity Peng et al [98] Hg +2 [99] Hg +2 2-[3-(3-methylphenyl)-2-triazen-1-yl] benzoate in poly(vinyl chloride) (PVC) 0.67 μg/L c 8 min 7.5 Room temp. Spectrographic Shafiekhani et al [70] Ni +2 Poly(ethylene imine) (PEI) pentadente ethylenediamine triacetic acid acetamide 20 mM 120 min 1 Room temp. Chromatography Hughes and Rosenberg [67] Pb +2 Poly(p-aminobenzene sulfonic acid) (PBASA) Sb (III) (3 mg/L) 0.1 μg/L 240 s 2.0 25 Voltametric Yi et al [74] (Continues) metal.…”