Fluorescence sensors for selective detection of Hg²⁺ ion using a water-soluble poly(vinyl alcohol) bearing rhodamine B moieties

A cationic iridium(III) complex containing a thiosemicarbazide unit: Synthesis and application for turn-on chemiluminescent detection of Hg2

A novel cationic iridium(III) complex [(ppy)₂Ir(bPCPC)]PF₆ (ppy: 2-phenylpyridine; bPCPC: 2-([2,2'-bipyridine]-4-carbonyl)-N-phenylhydrazinecarbothioamide) containing a thiosemicarbazide unit was designed and synthesized. The thiosemicarbazide unit was a sensitive functional group to Hg²⁺, when it reacted with Hg²⁺, it was desulphurized and thus led to the formation of 1,3,4-oxadiazole, [(ppy)₂Ir(bPCPC)]PF₆ resultantly was used as a "turn-on" chemodosimeter for luminescent detection of Hg²⁺ in DMF/PBS buffer solution at pH = 7-11. Except for Ag⁺, recognition capability of [(ppy)₂Ir(bPCPC)]PF₆ to Hg²⁺ was not interfered by other common metal ions (Co²⁺, Li⁺, Zn²⁺, Pb²⁺, K⁺, Al³⁺, Na⁺, Mn²⁺, Cu²⁺, Fe²⁺, Fe³⁺, Cr³⁺, Ba²⁺, Mg²⁺, Ni²⁺ and Ca²⁺). The detection limit was 1.83 × 10^-9 mol∙L^-1 (0.37 ppb), which indicated the complex was a highly sensitive chemiluminescent detection reagent of Hg²⁺.

Fluorescent, colourimetric, and ratiometric probes based on diverse fluorophore motifs for mercuric(II) ion (Hg2+) sensing: highlights from 2011 to 2019

Though it has not been shown to deliver any biological importance, mercuric(II) ion (Hg²⁺) is a deleterious cation which poses grievous effects to the human body and/or the ecosystem, hence, the need for its sensitive and selective monitoring in both environmental and biological systems. Over the years, there has been a great deal of work in the use of fluorescent, colourimetric, and/or ratiometric probes for Hg²⁺ recognition. Essentially, the purpose of this review article is to give an overview of the advances made in the constructions of such probes based on the works reported in the period from 2011 to 2019. Discussion in this review work has been tailored to the kinds of fluorophore scaffolds used for the constructions of the probes reported. Selected examples of probes under each fluorophore subcategory were discussed with mentions of the typically determined parameters in an analytical sensing operation, including modulation in fluorescence intensity, optimal pH, detection limit, and association constant. The environmental and biological application ends of the probes were also touched where necessary. Important generalisations and conclusions were given at the end of the review. This review article highlights 196 references.

Colorimetric and turn-on Fluorescence Chemosensor for Hg2+ Ion Detection in Aqueous Media

A new rhodamine 6G based fluorescent and colorimetric chemosensor, containing N-methyl imidazole nucleus, for the selective detection of Hg²⁺ ion was designed and synthesized. The results of UV-Vis and fluorescence spectral study indicated that the receptor is selective and sensitive towards Hg²⁺ with no noticeable interference with other competitive metal ions. The addition of Hg²⁺ to the receptor induced a rapid color change to pink from colorless and the turn-on fluorescence response toward Hg²⁺ among different cations was studied. The stoichiometric ratio of 1:1 between the receptor and Hg²⁺ was supported by Job's plot. The color change and turn-on fluorescence response upon addition of Hg²⁺ ion was ascribed by the spirolactam ring-opening mechanism. The probable mode of binding between the receptor and Hg²⁺ was confirmed by ¹H NMR and Mass spectral study. For the practical application, its electrospun nanofiber test strips successfully applied to recognize Hg²⁺ ion in aqueous media. Graphical Abstract Schematic representation of Hg²⁺ detection by rhodamine based sensor.

A novel cationic iridium(iii) complex with a thiorhodamine-based auxiliary ligand: application for luminescent and colorimetric detection of Hg2+in an aqueous solution

Detecting Hg²⁺in an aqueous solution with detection limits of 16 ppb by luminescence detection and 80 ppb by absorption detection.

Graphene-Rhodamine Nanoprobe for Colorimetric and Fluorimetric Hg(2+) Ion Assay

This article reveals the first ever prospective application of Graphene-Rhodamine array (GRH) as a colorimetric and fluorimetric sensor for Hg(2+) ions. The duality of Graphene to undergo π-π and dispersive interactions with Rhodamine as well as to act as a selective adsorbent for Hg(2+) is conceptualized in this study. These interactions lead to decrease in absorbance of the dye in the presence of graphene, which is restored when kept in contact with Hg(2+) ions. The feasibility of the mechanism has been proved using EDTA as the coordinating ligand. It is noteworthy that all the optical variations occurred in the visible scale of the electromagnetic spectrum. The GRH array exhibited higher sensitivity toward the target ion with a limit of detection of 2 ppb. A perfect linear variation of absorbance at 554 nm with Hg(2+) concentration was observed in 0-1000 nM range, enabling the use of the system as a quantitative sensor for the test ion. The commendable selectivity of the array toward Hg(2+) ion has been investigated by observing the optical response in the presence of other environmentally relevant metal ions. A reversible turn off and turn on INHIBIT logic gate has been proposed which extends the scope of the designed array for the development of automated chemical systems. The fluorescence resonance energy transfer (FRET) ability of graphene paves the backbone for the fluorimetric detection. Fluorimetric strategy yielded a much lower limit of detection of 380 ppt using this probe, which makes a significant advance in trace detection of Hg(2+) ions.