Rhodamine-labelled new architecture for dual sensing of Co2+ and Hg2+ ions

Copillar[5]arene-rhodamine conjugate as a selective sensor for Hg2+ ions

A new copillar[5]arene-coupled rhodamine probe 1 shows selective sensing of Hg²⁺ ions over a series of metal ions in CH₃CN by exhibiting color change of the solution as well as turn on fluorescence. It also shows interaction with Cu²⁺ by exhibiting different color and spectral change. Tetrabutylammonium iodide distinguishes between Hg²⁺ and Cu²⁺ ions.

A novel sulfur quantum dot for the detection of cobalt ions and norfloxacin as a fluorescent “switch”

Sulfur nanomaterials exceed carbon nanomaterials in terms of the antimicrobial or antifungal properties. A novel S QDs which were prepared by “top-down” methodology to detect Co²⁺and norfloxacin was constructed for the first time. S QDs can play a dual role for detection of Co²⁺as well as norfloxacin in aqueous media as a fluorescent switch.

New Six-Membered pH-Insensitive Rhodamine Spirocycle in Selective Sensing of Cu2+ through C-C Bond Cleavage and Its Application in Cell Imaging

A new rhodamine-based chemosensor 1 with a six-membered spirocyclic ring has been synthesized, which exhibits excellent pH stability and shows selective "turn-on" fluorescent detection of Cu²⁺ ions over a series of other metal ions including Cu⁺ ions. The expansion of spirocycle improves the stability and selectivity of the chemosensors in sensing of metal ions. Till today only few rhodamine structures R1-R5 with thiourea-, hydrazine amide-, or pyrrole-decorated six-membered spirocyclic rings are known that exhibit metal-ion sensing via C-N bond cleavage of the spiro ring. In this context, rhodamine compound that responds to the metal ion through C-C bond cleavage of the six-membered spiro ring is completely unknown. The present example is a first-time report that demonstrates selective sensing of Cu²⁺ ions through C-C bond cleavage over the conventional existing systems in the literature. The chemosensor 1 is cell permeable and can detect Cu²⁺ in live cells using confocal microscopy in the biologically relevant pH range with high photostability.

A selective fluorescent 'turn-on' sensor for recognition of Zn(2+) in aqueous media

A new rhodamine-based fluorescent probe 'RhAP' was synthesized and successfully characterized using FT-IR, (13)C NMR and (1)H NMR spectroscopies, LC-MS/MS spectrometry and elemental analysis. The RhAP, a colorless and non-fluorescent compound, showed a selective fluorescent response and colorimetric change for Zn(2+) in HEPES buffer (10mM, EtOH:water, 2:1, v/v, pH7.2). Upon the addition of two equivalents of Zn(2+) to a solution of RhAP, a nearly 35-fold enhancement of the fluorescence intensity, with an emission maximum at 578 nm, was observed in comparison to the sensor alone under the same experimental conditions. The complex formation between RhAP and Zn(2+) was found to have a 1:1 ratio based on calculations obtained from Job's plot and the mole ratio plot methods. The results showed that RhAP can be used as an effective fluorescent probe for selective detecting of Zn(2+) in an aqueous medium.

A real time colorimetric ‘two in one’ kit for tracking ppb levels of uric acid and Hg2+ in live HeLa S3 cells and Hg2+ induced keto–enol tautomerism

A TBET based ‘turn-on’ fluorescent reagent with high Stokes shifts, exhibits selective and colorimetric detection of biologically important uric acid as well as toxic Hg2+.

Chromo/Fluorogenic Detection of Co(2+), Hg(2+) and Cu(2+) by the Simple Schiff Base Sensor

Herein, we reported the ditriazole Schiff base derivative 1 and evaluated its photophysical properties on induction of varieties of metal ions including Na(+), Ag(+), Ni(2+), Mn(2+), Pd(2+), Co(2+), Hg(2+), Cu(2+), Pb(2+), Cd(2+), Zn(2+), Sn(2+), Fe(2+), Fe(3+), Cr(3+) and Al(3+), in order to figure out its potential as ion sensor. The ligand 1 exhibited the strong colorimetric change in the reaction solution as well as absorption spectral shifting with the concomitant appearance of well-defined isosbestic points only upon Co(2+), Hg(2+) and Cu(2+) addition corroborates its applicability as multichannel ion detector. The different extent of spectral shifting as well as unique chromogenic change in the probe solution upon Co(2+), Hg(2+) and Cu(2+) introduction can be used as the discrimination tool for these metal ions. The ligand-metal binding stoichiometry was assessed by their optical response which was further supported by the FT-IR, NMR and mass spectrometric analysis. The association constant and the detection limits of the ligand toward Co(2+), Hg(2+) and Cu(2+) ions were calculated to be 1.52 × 10(-8), 3.26 × 10(-9), 1.16 × 10(-8) and 3.87 × 10(-10), 5.47 × 10(-11), 8.91 × 10(-11) M, respectively, employing the Benesi-Hilderbrand equation and 3 σ slope(-1) methods. Furthermore, the successive addition of Co(2+), Hg(2+) and Cu(2+) induce the constant decline in the fluorescence emission signal intensity of the probe. The quenching efficiency of the probe upon metallic induction was fitted to the Stern-Volmer equation which yielded the upward curvature in case of all the three metals ions (Co(2+), Hg(2+) and Cu(2+)) when (Io/I-1) was plotted against the quencher concentration indicating the occurrence of both the dynamic and static quenching process in the system with the average Stern-Volmer quenching constant values of 9.25 × 10(-7), 1.14 × 10(-7), 1.829 × 10(-7), respectively.

Optical sensor: a promising strategy for environmental and biomedical monitoring of ionic species

In this review, we cover the recent developments in fluorogenic and chromogenic sensors for Cu²⁺, Fe²⁺/Fe³⁺, Zn²⁺and Hg²⁺.

Selective sensing of Al3+ by naphthyridine coupled rhodamine chemosensors

Naphthyridine-based rhodamine chemosensors 1 and 2 are designed and synthesized for selective sensing of Al³⁺ ion.