A single chemosensor for the detection of dual analytes Cu2+ and S2− in aqueous media

An ESIPT-based fluorescent turn-on probe with isothiocyanate for detecting hydrogen sulfide in environmental and biological systems

A probe with an isothiocyanate group was synthesized and evaluated for its H₂S sensing ability. Upon addition of H₂S, the probe exhibited ratiometric properties during absorption with a red-shift. The probe exhibited fluorescent off-on responses towards H₂S via the ESIPT process, due to the conversion of isocyanate into amine. UV-vis, fluorescence, and ¹H NMR spectroscopic analyses were performed to investigate the sensing mechanism. The probe has a large Stokes shift, short response time, and low detection limit. It can be used to estimate H₂S levels within the range of 0-36 nM. The practical applicability of the probe was demonstrated using water samples and living cells.

Real time sensor for Fe3+, Al3+, Cu2+ & PPi through quadruple mechanistic pathways using a novel dipodal quinoline-based molecular probe

A quinoline-based small molecular probe, H₂L was designed, synthesized and characterized by different spectroscopic methods. It was utilized as a multi-responsive probe for the detection of Fe³⁺, Al³⁺, Cu²⁺ and PPi. It showed very selective instant turn-on fluorimetric response towards Fe³⁺and Al³⁺ with a detection limit in nanomolar range. Solutions of H₂L containing Fe³⁺ or Al³⁺ could sequentially sense PPi by a turn-off mechanism. Also, H₂L could determine the presence of Cu²⁺ very selectively among a series of other metal ions by a sharp change in colour. Detection of Cu²⁺ through colorimetry was further investigated by systematic UV-Vis studies and the potential of H₂L to act as a potential colorimetric sensor for Cu²⁺ was suitably established. Filter-paper strip experiments were conducted to demonstrate the practical utility of the proposed sensor. Potential applications of H₂L as a sensor for pH in the acidic range has also been explored.

Synthesis and application of a new chemosensor based on the thiazolylazo-quinazolinone hybrid for detection of F- and S2- in aqueous solutions

A new chemosensor based on the thiazolylazo-quinazolinone hybrid (TAQH) was designed and synthesized for naked-eye sensitive detection of F^- and S^2-in aqueous acetonitrile solution. Spectral characterization of TAQH using FT-IR, ¹H NMR, and ¹³C NMR analysis revealed that the probe TAQH was successfully synthesized using a two steps reaction, including the diazotization-coupling and condensation reactions, respectively. The ion sensing ability of TAQH toward a wide range of anions and metal ions was evaluated by naked-eye detection method and UV-Vis absorption spectroscopy. The chemosensor TAQH displayed a fast and clear color change from yellow to red in the presence of F^- and S^2- ions, enabling easily detect with the naked eye. This clear color change is due to the effective interaction of the basic F^- and S^2- anions with hydroxyl group of chemosensor as a binding site. The experimental data also revealed that the F^- and S^2- ions were sensed by the probe TAQH over a wide pH range from 3 to 8. The results also confirmed that the TAQH has a wide linear detection range for F^- and S^2- ions. From UV-vis titration experiment, the limit of detection (LOD) for F^- and S^2- ions was found to be 3.1 μM and 5.7 μM, respectively. For quantitative measurements, the paper test strips containing TAQH were successfully fabricated and applied to detect F^- and S^2- ions in aqueous solutions. Furthermore, Job's plot based on spectroscopic data showed one-to-one stoichiometry for the interaction of anions with probe TAQH. Therefore, the proposed chemosensor with excellent features like the cost-effective, high sensitively and selectively and short response times can be utilized in any physical and biological conditions.

A fast, highly selective and sensitive colorimetric and fluorescent sensor for Cu2+ and its application in real water and food samples

A new oligothiophene functionalized Schiff base sensor 3TDC has been successfully designed and synthesized. Sensor 3TDC exhibited "naked-eye" colorimetric and selective "on-off" fluorescence response toward Cu²⁺ with high selectivity and sensitivity within a wide pH range. The binding ratio of the sensor 3TDC and Cu²⁺ was determined to be 1:1 through fluorescence titration, Job's plot, ¹H NMR titration, FTIR and DFT studies. The detection limit is calculated to be as low as 2.81 × 10^-8 M, which is much lower than the allowable level of Cu²⁺ in drinking water set by U.S. Environmental Protection Agency (~20 μM) and the World Health Organization (~30 μM). The binding constant (K_a) of Cu²⁺ to sensor 3TDC was found to be 2.52 × 10⁴ M^-1. Sensor 3TDC for Cu²⁺ detection exhibited fast fluorescence response within 30 s and high anti-interference performance. Moreover, sensor 3TDC could be used as an effective fluorescent sensor for detecting Cu²⁺ ions in various real water and food samples with good accuracy and high precision.

A simple, reversible, colorimetric and water-soluble fluorescent chemosensor for the naked-eye detection of Cu2+ in ~100% aqueous media and application to real samples

A simple, reversible, colorimetric and water-soluble fluorescent chemosensor ADA for the naked-eye detection of Cu²⁺ was developed. Sensor ADA showed high selectivity and sensitivity toward Cu²⁺ in ~100% aqueous media over wide pH range. Sensor ADA exhibited a red-shift in the absorption spectra from 466 to 480nm that is accompanied by significant color change from light yellow to yellowish brown instantaneously. The Cu²⁺ recognition is based on the chelation-enhanced fluorescence quenching (CHEQ) effect of the paramagnetic nature. The lowest detection limit is determined to be 15.8nM, which is much lower than the allowable level of Cu²⁺ in drinking water set by U.S. Environmental Protection Agency (~20μM) and the World Health Organization (~30μM). The 1:1 binding process was confirmed by fluorescence measurements, IR analysis and DFT studies. Moreover, sensor ADA was successfully applied for determination of trace level of Cu²⁺ with 4 reuse cycles in various water samples, which affords promising potential in ion-detection field.

A new Schiff-based chemosensor for chromogenic sensing of Cu2+, Co2+and S2−in aqueous solution: experimental and theoretical studies

A new Schiff-based multifunctional colorimetric chemosensor1was developed for the detection of various analytes (Cu²⁺, Co²⁺and S²⁻).