Fluorescent turn-on sensors based on pyrene-containing Schiff base derivatives for Cu2+ recognition: spectroscopic and DFT computational studies

Bright photoactivatable probes based on triphenylethylene for Cu2+ detection in tap water and tea samples

Photoactivatable probes can switch fluorescence on from a weak or nonemission state to improve the sensitivity of the sensing system. In this work, we successfully constructed three highly emissive photoactivatable probes, 2-DP, 1-2-DP and 2-2-DP, for Cu2+ detection. Under UV irradiation, the photoluminescence quantum yields of 2-DP, 1-2-DP and 2-2-DP display approximately 52.4-, 11.5- and 49.2-fold enhancement, respectively. Cu2+ selectively quenches the bright photoactivated fluorescence, resulting in an approximately 38-fold fluorescence reduction. The highly selective fluorescence response to Cu2+ yields an excellent low detection limit of 5.8 nM. Moreover, the photoactivatable probes were successfully applied for Cu2+ determination in tap water and tea samples with recovery ranges of 95%-105% and 97%-106%, respectively. This work provides a more sensitive and efficient methodology for Cu2+ detection in heavy metal pollution and food safety.

Schiff Bases: A Versatile Fluorescence Probe in Sensing Cations

Metal cations such as Zn²⁺, Al³⁺, Hg²⁺, Cd²⁺, Sn²⁺, Fe²⁺, Fe³⁺ and Cu²⁺ play important roles in biology, medicine, and the environment. However, when these are not maintained in proper concentration, they can be lethal to life. Therefore, selective sensing of metal cations is of great importance in understanding various metabolic processes, disease diagnosis, checking the purity of environmental samples, and detecting toxic analytes. Schiff base probes have been largely used in designing fluorescent sensors for sensing metal ions because of their easy processing, availability, fast response time, and low detection limit. Herein, an in-depth report on metal ions recognition by some Schiff base fluorescent sensors, their sensing mechanism, their practical applicability in cell imaging, building logic gates, and analysis of real-life samples has been presented. The metal ions having biological, industrial, and environmental significance are targeted. The compiled information is expected to prove beneficial in designing and synthesis of the related Schiff base fluorescent sensors.

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.

A novel dual functional pyrene-based turn-on fluorescent probe for hypochlorite and copper (II) ion detection and bioimaging applications

A novel dual-function fluorescent probe PPH was conveniently synthesized by linking pyrazinehydrazide unit and pyrenyl fluorophore. The present probe PPH could be used for simultaneous detection of ClO^- and Cu²⁺ through a fluorescence turn-on response. The probe PPH displayed excellent selectivity and sensitivity towards ClO^- and Cu²⁺ over other anions and metal ions. The detection limits of PPH for ClO^- and Cu²⁺ were calculated to be as low as 4.02 nM and 157 nM, respectively. The probe PPH had good pH stability and was highly responsive to ClO^- and Cu²⁺ in a wide pH range. Furthermore, this probe could be readily applied to visualize ClO^- and Cu²⁺ on the test paper. Additionally, this probe was successfully utilized to the fluorescence imaging of ClO^- and Cu²⁺ in HeLa cells.

Selective sensing of a Cu(ii) ion by organotin anchored keto-enamine ligands

New organotin carboxylates [{(n-Bu)₂Sn(HL)}₂O]₂ (1), [(t-Bu)₂Sn(HL)₂] (2) and [Ph₃Sn(HL)] (3) have been synthesized and used for sensing of Cu(ii) ion. Complex 3 shows highest binding constant and better limit of detection than other complexes.