Colorimetric and fluorescent multi-ion recognition by Anthracene appended di-Schiff base chemosensor

A review on polycyclic aromatic compounds based chemosensors for toxic ions detection - Present and future perspective

This comprehensive review delves into the current landscape and future outlook of chemosensors constructed from polycyclic aromatic compounds (PACs) for the detection of toxic ions. PACs, known for their unique molecular properties, have emerged as key building blocks for the development of chemosensors due to their sensitivity, selectivity, and versatility. The review begins by providing an overview of the existing literature on PAC-based chemosensors, detailing their design principles, structural modifications, and mechanisms of ion recognition. The discussion encompasses various toxic ions, including heavy metals, anions, and other environmental pollutants, showcasing the broad applicability of PAC-based chemosensors in diverse analytical contexts. The review also highlights recent advancements in the field, exploring novel strategies and materials for enhancing the performance of PAC-based chemosensors. Furthermore, the review critically evaluates the current challenges and limitations associated with PAC-based chemosensors, offering insights into potential avenues for future research and technological development.

A new bodipy/pillar[5]arene functionalized magnetic sporopollenin for the detection of Cu(II) and Hg(II) ions in aqueous solution

In this study, a new bodipy/pillar[5]arene functionalized magnetic MS-Sp-P[5]-bodipy microcapsule sensor was prepared based on the use of environmentally friendly for the selective and sensitive detection of Cu(II) and Hg(II) ions in aqueous media. SEM results used in the characterization process of the materials synthesized at each stage confirmed the structural and morphological changes in the pore structure, while other characterization results (FT-IR and XRD) elucidated the role of pillar[5]arene compound and bodipy dye in the synthesis of magnetic microcapsule sensors. The colloidal solution of MS-Sp-P[5]-bodipy (water/ethanol)) showed two fluorescence bands centered at 402 and 540 nm. The detection limits of MS-Sp-P[5]-bodipy for Hg(II) and Cu(II) were calculated to be 0.06 µM and 2.27 µM, respectively (at 540 nm). The linear range of the magnetic sensor for Hg(II) and Cu(II) was found to be in the range of 1-150 µM and 10-150 µM, respectively. The experimental results (response time, pH, temperature, sensitivity and selectivity) demonstrated the applicability and potential of the prepared magnetic microcapsule sensor for the detection of Cu(II) and Hg(II) in water and tap water samples containing heavy metal ions.

A novel isophorone-based fluorescent probe for recognition of Al3+ and its bioimaging in cells and plants

In this work, a novel isophorone-based fluorescent probe H-1 was designed and synthesized. The probe H-1 could achieve highly selective detection of Al³⁺ through forming a 1:1 complex, with a recognition mechanism based on intramolecular charge transfer (ICT). The detection limit of the probe H-1 for Al³⁺ is as low as 8.25 × 10^-8 M which was determined by fluorescent titration. It is confirmed that H-1 could be used not only for fluorescence spectrometry to detect Al³⁺ ions in actual water samples, but also for biological imaging to detect Al³⁺ ions in cells and plants.

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.

Theoretical investigation on the fluorescence properties and ESIPT mechanism of the Al3+ ion sensor 1-((2-hydroxynaphthalen-1-yl)methylene)urea(OCN)

A new action mechanism for the fluorescent detection on the Al³⁺ ion of the sensitive 1-((2-hydroxynaphthalen-1-yl)methylene)urea(OCN) is theoretically studied. The extensive theoretical calculations on the OCN and the isomer structure OCN-T are performed. The emission and absorption spectra consistent with the experiment value. The absorption spectra peaks (362 nm and 326 nm) of OCN and OCN-T molecules are attributed to the experimentally observed absorption spectra at 356 nm and 314 nm, respectively. The calculated fluorescence value of the OCN-AL structure is 460 nm, while the OCN-T-AL structure has no fluorescence. These results better explain that OCN and its isomers OCN-T are involved in the absorption, and the detection spectrum signal is emitted from the OCN-AL complex. The OCN and OCN-T molecules are obvious hydrogen bonding systems. The excited state intramolecular proton transfer photochemical behaviors and detecting Al³⁺ ion photophysical changes were explained for the first time at the molecular level. As driving force of excited state intramolecular proton transfer (ESIPT) reaction, the bond parameters and vibrational frequencies of intramolecular hydrogen bond were analyzed by optimizing structures and calculating infrared spectra, analysis of frontier molecular orbitals. To further elucidate the proton transfer reactive paths, the scanned the potential energy curves (PECs) of OCN and OCN-T chemosensor in different electronic states are plotted. This work proposes a reasonable explanation for the detection mechanism of the OCN sensor.

On the Electroanalytical Detection of Zn Ions by a Novel Schiff Base Ligand-SPCE Sensor

A novel bidentate Schiff base (L) is here proposed for the detection of Zn ions in water. The structure of the synthesized Schiff base L was characterized by FT-IR, ¹H NMR and ¹³C NMR. Optical characteristics were addressed by UV-Visible spectroscopy and Photoluminescence (PL) measurements. PL demonstrated that L displays a "turn-off" type fluorescence quenching in the presence of Zn²⁺ ion in aqueous solution, indicating its ability to preferentially coordinate this ion. Based on these findings, an L-M (where M is a suitable membrane) modified screen-printed carbon electrode (SPCE) was developed to evaluate the electrochemical behavior of the Schiff base (L) with the final objective of undertaking the electroanalytical determination of Zn ions in water. Using various electrochemical techniques, the modified L-M/SPCE sensor demonstrates high sensitivity and selectivity to Zn ions over some common interferents ions, such as Ca²⁺, Mg²⁺, K⁺, Ni⁺⁺ and Cd⁺⁺. The potentiometric response of the L-M/SPCE sensor to Zn ions was found to be linear over a relatively wide concentration range from 1 μM to 100 mM.

Chromone functionalized pyridine chemosensor for cupric ions detection

A new Schiff base 2-ethoxy-3-{[(6-{[(2-ethoxy-4-hydroxy-2H-chromen-3-yl)methylidene]amino}pyridine-2-yl)imino]methyl}-2H-chromen-4-ol (CD) was synthesized as a result of the condensation of 2,6-diaminopyridine and 3-formyl chromone in 1:2 M ratio and used for cupric ions detection and characterized through FTIR, HRMS and ¹H NMR spectral techniques. The sensing capability of Schiff base for cupric ions as compared to other transition metal ions was examined by absorbance and emission studies. A considerable decrease in emission intensity appeared in Schiff base in the case of cupric ions while irrelevant changes were examined for the rest of the ions. The binding stoichiometry was obtained as 1:2 for CD: Cu²⁺ complex intended from the job's plot which was confirmed through HRMS spectral technique. DFT calculations were carried for the confirmation of structural relationships and absorption-emission data. The Regression coefficient, Limit of detection, and Association constant were obtained as 98.7%, 1.2 × 10^-6 M, and 3.26 × 10⁴ M^-1 respectively using Benesi-Hildebrand (B-H) equation. The sensing power of Schiff base CD to recognize cupric ions was unaltered by the addition of the rest of metal ions, which was authenticated through interference studies. Schiff base CD and its complex with cupric ions were found stable over an extensive time period as revealed by time-reliant studies. The data collected by pH studies revealed that the preferred pH range for detecting cupric ions by Schiff base CD was 6 to 11. The Schiff base was finally utilized for sensing cupric ions in a variety of spiked samples of water like canal water, tap water, groundwater, distilled water.

Fluorescent chemosensors for Hg2+ ions based on a pyridine-attached phenanthridine probe

The sensor probe detects selectively Hg2+ ions in semi-aqueous medium. Probe showed ratiometric response with low detection limit. We observed that 1 : 1 binding mode between probe and Hg2+ ions. Additionally, this probe was utilized for various practical applications.