Pyranone based probe for the selective and specific recognition of zinc ions

Fluorescent Chemosensors in the Detection of Ultra-trace Quantity of Toxic Hg2+, Pb2+, Al3+, F-, AsO43- & AsO33- in Water Towards Better Health Management-A Comprehensive Review

Chemosensors have extensive applications in chemical, biological and environmental sciences. Fluorescent chemosensors are the most powerful techniques for rapid detection of ultra-trace quantity of inorganic ions in water samples with high sensitivity. Water is contaminated with various pollutant ions e.g., Cd2+ Cu2+, Hg2+, Pb2+, Mn2+, Zn2+, Al3+, AsO43-, AsO33- and F- due to increase industrialisation, usage of fertilizers, through food -beverages, water purification instruments and e-wastes. Thus, contaminated water is a potential threat to life as it transmits various bacterial waterborne diseases, so detection of contaminants is essential. This review focuses the recently developed single, dual and multi-analyte fluorescent chemosensors ligands for the detection through selective binding of trace quantity of critically toxic ions e.g., Hg2+, Pb2+ Al3+, F-, AsO33- and AsO43- in water and food samples. Binding of ions through Sensing mechanism: Intramolecular Charge transfer (ICT), Foster Resonance energy transfer (FRET), Aggregation based approaches, Photo induced electron transfer (PET) etc. have also discussed. Ligands i) derivatives of rhodamine dyes and phenanthroline ii) Schiff base with rhodamine B thiohydrazide and quinoline moiety iii) a chromone-quinolinyl hydrazide Schiff base as dual sensors iv) Nitro-furaldehyde based Schiff base as multi-analyte sensors having potential doner atoms to bind the concerned ions and easily synthesizable have been selected for reviews. The detections of toxic ions were accomplished by spectroscopic studies. Such comprehensive review has not yet been reported. This review emphasizes the works of pioneering researchers on chemosensors during the period 1990-2025. This review will also help future researchers to design new Schiff bases chemosensor and its selectivity for the detection of trace quantity of hazardous ions from environment and biological samples thereby monitoring human health.

Synthesis, Characterization and Application of Iron (III) Complex of Schiff Base Ligand as a Novel Enhancement Fluorescent Sensor for Al3+ Ion Detection

This study highlights the importance of developing sensitive and selective sensors for use in pharmaceutical applications for the first time. A novel iron(III)-complex, constructed from unsymmetrical tetradentate NNN'O type Schiff base ligand (E)-3-((6-aminopyridin-2-yl)imino)-1-phenyl butane-1-one (LH) and its structure of it characterized by using various spectroscopic techniques such as FT-IR, UV-Vis, elemental analysis, conductivity, magnetic susceptibility measurements and the TGA method. The correlation of all results revealed that the coordination of the (LH) with the metal ion in a molar ratio of 1:1 leads to the formation of an octahedral geometry around the metal ions. Conductivity data showed the electrolytic nature of the complex. Its fluorescence properties were thoroughly investigated by introducing aluminium ions in deionized water, which increased fluorescence intensity at 460 nm. The detection limit for Al3+ was optimized and found to be 1.5 µM. Notably, the fluorescent sensor successfully monitored Al³⁺ in pharmaceutical formulations. This fluorescence-based analytical method is an alternative to other methods due to its high selectivity, sensitivity, and speed. These results suggest the high potential of this system for pharmaceutical monitoring applications.

A novel one-stepped synthesized Schiff-base fluorescence probe for specific recognition of zinc ions with highly sensitive and its application in living cells

Fluorescent turn-on receptors are extensively employed for the detection of Zn ions contamination in the environment due to its simplicity, convenience and portability. However, developing highly sensitive and cell-imageable fluorescent turn-on probe for the recognition of Zn ions in living organisms remains a significant challenge. Herein, we have successfully synthesized a novel Schiff base probe (H2L) with a significant fluorescence turn-on response (Zn ions) by one-step synthetic method. In this work, H2L exhibited high sensitivity to Zn2+ ions upon interaction with various common metal ions in HEPES buffer solution. Its detection limit is 1.87 × 10-7 M, which is lower than the requirement of Environmental Protection Agency (EPA) and World Health Organization (WHO) guidelines. The fluorescence titration and Job's plot analysis suggested a 1:1 binding ratio between the probe and Zn ion, and the single-crystal structures obtained further confirmed this inference. In addition, the fluorescent sensor demonstrated recyclability, maintaining its fluorescence intensity for up to 6 cycles without significant decrease, which holds promise for future investigations on reversible fluorescent chemosensors. Notably, fluorescence imaging experiments demonstrated that H2L could be successfully used for the detection of Zn2+ in live cells.

Optical Chemosensor as a Sensitive and Selective Tool for the Detection of Thiocyanate Ions Via Cu2+ Induced Sensor and Its Practical Application

In various fields, including analytical, environmental, and biochemistry, the detection of ions is significant. A simple probe, 3-(1-((4-aminophenyl)imino)ethyl)-4-hydroxy-6-methyl-2H-pyran-2-one (DPD), was designed for this study and used for the detection of Cu2+ ions in methanol, based on dehydroacetic acid and phenylenediamine moieties. Binding interactions studies were performed using UV-Vis measurements, which showed selective binding behaviour towards Cu2+ ions. The HRMS spectral data and Job's plot were used to check the stoichiometry ratio of 2:1 of a probe to Cu2+ ions. A detection limit of 1.38×10-7 M for Cu2+ ions was observed. Theoretical DFT calculations were used to determine the quantum parameters and the energy gap between frontier molecular orbitals. Interestingly, the DPD-Cu2+ complex acted as a probe for the detection of SCN- ions at a low LOD value, i.e., 1.97×10-7 M. A novel incidence of reversibility with SCN- ions was reported using the HRMS technique. Next, real water and blood samples were used, and the concentration of Cu2+ ions was calculated to further analyse the practical applicability of the probe. The DPD probe showed better selectivity and sensitivity than previously reported sensors, especially in complex matrices, where other sensors frequently experience interference and detection limit issues, indicating its potential as an advanced tool for ion detection in various applications.

Tri-armed Schiff base fluorescent sensor for the rapid recognition of Zn(II): application in live cell imaging, test strips and TLC

Various metal ions exist in nature and human beings and play limitless vital roles in both the atmosphere and biology. A fundamental and useful aspect is the qualitative and quantitative assessment of Zn(II) at concentration levels as low as parts per billion (ppb). Thus, the design and development of novel fluorescent turn-on receptors have gained significant interest because of their potential for use in live cell imaging to detect biologically relevant metal ions with high selectivity and sensitivity. The present research illustrates the design and synthesis of a novel fluorescent sensor [(1,3,5-triazine-2,4,6-triyl)tris(hydrazine-2-yl-1-ylidene)tris(methaneylylidene)]tris(2,4-di-tert-butylphenol) (THDBP) for the selective and sensitive probing of Zn(II). The sensor exhibited a fluorescence turn-on mechanism upon treatment with Zn(II) ions at λemi. 503 nm in aq. acetonitrile. The formation of a 1 : 3 complex between THDBP and Zn(II) is confirmed from the Job plot and ESI-MS spectrum. The evaluated limit of detection (LOD) and association constant (Ka) of the sensor THDBP for Zn(II) were found to be 1.03 × 10-10 M and 2.33 × 108 M-1, respectively. Further research demonstrates the practical application of the sensor for the detection of Zn(II) ions in live cells. The sensing ability of the sensor THDBP was also explored through inexpensive test strips and TLC sheets.

Recent Advances in Organic Small-Molecule Fluorescent Probes for the Detection of Zinc Ions (Zn2+)

Zinc(II) ions (Zn2g) play crucial roles in the growth, propagation, and metabolism of animals, plants, and humans. Abnormal concentrations of Zn2+ in the environment and living organisms pose potential risks to environmental protection and human health. Therefore, it is imperative to develop rapid, reliable and in-situ detection methods for Zn2+ in both environmental and biological contexts. Furthermore, effective analytical methods are required for diagnosing diseases and understanding physiological metabolic mechanisms associated with Zn2+ concentration levels. Organic small-molecule fluorescent probes offer advantages such as fast, reliable, convenient, non-destructive detection capabilities and have significant application potential in Zn2+ detection and bioimaging; thus garnering extensive attention. Over the past two years alone, various organic small-molecule probes for Zn2+ based on different detection mechanisms and fluorophores have been rapidly developed. However, these probes still exhibit several limitations that need further resolution. In light of this context, we provide a comprehensive summary of the detection mechanisms, performance characteristics, and application scope of Zn2+ fluorescence probes since year 2022 while highlighting their advantages. We also propose solutions to address existing issues with these probes and outline future directions for their advancement. This review aims to serve as a valuable reference source offering insights into the development of advanced organic small-molecule-based fluorescence probes specifically designed for detecting Zn2+.