Triazole-Coupled Benzimidazole-Based Fluorescent Sensor for Silver, Bromide, and Chloride Ions in Aqueous Media

A cost-effective and efficient fluorescence staining agent for the identification of microplastics in environmental samples and zebrafish (Danio rerio)

Microplastics (MPs) are recognized as a significant environmental hazardous material. Therefore, identifying and tracking microplastics are crucial to understand their harmfulness. Herein, we introduce (Z)-N'-(pyren-1-ylmethylene)pyrazine-2-carbohydrazide (PPC) as a cost-effective and efficient fluorescence staining agent. Unique properties of PPC, including aggregation-induced emission (AIE) and solvatochromism, were verified by spectroscopic studies and theoretical calculations. PPC selectively stained eight types of MPs with green fluorescence in water/tetrahydrofuran (THF) solution (97/3, v/v). Interestingly, only polyurethane (PU) was selectively stained both in green and blue channel using 50 % ethanol (EtOH) treatment. Moreover, with 30 % EtOH treatment, PU and polyethylene terephthalate (PET) were distinctly stained in the blue channel, highlighting their selective fluorescence. These results suggested that changes in solvent polarity induced by different EtOH amounts might alter the binding strength between PPC and MPs, resulting in varying fluorescence responses. In addition, the adsorption interaction of PPC to MPs was proposed, based on thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and non-covalent interaction (NCI) analysis. PPC could identify MPs without any influence in the size, aging and pH difference. Successfully, PPC could stain eight types of MPs and selectively PU and PET in artificial environmental samples like seawater, river water and soil. Moreover, PPC-labeled MPs could be tracked in biological system such as Danio rerio (zebrafish) to monitor the transit and accumulation of MPs. These results underscore the potential of PPC for efficient detection of MPs in environmental and biological systems.

An AIE-based fluorescent dye for selective staining of polyamide microplastics without pretreatment: Applications to environmental samples and zebrafish

A novel staining dye, BEM ((1E,1'E)-1,1'-([2,2'-bithiophene]-5,5'-diyl)bis(N-(9-ethyl-9H-carbazol-3-yl)methanimine)) was synthesized for selective identification of polyamide (PA) micrplastics. BEM showed unique photophysical properties such as solvatochromism, intramolecular charge transfer (ICT), and aggregation induced emission (AIE) which were demonstrated through spectroscopic analysis and density functional theory (DFT) calculations. The optimal staining conditions for selective staining of PA by BEM were established by evaluating the staining efficiency according to the variation of the solvent compositions, concentrations of BEM, and staining durations. BEM demonstrated outstanding selective staining of PA among 11 types of microplastics (MPs) and 5 types of non-plastics through the emission of green fluorescence. BEM successfully identified PA without any noticeable influence on the size change of PA, aging of PA, and pH alteration of the solvent. In addition, BEM was practically applied to environmental samples like river water, seawater, and soil for selective identification of PA without pretreatment. In particular, the cost-effective technique of BEM-labeled PA allowed to monitor the location and accumulation of PA in living zebrafish. The interaction between PA and BEM was investigated through scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS), which suggested that BEM might be adsorbed onto the surface of PA. Moreover, non-covalent interaction (NCI) analysis demonstrated that the intermolecular hydrogen bonds and van der Waals interactions would play a significant role in the adsorption process between PA and BEM.

Design, Synthesis and Application of 1,4-disubstituted 1,2,3-triazole Based Chemosensors: A Promising Avenue

The 1,2,3-triazole-based chemosensors, synthesized through Cu(I)-catalyzed azide-alkyne cycloaddition via 'click chemistry', offer a straightforward yet highly effective method for detecting metal cations and anions with remarkable accuracy, selectivity and sensitivity, making them invaluable across various fields such as chemistry, pharmacology, environmental science and biology. The selective recognition of these ions is crucial due to their significant roles in biological and physiological processes, where even slight concentration variations can have major consequences. The article reviews literature from 2017 to 2024, highlighting advancements in the synthesis of 1,2,3-triazole-based ligands and their application (along with sensing mechanism) for detection of various ions causing health and environmental hazards. The detection aspects have been discussed sequentially for the transition-, inner transition-, and the metals from the s or p block of the periodic table.

A low-cost TICT-based staining agent for identification of microplastics: Theoretical studies and simple, cost-effective smartphone-based fluorescence microscope application

A novel staining agent, (5-(4-(diethylamino)benzylidene)- 1,3-dimethylpyrimidine-2,4,6(1 H,3 H,5 H)-trione) (DDB) was developed for the effective detection of environmentally harmful microplastics. DDB has competitive cost advantages, namely its facile synthesis and high yield, over Nile Red (NR), which is commonly used for microplastic staining. The unique photophysical properties of DDB, including emissive twisted intramolecular charge transfer (TICT) and aggregation-induced emission (AIE), were corroborated via spectroscopic investigations and density functional theory (DFT) calculations. Notably, DDB demonstrated superior selectivity for staining microplastics (polyethylene (PE), polyurethane (PU), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), and polyethylene terephthalate (PET)) over non-plastic materials in water. Furthermore, modulation of the solvent environment during the staining process yielded distinct fluorescence in both the green and red channels for specific types of plastic with the interplay between locally excited (LE) and TICT states. Treatment with 5% ethanol results in the selective staining of PE and PET with the emission of red fluorescence, whereas treatment with 30% ethanol facilitates the selective staining of PU, PVC, and PET with the emission of green fluorescence. Additionally, DDB could selectively stain microplastics in spiked soil and river water samples. Furthermore, a smartphone-based fluorescence microscope was developed at a cost below $100, validating the effective detection of microplastics stained with the newly synthesized DDB. The outcomes of this research demonstrate the potential of DDB as an economical and efficient agent for selective microplastic detection.

Recent Advances in Organic Sensors for the Detection of Ag+ Ions: A Comprehensive Review (2019-2023)

Recently, organic sensors for the detection of Ag+ and other metal ions have experienced significant advancements. This is because there is a growing demand for reliable and sensitive tools to monitor various environmental pollutants. Organic sensors have O-, S-, and N-donor atoms, which can act as a ligand and coordinate with different metal ions, hence stabilizing them in a variety of oxidation states. This interaction gives colorimetric and fluorescence changes, which are used to monitor Ag+ and other metal ions. This comprehensive review highlights the latest developments in organic sensors for the recognition of Ag+. We present an in-depth analysis of the underlying principles and mechanisms governing Ag+ ion recognition. Various organic sensing platforms, such as fluorescent and colorimetric sensors, are discussed, shedding light on their unique advantages and limitations. Special attention is given to the diverse range of organic ligands, receptors, and functional materials used to achieve high sensitivity, selectivity, and quantification accuracy. Additionally, we delve into real-world applications of organic sensors for Ag+ ion detection, examining their performance in complex matrices such as biological, environmental, industrial and agricultural matrices.

Advances in organic fluorescent probes for bromide ions, hypobromous acid and related eosinophil peroxidase-A review

Elemental bromine is among the essential elements for human health. In living organisms, bromide (Br^-) and hydrogen peroxide (H₂O₂) can be catalyzed by eosinophil peroxidase (EPO) to generate a reactive oxygen species (ROS), hypobromous acid (HOBr), which exhibits properties similar to those of hypochlorous acid (HOCl). Moreover, HOBr possesses strong oxidative and antibacterial properties, which are believed to play an important role in the neutrophil host defense system. However, overexpression or misexpression of HOBr can cause organismal and tissue damage, which is closely related to the development of various diseases. Therefore, an increasing number of studies has demonstrated physiological associations with the conversion of Br^- to HOBr. With the development of fluorescence imaging technology, developing fluorescent probes with novel structures and high selectivity to detect changes in Br^-, HOBr, and the related enzyme EPO levels in organisms has become very important. This paper summarizes Br^-, HOBr, and EPO fluorescent probes reported in recent years, including the design principles, mechanisms, optical properties, and bioapplications. Finally, the application prospects and challenges are also discussed.

N, N’‐Disubstituted Benzimidazolium Salts: Synthesis, Characterization, Micromolar Detection of Fe(III) ions in Aqueous system, Biological Evaluation and Molecular Docking Studies

A series of dicationic N, N’‐disubstituted benzimidazolium salts with Br− and PF6− as the counter anions were synthesized in 75–98 % yields. The single crystal X‐ray diffraction studies of one of the benzimidazolium salts confirmed the structure of these dicationic compounds. These salts exhibited a selective “turn‐off” fluorescence response toward Fe3+ ions in aqueous solution over the other competitive metal ions such as Ag+, Al3+, Ba2+, Ca2+, Co2+, Cr3+, Cu2+, Fe2+, K+, Mg2+, Na+, Ni2+, Pb2+, and Zn2+. Upon addition of 5 equivalents Fe3+ ions, emission intensity was quenched by 94–99 % in pure aqueous media. Detection limits for all probes with Fe3+ ions were found in micromolar range. Further, drug combination analysis was conducted by evaluating the combinatorial treatment effects of two benzimidazolium salts with doxorubicin on breast cancer cells using the Chou‐Talalay method and the Highest Single Agent (HSA) model, and it was found that these compounds showed synergism with doxorubicin. Further, molecular docking studies revealed the best docking score (−6.11) for one of the benzimidazolium salts, and explained its binding affinity with checkpoint kinase 2 (chk2) protein.

Ratiometric fluorescent detection of silver nanoparticles in aqueous samples using peptide-based fluorogenic probes with aggregation-induced emission characteristics

The quantification of silver nanoparticles and Ag⁺ contamination in the aquatic ecosystem has attracted considerable interest. Benzoimidazolyl-cyanovinylene (1) was synthesized as an aggregation-induced emission fluorophore, and a fluorescent peptidyl probe (2 and 3) bearing this fluorophore was developed. The fluorescent peptidyl probes coordinated with Ag⁺ selectively among various metal ions, leading to a ratiometric response to Ag⁺ in pure aqueous solutions. Furthermore, an "in situ" protocol was developed to quantify AgNPs using 2 with H₂O₂ as an oxidizing reagent. The fluorescent detection method for Ag⁺ and AgNPs showed promising detection properties such as high selectivity, high sensitivity, fast response, visible light excitation, well-operations in pure aqueous solution, and large fluorescent signal change. The detection limits of Ag⁺ (0.64 ppb) and AgNPs (1.1 ppb) were significantly low. According to the binding mode study, Ag⁺ induced the formation of a 2:1 complex between 2 and Ag⁺ and the chirality of the peptide part of the probe was not critical for this process. The formation of aggregates of the probe triggered by Ag⁺ from AgNPs induced a significant change in fluorescence. Furthermore, the amounts of spiked AgNPs in groundwater and tap water were quantified using the fluorescent detection method with 2.

Lansoprazole-Based Colorimetric Chemosensor for Efficient Binding and Sensing of Carbonate Ion: Spectroscopy and DFT Studies

The new benzimidazole based receptor Lansoprazole has been used to detect carbonate anion by naked-eye and Uv-Vis spectroscopy. This receptor revealed visual changes withCO 3 2 - anion in ethanol. No detectable color changes were observed upon the addition of any other tested anions. The lansoprazole chemosensor selectively recognizesCO 3 2 - ion over the other interference anions in the ethanol, followed by deprotonation and reflected 1:1 complex formation between the receptor and the carbonate ion. Lansoprazole exhibits splendid selectivity toward carbonate ion via a visible color change from colorless to yellow with a detection limit of 57 μM. The binding mode ofCO 3 2 - to receptor L is supported by Density Functional Theory calculation. Moreover, this receptor shows a practical visible colorimetric test strip for the detection of carbonate ions. The transition states calculation demonstrates the occurrence of reaction from L to L-CO 3 2 - after overcoming an energy barrier of 10.1 kcal/mol, and there is considerable interaction energy between L andCO 3 2 - (94.9 kJ/mol), both of which confirmed that receptor L has high sensitivity and selectivity to the carbonate ion. The theoretical studies were performed to acquire an electronic description of the complexation mechanism byCO 3 2 - as well as to study bonding and structure in the complex. The optimized structures and binding mechanisms were supported with a high correlation and agreement by spectroscopy and DFT calculations.