Fluorimetric Recognition of Nerve Agent Mimic Diethylchlorophosphate Along with Cu2+/Hg2+ Ions Using Imidazole Possessing Sensor

An imidazole possessing sensor (1) has been designed and developed by simple one step reaction and characterization was done by using common spectroscopic methods. The fluorimetric sensing of nerve agent mimic, DCP, was carried out by observing blue shift in spectra accompanied with quenching in semi-aqueous solvent. The sensor was found proficient for the detection of DCP amongst other phosphates with detection limit of 69 nM. Furthermore, upon incorporation of various metal ions to CH₃CN:H₂O (4:1, v/v) solution of 1 (λ_ex 340 nm), the fluorescent probe turned non-fluorescent only in presence of Cu²⁺/Hg²⁺ ions. This was accompanied by fluorescent color change from light blue to yellow in case of Hg²⁺ and colorless in case of Cu²⁺ ions. Moreover, practical applications of sensor 1 were investigated for recognition of Cu²⁺ and Hg²⁺ ions in real water samples along with the detection of DCP in soil samples from different areas. Differential emission changes observed with addition of Hg²⁺ ions and DCP led to observation of "NOR" and an "INHIBIT" molecular photonic logic operations at 446 and 385 nm, respectively.

Recent Advances in Luminescent Recognition and Chemosensing of Iodide in Water

This Minireview covers the latest developments of chemosensors based on transition-metal receptors and organic fluorophores with specific binding sites for the luminescent detection and recognition of iodide in aqueous media and real samples. In all selected examples within the last decade (made-post 2010), the iodide sensing and recognition is probed by monitoring real-time changes of the fluorescence or phosphorescence properties of the chemosensors. This review highlights effective strategies to iodide sensing from a structural approach where the iodide recognition/sensing process, through supramolecular interactions as coordination bonds, hydrogen bonds, halogen bonds and electrostatic interactions, is transduced into an optical change easily measurable. The selective iodide sensing is an active field of research with global interest due to the importance of iodide in biological, medicinal, industrial, environmental and chemical processes.

A nanomolar detection of mercury(II) ion by a chemodosimetric rhodamine-based sensor in an aqueous medium: Potential applications in real water samples and as paper strips

A new promising rhodamine based colorimetric and fluorometric chemosensor, RDV has been designed and synthesized for specific detection of Hg²⁺ ion. It acts as highly selective "turn-on" fluorescent chemosensor for Hg²⁺ ion without interference from other competitive metal ions in aqueous acetonitrile medium. The drastic color change with addition of Hg²⁺, from colorless to pink, indicates RDV can acts as "naked-eye" indicator for Hg²⁺. The Hg²⁺ promoted selective hydrolysis of appended vinyl ether group in RDV followed by Hg²⁺ chelated complex formation with concomitant opening of spirolactam ring is the plausible sensing mechanism. The detailed absorption, fluorescence, ¹H NMR, ¹³C NMR and mass spectrometry confirms the proposed sensing mechanism. The limit of detection (LOD) of Hg²⁺ by RDV is 136 nM indicating the high sensitivity towards Hg²⁺. The RDV shows consistent spectroscopic response in biological pH range 4-10. In addition to explore practical applicability of RDV, its paper strips have been made and used to detect Hg²⁺ in pure water solution up to 10 ppm level. Furthermore, the potential application of RDV for the sensing of Hg²⁺ in real water samples (tap water and drinking waters from different sources) were also monitored and demonstrated.

Cascade recognition of Hg2+ and cysteine using a naphthalene based ESIPT sensor and its application in a set/reset memorized device

An optical ESIPT sensor for Hg²⁺ and cysteine based on a naphthalene platform (1) was designed and synthesized by a one step reaction and characterized by using common spectroscopic techniques.

Protonation-induced ultrafast torsional dynamics in 9-anthrylbenzimidazole: a pH activated molecular rotor

Protonation activated molecular rotor property is demonstrated in 9-anthrylbenzimidazole which probes a wide range of viscosity selectively at acidic pH (pH < 5).

Cholesterol-Appended Benzimidazolium Salts: Synthesis, Aggregation, Sensing, Dye Adsorption, and Semiconducting Properties

A series of cholesterol-appended benzimidazolium salts 1-9 have been designed and synthesized. They have been explored in gel chemistry. The gelation of the benzimidazolium salts is dependent on the nature of the counteranions. In addition, the gelation behavior of the gelators is linked with the presence of both π-stacking and cholesteryl motifs. Whereas bisbenzimidazolium salt 2 forms a gel in dimethylsulfoxide/H₂O (1:1, v/v) itself, under similar conditions, monobenzimidazolium salts 4 and 6 exhibit gelation in the presence of F^- ions and validate the visual sensing of F^-. As an application, the gel phase of 2 efficiently removes toxic dyes from waste water. Furthermore, all gels show thermally activated semiconducting property within a wide voltage window.

Carbazolic Porous Framework with Tetrahedral Core for Gas Uptake and Tandem Detection of Iodide and Mercury

A multifunctional carbazolic porous framework (Cz-TPM), with a tetrahedral core, has been synthesized by FeCl₃ oxidative coupling polymerization. The Brunauer-Emmett-Teller surface area of the obtained polymers reaches 713.2 m² g^-1. Gas adsorption isotherms show that Cz-TPM exhibits large carbon dioxide (97.9 mg g^-1, 9.8 wt %, 273 K, and 1 bar) and hydrogen uptake capacities (149.3 cm³ g^-1, 1.34 wt %, 77 K, and 1 bar). Furthermore, Cz-TPM has been found to display tandem visual detection of iodide and mercury, respectively. The Cz-TPM dispersion turns to yellow in the presence of iodide salts and subsequently changes to nearly colorless on addition of Hg²⁺ salts that could be easily observed by the naked eye. Cz-TPM can detect I^- via "turn off" fluorescence quenching, and then the in situ generated Cz-TPM@I complexes can recognize Hg²⁺ ions via "turn on" fluorescence recovery. More importantly, Cz-TPM is stable over common solvents and can be easily recovered by excessive water washing and centrifugation for further repeated use. As far as we know, carbazolic porous organic frameworks enabling detection of I^- and Hg²⁺ have not been reported.

A reusable multichannel anthraimidazoledione-based receptor for Hg2+and Cu2+ions: ultrasensitive, economical and facile detection of Hg2+in real water sources through fluorescence readout

A multichannel, ultrasensitive and selective receptor (1) has been developed for practical detection of Hg²⁺in various drinking waters.

Hierarchical self-assembly of switchable nucleolipid supramolecular gels based on environmentally-sensitive fluorescent nucleoside analogs

Exquisite recognition and folding properties have rendered nucleic acids as useful supramolecular synthons for the construction of programmable architectures. Despite their proven applications in nanotechnology, scalability and fabrication of nucleic acid nanostructures still remain a challenge. Here, we describe a novel design strategy to construct new supramolecular nucleolipid synthons by using environmentally-sensitive fluorescent nucleoside analogs, based on 5-(benzofuran-2-yl)uracil and 5-(benzo[b]thiophen-2-yl)uracil cores, as the head group and fatty acids, attached to the ribose sugar, as the lipophilic group. These modified nucleoside-lipid hybrids formed organogels driven by hierarchical structures such as fibers, twisted ribbons, helical ribbons and nanotubes, which depended on the nature of fatty acid chain and nucleobase modification. NMR, single crystal X-ray and powder X-ray diffraction studies revealed the coordinated interplay of various non-covalent interactions invoked by modified nucleobase, sugar and fatty acid chains in setting up the pathway for the gelation process. Importantly, these nucleolipid gels retained or displayed aggregation-induced enhanced emission and their gelation behavior and photophysical properties could be reversibly switched by external stimuli such as temperature, ultrasound and chemicals. Furthermore, the switchable nature of nucleolipid gels to chemical stimuli enabled the selective two channel recognition of fluoride and Hg(2+) ions through visual phase transition and fluorescence change. Fluorescent organogels exhibiting such a combination of useful features is rare, and hence, we expect that this innovative design of fluorescent nucleolipid supramolecular synthons could lead to the emergence of a new family of smart optical materials and probes.

Regioselective synthesis of 3-anthracenyloxindoles and 3-carbazolyloxindoles by indium(iii)-catalyzed direct arylation and their fluorescent chemosensor properties

An efficient protocol for diverse 3-anthracenyloxindoles and 3-carbazolyloxindoles has been developed by In(OTf)₃-catalyzed direct arylation of 3-diazooxindoles with anthracenes or carbazoles.