An Anthracene-Imidazoanthraquinone Conjugate Exhibiting Ratiometric Fluorescence Turn - on Behavior with CN- and F- Anions

A new conjugate, 2-(4-(anthracen-9-yl) phenyl)-[1,2-d]imidazole-1H-anthraquninone (AQI) has been designed and synthesized as a molecular probe 4. The photophysical and electrochemical behavior of the probe in the absence and presence of different class of ions were examined in acetonitrile solution. The probe 4 with F- and CN- anions showed ratiometric fluorescence "turn - On" response due to variation in ICT processes. Cyclic voltammetry of probe exhibited reversible redox behavior wherein the band gap (Eg =1240/λmax) of probe (ΔE =3.220 eV) decreased (~2.583 eV) after the interaction with F- and CN- anions. The probe interacted with both anions in a 1 : 1 stoichiometry with good binding constants (KF -=.05×106 M-1 and KCN - = 1.46×106 M-1) and limit of detection/quantification (LOD/LOQ) in nM range. pH studies showed that probe 4 has potential to detect the anions under physiological conditions (between pH 6-10). The probe upon interaction with both F- and CN- anions showed a naked-eye sensitive color change in solution and on test paper strips. The probable complexes, 4+F-/CN- upon interaction with trifluoroacetic (TFA) acid showed reversible behavior wherein the intensity of probe rejuvenated. The output emission signal of the probe upon providing F- and TFA as a chemical inputs mimic the function of a memory device with ''write-read-erase-read'' functions and has also been utilized to construct a molecular key-pad lock security device system. Also, the probe showed sensitivity to detect the F- in toothpaste. The mechanism of interaction has been confirmed by different spectroscopic data analysis.

Highly Selective and Scalable Molecular Fluoride Sensor for Naked-Eye Detection

Fluoride is widely present in nature, and human exposure to it is generally regarded as inevitable. High levels of fluoride intake induce acute and chronic illnesses. To reduce potential harm to the general public, it is essential to create selective fluoride detectors capable of providing a colorimetric response for naked-eye detection without the need for sophisticated equipment. Here, we report a one-pot synthesis of four different diaminomaleonitrile-derived Schiff base sensors. The terephthalaldehyde adduct provided a strong color change visible to the naked eye at a F- concentration level as low as 2 ppm. From the evaluation against other anions, such as CN-, I-, Br-, Cl-, NO3-, PO43-, OAc-, and HSO4-, the molecular sensor displayed a visible color change exclusively upon exposure to fluoride, underscoring exceptional selectivity. As a key intermediate for understanding the mechanism, HF2- was confirmed by 19F nuclear magnetic resonance. Theoretical calculations suggested a deprotonation-triggered bathochromic shift brought about by the unique electronic structure of the sensor. Furthermore, the simple synthetic protocol from economically accessible materials allowed for the preparation of the compound on a large scale, rendering it a highly practical visual fluoride sensor.

Structural and optical studies of fluoride ion binding using N-heteroaromatic ligands

8-Hydroxyquinoline and imidazole, two important N-heteroaromatic systems, have a strong affinity towards various anions via their acidic OH or NH protons. Three receptor ligands, 5-(1H-benzo[d]imidazol-2-yl)quinolin-8-ol (1), 5-(benzo[d]thiazol-2-yl)quinolin-8-ol (2), and 4-(1H-benzo[d]imidazol-2-yl)benzene-1,3-diol (3), were synthesized, and their fluoride (F-) ion binding properties were investigated. These ligands could selectively bind F- ions, and their respective F- complexes, namely, 1-TBAF, 2-TBAF, and 3-TBAF (TBAF = tetrabutylammonium fluoride), were characterized using single crystal X-ray analysis, NMR, UV-vis, Hirshfeld surface (HS) analysis and computational studies. Their solid-state structural analysis revealed that in each case, the F- ion is strongly bound within the receptor molecule scaffold through NH, OH, and aryl-CH hydrogen bonding interactions. In the case of 1-TBAF and 3-TBAF, F- binding is further strengthened by the inclusion of water molecules, forming fluoride-water cluster complexes. 1H NMR study exhibited the disappearance of NH and OH proton signals upon the addition of TBAF, indicating that the NH and OH protons are the primary sites for F- ion coordination. UV -vis absorbance spectra was used to study their lowest sensing limits towards F- ions. Ligands 1 and 2 showed good responsiveness towards F- ions at concentrations ≥0.5 μM, with obvious changes occurring at F- concentrations of 180 and 12 μM, respectively. HS analysis quantified non-covalent interatomic contacts between the atoms and fluoride ions, revealing that 1-TBAF contributed a maximum of 19.2% of all atoms⋯F contacts to the HS. Density functional theory studies were carried out on the 1-TBAF, 2-TBAF, and 3-TBAF crystal systems, and the band structure and total density of states of the systems were evaluated. The optical response of 2-TBAF was also investigated.

In Situ Ni(II) Complexation Induced Deprotonation of Bis-Thiourea-Based Tweezers in DMSO-Water Medium: An Approach toward Recognition of Fluoride Ions in Water with Organic Probe Molecules

Recognition of fluoride in water through the fluoride-induced Brönsted acid-base deprotonation reaction of an organic probe molecule is still a challenging task owing to the lower basicity of fluoride ions and the instability of the conjugate base of the probe molecules in aqueous medium. Herein, we report a complementary strategy in which the conjugate base of the studied bis-thiourea molecule in dimethyl sulfoxide (DMSO) medium is simultaneously stabilized through chelation of the Ni(II) ion, which eventually facilitates the recognition of the fluoride ion in water samples. The recognition methodology is validated colorimetrically and electrochemically, and finally, the applicability of the approach is explored with water samples collected from fluoride-affected areas. The limit of detection value for the fluoride ion in water medium was found to be 0.2 and 0.3 ppm with UV-visible spectroscopy and differential pulse voltammetry measurements, respectively. The methodology is also demonstrated on a paper strip for the detection of the fluoride ion with the naked eye and a smartphone-based RGB sensor. The scheme has been shown to be effective in enhancing the aqueous fluoride recognition ability of the organic probe molecules with acidic hydrogen prone to deprotonation by the fluoride ion.

Tuning sensing efficacy of anthraimidazoledione-based charge transfer dyes: nitro group positioning impact

Anthraimidazoledione-based optical sensors have been designed by varying the position of the nitro functional group. All three positional isomers showed highly colored, photostable optical signals owing to intramolecular charge transfer interactions. Despite having the same anion-binding site (imidazole unit), the selectivity and sensitivity of the compounds depend on the positioning of the nitro group. The selectivity was fairly good for the meta isomer, followed by the ortho and para isomers, respectively. In contrast, the sensitivity towards anions followed a completely opposite trend, with the para isomer being the most sensitive one towards anions. Interestingly, the color changing response along the turn-on fluorescence signal was observed only with CN- ions in a semi-aqueous environment. Though the introduction of water as a co-solvent could improve the selectivity, the sensitivity was found to be slightly less than that observed in pure organic medium. Mechanistic studies indicated hydrogen bonding interactions between the imidazole -NH proton and cyanide, which further facilitated the extent of intramolecular charge transfer.

A comparative performance evaluation of cephalosporin's drugs for fluoride recognition

In this manuscript, readily available cephalosporin's drugs cefuroxime axetil (L1) cefpdoxime proxetil (L2), and cefditoren pivoxil (L3) possess dihydrothiazine ring as signaling unit, and -NH groups as the binding site were used for the sensing of fluoride (F^-) ions. In the presence of F^-, the drug selectively portrayed a naked-eye detectable color change from colorless. The binding constant of 1:1 stoichiometric complex of L1, L2, and L3 with F^- was found to be 2.36 × 10⁴ M^-1, 2.44 × 10³ M^-1 and 1.02 × 10⁴ M^-1 respectively. The lowest detection limit (LOD) of F^- was found to be 11 µM (209 ppb) with drug L1 and L2. The binding mechanism of the drug with F^- was studied by ¹H and ¹⁹F nuclear magnetic resonance (NMR) spectral titration, electrospray ionization mass spectra (ESI-MS) analysis, and density functional theory (DFT) studies. The presence of F^- was monitored in various spiked water and Colgate toothpaste samples. Overall, cephalosporin's drug demonstrates a promising potential for the detection of F^- ions in the semi-aqueous phase.

Spectroscopic and Density Functional Studies on the Interaction of a Naphthalene Derivative with Anions

This article highlights the investigation of anion interactions and recognition abilities of naphthalene derivative, [(E)-1-(((4-nitrophenyl)imino)methyl)naphthalen-2-ol], (NIMO) by UV-visible spectroscopically and colorimetrically. NIMO shows selective recognition of F^- ions colorimetrically, and a visual color change from yellow to pink is observed by the naked eye. The F^- ions recognition is fully reversible in the presence of HSO₄^- ions. The limit of F^- ions detection by NIMO could be possible down to 0.033 ppm-level. A paper strips-based test kit has been demonstrated to detect F^- ions selectively by the naked eye, and a smartphone-based method for real sample analysis in the non-aqueous medium has also been demostrated. Spectroscopic behavior is well supported by pK_a value calculation and DFT analysis, to find a correlation with receptor analyte interaction. The optical response of NIMO towards the accumulation of F^- ions and, subsequently, HSO₄^- ions as chemical inputs provides an opportunity to construct INH and IMP molecular logic gates.

Aryl-Phenanthro[9,10-d]imidazole: A Versatile Scaffold for the Design of Optical-Based Sensors

Fluorescent and colorimetric sensors are important tools for investigating the chemical compositions of different matrices, including foods, environmental samples, and water. The high sensitivity, low interference, and low detection limits of these sensors have inspired scientists to investigate this class of sensing molecules for ion and molecule detection. Several examples of fluorescent and colorimetric sensors have been described in the literature; this Review focuses particularly on phenanthro[9,10-d]imidazoles. Different strategies have been developed for obtaining phenanthro[9,10-d]imidazoles, which enable modification of their optical properties upon interaction with specific analytes. These sensing responses usually involve changes in the fluorescence intensity and/or color arising from processes like photoinduced electron transfer, intramolecular charge transfer, intramolecular proton transfer in the excited state, and Förster resonance energy transfer. In this Review, we categorized these sensors into two different groups: those bearing formyl groups and their derivatives and those based on other molecular groups. The different optical responses of phenanthro[9,10-d]imidazole-based sensors upon interaction with specific analytes are discussed.

Novel Quinoline-Derived Chemosensors: Synthesis, Anion Recognition, Spectroscopic and Computational Study

Fluorescent-small molecules offer an excellent source of chemosensors when optimized for detection of anions with sensitivity and selectivity, low-cost and robust synthesis. In the present study we synthesized new quinoline-based...

Imidazopyridine–fluoride interaction: solvent-switched AIE effects via S⋯O conformational locking

Imidazopyridine-based carboxamide exhibiting the aggregation-induced emission phenomenon works effectively in fluoride ion detection through H-bond interaction and subsequent deprotonation.

Regioselective synthetic approach for key precursors of 6-aryl benzo[c]phenanthridin-10-ol derivatives: A useful compound for selective chromogenic recognition of fluoride

A regioselective synthetic strategy for 6-aryl-8,9-dihydro-benzo[c]phenanthridine-10(7H)-ones (4) is accomplished using a one-pot four-component reaction by fine-tuning of reaction temperature. DMSO is excellently used as a reactant-cum-solvent to introduce carbonyl functionality...

Coumarin based thiosemicarbazones as effective chemosensors for fluoride ion detection

Anion sensing have attained immense importance as these charged ions are prevailing in agriculture industry and in heavy industry and therefore in the environment around us, chemosensors are commencing to claim several applications as their role is being better perceived day by day. In the current study, coumarin based thiosemicarbazone R-1 (phenyl moiety) and R-2 (benzyl moiety) were synthesized. It was observed that there were variations in the sensing patterns of compound bearing benzyl group, as compared to the simple phenyl group bearing receptor. Different techniques were used to confirm the interaction of coumarin based receptors with anions. These techniques included naked-eye test, UV-visible, 1H NMR, and fluorescence spectroscopic techniques. The synthesized receptors showed selectivity for fluoride ions. Benesi-Hildebrand equation was employed for determining the detection limits and binding constants values. The synthesized receptors were employed as efficient chemosensors in real life samples and satisfactory results were obtained.

B(C6F5)3-catalyzed three-component tandem reaction to construct novel polycyclic quinone derivatives: synthesis of a carbonate salt chromogenic chemosensor

A series novel polycyclic quinone derivatives were constructed providing a carbonate salt chromogenic chemosensor.

Effect of Substitution at Amine Functionality of 2,6-Diaminopyridine-Coupled Rhodamine on Metal-Ion Interaction and Self-Assembly

2,6-Diaminopyridine-coupled rhodamines 1 and 2 have been synthesized, and the effect of substitution on amine functionality toward metal-ion interactions and self-assembly is thoroughly investigated. Both the compounds effectively recognize different metal ions of biological significance fluorimetrically and colorimetrically with a high degree of selectivity and sensitivities. While compound 1 is sensitive to Fe³⁺ ions, compound 2 is responsive to both Fe³⁺ and Al³⁺ ions in aqueous CH₃CN (4/1, v/v; 10 mM tris HCl buffer, pH 6.8). The sensing mechanism involves the metal-ion chelation-induced spirolactam ring opening of the rhodamine scaffold that results in both color and fluorescence changes, while the extent of interactions with the metal ions is truly governed by the chemical structure of the compounds. Both 1 and 2 are proficient in detecting Fe³⁺ and Al³⁺ ions in human lung cancer cells (A549). As new findings, unlike 1, compound 2 formed a faint pink gel in the toluene-hexane mixture solvent (1:1, v/v), and the gel state of 2 selectively recognizes Ag⁺ ions by exhibiting a phase change from gel to purple sol. Experimental findings establish the role of the formamide moiety in forming the self-assembly.

Crystallographic Elucidation of Stimuli-Controlled Molecular Rotation for a Reversible Sol-Gel Transformation

To get an idea about the most probable microporous supramolecular environment in the gel state, gelator molecule 1 has been crystallized from its gelling solvent (dimethylformamide). Crystal structure analysis of 1 shows a strong π···π stacking interaction between the electron-deficient pentafluorophenyl ring and electron-rich naphthyl ring. The gelling solvent situated in the "molecular pocket" stitches the gelators through weak H-bonding interactions to facilitate the formation of an organogel. Scanning electron microscopy analysis exhibits a ribbonlike fibrous morphology that resembles the supramolecular arrangement of 1 in its crystalline state, as evidenced by powder X-ray diffraction. In the presence of external stimuli (tetrabutylammonium fluoride), the organogel of 1 disassembles into sol. This sol-gel transformation phenomenon has been explained on the basis of X-ray single-crystal analysis. Single crystals obtained from the sol state show that naphthylic -OH of 1 gets deprotonated, resulting in C-C bond rotation that plays a major role in the sol-gel transformation. Gelator 1 exhibits weak green fluorescence in the gel state, whereas it shows highly intense yellow fluorescence in the sol state. Furthermore, a reversible sol-gel transformation associated with changes in the spectroscopic properties has been observed in the presence of acids and fluoride ions, respectively.

A Novel Thiophene-Based Fluorescent Chemosensor for the Detection of Zn2+ and CN-: Imaging Applications in Live Cells and Zebrafish

A novel fluorescent turn-on chemosensor DHADC ((E)-3-((4-(diethylamino)-2-hydroxybenzylidene)amino)-2,3-dihydrothiophene-2-carboxamide) has been developed and used to detect Zn2+ and CN-. Compound DHADC displayed a notable fluorescence increase with Zn2+. The limit of detection (2.55 ± 0.05 μM) for zinc ion was far below the standard (76 μM) of the WHO (World Health Organization). In particular, compound DHADC could be applied to determine Zn2+ in real samples, and to image Zn2+ in both HeLa cells and zebrafish. Additionally, DHADC could detect CN- through a fluorescence enhancement with little inhibition with the existence of other types of anions. The detection processes of compound DHADC for Zn2+ and CN- were demonstrated with various analytical methods like Job plots, 1H NMR titrations, and ESI-Mass analyses.

Design and synthesis of stable indigo polymer semiconductors for organic field-effect transistors with high fluoride sensitivity and selectivity

We report the design and synthesis of two novel indigo donor-acceptor (D-A) polymers, PIDG-T-C20 and PIDG-BT-C20, comprising an indigo moiety that has intramolecular hydrogen-bonds as the acceptor building block and thiophene (T) and bithiophene (BT) as the donor building block, respectively. PIDG-T-C20 and PIDG-BT-C20 exhibited characteristic p-type semiconductor performance, achieving hole mobilities of up to 0.016 and 0.028 cm2 V-1 s-1, respectively, which are highest values reported for indigo-based polymers. The better performing PIDG-BT-C20 was used for the fabrication of water-gated organic field-effect transistors (WGOFETs), which showed excellent stability at ambient conditions. The PIDG-BT-C20-based WGOFETs exhibited rapid response when fluoride ions were introduced to the water gate dielectric, achieving a limit of detection (LOD) of 0.40 mM. On the other hand, the devices showed much lower sensitivities towards other halide ions with the order of relative response: F- ≫ Cl- > Br- > I-. The high sensitivity and selectivity of PIDG-BT-C20 to fluoride over other halides is considered to be realized through the strong interaction of the hydrogen atoms of the N-H groups in the indigo unit with fluoride ions, which alters the intramolecular hydrogen-bonding arrangement, the electronic structures, and thus the charge transport properties of the polymer.

Revisiting the fluoride binding behaviour of dipyrrolylquinoxaline in aqueous medium: a copper ion mediated approach

An ion detection methodology employing synergistic interaction between copper(ii) ions and fluoride with 2,3-dipyrrol-2′-yl-quinoxaline (SR1) is investigated with a particular target to detect fluoride in an aqueous environment.

Excited State Interaction of Ruthenium (II) Imidazole Phenanthroline Complex [Ru(bpy)2 ipH]2+ with 1,4-Benzoquinone: Simple Electron Transfer or Proton-Coupled Electron Transfer?

The unidirectional proton coupled electron transfer (PCET) from the excited state of Ru(II) imidazole phenanthroline complex [Ru(bpy)₂ ipH]²⁺ to 1,4-benzoquinone, was studied by steady-state (SS) and time-resolved (TR) fluorescence and transient absorption (TA) measurements. The pK_a (9.7) and pK_a * (8.6) values of the complex suggest that it behaves as a photoacid on excitation. The difference in the quenching rates obtained from SS and TR fluorescence studies indicate participation of both dynamic quenching and static quenching involving the hydrogen bonded ipH ligand of [Ru(bpy)₂ ipH]²⁺ with the 1,4-benzoquinone quencher, formed in the ground state. Within the hydrogen bonded complex, the ruthenium centre acts as the electron donor, while the ipH ligand acts as the proton donor to the hydrogen bonded 1,4-benzoquinone that acts simultaneously both as the electron and proton acceptor. It is proposed that the static quenching in the hydrogen bonded [Ru(bpy)₂ ipH]²⁺ -1,4-benzoquinone pairs occurs involving the PCET mechanism, while the dynamic quenching occurs through the simple ET mechanism, on diffusional encounter of the isolated 1,4-benzoquinone with the excited [Ru(bpy)₂ ipH]²⁺ complex. The occurrence of broad TA bands around 420-430 nm suggests formation of both 1,4-benzoquinone radical anion as well as the 1,4-benzosemiquinone radical by the interaction of excited [Ru(bpy)₂ ipH]²⁺ with 1,4-benzoquinone, thus supporting the ET process in the studied system.

Cobalt complexes with redox-active anthraquinone-type ligands

Three anthraquinone-type multidentate ligands, HL1-3 (HL = 2-R-1H-anthra[1,2-d]imidazole-6,11-dione; HL1: R = (2-pyridyl), HL2; R = (4,6-dimethyl-2-pyridyl), HL3; R = (6-methoxy-2-pyridyl)), were prepared, and their complexation behaviour was investigated. Three bis-chelate cobalt complexes with the formula [CoII(L1-3)2]·n(solv.) (1, 2, and 3 for HL1, HL2, and HL3, respectively), in which the ligands adopted tridentate binding modes, were synthesized and structurally characterized by single-crystal X-ray analyses. Electrochemical studies of 1-3 in CH2Cl2 reveal three reversible redox waves, assigned to ligand and cobalt-centred processes. Additional complexes were obtained in which HL1 adopted a bidentate binding mode, stabilising the mono-chelate [CoII(HL1)(NO3)2(DMF)2] (4) species and tris-chelate [CoIII(L1)3] (5) complex in which the cobalt ion was in its 3+ state. The electrochemical properties of complex 5 were investigated in DMF, and the Co(ii)/Co(iii) redox couple was found to be negatively shifted compared to that of complex 1, while the ligand-based processes became irreversible. Tridentate chelation is found to stabilise the anthraquinone ligands and unlocks their redox multi-stability.

Bifunctional colorimetric chemosensing of fluoride and cyanide ions by nickel-POCOP pincer receptors

Three Ni(ii)-POCOP pincer complexes [NiCl{C₆H₂-4-OH-2,6-(OPPh₂)₂}], 1; [NiCl{C₆H₂-4-OH-2,6-(OPtBu₂)₂}], 2 and [NiCl{C₆H₂-4-OH-2,6-(OPiPr₂)₂}], 3 were studied as bifunctional molecular sensors for inorganic anions and acetate. In CH₃CN, fluoride generates a bathochromic shift with a colorimetric change for 1-3 with a simultaneous fluorescence turn on, this optical effect is based on deprotonation of the para-hydroxy group of the POCOP ligand. On the other hand, in a neutral aqueous solution of 80 vol% CH₃CN, additions of cyanide produce a distinct change of color by forming very stable complexes with the nickel-based receptors 1-3 with log K_a in the range of 4.38-5.03 M^-1 and pronounced selectivity over other common anions such as iodide, phosphate, and acetate. Additionally, bromide shows a modest spectral change and affinity, but lower than those observed for cyanide. On the basis of ¹H NMR experiments, UV-vis titrations, ESI-MS experiments, and the crystal structure of the neutral bromo complex of 1, it is proposed that the colorimetric change involves an exchange of chloride by CN^- on the Ni(ii) atom. The Ni(ii)-based sensor 1 allows the fluorescent selective detection of fluoride with a limit of 5.66 μmol L^-1 and colorimetric sensing of cyanide in aqueous medium in the micromolar concentration range.

Donor–π–acceptor (D–π–A) dyad for ratiometric detection of Hg2+ and PPi

A donor–π–acceptor (D–π–A) dyad 1 has been successfully synthesized by linking phenanthrenequinone as an electron donor unit and anthraquinone as an electron acceptor unit through a phenyl ring.

A highly sensitive pyridine-dicarbohydrazide based chemosensor for colorimetric recognition of Cu2+, AMP2−, F− and AcO− ions

A single colorimetric chemosensor for the detection of both Cu²⁺ and AMP²⁻ ions has been developed for the first time.

Detection of cyanide ions in aqueous solutions using cost effective colorimetric sensor

Cyanide (CN̄) is one of the most toxic material to the human and environment. It is very important to develop the diagnostic tools for the detection of CN̄ ions. Moreover, detection of the ions in an aqueous medium is a challenging task as water molecules interfere with the sensing mechanism. In this context, we prepared chemical sensor, S1, having anthraquinone as a signaling unit and thiourea as a binding site. This sensor exhibited distinct visual color and spectral changes in response to CN̄ ion over other testing anions in 50% aq. DMSO solution. However, in 20% aq. DMSO solution, S1 exhibited obvious spectral and color changes in response to CN̄, fluoride (F̄), acetate (Ac̄) and benzoate (Bz̄). Another sensor, S2, having a same signaling unit with that of S1, but a different binding site of urea group. In contrast to S1, S2 exhibited obvious spectral and color changes to F̄ in 2.5% aq. DMSO solution. NMR titration results suggested that the spectral and colorimetric responses were due to the formation of host-guest complex and deprotonation events. Finally, economically viable paper-based colorimetric "test stripes" of S1 were fabricated to detect the CN̄ ions in 100% aqueous solution.

Anthraimidazoledione Based Reversible and Reusable Selective Chemosensors for Fluoride Ion: Naked-Eye, Colorimetric and Fluorescence "ON-OFF"

Novel anthraimidazoledione-based compounds (1-3) are synthesized as selective colorimetric and fluorescent sensors for fluoride ion. The binding properties of the probes (1-3) are studied with different anions in acetonitrile solvent. Spectral red shifts in the absorption spectra and 'turn-off' emission are observed when fluoride is added to 1-3. The striking green to orange color change in the ambient light is thought to be due to the deprotonation of the N-H proton of the imidazole moiety of the probes by the basic F^- ion. Interestingly, in all three cases the nonfluorescent probe-F^- solutions, on treatment with copper perchlorate, show distinct color change from orange to golden yellow with resumption of fluorescence intensity. Furthermore, the reversibility of sensors (1-3) for the detection of F^- ion is tested for four cycles indicating that "ON-OFF-ON" mechanism is operative. Test strip based on sensor 2 acts as a reusable cost-effective F^- sensor.

A novel dual-channel chemosensor for CN− based on rhodamine B hydrazide derivatives and its application in bitter almond

We successfully designed and synthesized a novel chemosensor PW bearing rhodamine B hydrazide and 8-formyl-7-hydroxyl-4-methylcoumarin, which displayed both colorimetric and “turn-on” fluorescence responses for CN⁻ in DMSO/H₂O (1 : 1, v/v, pH = 7.20) solution.

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.

Selective and sensitive colorimetric sensor for CN− in the absence and presence of metal ions (Cu2+/Ni2+): mimicking logic gate behaviour

Enone based anion sensors have significance due to their colorimetric reaction upon deprotonation and variable occurrence in the conjugated moiety.