Colorimetric and Fluorimetric Detection of Fe(III) Using a Rhodamine-Imidazole Hydrazone Based Chemosensor: Photophysical Properties, DFT, TGA, and DSC Studies

Rhodamine-imidazole hydrazones (RIH-1 & RIH-2) based chemosensors have been synthesized. These are characterised and evaluated by FT-IR spectroscopy, 1H-NMR, 13C-NMR, LCMS, absorption and fluorescence spectroscopy. These chemosensors exhibit enhanced sensitivity and selectivity in detecting the biologically significant Fe3+ metal ion through both colorimetric and fluorescence changes. The optical properties have been investigated using binary acetonitrile-water (7:3 v/v) semi-aqueous solution. The probe RIH-1 can be deployed as a fluorescent and colorimetric probe for the detection of Fe3+ ion. It shows an absorption band at 559 nm and an intensity band at 579 nm increasing up to 50-fold with the increase in the concentration of Fe3+ with the detection limit as low as 11nM. In the visible light, RIH-1 helps in the detection of Fe3+ ion through the naked eye, while the addition of Fe3+ to the probe RIH-1 results in a colour change from colourless to pink. This is primarily due to the opening of the lactone ring in RIH-1. Notably, RIH-1 probe displays a high quantum yield of 0.51, after binding with Fe3+ ions. Indeed, it has been found that sensor RIH-1 is very effective in sensing Fe3+ ions through both fluorescence based and visual detection methods. Additionally, DFT studies of these chemosensors have been evaluated, TGA and DSC analysis showed good thermal stability.

Diethylaminophenol appended pyrimidine bis hydrazone for the sequential detection of Al3+ and PPi ions

In this study, a novel easy-to-prepare diethylaminophenol appended pyrimidine bis hydrazone (HD) has been designed and developed. The probe exhibits excellent sequential sensing characteristics towards Al3+ and PPi ions. The emission studies, various spectroscopic techniques and lifetime results have been utilized to understand the binding mechanism of HD with Al3+ ions and, to discover the specificity as well as the efficacy of the probe in sensing Al3+ ions. The good association constant in addition to the lower detection limit values makes the probe effective for the detection of Al3+. The in-situ produced HD-Al3+ ensemble could consecutively detect PPi via a turn-off fluorescence response and the selectivity and sensitivity characteristics of the generated ensemble towards PPi were described based on the demetallation approach. The overall sensing property of HD was perfectly employed for constructing logic gates, real water, and tablet applications. Paper strips, as well as cotton-swab experiments, were also conducted inorder to check the practical utility of the synthesized probe.

A rhodamine based chemodosimeter for the detection of Group 13 metal ions

A new rhodamine derivative, HL-CIN, derived from a reaction between N-(rhodamine-6G)lactam-ethylenediamine (L1) and trans-cinnamaldehyde, is reported here for the colorimetric and fluorogenic sensing of Group 13 trivalent cations, namely Al³⁺, Ga³⁺, In³⁺ and Tl³⁺. The absorption intensity of the probe increases significantly at 530 nm whereas the fluorescence intensity enhances massively at 558 nm upon interaction with these metal ions. Other relevant metal ions could not impart any noticeable color change or fluorescence enhancement. The quantum yield or fluorescence life time of HL-CIN increases considerably in the presence of these Group 13 metal ions. Different spectral studies such as ESI-mass, FT-IR, ¹H and ¹³C NMR spectra, establish that HL-CIN undergoes hydrolysis in the presence of the trivalent cations and a rhodamine species in its ring opened form (i.e. N-(2-aminoethyl)-2-((6Z)-3-(ethylamino)-6-(ethylimino)-2,7-dimethyl-6H-xanthen-9-yl)benzamide, (L2)) along with cinnamaldehyde are produced. The rhodamine species in its ring opened form (L2) is responsible for the color change and strong increment in the absorbance and fluorescence of HL-CIN with Group 13 cations. Interaction between L1 and these metal ions could not produce the same outcome. It has been used in test paper strips and to detect these cations in real samples.

3-Aminopyridine Salicylidene: A Sensitive and Selective Chemosensor for the Detection of Cu(II), Al(III), and Fe(III) with Application to Real Samples

Interest in developing selective and sensitive metal sensors for environmental, biological, and industrial applications is mounting. The goal of this work was to develop a sensitive and selective sensor for certain metal ions in solution. The goal was achieved via (i) preparing the sensor ((E)-2-((pyridine-3-ylimino)methyl)phenol) (3APS) using microwave radiation in a short time and high yield and (ii) performing spectrophotometric titrations for 3APS with several metal ions. 3APS, a Schiff base, was prepared in 5 min and in a high yield (95%) using microwave-assisted synthesis. The compound was characterized by FTIR, XRD, NMR, and elemental analysis. Spectrophotometric titration of 3APS was performed with Al(III), Ba(II), Cd(II), Co(II), Cu(II), Fe(III), Mn(II), Ni(II), and Zn(II). 3APS showed good abilities to detect Al(III) and Fe(III) ions fluorescently and Cu(II) ion colorimetrically. The L/M stoichiometric ratio was 2:1 for Cu(II) and 1:1 for Al(III) and Fe(III). Low detection limits (μg/L) of 324, 20, and 45 were achieved for Cu(II), Al(III), and Fe(III), respectively. The detection of aluminum was also demonstrated in antiperspirant deodorants, test strips, and applications in secret writing. 3APS showed high fluorescent selectivity for Al(III) and Fe(III) and colorimetric selectivity towards Cu(II) with detection limits lower than corresponding safe drinking water guidelines.

Cyclometalated iridium(III) complex of a 1,2,3-triazole-based ligand for highly selective sensing of pyrophosphate ion

A new cyclometalated Ir(III) complex of a methylene-bridged benzimidazole-substituted 1,2,3-triazole methanol ligand has been synthesized for the photoluminescent detection of pyrophosphate (H₂P₂O₇^2-) anions. The solution structure of 1[PF6] was fully characterized by 1D (¹H, ¹³C) and 2D (¹H-¹H COSY, ¹H-¹³C HSQC, and ¹H-¹³C HMBC) NMR spectroscopy, and ESI-HRMS. The 1[PF6] acted as a highly selective luminescent sensor for H₂P₂O₇^2- in CH₃CN over other competitive ions, including H₂PO₄^-, ATP, ADP and AMP. The PL titration of 1[PF6] with H₂P₂O₇^2- in CH₃CN furnished the association constant K_a = 8.6 × 10⁷ M^-1 and a low detection limit of ∼127 nM. The structure of the analyte interacting ligand renders the Ir(III) complex-based probe highly selective for H₂P₂O₇^2- ions. The PL enhancement with H₂P₂O₇^2- is due to the hydrogen bonding interaction of H₂P₂O₇^2- with the triazole C-H, imidazole N-H, methylene hydrogen and hydroxyl groups of the ligand that has been supported by ¹H NMR titration. Further, the PL enhancement of 1·H₂P₂O₇^2- adducts was supported by triplet-state TDDFT calculations. In 1·H₂P₂O₇^2-, the ³MLCT-³MC energy gap is increased, and the 1·H₂P₂O₇^2- emits efficiently from the ³MLCT and ³ILCT excited states. Finally, a cytotoxicity study and live-cell imaging were performed. The probe showed low cytotoxicity against HeLa cells and was suitable for intracellular pyrophosphate imaging.

ESIPT-Active 8-Hydroxyquinoline-Based Fluorescence Sensor for Zn(II) Detection and Aggregation-Induced Emission of the Zn(II) Complex

A D-π-A type quinoline derivative, 2-(((4-(1, 2, 2-triphenylvinyl)phenyl)imino)methyl)quinolin-8-ol (HL), was synthesized and structurally characterized. The five-membered ring formed by the O-H···N hydrogen bond in HL contributed to the excited-state intramolecular proton transfer (ESIPT) behavior of HL, which was further verified by theoretical computations. Upon coordination with Zn²⁺, the hydroxyl proton in HL was removed, resulting in the inhibition of ESIPT. In the meanwhile, the formed Zn ₂ L ₄ complex displayed aggregation-induced emission (AIE) character in THF/H₂O mixtures, which is conducive to the fluorescence enhancement in aqueous media. Structure analysis suggested that the origin of the AIE characteristic was attributed to restriction of intramolecular rotations along with the formation of J-aggregates. Based on ESIPT coupled with AIE, HL could recognize Zn(II) in aqueous media via an orange fluorescence turn-on mode. Benefitting from the AIE property, chemosensor HL was successfully applied to fabricate test strips for rapid sensing of Zn(II) ions.

Chain length effect of spiro-ring N-alkylation on photophysical signalling parameters in Fe(III) selective rhodamine probes

Manifestation of photophysical signalling parameters in rhodamine derivatives exhibiting complexation induced spiro-ring opening is crucial for the realization of selective metal ion detection at trace levels. Substitution of various functional groups, such as alkylation to the core architecture, modulates the physico-chemical properties of such molecular probes. Despite a few studies, relationships between the extent of photophysical signal modulations and the chain lengths of n-alkyl substituents are still elusive. In this investigation, a few molecular probes based on the rhodamine B (1-5) and rhodamine 6G (6-10) platform were synthesized by their derivatization with n-alkyl substituents of varying chain lengths at the amino-donor of their spiro-ring end, which exhibited Fe(III)-selective absorption and fluorescence 'off-on' signal transduction along with colorization of solution. The Fe(III)-selectivity in these probes remained the same despite their structural distinctions through varied n-alkyl chain lengths of the substituents; however, the quantifiable signalling parameters such as spectroscopic enhancement factors, sensitivity, the kinetics of spiro-ring opening and effectiveness of probe-Fe(III) interactions were analyzed. These parameters were also correlated in terms of the influence of different chain lengths of n-alkyl substituents that efficiently contributed to their inter-componential interactive stereo-electronic environment.

A novel AIE-active imidazolium macrocyclic ratiometric fluorescence sensor for pyrophosphate anion

An imidazolium bridged macrocyclophane was synthesized as a ratiometric fluorescence sensor with aggregation-induced emission (AIE) characteristic to detect pyrophosphate anion with high selectivity among various anions. In the presence of zinc ion, macrocyclophane can form aggregates through complexation with pyrophosphate anion and emit ratiometric fluorescence, resulting from an enhancement in its aggregate-state emission and a reduction in its monomer emission. This AIE-active macrocycle showed great potential as a ratiometric fluorescence receptor.

A novel hydrazone-based fluorescent "off-on-off" probe for relay sensing of Ga3+ and PPi ions

A novel hydrazone-based fluorescent probe (E)-3-((2-(benzo[d]thiazol-2-yl)hydrazono)methyl)-4H-chromen-4-one (BTC) has been rationally designed and synthesized. BTC can subsequently detect Ga³⁺ and PPi ions through the absorption and emission off-on-off response with high specificity. Importantly, fluorescent probe BTC can well discriminate Ga³⁺ from Al³⁺ and In³⁺. The association constant (K) was calculated as 2.06 × 10⁴M^-1, and the limit of detection (LOD) was calculated as 4.88 × 10^-2μM. Competitive binding studies also illustrated good results of the probe BTC towards Ga³⁺. Job's plot and HRMS results substantiated the 1:1 stoichiometry between BTC and Ga³⁺ ion. The interaction binding mode of BTC with Ga³⁺ was proposed by HRMS, ¹H NMR spectral titration, UV-vis absorption and fluorescence spectral measurements. The combination of the restraint of the photo-induced electron transfer (PET) process and the chelation enhanced fluorescence (CHEF) process is responsible for the fluorescence enhancement of this probe. The in situ chelated BTC-Ga³⁺ could further monitor pyrophosphate ion (PPi) by demetallization process with quenching fluorescence emission. Additionally, the BTC and BTC-Ga³⁺ showed good cell permeability and could detect Ga³⁺ and PPi ions in onioninner epidermal cells, respectively.

Tracking the concentration of Al3+ in the aqueous system up to nanomolar range using modified biopolymer chitosan based fluorophore

The paper reports the development of biopolymer chitosan based fluorophore for selective detection of Al3+ in aqueous streams. Fluorescence sensing based on the change in the photophysical properties of the...

A highly selective A-π-A “turn-on” fluorescent probe for hypochlorite in tap water

A highly selective fluorescence probe (BON) for hypochlorite (ClO-) was designed and synthesized. The probe was based on boron-dipyrromethene (BODIPY) dye as the fluorophore and diaminomaleonitrile (DAMN) as the recognition...

A Facile Probe for Fluorescence Turn-on and Simultaneous Naked-Eyes Discrimination of H2S and biothiols (Cys and GSH) and Its Application

Hydrogen sulfide and biothiol molecules such as Cys and GSH acted important roles in many physiological processes. To simultaneously detect and distinguish them was quite necessary by a suitable fluorescent probe. A novel chemosensor 4-(4-(benzo[d]thiazol-2-yl)-2-methoxyphenoxy)-7-nitrobenzo[c][1,2,5]oxadiazole (BMNO) was designed to detect H₂S/Cys/GSH using the combination of nitrobenzofurazan (NBD) and benzothiazole fluorophores linked by a facile ether bond. The probe BMNO was developed for simultaneous identification of H₂S, Cys and GSH. Noticeably, the color changes (from colorless to light purple, light orange and light yellow) of probe BMNO solutions for sensing H₂S, Cys and GSH could be observed by naked eyes, respectively. The probe BMNO exhibited high selectivity and sensitivity for H₂S, Cys and GSH showing distinct optical signal with detection limit as low as 0.15 μM, 0.03 μM and 0.14 μM, respectively. The sensing mechanism was clarified by spectrum analysis and some controlled experiments. In addition, these outstanding properties of probe BMNO enabled its practical applications in detection H₂S in beer, and in cell imaging for Cys and GSH as well.

A bis-pyrene chalcone based fluorescent material for ratiometric sensing of hydrazine: An acid/base molecular switch and solid-state emitter

In this work, we have designed and synthesized a new fluorescent molecular probe, DPY comprising of pyrene-diacetylpyridine conjugate, which was found to be sensitive to hydrazine as well as protonation. DPY is characterised by a strong emission both in solution (λ_em = 530 nm) as well as in solid state (λ_em = 610 nm), attributed to intramolecular charge-transfer. The probe responds to hydrazine with a ratiometric fluorescence emission change from yellow to blue, due to chalcone cyclisation reaction of α, β-unsaturated carbonyl group resulting in the pyrazoline compound, DPY-Hy, imparting a strong greenish-blue emission in solution. Further, the strong fluorescence emission of DPY in powder and thin film was quenched upon exposure to TFA, and revived upon exposure to TEA. For developing on-site detection protocol, when DPY was drop-casted on nonfluorescent silica plate a vivid naked-eye colour change from orange-red to dark blue was realized. Interestingly, in the aggregated state, DPY exhibited a broad range emission from green to orange in a mixed solvent system of THF:H₂O. A plausible explanation of the photophysical events is substantiated with theoretical calculations.

A multi-binding site hydrazone-based chemosensor for Zn(ii) and Cd(ii): a new strategy for the detection of metal ions in aqueous media based on aggregation-induced emission

A multi-binding site chemosensor, N-(3-methoxy-2-hydroxybenzylidene)-3-hydroxy-2-naphthahydrazone (H₃L), with excited-state intramolecular proton transfer (ESIPT) behaviour was prepared and characterized. It possesses no aggregation-induced emission (AIE) characteristics but can detect Cd²⁺ and Zn²⁺ ions selectively in the "off-on" mode based on the AIE of their complexes in the media of THF/HEPES and THF/H₂O, respectively, which will provide a new strategy for target detection based on AIE. The detection limits of Zn²⁺ and Cd²⁺ were 9.85 × 10^-9 M and 1.27 × 10^-7 M, respectively. The aggregates of the complexes formed in the detection system were confirmed by DLS data and SEM images. The corresponding Zn²⁺ (1) and Cd²⁺ (2) complexes were prepared to investigate the response mechanism. Powder X-ray diffraction and single crystal X-ray diffraction proved that complex 1 is the species formed in the detection system. The chemosensor coordinates with the Cd²⁺ and Zn²⁺ ions in different formation and coordination modes, leading to the emission position of the aggregates at 560 and 645 nm, respectively, based on which Cd²⁺ ions were successfully differentiated from Zn²⁺ ions. Moreover, the detection of Cd²⁺ and Zn²⁺ ions was realized qualitatively via test paper and quantitatively in water.

Multifunctional rhodamine B appended ROMP derived fluorescent probe detects Al3+ and selectively labels lysosomes in live cells

There a few reports of rhodamine-based fluorescent sensors for selective detection of only Al3+, due to the challenge of identifying a suitable ligand for binding Al3+ ion. The use of fluorophore moieties appended to a polymer backbone for sensing applications is far from mature. Here, we report a new fluorescent probe/monomer 4 and its ROMP derived polymer P for specific detection of Al3+ ions. Both monomer 4 and its polymer P exhibit high selectivity toward only Al3+ with no interference from other metal ions, having a limit detection of 0.5 and 2.1 µM, respectively. The reversible recognition of monomer 4 and P for Al3+ was also proved in presence of Na2EDTA by both UV-Vis and fluorometric titration. The experimental data indicates the behavior of 4 and P toward Al3+ is pH independent in medium conditions. In addition, the switch-on luminescence response of 4 at acidic pH (0 < 5.0), allowed us to specifically stain lysosomes (pH ~ 4.5-5.0) in live cells.

Application of real sample analysis and biosensing: Synthesis of new naphthyl derived chemosensor for detection of Al3+ ions

A new chemosensor (NANH) based on naphthyl moiety was synthesized with good selectivity and sensitivity towards Al³⁺ ions via the inhibition by operating through dual mechanisms like photo-induced electron transfer (PET) and excited-state intramolecular proton transfer (ESIPT). The synthesized NANH was validated by various techniques such as ¹H, ¹³C NMR and mass spectrum. While prominent fluorescent enhancement was observed from the NANH upon binding with Al³⁺ ions, however, other metal ions have not responded in the emission spectrum. Detection limit and association constant of NANH for Al³⁺ were calculated as 1.2 × 10^-7 M and 4.09 × 10⁴ M^-1 by using fluorescence titration method. Binding ratio (1:1) of NANH with Al³⁺ ions were proved by Job's plot and DFT studies. Furthermore, aluminium in variety of water samples was determined, and NANH could be used for biosensing of Al³⁺ in living cells.

Study on synthesis and fluorescence property of rhodamine-naphthalene conjugate

In this study, a novel ligand (HL) consisting of 2-methyl quinoline-4-carboxylic acid, rhodamine and naphthalene moiety, was designed and synthesized, it could be developed a ratiometric fluorescent sensor for selective detection of Al³⁺ via fluorescence resonance energy transfer (FRET) from naphthalimide moiety to rhodamine moiety. The addition of Al³⁺ trigger the significant fluorescence enhancement of HL at 550 nm at the expense of the fluorescent emission of HL centered at 524 nm.

A novel switch on and reversible optical sensor as an efficient, selective receptor for Zn(II) ion and its biological application

In the present study, a promising optical sensor (TR) was designed, synthesized, characterized and its chemosensing mechanism has been explored through ¹H NMR, ESI-MS, UV-Vis absorption and emission spectral studies. This compound exhibits a drastic change in its optical properties when treated with Zn²⁺, whereas other metal ions do not respond. This provides a naked eye detection for Zn²⁺ ion. In methanolic medium, Zn²⁺ ion induces strong fluorescence in TR with large Stokes shifts up to ∼132 nm. A 5-fold increase in fluorescence intensity of TR in presence Zn²⁺ ion is due to inhibition of ESIPT (Excited State Intramolecular Proton Transfer) and -C=N isomerization with large increase in the ICT (Intramolecular Charge Transfer) character of TR in the excited state. The Job's plot and BH plots reveal the formation of 1: 1 stoichiometry with an estimated binding constant of 3.9 × 10⁷ M^-1. The detection limit of TR was found to be 3.85 nM. The TR could be regenerated by adding EDTA solution to the complex formed during interaction. The pH studies indicate that TR could render pH dependent fluorescence measurements in a live physiological environment. Computational technique was used to optimize the structures and the theoretical results are correlated with the experimental results. The possible utilization of TR as bio-imaging fluorescent sensor with 98.57% cell viability to detect Zn²⁺ in HeLa cells was also explored by fluorescent cell imager.

Effect of n-alkyl substitution on Cu(ii)-selective chemosensing of rhodamine B derivatives

Rhodamine B hydrazide-based molecular probes (1-10) were synthesized by derivatization with n-alkyl chains of different lengths at the hydrazide amino end. These probes exhibited selective absorption (A∼557) and fluorescence (I∼580) 'off-on' signal transduction along with a colourless → magenta colour transition in the presence of Cu(ii) ions among all the competitive metal ions investigated. The effective coordination of these probes to Cu(ii) ions under the investigated environment forming [Cu·L]2+ (L = 1-5) and [Cu·L2]2+ (L = 6-10) complexes led to their spiro-ring opening, which in turn was expressed through signatory spectral peaks of ring-opened rhodamine. All these probes exhibited Cu(ii) selectivity in signalling despite structural modifications to the core receptor unit through variation of the nature of the alkyl substituents. However, the sensitivity of the signalling and kinetics of the spiro-ring opening varied and could be correlated with the number of carbon atoms present in the n-alkyl substituents. Structural elucidation with X-ray diffraction and X-ray photoemission spectroscopic analyses provided further insight into the structure-function correlation in their Cu(ii) complexes. These probes with Cu(ii) coordination showed selectivity in signalling, high complexation affinity (log Ka = 4.8-8.8), high sensitivity (LOD = 4.1-80 nM), fast response time (rate = 0.0017-0.0159 s-1) and reversibility with counter anions, which ascertained their potential utility as chemosensors for Cu(ii) ion detection.

An efficient water-soluble fluorescent chemosensor based on furan Schiff base functionalized PEG for the sensitive detection of Al3+ in pure aqueous solution

An efficient reversible fluorescent chemosensor, PEGFB, based on polyethylene glycol bearing a furan Schiff base unit has been successfully developed to sensitively detect Al³⁺ in pure aqueous solution.

Theoretical Design of Near-Infrared Al3+ Fluorescent Probes Based on Salicylaldehyde Acylhydrazone Schiff Base Derivatives

The aim of this paper is to design near-infrared (NIR) Al³⁺ fluorescent probes based on a Schiff base to extend their applications in biological systems. By combining benzo[h]quinoline unit and salicylaldehyde acylhydrazone, we designed two new Schiff base derivatives. According to theoretical simulations on previous experimental Al³⁺ probes, we obtained the appropriate theoretical approaches to describe the properties of these fluorescent probes. By employing such approaches on our newly designed molecules, it is found that the new molecules have high selectivity toward Al³⁺ and that their corresponding Al³⁺ complexes can emit NIR fluorescence. As a result, they are expected to be potential NIR Al³⁺ fluorescent probes.

A dual functional turn-on non-toxic chemosensor for highly selective and sensitive visual detection of Mg2+ and Zn2+: the solvent-controlled recognition effect and bio-imaging application

A new dual functional turn-on chemosensor, 2,6-diformyl-4-methylphenol-di(isoquinolinyl-1-hydrazone) (HL), has been developed, which could highly selectively discriminate Mg²⁺ and Zn²⁺ in different solvent systems. The chemosensor HL exhibits rapid visual turn-on fluorescence enhancing recognition toward Mg²⁺/Zn²⁺, which is not interfered by other cations, especially for respective congeners Ca²⁺/Cd²⁺. The remarkable fluorescence enhancement (71-fold or 11-fold) was observed after adding Mg²⁺ in acetonitrile or Zn²⁺ in DMF-H₂O solvent systems. Additionally such a solvent medium-controlled platform could achieve the quantitative determination of Mg²⁺ and Zn²⁺ quantitation with low detection limits of 2.97 × 10^-8 M and 3.07 × 10^-7 M, respectively. Furthermore, the turn-on fluorescence sensing mechanism is also investigated by ¹H NMR, FT-IR and ESI-MS spectroscopy. Density functional theory (DFT) calculations derive optimized geometries of HL and its complexes. Notably, non-toxic HL also can be successfully applied as a visual probe for the practical determination of Mg²⁺/Zn²⁺ in MCF-7 cells, Zebrafish larvae, syrup and water samples, which might provide extensive application in biology and medicine fields.

A coumarin based fluorescent probe for rapidly distinguishing of hypochlorite and copper (II) ion in organisms

A dual-functional fluorescent probe based on coumarin fluorophore for monitoring ClO^- and Cu²⁺ was synthesized and characterized. The identification mechanisms for ClO^- and Cu²⁺ induced different colorimetric and ratiometric changes. ClO^- caused a colorimetric change from yellow to colorless and 120 nm blue-shifted emission spectra from red to blue. Besides, Cu²⁺ induced a remarkable fluorescence quenching behavior and 36 nm blue-shifted absorption spectra accompanied by the color change from yellow to luminous yellow. As expected, Probe 1 displayed excellent selectivity and sensitivity for detecting ClO^- and Cu²⁺ over other competing ions in their respective systems. The limits of detection for ClO^- and Cu²⁺ were 24.62 nM and 0.39 nM, respectively. The recognition mechanisms were proved by ¹H NMR, mass spectrum and theoretical calculations. More importantly, the reversibility of Cu²⁺ could be applicable to rapid quantification for ClO^-/Cu²⁺. Thus, the strategy for sensing ClO^-/Cu²⁺ was carried out, which revealed broad applications of Probe 1 in multiple actual water and biology.

An efficient new dual fluorescent pyrene based chemosensor for the detection of bismuth (III) and aluminium (III) ions and its applications in bio-imaging

A new simple pyrene based schiff base chemosensor 1 (nicotinic acid pyren-1-ylmethylene-hydrazide) has been constructed and is prepared from 1-pyrenecarboxaldehyde and nicotinic hydrazide. Notably, the chemosensor 1 exhibited remarkable colour changes while in the presence of trivalent metal ions like Bi³⁺ & Al³⁺ ion in DMSO-H₂O, (1:1 v/v, HEPES = 50 mM, pH = 7.4). The UV-Vis spectral investigation of chemosensor 1 showed that the maximum absorption peak appeared at 378 nm. In emission studies, chemosensor 1 develops weak fluorescence, while upon the addition of Bi³⁺ and Al³⁺ ions, it exhibits an enhancement of fluorescence intensity. Nevertheless, rest of metal ions have no changes in the emission spectra. The association constant of chemosensor 1 for binding to Bi³⁺ & Al³⁺ system had a value of 1.27 × 10⁴ M^-1 and 1.53 × 10⁴ M^-1. The detection limits were 0.12 µM for Bi³⁺ and 0.17 µM for Al³⁺ respectively. The overall results reveal that chemosensor 1 can act as a dual-channel, highly selective, and sensitive probe for Bi³⁺ and Al³⁺ ions. Moreover, the fluorescence imaging of chemosensor 1 was applied in RAW 264.7 cell line and cytotoxicity assay prove that this chemosensor 1 is non-toxic as well as highly biocompatible.

A fluorescein-based chemosensor for “turn-on” detection of Hg2+ and the resultant complex as a fluorescent sensor for S2− in semi-aqueous medium with cell-imaging application: experimental and computational studies

A fluorescein hydrazone based probe selectively recognizes Hg²⁺ ion with live cell imaging application.

Development of rhodamine-based fluorescent probes for sensitive detection of Fe3+ in water: spectroscopic and computational investigations

Four novel rhodamine-based fluorescent probes (RE1–RE4) were designed and synthesized for sensitive detection of Fe³⁺ in water.

Rhodamine scaffolds as real time chemosensors for selective detection of bisulfite in aqueous medium

Rhodamine and its derivatives have been widely used in designing fluorescent ‘turn on’ cation sensors, while very few rhodamine based fluorescent probes have been reported to date for the detection of anions in water.