A squaraine-based near IR fluorescent chemosensor for Calcium

A red to NIR emitting, highly Ca²⁺-specific fluorescent chemosensor has been synthesized. In pH 7.2 aqueous buffers, the chemosensor signals Ca²⁺ by a decrease in emission intensity, whereas large excess of Mg²⁺ ions have no effect on either the absorption or the emission spectrum. The chemosensor is likely to be the prototype of a new generation of laser-diode excitable fluorescent chemosensors for Calcium.     

A fluorescein derivative for nanomolar aqueous copper and monitoring copper ion uptake by transferrin and amyloid precursor protein

A new fluorescent chemosensor based on the fluorescein derivative effectively recognizes Cu²⁺ in nanomolar range at pH 7.4. The Cu²⁺ ion uptake by transferrin and amyloid precursor protein was monitored using the title fluorescent chemosensor.     

Colorimetric and fluorescent chemosensor for citrate based on a rhodamine and Pb complex in aqueous solution

In this paper we unveil a novel rhodamine compound based fluorescent chemosensor (1-Pb²⁺) for colormetric and fluorescent detection of citrate in aqueous solution. This is the first fluorescent chemosensor for citrate based on rhodamine compound. The comparison of this method with some other fluorescence methods for citrate indicates that the method can detect citrate in aqueous solution by both color changes and fluorescent changes with long emission wavelength. In the new developed sensing system, 1-Pb²⁺ is fluorescent due to Pb²⁺-induced fluorescence enhancement of 1. However, the addition of citrate may release 1 into the solution with quenching of fluorescence. The chemosensor can be applied to the quantification of citrate with a linear range covering from 1.0 × 10⁻⁷ to 5.0 × 10⁻⁵ M and a detection limit of 2.5 × 10⁻⁸ M. The experiment results show that the response behavior of 1-Pb²⁺ towards citrate is pH independent in medium condition (pH 6.0–8.0). Most importantly, the fluorescence changes of the chemosensor are remarkably specific for citrate in the presence of other anions (even those that exist in high concentration), which meet the selective requirements for practical application. Moreover, the response of the chemosensor toward citrate is fast (response time less than 1 min). In addition, the chemosensor has been used for determination of citrate in urine samples with satisfactory results.     

A ‘turn-on’ fluorescent chemosensor based on rhodamine-N-(3-aminopropyl)-imidazole for detection of Al ions

A novel N-(3-aminopropyl)-imidazole-appended rhodamine-based fluorescent chemosensor was synthesized. The sensing behavior and selectivity of the synthesized chemosensor toward metal cations were studied by UV/vis and fluorescence spectroscopy. The chemosensor recognized Al³⁺ ions by a significantly enhanced fluorescence and a visible color change due to opening of the spirolactam ring triggered by the addition of Al³⁺ ions.     

A colormetric and fluorescent chemosensor for adenosine-5′-triphosphate based on rhodamine derivative

A rhodamine spirolactam derivative (1) was developed as a colormetric and fluorescent chemosensor for adenosine-5′-triphosphate (ATP) via hydrogen bonds interaction. As far as we know, this is the first case to explore ATP-induced ring-opening of spirolactam in rhodamine derivatives. It exhibited a highly sensitive “turn-on” fluorescent response toward ATP with a 47-fold fluorescence intensity enhancement under 20 equiv. of ATP added. The chemosensor can be applied to the quantification of ATP with a linear range covering from 1.0 × 10⁻⁷ to 2.0 × 10⁻⁴ M and a detection limit of 2.5 × 10⁻⁸ M. The experiment results show that the response behavior of 1 toward ATP is pH independent in medium condition (pH 6.0–8.0). Most importantly, the novel chemosensor has well solved the problem of serious interferences from other nucleoside polyphosphates such as ADP and AMP generally met by previously reported typical fluorescent chemosensors for ATP. Moreover, the response of the chemosensor toward ATP is fast (response time less than 3 min). In addition, the chemosensor can be used for the fluorescence assay for protein kinase activity with satisfactory results. The chemosensor for ATP based on hydrogen bonds interaction provided a novel strategy for the design of colormetric and ratiometric fluorescent probes for other target anions with high sensitivity and selectivity.     

Highly selective fluorescent calix[4]arene chemosensor for acidic amino acids in pure aqueous media

A fluorescent chemosensor based on a calix[4]arene derivative conjugated with four thiophene-cyanoarylic acid groups at the upper rim displays high selectivity toward acidic amino acids in pure aqueous media through multiple H-bond interactions. The interactions of Asp/Glu with the chemosensor have been investigated by fluorescence and UV–Vis titrations, ESI-MS assay, ¹H NMR spectra, and molecular modeling method.     

A New Fluorescent Chemosensor for Cu2+ Based on a Dianthracene-Derivative

Abstract

Besides being of interest in photochemistry, photoinduced electron transfer (PET) is a process largely used in the design of fluorescent ion sensing molecules. One of the simplest systems is based on fluorescent aromatic groups linked to amino groups and proposed as possible fluorescent transition metal ion chemosensor [1]. In this case, the fluorescence of the fluorophore “ligths on” when the amino group is complexed. On the other hand, in the absence of metal ions, the fluorescence is quenched by a PET originating from the nitrogen lone electron pairs [2]. We prepared a new fluorescent chemosensor, abbreviated as Ant-NH-O-O-NH-Ant (shown in Fig. 1) in which the intramolecular PET is expected to be efficient. The chemosensor consists of a metal-binding dioxodiamino unit linked to two light-emitting anthracene fragments. This type of supramolecules when irradiated in methanol solution (conc. 1.89—10^?5 M.) at 368 nm displays a characteristic fluorescence spectrum for anthracene group with the most intensive band at 415 nm [Fig. 2(a)]. The emission is slightly enhanced upon coordination of such metal ions as Ni²⁺ and Zn²⁺ by the ligand fragment of the Ant-NH-O-O-NH-Ant molecule [Fig. 2(b) and (d)]. However, much higher intensity of emission is observed in the case of Cu²⁺ complex [see Fig 2(c)]. The fluorescence enhancement is presumably due to suppression of photoinduced fluorophore-to-metal electron-transfer mechanism.     

‘On-Off’ reversible switch for Fe and F mimicking XNOR logic function

A new pyrene-appended chemosensor based on thiacalix[4]arene of 1,3-alternate conformation has been synthesised which demonstrates selective optical recognition of Fe³⁺ and F⁻ in two contrasting modes. The chemosensor behaves as a bifunctional fluorescent switch which mimics the performance of an exclusive-NOR (XNOR) logic gate with chemical inputs of Fe³⁺ and F⁻ ions.     

A novel and synthetically facile coumarin-thiophene-derived Schiff base for selective fluorescent detection of cyanide anions in aqueous solution: Synthesis,anion interactions,theoretical study and DNA-binding properties

A colorimetric and fluorescent chemosensor (chemosensor 2) for the detection of cyanide anions in aqueous solution has been designed and synthesized in high yield. The sensing mechanism of the chemosensor was verified via UV–vis, fluorimetric, and NMR titrations, and was theoretically explained using DFT and TD-DFT calculations. The chemosensor could optically discriminate the presence of fluoride ions over other anions by a color change from yellow to red with an enhancement of pink fluorescence in DMSO. However, it showed strong green fluorescence when CN^? was added to a mixture of DMSO/water (6:4 v/v). Thus, the chemosensor can be employed in selective detecting of CN^? besides other interference anions (F^?, AcO^? and H₂PO₄^?) in aqueous solution. Moreover, 2 can be used to detect CN^? at a concentration as low as 0.32?μM, which is lower than the WHO guideline (2.7?μM) for cyanide. A low quantity of CN^? (1.08?μM) can be detected and quantified using the prepared chemosensor. Moreover, the UV–vis and fluorescence spectroscopy studies of the interactions between 2 and dublex DNA revealed intercalative binding of calf thymus DNA to the chemosensor.     

A tetraphenylethene based polarity dependent turn-on fluorescence strategy for selective and sensitive detection of Hg in aqueous medium and in living cells

A turn-on fluorescent chemosensor strategy based on the change in the polarity of aggregation induced emission active tetraphenylethene is presented for the detection of Hg²⁺ in aqueous medium and in living cells. The sensing mechanism involves the formation of nonpolar fluorescent aggregates of tetraphenylethene molecules by elimination of polar moieties of TPE with Hg²⁺ interaction.     

Benzimidazole-based imine-linked chemosensor: chromogenic sensor for Mg2+ and fluorescent sensor for Cr3+

We synthesized an imine-linked, benzimidazole-based chemosensor that can be used for chromogenic recognition of Mg²⁺ and fluorescent recognition of Cr³⁺. The chemosensor shows sensitive, selective, and ratiometric recognition of Cr³⁺ through concurrent quenching at one wavelength and enhancement of fluorescence intensity at another wavelength. It can also be used to detect Mg²⁺ via UV–vis absorption spectroscopy. DFT calculations support these phenomena. The sensor can be used to strain microbe cells without breakage.     

Action of a Fluorescent Chemosensor for Cu2+ Encapsulated in Silica Xerogel

The fluorescent chemosensor of the type Ant-NH-O-O-NH-Ant for Cu²⁺ ions has been designed by means of a supramolecular approach, as follows: two anthracene (Ant) fragments as fluorophore subunits have been linked by a noncyclic NH-O-O-NH quadridentate ligand as a receptor. The interaction of Cu²⁺ - receptor is signalled through the enhancement of the anthracene fluorescence when the receptor, i.e., the dioxodiamine chain subunit of the sensor is able to stop a photoinduced electron-transfer mechanism. The experiments with the chemosensor encapsulated in silica xerogel by the sol-gel processing are described.     

A quinoline-based selective ‘turn on’ chemosensor for zinc(II) via quad-core complex,and its application in live cell imaging

An efficient quinoline-based fluorescent chemosensor (QLNPY) was successfully developed for the detection of zinc ions (Zn²⁺). This novel chemosensor displayed higher sensitivity and selectivity toward Zn²⁺ over other competitive metal ions accompanying with obvious fluorescence enhancement. The QLNPY-Zn²⁺ complex can be further used as a new fluorescent “turn-off” sensor for pyrophosphate (PPi) and sulfur ion (S^2?) via a Zn²⁺ displacement approach. The limits of detection were calculated to be 3.8 × 10^?8 M for Zn²⁺, 3.7 × 10^?7 M for PPi and 4.9 × 10^?7 M for S^2?. The binding mechanism of QLNPY and Zn²⁺ was investigated through NMR, HR-MS analysis and further studied by crystallographic analysis. Additionally, further application of QLNPY for sequential bioimaging of Zn²⁺ and PPi was studied in HepG2 cells, suggesting that the quinoline-based chemosensor possesses great potential applications for the detection of intracellular Zn²⁺ and PPi in vivo.     

A biacylhydrazone-based chemosensor for fluorescence ‘turn-on’ detection of Al3+ with high selectivity and sensitivity

A simple Al³⁺ fluorescent chemosensor (1) based on diacylhydrazone has been designed and synthesized by the condensation reaction of 2-hydroxy naphthaldehyde and metaphthalic hydrazide. The chemosensor 1 displays a specific and sensitive response to Al³⁺ over other cations in DMSO solution. Upon the addition of DMSO solution of Al³⁺, the sensor 1 shows an immediate fluorescence ‘turn-on’ response and emitting strong blue emission with visible color change from colorless to green. The fluorescence quantum yield enhanced from 7.24% to 48.68%. Meanwhile, the fluorescence and UV absorption spectra detection limits of the chemosensor 1 for Al³⁺ were 2.0 × 10^?7 M and 5.6 × 10^?7 M respectively, indicating the high sensitivity of 1 to Al³⁺. Furthermore, test strips based on 1 were fabricated, which could be used as a convenient test kit for the detection of Al³⁺ and an efficient Al³⁺ controlled fluorescent security display materials.     

Fluorescence turn-on chemosensor for Hg<Superscript>2+</Superscript> based on a rhodamine derivative and its application in bioimaging

A fluorescence turn-on chemosensor based on rhodamine B derivative (FD10) has been developed as a highly sensitive chemosensor for Hg²⁺. A prominent fluorescence enhancement was measured in the presence of Hg²⁺, which was in agreement with the changes in the absorption spectrum. Furthermore, by means of laser scanning fluorescence microscopy experiments, it was demonstrated that FD10 was cell-permeable and could be used as a fluorescent probe for monitoring Hg²⁺ in living cells. Supported by the National Natural Science Foundation of China (Grant No. 20801015) and Shanghai Leading Academic Discipline Project (Grant No. B108)     

Highly Effective Fluorescent Sensor for Hg2+ in Aqueous Solution

A new anthracene fluorophore senses Hg²⁺ selectively in aqueous solution. Among the metal ions examined, fluorescent chemosensor 1 shows selective large CHEQ effects with Hg²⁺ and Ag⁺ at pH 7.     

A tetra-sulfonamide derivative bearing two dansyl groups designed as a new fluoride selective fluorescent chemosensor

A new fluorescent chemosensor based on an acyclic tetra-sulfonamide derivative linked to two dansyl groups has been conveniently synthesized. Its high selective binding ability to fluoride ions over other halide ions was demonstrated by using fluorescence as well as ¹H NMR spectra.     

A new fluorescent chemosensor for transition metal cations and on/off molecular switch controlled by pH

A new fluorescent chemosensor with imidazole as ionophore was synthesized by the selective derivation of calixarene, which can effectively recognize Cu²⁺ and Zn²⁺ leading to different fluoroscopic behaviors in CH₃OH-H₂O. This system could be considered as a molecular switch. By modulating the pH of the solution, on-off-on fluorescent switching is carried out upon combinatory addition of acid, base and Cu²⁺.     

Imidazo[1,2-a]pyridine-substituted coumarin as a selective ratiometric sensor for Cu2+ ion

A novel fluorescent chemosensor, (E)-7-(diethylamino)-3-((2-phenylimidazo[1,2-a]pyridin-3-ylimino)methyl)-2H-chromen-2-one 1a, has been synthesised and characterised. This chemosensor displayed an extreme selective fluorescence emission only with Cu²⁺ ion over all other metal ions examined. The Job’s plot experiment analysis suggested the binding ratio of the chemosensor 1a with Cu²⁺ was 1:1 metal-to-ligand ratio. The association constant for Cu²⁺ towards receptor 1a obtained from Benesi–Hildebrand plot was found to be 4.859 × 10³ M^?1 with a detection limit 4.6 × 10^?8 M. Fluorescence enhancement caused by Cu²⁺ binding with chemosensor 1a attributed to combinational effect of intramolecular charge transfer and chelation-enhanced fluorescence occurred at pH 8.0.     

Unmodified fluorescein as a fluorescent chemosensor for fluoride ion detection

Unmodified fluorescein (1) behaves as a fluorescent chemosensor for F⁻ detection, where the F⁻-induced fluorescence enhancement is driven by a transfer of the phenolic OH protons to F⁻.