Rhodamine-based highly sensitive colorimetric off-on fluorescent chemosensor for Hg2+ in aqueous solution and for live cell imaging

A novel rhodamine-based highly sensitive and selective colorimetric off-on fluorescent chemosensor for Hg(2+) ions is designed and prepared by using the well-known thiospirolactam rhodamine chromophore and furfural hydrazone as signal-reporting groups. The photophysical characterization and Hg(2+)-binding properties of sensor RS1 in neutral N, N-dimethylformamide (DMF) aqueous solution are also investigated. The signal change of the chemosensor is based on a specific metal ion induced reversible ring-opening mechanism of the rhodamine spirolactam. The response of the chemosensor for Hg(2+) ions is instantaneous and reversible. And it successfully exhibits a remarkably "turn on" response toward Hg(2+) over other metal ions (even those that exist in high concentration). Moreover, this sensor is applied for in vivo imaging in Rat Schwann cells to confirm that RS1 can be used as a fluorescent probe for monitoring Hg(2+) in living cells with satisfying results, which further demonstrates its value of practical applications in environmental and biological systems.     

Facile synthesis of rhodamine-based highly sensitive and fast responsive colorimetric and off-on fluorescent reversible chemosensors for Hg2+: preparation of a fluorescent thin film sensor

Fluorescence-active chemosensors (L1-L4), comprising a rhodamine scaffold and a pseudo azacrown cation-binding subunit, have been proposed and characterized as a fluorescent chemosensor for Hg(2+). An on-off type fluorescent enhancement was observed by the formation of the ring-opened amide form of the rhodamine moiety, which was induced by the interactions between Hg(2+) and the chemosensor. Upon the addition of Hg(2+), an overall emission change of 350-fold was observed, and the selectivity was calculated to be 300 times higher than Cu(2+) for receptors L2-L4. A polymeric thin film can be obtained by doping poly(methyl methacrylate) or PMMA with chemosensor L2. Such a thin film sensor can be used to detect Hg(2+) with high sensitivity and can be recovered using diluted NaOH.     

Highly sensitive multiresponsive chemosensor for selective detection of Hg2+ in natural water and different monitoring environments

A new chemosensor RF1 that combines a ferrocene unit and a rhodamine block via the linkage of a carbohydrazone binding unit was designed and prepared for the highly selective detection of Hg (2+) in natural water. This chemosensor displays great brightness and fluorescence enhancement following Hg (2+) coordination within the limit of detection for Hg (2+) at 1 parts per billion (ppb). The fluorescence intensities are nearly proportional to the amount of Hg (2+) at the ppb level. It is capable of distinguishing between the safe and the toxic levels of inorganic mercury in drinking water. Hg (2+)-binding also arouses the absorption of the rhodamine moiety in RF1 significantly with the chromogenic detection limit for Hg (2+) at 50 ppb. The conventional UV-vis spectroscopic method thus has the potential to provide the critical information about the mercury hazard assessment for industrial wastewater discharging. The obvious and characteristic color change of the titration solution from colorless to pink upon the addition of Hg (2+) demonstrates that RF1 can be used for "naked-eye" detection of Hg (2+) in water. The Hg (2+) complexation also causes a significant shift of the redox potential about the ferrocene/ferrocenium couple. The electrochemical responses provide the possibility to quantitative analysis of Hg (2+) at the parts per million (ppm) level. Preliminary investigations in natural water samples including seawater and freshwater indicate that RF1 offers a direct and immediate Hg (2+) detection in complex media, pointing out its potential utility in environment monitoring and assessment. The responses of RF1 are Hg (2+) specific, and the chemosensor exhibits high selectivity toward Hg (2+) over other Group 12 metals, alkali, alkaline earth metals, and most of the divalent first-row transition metals. The RF1-Hg (2+) complex is successfully isolated and the Hg (2+)-binding is reversible. The crystal structure and spectral properties of its congener RF2 that contains one ferrocene group and two rhodamine 6G moieties were also investigated for a comparison.     

Rhodamine thiospirolactone. Highly selective and sensitive reversible sensing of Hg(II)

A novel rhodamine thiospirolactone chemosensor was found to develop prominent absorbance and fluorescence enhancements in the presence of Hg(2+) in aqueous solution and this was suggested to result from the thiospiro ring opening induced by Hg(2+) binding.     

Naphthalimide appended rhodamine derivative: through bond energy transfer for sensing of Hg2+ ions

A naphthalimide appended rhodamine based fluorescent chemosensor '1' is synthesized which undergoes through bond energy transfer in the presence of Hg(2+) ions in mixed aqueous media.     

A squaraine-based colorimetric and "turn on" fluorescent sensor for selective detection of Hg2+ in an aqueous medium

A novel squaraine-based chemosensor SQ-1 has been synthesized, and its sensing behavior toward various metal ions was investigated by UV-vis and fluorescence spectroscopies. In AcOH-H(2)O (40:60, v/v) solution, Hg(2+) ions coordinate with SQ-1 causing a deaggregation which induces a visual color and absorption spectral changes as well as strong fluorescence. In contrast, the addition of other metals (e.g., Pb(2+), Cd(2+), Cu(2+), Zn(2+), Al(3+), Ni(2+), Co(2+), Fe(3+), Ca(2+), K(+), Mg(2+), Na(+), and Ag(+)) does not induce these changes at all. Thus SQ-1 is a specific Hg(2+) sensing agent due to the inducing deaggregation of the dye molecule by Hg(2+).     

A turn-on chemosensor for Hg2+ in aqueous media and its application in "MCT" imaging in living cells

A turn-on chemosensor L1, which exhibits high selectivity and sensitivity toward Hg(2+) over other common metal ions in aqueous media under a physiological pH window via a 1:1 binding mode, had been synthesized and characterized. L1 provides good fluorescent imaging of Hg(2+) in living cells. Particularly, we adopted the "micro computed tomography (MCT)" technology, successfully demonstrating the method of Hg(2+) sensing by L1 in cell lines, also the cell permeability of L1 and its imaging position in the cells.     

A Selective and Sensitive "Turn-on" Fluorescent Chemosensor for Recognition of Hg(2+) Ions in Water

Based upon highly selective and irreversible Hg(2+) -promoted deprotection of the dithioacetal reaction, a new water-soluble "turn-on" fluorescent chemosensor (1) was prepared and exhibited high selectivity and sensitivity towards the Hg(2+) ion over other heavy and transition-metal ions in pure water by transforming a weakly fluorescent precursor (colorless) to a highly fluorescent aldehyde (yellow-green; see figure) with a 155-fold increase in fluorescent intensity.     

A novel colorimetric and fluorescent chemosensor for acetate ions in aqueous media based on a rhodamine 6G-phenylurea conjugate in the presence of Fe(III) ions

A novel colorimetric and fluorescent chemosensor based on a rhodamine 6G phenylurea conjugate showed highly selective and sensitive recognition toward acetate ions in H(2)O-CH(3)CN (1:1, v/v) with fluorescence intensity change and also clear color change from pink to colorless in the presence of Fe(III) ions.     

Novel fluorescent chemosensor for Ag^ ＋ based on coumarin fluorophore

A novel chemosensor 1 （CS1） bearing one coumarin and two carbodithioate groups was synthesized and its fluorescent sensing behavior toward metal ions was investigated. Ag^＋ addition to a CH3COCH3/H2O （3：7, v：v） solution of CS1 gave a significantly quenched fluorescence. Other ions including Pb^2＋, Zn^2＋, Cu^2＋, Ca^2＋, Cd^2＋, Co^2＋, Mg^2＋, Mn^2＋, Hg^2＋, Ag^＋, Ni^2＋ induced no or much smaller spectral changes. This constitutes an ON-OFF Ag^＋-selective fluorescent chemosensor.     

A "turn-on" fluorescent Hg2+ chemosensor based on Ferrier carbocyclization

A "turn-on" fluorescent chemosensor with excellent selectivity and satisfactory sensitivity on Hg(2+) detection in 100% water media has been established employing a carbohydrate based Ferrier carbocyclization reaction. The probe has also presented satisfactory results for the imaging of Hg(2+) ions in cells and organisms.     

Rhodamine triazole-based fluorescent probe for the detection of Pt(2+)

A rhodamine triazole-based fluorescent chemosensor has been developed for the selective detection of platinum ions in aqueous solutions. The rhodamine 6G hydroxamate linked with a propargyl group is converted to the corresponding triazole by a "click" reaction. The dual binding unit composed of a hydroxamate and a triazole shows high selectivity and sensitivity toward Pt(2+) over a range of other metal ions in water. The fluorescent probe is applied to monitor cisplatin in aqueous solutions.     

Novel hemicyanine dye as colorimetric and fluorometric dual-modal chemosensor for mercury in water

A novel water soluble Hg(2+)-selective chemosensor 1 with hemicyanine as fluorescent reporting group and NO(2)Se(2) chelating unit as ion binding site was reported. Chemosensor 1 shows a specific Hg(2+) selectivity and discrimination between Hg(2+) and chemically similar ions in conjunction with a visible colorimetric change from red to colorless, potentially leading to both "naked-eye" and fluorometric detection of Hg(2+) cations.     

Ratiometric sensing of Hg2+ based on the calix[4]arene of partial cone conformation possessing a dansyl moiety

A new fluorescent chemosensor based on the calix[4]arene of partial cone conformation possessing a dansyl moiety has been synthesized. The chemosensor demonstrates selective optical recognition of Hg(2+) and Cu(2+) in two contrasting modes. The receptor exhibited ratiometric sensing of Hg(2+) and "ON-OFF" type of fluorescence behavior in the presence of Cu(2+). The compound behaves as a fluorescent molecular switch upon chemical inputs of Hg(2+) and Cu(2+) ions.     

A new "turn-on" naphthalenedimide-based chemosensor for mercury ions with high selectivity: successful utilization of the mechanism of twisted intramolecular charge transfer, near-IR fluorescence, and cell images

For the first time, a new near-IR "turn-on" fluorescent chemosensor with high selectivity for Hg(2+) ions was designed according to the twisted intramolecular charge transfer (TICT) mechanism. The selective fluorescence enhancement effect can be optimized by modulating the solvent systems. And this naphthalenedimide-based sensor with long wavelength absorption and emission can be used to image intracellular Hg(2+) ions in living Hela cells.     

Switching the recognition preference of rhodamine B spirolactam by replacing one atom: design of rhodamine B thiohydrazide for recognition of Hg(II) in aqueous solution

[STRUCTURE: SEE TEXT] A new chemosensor based on rhodamine B thiohydrazide is described. Chemosensor B was found to show a reversible dual chromo- and fluorogenic response toward Hg2+ in aqueous solution in a highly selective and sensitive manner. This was suggested to result from the coordination of Hg2+ at the N, S binding sites in B to open its spiro ring.     

Fluorescence turn-on chemosensor for Hg~(2+) 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.     

An efficient rhodamine thiospirolactam-based fluorescent probe for detection of Hg2+ in aqueous samples

This paper described the optimized design, synthesis and application of a novel rhodamine thiospirolactam derivative as an 'off-on' fluorescent probe for the detection of Hg(2+) in aqueous samples. The 'off-on' fluorescence and color signal change of the probe is based on an Hg(2+)-triggered domino reaction which brings on the opened-ring form of the rhodamine spirolactam to regain the conjugated system of the rhodamine skeleton. In the well designed probe, the thiospirolactam serves as both Hg(2+) binding unit and electron-defect carbon centre, a phenolic hydroxyl with very strong nucleophilicity after deprotonation is chosen as the attacking unit, and a benzene ring is introduced on the linker to afford steric effects, which benefits an efficient nucleophilic reaction, with a high sensitivity towards Hg(2+). It exhibits a stable response for Hg(2+) from 1.0 × 10(-8) to 1.0 × 10(-6) M, with a detection limit of 3.0 × 10(-9) M. The response of the probe to Hg(2+) is highly selective and pH-insensitive, with a fast response time. All these unique features make it particularly favorable for cellular Hg(2+) imaging applications. It has been preliminarily used for highly sensitive monitoring of Hg(2+) levels in living cells with satisfying resolution.     

Highly sensitive and selective chemosensor for Hg2+ based on the rhodamine fluorophore

A novel tren-based tripodal chemosensor 1 bearing a rhodamine and two tosyl groups was synthesized and its sensing behavior toward metal ions was investigated by UV/vis and fluorescence spectroscopies. Addition of a Hg2+ ion to a CH3CN solution of 1 gave a visual color change as well as significantly enhanced fluorescence, while other ions including Pb2+, Zn2+, Cu2+, Ca2+, Ba2+, Cd2+, Co2+, Mg2+, Ag+, Cs+, Li+, and Na+ induced no or much smaller color/spectral changes, which constituted a Hg2+-selective fluorescent chemosensor (OFF-ON).     

A bifunctional rhodamine derivative as chemosensor for recognizing Cu~(2+) and Hg~(2+) ions via different spectra

A new simple bifunctional chemosensor 1 based on rhodamine was synthesized by hydrazide and formylformic acid,which could detect Cu~(2+) and Hg~(2+) via dif ferent detecting methods in CH3 CN-HEPES buffer solution(20 mmol/L,pH 7.4)(1:9,v/v) respectively.When sensor 1 bound with Cu~(2+),it showed a colorimetric change,while a selective enhancement in fluorescence occurred upon 1 binding with Hg~(2+),resulting from the spirolatam-ring opening process.The binding modes of 1 with Cu~(2+) and Hg~(2+) were investigated based on UV,fluorescence change,ESI-Mass and Job's Plot data.Moreover,sensor 1 could selectively detect target ion in a mixed solution of Cu~(2+) and Hg~(2+),and the two metal ions do not inte rfere with each other in the process of detecting Cu~(2+) or Hg~(2+) with 1.