Reversible "off-on" fluorescent chemosensor for Hg2+ based on rhodamine derivative

A novel and simple fluorescent chemosensor based on rhodamine was designed and synthesized to detect Hg(2+) with high selectivity. The structure of chemosensor 1 was characterized by IR, (1)H NMR, and HRMS spectroscopies. Chemosensor 1 exhibited distinct fluorescent and colorimetric changes toward Hg(2+) in an ethanol/water (80/20, v/v) solution, which resulted in the formation of 1/Hg(2+) complex with the Hg(2+)-induced ring opening of the spirolactam ring in rhodamine. The reversibility of chemosensor 1 was verified through its spectral response toward Hg(2+) ions and TBAI (tetrabutylammonium iodide) titration experiments.     

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.     

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.     

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.     

Ratiometric fluorescent chemosensor for Hg(2+) based on heptamethine cyanine containing a thymine moiety

Based on a T-Hg(2+)-T binding mode, a sensitive ratiometric fluorescent chemosensor for aqueous Hg(2+) was developed with a heptamethine cyanine chromophore containing a thymine moiety.     

Highly sensitive and selective turn-on fluorescent and chromogenic probe for Cu2+ and ClO- based on a N-picolinyl rhodamine B-hydrazide derivative

A new rhodamine B-based dual-function chromo- and fluorogenic probe for Cu(2+) and ClO(-) has been designed, synthesized, and characterized. The probe comprises a spectroscopic unit of rhodamine B and a Cu(2+)-specific chelating unit of pyridinecarboxamide as well as a ClO(-)-specific reactive moiety of diacylhydrazine, and is a highly selective and extremely sensitive fluorescent and colorimetric sensor for Cu(2+) and ClO(-) in different pH conditions. Compared with the reported probes for Cu(2+) or ClO(-), this is the first chemosensor based on a small molecule that can detect both Cu(2+) and ClO(-), respectively, at 1 nM level.     

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.     

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.     

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.     

Ratiometric detection of Hg2+ ions: an allosterically synchronized Hg2+/Li+ switch based on thiacalix[4]crown

A new heteroditopic chemosensor based on the 1,3-alternate conformation of thiacalix[4]crown shows a ratiometric fluorescence response towards Hg(2+) ions. Further, a negative allosteric behaviour between Hg(2+)/Li(+) ions is observed. Thus, metal ion exchange triggers a Hg(2+)/Li(+) switchable fluorescent chemosensor.     

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.     

Hg2+ selective fluorescent and colorimetric sensor: its crystal structure and application to bioimaging

A Hg(2+)-selective rhodamine 6G derivative bearing thiolactone moiety was synthesized, and its crystal structure with Hg(2+) is presented to explain the binding mode. In addition, highly selective "off-on"-type fluorescent change upon the addition of Hg(2+) was also applied to bioimaging.     

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.     

Oxidative cyclization of thiosemicarbazone: an optical and turn-on fluorescent chemodosimeter for Cu(II)

A weakly fluorescent thiosemicabazone (L(1)H) was found to be a selective optical and "turn-on" fluorescent chemodosimeter for Cu(2+) ion in aqueous medium. A significant fluorescence enhancement along with change in color was only observed for Cu(2+) ion; among the other tested metal ions (viz. Na(+), K(+), Mg(2+), Ca(2+), Cr(3+), Zn(2+), Cd(2+), Hg(2+), Pb(2+), Ag(+), Ni(2+), Co(2+), Fe(3+) and Mn(2+)). The Cu(2+) selectivity resulted from an oxidative cyclization of the weak fluorescent L(1)H into highly fluorescent rigid 4,5-dihydro-5,5-dimethyl-4-(naphthalen-5-yl)-1,2,4-triazole-3-thione (L(2)). The signaling mechanism has been confirmed by independent synthesis with detail characterization of L(2).     

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.     

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.     

Rhodamine hydrazone derivatives as Hg2+ selective fluorescent and colorimetric chemosensors and their applications to bioimaging and microfluidic system

In this paper, we report new rhodamine hydrazone derivatives bearing thiol and carboxylic acid groups as selective fluorescent and colorimetric chemosensors for Hg(2+). The ring-opening process of spirolactam enables the large fluorescent enhancement and colorimetric change upon the addition of Hg(2+). The sample containing Hg(2+) was mixed with one of the chemosensors in a microchannel where the sensor was examined using confocal laser scanning microscopy. A plot of the fluorescent intensities of both chemosensors versus the log concentration of Hg(2+) exhibited a linear response (r(2)=0.95) in the range of 1 nM-1 μM, and the detection limits were 1 nM and 4.2 nM, respectively. Both chemosensors also enable the visualization of Hg(2+) accumulated in the nematode Caenorhabditis elegans previously exposed to nanomolar concentrations of Hg(2+).     

A rhodamine-cyclen conjugate as a highly sensitive and selective fluorescent chemosensor for Hg(II)

A rhodamine-cyclen conjugate (1) behaves as a highly sensitive and selective fluorescent chemosensor for Hg(2+). The high emission selectivity is due to the formation of 1-Hg(2+) 1:2 complex leading to spirocycle opening of 1.     

Development of a reversible fluorescent gold sensor with high selectivity

We have designed and synthesized the highly selective and reversible fluorescent chemosensor 1 for Au(3+) by modifications on the fluorescent copper chemodosimeter 2, and we have further demonstrated that chemosensor 1 could be employed to image Au(3+) in living cells.     

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.