A novel rhodamine-based receptor bearing a morpholine (RDM) was developed as a fluorescent chemosensor with high selectivity toward Hg2+. After the addition of Hg2+ to RDM, the color of the solution changed from colorless to pink, and the new absorption band appears
at 580 nm. The fluorescent of RDM appears to orange color in the presence of Hg2+. Upon the addition of Hg2+, ring-opening of the corresponding spirolactam gives rise to fluorescence, and a 1:1 metal-ligand complex formed.
The rhodamine based receptors were developed as colorimetric and fluorescent chemosensor towards Cu 2+ . By using UV-Vis and fluorescence spectroscopy techniques, their selectivity and photophysical properties towards various metal ions were determined. The obvious color change from colorless to pink (under normal light) and non-fluorescent to yellowish-green fluorescent (under UV light) were observed upon the copper addition. The metal binding structures were proposed based on analysis data of proton NMR and Job's plot. Cell imaging experiments were conducted to determine if the chemosensors could be used in biological systems. The results showed that cell viability did not decrease below 80% at any concentrations. Chemosensors and Cu 2+ were added to the cells for cell imaging and fluorescence images. Overall, it was found that the chemosensors were cell-permeable, non-toxic, and functional in the cells.
Over the past two decades, fluorescent chemosensors have emerged as important alternatives to traditional qualitative and quantitative analysis technologies. Such sensors have been designed and synthesized for various uses, including biological, environmental, medical, and electromagnetic applications.
1-12Fluorescent sensors are highly sensitive, easy to use, and have wide applicability. In addition, such sensors can be used for analyzing metal ions quickly and accurately via the formation of a complex between the fluorophore and the metal ion being detected.
13The fluorophore anthracene and its derivatives have been used widely for fluorescence sensing, including the detection of metal ions, simple inorganic anions, and small organic molecules as well as for pH measurements. [14][15][16][17] These materials also exhibit very interesting photophysical properties: both chelation-enhanced fluorescence (CHEF) and chelation-enhanced fluorescence quenching (CHEQ) have been observed during complex formation. [18][19][20][21][22] We had previously reported that 9, 10-bis(3-hydroxypropylamino-methyl)anthracene exhibits significant OFF-ON-type fluorescence responses after interacting with Fe 3+
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