Ratiometric Detection
of Cr<sup>3+</sup> and Hg<sup>2+</sup> by a Naphthalimide-Rhodamine
Based Fluorescent Probe
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Abstract
Newly synthesized rhodamine derivatives, <b>L</b><sub><b>1</b></sub> and <b>L</b><sub><b>2</b></sub>, are found
to bind specifically to Hg<sup>2+</sup> or Cr<sup>3+</sup> in presence
of large excess of other competing ions with associated changes in
their optical and fluorescence spectral behavior. These spectral changes
are significant enough in the visible region of the spectrum and thus,
allow the visual detection. For <b>L</b><sub><b>1</b></sub>, the detection limit is even lower than the permissible [Cr<sup>3+</sup>] or [Hg<sup>2+</sup>] in drinking water as per standard
U.S. EPA norms; while the receptor, <b>L2</b> could be used
as a ratiometric sensor for detection of Cr<sup>3+</sup> and Hg<sup>2+</sup> based on the resonance energy transfer (RET) process involving
the donor naphthalimide and the acceptor Cr<sup>3+</sup>/Hg<sup>2+</sup>-bound xanthene fragment. Studies reveal that these two reagents
could be used for recognition and sensing of Hg<sup>2+</sup>/Cr<sup>3+</sup>. Further, confocal laser microscopic studies confirmed that
the reagent <b>L</b><sub><b>2</b></sub> could also be
used as an imaging probe for detection of uptake of these ions in
A431 cells