Newly synthesized rhodamine derivatives, L(1) and L(2), are found to bind specifically to Hg(2+) or Cr(3+) 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 L(1), the detection limit is even lower than the permissible [Cr(3+)] or [Hg(2+)] in drinking water as per standard U.S. EPA norms; while the receptor, L2 could be used as a ratiometric sensor for detection of Cr(3+) and Hg(2+) based on the resonance energy transfer (RET) process involving the donor naphthalimide and the acceptor Cr(3+)/Hg(2+)-bound xanthene fragment. Studies reveal that these two reagents could be used for recognition and sensing of Hg(2+)/Cr(3+). Further, confocal laser microscopic studies confirmed that the reagent L(2) could also be used as an imaging probe for detection of uptake of these ions in A431 cells.

Specific recognition of CN(-) in sodium cyanide solution was achieved using two imidazole-based receptors (A and B). Visually detectable color changes were associated with the formation of hydrogen bonded adducts, A.CN(-) and B.CN(-). Ratiometric fluorescence response was achieved for receptor A on binding to CN(-), and this reagent was used for imaging bacterial cells pre-exposed to 1.42 microM CN(-) solution.

Adverse influences of mercury on living organisms are well known. Despite efforts from various regulatory agencies, the build-up of Hg2+ concentration in the environment is of serious concern. This necessitates the search for new and efficient reagents for recognition and detection of Hg2+ in environmental samples.

Effective extraction of Hg(2+) and Cr(3+) ions from aqueous media by novel rhodamine-alginate polymer-based highly fluorogenic, as well as colorimetric, chemosensor beads.