A probe based on 2-(2'-hydroxyphenyl) benzothiazole (HBT) has been synthesized and used for the ratiometric detection of hydrazine. The probe is designed in such a way that the excited state intramolecular proton transfer (ESIPT) of the HBT moiety gets blocked. The chemodosimetric approach of hydrazine to the probe results in the recovery of the ESIPT by removal of a free HBT moiety through subsequent substitution, cyclization, and elimination processes. The probe is successfully demonstrated to enable the detection of hydrazine in live cells.

A spirobenzopyran-quinoline (SBPQ) based sensor was synthesized which selectively detects trivalent ions viz. Al(3+), Fe(3+) and Cr(3+) through a fluorescence turn on signal in the red region (~675 nm) with the detection limit in the order of 10(-8) M. The potentiality of the probe was confirmed by employing it for fluorescence bio-imaging with Al(3+) in three different types of live-cells.

A new naphthalimide-quinoline based probe (NAQ) is designed and synthesized and its structure is confirmed through single crystal analysis. It detects the trivalent ions (Fe 3+ or Al 3+ or Cr 3+ ) selectively among other alkali and transition metal ions studied. NAQ shows a distinct ratiometric fluorescence behavior upon addition of trivalent metal ions in CH 3 v/v, pH = 7.4). This fluorogenic sensing of NAQ to M 3+ (M 3+ = Fe 3+ or Al 3+ or Cr 3+ ) can be observed by the naked eye, when illuminated under the UV light.

On the basis of the Förster resonance energy transfer mechanism between rhodamine and quinoline-benzothiazole conjugated dyad, a new colorimetric as well as fluorescence ratiometric probe was synthesized for the selective detection of Cd(2+). The complex formation of the probe with Cd(2+) was confirmed through Cd(2+)-bound single-crystal structure. Capability of the probe as imaging agent to detect the cellular uptake of Cd(2+) was demonstrated here using living RAW cells.