Duraisamy Chellappa

Rhodamine based sensor for naked-eye detection and live cell imaging of fluoride ions

A rhodamine based highly selective colorimetric and fluorescent probe for fluoride has been designed and synthesized. The fluorescent change is attributed to the fluoride triggered spirolactam ring opening which is augmented by density functional theory calculations and 1H NMR titrations. The sensor has been shown to be feasible for real sample analysis, and imaging of fluoride ions in the HeLa cells.

Rhodamine based selective turn-on sensing of picric acid

A rhodamine based derivative RDD-1 bearing dimethylaminobenzaldehyde has been designed and synthesized. It is a highly sensitive and selective chemosensor towards picric acid without having any interference from other NACs. To the best of our knowledge, the present probe is the first example of a rhodamine based sensor that facilitates the detection of powerful explosive picric acid even at picomolar concentration.

Development of a pyrene based “turn on” fluorescent chemosensor for Hg2+

We have designed, synthesized, and evaluated a new pyrene-based “turn on” fluorescent chemosensor which showed remarkable enhanced fluorescence intensity in the presence of Hg2+ ions and a high selectivity towards Hg2+ ions over a wide range of metal ions in aqueous acetonitrile (ACN). The probe shows selectivity and sensitivity with a 12-fold enhancement in fluorescence towards Hg2+. Upon the addition of Hg2+ ions, the probe displayed an apparent color change, which could be observed by the naked eye under a UV lamp. Its in vitro sensitivity to Hg2+ was demonstrated in candida albicans cells with the use of confocal microscopy.

Aminoquinoline based highly sensitive fluorescent sensor for lead(II) and aluminum(III) and its application in live cell imaging.

We have synthesized a new probe 5-((anthracen-9-ylmethylene) amino)quinolin-10-ol (ANQ) based on anthracene platform. The probe was tested for its sensing behavior toward heavy metal ions Hg(2+), Pb(2+), light metal Al(3+) ion, alkali, alkaline earth, and transition metal ions by UV-visible and fluorescent techniques in ACN/H2O mixture buffered with HEPES (pH 7.4). It shows high selectivity toward sensing Pb(2+)/Al(3+) metal ions. Importantly, 10-fold and 5- fold fluorescence enhancement at 429 nm was observed for probe upon complexation with Pb(2+) and Al(3+) ions, respectively. This fluorescence enhancement is attributable to the prevention of photoinduced electron transfer. The photonic studies indicate that the probe can be adopted as a sensitive fluorescent chemosensor for Pb(2+) and Al(3+) ions.

Aminobenzohydrazide based colorimetric and ‘turn-on’ fluorescence chemosensor for selective recognition of fluoride

Chemosensors based on aminobenzohydrazide Schiff bases bearing pyrene/anthracene as fluorophores have been designed and synthesized for F(-) ion recognition. The addition of fluoride ions to the receptors causes a dramatically observable colour change from pale yellow to brown/red. (1)H NMR studies confirm that the F(-) ion facilitates its recognition by forming hydrogen bond with hydrogens of amide and amine groups. Moreover these sensors have also been successfully applied to detection of fluoride ion in commercial tooth paste solution.

Pyrene based selective–ratiometric fluorescent sensing of zinc and pyrophosphate ions

A simple pyrene-based receptor has been synthesized. It shows a colorimetric and ratiometric fluorescent detection of zinc in aqueous solution. The ratiometric fluorescent change has been accounted to the conformational change of the probe. The ratiometric fluorescence change has been further supported by DFT/TDDFT calculations. The PDP-1 + Zn2+ complex is also further successfully utilized for ratiometric fluorescence detection of pyrophosphate anions in buffered aqueous solution. The applicability of these probes for real sample analysis for the detection of Zn(II) and pyrophosphate ions has been also studied.

Quick accessible dual mode turn-on red fluorescent chemosensor for Cu(II) and its applicability in live cell imaging

A novel fluorescent chemosensor 9,10-Diphenyl-7H-benzo[d,e]imidazo[2,1-a]isoquinolin-7-one (BIDQ-1), which exhibits rapid colorimetric and fluorimetric response for copper ions over other competitive metal ions under mild conditions has been synthesized easily by a simple one pot condensation method. On addition of Cu(II), BIDQ-1 shows a distinct color change from yellow to green, thus permitting the probe to be used for naked eye detection of Cu(II). The new fluorescent probe exhibits a turn-on fluorescence response towards Cu2+ under physiological conditions with high sensitivity and selectivity. The turn-on fluorescence behaviour of BIDQ-1 with Cu(II) was found to be via an intramolecular charge transfer (ICT) mechanism, by TD-DFT calculations. The probe was found to be applicable for imaging intracellular Cu2+ in living cells.

Triazole based ratiometric fluorescent probe for Zn2+ and its application in bioimaging

An efficient fluorescent chemosensor 4-((2-hydroxynaphthalen-1-yl)methyleneamino)-3-phenyl-1H-1,2,4-triazole-5(4H)-thione, based on triazole has been designed by condensing 2-hydroxy-1-napthaldehyde with amine, appended to 1,2,4-triazole unit. The probe displays excellent selectivity and sensitivity in both absorbance and fluorescence detection of Zn2+ over other essential metal ions. The nature of fluorescence behavior of receptor upon addition of Zn2+ has been obtained from Density Functional Theory calculations. Imaging experiment indicates that probe works effectively for intracellular Zn2+ imaging with good cell permeability and biocompatibility.

A ratiometric fluorescent sensor for selective recognition of Al3+ ions based on a simple benzimidazole platform

An efficient new ratiometric chemosensor, 6-imidazo-2-yl-5,6-dihydro-benzo[4,5]imidazo[1,2-c]quinazoline (PB), which enables selective sensing of Al3+ in aqueous DMSO was synthesized by a facile one step condensation reaction of imidazole-2-carboxaldehyde with 2-(2-aminophenyl)-1H-benzimidazole. The probe PB was characterized by elemental analysis, 1H and 13C NMR, ESI-MS and IR spectral techniques. Upon addition of Al3+, the fluorescent probe PB induces ratiometric responses in both absorption and fluorescence spectra on the basis of a charge transfer mechanism. The receptor PB serves for highly selective, sensitive and ratiometric detection of Al3+ without the interference of biologically and environmentally relevant cations. The detection limit is found to be 5.3 × 10−7 M. The Jobs plot analysis indicates the binding stoichiometry of the complex to be 1 : 1 (host/guest).

Vitamin B6 cofactor based fluorescent probe for sensing an anion (F−) and cation (Co2+) independently in a pure aqueous medium

A new highly selective and sensitive bifunctional fluorescent probe for Co2+ and F− ions has been derived from a vitamin B6 cofactor and the response mechanism has been analyzed using DFT calculations. The probe features a facile synthetic protocol, good water solubility, high selectivity and sensitivity, a fluorescence turn-on response to F−, and a ratiometric response towards Co2+ in an aqueous medium.