Gandhi Sivaraman

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.

Phenothiazine based sensor for naked-eye detection and bioimaging of Hg(II) and F− ions

The design and development of new phenothiazine-based fluorescent probes, which display a selective fluorescence response to mercury and fluoride ions, were described. The probe is the first example that facilitates the detection of Hg2+ at nanomolar concentrations. The sensitivity of probe P-1 to Hg2+ and F− was demonstrated in living cells, and cell toxicity assays revealed that probe P-1 can be used for selective imaging of Hg2+ and F− in living cells. Moreover, the simple probe design presented here may contribute to the development of more efficient and more useful dual-mode probes.

A rhodamine based “turn-on” fluorescent probe for Pb(II) and live cell imaging

A novel “turn-on” fluorescent chemosensor RDP-1 based on a rhodamine tri methoxy benzaldehyde conjugate was synthesized, which showed high selectivity and sensitivity towards recognition of Pb2+ in aqueous media over other metal ions and also color changes from colorless to pink, allowing colorimetric detection of Pb2+ by the naked eye. The sensitivity of probe RDP-1 towards Pb2+ was demonstrated in living cells, and can be used for selective imaging of Pb2+ in living cells.

Silver@graphene oxide nanocomposite-based optical sensor platform for biomolecules

In this report, a silver@graphene oxide (Ag@GO) nanocomposite-based optical sensor was developed for the detection of biomolecules such as dopamine (DA), ascorbic acid (AA), and uric acid (UA). An aqueous solution of Ag@GO was prepared using a simple chemical reduction method, and it showed a characteristic surface plasmon resonance (SPR) band at 402 nm. The SPR features of the Ag@GO nanocomposite were used for the detection of DA, AA, and UA. The SPR intensity-based limits of detection (LODs) of DA, AA, and UA were 49 nM, 634 nM, and 927 nM, respectively. The SPR band position-based LODs of DA, AA, and UA were 30 nM, 1.64 μM, and 2.15 μM, respectively. The present optical sensor was more sensitive to DA than to UA and AA. The interactions of the biomolecules with Ag@GO were studied based on density functional theory (DFT), and it was found that DA had more interaction than AA and UA. This novel Ag@GO nanocomposite is simple to prepare and showed excellent stability and sensitivity toward the detection of biomolecules.